ENCYCLOPEDIA OF ENVIRONMENTAL SCIENCE AND ENGINEERING - PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS potx

972
PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
INTRODUCTION
The substances in domestic and industrial wastewater having
significance in water-pollution control, disposal, and reuse
are (1) dissolved decomposable organic substances result-
ing in dissolved oxygen depletion in streams and estuaries
and/or causing taste and odor; (2) suspended organic solids
resulting in dissolved oxygen depletion; (3) inert suspended
solids (SS) causing turbidity and resulting in bottom sedi-
ment deposits; (4) toxic synthetic organic substances and
heavy metals; (5) oil, grease, and floating materials; (6) acids
and alkalis; and (7) dissolved salts, including nutrients like
phosphorus and nitrogen.
Conventional wastewater-treatment practices have been
oriented to the removal of grit and floating matter followed
by the removal of suspended and dissolved organic matter.
The removal of suspended matter has been achieved by
sedimentation, and the bulk of the soluble organic matter
is removed by biological oxidation and flocculation.
These processes, when carried out in combination, have
proved to be economical and effective means for remov-
ing organic matter from wastewaters. However, there are
certain disadvantages associated with them. These include
the following:
1. Biological process require considerable operating
control and often generate operating problems of
a complex nature.
2. Biological processes are easily upset by shock loads
and require time to regain efficient operation.
3. Biological processes are unable to remove certain

nutrients, heavy metals, and inorganic salts, when-
ever there is a requirement for their removal.
4. Many waste streams contain certain compounds
that do not respond to biological treatment or,
alternatively, require extensive pretreatment.
In the last decades, physical-chemical treatment of waste-
water has been studied both on laboratory and pilot-plant
scales with important industrial and municipal wastewater-
treatment applications. This type of treatment is used either as
a pretreatment, tertiary treatment, or advanced treatment given
to the effluent from secondary treatment, or as a substitute for
conventional biological treatment. In the latter case, it is found
to produce effluent of a quality at least equal to that produced
by conventional biological treatment.
The first study on the treatability of raw wastewater
by physical-chemical processes was reported by Rudolfs
and Trubnick in 1935. In this study, solids were removed
by chemical coagulation with ferric chloride followed by
absorption of dissolved impurities with activated carbon.
Stander and Van Vuuren (1969) investigated the treat-
ment of raw wastewater in a pilot plant where solids removal
was achieved by primary sedimentation and chemical coagu-
lation with lime, and adsorption with activated carbon. Rizzo
and Schade (1969) have also reported results on the pilot-
plant treatment of raw wastewater with chemical coagulation
and anionic polymer and adsorption with activated carbon.
Zuckerman and Molof (1970) studied the efficiency of a
treatment system in which raw wastewater was lime-clarified
at high pH and then activated-carbon-treated: their results
showed that the chemical oxygen demand (COD) values of

the final effluent were significantly lower than those associ-
ated with good conventional treatment. Moreover, they con-
cluded that the removal of soluble organics with activated
carbon was enhanced because of the hydrolytic breakdown
of high-molecular-weight organic compounds, at a higher
pH value, which are absorbed more readily by activated
carbon.
Weber et al. (1970) investigated the chemical clarifi-
cation of primary effluent with ferric chloride followed
by activated-carbon adsorption. Their results showed that
65% of the organic matter present in primary effluent
was removed by chemical treatment with ferric chloride.
Overall removal of biochemical oxygen demand (BOD)
was reported as being consistently in the range of 95 to
97%. Final effluent from the system contained approxi-
mately 5 mg/l BOD as compared to 30 mg/l for the same
wastewater treated conventionally.
In another study, Villiers et al. (1971) showed that the
treatment of primary effluent by lime clarification and acti-
vated carbon, in a steady flow system, produced an efflu-
ent with total organic carbon (TOC) averaging 11 mg/l and
turbidity averaging less than 2. Phosphates and SS removal
were consistently 90% or better. These product characteris-
tics are comparable to those associated with products from
well-operated conventional treatment plants.
Shuckrow (1971) had developed a sewage-treatment
process involving chemical coagulation for SS removal, fol-
lowed by adsorption of soluble organics on powdered carbon.
The advantages cited for this process were (1) a total treat-
ment time of less than one hour, (2) a high-quality effluent,

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PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 973
(3) lower initial plant cost, (4) ability to remove nitrogen and
phosphorus, and (5) a final sludge reduction to sterile ash in
a centrifuge-incineration process combined with a chemical
regeneration step to recover both the coagulant and the carbon.
While the estimated operational costs were high, the overall
costs during a 20-year plant life were considered to be signifi-
cantly less than costs for comparable biological facilities.
Ecodyne Corporation’s first complete physical-chemical
treatment plant in Rosemount, Minnesota, with 0.04 to
0.08 m
3
/sec peak capacity, consisted of bar screening, phos-
phate removal with sludge recirculation, dual media filtration,
carbon absorption to remove dissolved organics, secondary
filtration, and ammonia removal by ion exchange with zeo-
lite. The plant included facilities for regenerating the carbon,
recovering ammonia, and regenerating brine from the ion-
exchange system (Ecodyne, 1972).
Examples of more recent research include an exhaustive
review on the treatment of pulp- and paper-mill wastewa-
ter published by Pokhrel and Viraraghavan in 2004. This
includes the different processes involved with their effluents,
the different methods for treatment of these effluents, the
integration of biological and physico-chemical processes,
a comparison of them, and conclusions from this review.
An article by Van Hulle and Vanrolleghem (2004) presents
the development, calibration, and application of a model for

the simulation and optimization of a wastewater-treatment
plant. The constructed model proved to be able to predict
large variations in influent composition. This could be an
important tool for production scheduling when applied to
industrial wastewater-treatment plants. Recent research in
specific areas is included in for each process.
The number of water-treatment facilities in the United
States by treatment capacities is presented in Table 1. Many
of these facilities include some sort of physical-chemical
treatment technology. A diagram of alternative technologies
for wastewater treatment is shown in Figure 1; it includes
most of the processes to be discussed in the next section. As
environmental regulations, space availability, and cost fac-
tors affect the treatment of waste streams, more and more
physical-chemical treatment will be needed to meet these
constraints. This is an important research area that will con-
tinue to grow in the next years.
PHYSICAL AND CHEMICAL PROCESSES USED IN
WASTEWATER TREATMENT
The following important unit operations and unit processes
involved in the physical and chemical treatment of wastewater
are discussed in detail:
Flow equalization and neutralization
Chemical coagulation, flocculation, and sedimentation
Filtration
Gas stripping
Ion exchange
Adsorption
Flotation
Chemical processes

Oxidative, photochemical, and electron-beam processes
Flow Equalization and Neutralization
Both domestic and industrial wastewater flows show con-
siderable diurnal variation, and it is considered necessary
to significantly dampen these variations in inflow to relieve
hydraulic overload on both biological and physical-chemical
plants. This process will also smooth out variations in influent
characteristics.
Flow-equalization basins are basically flow-through or
side-line holding tanks, and their capacity is determined by
plotting inflow and outflow mass curves. These tanks are
generally located after preliminary treatment and should be
designed as completely mixed basins, using either diffused
air or mechanical surface aerators, to prevent settling of sus-
pended impurities. If decomposable organic matter is present
in the wastewater, aeration will prevent septicity. The pre-
aeration can also reduce the BOD on subsequent treatment
units.
Flow-equalization basins can also be used to neutral-
ize the acidity or alkalinity in incoming wastewater. The
neutralizing chemicals are added to the inflow wastewater
stream before entering the flow-equalization basins, and the
retention period in these basins provides sufficient time for
reaction. Any precipitates produced during neutralization are
separated in subsequent sedimentation basins.
Chemical Coagulation, Flocculation, and
Sedimentation
The use of chemical treatment appeared early in the devel-
opment of sewage- and wastewater-treatment technology.
Aluminum sulfate, lime, and ferrous sulfate, when used in

the manner usually adopted for water clarification, were
successful in producing an effluent of quality better than
that obtained by plain sedimentation. An effluent that is
generally fairly clear, with only very fine suspended or col-
loidal solids but with practically all of the dissolved solids
remaining, can be produced. Under most favorable condi-
tions and with skilled operation, SS may be reduced in an
amount of up to 90% and BOD up to 85%. However, the
TABLE 1
Number of wastewater-treatment facilities in the United States (1996)
Flow ranges m
3
/s Number of facilities Total existing flowrate m
3
/s
0–0.00438 6444 12.57
0.0044–0.0438 6476 101.78
0.044–0.438 2573 340.87
0.44–4.38 446 511.12
4.38 47 443.34
Other 38 —
Total 16204 1409.68
Source: Adapted from Tchobanoglous et al., 2003.
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974 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
cost of the coagulants and the difficulty of disposing of the
larger amount of the sludge produced by this process caused
it to be abandoned. The revival of chemical treatment can be
attributed to a number of factors that accumulated as a result

of continuous investigations and reevaluation of the process.
These are (1) the decrease in cost of chemicals; (2) better
understanding of floc formation and the factors affecting
it; (3) the development of methods of sludge filtration and
processing that overcome, in part, the difficulty of greater
sludge bulk; and (4) the establishment of the relationship
between eutrophication in streams and nutrients, particularly
phosphorus, nitrogen oxides, and organic matter. This rela-
tion establishes the need of final effluent wastes free of such
pollutants regardless of the cost of additional treatment.
The settling velocities of finely divided and colloidal
particles in wastewaters are so small that removing them
in a settling tank under ordinary conditions is impossible
unless very long detention periods are provided. Therefore,
it has been necessary to devise means to coagulate these
very small particles into larger ones that will have higher
settling velocities. The aggregation of dispersed particles in
wastewater is induced by addition of chemical coagulants to
decrease the effects of stabilizing factors such as hydration
and zeta potential, and by agitation of the medium to encour-
age collisions between particles.
Because of the greater amount of suspended matter in
sewage, the doses for chemical coagulants are generally con-
siderably greater. Therefore, in order to keep costs down, it
is important that the chemical reaction involved with each
coagulant should be known and enhanced and that optimum
pH values be obtained by adjustment with acid or base to get
more efficient coagulation and clarification with least sludge
production.
Coagulation Coagulation is a process in which chemicals

are added to an aqueous system for the purpose of creat-
ing rapid-settling aggregates out of finely divided, dispersed
matter with slow or negligible setting velocities. The poten-
tial applications of this process in treating wastewater are:
(1) direct coagulation of organic matter present mostly as
colloidal particles in wastewater; (2) the removal of colloi-
dal substances prior to such tertiary treatment processes as
ion exchange, carbon adsorption, and sand filtration; (3) the
removal of colloidal precipitates formed in phosphate pre-
cipitation processes; and (4) the removal of dispersed micro-
organisms after a brief biooxidation process.
The majority of colloids in domestic wastewater or in
organic wastes are of a hydrophilic nature; that is, they have
an affinity for water. The affinity of hydrophilic particles for
water results from the presence of certain polar groups such
as −COOH and −NH
2
on the surface of the particles. These
groups are water-soluble and, as such, attract and hold a sheath
of water firmly around the particle. The primary charge on
hydrophilic colloidal particles may arise from ionization of the
chemical groups present at the surface of the particles, e.g., car-
boxyl, amino, sulfate, and hydroxyl. This charge is dependent
upon the extent to which these surface groups ionize, and thus
the particle charge depends upon the pH.
Equalization
Raw
wastewater
Spill pond
Filtration

Precipi-
tation
Oxidation/
reduction
Heavy
metals
Process
wastewaters
Organic
chemicals
Organics,
ammonia
In-plant treatment
Centrifugation
Drying
Sludge disposal
Incineration
Lagooning
Land disposal
Sludge digestion
Filtration
Gravity
thickening
Dissolved-air
flotation
Sludge
dewatering
Air or
steam
stripping

To discharge or POTW
GAC
adsorption
Oxi-
dation
Neutralization
Coagulation
Filtration
Anaerobic
treatment
Activated
sludge
Ozonation
PAC coagulant
PACT
Nitrification/
denitrification
RBC
Aerated lagoon
Trickling
filter
To publicly owned
treatment works (POTW)
Primary treatment
Acid or
alkali
Chemicals
Flotation
Sedi-
mentation

Filtration
GAC
adsorption
Discharge to
receiving water
Secondary
treatment
Tertiary treatment
Biological
roughing
Wastewater
Return flows
Sludge
GAC and PAC: granular and powdered activated carbon
RBC: rotating biological contractor
FIGURE 1 Alternative technologies for wastewater treatment (From Eckenfelder, 2000. Reprinted with
permission from McGraw-Hill.)
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PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 975
The precise zeta potential that yields optimum coagu-
lation must be determined for a given wastewater by actual
correlation with jar test or plant performance. The control
point has been reported to be in the range of 0 to −10 mV
when raw sewage is coagulated by alum. It is important that
coagulants contribute polyvalent ions of charge opposite to
the zeta potential of the dispersion. On a molar basis, biva-
lent ions seem to be about 10 to 50 times and trivalent ions
about 300 to 700 times as effective as monovalent ions for
destabilization of dispersion in wastewater (Rich, 1963). The

zeta potential is unaffected by pH in the range of 5.5 to 9.5
(Eckenfelder, 2000).
Since most dispersions encountered in wastewaters
are stabilized by negative charges, coagulants required are
polyvalent cations such as aluminum, ferric, ferrous, or cal-
cium. Organic polyelectrolytes are also effective coagulants.
Dispersions stabilized principally by electrostatic force are
in general amenable to coagulation inasmuch as addition of
small doses of suitable electrolytes may effect a significant
change in zeta potential of the particles. The most widely
used chemicals for coagulation of wastewater are the salts
of aluminum and iron. Lime alone has also been used for
precipitation of phosphates.
Aluminum Sulfate In order to form flocs, aluminum sulfate
requires the presence of alkalinity, which, if naturally present
in wastewater in the form of bicarbonate, would lead to the
following reaction:
Al
2
(SO
4
)
3
.xH
2
O  3Ca(HCO
3
)
2
→

2Al(OH)
3
↓  3CaSO
4
 xH
2
O  6CO
2
(1)
In case of insufficient alkalinity in the wastewater, lime is
generally added, and the reaction with alum becomes:
Al
2
(SO
4
)
3
.xH
2
O  3Ca(OH)
2
→
2Al(OH)
3
↓  3CaSO
4
 xH
2
O (2)
In the presence of phosphate, the following reaction also

occurs:
Al
2
(SO
4
)
3
.xH
2
O  2PO
4
-2
→
2AlPO
4
↓  3SO
4
-2
 xH
2
O (3)
Aluminum hydroxide flocs are least soluble at a pH of
approximately 7.0. The floc charge is positive below pH 7.6
and negative above pH 8.2 (Eckenfelder, 1966). The solubil-
ity of AlPO
4
is related to the pH and the equilibrium con-
stant for the salt. Stumm and Morgan (1970) state that the
solubility of aluminum phosphate is pH-dependent, and the
optimum pH for phosphorus removal lies in the range of 5.5

to 6.5. Generally, at pH above 6.3, the phosphate removal
occurs either by incorporation in a complex with aluminum
or adsorption on the aluminum hydroxide flocs. According to
Yuan and Hsu (1970), the reaction mechanism for precipita-
tion of phosphates by aluminum hydroxide is very complex.
They have proposed that the positively charged hydroxy-
aluminum polymers are the species that accounts for the
precipitation of phosphates and that effective phosphate pre-
cipitation can occur only when the positive charges on the
polymers are completely neutralized. It is also reported that
the effectiveness of aluminum is related to the nature and
concentration of the foreign components present and to the
ratio of phosphate to aluminum.
Alum has been used extensively for phosphate removal
in raw wastewaters. Bench-scale tests of alum addition were
conducted at Springfield, Ohio, and Two Rivers, Wisconsin
(Harriger and Hoffman, 1971 and 1970, respectively). Raw
wastewater at Springfield required an average Al:P mass ratio
of 1.9:1 to achieve 80% removal, while at Two Rivers the
average mass ratio was 0.93:1 to obtain phosphate removal
of 85%. The stoichiometric equation (3) indicates that each
kilogram of phosphorus requires 0.87 kg of aluminum for
complete precipitation.
Ferrous Sulfate and Lime If ferrous salts are used for
wastewater coagulation, addition of a small amount of base,
usually sodium hydroxide or lime, is essential. The required
dosage is related to the alkalinity of water. Ferrous sulfate
reacts with calcium bicarbonate in water, but this reaction
is much delayed and therefore cannot be relied on (Steel,
1960). Caustic alkalinity, due to the addition of lime to the

wastewater, produces a speedy reaction. The lime is added
first, and the following reaction takes place:
FeSO
4
.7H
2
O  Ca(OH)
2
→ Fe(OH)
2
 CaSO
4
 7H
2
O (4)
The ferrous hydroxide is not an efficient floc, but it can soon
be oxidized by the dissolved oxygen in wastewater as ferric
hydroxide:
4Fe(OH)
2
 O
2
 2H
2
O → 4Fe(OH)
3
↓ (5)
An insoluble hydrous ferric oxide is produced over a pH
range of 3 to 13. The floc charge is positive in the acid range
and negative in the alkaline range, with a mixed charge over

a pH range of 6.5 to 8.0. This process is usually cheaper than
the use of alum but needs greater skill to dose with the two
chemicals.
Ferric Chloride Ferric chloride has been used successfully
for wastewater coagulation because it works well in a wide
pH range (Steel, 1960; Wuhrmann, 1968). The reactions
of ferric chloride with bicarbonate alkalinity and lime are,
respectively:
2FeCl
3
 3Ca(HCO
3
)
2
→ 2Fe(OH)
3
↓  3CaCl
2

 6CO
2
(6)
2FeCl
3
 3Ca(OH)
2
→ 2Fe(OH)
3
↓  3CaCl
2

(7)
Wuhrmann (1968) was successful in removing phosphates
from sewage effluent by precipitation with a mixture of
ferric salt and lime. The ferric dosages varied between 10
and 20 mg/l and the lime dosages from 300 to 350 mg/l
in order to raise the pH to values between 8 and 8.3. The
actual lime dosage required is related to the alkalinity of
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976 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
the water. According to Wuhrmann, the dominant reaction
product between the phosphate ion and the ferric ion at pH
above 7 is believed to be FePO
4
, with a solubility product of
about 10
23
at 25°C. The colloidal particle size of the FePO
4

requires a sufficient excess of ferric ion for the formation of
a well-flocculating hydroxide precipitate, which includes the
FePO
4
particles and acts as an efficient adsorbent for other
phosphorous compounds.
It has been reported that for efficient phosphorus
removal (85 to 95%), the stoichiometric amount of 1.8 mg/l
Fe required per mg/l P should be supplemented by at least
10 mg/l of iron for hydroxide formation. Also, the use of

anionic polymer is considered desirable in order to produce
a clear supernatant (Wukash, 1968).
Lime Lime reacts with the bicarbonate alkalinity of waste-
water to form calcium carbonate, which precipitates, under
normal conditions:
Ca(OH)
2
 Ca(HCO
3
)
2
→ 2CaCO
3
↓  2H
2
O (8)
Normally, 70 to 90% of the phosphorus in domestic sewage
is in the form of orthophosphates or polyphosphates that may
hydrolyze orthophosphates. The remaining phosphorus is
present in the form of organic-bound phosphorus. The removal
of phosphorus can be achieved by direct adsorption on the
surface of calcium carbonate particles. Orthophosphates can
also be precipitated in the alkaline range by reaction with cal-
cium salts to form hydroxyapatite, according to the following
reaction:
10Ca(OH)
2
 6H
3
PO

4
→ 10Ca  (PO
4
)
6
(OH)
2
↓
 18H
2
0 (9)
Schmid and McKinney (1969) observed that hydroxyapatite
was present in soluble form at a pH value above 9.5. They
also found that at pH values of 9.5 or less, phosphorus was
adsorbed onto the growing faces of calcium-carbonate par-
ticles, thereby inhibiting their growth. Buzzell and Sawyer
(1967) have shown that at pH levels of 10 to 11 in the primary
sedimentation tanks, BOD removal of 55 to 70%, nitrogen
removal of 25%, phosphate removal of 80 to 90%, and coli-
form removal of 99% can be expected. Bishop et al. (1972)
have reported that precipitation of domestic wastewater with
lime removed approximately 80% of the TOC, BOD, and
COD; 91% of the SS; 97% of the total phosphorus; and 31%
of the total nitrogen. Phosphates from secondary effluent have
been removed successfully at Lake Tahoe by precipitation
with lime (Slechta and Culp, 1967). Albertson and Sherwood
(1967) found that by recirculating calcium-phosphate solids,
previously formed due to the addition of lime, it was possible
to reduce the lime dosage by about 50%.
Galarneau and Gehr (1997) present experimental results

of their studies on phosphorous using aluminum hydroxide.
de-Bashan and Bashan (2004) present an extensive review of
recent advances in phosphorous removal from wastewaters
and its separation for use as a fertilizer or as an ingredient in
other products.
In wastewater-treatment practices, it is detrimental to
form large floc particles immediately in the flocculation step
because it reduces the available floc surface area for adsorp-
tion of phosphorus. Therefore, it is essential to maintain fine
pinpoint flocs in order to get a maximum phosphate removal
by surface adsorption, and this can be achieved by minimizing
the time of their flocculation. This is not the case if the goal is
one of colloidal-solids removal, as is often the case in water
treatment.
The process of coagulation and flocculation in wastewater
treatment can be summarized in the following three steps:
1. As the coagulant dissolves, positive aluminum
and ferric ions become available to neutralize the
negative charges on the colloidal particles includ-
ing organic matter. These ions may also react with
constituents in solution such as hydroxides, car-
bonates, phosphates, sulfides, or organic matter to
form complex gelatinous precipitates of colloidal
dimensions that are termed “microflocs.” This is
the first stage of coagulation, and for greatest effi-
ciency a rapid and intimate mixing is necessary
before a second reaction takes place.
2. After the positively charged ions have neutralized
a large part of the colloidal particles and the zeta
potential has been reduced, the resulting flocs are

still too small to be seen or to settle by gravity. The
treatment, therefore, should be flocculation, slow
stirring so that very small flocs may agglomerate
and grow in size until they are in proper condition
for sedimentation. Some evidence suggests that
aggregation of microflocs with dispersed waste con-
stituents is the most important mechanism affecting
coagulation in water treatment (Riddick, 1961).
3. During the third phase, surface adsorption of parti-
cles takes place on the large surface area provided
by the floc particles. Some of the bacteria present
will also become entangled in the floc and carried
to the bottom of the tank.
Electrocoagulation Electrocoagulation is a process in which
the coagulating ions are produced by electrolytic oxidation of
sacrificial electrodes. This technique has been successfully
used in the removal of metals, suspended particles, colloids,
organic dyes, and oils. An interesting review of this technique
is presented by Mollah et al. (2001). In it the advantages and
disadvantages of electrocoagulation are presented as well as
a description and comparison with chemical coagulation. His
group studied its use in the treatment of a synthetic-dye solu-
tion with a removal of 99% under optimal conditions (Mollah,
Morkovsky, et al., 2004). Another publication (Mollah, Pathak,
et al., 2004) presents the fundamentals of electrocoagulation
and the outlook for the use of this process in wastewater treat-
ment. Lai and Lin (2003) studied the use of electrocoagulation
for the treatment of chemical mechanical polishing wastewater,
obtaining a 99% copper removal and 96.5% turbidity reduction
in less than 100 minutes.

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PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 977
Sedimentation Sedimentation basins are important compo-
nents in water- and wastewater-treatment systems, and their
performance greatly depends upon proper design. In chemical
treatment of wastewater, the separation of chemically coagu-
lated floc depends on the characteristics of the floc in addition
to the factors normally considered in the design of conven-
tional primary and secondary clarifiers. Field experience indi-
cates that the usual values for surface overflow rates used in
separating chemical floc in water-treatment plants must be
reduced in order to obtain a good efficiency in the removal
of floc from chemically coagulated wastewater (Weber et al.,
1970; Convery, 1968; Rose, 1968; Kalinske and Shell, 1968).
In wastewater-treatment practices, the recommended overflow
rate for removal of alum floc is 30 m/day, while with use of
lime or iron salts, it can be increased up to 40 m/day.
Filtration
Filtration of wastewater can be accomplished by the use of
(1) microscreens, (2) diatomaceous earth filters, (3) sand fil-
ters, (4) mixed media filters, or (5) membranes. The filtration
of sludges, on the other hand, is achieved by sand beds or
vacuum filters.
The filtration characteristics of the solids found in a bio-
logical treatment plant effluent are greatly different from
those of the floc formed during chemical coagulation for the
removal of organic matter and phosphates. Tchobanoglous
and Eliassen (1970) have noted that the strength of the bio-
logical floc is much greater than that of the flocs resulting

from chemical coagulation.
Accordingly, biological flocs can be removed with a
coarser filter medium at higher filtration rates than can the
weaker chemical flocs, which may shear and penetrate through
the filter more readily. Lynam et al. (1969) had observed that
the chemical floc strength can be controlled, to some degree,
with the use of polymers as coagulant aids. Their experi-
ments yielded higher SS removal by filtration when 1 mg/l of
anionic polymer A-21 was used along with alum.
The filterability of solids in a conventional biological
plant effluent is dependent upon the degree of flocculation
achieved in the biological process. For example, filtration of
the effluent from a trickling-filter plant normally cannot yield
more than 50% removal of the SS due to the poor degree of
biological flocculation in trickling filters. On the other hand,
the activated sludge process is capable of a much higher
degree of biological flocculation than the trickling-filter pro-
cess. The degree of biological flocculation achieved in an
activated sludge plant was found to be directly proportional
to the aeration time and inversely proportional to the ratio of
the amount of organic material added per day to the amount
of SS present in the aeration chamber (Culp and Hansen,
1967a). It has also been reported that up to 98% of the SS
found in the effluent from a domestic sewage-treatment plant
after a 24-hour aeration time could be removed by filtration
without the use of coagulants (Culp and Hansen, 1967b).
Microscreening Microscreens are mechanical filters
in which flow is passed through a special metallic filter
fabric placed around a drum. The filter traps the solids and
rotates with the drum to bring the fabric under backwash

water sprays fitted to the top of the machine, in order to
wash the solids to a hopper for gravity removal to disposal.
The rate of flow through the microscreen is determined
by the applied head, normally limited to about 150 mm
or less, and the concentration and nature of the SS in the
effluent.
Extensive tests at the Chicago Sanitary District showed
that microscreens with a 23 µm aperture could reduce the
SS and BOD of a good-quality activated sludge effluent,
20–35 mg/l SS and 15–20 mg/l BOD, to 6–8 mg/l and 3.5–
5 mg/l, respectively (Lynam et al., 1969). It was noted that
the microscreens were more responsive to SS loading than
to hydraulic loading and that the maximum capacity of the
microscreens was reached at the loading of 4.3 kg/m
2
/day
at 0.27 m/min.
Diatomaceous Earth Filtration Diatomite filters found their
widest application in the production of potable waters, where
the raw water supply was already of a relatively good quality,
i.e., of low turbidity. Operating characteristics of diatomite
filters can now be predicted under a wide range of operat-
ing conditions by utilizing several mathematical models
(Dillingham et al., 1966, 1967). Several investigators have
studied the filtration of secondary effluent by diatomite filters
whose ability to produce an excellent-quality effluent is well
established (Shatto, 1960; R. Eliassen and Bennett, 1967;
Baumann and Oulman, 1970). However, the extremely high
cost and their inability to tolerate significant variations in SS
concentration limit the usage of diatomite filters in sewage-

treatment practices.
Sand Filtration Sand filters have been operated as slow
sand filters or as rapid sand filters made with one or more
media. A slow sand filter consists of a 150- to 400-mm-thick
layer of 0.4-mm sand supported on a layer of a coarser mate-
rial of approximately the same thickness. The underdrainage
system under the coarser material collects the filtrate. The
rate of flow through the filter is controlled at about 3 m/day.
This rate is continued until the head loss through the bed
becomes excessive. Then the filter is thrown out of service
and allowed to partially dry, and 25 to 50 mm of the sand
layer, which includes the surface layer of sludge, is manually
scraped from the top for washing. Disadvantages of slow
sand filtration system are: (1) the filters may become inoper-
ative during the cold winter weather, unless properly housed;
(2) slow sand filters may not be effective due to the rapid
clogging of filters (the normal frequency of cleaning filters
varies from once to twice a month; Truesdale and Birkbeck,
1996); (3) the cost of slow sand filtration is three times the
cost of rapid sand filters and twice the cost of microscreens
(anonymous, 1967); and (4) the large space requirement.
Rapid sand filters consist of about a 400-mm-thick layer
of 0.5- to 0.65-mm sand supported on coarser gravel. The
rate of filtration ranges between 80 and 120 mm/min. At this
high filtration rate, the filter beds need backwashing when
the head loss becomes excessive.
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978 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
Lynam et al. (1969) reported results of detailed tests con-

ducted on filtration of secondary effluent from an activated
sludge plant of the Chicago Sanitary District. They used a
filter bed of 0.85-mm-effective-size sand in a 280-mm depth
and a filtration rate of 120 mm/min, and analyzed the data in
terms of both hydraulic and SS loadings. Poor correlations
were obtained between effluent quality and hydraulic load-
ing, effluent quality and solids loading, and solid removal
and hydraulic loading. However, an excellent correlation
existed between SS loading and SS removals. It was also
observed that the sand filtration of alum-coagulated solids
was no better than that of uncoagulated solids, and the opti-
mum SS removal was obtained by alum and polymer coagu-
lation in combination with sand filtration.
A review of the retention of pathogenic bacteria in
porous media is presented by Stevik et al. (2004). The
review includes the factor affecting bacteria retention and
the factors that effect elimination of bacteria from porous
media. The authors also suggest priority areas of research
in this field.
Multimedia Filtration The limitation of the single medium
rapid sand filter follows from its behavior as a surface filtra-
tion device. During filter backwashing, the sand is graded
hydraulically, with the finest particles rising to the top of the
bed. As a result, most of the material removed by the filter
is retained at or very near the surface of the bed. When the
secondary effluent contains relatively high solids concen-
trations, the head loss increases very rapidly, and SS clog
the surface in only a few minutes. One approach to increase
the effective filter depth is to use dual-media beds consisting
of a discrete layer of coarse coal placed above a layer of

fine sand.
More recently, the concept of mixed-media filters has
been introduced in order to achieve a filter performance that
very closely approaches an ideal one. In this case a third
layer of a very heavy and fine material, garnet (with specific
gravity of 4.2) or illmenite (with specific gravity of 4.5), is
placed beneath the coal and sand. Conley and Hsiung (1965)
have suggested the optimum design values for these filters.
The selection of media for any filtration application should
be based on the floc characteristics. An example of a typical
dual-media filter is shown in Figure 2.
Moving-Bed Filters These types of filters were put on the
market by the Johns-Manville Corporation in the late 1960s.
It is a continuous sand filter in which influent wastewater
passes through the bed and becomes product water. Solids
trapped on the filter face and within the bed move with the
filter media, countercurrent to the liquid. Solids and small
amounts of filter media regularly removed from the filter
face are educted to the filter media tower without stopping
operations. Solids are scrubbed from the media and dis-
charged as a waste sludge, while the washed media is fed
back into the bed.
The filter medium usually used is 0.6- to 0.8-mm sand
with a maximum sand-feed rate of 5 mm/min and maxi-
mum filtration rate of 85 m/day (2100 U.S. gal/day/ft
2
). The
advantages claimed for this system are (1) automatic and
continuous operation, (2) that the filter allows much higher
and variable solids loadings than is permissible with a sand

bed, and (3) that through an efficient use of coagulant chemi-
cals, the system has the flexibility to reduce turbidity, phos-
phorus, SS, and BOD to the desired level (Johns-Manville
Corporation, 1972).
Membrane Filtration Membrane filtration is being applied
more extensively as membrane materials are becoming more
resistant and affordable. Fane (1996) presents a description of
membrane technology and its possible applications in water
and wastewater treatment. An extensive study on microfiltra-
tion performance of membranes with constant flux for the
treatment of secondary effluent was published by his research
group in 2001 (Parameshwaran et al., 2001). Kentish and
Stevens (2001) present a review of technologies for the recy-
cling and reuse of valuable chemicals from wastewater, par-
ticularly from solvent-extraction processes.
A feasibility study on the use of a physico-chemical
treatment that includes nanofiltration for water reuse from
printing, dyeing, and finishing textile industries was per-
formed by Bes-Pia et al. (2003). In this work jar tests were
conducted for flocculation using commercial polymers fol-
lowed by nanofiltration. Their results show that the combina-
tion reduces COD from 700 to 100 mg/l. Another treatment
approach by the same authors (2004) uses ozonation as a
pretreatment for a biological reactor with nanofiltration as
a final step. A combined approach is presented by Wyffels
et al. (2003). In this case a membrane-assisted bioreactor
for the treatment of ammonium-rich wastewater was used,
showing this to be a reliable technology for these effluents.
Galambos et al. (2004) studied the use of nanofiltration
and reverse osmosis for the treatment of two different waste-

waters. For their particular case the use of reverse osmosis
was more convenient due to the high quality of the effluent,
but the permeate of the nanofiltration can only be released into
a sewer line or would have to be treated, resulting in an eco-
nomic compromise. A comparison between a membrane bio-
reactor and hybrid conventional wastewater-treatment systems
at the pilot-plant level is presented by Yoon et al. (2004).
The removal of volatile organic compounds (VOCs)
using a stripper-membrane system was studied by Roizard
et al. (2004). Their results show that this hybrid system can
be used for the removal of toluene or chloromethane with a
global efficiency of about 85%.
Vildiz et al. (2005) investigated the use of a coupled jet
loop reactor and a membrane for the treatment of high-
organic-matter-content wastewater. The main function of the
membrane is the filtration of the effluent and the recycle of
the biomass to the reactor. One advantage of the system is its
reduced size as compared with traditional treatment systems,
as well as a better-quality effluent.
A comprehensive review on the use of nanofiltration
membranes in water and wastewater use, fouling of these
membranes, mechanisms of separation, modeling, and the
use of atomic force microscopy for the study of surface mor-
phology is presented by Hilal et al. (2004). The future of
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PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 979
membranes and membrane reactors in green technology and
water reuse was published by Howell (2004). In it, water
problems in different regions of the world are discussed,

different membrane systems are presented, and different
approaches for new research are introduced.
Reverse Osmosis There are several reverse-osmosis units cur-
rently in use to produce freshwater from seawater. With recent
improvements in membranes, this process is also being used
for purification of wastewater. Substantial removal of BOD,
COD, total dissolved solids, phosphate, and ammonia by this
process has been reported (Robinson and Maltson, 1967).
In a reverse-osmosis process, wastewater containing dis-
solved materials is placed in contact with a suitable semi-
permeable membrane in one of the two compartments of
the tank. The pressure on this compartment is increased to
exceed the osmotic pressure for that particular waste in order
to cause the water to penetrate the membrane, carrying with
it only a small amount of dissolved materials. Therefore, the
dissolved material in the wastewater gets concentrated con-
tinuously, while highly purified water collects in the other
compartment.
The performance of the reverse-osmosis process depends
mainly on (1) the membrane semipermeability or its effi-
ciency to separate dissolved material from the wastewater,
and (2) the membrane permeability or the total amount of
water that can be produced with appropriate efficiency for
the removal of dissolved materials. It has been reported that
the conventional cellulose-acetate membranes give adequate
separation efficiency, but the flow rate of water is too small
to be of practical interest. However, cellulose-acetate mem-
branes allow a much higher flow rate of product water, at
the same separation efficiency, which makes it applicable in
wastewater-treatment practices (Goff and Gloyne, 1970).

The operating pressure, as well as the rejection perfor-
mance of the membrane, is dependent on the membrane
porosity. Rejection performances of three graded mem-
branes with secondary sewage effluent were investigated by
Bray et al. (1969).
Merten et al. (1968) evaluated the performance of an
18.9 m
3
/day pilot reverse-osmosis unit in removing small
amounts of organic material found in the effluent of carbon
columns treating secondary effluent. With a feed pressure
of 2760 kPa and water recovery of 80 to 85%, 84% removal
of COD present in the carbon column effluent, averaging
10.8 mg/l, was achieved. Problems of clogging have occurred
when operating with waters containing high concentrations
of bicarbonate, and as such, adjustment of pH to prevent
calcium-carbonate precipitation is normally required.
Sadr Ghayeni et al. (1996) discuss issues such as flux
control and transmission in microfiltration membranes and
biofouling in reverse-osmosis membranes in their use for
the reclamation of secondary effluents. The process used
for the study consisted of a microfiltration membrane fol-
lowed by a reverse-osmosis membrane. The performance
of this combined system was evaluated by Sadr Ghayeni et
al. (1998b), as was the study of the adhesion of bacteria to
reverse-osmosis membranes (1998a).
Effluent
Transfer pipe
Storage
compartment

Filter
compartment
Collection
chamber
Air
Underdrain nozzles
Recycle
Backwash
Equalization tank
Drain
Sump
Coal
Sand
Filter
backwash
Polymer
Three-way
valve
Water level
Alum
Influent
Filter
Backwash
FIGURE 2 Typical dual-media filter (From Eckenfelder, 2000. Reprinted with permission
from McGraw-Hill.)
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980 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
A study on the processing of composite industrial effluent
by reverse osmosis was published by Sridhar et al. in 2003.

The effluent used in the study was from combined bulk drug
and pharmaceutical companies, obtaining a removal of 88%
of dissolved solids, COD, and BOD, with reasonable water
recovery. They also present a comparison between aerobic
and reverse-osmosis treatment for this effluent.
A physical-chemical process for the treatment of chemi-
cal mechanical polishing process wastewater is presented by
Lin and Yang (2004). In it the authors used chemical coagula-
tion using different coagulants followed by reverse osmosis,
obtaining water capable of being reused in the process due to
its characteristics.
Electrodialysis Electrodialysis involves the removal of
inorganic ions from water by creating an electrical potential
across two electrodes dipped in water. One of the two strips
serves as a cathode and the other as an anode. The treatments
that can be achieved by electrodialysis include:
1. Removal of inorganic ions: Under the effect of
applied potential, cations and anions migrate to
the cathode and anode, respectively. By alternat-
ing membranes, a series of concentrating and
diluting compartments can be created. For a long
run and better efficiency, it is essential that turbid-
ity, SS, colloids, and trace organics are removed
from the wastewater before it enters the electrodi-
alysis unit.
2. Effective bacteria reduction in wastewater: Most
of the municipal wastewaters contain a high con-
centration of chloride ions. Oxidation of chloride
at the anode produces chlorine, hypochlorite,
or chloramines, depending on the nature of the

wastewater. Chlorine in these forms is a good dis-
infectant and also provides an effective means of
reducing soluble BOD.
In order to reduce the operating cost of the electrodialysis pro-
cess, the eroding anodes made of aluminum or iron are now
being replaced by nonconsumable noble anodes, which appear
to have more potential in wastewater treatment (Culp and Culp,
1971). The cost of disinfection by electrodialysis is reported to
be 0.053 $/m
3
of wastewater as compared to 0.095 $/m
3
for
the conventional chlorination (unpublished proposal, 1970).
However, some other sources have reported that the cost
of electrolytic treatment of wastewater was too high for the
removal of a large percentage of secondary effluent COD.
Grimm et al. (1998) present a review of electro-assisted
methods for water purification, including electrodialysis.
Fukumoto and Haga (2004) applied this technique for the
treatment of swine wastewater with removal rates for NO
3
−
and
PO
4
−3
ions of 99% and an average color reduction of 58%.
Gas Stripping
In domestic wastewaters, most of the nitrogen that gets

converted to ammonia during biological degradation is
present either as ammonia or in organic form. When the
carbon concentration in wastewater becomes low and the
nitrifying bacteria are populous, this ammonia can be oxi-
dized by bacteria to nitrites and nitrates in the presence of
dissolved oxygen. The stripping process can be employed
either before or after secondary treatment for removing
high levels of nitrogen that is present as ammonia. If it
is to be used as pretreatment prior to a biological system,
enough nitrogen, N:BOD  5:150, must be left in the efflu-
ent to satisfy the nutritional requirement (Eckenfelder and
Barnhart, 1963).
In wastewater, ammonium ions exist in equilibrium with
ammonia and hydrogen ions:
NH
4

↔ NH
3
↑  H

(10)
At pH levels of 6 to 8, ammonia nitrogen is mostly present
in the ionized form NH
4

. Increasing the pH to above 10
changes all the nitrogen to ammonia gas, which is remov-
able by agitation. The stripping of ammonia from wastewater
is carried out with air. In this operation, wastewater is agi-

tated vigorously in a forced-draft countercurrent air-stripping
tower when the ammonia is driven out from the solution and
leaves with the air exhausted from the tower. The efficiency
of ammonia removal in the stripping process depends upon
the pH, airflow rate, tower depth, and hydraulic loading to
the tower.
Slechta and Culp (1967) have shown experimentally that
the efficiency of the ammonia-stripping process is dependent
on the pH of the wastewater for pH values up to 10.8. However,
no significant increase in ammonia removals was achieved
by elevating the pH above 10. Kuhn (1956) had come to the
same conclusion. It has also been reported that the efficiency
of the ammonia-stripping process depends on maximizing the
air–water contact within the stripping tower. Higher ammo-
nia removals and lower air requirements were obtained with
a 40  50-mm packing than with a 100  100-mm packing.
Increased tower depth, which provides additional air–water
contact, results in greater ammonia removals and lower air
requirements. Ammonia removals of 90%, 95%, and 98%
were obtained at airflow rates of 1875, 3000, and 6000 m
3
per
cubic meter of wastewater, respectively.
Gas stripping is also used for removal of H
2
S and VOCs
from wastewater.
Ion Exchange
The ion-exchange process has been adopted successfully
in wastewater-treatment practice for removing most of the

inorganic dissolved salts. However, the cost of this method
for wastewater treatment cannot be justified unless the efflu-
ent water is required for multiple industrial municipal reuse.
One of the major applications of this technique is the treat-
ment of plating-industry wastewater, where the recovery of
chrome and the reuse of water make it an attractive choice
(Eckenfelder, 2000).
Gaffney et al. (1970) have reported that the modified
DESAL process, developed for treating acid mine drainage
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PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 981
waters, can be applied successfully to the treatment of sec-
ondary sewage effluent. This process consists of passing
secondary sewage-plant effluent upflow through an ion-
exchange unit filled with a weak base anion exchange resin,
Amberlite IRA-68, operated on a bicarbonate cycle. The
effluent with a pH of 6.0 is then treated with a small quan-
tity of bentonite and cationic flocculant, Prima floc C-7, fol-
lowed first by aeration to drive out carbon dioxide, and then
lime softening in proportion to its hardness concentration.
A dosage of 30 mg/l of bentonite, 3 to 5 mg/l of polyelec-
trolyte, and normal lime levels are required. The effluent
that is partially desalinated and essentially free of nitrates,
phosphates, chlorides, alkyl benzene sulfonate (ABS), and
COD can be produced. If the salinity is too high, it may be
reduced further by passing a portion of the effluent through
a weak acid cation, Amberlite IRC-84. It has been observed
that IRA-68 can remove much of the organic contents and
COD, thereby eliminating or markedly reducing the need for

carbon treatment.
Slechta and Culp (1967) tested a cationic resin, Duolite
C-25, for the removal of ammonia nitrogen from the carbon
column effluent that was containing ammonia nitrogen in
the range of 18 to 28 mg/l as nitrogen. A 100-mm-diameter
Plexiglas cylinder filled to a depth of 700 mm with the resin
served as the pilot ion-exchange column. The rate of appli-
cation of influent waste to the ion-exchange column was
0.4 m
3
/min per cubic meter of resin. Following breakthrough
of the ammonia nitrogen to 1 mg/l, the bed was backwashed
and the resin was regenerated. On the average, about 400 bed
volumes of carbon column effluent had been passed through
the ion-exchange resin prior to a breakthrough to 1 mg/l
ammonia nitrogen. However, considering the operating and
capital costs, they concluded that the ammonia-stripping
process was more efficient.
Nitrate nitrogen, present in the effluent from the acti-
vated sludge process, has been removed by anion exchange
regenerated with brine by R. Eliassen and Bennett (1967).
This ion-exchange process also removes phosphates and
some other ions; however, pretreatment by filtration is
essential. The resin is restored by treatment with acid and
methanol.
The removal of heavy metals with Mexican clinoptilo-
lite was studied by Vaca Mier et al. (2001). In this study the
interactions of lead, cadmium, and chromium competed for
the ion-exchange sites in the zeolite. The authors also stud-
ied the influence of such factors as the presence of phenol

and the pH of the solution to be treated.
Adsorption
Application of adsorption on granular active carbon, in
columns of counterflow fluidized beds, for the removal of
traces or organic pollutants, detergents, pesticides, and other
substances in wastewater that are resistant to biological deg-
radation has become firmly established as a practical, reliable,
and economical treatment (Slechta and Culp, 1967; Weber,
1967; Parkhurst et al., 1967; Stevens and Peters, 1966;
Presecan et al., 1972).
Adsorption can also be accomplished with powdered
carbon (Davies and Kaplan, 1964; Beebe and Stevens, 1967),
which is mixed in wastewater, flocculated, and ultimately
settled. However, there are certain problems associated with
the use of powdered carbon. These are: (1) that large quanti-
ties of activated carbon are needed in wastewater treatment,
because it is used only on a once-through basis, and han-
dling of such large quantities of carbon also creates a dust
problem, and (2) problems in disposal of precipitated carbon
unless it is incinerated along with the sewage sludge.
Carbon-Adsorption Theory Less polar molecules, includ-
ing soluble organic pollutants, are removed by adsorption
on a large surface area provided by the activated carbon.
Smaller carbon particles enhance the rate of pollutant
removal by providing more total surface area for adsorption,
partial deposition of colloidal pollutants, and filtration of
larger particles. However, it is almost always necessary to
remove finely divided suspended matter from wastewater by
pretreatment prior to its application on a carbon bed.
Depending on the direction of flow, the granular carbon

beds are either of the downflow-bed type or upflow-bed type.
Downflow carbon beds provide the removal of suspended
and flocculated materials by filtration beside the absorption
of organic pollutants. As the wastewater passes through the
bed, the carbon nearest the feed point eventually becomes sat-
urated and must be replaced with fresh or reactivated carbon.
A countercurrent flow using multiple columns in series is
considered more efficient. The first column is replaced when
exhausted, and the direction of flow is changed to make that
column the last in the series. Full countercurrent operation
can best be obtained in upflow beds (Culp and Culp, 1971).
Upflow carbon columns for full countercurrent opera-
tions may be either of the packed-bed type or expanded-
bed type. Packed beds are well suited to treatment of wastes
that contain little or no SS, i.e., turbidity less than 2.5 JTU.
However, the SS invariably present in municipal and indus-
trial wastewaters lead to progressive clogging of the carbon
beds. Therefore, expanded-bed upflow columns have certain
potential advantages in operation of packed-bed adsorbers
for treating wastes that contain SS. In expanded-bed-type
adsorbers, water must be passed with a velocity sufficient
to expand the bed by about 10%, so that the bed will be
self-cleaned.
Experiments conducted by Weber et al. (1970) have
shown that expanded-bed and packed-bed adsorption sys-
tems have nearly the same efficiency with regard to the
removal of soluble organic materials from trickling-filter
effluent, under otherwise similar conditions. The packed-
bed system was found to be more effective for removal of
SS, but the clogging that resulted from these solids required

higher pumping pressure and more frequent cleaning of
the carbon beds. Because of the time elapsed in cleaning,
the expanded-bed production was about 9% more than the
packed-bed production.
The Lake Tahoe Water Reclamation Facilities, described
by Slechta and Culp (1967), included pretreatment of second-
ary effluent by chemical clarification and filtration, thereby
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© 2006 by Taylor & Francis Group, LLC
982 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
providing a highly clarified feed and permitting an extended
operation of carbon beds. Carbon beds were of the upflow
full-countercurrent columns and were usually operated as
packed types since the turbidity of the applied water was
always less than 0.3 JTU. The columns were also operated at
times as expanded beds by drawing 10% of the carbon.
The efficiency of carbon bed treatment depends on:
1. Contact time between the carbon and the
wastewater
2. The pH of the wastewater (below pH of 9.0,
the rate of adsorption of organics in wastewater
increases with decreasing pH)
3. Temperature of the wastewater
4. Quality of the influent.
Carbon-Bed Design The following are the important design
parameters used in the design of activated-carbon beds:
1. Properties of filtering material: The two most
common sizes of granular carbon normally used
for wastewater treatment are 8  30 mesh and
12  14 mesh; 8  30 mesh carbon is preferable,

although its surface area is less, because it reduces
losses during regeneration, head loss is less, and
the operation of the filter becomes easier. Culp and
Culp (1971) have reported the desirable physical
properties for granular activated carbon for use in
wastewater treatment.
2. Depth of carbon bed: 3 to 10 m.
3. Flow rates: 140 to 700 m
3
/min per square meter
of column cross-sectional area. For optimum per-
formance of the bed, the actual depth and rate of
flow should be determined by a dynamic pilot-
plant test in the laboratory.
4. Activated carbon contact time: 15 to 35 mm,
depending on the objective of treatment and the
impurities to be removed from the wastewater.
A diagram of a carbon-gas-adsorption process is presented
in Figure 3.
In the 1970s, over 30 granular activated-carbon plants
were designed in the United States for use at municipal
wastewater-treatment plants (DeJohn and Edwards, 1981).
Thirteen of the plants are classed as physical-chemical and
15 as tertiary treatment plants, and 4 use carbon to dechlori-
nate. According to the authors, there have been some prob-
lems encountered at certain physical-chemical and tertiary
treatment plants, but in their opinion, granular activated
carbon is a viable treatment alternative when applied under
proper conditions (Grieves et al., 1964).
One of the changes in conventional treatment technology is

the use of the PACT (Powdered Activated Carbon Treatment)
process using powdered carbon in the aeration tank of an
activated sludge system (Meidl, 1981). The development
Backwash effluent
return
Backwash
effluent
sump
Column
1
Column
2
Column
3
Column
4
From storage
reservoir
Raw water
feed pump
Virgin
carbon
makeup
Slurry
mixing
tank
Regenerated
carbon
return
Regenerated

carbon
storage
Utility
water
High-pressure
water
Eductor
Quench
tank
Spent
carbon
tank
Eductor
High-pressure
water
Wet
scrubber
Multiple-
hearth
regen-
eration
furnace
Eductor
High-pressure
water
Utility
water
Final effluent
Effluent
retention

sump
Back-
wash
sump
Backwash
pump
FIGURE 3 Carbon-adsorption process diagram (From Eckenfelder, 2000. Reprinted with permission from
McGraw-Hill.)
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© 2006 by Taylor & Francis Group, LLC
PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 983
of PACT in municipal wastewater treatment resulted from
the inability of the physical-chemical treatment process
to adequately treat wastewater. This process has been used
successfully to treat domestic wastewater from a residential
population of 30,000 in Vernon, Connecticut, and many other
plants have been under construction. Similar applications of
combined powdered-carbon and activated-sludge treatment
to various industrial wastewaters, particularly coal-gasification
wastewaters, are shown to be successful.
Miyake et al. (2003) studied the adsorption equilib-
rium isotherms of trichloroethylene (TCE) vapor stripped
from TCE-polluted waters. These results can be used for
wastewater treatment of waters with the same pollutant.
A combined Al(III) coagulation/carbon adsorption process
for the treatment of reactive dyes in synthetic wastewater
was proposed by Papic et al. (2004). This process achieved
99.9% reduction of the dyes in the wastewater as well as
95.7 and 91.3% COD reduction for the two waters used.
They conclude that the proposed process has many advan-

tages, such as high efficiency, low use of coagulant, mini-
mal sludge production, and high-quality product water with
reuse potential.
Adsorption of Pollutants on Biomaterials A review of
potentially low-cost adsorbents for heavy metals was pre-
sented by Bailey et al. (1999). Minamisawa et al. (2004)
investigated the adsorption of cadmium and lead ions on
different biomaterials, concluding that this is a promising
alternative for the removal of these ions. Another review was
published in 2004 by Gardea-Torresdey et al., concluding
that Cd, Cu, Ni, Cr, and other ions have been successfully
removed from solutions using different biomaterials. Gong
et al. (2005) studied the use of peanut hull as a biosorbent
for the removal of anionic dyes in a solution, obtaining sorp-
tion capacities of between 13.99 and 15.60 mg per gram of
biosorbent for three different dyes.
Flotation
Surface-active contaminants, if present in wastewater, will
produce foam upon aeration. This foam rises to the surface
of the wastewater and can be separated and concentrated.
Moreover, as the foam generates and rises, certain sus-
pended impurities also get removed by entrainment. Thus,
the foam-separation process can be developed to provide a
selective removal of soluble and colloidal pollutants in vari-
ous concentrations from water or wastewater. The process
may either utilize the surface-active impurities present in the
wastewater or may require the addition of a specific surface-
active agent prior to aeration; soluble or colloidal impurities
of interest may be precipitated to improve their removal.
Factors affecting the efficiency of the process of foam

separation are:
1. Airflow rate/surface-active agent or airflow-rate-
to-waste-flow-rate ratio (the removal efficiency
increases when increasing the airflow rate, but
yields wetter foam)
2. Air-bubble size (fine-bubble aeration improves
the efficiency of foam separation, whereas coarse
bubbles or deck aeration are not efficient)
3. Nature and concentration of surface-active agents
4. Foam stability
5. pH of the wastewater
6. Detention period (a short aeration time, 5 minutes
or so, is considered sufficient)
7. Surface-to-volume ratio (a large surface-to-volume
area is conducive to higher efficiency)
The process of foam separation has been used successfully
in a number of waste-treatment applications. These include
(1) removal of surface-active materials such as ABS from sec-
ondary effluent sewage (Klein and McGauhey, 1963; Grieves
et al., 1964; Brunner and Lemlich, 1963; Fldib, 1963);
(2) removal of radioactive ions from dilute aqueous solutions
by the addition of anionic surface agents (Schoen and Mazella,
1961; Schoen et al., 1962; Schnepf et al., 1959); (3) removal
of specific surfactants from refining and petrochemical waste-
waters (Grieves and Wood, 1963); (4) foam fractionation of
phenol (phenolate) from aqueous solutions using a cationic
surfactant, ethyl hexadecyl dimethylammonium bromide, as
the foaming agent (Grieves and Aronica, 1966); (5) the treat-
ment of cyanide and acid chromate wastes (cyanide is precipi-
tated with ferrous ions, and the ferrocyanide precipitates are

floated with a cationic surfactant in a pH range of 5 to 7; acid
chromate is reduced and precipitated as Cr(OH)
3
, and these
precipitates are floated with an anionic surfactant [Grieves,
1972]); (6) the treatment of liquid wastes from the scrubbing
of phosphate and fluoride from air-pollution emissions of the
phosphoric-acid-manufacturing industry (these include pre-
cipitation by lanthanum (III), followed by flotation with an
anionic surfactant [Grieves, 1972]); (7) clarification of turbid
raw water supplies by microflotation-activated carbon process
(Grieves, 1972); and (8) physical separation of SS and coag-
ulated dissolved organic impurities from wastewaters. ABS
serves as activator for bubble attachment in flotation treatment
of sewage (Klein and McGauhey, 1963). Other applications
include the treatment of mine-drainage wastes combined with
secondary sewage effluents and removal of H
2
S from sour
wastes.
An overview on flotation in wastewater treatment was
published by Rubio et al. in 2002. The authors explain the
process, present conventional and emerging flotation tech-
niques and processes, and discuss the applications of the
technique to different compounds. An example of a dissolved
air flotation (DAF) process is presented in Figure 4.
Chemical Processes
An extensive review on catalytic abatement of water pol-
lutants was published by Matatov-Meytal and Sheintuch
in 1998. In it they present the oxidation and reduction pro-

cesses involved as well as a discussion on catalyst support
and deactivation. A discussion on the use of iron for waste-
water treatment was published by Waite (2002). This article
presents the research challenges and the new possibilities in
C016_005_r03.indd 983 11/22/2005 11:25:20 AM
© 2006 by Taylor & Francis Group, LLC
984 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
this area. A review on the use of ferrate (VI) salt as a coagu-
lant and oxidant for water and wastewater treatment is pre-
sented by Jiang and Lloyd (2002). In this paper the authors
demonstrate the advantages of this approach in the treatment
of microorganisms, heavy metals, and SS, as well as present
the difficulties associated with this technique.
Ghoreishi and Haghighi (2003) propose a combined
bisulfite catalyzed sodium borohydride reduction followed
by activated sludge for the treatment of nonbiodegradable
textile effluent, reposting reductions of BOD, COD, and
TSS of 74–88%, 76–83%, and 92–97% respectively. Lin and
Wang (2004) investigated the performance of a proposed
granulated activated carbon bed combined with ozonation
and preceded by chemical coagulation, obtaining interest-
ing results. Akcil (2003) discusses the advantages of using
biological methods for the treatment of cyanide in gold-mill
effluents as compared to well-established chemical meth-
ods. Chung et al. (2003) evaluated the performance of a
combined chemical absorption–biological oxidation system
for the removal of H
2
S from gaseous streams such as those
produced by livestock wastewater-treatment plants. They

demonstrated the potential of this technique and obtained
reductions on the order of 85%. Another combined approach
is presented by Libra and Sosath (2003). In this case they
used ozonation followed by a biological process for the treat-
ment of textile wastewater, comparing two configurations
of treatment processes, concluding that the most attractive
alternative is the simplest: ozonation followed by aerobic
treatment as compared to anaerobic, aerobic, ozonation, and
aerobic treatments for their effluent and conditions.
A comprehensive review on the properties of alumina,
the chemical reactions involved in its use in water treatment,
and adsorption and catalysis using alumina was published
by Kasprzyk-Hordern in 2004. An interesting review on the
enhancement of biodegradability of industrial wastes by
chemical-oxidation pretreatment is presented by Mantzavinos
and Psillakis in 2004. This exhaustive review includes many
different pollutants, trends, and process schemes used as
segregation by effluent type; evaluation of the pretreatment
steps; and modeling of the individual steps involved.
Aiyuk et al. (2004) propose a chemically enhanced pri-
mary treatment followed by a UASB reactor for the treatment
of domestic wastewater. The chemical pretreatment consisted
of the addition of FeCl
3
or Al
2
(SO
4
)
3

and polymers in a mixing
tank, and a posttreatment of the biologically treated water was
achieved by zeolite adsorption for NH
4

removal. Another
combined solution was proposed by Bressan et al. in 2004.
This approach includes the use of an enhanced Fenton process
followed by biological treatment of olive-mill wastewater.
Oxidative, Photochemical, and Electron-Beam
Processes
Oxidizing agents like chlorine, ozone, hydrogen peroxide,
potassium permanganate, and ultraviolet irradiation have been
used successfully in oxidizing and stabilizing certain impu-
rities like hydrogen sulfide, phenol, cyanide, and selected
refractory organic substances. The reaction of chlorine with
certain organic matter present in wastewater to form a more
harmful persistent chemical has raised a serious question
of continuing the use of chlorine for disinfection of waste-
water effluents. Ozone is gradually becoming more popular,
because it has strong oxidizing and disinfecting capacity and
leaves no harmful residuals. It has been shown that ozone
in combination with photochemical oxidation economically
removed inorganic, organic, and toxic refractory species and
effectively destroyed phenol in a bubble column or a stirred
cell (Wall, 1980; Otake, 1979). Ganes and Staubach (1980)
have reported the kinetics of the reaction between ozone and
nitrilotriacetate in water and the effects of pH, metal content,
and natural organics on the rate and extent of degradation.
In 1993, Legrini et al. published an extensive review

on photochemical processes for water treatment, including
UV, H
2
O
2
/UV, ozone/UV, O
3
/H
2
O
2
/UV, TiO
2
/UV, vacuum
UV, photochemical electron-transfer processes, and energy-
transfer processes. In 1999, Andreozzi et al. published studies
on the use of O
3
/UV and O
3
/H
2
O
2
for the treatment of mineral-
oil-polluted wastewaters, performing different experiments
and achieving an 80 to 90% reduction of COD for the O
3
/UV
treatment (Andreozzi et al., 1999). A discussion of the different

advanced oxidation processes (AOP), as well as experimental
apparatus and working procedures for the study of the applica-
tion of this technique, is presented in Andreozzi et al. (2000).
An extensive review on photocatalytic degradation was
presented by Bhatkhande et al. (2001). In it they include
a description of the process, the mechanisms implied, the
compounds that can be degraded with it, and the variables
that can affect this technique. Another review was pub-
lished by Kabra et al (2004), concluding that this process
can be used to treat industrial wastewater for the removal
of metal ions and nonbiodegradable organics. Another con-
clusion is that the costs of this method are slightly higher
than for conventional methods, but that future research can
make a competitive option. An interesting article on the
evaluation of the use of peracetic acid for the disinfection of
the effluent of Montreal’s wastewater-treatment plant was
FIGURE 4 Conventional DAF unit with water recycle
to the saturator (From Rubio et al., 2002, with permission
from Elsevier).
C016_005_r03.indd 984 11/22/2005 11:25:20 AM
© 2006 by Taylor & Francis Group, LLC
PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 985
published by Gehr et al. in 2003. In this study the authors
presented and evaluated the different alternatives (with the
exception of chlorine, due to environmental regulations)
arriving at the conclusion that using the current process,
the economically viable alternative is UV, while if some
changes are made upstream, the use of peracetic acid could
be a viable alternative.
A study on the application of different AOPs to the treat-

ment of textiles, Kraft bleaching, photoprocessing, and phar-
maceutical wastewaters was published by Balcoglu et al. in
2003. They conclude that the efficiency of the AOP process
used for a particular application depends upon the pretreat-
ment used, and concentrations and types of pollutants present
in the influent.
Adesina (2004) investigated the use of photocatalysis
for the treatment of spent industrial Bayer liquor and detox-
ification of paper-mill effluents, among others. The use of
sunlight as an energy source is also discussed. A compari-
son of different AOPs and chemical-treatment options was
conducted by Azbar et al. (2004) for the reduction of color
and COD from an acetate- and polyester-dyeing process.
They conclude that AOPs have better performances than
chemical-coagulation methods for the parameters stud-
ied. They also found that UV/H
2
O
2
achieved 99% and
96% COD and color removal, respectively. Their choice
from the economic point of view was the Fenton’s reagent
process. The removal of the drug diclofenac by means of
UV/H
2
O
2
was studied by Vogna et al. (2004), showing that
the proposed treatment was effective for the degradation of
the drug. The behavior of the process Fe(III)/Air/UV was

studied by Andreozzi and Marotta (2004) by using ben-
zoic acid as the molecule to be treated, with the goal of
developing kinetic models for this process. A study on the
treatment of cork-processing wastewater was published by
Acero et al. in 2004. They evaluated the use of different
combinations of UV, H
2
O
2
, and O
3
and Fenton’s reagent
and photo-Fenton processes for the effluent under study
and concluded that the best options that produce reusable
water are those involving ozone.
Broad reviews on oxidation technologies at ambient
conditions and on hybrid methods for wastewater treatment
were published by Gogate and Pandit (2004a, 2004b). Tabrizi
and Mehrvar (2004) present an interesting article on the inte-
gration of AOPs and biological processes, including recent
developments, trends, and advances in this field. A review
on the degradation of chlorophenols via AOP was published
by Pera-Titus et al. in 2004. Among their conclusions is that
although photocatalytic processes show higher half reaction
times, they do not require oxidants or further separation of
byproducts after the reaction.
Ding et al. (1996) present a review of catalytic oxi-
dation in supercritical water, including the reactions
involved, the processes available, a comparison with sub-
critical water oxidation, and an extensive review of the

catalysts available. Kritzer and Dinjus (2001) published
an interesting evaluation of the problems of supercritical
water oxidation, with discussion and suggestions for its
improvement.
Ultrasound Ultrasound is being studied as an alternative solu-
tion for environmental problems. This process works by gen-
eration of highly reactive oxidizing species, such as hydroxyl,
hydrogen, and hydroperoxyl radicals as well as hydrogen per-
oxide by means of ultrasound waves (Vajnhandl and Majcen
Le Marechal, 2005). In their review they include the use of
ultrasound in the textile industry and its wastewaters.
Electrochemical Oxidation Panizza and Cerisola (2004)
published results on a series of experiments using an elec-
trochemical cell for the treatment of synthetic-tannery
wastewater using two different electrodes under various
experimental conditions, concluding that electrochemical
methods can be effectively applied for the final treatment
of these effluents, achieving total COD, tannin, and ammo-
nium removals.
Electron-Beam Wastewater Treatment Water irradiation
with ionizing radiation generates several very reactive ions
and molecules. Getoff presents a review and the state of the
art for radiation-induced degradation of water pollutants
(1996). His group has studied the use of radiation for disin-
fection and decomposition of pollutants in water and waste-
water for years. Among the experimental factors proposed to
affect the efficiency of this process in pollutant degradation
are: form of radiation, energy, absorbed dose and dose rate,
pollutant concentration, pH, temperature, effect of oxygen
and ozone, presence of ozone and TiO

2
, and molecular struc-
ture of the pollutants (2002).
Pikaev et al. (2001) applied electron beams followed by
coagulation for the treatment of mixed distillery and munici-
pal wastewater; they conclude that the proposed scheme can
treat the effluent at lower cost than the biological and sedi-
mentation processes. In 2002 his group published pilot-plant
experiments using electron-beam and biological oxidation
for the treatment of dyeing wastewater. In this research they
conclude that the proposed method reached the desired efflu-
ent characteristics in about 8 hours of treatment, as compared
to 17 hours for biological treatment alone (Pikaev, 2002).
In collaboration with researchers from Korea, he also used
electron beams combined with coagulation, flocculation, and
biological processes for the treatment of paper-mill effluents.
This research concluded with the design of a commercial
plant for the treatment of 15,000 m
3
/day of wastewater with
80% of water reuse (Shin et al., 2002). In a final publication,
Pikaev (2002) presents data on the treatment of different
pollutants, including carboxylic acids, distillery slops, and
petroleum products. In this work the author presents an eco-
nomic evaluation of a commercial plant, concluding that the
treatment costs for the proposed technology are about half of
conventional methods.
REFERENCES
Acero, J.L., Javier Benitez, J. F., Heredia, J.B.D., and Leal, A.I. (2004). Chemi-
cal treatment of cork-processing wastewaters for potential reuse. Journal

of Chemical Technology and Biotechnology, 79(10), 1065–1072.
Adesina, A.A. (2004). Industrial exploitation of photocatalysis: progress, per-
spectives and prospects. Catalysis Surveys from Asia, 8(4), 265–273.
C016_005_r03.indd 985 11/22/2005 11:25:21 AM
© 2006 by Taylor & Francis Group, LLC
986 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
Aiyuk, S., Amoako, J., Raskin, L., van Haandel, A., and Verstraete, W.
(2004). Removal of carbon and nutrients from domestic wastewater
using a low investment, integrated treatment concept. Water Research,
38(13), 3031–3042.
Akcil, A. (2003). Destruction of cyanide in gold mill effluents: biological
versus chemical treatments. Biotechnology Advances, 21(6), 501–511.
Albertson, O.E. and Sherwood, R.J. (1967). Phosphate extraction process.
Paper presented at the Water Pollution Control Federation meeting,
Yakima, Washington, October.
Andreozzi, R. and Marotta, R. (2004). Removal of benzoic acid in aque-
ous solution by Fe(III) homogeneous photocatalysis. Water Research,
38(5), 1225–1236.
Andreozzi, R., Caprio, V., Insola, A., and Marotta, R. (1999). Advanced
oxidation processes (AOP) for water purification and recovery. Cataly-
sis Today, 53(1), 51–59.
Andreozzi, R., Caprio, V., Insola, A., Marotta, R., and Sanchirico, R.
(2000). Advanced oxidation processes for the treatment of mineral oil-
contaminated wastewaters. Water Research, 34(2), 620–628.
Anonymous (1967). Renovation and reuse of wastewaters in Britain,
published by Water Pollution Research Laboratory.
Azbar, N., Yonar, T., and Kestioglu, K. (2004). Comparison of various
advanced oxidation process and chemical treatment methods for COD
and color removal from a polyester and acetate fiber dyeing effluent.
Chemosphere, 55(1), 35–43.

Babbit, H.E., Donald, J.J., and Cleasby, J.L. (1962). Water Supply Engi-
neering. McGraw-Hill Book Company, New York.
Bailey, S.E., Olin, T.J., Bricka, R.M., and Adrian, D.D. (1998). A review of
potentially low-cost sorbents for heavy metals. Water Research, 33(11),
2469–2479.
Balcoglu, I.A., Alaton, I.A., Ötker, M., Bahar, R., Bakar, N., and Ikiz,
M. (2003). Application of advanced oxidation processes to different
industrial wastewaters. Journal of Environmental Sciences and Health,
Part A—Toxic/Hazardous Substances and Environmental Engineering,
A38(8), 1587–1596.
Baumann, E.R. and Oulman, C.S. (1970). Sand and diatomite filtration
practices. Water Quality Improvement by Physical and Chemical Pro-
cesses, Water Resources Symposium No. 3, University of Texas Press,
Austin and London, 104.
Beebe, R.L. and Stevens, J.I. (1967). Activated carbon system for wastewater
renovation. Water and Waste Engineering, 4(1), 43.
Bes-Pia, A., Iborra-Clar, A., Mendoza-Roca, J.A., Iborra-Clar, M.I., and
Alcaina-Miranda, M.I. (2004). Nanofiltration of biologically treated
textile effluents using ozone as a pre-treatment. Desalination, 167,
387–392.
Bes-Pia, A., Mendoza-Roca, J.A., Alcaina-Miranda, M.I., Iborra-Clar, A.,
and Iborra-Clar, M.I. (2003). Combination of physico-chemical treat-
ment and nanofiltration to reuse wastewater of a printing, dyeing and
finishing textile industry. Desalination, 157(1–3), 73–80.
Bhatkhande, D.S., Pangarkar, V.G., and Beenackers, A.A.C.M. (2001). Photo-
catalytic degradation for environmental applications—a review. Journal
of Chemical Technology and Biotechnology, 77(1), 102–116.
Bishop, D.F., O’Farrell, T.P., and Stanberg, J.B. (1972). Physical-chemical
treatment of municipal wastewater. Journal of the Water Pollution Con-
trol Federation, 44, (3), 361.

Bray, D.T., Merten, U., and Augustus, M. (1969). Chemical Engineering,
76(4), 60.
Bressan, M., Liberatore, L., d’Alessandro, N., Tonucci, L., Belli, C., and
Ranalli, G. (2004). Improved combined chemical and biological treat-
ments of olive oil mill wastewaters. Journal of Agricultural and Food
Chemistry, 52(5), 1228–1233.
Brunner, C.A. and Lemlich, R. (1963). Foam fractionation: standard sepa-
rator and refluxing columns. Industrial Engineering Chemistry, 2,
297–300.
Buzzell, J.C. and Sawyer, C.H. (1967). Removal of algal nutrients from raw
wastewater with lime. Journal of the Water Pollution Control Federa-
tion, 39(10), R16.
Chung, Y C., Ho, K L., and Tseng, C P. (2003). Hydrogen sulfide gas
treatment by a chemical-biological process: chemical absorption and
biological oxidation steps. Journal of Environmental Science and
Health, Part B—Pesticides, Food Contaminants, and Agricultural
Wastes, 38(5), 663–679.
Conley, W.R., Jr. and Hsiung, K. (1965). Design and application of mul-
timedia filters. Journal of the American Water Works Association,
57(10), 1333.
Convery, J.J. (1968). Phosphorus removal by tertiary treatment with lime and
alum. Paper presented at the FWPCA Symposium on Nutrient Removal
and Advanced Waste Treatment, Tampa, Florida, November 15.
Culp, R.L. and Culp, G.L. (1971). Advanced Wastewater Treatment. Van
Nostrand Reinhold Company, New York.
Culp, G.L. and Hansen, S.P. (1967a). Extended aeration effluent polishing
by mixed media filtration. Water and Sewage Works, 114(2), 46.
Culp, G.L. and Hansen, S.P. (1967b). How to reclaim wastewater for reuse.
American City, June, 96.
Davies, D.S. and Kaplan, R.A. (1964). Activated carbon eliminates organ-

ics. Chemical Engineering Progress, 60(12), 46.
de-Bashan, L.E. and Bashan, Y. (2004). Recent advances in removing phos-
phorus from wastewater and its future use as fertilizer (1997–2003).
Water Research, 38(19), 4222–4246.
DeJohn, P.B. and Edwards, R.W. (1981). Application of GAC to municipal
wastewaters. Proceedings of the International Conference on the Appli-
cation of Adsorption to Wastewater Treatment, Vanderbilt University,
Nashville, Tennessee, 109–127.
Dillingham, J.H., Cleasby, J.L., and Baumann, E.R. (1966). Optimum design
and operation of diatomite filtration plants. Journal of the American
Water Works Association, 58(6), 657.
Dillingham, J.H., Cleasby, J.L., and Baumann, E.R. (1967). Diatomite filtra-
tion equations for flat and cylindrical septa. Journal of the Sanitary Engi-
neering Division, American Society of Civil Engineers, 93(2) (SA1), 41.
Ding, Z.Y., Frisch, M.A., Li, L., and Gloyna, E.F. (1996). Catalytic oxidation
in supercritical water. Industrial and Engineering Chemistry Research,
35(10), 3257–3279.
Eckenfelder, W.W. (1966). Industrial Water Pollution Control. McGraw-Hill
Book Company, New York.
Eckenfelder, W.W. (2000). Industrial Water Pollution Control. McGraw-Hill
Book Company, New York.
Eckenfelder, W.W. and Barnhart, E.L. (1963). Performance of high rate
trickling filter using selected media. Journal of the Water Pollution
Control Federation, 35(12), 1535.
Ecodyne (1972). Physical-chemical sewage treatment plant for the village
of Rosemount. Environmental Currents News, Environmental Science
and Technology, 6(4), 306.
Eliassen, K. and Bennett, G. (1967). Anion exchange and filtration techniques
for wastewater renovation. Journal of the Water Pollution Control Fed-
eration, 39(10), R81.

Eliassen, R. and Bennett, G.E. (1967). Renovation of domestic and industrial
waste water. Paper presented at the International Conference on Water
for Peace, Washington, DC, May.
Fane, A.G. (1996). Membranes for water production and wastewater reuse.
Desalination, 106(1–3), 1–9.
Fldib, L.A. (1963). Renovation of wastewater by foam fractionation.
Paper presented before the Division of Water and Waste Chemistry,
American Chemical Society, 143rd National Meeting, Cincinnati,
Ohio, January 15.
Fukumoto, Y. and Haga, K. (2004). Advanced treatment of swine waste-
water by electrodialysis with a tubular ion exchange membrane. Animal
Science Journal, 75(5), 479–485.
Gaffney, J.G., Junin, R., and Downing, D.G. (1970). Ion exchange for
industrial water. Water Quality Improvement by Physical and Chemi-
cal Processes, Water Resources Symposium No. 3, University of Texas
Press, Austin and London, 258.
Galambos, I., Mora Molina, J., Jaray, P., Vatai, G., and Bekassy-Molnar E.
(2004). High organic content industrial wastewater treatment by mem-
brane filtration. Desalination, 162, 117–120.
Galarneau, E. and Gehr, R. (1996). Phosphorus removal from wastewaters:
experimental and theoretical support for alternative mechanisms. Water
Research, 31(2), 328–338.
Ganes, L.M. and Staubach, J.A. (1980). Reaction of nitrilotiacetate with ozone
in model and natural waters. Environmental Science and Technology,
14, 571.
Gardea-Torresdey, J.L., dela Rosa, G., and Peralta-Videa, J.R. (2004). Use
of phytofiltration technologies in the removal of heavy metals: a review.
Pure and Applied Chemistry, 76(4), 801–813.
C016_005_r03.indd 986 11/22/2005 11:25:21 AM
© 2006 by Taylor & Francis Group, LLC

PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 987
Gehr, R., Wagner, M., Veerasubramanian, P., and Payment, P. (2003). Dis-
infection efficiency of peracetic acid, UV and ozone after enhanced
primary treatment of municipal wastewater. Water Research, 37(19),
4573–4586.
Getoff, N. (1996). Radiation-induced degradation of water pollutants—state
of the art. Radiation Physics and Chemistry, 47(4), 581–593.
Getoff, N. (2002). Factors influencing the efficiency of radiation-induced
degradation of water pollutants. Radiation Physics and Chemistry,
65(4–5), 437–446.
Ghoreishi, S.M. and Haghighi, R. (2003). Chemical catalytic reaction and
biological oxidation for treatment of non-biodegradable textile effluent.
Chemical Engineering Journal, 95(1–3), 163–169.
Goff, D.L. and Gloyne, E.F. (1970). Reverse osmosis development. Water
Quality Improvement by Physical and Chemical Processes, Water
Resources Symposium No. 3, University of Texas Press, Austin and
London, 312.
Gogate, P.R. and Pandit, A.B. (2004a). A review of imperative technologies
for wastewater treatment I: oxidation technologies at ambient conditions.
Advances in Environmental Research, 8(3–4), 501–551.
Gogate, P.R. and Pandit, A.B. (2004b). A review of imperative technologies
for wastewater treatment II: hybrid methods. Advances in Environmental
Research, 8(3–4), 553–597.
Gong, R., Ding, Y., Li, M., Yang, C., Liu, H., and Sun, Y. (2005). Utilization
of powdered peanut hull as biosorbent for removal of anionic dyes from
aqueous solution. Dyes and Pigments, 64(3), 187–192.
Grieves, R.B. (1972). Water and wastewater treatment applications of the
foam separation process. Paper presented at the Second Annual Environ-
mental Engineering and Science Conference, University of Louisville,
Louisville, Kentucky, April 20–21.

Grieves, R.B. and Aronica, R.C. (1966). Foam separation of phenol with
a cationic surfactant. Air and Water Pollution International Journal,
10(1), 31–40.
Grieves, R.B., Crandall, C.J., and Wood, R.K. (1964). Foam separation of
ABS and other surfactants. Air and Water Pollution International Jour-
nal, 8(8–9), 501–513.
Grieves, R.B. and Wood, R.K. (1963). Continuous accumulation in foam
for the treatment of refining and petrochemical wastes. Chem. In Can.,
15, 13–15.
Grimm, J., Bessarabov, D., and Sanderson, R. (1998). Review of electro-
assisted methods for water purification. Desalination, 115(3), 285–294.
Han, B., Ko, J., Kim, J., Kim, Y., Chung, W., Makarov, I.E., Ponomarev, A.V.,
and Pikaev, A.K. (2002). Combined electron-beam and biological treat-
ment of dyeing complex wastewater: pilot plant experiments. Radiation
Physics and Chemistry, 64(1), 53–59.
Harriger, R.D. and Hoffman, F.L. (1970). Phosphorous Removal Tests—
Two Rivers, Wisconsin. for Black and Veatch Consulting Engineers.
Technical Service Department, Allied Chemical Corporation, Indus-
trial Chemical Division, Syracuse, New York.
Harriger, R.D. and Hoffman, F.L. (1971). Phosphate Removal Tests—
Springfield, Ohio. for Black and Veatch Consulting Engineers, Tech-
nical Service Department, Allied Chemical Corporation, Industrial
Chemicals Division, Syracuse, New York.
Hilal, N., Al-Zoubi, H., Darwish, N.A., Mohammad, A.W., and Abu Arabi,
M. (2004). A comprehensive review of nanofiltration membranes: treat-
ment, pretreatment, modelling, and atomic force microscopy. Desalina-
tion, 170(3), 281–308.
Howell, J.A. (2004). Future of membranes and membrane reactors in green
technologies and for water reuse. Desalination, 162, 1–11.
Jiang, J Q. and Lloyd, B. (2002). Progress in the development and use of

ferrate(VI) salt as an oxidant and coagulant for water and wastewater
treatment. Water Research, 36(6), 1397–1408.
Johns-Manville Corporation (1972). Moving bed filter system. Water and
Sewage Digest, May–June, 47.
Kabra, K., Chaudhary, R., and Sawhney, R.L. (2004). Treatment of hazardous
organic and inorganic compounds through aqueous-phase photocataly-
sis: a review. Industrial and Engineering Chemistry Research, 43(24),
7683–7696.
Kalinske, A.A. and Shell, G.L. (1968). Phosphate removal from waste
effluent and raw wastes using chemical treatment. Paper presented
at the Phosphorus Removal Conference sponsored by the FWPCA,
Chicago, Illinois.
Kasprzyk-Hordern, B. (2004). Chemistry of alumina, reactions in aqueous
solution and its application in water treatment. Advances in Colloid and
Interface Science, 110(1–2), 19–48.
Kentish, S.E. and Stevens, G.W. (2001). Innovations in separations tech-
nology for the recycling and re-use of liquid waste streams. Chemical
Engineering Journal, 84(2), 149–159.
Klein, S.A. and McGauhey, P.H. (1963). Detergent removal by surface strip-
ping. Journal of the Water Pollution Control Federation, 35(1), 100.
Kritzer, P. and Dinjus, E. (2001). An assessment of supercritical water oxi-
dation (SCWO): existing problems, possible solutions and new reactor
concepts. Chemical Engineering Journal, 83(3), 207–214.
Kuhn, P.A. (1956). Removal of ammonium nitrogen from sewage effluent.
MS Thesis, University of Wisconsin, Madison.
Lai, C.L. and Lin, S.H. (2003). Electrocoagulation of chemical mechanical
polishing (CMP) wastewater from semiconductor fabrication. Chemical
Engineering Journal, 95(1–3), 205–211.
Legrini, O., Oliveros, E., and Braun, A.M. (1993). Photochemical processes
for water treatment. Chemical Reviews, 93(2), 671–698.

Libra, J.A. and Sosath, F. (2003). Combination of biological and chemi-
cal processes for the treatment of textile wastewater containing reac-
tive dyes. Journal of Chemical Technology and Biotechnology, 78(11),
1149–1156.
Lin, S.H. and Yang, C.R. (2004). Chemical and physical treatments of
chemical mechanical polishing wastewater from semiconductor fabri-
cation. Journal of Hazardous Materials, 108(1–2), 103–109.
Lynam, B., Ettelt, G., and McAloon, T. (1969). Tertiary treatment at Metro
Chicago by means of rapid sand filtration and microstrainers. Journal
of the Water Pollution Control Federation, 41(2), 247.
Mantzavinos, D. and Psillakis, E. (2004). Enhancement of biodegradability
of industrial wastewaters by chemical oxidation pre-treatment. Journal
of Chemical Technology and Biotechnology, 79(5), 431–454.
Matatov-Meytal, Y.I. and Sheintuch, M. (1998). Catalytic abatement of
water pollutants. Industrial and Engineering Chemistry Research,
37(2), 309–326.
Meidl, J.A. (1981). Application of PACT to municipal wastewater. Proceed-
ings of the International Conference on the Applications of Adsorption
to Wastewater Treatment, Nashville, Tennessee, 357–383.
Merten, U., Nusbaum, I., and Miele, R. (1968). Organic removal by reverse
osmosis. Paper presented at the American Chemical Society Sympo-
sium on Organic Residue Removal from Wastewaters, Atlantic City,
New Jersey, September.
Minamisawa, M., Minamisawa, H., Yoshida, S., and Takai, N. (2004).
Adsorption behavior of heavy metals on biomaterials. Journal of Agri-
cultural and Food Chemistry, 52(18), 5606–5611.
Miyake, Y., Sakoda, A., Yamanashi, H., Kaneda, H., and Suzuki, M. (2003).
Activated carbon adsorption of trichloroethylene (TCE) vapor stripped
from TCE-contaminated water. Water Research, 37(8), 1852–1858.
Mollah, M.Y.A., Morkovsky, P., Gomes, J.A.G., Kesmez, M., Parga, J., and

Cocke, D.L. (2004). Fundamentals, present and future perspectives
of electrocoagulation. Journal of Hazardous Materials, 114(1–3),
199–210.
Mollah, M.Y.A., Pathak, S.R., Patil, P.K., Vayuvegula, M., Agrawal, T.S.,
Gomes, J.A.G., Kesmez, M., and Cocke, D.L. (2004). Treatment of
orange II azo-dye by electrocoagulation (EC) technique in a continuous
flow cell using sacrificial iron electrodes. Journal of Hazardous Mate-
rials, 109(1–3), 165–171.
Mollah, M.Y.A., Schennach, R., Parga, J.R., and Cocke, D.L. (2001). Elec-
trocoagulation (EC)—science and applications. Journal of Hazardous
Materials, 84(1), 29–41.
Otake, T. (1979). Photo-oxidation with ozone. Journal of Chemical Engi-
neering of Japan, 12, 289.
Panizza, M. and Cerisola, G. (2004). Electrochemical oxidation as a final
treatment of synthetic tannery wastewater. Environmental Science and
Technology, 38(20), 5470–5475.
Papic, S., Koprivanac, N., Loncaric Bozic, A., and Metes, A. (2004).
Removal of some reactive dyes from synthetic wastewater by combined
Al(III) coagulation/carbon adsorption process. Dyes and Pigments,
62(3), 291–298.
Parameshwaran, K., Fane, A.G., Cho, B.D., and Kim, K.J. (2001). Analysis
of microfiltration performance with constant flux processing of second-
ary effluent. Water Research, 35(18), 4349–4358.
C016_005_r03.indd 987 11/22/2005 11:25:22 AM
© 2006 by Taylor & Francis Group, LLC
988 PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS
Parkhurst, J.D., Dryden, F.D., McDermott, G.N., and English, J. (1967).
Pomona activated carbon pilot plant. Journal of the Water Pollution
Control Federation, 39(10), R70.
Pera-Titus, M., García-Molina, V., Banos, M.A., Gimenez, J., and Esplugas,

S. (2004). Degradation of chlorophenols by means of advanced oxida-
tion processes: a general review. Applied Catalysis B: Environmental,
47(4), 219–256.
Pikaev, A.K. (2002). New data on electron-beam purification of wastewater.
Radiation Physics and Chemistry, 65(4–5), 515–526.
Pikaev, A.K., Ponomarev, A.V., Bludenko, A.V., Minin, V.N., and Elizareva,
L.M. (2001). Combined electron-beam and coagulation purification of
molasses distillery slops: features of the method, technical and economic
evaluation of large-scale facility. Radiation Physics and Chemistry,
61(1), 81–87.
Pokhrel, D. and Viraraghavan, T. (2004). Treatment of pulp and paper mill
wastewater—a review. Science of the Total Environment, 333(1–3),
37–58.
Presecan, N.L., Touhill, J.C., and Shuckrow, A.J. (1972). Cleveland west-
erly physical chemical wastewater treatment plant. Paper presented at
the Second Annual Environmental Engineering and Science Confer-
ence, University of Louisville, Kentucky, April 20–21.
Rich, L.G. (1963). Unit Processes of Sanitary Engineering. John Wiley and
Sons, New York.
Riddick, T.M. (1961). Zeta potential and its application to difficult waters.
Journal of the American Water Works Association, 53(8), 1007.
Rizzo, J.L. and Schade, R.E. (1969). Secondary treatment with granular
activated carbon. Water and Sewage Works, 116(8), 307.
Robinson, W.T. and Maltson, R.J. (1967). A new product concept for
improvement of industrial water. Paper presented at Annual Meeting,
Water Pollution Control Federation, New York.
Roizard, D., Teplyakov, V., Favre, E., Fefilatiev, L., Lagunstsov, N., and
Khotimsky, V. (2004). VOC’s removal from water with a hybrid system
coupling a PTMSP membrane module with a stripper. Desalination,
162, 41–46.

Rose, J.L. (1968). Removal of phosphorus by alum. Paper presented at the
Phosphorus Removal Conference sponsored by the FWPCA, Chicago,
Illinois.
Rubio, J., Souza, M.L., and Smith, R.W. (2002). Overview of flotation as a
wastewater treatment technique. Minerals Engineering, 15(3), 139–155.
Rudolfs, W. and Trubnick, E.H. (1935). Activated carbon in sewage treat-
ment. Sewage Works Journal, 7(5), 852.
Sadr Ghayeni, S.B., Beatson, P.J., Schneider, R.P., and Fane, A.G. (1998a).
Adhesion of waste water bacteria to reverse osmosis membranes. Journal
of Membrane Science, 138(1), 29–42.
Sadr Ghayeni, S.B., Beatson, P.J., Schneider, R.P., and Fane, A.G. (1998b).
Water reclamation from municipal wastewater using combined micro-
filtration-reverse osmosis (ME-RO): preliminary performance data and
microbiological aspects of system operation. Desalination, 116(1),
65–80.
Sadr Ghayeni, S.B., Madaeni, S.S., Fane, A.G., and Schneider, R.P. (1996).
Aspects of microfiltration and reverse osmosis in municipal wastewater
reuse. Desalination, 106(1–3), 25–29.
Schmid, L.A. and McKinney, R.E. (1969). Phosphate removal by a lime-
biological treatment scheme. Journal of the Water Pollution Control
Federation, 41(7), 1259.
Schnepf, R.W., Gaden, E.L., Mirocznik, E.Y., and Schonfield, E. (1959).
Foam fractionation: metals. Chemical Engineering Progress, 55, 42–46.
Schoen, H.M. and Mazella, G. (1961). Foam separation. Industrial Water
Wastes, 6, 71–74.
Schoen, H.M., Rubid, E., and Ghosh, D. (1962). Radium removal from ura-
nium mill wastewater. Journal of the Water Pollution Control Federa-
tion, 34(10), 1026.
Shatto, J. (1960). Aerobic digestion and diatomite filter. Public Works,
December, 82.

Shin, H S., Kim, Y R., Han, B., Makarov, I.E., Ponomarev, A.V., and
Pikaev, A.K. (2002). Application of electron beam to treatment of
wastewater from papermill. Radiation Physics and Chemistry, 65(4–5),
539–547.
Shuckrow, A. (1971). Battelle’s northwest laboratories. American Society of
Civil Engineers Newsletter, August, 4.
Slechta, A.F. and Culp, G.L. (1967). Water reclamation studies at the South
Tahoe Public Utility District. Journal of the Water Pollution Control
Federation, 39(5), 787.
Sridhar, S., Prasad, K.K., Murthy, G.S., Rao, A.G., and Khan, A.A.
(2003). Processing of composite industrial effluent by reverse osmo-
sis. Journal of Chemical Technology and Biotechnology, 78(10),
1061–1067.
Stander, G.J. and Van Vuuren, L.R.J. (1969). The reclamation of potable
water from wastewater. Journal of the Water Pollution Control Federa-
tion, 41(3), 355.
Steel, E.W. (1960). Water Supply and Sewerage. McGraw-Hill Book Com-
pany, New York.
Stevens, D.B. and Peters, J. (1966). Long Island recharge studies. Journal of
the Water Pollution Control Federation, 38(12), 2009.
Stevik, T.K., Kari, A., Ausland, G., and Hanssen, J.F. (2004). Retention
and removal of pathogenic bacteria in wastewater percolating through
porous media: a review. Water Research, 38(6), 1355–1367.
Stumm, W. and Morgan, J.J. (1970). Aquatic Chemistry. John Wiley and
Sons, New York.
Tabrizi, G.B. and Mehrvar, M. (2004). Integration of advanced oxidation
technologies and biological processes: recent developments, trends,
and advances. Journal of Environmental Science and Health, Part
A—Toxic/Hazardous Substances and Environmental Engineering,
A39(11–12), 3029–3081.

Tchobanoglous, G., Burton, F.L., and Stensel, H.D. (2003). Wastewater
Engineering, Treatment and Reuse (4th ed.). McGraw-Hill Book Com-
pany, New York.
Tchobanoglous, G. and Eliassen, R. (1970). Filtration of treated sewage
effluent. Journal of the Sanitary Engineering Division, American Soci-
ety of Civil Engineers, 96(4) (SA2), 243.
Truesdale, G.A. and Birkbeck, A.E. (1966). Tertiary treatment processes for
sewage works effluents. Paper presented to the Scottish Center of the
Institution of Public Health Engineers, March 28.
Unpublished proposal to Clark County Sanitation District, prepared by
Pacific Engineering and Production Co., Henderson, Nevada, 1970.
Vaca Mier, M., Lopez Callejas, R., Gehr, R., Jiménez Cisneros, B.E., and
Álvarez, P.J.J. (2001). Heavy metal removal with Mexican clino-
ptilolite: multi-component ionic exchange. Water Research, 35(2),
373–378.
Vajnhandl, S. and Majcen Le Marechal, A. (2005). Ultrasound in textile
dyeing and the decolouration/mineralization of textile dyes. Dyes and
Pigments, 65(2), 89–101.
Van Hulle, S.W.H. and Vanrolleghem, P.A. (2004). Modelling and optimi-
sation of a chemical industry wastewater treatment plant subjected to
varying production schedules. Journal of Chemical Technology and
Biotechnology, 79(10), 1084–1091.
Villiers, R.V., Berg, E.L., Brunner, C.A., and Masse, A.N. (1971). Munici-
pal wastewater treatment by physical and chemical methods. Water and
Sewage Works, 118(8), R62.
Vogna, D., Marotta, R., Napolitano, A., Andreozzi, R., and d’Ischia, M.
(2004). Advanced oxidation of the pharmaceutical drug diclofenac with
UV/H
2
O

2
and ozone. Water Research, 38(2), 414–422.
Waite, T.D. (2002). Challenges and opportunities in the use of iron in water
and wastewater treatment. Reviews in Environmental Science and Bio-
technology, 1(1), 9–15.
Wall, A.E. (1980). Economically removed toxics. Water and Wastes Engi-
neering, 17(2), 43.
Weber, W.J., Hopkins, C.B., and Bloom, R. (1970). Physico-chemical treat-
ment of wastewater. Journal of the Water Pollution Control Federation,
42(1), 83.
Weber, W.J., Jr. (1967). Fluid-carbon columns for sorption of persistent
organic pollutants. Advances in Water Pollution Control Research.
Proceedings of the Third International Conference on Water Pollu-
tion Research, Washington, DC, Water Pollution Control Federation,
1, 253.
Wuhrmann, K. (1968). Objectives technology and results of nitrogen and
phosphorus removal processes. Advances in Water Quality Improvement,
University of Texas Press, Austin.
Wukash, R.F. (1968). New phosphate removal process. Water and Wastes
Engineering, 5(9), 58.
C016_005_r03.indd 988 11/22/2005 11:25:22 AM
© 2006 by Taylor & Francis Group, LLC
PHYSICAL AND CHEMICAL TREATMENT OF WASTEWATERS 989
Wyffels, S., Boeckx, P., Pynaert, K., Verstraete, W., and Cleemput, O.V.
(2003). Sustained nitrite accumulation in a membrane-assisted biore-
actor (MBR) for the treatment of ammonium-rich wastewater. Jour-
nal of Chemical Technology and Biotechnology, 78(4), 412–419.
Yildiz, E., Keskinler, B., Pekdemir, T., Akay, G., and Nuhoglu, A. (2005).
High strength wastewater treatment in a jet loop membrane bioreactor:
kinetics and performance evaluation. Chemical Engineering Science,

60(4), 1103–1116.
Yoon, T.I., Lee, H.S., and Kim, C.G. (2004). Comparison of pilot scale
performances between membrane bioreactor and hybrid conventional
wastewater treatment systems. Journal of Membrane Science, 242(1–2),
5–12.
Yuan, W.L. and Hsu, P.H. (1970). Effect of foreign components of the precipi-
tation of phosphate by aluminum. Paper presented at the 5th International
Water Pollution Conference, July–August.
Zuckerman, M.M. and Molof, A.H. (1970). High quality reuse water by
chemical-physical wastewater treatment. Journal of the Water Pollution
Control Federation, 42(3), 437.
ALESSANDRO ANZALONE
Polytechnic University of Puerto Rico
J.K. BEWTRA
University of Windsor
HAMBDY I. ALI
Ain Shams University
C016_005_r03.indd 989 11/22/2005 11:25:22 AM
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