The behavior of humic substance in iron electrolysis process and its influence on phosphorus removal

VIETNAM NATIONAL UNIVERSITY, HANOI
VIETNAM JAPAN UNIVERSITY

HA THI DIEP ANH

THE BEHAVIOR OF HUMIC
SUBSTANCE IN IRON ELECTROLYSIS
PROCESS AND ITS INFLUENCE ON
PHOSPHORUS REMOVAL

MASTER'S THESIS


VIETNAM NATIONAL UNIVERSITY, HANOI
VIETNAM JAPAN UNIVERSITY

HA THI DIEP ANH

THE BEHAVIOR OF HUMIC
SUBSTANCE IN IRON ELECTROLYSIS
PROCESS AND ITS INFLUENCE ON
PHOSPHORUS REMOVAL

MAJOR: ENVIRONMENTAL ENGINEERING
CODE: 8520320.01

RESEARCH SUPERVISOR:
Prof. Dr. JUN NAKAJIMA
Associate Prof. Dr. LE VAN CHIEU

Hanoi, 2020

ACKNOWLEDGMENT
First and foremost, I would like to sincerely thank my instructor, Prof. Jun
Nakajima for helping and always encouraging me, because of his patience,
motivation, and immense knowledge. His generosity and devoted guidance
contributed greatly to my dissertation completion and developed myself. There is no
unmatched honor to work with him.
Second, I would like to thank my co-supervisor, Associate Prof. Dr. Le Van
Chieu a lot because of his thoughtfulness and kindness. He is always enthusiastic
about reading and revising my research carefully.
Third, I would like to express my sincere thanks to all MEE Department for
your valuable support in the process of implementing the thesis as well as my stay at
VJU. And I would also like to thank JICA for its support. Thanks for all that we have
been through together.
I would like to express my appreciation to all Ritsumeikan University
professors, staff, and doctors, for their warm and enthusiastic welcome during my
internship. They gave me access to labs and research facilities. Without their valuable
support, it would not be possible to do this research.
Finally, I would like to thank my family and friends who have supported me
spiritually throughout the process of writing this thesis in particular, and my life in
general.
Hanoi, August 7th, 2020

Ha Thi Diep Anh

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TABLE OF CONTENT

ACKNOWLEDGMENT........................................................................................... i
INTRODUCTION .....................................................................................................1
1. Background .............................................................................................................1
2. Objectives ................................................................................................................3
3. Structure of thesis ....................................................................................................5
CHAPTER 1. LITERATURE REVIEW ................................................................7
1.1. Phosphorus removal technologies ........................................................................7
1.1.1. Phosphorus (P) pollution. ..................................................................................7
1.1.2. Phosphorus removal technologies. ....................................................................8
1.2. Electrocoagulation/Iron electrolysis. .................................................................15
1.2.1. Definition. .......................................................................................................16
1.2.2. Advantages and drawbacks of EC ..................................................................17
1.2.3. The principle of electrocoagulation ................................................................18
1.3.4. Application of EC ...........................................................................................19
1.3. Iron electrolysis application for phosphorus removal in Johkasou systems. .....19
1.3.1. Johkasou systems for decentralized domestic wastewater treatment. ............19
1.3.2. Phosphorus removal in Johkasou and application of iron electrolysis ...........20
1.3.3. Interference of phosphorus removal using iron electrolysis. ..........................23
1.4. Humic substance. ...............................................................................................24
1.4.1. General description .........................................................................................24
1.4.2. Chemical characteristic ...................................................................................26
CHAPTER 2. MATERIALS AND METHODOLOGY ......................................28
2.1. Materials .............................................................................................................28
2.1.1. Synthetic test liquor (phosphate solution) .......................................................28
2.1.2. Humic substance sample liquor. .....................................................................28
2.1.3. Humic acid sample liquor ...............................................................................29
2.2. Iron electrolysis experiment set-up. ...................................................................30
2.3. Operational condition of experiment. ................................................................31
2.3.1. Iron electrolysis with or without oxygen supply. ............................................31
2.3.2. Iron electrolysis with HS addition ..................................................................32

2.3.3. Iron electrolysis with humic acid addition. .....................................................33
2.4. Chemical analysis...............................................................................................34
2.4.1. Suspended solid (SS).......................................................................................34
2.4.2. Iron analysis. ...................................................................................................35
2.4.3. Phosphorus analysis. (PO4-P)..........................................................................36
2.5. Fluorescence spectroscopy analyses by three-dimensional excitation-emission
matrix. .......................................................................................................................36
CHAPTER 3. RESULTS AND DISCUSSION .....................................................38
3.1. Iron electrolysis without oxygen supply. ...........................................................38
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3.1.1. Iron electrolysis with aeration. ........................................................................38
3.1.2. Iron electrolysis without aeration. ...................................................................39
3.1.3. Discussion .......................................................................................................41
3.2. The effect of humic substance on iron electrolysis ............................................43
3.2.1. Iron coagulation decrease by humic substance addition .................................43
3.2.2. Decrease of phosphorus insolubilization by iron coagulation decrease .........44
3.2.3. Discussion. ......................................................................................................45
3.3. The effect of fulvic acid to iron electrolysis ......................................................47
3.3.1. Iron electrolysis with humic acid addition ......................................................47
3.3.3. Discussion .......................................................................................................50
CONCLUSION ........................................................................................................52
REFERENCES ........................................................................................................53

iii


LIST OF TABLES
Table 1.1. Vietnam national technical regulations on effluent discharge ..................7

Table 2.1. Preparation of synthetic test liquor..........................................................28
Table 2.2. Operational experiment condition. ..........................................................32
Table 2.3. Preparation chemicals to iron analysis ....................................................35
Table 2.4. Preparation chemicals to phosphorus analysis ........................................36
Table 3.1. Effluent parameters after electrolysis performed in aeration condition ..38
Table 3.2. Effluent parameters after electrolysis performed in humic substance
addition experiment ...................................................................................................43
Table 3.3. Effluent parameters after electrolysis performed in humic acid addition
experiment .................................................................................................................47

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LIST OF FIGUREURES
Figure 1. Iron electrolysis reactor (Fayad, N. (n.d.)., 2017) .....................................2
Figure 2. Structure of thesis ......................................................................................6
Figure 1.1. Changes in structure of phosphorus compounds in municipal wastewater
between year 1971 and 1991 (Rybicki, n.d.). .............................................................9
Figure 1.2. Phosphorus removal technologies ..........................................................9
Figure 1.3. One – point chemical addition .............................................................. 10
Figure 1.4. Two – point chemical addition.............................................................. 10
Figure 1.5. Metabolic pathway of PAO under aerobic and anaerobic conditions
(Bunce et al., 2018) ...................................................................................................14
Figure 1.6. Iron electrolysis principle ......................................................................18
Figure 1.7. Combination process of BOD and nitrogen removal type Johkasou and
phosphorus adsorption column (Ebie et al., 2008)....................................................22
Figure 1.8. Johkasou for phosphorus – BOD – Nitrogen removal. (Kumokawa, n.d.)
...................................................................................................................................23
Figure 1.9. Hypothetical humic acid structure according to Stevenson (1982) .......26
Figure 1.10. The hypothetical model structure of fulvic acid (Buffle's model) .......26

Figure 1.11. Chelation of Cu and Zn in top 2 examples with simple complexation of
Zn by an amino acid (Hd, n.d.). ................................................................................27
Figure 2.1. The map of Hanoi and Nam Son landfill ...............................................29
Figure 2.2. Humic acid, Nacalai Tesque, Japan. ......................................................29
Figure 2.3. Schematic diagram of the laboratory-scale experiment. .......................30
Figure 2.4. The types of equipment used to set-up experiments ..............................30
Figure 2.5. Synthetic test wastewater preparation ...................................................31
Figure 2.6. Set – up experiments ..............................................................................32
Figure 2.7. Humic substance experiment set-up. .....................................................33
Figure 2.8. Humic acids addition experiment set-up ...............................................34
Figure 2.9. Procedure iron calculate. .......................................................................34
Figure 2. 10. Fluorescence Spectrophotometer F-7000 (Hitachi, Tokyo, Japan) ....37
Figure 3.1. Phosphorus insolubilization ...................................................................39
Figure 3.2. Iron coagulation .......... ………………………………………………..39
Figure 3.3. Iron coagulation (without aeration) .......................................................39
Figure 3.3. Iron coagulation (without aeration) .......................................................39
Figure 3.4. Iron coagulation (N2 gas bubbling)........................................................39
Figure 3.5. Iron coagulation under aerobic condition (a) and anaerobic condition
(b)…………………………………………………………………………………..37
Figure 3.6. Phosphorus insolubilization (without aeration)………………………..41
Figure 3.7. Phosphorus insolubilization (N2 gas bubbling) ....................................41
Figure 3.8. The existing pathway models. ...............................................................41
Figure 3.9. The new pathway model including ferrous compound coagulation ......42
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Figure 3.10. Iron coagulation (Humic substance addition) ......................................44
Figure 3.11. Phosphorus insolubilization (HS addition) ..........................................45
Figure 3.12. Molar ratio of ΔFe / ΔP .......................................................................46
Figure 3.13. Soluble complex formation of ferrous ion and HS ..............................47

Figure 3.14. Iron coagulation (Humic acid addition) ...............................................48
Figure 3.15. Phosphorus insolubilization (HA addition) .........................................49
Figure 3.16. EEMs Fluorescence spectra of humic substance sample (leachate
sample) ......................................................................................................................49
Figure 3.17. EEMs Fluorescence spectra of humic acid sample. ...........................50
Figure 3.18. The effect of fulvic acid on iron electrolysis. ......................................51

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LIST OF ABBREVIATIONS
BOD

Biochemical oxygen demand

DC

Direct current

DOC

Dissolved organic carbon

EBPR

Enhanced biological phosphorus removal

EC

Electrocoagulation

EEM

Excitation emission matrix

FDOM

Fluorescent dissolved organic matter

HA

Humic acid

HS

Humic substance

MBR

Membrane bioreactor

PAO

Phosphorus accumulation organisms

SBR

Small-scale wastewater treatment plants

SWTPs

Sequencing batch reactor

SS

Suspended solids

TDS

Total dissolved solid

WWTP

Wastewater treatment plant

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INTRODUCTION
1. Background
Some serious environmental problems such as eutrophication are due to the
direct discharge of phosphorus into the water source. The abundance of these
nutrients will spur the development of algae, mosses, and mollusks in the water and
will ultimately affect the biological balance of water. In addition, phosphorus is also
a limited resource, so we need to remove and recover P effectively from wastewater
before discharging it into the water source.
In order to remove phosphorus from wastewater sources, there are several
methods being applied, including adsorption, chemical precipitation (using metal
salts), biological processes, and ion-exchange methods ion (Omwene et al., 2018).
Among the methods in the two most used methods are chemical precipitation and

biological processes. Chemical precipitation and adsorption are currently the best
methods for efficiency. By adding metal salts (aluminum salts or iron salts) most of
the phosphorus is removed. Biological methods can also eliminate up to 90% of total
phosphorus but this method is only suitable for wastewater with low phosphorus
concentrations. And when there is a change in the chemical composition, high
phosphorus concentration, and changes in the temperature of the wastewater, the
treatment efficiency is not high. Moreover, many of the above methods have long
operating times, eliminating ineffective and costly (Wysocka and Sokolowska, 2016).
Therefore, electrocoagulation (EC) to remove phosphorus has been used as an
alternative process (especially chemical precipitation). Electrochemical (electrolysis
+ coagulation) combining coagulation, flotation, and electrolysis is a process of
destabilizing suspended pollutants or dissolving in water environments using electric
current (Fayad, N. (n.d.)., 2017).
Distinct mechanisms are involved in the removal of the various types of
contaminants that exits in water and wastewater which include oxidation, reduction,
coagulation, flotation, adsorption, precipitation, and others (Fayad, N. (n.d.)., 2017)
said that: “As pollutants in raw water and wastewater are mostly colloidal particles,

1


their removal is mainly accomplished by destabilization and adsorption”.
Coagulation is a traditional physicochemical treatment via phase separation for the
decontamination of wastewaters before discharge to the environment. EC is causally
related to the conventional coagulation process, which has been used as a method for
water clarification and stabilization, and nowadays, it is still extensively used
(Garcia-Segura et al., 2017).
Moreover, this technique has the advantages to be able to overcome the
drawbacks of the above methods such as simple equipment, easy operation, and only
use electric current so there is no need to add chemicals and reduce time retention

time, settling speed is also faster and creates less sludge (Moussa et al., 2017).
In addition, the EC does not use chemicals, so it does not raise water or aquatic
organisms. The EC only uses electricity for operation without adding any chemical,
so it is suitable for domestic scale facilities. EC applied in small-scale wastewater
treatment Johkasou (domestic, small-scale, on-site, decentralized) (Fayad, N. (n.d.).,
2017).
EC can be applied to treat wastewater containing heavy metals, organic
substances, and other ions such as PO43- and AsO2-, ...
EC reactor is composed of an electrolytic cell and connected externally to a
direct current power supply.

Figure 1. Iron electrolysis reactor (Fayad, N. (n.d.)., 2017)
Mechanism of phosphorus removal by electrolysis method: By directing
electric current through a pair of iron electrodes immersed in water. At the Anode
electrode oxidation occurs, iron is oxidized into Fe2+ ions and dissolved into solution.

2


This Fe2+ ion will be oxidized with dissolved oxygen in the water to trivalent iron ion
(Fe3+). Fe3+ will combine with PO43- in water to form a precipitate and settle to the
bottom of the device (Morrizumi et al., 1999). This precipitate can be removed by
pumping out of the system or by using the flotation method to remove the sludge.
EC has been applied to industrial wastewater treatment plants or small
wastewater treatment models. The small-scale wastewater treatment plants (SWTPs)
are called Johkasou and this model treats domestic wastewater on-site for about 10
households, so it is widely applied in Japan. But it is difficult to remove phosphorus
by the activated sludge method because it is dependent on the input parameters.
Therefore iron-electrolysis was developed and used in this model to remove
phosphorus more effectively. According to previous studies, it has achieved good

performance although some examples showed a slightly lower phosphorus removal
(Mishima et al., 2017).
A study on the effects of calcium in increasing phosphorus removal efficiency
has been conducted and results of countermeasures have been reported.
In addition, testing of such cases shows that the DOC (humic substances are
imported from sewage or produced in Johkasou tanks), causing low performance.
Regarding the effect of humic substances, a hypothesis has been obtained that it forms
a chelate compound with iron ions provided by iron electrolysis (Mishima et al.,
2018).
Testing to verify this idea has been started but has not ended. Previous research
using EDTA, a typical chelate-making material, shows the potential for interfering
with phosphorus removal by forming a chelate with supplied iron. The mechanism of
the effects of humic compounds on phosphorus removal is still unclear, especially the
sequencing batch reactor activated sludge processes, which are still poorly
understood. Next, a test using humic substances is needed to clarify this mechanism
of intervention.
2. Objectives
With the high potential in the handling and wide application mentioned above,
EC has been widely applied in phosphorus removal for domestic scale wastewater

3


treatment Johkasou. However, there are still problems remain that affecting the
removal of phosphorus. There have been many previous studies on factors affecting
the phosphorus removal process, such as the influence of electric current, the effect
of initial pH, the effect of initial phosphorus concentration. No research has been
done to study influence the DOC co-substance or co-ions present in wastewater on
phosphorus removal. It is very necessary to improve this method to clear the
interference problem. Because in real sewage not only phosphorus but also many

other compounds such as DOC coexist under some condition. It may increase or
decrease processing efficiency.
Therefore, the action of phosphorus, iron, and organic substances coexisting
in wastewater must be thoroughly investigated to clarify the factors that influence the
phosphorus removal process. Moreover, it is also necessary to determine the optimal
and stable reaction conditions in the actual model.
Based on this study focused on investigating the impact of a high molecular
organic compound capable of complexing with Fe, particularly humic substance
(HS). However, humic substances including humic acid (HA), fulvic acid, and humin,
can also affect the removal of phosphorus by electrolysis of iron. Therefore, in this
study, the effect of HA is the main object of study, by adding HA to the electrolysis
process and conducting related analyzes to evaluate the effect. This study focuses on
clarifying the mechanism of the phenomenon occurring during electrolysis under the
presence of HS and developing a model describing this process.
To achieve the above objective, I operated a laboratory scale batch
experiments with simulated wastewater and prepared HA (commercial humic acid or
humic acid from humic substance sample) was operated.
Summary of research object and scope:
Research question:
(1) What is mechanism of DOC interference to phosphorus removal in iron
electrolysis process used in Johkasou?

4


(2) What is main DOC factor that interferes phosphorus removal in iron
electrolysis process?
Research objective:
(1) To clear the mechanism of phenomena occurring in iron electrolysis
process under the condition of abundant of DOC.

(2) To clarify specific factor in DOC that interferes phosphorus removal in
iron electrolysis process used in Johkasou.
3. Structure of thesis
The structure of this thesis is shown in the Figure 2. This thesis contains of 3
chapters. The main content of each chapter is presented as follows:
Introduction: Introduction Briefly summarize the foundational knowledge
causally related to the research and identify the main research subjects and tasks.
Chapter 1: Literature review provide background knowledge of phosphorus
pollution and its consequences, history of phosphorus removal technologies. Focus
on EC's role in phosphorus removal.
Chapter 2: Material and Methodology Describe materials, equipment, and
methods used in the study. Detailed description set-up experiments. Analytical
methods as well as equipment were also introduced.
Chapter 3: Results and discussion
3.1. Iron electrolysis without oxygen supply.
3.2. The effect of Humic substance to iron electrolysis.
3.3. The effect of Fulvic acid to ion electrolysis
Conclusion.

5


Introduction
Briefly summarize the foundational knowledge

Chapter 3: Results and discussion.

causally related to the research and identify the
main research subjects and tasks.

3.1. Iron electrolysis without oxygen

Chapter 1: Literature review

supply.

Provide

background

knowledge

3.2. The effect of Humic substance

of

to iron electrolysis.

phosphorus pollution and its consequences,
history of phosphorus removal technologies.

3.3. The effect of Fulvic

Chapter 2: Material and methodology
Describe materials, equipment, and methods

Conclusion

used in the study. Detailed description Set-up
experiments. Analytical methods as well as

equipment were also introduced.

Figure 2. Structure of thesis

6


CHAPTER 1: LITERATURE REVIEW
1.1. Phosphorus removal technologies
1.1.1. Phosphorus (P) pollution.
Phosphorus and nitrogen are crucial nutrient that extremely needed for growth
of plant and animals (Yan et al., 2015). In addition, phosphorus plays an important
role in several industries (e.g. fertilizers, detergents, paint ...). Increasing input of
nitrogen and phosphorus compounds to receiving surface waters, especially to lakes
and artificial reservoirs lead to increase of primary production of water born
organisms and finally its consequence is lack of oxygen in waters. The removal of
phosphorus from domestic wastewater is primarily to reduce the potential for
eutrophication (Dunne et al., 2015).
The excessive amounts of phosphorus in the aquatic environment due to
human activity can negatively affect aquatic ecosystems. Therefore, several technical
standards for the quality of wastewater effluent have been made public to control
phosphorus pollution.
To minimize surface water pollution and to control pollution sources, each
country has issued its own standards on effluent standards. The following are some
of Vietnam's effluent discharge standards that specify a limit for phosphorus
effluence.
Table 1.1. Vietnam national technical regulations on effluent discharge for
Phosphorus.
No.

Regulations

Unit

Maximum value allowed

QCVN 40:2011/BTNMT
1.

National

technical

regulation

on mg/L

4-6

Industrial wastewater

2.

QCVN 11-MT:2015/BTNMT

mg/L

7

10 - 20

National technical regulation on the
effluent of aquatic Products Processing
industry

QCVN 14-MT:2015/BTNMT
3.

National technical regulation on domestic mg/L
wastewater

6 - 15

QCVN 08-MT:2015/BTNMT
4.

National technical regulation on surface mg/L
water quality

– 0.5

1.1.2. Phosphorus removal technologies.
Phosphorus enters water derived from urban sewage, chemical fertilizers,
washed away from the soil, rainwater, or phosphorus sediments dissolved again.
Phosphorus in water usually exists in the form of orthophosphate (PO43-, HPO42-,
H2PO4-, H3PO4) or polyphosphates [Na3(PO3)6] and organic phosphates.
Phosphorus exists in wastewater soluble form. That is why most of the applied
methods based on a general principle of converting phosphorus compounds from
soluble to insoluble. The basic principle for removing phosphorus in water is to

convert phosphorus from soluble form to insoluble form by precipitating with ions of
aluminum, iron, calcium, or forming biomass by chemical methods. There are many
methods of handling phosphorus but can be classified into two main groups: physicalchemical method and biological method.
Comparison between year 1971 and year 1991 is shown in Figure 1.1 below.
(Jenkins Ferguson Menar 1971, Sedlak 1991). It is visible how concentration
decreases and the structure changes in time.

8


Figure 1.1. Changes in structure of phosphorus compounds in municipal
wastewater between year 1971 and 1991 (Rybicki, S. M. (n.d.)., 2004).
Phosphorus removal technologies

Physical – chemical

Electrolytical Crystallization
method

Magnetic

Biological

Adsorption

Precipitation

separation

Enhanced biological P

Constructed

removal (EBPR)

wetland (CW)

Figure 1.2. Phosphorus removal technologies
Physical-chemical technologies.
Physical and chemical processes have been applied to remove and control
phosphorus for many years. This method clearly shows the processing efficiency, but
they still have some limitations. Physical-chemical treatment of phosphorus removal
involves the addition of trivalent metal salts to react with dissolved phosphates and
remove by sedimentation or filtration. Metal salts are commonly used in the form of

9


alum and the most common is salt of iron or aluminum. Depending on the dosage
point, this method can be used in various technology schemes (Graziani et al., 2006):
• primary precipitation in mechanical wastewater treatment plants (older
constructions).
• primary precipitation before further biological treatment.
• simultaneous precipitation (adding chemicals to final zones of activated
sludge reactor).
• final precipitation.
Because the amount of precipitate produced is causally related to the amount
of phosphorus removed, hence study to find the quantitative optimization point is
extremely important in chemical treatment. Contact filtration is also a widely
integrated method with physical-chemical methods to ensure a stable phosphorus

output. Investigations on other physical-chemical methods containing many
processes most will be described in the following processes:
• Electrolytical method
• Precipitation
• Crystallization
• Magnetic separation
• Adsorption
Electrolytical method.
Electricity has been used for water treatment for a long time, around the 1860s
electricity was used to treat sewage in England. Development of the direct use of
electricity for treatment is carried out in subsequent years. The basic principle of the
process is that the chemical precipitation of iron compounds is formed on an
electrode. Operation of the plant showed positive results. In the following years, the
technology continued to be researched and developed, and until 1950 the first
experiments on electrolyte treatment were directed at removing nutrients. During this
process, the phosphorus content was reduced to 1.0 mgP/L.
Further findings were reported by Groterud i Smoczynski in 1991, who
experimented with two electrodes:

10


• Aluminum electrode for phosphorus removal.
• Carbon electrodes for electrochemical.
For decades, this technology has been increasingly used to treat industrial
wastewater containing metals. It is also used to treat pulp and paper industry
wastewater, metal processing, and mining. EC is also applied to treat many types of
wastewater containing food waste, dyes, organic matter from leachate. Studies are
often carried out on the EC to optimize key operational parameters such as amperage,
effluent flux (Fayad, N. (n.d.)., 2017).

Precipitation
Chemical methods have been widely used in phosphorus removal. This
method removes phosphorus by adding metal salts to the wastewater so that it reacts
with the phosphorus in a soluble form. The produced precipitate will then be removed
by sedimentation or filtration. The most used metal salts are trivalent metal salts (iron,
aluminum): aluminum sulfate, ferric chloride, ferric sulfate, ferrous sulfate, and
ferrous chloride. These chemicals combine with phosphorus as shown by the
following reactions (Graziani et al., 2006).
Al3+ + PO43- → AlPO4↓
Fe3+ + PO43-→ FePO4↓
Depending on the design of each specific treatment plant, the chemical
addition point is designed differently. But there are two main scenarios for chemical
additions:
Effluent polishing in the secondary process. Chemicals added right before the
secondary settling tanks
Two – point chemical addition. Chemicals are added in both primary and
secondary settling tanks. This design is widely applied because of its good
phosphorus removal effect.

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Influent

Influent

Primary
clarifier

Primary

clarifier

Return
Activated
Sludge (RAS)

Waste
Activated
Sludge
(WAS)

Return Activated
Sludge (RAS)
Aeration
tank

Aeration tank

Chemical
addition

Secondary
clarifier

Waste Activated
Sludge (WAS)

Secondary
clarifier

Effluent

Effluent

Figure 1.3. One – point chemical addition

Chemical
addition

Figure 1.4. Two – point chemical addition

Crystallization
This method has been developed and applied for phosphorus removal since
the 1980s. This method was specifically presented by Joko, who showed the longterm operation of the installation to remove phosphorus. The phosphorus from
wastewater is biologically treated by crystallizing hydroxyapathyte Ca5(OH)(PO4)3.
This method also shows relatively good handling efficiency. Joko completed
tests on Yamato (Japan) WWTP, which confirmed the decrease of P level from 1-4
mgP/L in biologically treated wastewater down to 0.3 - 1.0 mgP/L after
crystallization.
This method has the advantage that the product after crystallization can be
used for fertilizer production, but this method is not widely applied because it is quite
complex and high processing cost (Rybicki, S. M. (n.d.)., 2004)
Magnetic separation.
In the 1970s, magnetic separation technology was investigated by De Latour
and reported that it was an effective method if applied after adding iron or aluminum
salts. This method can remove most of the phosphorus in the water, the amount of

12

phosphorus in the output can reach 0.1 - 0.5mgP/L compared to other methods with
equivalent costs (Velsen et al.1991).
The principle of this method is to separate particles that are removed by a
magnetic field. Therefore, it can remove all impurities
Adsorption
Around the 1970s there were trials of phosphorus adsorption using fly ash.
The phosphorus in the wastewater will be attracted to the molecular binding force
and trapped on the adsorbent surface. This method is widely used for both high and
low concentrations of phosphorus (Rybicki, S. M. (n.d.)., 2004)
Adsorbents are the most important factor affecting phosphorus removal
efficiency. In the past, activated carbon was the most widely used adsorbent, but it
also revealed some disadvantages such as regeneration and high cost. Therefore, a lot
of research has been done to reduce the production costs of these adsorbents, and
there are several solutions that are proposed to use by-products in agriculture and
industry.
Biological technologies.
Biological methods for handling phosphorus have been studied and applied
for a long time. This method is associated with the use of activated sludge to remove
pollutants in the water environment, which proved to be quite effective with organic
pollutants. Current biological methods are developing in two directions:
• Optimizing wastewater treatment plants using activated sludge technology.
• Dealing with pollutants by constructed wetlands
Enhanced biological phosphorus removal (EBPR)
Although activated sludge has been used in wastewater treatment for a long
time, this technology still reveals the disadvantages that need to be overcome such as
the treatment efficiency is still unstable, especially the effectiveness of the treatment
of substances. nutrition (nitrogen, phosphorus) and highly dependent on operational

13

skills, making it difficult to control the process (Seviour et al., 2003). This is a
technological barrier when applied to decentralized treatment facilities (Brown and
Shilton, 2014). However, the understanding of biochemical mechanisms involved in
P uptake is increasing. The phosphorus uptake process is dependent on phosphorus
accumulation organisms (PAO) for EBPR. The application of this method is subject
to strict operating conditions for carbon source, glycogen, and electron acceptor.
When good operating conditions can be assured, 80% of the phosphorus can be
removed from the wastewater by this method (Bunce et al., 2018)

Figure 1.5. Metabolic pathway of PAO under aerobic and anaerobic
conditions (Bunce et al., 2018)
This method can be used in different designs for each type of wastewater plant.
Recent EBPR applications include a combination of a membrane bioreactor (MBR),
a sequencing batch reactor (SBR), and an activated sludge reactor. This combination
has been shown to be effective in removing phosphorus from municipal sewage,
particularly the MBR proving highly effective in capturing suspended solids in the
tank.
Constructed wetland
Using natural cycles to remove phosphorus is particularly suitable for small
communities and local systems because it is easy to operate and the cost is quite
cheap:
• Using activated algae: exposing algae culture environment to wastewater, can
remove 90% of phosphorus (Rybicki, S. M. (n.d.)., 2004).

14


• Using artificial and natural wetlands can apply treatment without the use of
chemicals.

An artificial wetland is an engineering system comprising of filter materials,
plants, and microorganisms. Phosphorus will be removed by decomposing
organisms, plants that absorb, settle, or adsorb on filter materials. Microorganisms in
the system also have the role of metabolizing phosphorus from the form of poorly
soluble organic to dissolved inorganic phosphorus which plants can easily to absorb
(Vymazal., 2007).
1.2. Electrocoagulation/Iron electrolysis.
Electrocoagulation (EC) is a technique that has been used and successfully for
treating various types of wastewater. The technology uses direct current between a
pair of metal electrodes submerged in water. Metal ions at the right pH will produce
precipitates and metal hydroxides. The resulting precipitate will destabilize and
synthesize particles or adsorb dissolved pollutants. This method was also started to
apply in the late 19th century:
1880: in US – first document on the use of EC for the treatment of effluents.
1880: in UK, WWTP apply this patent to treat sewage.
1930: due to high operating costs and replace by chemical coagulant.
1947: small size installations, EC is more competitive than conventional
process.
1970s- 1980s: that research on the application of EC for the treatment of
various types of wastewater has generated significant interest. The industrial
development of EC process was, however, hampered by the cost deemed too high
and by the competition of chemical treatment processes, without ruling out its us
(Fayad, N. (n.d.)., 2017)

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1.2.1. Definition.
Electrolysis process in which current is passed between 2 electrodes through
an ionized solution (electrolyte) to deposit positive ions on the negative electrode

(cathode) and negative ions on the positive electrode (anode) (Yousuf et al., 2001).
Electrolyte:
• positive ions → move to cathode (occurring oxidation process).
• negative ions → move to anode (occurring reduction process).
EC is a process of destabilizing suspended emulsified or dissolved
contaminants in an aqueous medium.
Connected externally to a direct current power supply (DC)
Electrochemical dissolution of the sacrificial anode (+)

Coagulating ions

Coagulant

Metallic
hydroxide

Various other ions
metal species

The dissociation of the ions from the anode follows Faraday s law

=

ì ì
ì

Where:
ã I: current (A)
ã t: time of operation (s)

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(g)