RESTORATION AND MANAGEMENT OF LAKES AND RESERVOIRS - CHAPTER 10 doc

10
Copper Sulfate
10.1 INTRODUCTION
Copper, an effective algicide, is registered for use in potable water supplies. Its effects are temporary
(days), annual treatment costs can be high, there are major negative impacts to non-target organisms,
and significant copper contamination of sediments is possible. Several U.S. states have started to
restrict or phase out copper use or to lower the permissible dose. The search for an alternative
algicide with fewer negative effects has been unsuccessful. Copper sulfate is also used in tank
mixes of herbicides to enhance macrophyte control (Chapter 16).
The purposes of this chapter are to describe copper sulfate’s dose and application procedures,
and to discuss its positive and negative effects. There are several reviews of copper use for algae
control (i.e., AWWARF, 1987; Cooke and Carlson, 1989; Demayo et al., 1982; McKnight et al.,
1981, 1983; Raman and Cook, 1988).
10.2 PRINCIPLE OF COPPER SULFATE APPLICATIONS
The primary toxic form of copper to algae is the cupric ion (Cu
2+
) (McKnight et al., 1981), although
other forms such as copper-hydroxy complexes may also be toxic (Erickson et al., 1996). Effects
on algae include inhibitions of photosynthesis, phosphorus (P) uptake, and nitrogen fixation
(Havens, 1994), but effects vary with algal species. Cyanobacteria are particularly sensitive, with
concentrations as low as 5–10 μg Cu/L suppressing activity (Demayo et al., 1982; Horne and
Goldman, 1974). Copper treatments are likely to be most effective in controlling blooms of nitrogen
fixing cyanobacteria, possibly through frequent low doses (Elder and Horne, 1978).
The activity of the cupric ion is affected by: (1) inorganic complexation, (2) precipitation
(Cu(OH)
2
CO
3
, CuO, CuS), (3) complexation with compounds such as humic and fulvic acids, (4)
adsorption on materials such as clays, and (5) biological uptake (McKnight, 1981; McKnight et
al., 1981, 1983; Fitzgerald, 1981). Effective doses therefore may vary among lakes.

pH has a significant effect on the appearance of the cupric form (Cu
2+
), requiring higher CuSO
4
doses in lakes with high alkalinity and pH (Figures 10.1 and 10.2). Copper is less toxic in hard
water, in part due to the precipitation of malachite (Cu(OH)
2
CO
3
) and to competition with calcium
and magnesium for binding sites on the algal cell membrane.
The experiments by Button et al. (1977) in Hoover Reservoir (alkalinity = 96 mg/L as CaCO
3
,
pH = 7.8), a water supply for Columbus, Ohio, illustrate the brief period of high Cu
2+
that can be
expected in a water body of this alkalinity. Cu
2 +
concentration in the water column fell rapidly
after the application of 1.56 g CuSO
4
⋅ 5H
2
O/m
2
. About 95% of the total CuSO
4
dissolved in the
top 1.75 m of the water column. At the end of 2 h, soluble Cu

2+
fell to pre-treatment levels (Figure
10.3), perhaps through precipitation, dilution by incoming water, or by washout. An algae bloom,
consisting of taste and odor causing diatoms Melosira sp., Asterionella sp. and Stephanodiscus sp.,
was controlled. Formation of insoluble malachite may have been responsible for a substantial
fraction of the loss of Cu
2+
because conditions for its formation were ideal (Button et al., 1977).
Complexation by dissolved humic substances in Mill Pond Reservoir, a Massachusetts water
supply with a high humic content, apparently prevented the rapid loss of copper to the lake’s bottom,
making the treatment more effective. Biomass of the taste and odor causing dinoflagellate, Ceratium
Copyright © 2005 by Taylor & Francis
FIGURE 10.1 Relationship between pH and concentration and forms of copper in high alkalinity water. (From
McKnight, D.M. et al. 1983. Environ. Manage. 7: 311–320. With permission.)
FIGURE 10.2 Relationship between pH and concentration and forms of copper in low alkalinity water. (From
McKnight, D.M. et al. 1983. Environ. Manage. 7: 311–320. With permission.)
− log Cu
T
4
5
6
7
5678910
pH
Cu
2+
CuCO
3
(aq.)
Malachite

Cu
2
(OH)
2
CO
3
(s)
Tenorite
CuO (s)
(CuCO
3
)
2
2−
− log Cu
T
4
5
6
7
5678910
pH
Cu
2+
CuCO
3
(aq.)
Malachite
Cu
2

(OH)
2
CO
3
(s)
Tenorite
CuO (s)
Cu(OH)
−
3
Copyright © 2005 by Taylor & Francis
hirundinella, was reduced by 90%, although the green algae Nanochloris and Ourococcus were
unaffected by the complexed copper and appeared to be copper tolerant (McKnight, 1981). In this
case, the dose of CuSO
4
saturated the organic complexing agent and still provided enough Cu
2+
to
control the dinoflagellate. Presumably, much higher doses would have been needed to control the
other species.
The effectiveness of copper has been enhanced by either complexing copper with a carrier
molecule, or by chelating it to non-metal ions, to keep copper in solution (DuBose et al., 1997).
These formulations allow effective treatment at lower doses.
Mat-forming filamentous algae can be pond and littoral zone nuisances, and doses to control
them vary widely. Using Cutrine-Plus (Applied Biochemists, Milwaukee, WI 53218, U.S.), an
ethanolamine–copper complex, Oedogonium and Spirogyra had a very low EC
50
of 3 μg Cu/L (dose
producing a 50% biomass reduction), but Hydrodictyon, Pithophora, and Rhizoclonium were 15
times more tolerant, and Oscillatoria was six times more tolerant than Pithophora (Lembi, 2000).

Field dose ranges could be wider than these laboratory doses, indicating the need for correct
identification of algae and for recognition that Pithophora, Oscillatoria, and Lyngbya form thick
mats or “scums” that may resist copper penetration.
10.3 APPLICATION GUIDELINES
Guidelines for CuSO
4
treatments for planktonic algae were developed by Mackenthun (1961).
However, reservoirs and lakes are sufficiently unique to require experience and judgment of the
applicator for the dose most likely to produce control. These are Mackenthun’s guidelines: For
lakes with a methyl orange alkalinity > 40 mg/L as CaCO
3
, the dose for planktonic algae is 1.0
mg CuSO
4
⋅ 5H
2
O/L, as copper sulfate crystals, for the upper 0.3 m depth regardless of actual
depth. In water with this alkalinity, 0.3 m is considered the maximum effective depth range, after
which copper is rapidly lost to complexation. If alkalinity is < 40 mg/L, the dose is 0.3 mg CuSO
4
5H
2
O/L. Copper sulfate is more effective at water temperatures > 15°C. Doses at these concentra-
tions will be toxic to many species of algae and to some non-target organisms (Nor, 1987). Control
of Chara and Nitella requires a dose of 1.5 mg/L, or higher, and must be applied early in the season
before these algae become encrusted with marl.
FIGURE 10.3 Depth of soluble copper penetration after application to Hoover Reservoir, OH. (From Button,
K.S. et al. 1977. Water Res. 11: 539–544. With permission.)
Cu
2+

mg/l
0.3
0.2
0.1
Surface
1 m
3 m
16 m
No sample
0 0.1 0.5 1.0 1.5 2.0 2.5 3.0 3.5
4.0
Time, hr
Copyright © 2005 by Taylor & Francis
Applicators may increase doses to compensate for copper sulfate ineffectiveness when water
column conditions promote complexation and precipitation. At a water column pH of 8.0, less than
10% of the added copper is in the dissolved form. Photosynthesis can drive pH up to 9 or above,
and copper effectiveness will be minimal. A chelated or complexed form may be needed in high
alkalinity waters (Raman and Cook, 1988).
Planktonic and filamentous algae are rarely controlled with a single application. The “guideline”
dose of 1.0 mg/L as CuSO
4
⋅ 5H
2
O for waters with alkalinity > 40 mg/L as CaCO
3
(Mackenthun,
1961: Fitzgerald, 1967) is often followed, but it appears that lower doses (e.g., 0.15 mg/L) at daily
intervals for 3–5 days could be more effective (DuBose et al., 1997). The problems with low doses,
however, are algal tolerance (McKnight et al., 1981; Twiss et al., 1993), the rapid loss of copper
via complexation, precipitation, or washout to concentrations that are too low, and the costs

associated with re-applications.
Treatment methods range from the traditional burlap bag of CuSO
4
towed behind a boat, to
mechanical spreaders, sprayers, and helicopters. Large quantities (e.g., 4,500 to 7,000 kg per day)
have been applied to water supply reservoirs, using barges and chemical spreaders (McGuire et al.,
1984) to treat taste and odor causing periphytic species of Oscillatoria. Copper can be added to a
reservoir’s inflow (Bean, 1957), or introduced near an artificial circulation device. Recreational
lake users may wait until an algal bloom develops before making application, an approach that
could be effective, although severe dissolved oxygen (DO) depletions are possible. Water supply
managers face the problem of preventing episodes of unacceptable tastes and odors, or the appear-
ance of a bloom of a toxic algal species. Some potable water supply operators monitor the algal
community on a frequent and regular basis during the summer and fall and treat the reservoir to
prevent a “bloom.” This may require several treatments. This approach emphasizes the need for
continuous and detailed monitoring of the water body.
10.4 EFFECTIVENESS OF COPPER SULFATE
The chemical and hydrological features of the treated water determine how rapidly copper will be
lost through precipitation, adsorption, washout, or dilution. There have been suggestions that some
algae species population have become resistant to low doses of copper, thus requiring either the
chelated or complexed forms, or a greater concentration, for effectiveness. These and other factors
are significant in the few published case histories about algae responses to copper.
The experimental treatments to periphytic blue-green algae in the highly buffered (alkalinity
150 mg/L as CaCO
3
) Casitas Reservoir, California are among the few published case histories
about control of these taste and odor producing algae (AWWARF, 1987). Several chelated and non-
chelated copper compounds were studied for effects on Oscillatoria limosa and other species of
this genus. Dry CuSO
4
crystals in chelated (ethanolamine) and non-chelated forms were applied to

surface waters over the periphyton mats, at doses from 0.2 to 0.3 mg Cu/L (chelated) and 0.4 to
1.7 mg Cu/L (non-chelated). Liquid copper citrate (chelated) and CuSO
4
solutions were applied
directly on the periphyton via a submerged hose, at 0.2 to 2.2 mg Cu/L and 0.2 to 1.0 mg Cu/L,
respectively. Divers were used to monitor results and water samples were obtained to determine
changes in taste and odor causing compounds.
The submerged applications of CuSO
4
and CuSO
4
citrate solutions at Casitas Reservoir had
little effect on periphyton. Applications of CuSO
4
at 1.7 mg Cu/L

to the lake’s surface, based on
an estimated volume of water near the periphyton growths, had some effect but produced significant
benthic invertebrate mortality. Application of chelated granular copper to the surface at doses of
0.2 to 0.4 mg Cu/L was effective at periphyton control, but regrowth was apparent in 4 weeks. This
formulation was toxic to benthic invertebrates and was the most costly treatment (Table 10.1).
Copper use was stopped at Casitas Reservoir due to environmental concerns.
Copper sulfate treatments of nuisance phytoplankton “blooms” frequently are successful for
brief periods. Species other than the target algae may become dominant, or algal biomass may
Copyright © 2005 by Taylor & Francis
“rebound” to levels similar to or higher than the original bloom condition. Copper sulfate is
unquestionably effective as long as the cupric ion concentration remains high, but water masses
are hydraulically dynamic, leading to washout, dilution, and reinoculation with algae, and chemical
and physical conditions may lead to loss of copper. In situations where eutrophication continues,
increasingly frequent and heavier doses may be needed (Hanson and Stefan, 1984).

Copper sulfate has been used to kill snails in bathing beach areas to limit the release of immature
(cercaria) forms of the blood flukes (Trematoda, Schistosomatidae) that penetrate human skin,
causing “swimmer’s itch.” Humans are not the normal host and the cercaria die in the skin, producing
severe itching. The Minnesota Department of Natural Resources (undated pamphlet) recommended
treating with 1.5 kg/100 m
2
out to the edge of the littoral zone. This dose is lethal to most
invertebrates and could produce sediment contamination.
10.5 NEGATIVE EFFECTS OF COPPER SULFATE
The benefits of copper sulfate treatments for algae control in recreational lakes should be weighed
against the exposure of non-target organisms to concentrations of a heavy metal greater than the
median lethal dose from laboratory studies. Copper sulfate negatively impacts aquatic communities,
and could create human health problems. Resistance may develop in target algae, and algae grazing
by zooplankton may be eliminated. Dissolved oxygen depletions can occur when large volumes of
dead algal cells decompose, creating conditions causing increases in iron, P, manganese, hydrogen
sulfide, and ammonia concentrations.
Laboratory test procedures for copper toxicity often involve exposure of the test organism for
96 h, a test period that may obscure effects. Copper is rapidly lost from solution, even with highly
simplified, possibly soft-water, experimental conditions, suggesting that 48-h exposures may be
more realistic in determining an LC
50
(concentration lethal to 50% of test organisms) (Mastin and
Rodgers, 2000).
Laboratory toxicity tests have demonstrated lethal and sublethal effects on bluegills (Lepomis
macrochirus). The 96-h LC
50
ranged from 1.0–3.0 mg Cu/L (Blaylock et al., 1985), to as high as 16.0
mg. Cu/L (Ellgaard and Guillot, 1988) in test waters of moderate alkalinity (46–82 mg/L as CaCO
3
).

However, locomotor activity was impaired at much lower concentrations (e.g., 40 μg Cu/L; Ellgaard
and Guillot, 1988). Hatchability and survival of 4-day old larvae were affected by concentrations
above 77 μg Cu/L (Benoit, 1975). The risk of direct bluegill mortality apparently is low, but sublethal
effects on behavior and reproduction, and on feeding behavior, could lead to reduced growth, and
occur at concentrations more than an order of magnitude less than recommended for algae treatment
(Sandheinrich and Atchison, 1989). Other species (e.g., trout) may be even more copper sensitive.
Does copper accumulation in lake sediments pose a bioaccumulation or toxicity risk? Anderson
et al. (2001) compared the hepatic concentrations of copper in largemouth bass (Micropterus salmo-
TABLE 10.1
Costs of Copper Sulfate Treatments at Casitas
Reservoir, California
Treatment Cost (2002$)
CuSO
4
solution $169–499 ha
–1
($19–202 acre
–1
)
CuSO
4
crystals $152–913 ha
–1
($72–370 acre
–1
)
CuSO
4
–citric acid solution $98–1106 ha
–1

($40–446 acre
–1
)
Copper-ethanolamine granular $547–2263ha
–1
($221–916 acre
–1
)
Source: Modified from AWWARF. 1987. Current Methodology for
the Control of Algae in Surface Waters. Research Report. AWWA,
Denver, CO. With permission.
Copyright © 2005 by Taylor & Francis
ides) and common carp (Cyprinus carpio) in Lake Mathews and Copper Basin Reservoir, both in
California. Lake Mathews, a water supply reservoir, received more than 2000 tons of granular copper
sulfate over a 20-year period. The lake retained 80% of the applied copper, mainly associated with
oxidizable and carbonate-bound phases that could release copper under some chemical conditions
(Haughey et al., 2000). Copper Basin Reservoir was untreated. Sediment copper in Lake Mathews
averaged 290 mg Cu/kg dry weight; Copper Basin’s was 8 mg Cu/kg dry weight. Hepatic accumulation
of copper was found in smaller bass (< 41 cm length) and in all carp in the treated lake, but there
were no apparent effects of copper on these species, as estimated by condition factors. Copper in
treated lake sediments was found in organic, carbonate, and iron-oxide forms, with a small amount
in bioavailable form. Toxicity bioassays, using amphipods (Hyallela azecta) and cattails (Typha
latifolia), did not reveal impaired survival or growth when these species were exposed to re-wetted
pond soils that had an average concentration of 173 mg Cu/kg dry weight (vs. 36 mg Cu/kg dry
weight in untreated sediments) (Han et al., 2001). Accumulation in fish may be through food web
transfer, or through direct exposure during applications.
Copper may be highly toxic to benthic invertebrates (Giudici et al., 1988; Harrison et al., 1984;
Mastin and Rodgers, 2000; Nor, 1987), but it does not appear to continue to interact with the water
column after its deposition, at least in sediments with high carbonate content (Sanchez and Lee,
1978). Copper accumulation in sediments could produce a sufficiently high concentration to delay

or greatly increase the costs of a sediment removal project, but sediment contamination has not
been shown to impair certain fish, invertebrate, or vascular plant species.
Copper could become a problem in low alkalinity lakes and reservoirs, with low carbonate-
containing sediments, if acidification of the system occurred, perhaps through acid precipitation.
For example, in laboratory tests, copper was toxic to fathead minnows (Pimephelas promelas) at
concentrations as low as 2 μg Cu/L at pH 5.6 and dissolved organic carbon (DOC) of 20 μg/L. A
multiple regression model found that pH and DOC explained 93% of the variance in toxicity in
test systems (Welsh et al., 1993). Similar results occurred with Ceriodaphnia dubia (Cladocera)
where the copper LC
50
increased (toxicity decreased) in direct proportion to pH and DOC increases
(Kim et al., 2001). Prolonged use of copper to control algae could create a situation where an
acidified lake or reservoir was rendered unusable. Copper algicides should not be used in low pH,
low DOC, poorly buffered waters.
The potential for copper toxicity in contaminated sediments can be predicted by pore water
concentration, or by acid-volatile sulfide (AVS) concentration. AVS binds with metals, mole for
mole, to form an insoluble metal complex. Thus, if AVS concentration in sediments exceeds the
concentration of a simultaneously extracted metal (SEM), all of the metal exists as a sulfide (e.g.,
CuS) and cannot be directly toxic to benthos (Ankley et al., 1996). However, as these authors note,
resuspended sediments, or contamination of food webs via ingestion of contaminated benthos,
detritus, or sediments, may produce toxicity that cannot be predicted from the AVS/SEM analysis.
This predictive analytical tool should be useful where there are concerns about copper toxicity of
lake sediments following extensive CuSO
4
applications.
The “rebound” of algal biomass after CuSO
4
treatment may be from copper toxicity to algae-
grazing zooplankton (McKnight, 1981; Cooke and Carlson, 1989). CuSO
4

is highly toxic to species
of Daphnia, a common and effective grazer of planktonic algae, and an important item in fish diets
(Chapter 9). Copper concentrations 100 times less than needed for algae control inhibit reproduction
or are lethal to zooplankton (Blaylock et al., 1985; Naqvi et al., 1985; Winner et al., 1990). Daphnia
magna, D. pulex, D. parvula, and D. ambigua, tested in waters with an alkalinity of 100–119 mg/L
as CaCO
3,
exhibited reductions in survival and reproduction when copper concentrations exceeded
8 μg Cu/L (Winner and Farrell, 1976). The 48-h LC
50
for D. magna exposed to the complexed
products Clearigate and Cutrine-Plus (Applied Biochemists Inc., Milwaukee, Wisconsin), and to
granular CuSO
4
, were 29, 11, and 19 μg Cu/L, respectively. Alkalinity in these test systems ranged
from 55–95 mg/L as CaCO
3
at pH 7–8 (Mastin and Rodgers, 2000). These concentrations are more
than an order of magnitude lower than recommended doses for lakes with moderate or high
Copyright © 2005 by Taylor & Francis
alkalinity. In many copper-treated waters, natural mortality of algae through grazing may be reduced
or eliminated and a brief chemical-based mortality substituted, perhaps creating a “chemical
dependency” on the part of lake users.
The responses of lake communities to copper, or presumably to any toxicant, may be poorly
estimated from single species laboratory studies. Taub et al. (1990) treated species-rich laboratory
ecosystems with copper during different periods in ecological succession. Copper was an effective
algicide early in succession but became less effective as pH and dissolved organic carbon increased
over time from community metabolism. This study suggested that copper should be applied during
the initial stages of an algal bloom before cells have altered the water’s chemical content sufficiently
to limit copper toxicity, and when cells are actively dividing.

Copper stress impairs food web functions. When planktonic communities in in situ mesocosms
were exposed to 140 μg Cu/L for 14 days, not only were Daphnia, phytoplankton, and Protozoa
(ciliates, flagellates) greatly reduced in abundance, but carbon flow through the food web was
impaired. Bacteria increased significantly, but there was little energy transfer via the microbial loop
to higher trophic levels (Havens, 1994).
Fifty-eight years of granular CuSO
4
treatments of four Minnesota recreational lakes and a water
supply reservoir may have produced significant deterioration of their quality. The deposition of
dead organic matter in deeper water after a CuSO
4
application was large enough to stimulate
microbial metabolism and eliminate DO. Low or zero DO conditions apparently stimulated P release
from enriched sediments, which in turn stimulated algal blooms, requiring yet another algicide
application. A state regulatory agency terminated CuSO
4
use in all of these systems due to copper
contamination of sediment. Phytoplankton problems did not become worse (Hanson and Stefan,
1984).
Copper does not appear to be directly teratogenic, mutagenic, or carcinogenic to humans. Unlike
aquatic organisms, humans tolerate moderately high concentrations (< 1.5 mg Cu/L) (Nor, 1987).
However, the use of CuSO
4
to control cyanobacteria blooms in potable water supply lakes and
reservoirs poses a potential human health risk. Cyanobacteria, especially species of Microcystis,
Anabaena, and Anabaenopsis (Cylindrospermopsis) may produce powerful hepatotoxins and neu-
rotoxins. Consumption of raw water (prior to appropriate potable water treatment) has been asso-
ciated with livestock and human illnesses and deaths (Carmichael et al., 1985, 2001). When copper
is used to treat the reservoir, cell lysis occurs, releasing toxins (Kenefick et al., 1992). In northern
Queensland, Australia, 148 people, mostly children, were affected with hepatoenteritis. Most were

hospitalized. An epidemiologic study found that only people who had consumed water from Soloman
Dam, which had been copper-treated several days earlier, had become ill. The source of the toxin
was Cylindrospermopsis raciborskii (Bourke et al., 1983; Hawkins et al., 1985). Most modern water
supply treatment plants that treat eutrophic raw water use granular activated carbon (GAC) to remove
dissolved organic compounds. GAC may remove algal toxins as well. However, some plants process
copper-treated eutrophic raw water without GAC. Unless the operators are aware of a potentially
toxic cyanobacteria bloom, and take appropriate steps, toxin-laden water could be sent into the
distribution system. Drinking water supply managers should monitor algal species composition and
density on a daily basis, at sites along the reservoir’s length (Cooke and Carlson, 1989) in order to
anticipate an algal bloom. Cyanobacteria blooms may originate in the riverine zone, or be inoculated
from sediments and develop in the water column (Barbiero and Kann, 1994). In either case, early
and regular algicide treatment may prevent the bloom from materializing. But even this “early
warning system” (Means and McGuire, 1986) can fail to prevent the bloom.
10.6 COSTS OF COPPER SULFATE
The costs for CuSO
4
use in algae management are dictated by dose, frequency of reapplication, area
to be treated, type of algal nuisance, and other lake-specific factors. The more costly chelated or
complexed forms may be needed in hardwater situations, but may be longer lasting and more effective.
Copyright © 2005 by Taylor & Francis
In four Minnesota recreational lakes and a water supply lake, with over 58 years of CuSO
4
treatment, 1.5 million kg of CuSO
4
were applied at an estimated cost of $4.04 million (2002 U.S.
dollars), including labor and operating costs. During summer months, 35% of the chemical costs
at the water treatment plant were for CuSO
4
. Costs for chemicals to operate the plant have not
increased since terminating CuSO

4
applications. The treatments were not sufficiently cost effective,
given that benefits were temporary and there were long-term environmental changes (Hanson and
Stefan, 1984).
The variation of single treatment costs with copper formulation is illustrated by the treatments
at Casitas Reservoir, California (Table 10.1). Granular copper sulfate costs about $2.00 per kilogram,
and liquid Cutrine Plus costs about $10.00 per liter (McComas, 2003). Application costs vary
greatly.
Copper sulfate application, the standard treatment for algal problems for many decades, is often
effective for brief periods and may be the only short-term solution to a current algae problem,
particularly in water supply reservoirs. However, there is substantial evidence against the continued
use of this compound, in part from the low or non-existent margin of safety for non-target organisms.
There are other longer term and more permanent options, including control of external and internal
nutrient loading, to manage algae. Water supply operators should exercise caution in using copper
sulfate, particularly during algal blooms, and should develop a diagnosis-feasibility and manage-
ment plan to address causes of algal blooms (Cooke and Carlson, 1989; Chapter 3).
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