Copper sulfate
(endorsed 2005)
Copper sulfate is an active constituent in registered algicide products used in drinking water reservoirs. There are different State and Territory environment protection regulations on the use of copper sulfate in reservoirs. Further information should be sought from the relevant State or Territory agency.
General description
Copper sulfate, , is a blue crystal, or blue crystalline granule or powder, but is white when dehydrated. The chemical has a nauseous metallic taste and is poisonous. The anhydrous form contains nearly 50% copper; the commonly used pentahydrate form () contains 25.5% copper.
Appropriate handling materials for copper sulfate include fibreglass-reinforced plastic, polyethylene, polyvinyl chloride, cast iron and stainless steel. Rubber-lined and silicon-lined containers can also be used.
Chemistry
Copper sulfate is the product of the reaction of sulfuric acid with copper metal, cupric oxide or basic copper salts.
Typical use in Australian drinking water treatment
Copper sulfate is an algicide, and is used to treat toxic or odorous algal blooms in water reservoirs and other water supply storages. Copper sulfate may kill aquatic plants, insects, invertebrates and fish. Copper sulfate is subject to registration and labelling requirements of the Australian Pesticides and Veterinary Medicines Authority. Copper sulfate is not registered for general use as an algicide in all jurisdictions therefore, before copper sulfate is used in a water storage system, the State or Territory environment protection authority must be advised. In some States and Territories, a licence must be obtained for its use. The Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2002) contain information on the effect of copper sulfate on various ecosystems. There is a range of alternative water treatment and storage management methods for controlling the risks of toxic algal bloom including reducing the amounts of nutrient inflow to water reservoirs.
The application of copper sulfate products to storages should be in accordance with the registered chemical label. Copper sulfate can be applied by:
dissolving crystals of the chemical into the water using porous bags pulled by a boat
applying the crystals directly using a hopper feeder
spraying dissolved copper sulfate on the water surface.
To determine the appropriate dose rate and ensure efficient application, knowledge of algal habitat and distribution is needed. Experience with the use of copper sulfate to treat cyanobacteria indicates that it is best to start applying the chemical early in the morning, and to apply it during calm conditions. This is because cyanobacteria tend to be most buoyant at this time, and are likely to be near the surface.
For a stratified reservoir, calculation of the total amount of algicide to be added is based on the amount needed to treat the surface of the water body, because this is where most cyanobacteria will be located. Treatment of algae should be concentrated in areas of algae scum.
The amount of copper sulfate required will depend on various factors, such as pH, alkalinity and water temperature (algae are more likely to bloom in warm water).
Copper sulfate is most effective at pH values of around 8, and alkalinity less than 50 mg/L. In conditions of high alkalinity or pH, addition of an acid (e.g. citric acid) may also be needed for the copper sulfate to be effective. The concentrations of copper sulfate added are typically in the range 0.2–1 mg Cu/L, depending on the specific type of organism being controlled.
Contaminants
The purity of chemicals used in Australia for the treatment of drinking water varies, depending on the manufacturing process. Chemical contaminants that may be present in copper sulfate include (JECFA):
arsenic
chloride
iron
lead
nickel
Residue and by-product formation in drinking water
When employed in drinking water treatment, copper sulfate should be used in such a way that any contaminant or by-product formed by the use of the chemical does not exceed guideline values in the Australian Drinking Water Guidelines. A limit of 2 mg/L based on health considerations and of 1 mg/L for aesthetic considerations has been established for copper residues resulting from the use of copper sulfate.
Copper sulfate breaks down algae, resulting in the release of algal toxins and odorous substances that decay over time. Hence, a withholding period is needed after copper sulfate has been used as an algicide, and it may be necessary to monitor copper residues, toxins and odours during a follow-up period.
Copper sulfate products should not be used to treat more than half of a lake or pond at one time, in order to avoid depletion of oxygen caused by decaying vegetation. One to two weeks should be allowed between copper sulfate treatments to allow water oxygen levels to recover.
Copper entering a water treatment plant may be removed to some degree through coagulation with clarification/filtration. Elevated pH assists in copper removal.
Status
Copper sulfate was endorsed by the NHMRC for use as a drinking water treatment chemical in 1983. The revision undertaken in 2003 did not change the status of this chemical for the treatment of drinking water.
References
ANZECC (Australia and New Zealand Environment and Conservation Council)/ARMCANZ (Agriculture and Resource Management Council of Australia and New Zealand) (2002). Australian and New Zealand Guidelines for Fresh and Marine Water Quality. National Water Quality Management Strategy, ANZECC/ARMCANZ, Canberra.
Clesceri LS, Greenberg AE and Eaton AD (eds) (1998). Standard Methods for the Examination of Water and Wastewater, 20th Edition. American Public Health Association, Washington, DC.
Lewis RJ (1993). Hawley’s Condensed Chemical Dictionary, 12th edition. Van Nostrand Reinhold, New York, 315.
National Registration Authority for Agricultural and Veterinary Chemicals (1996). The Requirements Manual for Agricultural Chemicals. National Registration Authority, Canberra.
Ramadan T (2000). Algae control solves aesthetic problems. Opflow 26(8): 1–4.
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