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How to Control Algae in Effluent Systems and Waste Water Treatment

Effluent Systems

Are the species of alga present likely to be cynobacteria and if so what is the likelihood of toxin contamination in the water system

Should the algae be treated?

What method for treating the algae is appropriate?

An effluent lagoon is a highly eutrophic environment, with large amounts of organic matter being regularly pumped into the lagoon. So the 3 questions above divide into a further three parts.

a) Does algal concentration limit evaporation rates?

b) Does the algae assist with the breakdown of biomass and organic pollutants?

c) What is the likely environmental impact of killing the algae?

In relation to (a) there is some evidence in the literature confirming algal concentrations do inhibit evaporation rates. It is dependant on a number of variables that can often be particular to the area concerned. This issue can be relatively easily determined by conducting a small scale experiment. RCI can suggest experimental methods if required.

In relation to (b) When considering the nature of the environment, concentration of biomass involved and the normal respiration cycle of an algal cell, the argument that high levels of algae will assist in the breakdown of organic biomass is difficult to sustain.

There are times in a 24 hr cycle when algal populations are depleting oxygen in the system. On balance the proposition algal populations will contribute to aerobic activity to be highly unlikely.

In relation to (c) the consequence of killing such a large volume of algae needs to be understood before action is taken. The sudden death of this number of algal cells is likely to result in the following:

A release of all the toxins present in the algal cells at one time. This of itself probably does not change the overall status of a system as it is already likely to be highly contaminated with toxin. Killing all the algae at one time will cause a spike in toxin that will stimulate bacterial digestion of toxins already taking place.

Oxygen levels are likely to be relatively low in a system of this type; the death of large volumes of algae will cause these levels to decrease. This may result in the death of fish.

Algae and Algal Blooms

There is no easy definition of an alga. Algae are generally microscopic organisms, are generally thought of as simple aquatic plants which do not have roots, stems or leaves and have primitive methods of reproduction.

Click here for further information on algae.

Methods for treating algae also deserve consideration.

Some common options to consider are:

Copper Sulphate
Copper Sulphate and hypochlorite
Coptrol

Examining 1 Copper sulphate in effulent systems.

It is worthwhile reviewing the chemistry of this approach which is outlined below:

Effluent water is usually highly mineralised. When copper sulphate is added to these environments copper sulphate reacts in the water. Initially copper is released from the sulphate bond creating Cu++, at the same time sulphate reacts with water creating mild sulphuric acid.

It is the Cu++ that is toxic to algae; however, its persistence in this form has a very limited duration. Cu++ reacts with carbonates and hydroxides in solution to form insoluble copper compounds which has no algal toxicity. In most cases only 5% of the Copper ion from Copper Sulphate remains in the Cu++ phase for 60 minutes. Most is lost as an insoluble form in less than 60 minutes and never comes in contact with the target algae.

Try conducting a pilot test using copper sulphate and watch for a cloudy reaction,the reaction will be copper sulphate transforming into an insoluble copper carbonate/hydroxide compound.

In Australia Copper Sulphate is no longer approved for use in effluent treatment systems.

Examining 2 Hypochlorite, does not work as an efficient algaecide in fresh water. When used in an organic rich environment such as this it will be even less effective. Mixing Copper Sulphate and hypochlorite should be avoided. It will produce a highly noxious chlorine gas that could cause significant health problems to anyone exposed to it.

Examining 3 Coptrol has a number of major advantages.

Applying product over a large surface area will require either a large input of labour or aerial application. Dosing marginally effective copper sulphate from a boat is a highly labour intensive operation with the possibility of health problems for those exposed to the lagoon for prolonged periods.

Application of Copper Sulphate by air also has serious issues. Reacting copper crystals into slurry in an aircraft tank creates real potential for corrosion in an aeroplane. There is also the question of the even distribution of copper sulphate in such large volumes over such large areas.

By contrast Coptrol is a non corrosive liquid that can be readily applied by air over large areas. For example Coptrol is routinely aerially applied to rice production systems in Australia.

Coptrol is a liquid designed to remain stable in highly mineralised aquatic environments without the risk of precipitation. It is ideally suited for use in effluent pond systems as they are usually environments high in carbonate and hydroxide anions. Application rates will depend on the likely concentration of algae. Once the algal situation is brought under control lower rates of application can be used to ensure ongoing control.

Coptrol works by accumulation of copper in the algal cell, the chelate works as a nutrient source for algae. This ensures the algae keeps accumulating copper until it reaches the point of toxicity. The chelate protects the copper from precipitation. Coptrol is approved for use in potable water supplies in

Australia

.

In summary Coptrol is easier and cheaper to apply than the alternatives and has a proven record dealing with algal problems in effluent systems.

To control algae add Coptrol at 8-10 litres per megalitre of water. Best results are achieved when applying Coptrol by spraying the surface of the water.

Click here for full application rates.

Click here for Coptrol Bibliography

Click here for Coptrol Frequently Asked Questions.

Click here for Information on Coptrol and Environmental Safety

If you wish to purchase Coptrol click here

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