ALGAE & CYANOBACTERIA
many countries now prohibit or limit the use of copper
sulfate and alternatives need to be investigated.
Project #4094 (Burch, to be completed in 2012)
was undertaken to evaluate a range of alternative
and innovative techniques for control of algae and
cynobacteria that have potential for application
in drinking water reservoirs. Methods to control
cyanobacteria in source water can be divided into five
major groups: Chemical, Nutrient Control, Physical,
Biological, and Novel Techniques. The research developed
the table below that summarizes these alternative and
innovative cyanobacteria control methods, information
on their effectiveness, advantages, and limitations in
relation to their use.
Table 1: Equipment and methods developed for managing cyanobacteria and green algae in water bodies
PRINCIPLE – MODE OF ACTION
e.g., PACTM 27
EnvirofirstA (Solvay Interox)
Copper chelates provide an aqueous biologically active form of copper to treat
cyanobacteria while limiting the reactivity of the copper with carbonates and water
to form undesirable by-products. Claimed to be effective at lower concentrations
than conventional copper-based algal treatment, thereby requiring less copper
(0. 2–1.0 mg/L). Formulations are generally recommended for use in hard, alkaline
waters to overcome rapid copper complexing to carbonates, which limits toxicity and
efficacy of copper sulfate.
Solid granules of sodium carbonate peroxyhydrate directly applied to a water body
release sodium carbonate and hydrogen peroxide. Hydrogen peroxide then degrades
further into hydroxyl free radicals, which degrade the cell membrane and DNA of
algae. Green algae have a higher tolerance for hydroxyl radicals than cyanobacteria
thereby achieving some specificity. Peroxide may also reduce tastes and odors by
oxidizing geosmin and methylisoborneol. When the peroxide treatment ceases, algae
may begin to regrow.
Electrochemically generated active oxygen species. Mechanism for application to
large water storage. Shown to be effective in inactivating micro-organisms and
damaging membranes of Microcystis aeruginosa.
Oxidising agent, which acts in the same way as hydrogen peroxide. Used by a small
number of North American water utilities. Effective but more information required on
effect on other aquatic organisms.
Produces hydroxyl radicals after ultraviolet excitation. Limited use due to TiO2
insolubility in water.
Oxidizing agent previously employed in reservoir situations. Effective dose is
dependent on the chlorine demand of the water, most algae controlled by residues of
free chlorine between 0.25 and 2.0 mg/L.
Photon-initiated interactions between humic substances and other chemicals to form
oxidizing agents. Shown to kill M. aeruginosa and A. variabilis while less sensitive to
Barley straw releases chemicals during decay that function as an algistat to inhibit
algal growth. Promoted as cheap and ‘natural’ method without frequent chemical
use. Many studies for and against.
Other plant material has been tested for their algicidal activity. These include rice
straw, fruit peel, rotting plant and wood material, leaf litter, and wood extracts.
Further work is needed to identify the algicidal compounds involved.
CONTINUED ON PAgE 14