New Zealand: Chapter 9: Cyanobacterial compliance

It’s not enough to say a particular water treatment is safe or not because, I feel the experts don’t really know because they haven’t tested all the different species. Test results thusfar show it’s easier to remove intact cells but not the toxins which can be released when the cells die from being handled roughly, exposed to various drinking water treatments, or as just part of their natural life cycle. Figure 9.1 from the paper states that cell lysis occurs from: “the use of algicides, pre-chlorination, senescent (eg, late summer) bloom, and pumping regimes.” Click on the document titled “Scientific Assessment of Freshwater Harmful Algal Blooms” to learn how complex this contaminant is for our drinking water authorities. This contaminant should be made a priority as new research is connecting it to Alzheimer’s, ALS and Parkinson’s Diseases, and we don’t want to have another Toledo, OH incident where 500,000 people could not use their drinking water due to toxins. Click here to read New Zealand’s compliance document to learn more.



d) Alkalinity and pH Alkalinity and pH determine the chemical speciation of inorganic carbon, such as carbonate, bicarbonate and carbon dioxide. Low carbon dioxide concentrations favour the growth of several cyanobacterial species. Hence, water conditions such as low alkalinity and hardness and the consumption of carbon dioxide during photosynthesis by algae, increasing the pH, give cyanobacteria a competitive advantage. Health Canada (2000, edited 2002).

Table 9.2: Toxic cyanobacteria species and their geographical distribution
Toxic species Cyanotoxin Location with toxin identified

Anabaena flos-aquae microcystins Canada, Norway
Anabaena flos-aquae anatoxin-a Canada
Anabaena flos-aquae anatoxin-a(S) Canada

cyanobacteria page 35

cyanobacteria page 36 Drinking-water treatment for households and small communities
Domestic treatment of drinking-water has been a recent issue of concern in New Zealand. Many reticulated supplies provide excellent quality drinking-water and additional household treatment may actually cause deterioration rather than improvement. However, domestic treatment may have a role in regions supplied with poor quality drinking-water. Such treatment, using filtration, activated carbon and oxidation has shown a good removal of health hazards associated with cyanobacteria.

New (previously unused) point-of-use filter cartridges can achieve a removal of microcystin variants in the range 30–60 percent, and this degree of removal could be increased to about 90 percent by the passage of the water through three such filters. The removal may drop to 15 percent, however, by the time the filter is halfway through its expected life. The form of the cyanobacteria also has an influence on the efficiency of removal. A filter consisting of activated carbon and ion exchange resins may remove about 60 percent of the filamentous cyanobacteria, while up to 90 percent of the single cells pass through (eg, Microcystis). As with other filter systems, the death and lysis of cells retained on the filter creates a potential concern.

Health Canada. 2000, edited 2002. Cyanobacterial Toxins — Microcystin-LR. Guidelines for Canadian Drinking Water Quality: Supporting Documentation. 22 pp.



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