ALGAL/BACTERIAL TOXIN REMOVAL FROM WATER
A Literature Survey
Report No FR0223

J R Pressdee and J Hart

Sept 1991

SUMMARY

I OBJECTIVES

To perform a review of available literature related to the removal of algal/bacterial toxins from water.

II REASONS

Recent occurrences of toxic algal blooms have highlighted the potential risk of toxins entering drinking water supplies, and posing a threat to public health. This necessitates a need for research to determine the effectiveness of different water treatment processes for removing algal toxins.

III CONCLUSIONS

Conventional water treatment processes, such as coagulation and filtration, have been shown to be ineffective at removing toxins. Pre-chlorination has also been found to be ineffective.

Slow sand filtration has shown some potential to remove toxins by biodegradation. However, not all types of toxin were successfully removed.

Activated carbon adsorption has been shown to be capable of effectively removing different toxins. With powdered activated carbon (PAC), high PAC doses were generally required. However, most of the tests were conducted with higher toxin concentrations than would probably be found in raw waters.

Granular activated carbon (GAC) can effectively remove toxins, but the studies have not fully assessed the most suitable GAC. In addition, most of the work to date has not determined the bed lives of the different GACs. Therefore, the regeneration period for a GAC bed that has been used to remove toxins cannot be specified at the present time.

The limited amount of work on ozonation has shown that it is an effective process for removing toxins, even with relatively low ozone doses. Ozonation does produce by-products, but these have been shown to be non-toxic.

There is no published literature available that has investigated more advanced water treatment processes, e.g. membranes, advanced oxidation processes.

IV RECOMMENDATIONS

To date most of the published work looking at toxin removal has been qualitative as no validated analytical technique has been available to be able to accurately determine the levels of toxins in water. Most of the studies have used toxicity tests to evaluate process performance. The occurrence of algal toxins in surface waters and the potential risk to human health necessitates their removal. The necessary research to fully assess toxin removal by different water treatment processes, so that the most suitable processes can be identified, has been proposed and accepted.

V RESUME OF CONTENTS

A review of literature related to the removal of algal/bacterial toxins is presented. The information has been separated into two groups, one considering convential treatment processes, and the other considering advanced water treatment processes.

Copies of the Report are available from FWR, price 15 less 20% to FWR Members.