J Hart, P Scott and P R Carlile

June 1992

SUMMARY

I BENEFITS

Identification of processes capable of removing algal toxins from drinking water.

Optimisation of processes for removing algal toxins from drinking water.

II OBJECTIVES

To identify and develop processes suitable for the removal of algal toxins and to provide a basis for estimating potential water treatment costs.

III REASONS

Blooms of blue-green algae can give rise to the production of toxins that may contaminate freshwaters used as sources for potable water. There is concern that these materials are not effectively removed by conventional water treatment processes and that they may enter supply.

IV CONCLUSIONS

The laboratory tests have shown that advanced water treatment processes can be used to remove microcystin-LR from a lowland derived water. The conclusions for each process are as follows:

1. Powdered activated carbon (PAC) dosing is effective, but the degree of removal is strongly dependent on the dose applied. A wood PAC gave better removals than other source materials.
2. A coal based granular activated carbon (GAC) is more effective than other source materials, although bed lives are short for toxin removal.
3. Chlorine dioxide and potassium permanganate are effective oxidising agents for removing the toxin from clarified and sand filtered water.
4. Results are not yet available for toxin removal by ozonation.
5. Nanofiltration can be used effectively to remove the toxin.

V RECOMMENDATIONS

There are no recommendations at this stage of the project as the full evaluation of advanced water treatment processes has not been completed, and further investigations are underway. The final report for the project is due for completion in March 1993.

VI RESUME OF CONTENTS

The report contains the results of some laboratory scale studies, used to investigate the removal of microcystin-LR from a lowland derived reservoir source, by advanced water treatment processes.

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