AWWA WQTC65935

Cyanobacteria are a concern for water authorities worldwide as their persistence in water suppliescauses numerous problems for water treatment plants. These include exertion of an additionaldemand on coagulants and clogging of filters which results in reduced filter run-times andincreasing backwash frequencies. However, the major problem of cyanobacteria is the metabolitesthey produce; in particular, cyanotoxins and taste and odor (T&O) compounds. These metabolitesnot only account for a large number of consumer complaints due to aesthetic problems, but theyalso have the potential to compromise human health. Furthermore, these metabolites have beenshown to be somewhat recalcitrant to conventional water treatment processes.One of the major species of cyanobacteria which plague Australian water authorities is Anabaenacircinalis, which can produce geosmin (a T&O compound) and a range of saxitoxins (potentneurotoxins). Recent surveys of A. circinalis blooms in South Australian water sources have shownthese metabolites are present at significant concentrations.This study evaluated the treatment processes at two existing South Australianwater treatment plants for the removal of A. circinalis cells and the associated metabolites, geosminand saxitoxins. In particular, the coagulation process, powdered activated carbon (PAC) dosing andbiological sand filtration were assessed for their ability to remove these contaminants. The resultsso far have shown that if optimized, coagulation can remove most of the cyanobacterial cells and asignificant proportion of the metabolites as they are largely contained within the cells (intracellular).Under favorable conditions, biological rapid sand filtration can remove the remainder of thegeosmin, representing the dissolved form (extracellular) whereas PAC is not quite as effective, andstill allows a fraction of the geosmin to enter the distribution system. Includes 7 references, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

9

File Size:

1 file , 350 KB