AWWA WQTC71437

This study addresses the colonization of a submerged hollow fiber membrane-based watertreatment plant by a population of pulmonate snails. Physical shearing of the fibermembranes caused by embedded calcareous shell structures, has created a challenge inmeeting membrane integrity testing. Chlorinedioxide (ClO₂) has been successfully used in treating and preventing the proliferation ofboth bivalve and gastropod mollusks. The biocidal effectiveness of ClO₂ is consideredsuperior to that of chlorine and hypochlorite in penetrating cell wall structure, acting onthe colloidal nature of protoplasm, and suspending cellular enzymatic activity.Additionally, ClO₂ has been shown to have added advantages over chlorination byimproving the removal of organic carbons and minimizing disinfection byproduct.A definitive bioassay was developed to establish the ClO₂ dose concentration andexposure that would effectively inactivate the life cycle of the resident snail. Resultsderived from initial bench scale dosing experiments performed on a laboratorypropagated snail culture, suggest that continuous dosing at lower concentrations may bemost effective by inducing a perpetual moribund state. In contrast, it was found thatintermittent dosing at levels tenable for drinking water application, were ineffective atinactivating all of the life stages tested. Microscopic observations of the blastula andembryo stages made it possible to identify the egg bound vitellus content as a majorprotective barrier against oxidation. Additional chemical dosing trials are scheduled tobe conducted in a custom built monitoring chamber stationed at the affected watertreatment plant. Concurrent studies will be performed aimed at evaluating theeffectiveness of ClO₂ as a pretreatment option to mitigate downstream Total Trihalomethane (TTHM) formation. Includes abstract only.

Product Details

Edition:

Vol. - No.

Published:

11/01/2009

Number of Pages:

1

File Size:

1 file , 720 KB