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EVALUATION OF CHITOSAN COAGULATION AS A SUSTAINABLE METHOD FOR POINT OF USE DRINKINGWATER TREATMENT IN DEVELOPING COUNTRIES
Impact/Purpose:
We will evaluate the effectiveness of chitosan coagulation for drinking water treatment both alone and as an improvement for other POU methods.
Description:
Chitosan A was found to remove up to 3.4 log10 E. coli, a reduction of 99.96%. The removal was dose dependent; up to a point, removal of E. coli increases with increasing dose. Removal of E. coli ranged from 0% removal by a dose of 1g/L to 99.96% (3.4 log10) removal by a dose of 20 g/L. One-way ANOVA showed that the amount of E. coli removed was significantly different between doses (p<0.0001). Chitosan B performed very poorly in comparison; it reduced E. coli by less than 0.5%. Chitosan C had the greatest removal of E. coli of all the chitosans tested. It also removed E. coli at lower doses than the other chitosans tested, with 99% (2 log10) reduction of E. coli at a dose of only 0.1 g/L. A dose of 10-15 g/L could reduce E. coli by 99.99996% (6.45 log10), meeting the USEPA efficacy standard for bacteria for a point of use (POU) drinking water treatment technology.
The removal of MS2 from water by Chitosan A was extremely poor; at a dose of 15 g/L, which removed 99.78% of E. coli, the reduction of MS2 was less than 0.5% (0.14 log10). Chitosan B was not tested because of its poor performance against E. coli. Chitosan C achieved the highest reduction of MS2. The highest dose tested, 15 g/L, removed 99.99993% of MS2 (6.15 log10). There was a dose effect above 5 g/L, with the removal increasing with increasing dose. The hypothesis that chitosan could remove 99% of MS2 from water was only accepted for chitosan C; this chitosan meets the USEPA POU technology standard for viruses (99.99% reduction) at a dose of 15 g/L.
Chitosan A was tested in combination with filtration by a ceramic filter to determine if it could increase the reductions of E. coli compared to filtration alone. Filtration alone was highly efficacious in removing E. coli; filtration removed an average of 99.99999% (7.0 log10) E. coli from water. Coagulant A and filtration, when used sequentially, removed 99.9999999% (10.0 log10) of E. coli, an increase of 99.9% (3 log10) over filtration alone. These results indicate that Chitosan A could meet the threshold for increasing the removal of E. coli by 99.99% over filtration alone. Based on the log reductions achieved in experiments with Chitosan C alone, it could increase the efficacy of filtration by >99.9999 (6 log10). Ceramic filtration alone was not effective in removing MS2; the reduction of MS2 by the ceramic filter was <0.5%. Ceramic filters appear to have insufficient pore sizes to trap and remove viruses; they pass through the filter into the effluent water. The combination of chitosan A and filtration produced no removal of viruses. Chitosan C could increase the efficacy of MS2 removal, but this was due solely to the coagulant action of the chitosan and not the filter.