Evaluation of UVLED disinfection for biofouling control during distribution of wastewater effluent

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A commercially available UVLED flow-through device, operating at 40 mJ/cm², was examined for biofilm control on irrigation pipe material fed by wastewater effluent. Biofouling was monitored through total coliform counts, crystal violet (CV) staining, and ATP analyses. A UV fluence of 40 mJ/cm² at 280 nm retarded biofilm formation; however, complete biofilm prevention by UV treatment was not achieved despite a high inactivation of planktonic cells. After 5 days of the study, the total coliform and CV biofilm quantification assays between the UV-treated and control bioreactor coupons were not statistically different. The total coliform counts indicated a stable biofilm cell concentration was reached; the CV assay showed biofilm biomass accumulation with time. The ATP results revealed higher coupon ATP on the UV-treated coupons than the control coupons by day 5. The results provoke an interesting discussion surrounding the contribution of viable cells, represented by total coliforms, and extracellular polymeric substance (EPS) to total biofilm biomass. This study also highlighted a need for further investigation into the relationship between ATP responses and complex UV-stress responses of diverse microbial communities as opposed to pure bacteria cultures.