Factors influencing ultraviolet disinfection performance part II: Association of coliform bacteria with wastewater particles

A technique is described for quantifying the number of particles with embed ded coliform bacteria in wastewater samples. This technique was applied to eight different wastewater samples collected from eight significantly diffe rent treatment processes (five variations of the activated-sludge process, a trickling filter, an aerated lagoon, and a facultative lagoon). For all t reatment process types that did not use chemical coagulants, total number o f particles with embedded coliform bacteria correlated linearly with number of residual coliform bacteria following high doses of UV light. Lagoon tre atment processes led to the formation of fewer bacteria-associated particle s than either thr acrtivated-sludge or trickling-filter processes. Chemical coagulants showed a potential to significantly reduce the inactivation fra ction of coliform bacteria associated with particles.