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 embedded coliform bacteria in wastewater samples. This technique was applied to eight different wastewater samples collected from eight significantly different treatment processes (five variations of the activated-sludge process, a trickling filter, an aerated lagoon, and a facultative lagoon). For all treatment process types that did not use chemical coagulants, total number of particles with embedded coliform bacteria correlated linearly with number of residual coliform bacteria following high doses of UV light. Lagoon treatment processes led to the formation of fewer bacteria-associated particles than either thr acrtivated-sludge or trickling-filter processes. Chemical coagulants showed a potential to significantly reduce the inactivation fraction of coliform bacteria associated with particles.