The influence of physical–chemical and biological factors on the removal of faecal coliform through down-flow hanging sponge (DHS) system treating UASB reactor effluent

The mechanism of faecal coliform removal in down-flow hanging sponge (DHS) system treating up-flow anaerobic sludge blanket (UASB) reactor effluent was the subject of this study. The results obtained revealed that the most important removal mechanism of faecal coliform in the DHS system is adsorption, followed by predation. Die-off is a relatively minor removal mechanism in the DHS system. The impact of physical and chemical factors such as contact time, effective sponge bulk volume and pH values on faecal coliform removal has been investigated. Increasing the contact time and sponge bulk volume exerted positive effect on the removal of faecal coliform. Changing the pH values between 6.5 and 9.0 did not show significant impact. Reducing sponge pore size from 1.92 to 0.56 mm, increased faecal coliform removal by a value of 1.3 log10.