Fate of Anionic Surfactants in a 38ML∕Day UASB-Based Municipal Wastewater Treatment Plant: Case Study

The outcome of a 15-month monitoring study (August 2004–October 2005) on the anionic surfactants (AS), at the 38ML∕day up-flow anaerobic sludge blanket (UASB)-based sewage treatment plant (STP) is described. The average removal of AS was only around 57%. Appreciable concentration of AS was being discharged to the watercourse (average 2.41mg∕L ; range 0.63–5.16mg∕L ). On an average dried sludge contained 1,560mgASkg−1 dry weight. Mass balance indicated that, AS load of the orders of 23 and 33% is removed by adsorption in UASB reactors and polishing ponds (PP), respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation (≈70%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100units , than 43 and 7units are discharged with treated effluent and dried sludge, respectively, whereas 33 and 16units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds, respectively.