A Study On Filamentous Bulking Control In The Activated Sludge System

The sludge bulking is the main problem in Municipal Waste Water Treatment Plants (WWTP). The result of sludge bulking is low effluent quality, high biomass loss, even system failure. So the study on bulking control is very important for the operation of activated sludge system. Based on the fact that the filaments can not use nitrate as an electron acceptor, filament bulking control in the active sludge system was studied.The experiment use two equal rank reactor, choose three easiest factors (low pH, low DO, low sludge load) to make the filament bulking in the stable activated sludge, then operated the adding nitrate and recovered condition (namely natural recover) respectively. It has been specifically analyzed that add the nitrate to enter the water the water quality and the sludge subsidence performance. Experimental result expression:(1) Nitrate is a very good inhibitor for sludge bulking from filament bacteria, the fast speed in the condition of natural recover is 24.5mL /g.d, but the lowest speed in the nitrate condition is 50.57mL/g.d. Throws the nitrate suppression COD basically not to affect, the affections of ammonia nitrogen, the niter nitrogen influence are very big.(2) The denitrification time was an important effect on the controlling of sludge bulking. Complete nitration may destroy the sludge's nitrifying performance. The nitrobacteria in the sludge maybe cleared away through five days denitrification. Adding about 35 minutes aeration after denitrification is an advantageous for the coming back of the sludge's nitration performance. If we do it, the sludge's nitration performance may come back completely three days latter, and the concentrations of ammonia and nitrate maybe near to their concentration in active sludge which is brought up steadily.(3) Different mixing has different effect on the controlling of sludge bulking. Magnetic force mixer largely influences the filament bulking. Because this mixer is mixing in the bottom of the reactor, the filament is broken in immediately and the SVI descends greatly in short times.(4) Adding nitrate has no effect on inhibiting non-filament bulking.