Uncoupled Metabolism Process Of Activated Sludge

The activated sludge process is in common use for the treatment of wastewater, but it also generates a large quantity of excess sludge daily as a byproduct. In this paper, based on the increasing severe problem of sludge ultimate outlet, 2,4,6-trichlorophenol(TCP), which has been proved as an efficient chemical uncoupler, is used to reducing the yield of biomass. The catabolism and the anabolism of microorganism could be uncoupled under the presence of chemical uncoupler, while the energy intended for anabolism of cells mass is dissipated and is used for catabolism, which provides a direct pathway for sludge reduction. A pilot-scale of SBR reactor was tested to investigate the sludge reduction under the present of 2,4,6-trichlorophenol and the impact of TCP on effluent quality (COD removal efficiency) and sludge characteristics. The concentration of TCP in discharged effluent and in sludge was detected. The toxicity of discharged effluent was evaluated.In the second chapter, the optimal concentrations of TCP and its effects on sludge observed growth yield and COD removal rate were investigated in batch activated sludge process. The results demonstrated that the optimal concentration of TCP was 4mg/l, while the sludge yield can reduce by 53.02% with little reduction of substrate removal rate. The results of dynamic experiment showed that specific substrate removal rate can be improved by 26～30% by 4 mg/l TCP. The higher is the uncoupler concentration, the higher the specific substrate removal rate. However, the specific cell mass production rate over unit time with TCP is lower than the control sample's. These showed that the catabolism and anabolism of microorganism was uncoupled by TCP, which predicated there was an energy-spilling process for metabolic regulation and thus caused sludge reduction.The results of 70 days continuous operation of activated sludge process showed that excess sludge production with 4mg/l TCP was reduced by 47.83%, and COD removal rate and sludge settlability were not influenced obviously. Sludge ecosystem was analysed with microscope. The results showed that the population of protozoa and metazoan was decreased dramatically in the sludge ecosystem with TCP, which result probably in alteration of sludge settlability.In the fourth chapter, the concentration of TCP in discharged effluent and in sludge was detected. The impacts of aeration time and sludge concentration on distribution of TCP in system were evaluated. The results show that, the concentration of TCP in discharged effluent is equal to 70～80% of general concentration of system. The sludge which represents the 5～10% volume of the whole system contains about 25% TCP, in which 20～30% exists within the cells. With the increasing of aeration time and concentration of sludge, concentration of TCP in discharged effluent will decrease, and that in sludge will increase.The Vero cell was used to evaluate the toxicity of effluent with the concentration of TCP being 1,5, 10, 20, 50mg/L. The results show that when the concentration of TCP is under 5mg/L, the influence on Vero cell's growth is limited to little extension, with a decreasing of 5%, and the effluent could be considered to be acceptable and safe.