The Experimental Study Of Adding Diatomite Enhanced UCT Process

The UCT process is the deformation technology of A/O process, the difference is increased the mixture returning from the anoxic reactor to anaerobic reactor, as well as the part sludge of sedimentation tank flowed to anoxic reactor instead of anaerobic reactor, compared with A2/O process, the effect of nitrogen and phosphorus removal have the bigger promotion. However, the effluent index of the pollutants in traditional UCT process still can not stable up to the A standard of the《urban sewage treatment plant pollutant discharge standard》(GB18918-2002).The test added the diatomite into aerobic reactor of the UCT process, using the excellent affection, such as adsorption、flocculation、precipitation, of the diatomite, in order to strength the UCT process. The influences of diatomite dosage、sludge load、sludge age and reflux ratio are studied and the economic indicators are analyzed. In addition, the removal efficiency compared with the traditional UCT process, the main results are summarized as follows: (1) As the carrier of microorganism, diatomite had the biological strengthening affection, so the pollutant effluent indexes were increased to a large extent. With the diatomite dosage increases ceaselessly, water pollutant concentration decreased, when the dosage of diatomite is20mg/L, the COD, NH3-N, TN, TP removal rates were85.3%,91.2%,74.3%and88.3%, the effluent concentrations were43.1mg/L,2.9mg/L,12.4mg/L and0.43mg/L reaches the Class I (A) standard.(2) When the sludge load increases from0.35(COD)/(kg MLSS· d) to0.45(COD)/(kg MLSS· d), the removal rate of TN and TP are impacted significantly, while the removal rate of COD and NH3-N only have little influence. When the sludge load is0.40(COD)/(kg MLSS· d), the effluent quality is best, the removal rate of COD is87.6%, average concentrations in the effluent is33.3mg/L; the removal rate of NH3-N is90.5%, average concentrations in the effluent is3mg/L; the removal rate of TN is80.1%, average concentrations in the effluent is10.1mg/L; the removal rate of TP is88.7%, average concentrations in the effluent is0.38mg/L, the effluent indicators have reached the Class I (A) standard.(3) When the reflux ratio increased100%to200%, the removal rate of TN is improved greatly, increased from74.3%to82.8%, while the reflux ratio has the little influence on the removal rate of COD, NH3-N, TP. When the reflux ratio is100%, the pollutant indicators have reached to the Class I (A) standard.(4) When the sludge age gradually increases from8d to15d, the removal rate of COD, NH3-N and TN show upward trend and the removal rate of TP show downward trend. When the sludge age is from12d to15d, the effluent could reached the Class Ⅰ (A) standard limits.(5) The economic and technical are analyzed in the article, the increase of cost is mainly due to the diatomite adding and the expenses by processing sludge, about0.23～0.24yuan/tons of sewage, so it is economically feasible.The experimental results showed that:the removal effect of COD, NH3-N, TN, TP in adding diatomite enhances UCT process is great, the effluent can meet the Class Ⅰ (A) standard limits of Pollutant discharge standard of town sewage (GB18918-2002). It has great application prospects and no secondary pollution to the environment.