Distribution Of Organic Toxicity In Activated Sludge In The Process Of BPA Synthetic Wastewater Treatment

The key factor limiting land disposal of excess biological sludge is the toxicity. Regarding to organic wastewater biological treament process, the issue for excess sludge land disposal is the organic toxicity. The process of sludge toxicity caused by BPA biodegradation was studied under various conditions as follows:1) The synthetic wastewater containing BPA was treated in sequencing batch reactor (SBR) and continuous flow reactor respectively, so the sludge toxicity properties with various flow patterns were contrasted; 2) In different stages, the original BPA concentration was controlled as 20mg/L or 40mg/L respectively in experimental process. Then, the relationship between toxicity of sludge and original BPA content was investigated; 3) In SBR process, the sludge toxicity properties under various operation parameters as SRT 20d, HRT 12h and SRT 10d, HRT 8h was contrasted with original BPA concentration as 40mg/L. As a result, the sludge toxicity variation with operation parameters was explored. In each research situations above, effluent COD, BPA contents both in liquid and sludge, sludge toxicity and distribution in sludge flocs including outer EPS section, inner EPS and intracellular seciton were investigated. The results are obtained as follows:1) When BPA was fed into the blank SBR, the BPA removal in the beginning period (0-10d) was caused most by adsorption and desorption with sludge; the toxicity both in the whole sludge flocs and outer EPS section was significant. As to the toxicity of whole sludge and outer EPS section, the difference between experimental and blank processes are 18.9% and 5.16%respectively for original BPA as 20mg/L and 19%and 6.37%respectively for original BPA as 40mg/L.2) When BPA was removed completely in the biological process, the toxicity resulted from BPA biodegradation accumulated mainly in the inner section of sludge flocs including intracellular section and inner section of EPS. When the SBR process was controlled with parameters as SRT from 20d to 10d and HRT from 12h to 8h, the sludge toxicity was relatively reduced.3) By contrasting of continuous flow reactor and SBR, the performances on COD and BPA removal of the continuous flow process were worse, and the sludge toxicity was accordingly more significant than SBR. The difference of whole sludge flocs toxicity between continuous flow and SBR experimantal sludge was 30.54%, the toxicity difference in outer EPS between these two flow patterns was 19.34%.