Organic Toxicity Formation And Distribution In Activated Sludge Treating Synthetic Wastewater Containing DMF

N-dimethylformamide (DMF) was taken as the target pollutant, the aerobic condition was controlled by DO as 2.0-3.Omg/L, and contrast study was performed between blank reactor fed only with peptone and experimental reactor fed with mixture of peptone and DMF as organic carbon source. The effluent COD, DMF content both in effluent and sludge, and organic toxicity of sludge were analyzed. The process of sludge toxicity caused by DMF biodegradation was studied under various conditions as follows:1) The sludge toxicity formation and distribution in sludge flocs were investigated between SBR acclimated gradually with DMF (from 40mg/L to 200mg/L) and that impacted with 200mg/L DMF. Then, the toxicity properties resulted from various DMF removal processes as adsorption and biodegradation were analyzed.2) In SBR process, the sludge toxicity properties under various operation parameters as SRT 20d, HRT 12h and SRT 10d, HRT 8h were contrasted with original DMF concentration as 200mg/L. As a result, the sludge toxicity variation with operation parameters was explored.3) The toxicity of activated sludge formed in SBR and continuous flow reactor was contrasted with original DMF concentration as 200mg/L.The results obtained are as follows:1) both for two SBRs, one with DMF acclimation from 40mg/L to 200mg/L and another with DMF impaction with 200mg/L, organic toxicity accumulated in outer EPS section of sludge flocs to a relatively low level. While, sludge toxicity of outer EPS section for DMF impaction SBR was in a range of 10%-30%, which was a little more than that of DMF acclimation SBR.2) In SBR, as the operation parameters were shortened, the sludge toxicity decreased to a great extent. Toxicity of sludge reduced from 44.70%to 35.30%when SRT and HRT were shortened from 20d and 12h to 10d and 8h, respectively.3) When the sludge was acclimated with DMF to stable state both in SBR and continuous flow process, the original DMF concentration was controlled as 200mg/L. In the stable stage for the DMF removal, the sludge toxicity of continuous flow process was in 35%-45%, which was below that of SBR (40%-60%) for about 10%. The toxicity of outer EPS of continuous flow process was similar to that of SBR, both below 30%. Therefore, the toxicity of inner EPS and intracellular section of SBR was above that of continuous flow process for about 10%.As to various conditions above, the toxicity of whole sludge flocs was higher than that of outer EPS for 20%, and the sludge toxicity was caused most by DMF biodegradation.