Study on the Biodegradability of Oxidized Sulfiting Rapeseed Oil

The methods of BOD5/CODCr, respiratory curve and COD30 were adopted to evaluate the biodegradability of oxidized sulfiting rapeseed oil fatliquor. The results showed that when the concentrations of the substrate were 250 mg/L and 500mg/L and the dosage of unacclimated activated sludge was 300mg and pH was 7, the substrate was biodegradable and the biodegradation rate was up to 90%. When unacclimated activated sludge was 300mg and pH was 7, the biodegradability of the substrate with the concentration of 1000mg/L became bad and the biodegradation rate reduced to 80.9%. Moreover, the effect of pH, inoculation amount and salinity on the biodegradability of the substrate was obvious. The biodegradability of the substrate was best as pH was 7 and alkaline medium had little influence on the biodegradability of the substrate. When the inoculation amount increased to 1500mg/L, the biodegradation rate increased. The biodegradability of the substrate was inhibited as the external NaCl addition was 5% or 10%. The substrate could not be degraded as the external NaCl addition was 15%. The high salinity provided hyperosmolarity for microorganism, which caused microorganism cells dehydrate and activity inhibited. When the concentration of the substrate was 500mg/L, the ratio of BOD5/CODCr increased from 0.30 to 0.46 under the optimum condition. The biodegradability of the substrate was excellent.