Enhanced Treatment Of Orange Can-Processing Wastewater With Pectinase

Due to seasonal harvest,the quality and quantity of the orange can-processing wastewater fluctuates largely.It is very difficult to treat the wastewater and to dispose the sediment because there are pectin,suspended fiber and small pulp that lead to decay.The orange can-processing wastewater from Zhejiang Aisiman Food Co.,Ltd. was analyzed,and pectin was suggested to be one of the main factors influencing the wastewater treatment.The feasibility of pectinase-enhanced wastewater treatment was investigated and the results are shown as follows:1.According to determination,there were a lot of pollutants in the wastewater, and the quality and quantity changed largely.Some physical and chemical characteristics of the wastewater were:COD_cr concentration 476～3153 mg/L,BOD₅ concentration 297～893 rag/L,pH 2.5～6.0,SS 46～541 mg/L,pectin content 0.2%～2.5%.2.Pectin is a thickening agent,and it can make the wastewater ropy.The application of pectinase to the wastewater helped to reduce the viscosity.Different pH values(2.5～6.0),temperatures(25～55℃) pectinase dosage(0.01～0.06g/L),reaction time(0.5～2.0h) were tested and the optimum Condition was pH 4.5,35℃,0.04 g/L pectinase,reaction time 2.0h..3.The immobilization and performance of pectinase were conducted with sodium alginate as co-reagent.The condition for pectinase immobilization and application was:sodium alginate content 1.0%～4.0%,glutaraldehyde content 0.1%～0.8%,pH4.0,temperature 40℃,reaction time 2.0h.The immobilized pectinase was capable of completely degrading 2.5%pectin in the wastewater.4.After pretreatment with pectinase,the wastewater was further treated by sedimentation and biological process.The CODcr removal was more than 85%.5.Anaerobic digestion was carried out to reduce the sludge volume.The sludge yield from orange can-processing wastewater was large and it was difficult for the sludge to be dehydrated with pressure filtration.The sludge from primary sedimentation tank and secondary tank was fermented under anaerobic condition.The sludge content was increased from 92.0%to 98.8%in 24 days.