Modification and Evaluation of Parboiling Wastewater Discharge System for Minimizing the Effluent Volume to Be Treated in Rice Processing

Abstract

This study was conducted to reduce the wastewater volume to be treated in rice milling industry by modifying the existing effluent discharge system and the cleaning process. At the beginning, pH, Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) levels of existing wastewater ditch were measured. Paddy cleaning section of parboiling was improved. Waste water generated from washing was directly released to irrigation purpose, and effluent of soaking tanks was collected to a ditch followed by 10 hours aeration treatment. The waste of steaming process was directly sent to ash room. The BOD, COD, and pH values of wastewater, collected in every operation of rice parboiling, were analyzed. pH values of effluents indicated considerable improvement after the treatment. After the modifications of the wastewater discharge system, the BOD and COD levels of wastewater in the ditch, used for washing and soaking showed significant reduction (p<0.05) compared to existed conditions, from 2150 ml/1 to 389 ml/1 and from 3776 ml/1 to 687 ml/1, respectively. Further, wastewater used for paddy washing can directly be utilized for irrigation purposes due to lower values of BOD and COD. The levels of BOD and COD of steamed water collected in separate small ditch resulted in significantly higher levels (p<0.05) than other wastes. Aeration treatments applied to the ditch of soaking water had significantly reduced (p<0.05) these parameters below the maximum recommended limits for irrigation purpose. The study reveals that proper management of paddy cleaning process and wastewater discharge system can maintain the BOD and COD levels below to the recommended limits.