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.
