Design and Performance Study of a Bench-Scale Biological Wastewater Treatment Plant for a Sea Food Processing Industry

Abstract

Shrimp industries are though important in respect of foreign earnings they are producing huge amount of wastewater that contain large quantities of biodegradable organic wastes and disposed directly to the environment without any treatment. It is noted that none of the industries are following ECR 1997 (Revised in 2010) and they do not have effluent treatment plant that designed based on the characteristics of shrimp processed wastewater so far. Conventional ETP is physico-chemical type and takes higher cost in operation. Therefore, the best possible biological wastewater treatment plant design and its performance analysis is the main goal of the study. Wastewater has been collected from a selected industry. The wastewater samples were characterized for the basic wastewater qualities. Based on the characterization and literature review the design criteria has been selected. A bench scale treatment plant has been designed and installed in the Environmental Engineering lab. The bench scale plant were run over a designed period of 12 to 13 months during July 2017 to May 2018. About 400 selected samples were collected and tested for were 12 different selected parameters. As found that the shrimp processed wastewater contains large amount of organic waste, thus decision has been taken to design suspended growth activated sludge biological treatment process. In bench scale plant, two clarifiers and an aeration basin have been designed as a completely mixed extended aeration activated sludge process. Collected wastewater from the selected industry and poured in to the bench scale plant. According to design the hydraulic retention time was nearly eight hours. The results show that the raw wastewater of shrimp processing industry contain average DO, BOD5, COD, TDS, SS and Chloride of 2.07, 177, 355, 2894, 383 and 821 mg/L respectively. The EC and pH was contain of 4.51 mS/cm and 8.03. The bench scale plant has removed remarkable organic loading. The BOD5 reduction has been founded from 177 to 41 mg/L (77%) and COD from 355 to 117 mg/L (67%) respectively. The rest of all parameters have met the national standard. It can be said from the obtained analysis that the treatment was moderate level. Based on the foregoing result it may be said, this design criteria or bench scale plant can be effectively used in shrimp processed wastewater treatment.