Seasonal variation in microbiological and physicochemical characteristics of municipal wastewater in Al- Sharqiya province, Egypt ( case study)

摘要

This study was conducted to evaluate the changes in microbiological, physical and chemical quality in wastewater during treatment operations of 17 wastewater treatment plants (WTPs) in cold and hot climate over a one-year period and to evaluate the quality of wastewater in drainages that discharges from these WTPs distributed in the province of Al-Sharqiya, in Egypt, in order to examine their potential environmental impacts and assess their disposal options. Total bacterial count (TBC), total yeasts count (TYC), total Candida count (TCC), total coliform count (TCFC), total Escherichia coli (TEC) and total Salmonella and Shigella (TSSC) counts were analysed in several samples subjected to various treatment processes sequentially, including untreated wastewater (UW), aeration treatment wastewater, oxidation treatment wastewater, anaerobic treatment wastewater and effluent (treated) wastewater (TW). Physicochemical parameters (temperature, pH, total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrates (NO3-), sulphites (SO4-) and oil mg/l values of UW and TW in the WTPs) were examined in samples collected in different seasons. The results revealed that the influent wastewater was heavily contaminated with cultivable bacteria and inorganic and organic substances. Coliform bacteria were important indicators of pathogenic bacteria concentration reduction during the various wastewater processes; however, no correlation was found to Candida contamination. The TBC, TYC, TCC, TCFC, TEC and TSSC were significantly decreased (p<0.05) in treated water, and the maximum removal of TBC (60%), TYMC (59%), TCC (75%), TCFC (77%), TEC (75%) and TSSC (74%) took place during treatment resulting in an effluent of high quality. Moreover, TSS, TDS, BOD, COD, sulphite, nitrate and oil levels were significantly reduced (p<0.05) in the effluent, resulting in maximum removal of pH (6%), BOD (90%), COD (89%), TSS (88%) and SO4 (86%), obtained at the effluent. The results indicated that the treatment plants had a significant role in the control of pollution load from microbial, organic and inorganic pollution at the province of Al-Sharqiya, Egypt. Furthermore, microbiological parameters are essential for monitoring the appropriate WTPs operation, while Candida might be a significant indicator of effluent microbiological quality.