Efficiency of wastewater treatment plant at Zagazig City for removing microbial and chemical pollutants : case study

الملخص EN

Biological urban wastewater treatment plants utilize microorganisms for wastewater treatment so that microbiological characterization of processes is very important.

In addition, the removal of these microorganisms in the effluent for their reuse is important.

This study aims to characterize the presence of microbial flora and chemical pollutants along the processes in Wastewater Treatment Plant (WTP) at Zagazig City.

The removal efficiency of total bacterial counts was approximately 20 - 74% during all the periods of study from April 2011 up to January 2012.

However, the average total Enterobacteriaceae count in the wastewater samples reduced in all the periods by 85% except in June and December 2011in which the reduction was varied between 29-37%.

The results show a high level of coliforms, Escherichia coli, Salmonella and Shigella in the raw wastewater; although their total removal is not achieved (the removal efficiency was 11 to 83 %).

Candida spp., which is a yeast indicator, although it is less usual than E.

coli, is detected in raw wastewater as well as in treated wastewater.

The maximum total yeasts and Candida counts in the wastewater samples were reduced by 64.29 and 95.24 %, respectively in August and October 2011.

There was no difference in the physicochemical properties found in the treated wastewater during all the periods of the study in WTP.

The maximum removal efficiency of biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), nitrate, sulphate and oil in the treated wastewater samples was 91.6, 89.8, 8.6, 45.4, 99.2 and 90.2 %, respectively