Occurrence, Monitoring and Risk Assessment of Toxic Substances in Sewage Water Treatment Plants: A Case Study, Great Cairo, Egypt. متابعة, رصد وتقییم المخاطر البیئیه للمواد السامه بمحطات معالجة الصرف الصحی: دراسة خاصه, القاهرة الکبری, مصر.

Abstract

An evaluation process on the validity of wastewater treatment plants effluents for irrigation was done. Chemical and microbial pollutants were measured occasionally in five WWTPs spread in great Cairo, Egypt. The results revealed that WWTPs used secondary treatment (Chlorination) were had the capability to scrape much amount of microbial pollutants, while the units that have only primary treatments were unable to eliminate the microbial organisms. Although the processes used at WWTPs were unspecific for inorganic contaminants removal, metals were reduced in effluents to more than 50 % about the influents. This reduce was attributed to the adsorption of metals on activated sludge which used in aeration stage. In spite of low concentration values of heavy metals in the effluents, these values were conducted to cause hazard effects for aquatic organisms especially Cd, Cu, Pb and Zn based on predict no effect concentration criteria. Water quality index was calculated to identify the applicability of WWTPs effluents for sign in irrigation. The results cleared that the effluents of all units studied weren’t applicable for irrigation purpose. These consequences can affect directly on biological cycles. Thus it seems that more consideration of bio conservation protocols is so important.