Quality of wastewater reuse in agricultural irrigation and its impact on public health

This study is planned to perform a sanitary survey of the largest sewage treatment plant in Riyadh, KSA, fortnightly for 6 months to examine its effluent quality as an example for the growing dependence on reuse of treated municipal wastewater in agricultural irrigation purposes to cope with increasing water shortage. The biological and physico-chemical parameters of 12 wastewater samples from the plant were examined using standard methods. The physico-chemical analysis indicated that the surveyed municipal wastewater treatment plant contained some of the studied parameters, such as turbidity, total suspended solids, biochemical oxygen demand, chemical oxygen demand and residual chlorine above the maximum permissible wastewater limits set by the Saudi Standards. However, heavy metal concentrations in all samples were lower than the recommended standards. Total and faecal coliform counts were above the permissible limits indicating poor sanitation level. Fifty percent of all wastewater samples were contaminated with faecal coliforms but, surprisingly, Escherichia coli were only detected in 8.3 % of the samples. Regular monitoring and enhancement of microbial and physico-chemical parameters of the wastewater quality served by different wastewater treatment plants for reuse in agricultural irrigation is recommended to preserve the environment and public health.