Background and Aims: Lack of adequate supervision on the quality of disposal effluent and sludge from wastewater treatment plants (WWTPS) caused to their discharge by many pollutants into the environment.This study aimed to assess the microbial quality of disposal effluent and waste sludge from decentralized WWTPS in Tehran.Materials and Methods: This cross-sectional study was performed in 12 months on disposal effluent and sludge from 4 decentralized WWTPS in Tehran city. Random sampling was conducted at a monthly period. The microbial quality of disposal effluent and waste sludge were compared with the guidelines of Iranian, and United States Environmental Protection Agency (USEPA), respectively.Results: Effluent and sludge output from these plants typically were used for agricultural purposes. None of the samples of effluent meet Iranian environmental standards. Microbial quality of waste sludge from Shahrak Gharb and Ekbatan WWTPS were higher than class B of USEPA guidelines but, waste sludge from Gheitarieh and Shoosh WWTPS meet this index.Conclusion: At the present time, reuse of effluent and waste sludge from decentralized WWTPS in Tehran city were performed without any health considerations. This is a serious threat to public health; hence, executive and regulatory agencies must take action corrective measures and controls necessary in this regard as soon as possible.Key words: : Microbial quality, effluent, sludge, wastewater treatment plants, Tehran cit
