The Microbiological Quality Assessment of Dewatered and Stored Sludge in One of the Wastewater Treatment Plants in Tehran During the Winter Season for Agricultural Use; بررسی کیفیت میکروبی لجن آبگیری شده و دپو شده در یکی از تصفیه خانه های فاضلاب شهر تهران در فصلزمستان برای مصارف کشاورزی



M Ghani MARYAM ; M Askari MASOOMEH ; B Mahmoudi BABAK ; N Mousavipour NEJAT ; Rb Rashvanlou Reza BARATI ; S Nazmara SHAHROKH
Source: Iranian Journal of Health and Environment Published:2025

Abstract

Background and Objective: Sewage sludge, a byproduct of wastewater treatment plants, is rich in organic matter and nutrients. With appropriate treatment, sludge can be utilized as a fertilizer for agriculture and soil amendment. This study aimed to evaluate the microbial quality of wastewater treatment plants in Tehran. Materials and Methods: This study was conducted during the winter of 2018. A total of 25 samples were collected from the dewatering tank and sludge storage areas. Fecal coliform counts were determined using EPA Method 1681, while Salmonella and parasite egg counts were assessed using EPA Methods 1682 and 1992, respectively. Results: In the dewatered sludge, fecal coliform levels ranged from a minimum of 67 MPN/g.TS on the first day to a maximum of 18,518 MPN/g.TS on the third day. Salmonella levels measured on the fifth, eighth, and tenth days were 0.55, 0.32, and 0.66 MPN/4g. TS, respectively. Parasite egg counts recorded on the second, ninth, and tenth days were 4 OVA/4g.TS. In the stored sludge, regardless of depth or geographic location of the disposal land, fecal coliform counts during retention times of 2, 3, 4, 5, 6, 7, 8, and 9 years were 10, 186, 480, 30, 27, 29032, 2, and 11 MPN/g.TS, respectively. Salmonella and parasite eggs were not detected in the stored sludge. Conclusion: The findings indicate that, in the sludge storage unit compared to the sludge dewatering unit, achieving Class A standards for sludge is feasible through continuous quality monitoring. © 2025 Elsevier B.V., All rights reserved.