Investigation of sewage sludge quality for land application: A case study: Two Isfahan wastewater treatment plans

Abstract

Aims: The aim of this study was to investigate sewage sludge quality of Isfahan wastewater treatment plants (WWTPs) as a fertilizer in agricultural lands. Materials and Methods: The samples were collected seasonally from two WWTPs, including North-Isfahan and Shahin-Shahr in 2012 and 2013, seasonally and biochemical parameters were measured for each site. Results: The studied parameters were meet the Iranian standard level, including pH, nitrogen, phosphorous, potassium, calcium, total solids, organic matter, and moisture content except of magnesium. The carbon-nitrogen ratios was varied 7.41-9.45 and 8.7-9 in Shahin-Shahr and North-Isfahan WWTPs, respectively. The organic nitrogen was composed the highest percentage of the total nitrogen (about 78%) and inorganic nitrogen was in normal ranges. The electrical conductivity was varied 5-8.8 ds/m to 4.6-7.5 ds/m in Shahin-Shahr and North-Isfahan WWTPs, respectively. It may contribute to soil salinity in long term. Maximum nitrogen and phosphorous values were related to winter samples in both WWTPs. In Shahin-Shahr WWTP, minimum and maximum of potassium, calcium, and magnesium were measured in spring while they were the highest in spring in North-Isfahan WWTP. Conclusion: Application of sewage sludge of Isfahan WWTP as a fertilizer could be useful regardless to its microbial contents because it provides essential nutrients for plants growth regardless to its fecal and total coliforms.