Sewage sludge composting: quality assessment for agricultural application
In order to use sewage sludge (SS) composts in agriculture, it is extremely important to estimate the quality of compost products. The aim of this study was to investigate the quality of composted SS as a fertilizer and soil amendment especially in semi-arid areas. To determine the quality and agronomic value of the SS compost products, analyses on pH, electrical conductivity, organic matter content, C/N ratio, phytotoxicity, microbial load, and heavy metal content of composted anaerobically digested SS, with different proportions (1:1, 1:2, and 1:3 v/v) of green and dry plant waste, as bulking agents, were performed. The 1:2 and 1:3 mixtures of SS and green/dry plant waste were the most beneficial for composting, with final composts attaining high organic matter degradation and exhibiting low amounts of heavy metals, a relatively high germination index, and significant reduction of pathogens, suggesting the agricultural relevance of composted SS and green/dry plant waste at 1:2 and 1:3 (v/v) proportions. pH and electrical conductivity were also within the permissible limits. With respect to international standards, it appears that composted SS and green/dry plant waste at 1:2 and 1:3 proportions pose no threat to soil or plant quality if used in agriculture or land restoration.
KeywordsCompost Soil amendment Semi-arid area Heavy metals Pathogens
This research was conducted with funding from the vice chancellery for research of Isfahan University of Medical Sciences (Research Project # 391442) as a part of a PhD dissertation. The authors wish to acknowledge Mr. Ghobadian, Mr. Rabierad, Mr. Amini, and Ms. Javadi from Isfahan Water and Wastewater Co. for technical support and Mr. Farrokhzadeh and Ms. Vahid Dastjerdy for their assistance in terms of supplying laboratory facilities for this research and for valuable advice.
- American Public Health Association (APHA). (2012). Standard methods for the examination of water and wastewater, 22nd edn. Washington DC.Google Scholar
- Chazirakis, P., Giannis, A., Gidarakos, E., Wang, J., & Stegmann, R. (2011). Application of sludge, organic solid wastes and yard trimmings in aerobic compost piles. Global NEST Journal, 13, 405–411.Google Scholar
- Farrell, J. (1993). Fecal pathogen control during composting. Science and Engineering of Composting, 282–300.Google Scholar
- Haug, R. T. (1993). The practical handbook of compost engineering. USA: Lewis Publishers.Google Scholar
- Tchobanoglous, G., Burton, F. L., & Stensel, H. D. (2003). Wastewater engineering treatment and reuse (4th ed., pp. 77–78). Noida: Tata McGraw-Hill.Google Scholar
- Thompson, W., Leege, P., Millner, P., Watson, M. (2001). Test methods for the examination of composting and compost. The United States Composting Council Research and Education Foundation. The United States Department of Agriculture.Google Scholar
- USEPA. (1995). A guide to the biosolids risk assessment for the EPA Part 503 Rule EPA. B32-B-93-005. Washington DC: United States Environmental Protection Agency Office of Wastewater Management.Google Scholar
- World Health Organization. (2006). WHO guidelines for the safe use of wasterwater excreta and greywater. World Health Organization.Google Scholar
- Zucconi, F., Pera, A., Forte, M., & De Bertoldi, M. (1981). Evaluating toxicity of immature compost. Biocycle, 22, 54–57.Google Scholar