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CHALLENGES IN SLUDGE STABILIZATION: REGULATORY COMPLIANCE IN THE DESIGN AND OPERATION OF FACILITIES
Citation:
Tsang, K. R. AND J E. Smith* Jr. CHALLENGES IN SLUDGE STABILIZATION: REGULATORY COMPLIANCE IN THE DESIGN AND OPERATION OF FACILITIES. M.K. Banks (ed.), JOURNAL OF ENVIRONMENTAL ENGINEERING. American Society of Civil Engineers (ASCE), Reston, VA, 131(6):834-837, (2005).
Description:
Successful sewage sludge management involving the beneficial use of biosolids is predicated on acceptable quality of the product. Sludge quality can be defined in many ways. One of the most critical qualities affecting product marketability is sludge stability. While the terms "stabilization or stability" are not used in the Federal 40 Code of Federal Regulations (CFR) 503 regulations, for purposes of this paper, we define "stabilization" to mean any chemical, physical, or biological process that significantly reduces pathogens, odor, and ability to undergo putrefaction. (The federal regulation is only concerned with pathogen reduction and a reduction in vector attractiveness.) Sludge stabilization systems have been designed and operated in numerous wastewater treatment facilities around the country. Long before biological treatment of wastewater, lime was used to stabilize sludge and night soil. The practices or approach to sludge stabilization has since taken many forms, from the development of septic tanks to Imhoff tanks, to alkaline stabilization, thermal treatment, digestion, and other processes.
The goals of sludge stabilization as stated above include reducing pathogens and reducing the sludge's offensive characteristics. However, this objective is abstract and its achievement is difficult to quantify. Since the promulgation of the 40 CFR 503 regulations on sludge use and disposal, concerns have been raised on the adequacy of these regulations in protecting public health. Further questions have been raised regarding the ability of sludge stabilization systems to comply with the 40 CFR 503 regulations. This paper provides a general discussion of the sludge stabilization issues from design to proper operation from the design engineer's perspective.