The recycling of sewage sludge through agricultural lands has now resurfaced as one of the premier options for its disposal. Alkaline stabilization represents a feasible alternative for the transformation of these products into a stabilized pathogen-free material prior to their application to land. In this study, we evaluated the effectiveness of different mixing ratios of fly ash material to sludge in reducing pathogen levels and stabilizing a raw sewage sludge obtained from a treatment plant in Puerto Rico. The mixing ratios evaluated were: 2_1, 1:1, and 0.5:1 ash:siudge, calculated on a wet basis. Temperature and pH profiles for the first seven days after mixing were constructed on each case. Fecal coliform density was determined prior to mixing, and at 24 hours, 7 days, and 20 days «Liter mixing. In addition, the following parameters were measured: Total (Ca, Mg, Zn, Fe, Cu, Cd, Al,), available Ρ, NH4, NO3, electrical conductivity, moisture content, particle density, neutralizing value, organic matter content, and volatilization rate. Results indicate that the 1:1 mixture was more effective in achieving USEPA pathogen reduction standards. The chemical and physical properties of the resulting end-product make it a suitable liming agent with wide agricultural and industrial applications.


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