Assessment of two sludge stabilization methods in a wastewater treatment plant in Sotaquira, Colombia

Abstract

Wastewater sludge is a by-product of wastewater treatment; it is often employed in agricultural processes following appropriate microbiological stabilization. In this study, we evaluated two methods of sludge stabilization in the wastewater treatment plant of Sotaquira, Colombia. The two assessed stabilization methods were dewatcring on drying beds and alkaline stabilization. The stabilization through dewatcring on drying bed was carried out for five months. Alkaline stabilization was conducted for 96 hours with three concent calcium oxide, 7 %, 9 %, and 13 % w/w. Humidity, pH, organic carbon, hosphorus, organic nitrogen, fecal coliforms, somatic phages, total helminth eggs, and Salmonella sp. were monitored monthly for the sludge under dewatcring treatment and at 0, 12, 24 hours for sludge under alkaline stabilization treatment. Both treatments succcded in eliminating Salmonella sp. Helminth eggs were eliminated by alkaline stabilization, whereas it was reduced to one or zero helminth eggs with the dewatcring treatment. Somatic phages were eliminated with alkaline stabilization but were only reduced to 3.52 log CFU/g with the dewatcring method. Dewatcring on drying beds produced biosolids that can be used for soil restoration. Whereas alkaline stabilization produced biosolids that can be used for agricultural purposes. Alkaline stabilization with 9 % and 13 % calcium oxide ostensibly reduced nitrogen and phosphorus contents in the sludge, whereas 7 % calcium affected less the phosphorus concentration of the sludge. These results indicate that sludge dewatcring on drying beds is an effective sludge sanitation protocol to be in implemented in small wastewater treatment plants, such that in Sotaquira, Colombia.