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

Abstract

Wastewater sludge is a by-product of waste water treatment; it is often employed in agricultural processes following appropriate microbiological stabilization. In this study, we evaluated two methods of sludge stabilization in the waste water treatment plant of Sotaquirá, Colombia. The two assessed stabilization methods were dewatering on drying beds and alkaline stabilization. The stabilization through dewatering on drying bed was carried out for five months. Alkaline stabilization was conducted for 96 hours with three concentrations of calcium oxide, 7%, 9%, and 13% w/w. Humidity, pH, organic carbon, phosphorus, organic nitrogen, fecal coliforms, somatic phages, total helminth eggs, and Salmonella sp. were monitored monthly for the sludge under dewatering treatment and at 0, 12, 24 hours for sludge under alkaline stabilization treatment. Both treatments succeded in eliminating Salmonella sp. Helminth eggs were eliminated by alkaline stabilization, whereas it was reduced to one or zero helminth eggs with the dewatering treatment. Somatic phages were eliminated with alkaline stabilization but were only reduced to 3.52 log CFU/g with the dewatering method. Dewatering 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 dewatering on drying beds is an effective sludge sanitation protocol to be implemented in small waste water treatment plants, such that in Sotaquirá, Colombia.

Parasitological Assessment of Sewage Sludge Samples for Potential Agricultural Reuse in Tunisia

“…According to Capizzi and Schwartzbrod [10], the establishment of a maximum concentration of viable eggs of helminths in sewage sludge is a worldwide criterion for agricultural reuse of sewage sludge. The recommended maximum contents of intestinal parasites in sewage sludge for agricultural reuse set by several countries are summarized in Table 1 [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28].…”

The Efficiency of Ascaris Spp. Eggs Inactivation in Sewage Sludge by Lime Dosage, Ammonia Concentration, and Temperature Variation

“…Alkaline stabilization has been proven to reduce helminth eggs to one or zero with sludge dewatering treatment in Colombia. Alkaline stabilization also produces biosolids that can be used as fertilizers (21). Lime treatment increases the dehydration of sludge, temperature, and alkalinity, which contributes to sludge disinfection.…”

Biosolids as fertilizer in the tomato crop

“…For biosolids, ABIMGRA, Naturcomplet®-G, and greenhouse soil, the total concentrations of heavy metals (As, Cd, Cu, Cr, Mo, Ni, Pb, Se, Hg and Zn) were analyzed by extraction acid and quantified by atomic absorption spectrometry (EPA, 1996). Soil organic carbon (ICONTEC, 2006), available phosphorus (García & Ballesteros, 2006), total nitrogen (TC WI: 2003 E), pH (EPA, 2004), electrical conductivity (EPA, 1982), soil humidity (ICONTEC, 2013), fecal coliforms (Castellanos et al, 2020), Salmonella sp., (EPA, 2006), helminth eggs (Rachel & Duncan, 1996), and somatic phages (Lasobras et al, 1999) also were determined.…”

“…The wastewater treatment plant located in Sotaquirá, Boyacá, Colombia produces 109 tons of sludges per year. The sludges of Sotaquirá have been stabilized by alkalization and dehydration in the drying bed (Castellanos et al, 2020). The microbiological and physicochemical characterization of these biosolids suggests potential agricultural use due to their high content of total organic matter and low levels of heavy metals (Castellanos et al, 2018).…”