Investigating the effect of co-vermicomposting of fecal sludge with jackfruit waste on the physio-chemical properties, nutrients, pathogens, and heavy metals of final compost.

Abstract

There is evidence of declining soil fertility in Uganda due to soil degradation and mining, making sustainable crop production difficult. Farmers need organic fertilizers like dewatered and dried fecal sludge (FS) to address microbial and chemical contamination. Co-vermicomposting of Fecal sludge with Jackfruit waste is a potential solution to ensure the production of organic fertilizer to ensure soil fertility. The objective of this study was to investigate the effect of co-vermicomposting on the physiochemical properties, nutrients, pathogens and heavy metals of fecal sludge and Jackfruit waste. Dewatered and dried fecal sludge was collected from National Water and Sewerage treatment plant, Lubigi. The Jackfruit waste was collected from Nakasero market (Kampala) and size reduced to about 5mm diameter using a shredder. The Shredded Jack Fruit (JF) was pre-composted for 14 days to reduce the acidic pH to nearly neutral or alkaline for vermicomposting. FS and JF was mixed in different proportions; 100FS:00JF, 75FS:25JF, 50FS:50JF and 25FS:75JF and then put in a 0.0282 m3plastic reactor. Eudrilus Euginea, an earthworm species was introduced into the reactor and the experiment was replicated three times, in two different runs i.e., R1 (first run) and R2 (Second run). At the end of 60 days, the vermicompost was harvested and assessed for the contaminant’s (pathogens and heavy metals) reduction and nutrient changes. The pathogens in both the substrates and the vermicompost that were analyzed included; Pathogens; Total coliforms, Escherichia Coli, Staphylococcus Aureus, and salmonella and heavy Metals namely; Mo, Zr, Sr, Rb, Pb, Zn, Cu, Fe, Mn, Cr, V, Ti, Sc, Ca, K, S, Bal, Nb, Al, P, Si, Cl, and Mg. The study showed a significant reduction in Escherichia coli, which was reduced to 0 CFU/g and Staphylococcus aureus reduced too. Salmonella was not detected initially in the substrates and neither in the vermicompost. There was a significant change (p<0.005) in heavy metal contents between the treatment combinations which varied from metal to metal. The nutrients K, C, ash content, and total solids significantly increased (p<0.05) after vermicomposting whereas pH, volatile solids, total solids, and N significantly decreased (p<0.05) with vermicomposting time and P was observed to vary between treatment combinations. In general, co-vermicomposting of fecal sludge and Jackfruit waste proved to be a better technology in contaminants reduction and maintaining nutrients.