Valorization of fecal sludge stabilization via vermicomposting in microcosm enriched substrates using organic soils for vermicompost production

Rapheal Nsiah-Gyambibi; Helen Michelle Korkor Essandoh; Nana Yaw Asiedu; Bernard Fei-Baffoe

doi:10.1016/j.heliyon.2021.e06422

Valorization of fecal sludge stabilization via vermicomposting in microcosm enriched substrates using organic soils for vermicompost production

Heliyon. 2021 Mar 8;7(3):e06422. doi: 10.1016/j.heliyon.2021.e06422. eCollection 2021 Mar.

Authors

Rapheal Nsiah-Gyambibi¹, Helen Michelle Korkor Essandoh¹, Nana Yaw Asiedu², Bernard Fei-Baffoe³

Affiliations

¹ Regional Water and Environmental Sanitation Centre, Kumasi. Department of Civil Engineering, College of Engineering Kwame Nkrumah University of Science and Technology, UPO, Kumasi, Ghana.
² Department of Chemical Engineering, College of Engineering, Kwame Nkrumah University of Science and Technology, PMB, UPO, Kumasi, Ghana.
³ Department of Theoretical and Applied Biology, College of Science, Kwame Nkrumah University of Science and Technology, PMB, UPO, Kumasi, Ghana.

Abstract

High generation of fecal sludge without proper treatment is a major sanitation problem. A key step in curbing this problem is producing value-added resources such as vermicompost from fecal sludge through substrate enrichment. Substrate enrichment is a vermicomposting technique that involves augmenting vermibed substrates with organic rich materials to provide additional nutrients, as well as underlying layers needed for microcosm development to produce desirable vermicompost. The aim of this study was to investigate effects of substrate enrichment with organic soils (black soil, red laterite soil and sandy soil) combined with coconut coir as bulking material, on the fecal sludge vermicomposting process and quality of the end-product. The purpose of the study was to promote the development of highly nutritive vermicompost from fecal sludge using substrate enrichment as a low-cost innovative vermicomposting technique. The enriched substrates were prepared with 160g of coconut coir, 120g of fecal matter (65-70% dry matter) and 80g of organic soil. The treatments were labelled T₁, T₂ and T₃ representing systems containing black soil, red laterite soil and sandy soil respectively. The control treatment (T₄) contained no soil. Triplicate treatments were setup and about 20 3-week old clitellated earthworms of the species Eisenia. fetida with live weights ranging from 255 to 275mg, released into each system for vermicomposting over a period of 12 weeks. Physicochemical parameters such as pH, Organic Carbon (C_org), Total Nitrogen (N_tot), Available Phosphorus (P_avail), Exchangeable Calcium (Ca_exch), Iron (Fe), Lead (Pb) and Aluminium (Al) were determined for both the fecal sludge and the vermicompost. The vermicompost in the setup with black soil (T₁) showed the highest C_org mineralization and N_tot, P_avail and Ca_exch enhancement followed by T₂, T₃ and T₄. Treatment T₁ also resulted in the lowest concentration of Fe, Pb and Al in the vermicompost. Concentrations of these heavy metals were found to be higher in the other treatments in increasing order of T₂, T₃ and T₄. Less than 16% earthworm mortality was recorded in all treatments except T₄, in which the mortality was about 38% (38.33 ± 13.74). The enriched substrates were therefore found to provide a more suitable microclimate for earthworm development and produced vermicompost with high nutrient content. However, a more comprehensive study on metal accumulation in the earthworm tissues as a potential metal contaminant is needed to establish a strong hypothesis in the safe use of earthworms for this vermicomposting technique.

Keywords: Eisenia fetida; Enzymes; Fecal sludge; Substrate; Vermicompost.