Vermicomposting as an effective approach to municipal sewage sludge management through optimization of the selected process variables

Abstract

In most developing countries, municipal sewage sludge end-use practices appear unsustainable; rather, it poses environmental concerns. This study examined the potential of vermicomposting of municipal sewage sludge and its blend with other biowaste for agricultural application. Using a response surface methodology and the Box–Behnken design in Design Expert Software (Version 10.0.7), the current study optimized the moisture content (60–90%), turning frequency (1–3 turnings/week), and substrate mixing ratios (50:50 to 80:20 wt.%) to maximize the content of nitrogen, phosphorus, and potassium. As a result, an optimal moisture content (72%), substrate mixing ratio (72.34:27.6 wt.%), and turning frequency (2 per week), producing a promising-quality vermicompost with a maximum yield of nitrogen (2.76%), phosphorus (1.80%), and potassium (1.88%) is achieved. Thus, vermicomposting can effectively turn the concerning municipal sewage sludge into useful agricultural input for its sustainable management. HIGHLIGHTS Optimal vermicomposting conditions were achieved through parameter optimization, including moisture content, mixing ratio, and turning frequency.; High-quality vermicompost was harvested from municipal sewage sludge and amended with another biowaste (coffee husks and cow dung).; The physicochemical and microbial properties of the vermicompost were analyzed for use as organic fertilizer.;

Keywords

• coffee husks
• cow dung
• eisenia fetida
• municipal sewage sludge
• vermicomposting