Effect of Combined Vermicomposting and EM Solution on Sewage Sludge Nutrient Profile: A Temporal Study

Abstract

Effective management of sewage sludge remains a crucial environmental challenge mainly because of its high organic load and the loss of nutrients during composting. Traditional composting is often practiced extensively but lacks efficiency in nutrient stabilization and limited insights into temporal nutrient dynamics. This study addresses such limitations by proposing a dual composting approach combining the vermicomposting and Effective Microorganism (EM) solution, emphasizing the temporal evolution of nutrient profiles, namely, N, P, K to optimize nutrient stabilization. A thoroughly designed framework involving Dynamic Kinetic Modeling (DKM) was utilized to analyze nutrient transformations, resulting in critical parameters: mineralization constants and stabilization half-lives. Microbial and enzymatic profiling through 16S rRNA sequencing and enzymatic activity assays demonstrated that microbial contributions to nutrient dynamics are substantially interrelated with nutrient release pathways, such as the relationship of urease activity with ammonium-N, with R2=0.92. Furthermore, analysis of composition of substrates helped find the optimal sludge-to-green-waste ratios for maximum retention of nutrients and decomposition rates. Thus, higher retention of phosphorus (+20%) sets at a ratio of 2:1 was identified. Long-term soil fertility tests demonstrated the practical applicability of stabilized compost, with test crops showing a +30% yield increase and 70% improvement in nutrient use efficiency levels. Advanced techniques, including fractionation for mineralization-immobilization balances, and gas and leachate monitoring, minimized nutrient loss pathways (<10%<10\%<10% leachate loss). Stabilization indices like Humification Index (HI) confirmed compost maturity (HI=1.2 at 60 days) levels. This integrative approach drives forward our knowledge of nutrient stabilization as well as scales up solutions for sustainable waste management and agricultural productivity enhancements.