Trickling Filter and Activated Sludge Integrated System for Nitrogen Removal from Municipal Wastewater

Abstract

Nitrogen-rich municipal wastewater poses significant environmental challenges due to its contribution to eutrophication, dissolved oxygen depletion, and deterioration of aquatic ecosystems. Effective nitrogen removal is therefore essential for sustainable wastewater management and compliance with environmental discharge regulations. The present study investigates the performance of an integrated trickling filter and activated sludge system for nitrogen removal from municipal wastewater under varying operational conditions. The research focuses on evaluating organic matter degradation, nitrification–denitrification efficiency, biomass activity, and overall treatment stability associated with combined biological treatment processes. Experimental analysis was conducted to examine the influence of hydraulic retention time, aeration intensity, recirculation ratio, organic loading rate, and microbial population dynamics on nitrogen transformation and pollutant removal performance. Results demonstrate that the integrated treatment system effectively combines attached-growth and suspended-growth biological mechanisms to enhance ammonia oxidation and nitrate reduction processes. The study further reveals that optimized operational parameters significantly improve nitrification efficiency in the trickling filter stage while promoting denitrification and organic removal within the activated sludge process. Enhanced microbial diversity and stable biomass development contributed to improved nitrogen conversion efficiency and operational resilience under fluctuating wastewater loading conditions. Comparative assessment with standalone biological treatment systems confirms the advantages of integrated configurations, including improved treatment efficiency, lower sludge production, and enhanced process stability. In addition, the system demonstrated suitability for large-scale municipal wastewater treatment applications with reduced environmental impact.