Optimizing trickling filter Systems: Comparative analysis of integrated municipal wastewater treatment configurations within a biorefinery framework

Assessing the integration of trickling filter (TF) with various configurations, such as primary settling tanks (PST), microscreening (MS), and ion exchange (IE), is a valuable research endeavor. Most studies in the area of municipal wastewater treatment have researched components like PSTs and TFs individually. However, looking carefully through the literature reveals a limited comprehensive study focused on configurations like PST+TF, PST + MS + TF, or PST + MS + IE + TF. Given this gap, a pilot-scale study consisting of the two mentioned configurations along with the PST + TF system was set up at the water and wastewater research center of the University of Stuttgart, Germany, considering the worst-case scenario for temperature conditions and monitored intermittently over two years. The study was conducted under three different scenarios based on different biological loads, ranging from very high Organic and Nitrogen Loading Rate (OLR and NLR, respectively); S1 (OLR = 3.7 kg TCOD m⁻³ d⁻¹, NLR = 2.4 g NH₄⁺-N m⁻² d⁻¹), S2 (OLR = 3.0 kg TCOD m⁻³ d⁻¹, NLR = 1.4 g NH₄⁺-N m⁻² d⁻¹), down to very deficit, S3 (OLR = 1.5 kg TCOD m⁻³ d⁻¹, NLR = 0.5 g NH₄⁺-N m⁻² d⁻¹). Since the defined integrated system consists of energy and cost-effective methods like MS, IE, and TF, it can help to promote a biorefinery with sustainable process performance, particularly in terms of water reuse and resource recovery pathways. The results showed significant reductions in soluble chemical oxygen demand (SCOD), with SCOD removal efficiencies of 30 %, 50 %, and 70 % for S1, S2, and S3, respectively. Nitrogenous pollutant removal demonstrated enhanced nitrification at lower OLRs, with ammonium removal efficiencies of 20 %, 60 %, and 80 % across scenarios. Organic micropollutants (MPs) removal was also assessed under different scenarios, with results indicating that a maximum removal efficiency of 40 % is achievable under S3 (low-loaded scenario), as determined using SAK₂₅₄ (adsorption coefficient at a wavelength of 254 nm). These results demonstrate the TF system's capacity to effectively remove pollutants under even deficit loading conditions, making it an ideal choice for integrating energy-efficient technologies, such as MS and IE, for sustainable and cost-effective wastewater treatment.