Techno-economic feasibility of “membrane-based pre-concentration + post-treatment” systems for municipal wastewater treatment and resource recovery

Membrane-based pre-concentration (MPC) process has been regarded as an attractive approach to sustainable municipal wastewater (MW) treatment. The aim of this study is to verify the techno-economic feasibility of pilot-scale MPC demonstrations and to design a complete technical route for MPC-based MW treatment and resource recovery. Three pilot MPC demonstrations (50–500 t/d) were operated for several months with different strategy combinations of chemicals and aeration. The filtration performance, pollutant removal performance, and concentrate characteristics were investigated and a techno-economic assessment was conducted. Based on the characteristics of each MPC effluent, biofilters, reverse osmosis (RO) and membrane capacitive deionization (MCDI) were selected as post-treatment units. Comparisons were carried out from 6 perspectives, including effluent quality, energy consumption, capital investment, operating cost, by-products, and recovery potential. In MPC_C, the combination of intermittent aeration and “50 mg/L Polyaluminium chloride +25 mg/L activated carbon” ensured a stable filtration (flux >10 LMH over 3 months) and an exceptional pollutant removal (soluble organics removal rate >75%) performance. The highest energy recovery potential (0.35 kWh/m3) was also achieved in MPC_C with the lowest energy consumption (0.12 kWh/m3) and an acceptable operating cost (0.53 CNY/m3). As for post-treatment units, RO showed advantages in effluent quality, technological maturity, and economic cost. An “MPC (intermittent aeration + high strength dosage) + RO + anaerobic digestion” system was proposed for synchronous water-energy reclamation. The net energy consumption and operating cost were estimated as 0.273 kWh/m3 and CNY 1.132/m3, respectively. This study will open new possibilities for the establishment of revolutionary wastewater treatment routes for carbon neutrality and sustainable development.