Waste Heat Driven Integrated Membrane Distillation for Concentrating Nutrients and Process Water Recovery at a Thermophilic Biogas Plant

To efficiently utilize low-concentrate digestate nutrients, further treatment is needed to decrease their volume, recover process water, and increase nutrient concentrations. Membrane distillation (MD) a thermally driven that advantageous due its ability harness low-grade waste heat treat highly complex wastewater streams. This study assessed the techno-economic performance of integrating MD for two-fold concentrations nutrients recovery water from at thermophilic biogas plant. Thermal assessment showed recovered flue gas fully met thermal energy demand saved 20% boiler by heating incoming slurry. The permeate flux was 3.5 L/(m2h) 3.1 66 °C 61 inlet temperatures during winter summer, respectively. With internal recovery, specific 80 kWh/m3 100 in unit cost estimated be 3.6 €/m3 4.1 feed temperature (with recovery), 7.6 9.1 (without recovery) However, sensitivity analyses variations had significant impact on production cost. Nevertheless, economic indicated integration plant with industrial-scale capacity could economically feasible, being more favorable higher recovery.