An innovative thermo-hydraulic ultrafiltration process for solar application: experimental performances

Membrane ultrafiltration (UF) is an effective solution for separating pathogenic micro-organisms (bacteria, viruses and protozoa) from surface water. The pumping and pressurization of the water to be treated, necessary for ultrafiltration, are generated by a thermal energy input simulating the operation of a flat-plate solar collector. The process consisted of a modified organic Rankine cycle (ORC-like), two bladder tanks, a hydraulic complex with two double-acting cylinders and a UF membrane module. Experiments are conducted under controlled conditions with a hot thermal source fluctuating between 40 and 60 °C, while the ORC cold source varied between 20 and 40 °C. Energy variations typical of a solar day were reproduced under controlled conditions. Specific thermal energy consumption (SEC_th) was measured, with values ranging from 3.5 to 6.5 kWh_th·m⁻³. A dynamic numerical model was developed, based on enthalpy, heat and mass balances, the membrane transfers law and experimental correlations. After validation of the model, with an average deviation of 5 % on key process flows and pressures, a solar collector was integrated to simulate the performance of a solar thermal ultrafiltration process. For operating conditions in September in the south of France, a SEC_sol of between 7.7 and 8 kWh_sol·m⁻³ was estimated, in sunny and cloudy days.