Filtration Characteristics of Pressure-Driven Membrane Processes for the Purification of Aeration Station Sludge Leachates from Heavy Metals

Abstract The development of efficient pressure-driven membrane systems for the purification of contaminated waters from mixtures of heavy metals (HMs) is still a relevant scientific challenge due to the increasing volumes of industrial and municipal wastewaters, the limited efficiency of conventional methods for their purification from complex contaminants, and the requirements of UN Sustainable Development Goals by 2030 to safe wastewater treatment. The efficiency of the baromembrane filtration of contaminated solutions is provided by the combination of high selectivity and separation productivity. The key parameters of these processes are the retention coefficient and volume flux (specific productivity), which depend on the transmembrane pressure, the composition of an initial solution, and the material, pore size, and fouling characteristics of a membrane. In this study, the specific productivity of ultrafiltration and nanofiltration polymeric membranes was investigated in the treatment of solutions obtained after the reagent leaching of wastewater sludges from municipal water treatment plants from ions of heavy metals (HM) (Cd2+, Cr6+, Cu2+, Ni2+, Pb2+, Zn2+) and their mixtures in long-term experiments. The regularities of stabilization in volume fluxes and membrane retention coefficients in the studied processes were established. It is shown that the combination of complexation (for polyethyleneimine as an example) with pressure-driven membrane processes (ultrafiltration and nanofiltration) ensures the effective purification of wastewater sludges from the Bortnychi Aeration Station from HM (Cd, Cr, Cu, Ni, Pb, Zn) mixtures to the levels below the maximum permissible concentrations for all studied metals. The obtained data may be a basis for selecting optimal baromembrane systems for the treatment of real industrial wastewaters.