The Study of Humic Substances' Impact on Anion Exchangers

Humic substances (HSs) present in water and wastewater cause fouling of anion exchange resins (AERs), which mainly results in reducing the ion exchange capacity (IEC). In this paper, an attempt was made to investigate fouling of two polystyrene and one polyacrylic AER using water from the Oder River, treated wastewater after the ultrafiltration process (UFTW) and digester reject water from sludge dewatering at the Janowek Wastewater Treatment Plant (WWTP) in Wroclaw. HSs contained in digester reject water were characterised by the lowest aromaticity and molecular weights (MWs), the highest proportion of hydrophilic fraction and the highest amount of oxygenated functional groups. The Fourier-transform infrared (FTIR) analyses made it possible to identify chemical bonds characteristic of HSs and determine the mechanism of their retention on the surface of AER beads. The conducted experiments brought unexpected results, as the IEC increased with the amount of organic matter in the feed. Presumably, the humic substances accumulated on the beads and in the porosity of the anion exchangers themselves participated in the ion exchange process.