Three-component adsorption modeling to evaluate and improve integrated sorption-membrane processes

Integrated sorption-membrane (ISM) processes combining low-pressure membranes with adsorbents are increasingly popular because they cost-effectively expand low-pressure membrane treatment to include dissolved contaminant removal. However, contemporary ISM processes often exhibit antagonistic tradeoffs between adsorption and membrane performance that were investigated using state-of-the-art adsorption models that include both of the predominant competitive effects of natural organic matter: direct site competition and pore blockage. Two currently used ISM process configurations, powdered activated carbon-ultrafiltration (PAC-UF) and adsorptive floc blanket reactor-ultrafiltration (FBR-UF), were compared with a novel configuration, upflow adsorption-ultrafiltration (UA-UF), which consists of a moving-bed of granular activated carbon upstream of a membrane. Model simulations quantitatively compared performance and evaluated potential improvements for each configuration. For instance, using contemporary PAC-UF practices and 90% atrazine removal as a baseline, alternative membrane backwashing procedures can lower carbon usage rates (CURs) by 75% but may also reduce membrane hydraulic performance. Using the same baseline, FBR-UF can reduce CURs by 92% while simultaneously improving membrane performance via pretreatment; however, process size increases 10-fold. The novel UA-UF configuration only increases process size modestly, but can still yield CURs 96% lower than the PAC-UF baseline while simultaneously providing beneficial membrane pretreatment and improving sustainability features by reducing residuals.