Operating cost reduction of UF membrane filtration process for drinking water treatment attributed to chemical cleaning optimization

Abstract

This study investigated the cost and CO₂ emission reduced as a result of optimizing operating conditions for chemical cleaning in a membrane filtration process used for water treatment. A new protocol was proposed and operating conditions for chemical cleaning of a pilot-scale membrane filtration process were optimized. The critical flux for irreversibility was identified as the permeate flux using a modified flux-step method, and was 100 l m^-2 h^-1, 20 l m^-2 h^-1 higher than the vendor recommended permeate flux. NaOCl, which is also the vendor recommended chemical, was selected as the optimal chemical reagent following an examination of the permeability restoration ratios and nature of the irreversible foulants. The optimized operating conditions of enhanced flux maintenance (EFM), determined using response surface methodology (RSM) were: 6.3 d interval, 500 ppm concentration, and 76 min duration, which represented an increase of 4.3 d, 300 ppm, and 36 min, respectively, as opposed to the vendor recommended conditions. As a result, the total operating cost and CO₂ emission were $0.1187/m³ and 112.75 g CO₂/m³, respectively, and 26.5% lesser compared to the operating cost and CO₂ emission based on vendor recommended conditions. This study found that the reductions in operating cost and CO₂ emission using the optimization process were excellent.

Keywords: Chemical cleaning optimization; Enhanced flux maintenance; Irreversible fouling; Operating cost reduction; Response surface methodology.