Operational performance and cost analysis of PAC/ceramic MF for drinking water production: exploring treatment capacity as a new indicator for performance assessment and optimization.

Abstract

A powdered activated carbon (PAC)/ceramic microfiltration (MF) pilot was operated (24/7) in a water treatment plant during 18 months, with water from different points of the treatment line (raw, ozonated with recirculated filter-backwash waters, ozonated/pre-coagulated, filtered), the testing including MF and PAC/MF. The optimization of PAC/MF operational performance, including PAC effect analysis and pretreatment required, and a cost analysis are herein presented. A new indicator was developed and explored for performance assessment and optimization, the treatment capacity (TCp), i.e. the design flowrate normalized to membrane area and intake pressure. As expected, a higher TCp was obtained with filtered water. Non-clarified waters required alum-coagulation pretreatment to minimize membrane fouling, and achieved similar TCp results among them. PAC addition (6-24 mg/L) did not promote membrane fouling and had no or a slight positive effect on TCp. TCp integrates all key aspects of process productivity and therefore constitutes a useful indicator to balance flux, energy consumption, backwash frequency and chemical cleaning frequency. The cost functions developed for PAC/MF yielded, for the best operating conditions found for the low-turbidity, low-dissolved organic content waters tested, a total cost of 0.07-0.11 €/m3 for 100,000 m3/d, including investment and operation costs.