Evaluation of an emerging water treatment technology: ceramic membranes

Historically, low-pressure membranes (microfiltration (MF) and ultrafiltration (UF)) used in potable water treatment are made of polymers (polysulfone (PS), polypropylene (PP), polyethersulfone (PES), polyvinylidene fluoride (PVDF) etc). Recently, membranes made of ceramic materials (aluminium oxide) have been developed by MetaWater (Japan), Kubota (Japan) and others and is being marketed in the United States (US) by Krüger, Inc. (Cary, NC). Ceramic membranes offer several potential advantages over polymeric membranes, including higher mechanical robustness and ability to handle higher loading of particulates, higher resistance to oxidants and membrane cleaning chemicals, higher membrane integrity, longer service life and compact footprint. The authors conducted collaborative evaluations of this emerging technology at two different places; (i) Elm Fork Water Treatment Plant (WTP) of Dallas Water Utilities (DWU), Dallas, Texas, USA and (ii) Graham Mesa WTP, City of Rifle, Rifle, Colorado, USA. The evaluations included pilot testing of ceramic membranes in direct filtration mode (i.e. without clarification) and with coagulant addition. The water streams that were pilot tested at Elm Fork WTP included Trinity River water, spent filter backwash wastewater and lagoon recycle water (spent filter backwash water combined with clarifier blow down water). The City of Rifle pilot testing was conducted on Colorado River water. This paper presents the key results of these two pilot studies. Results of pilot testing were used to define the potential membrane flux, backwash protocols (interval and duration), chemical enhanced backwash (CEB) and clean-in-place (CIP) protocols. Pilot test results and engineering judgment were used for developing concept-level sizing and outlining parameters for future evaluation. This paper will discuss the key technical and economic considerations of the emerging treatment technology and its potential applications for potable water treatment. This paper will be of interest to water providers that are considering alternatives to treat challenging source waters (waters with high particulates and under heavy microbial influence), build new compact water treatment plants, increase plant capacity through membrane retrofits and treat recycle streams at existing WTPs.