Polyurethane foam filter/PAC Adsorber

Abstract

Stage 1 of the Disinfection/Disinfection‐Byproducts Rule and the Interim Enhanced Surface Water Treatment Rule require better removal of turbidity and total organic carbon (TOC) from drinking water. Activated carbon adsorption is one method that can be used to remove natural organic matter (NOM) from drinking water in order to reduce the production of disinfection byproducts, but using granular activated carbon (GAC) is expensive. This article proposes using a polyester polyurethane foam filter (whose high porosity enables significantly higher filtration rates than those of conventional granular media filters) at a velocity similar to that of fuzzy filters. The filter could be used as a prefilter when clarification does not provide the desired level of turbidity removal, and because of its low head loss, it may fit within an existing treatment plant's hydraulic profile. In addition, the filter could be loaded with powdered activated carbon (PAC) and used as an adsorber. Because PAC is considerably less expensive than GAC, this process could reduce the cost of the adsorption process if the PAC usage approximates that of GAC. The proposed filter/adsorber exhibits a low head loss and requires a shorter contact time than a conventional fixed‐bed GAC adsorber; it should therefore also reduce energy costs and space requirements. To demonstrate the concept, the filter is used to remove turbidity with three different foams at varying degrees of compression with the filter's clean‐bed head loss also monitored. The filter/adsorber concept is tested using PAC to remove NOM (as measured using ultraviolet absorbance at 254 nm (UV254), demonstrating that a fixed‐bed break‐through curve results.