Impact of Media Aging on the Removal of Cryptosporidium in Granular Media Filters

Abstract

A study was conducted to assess the impact of media aging on Cryptosporidium parvum transport and retention in granular filters. Column experiments were conducted with sand, anthracite, and granular activated carbon (GAC) filters. All columns possessed an identical filter design and grain size distribution. Oocyst removal was evaluated with both new and aged media. The variation in performance among new media was attributed to the shape of the tested granular media and to the concentration of extractable metals on the surface of collector grains. Media aging significantly increased the treatment performance of sand (26%) and GAC (31%) but had no influence on the perfor- mance of anthracite. This enhanced performance of aged media correlated well with the extent of biofilm development. The best removal performance was observed with aged GAC (71 � 2%), which supported the highest amount of biomass according to polysaccharide and protein measurements. The results of this investigation are of particular interest because they suggest that media aging increases the removal of protozoan parasites in full-scale granular filters. DOI: 10.1061/(ASCE)EE.1943-7870.0000672. © 2013 American Society of Civil Engineers. CE Database subject headings: Water treatment; Filtration; Filters; Biofilm; Abatement and removal. Author keywords: Water treatment; Granular filtration; Media aging; Cryptosporidium; Biofilm.