Application of high rate nitrifying trickling filters for potable water treatment Ben van den Akker a, *, Mike Holmes b , Nancy Cromar a , Howard Fallowfield a a Department of Environmental Health and Flinders Research Centre for Coastal and Catchment Environments, Flinders University, Bedford Park, South Australia 5042, Australia b United Water International, 180 Greenhill Road, Parkside, South Australia 5063, Australia article info Article history: Received 7 May 2008 Received in revised form 27 July 2008 Accepted 30 July 2008 Published online 9 August 2008 Keywords: Nitrification Trickling filter Water treatment Chlorine demand Ammonia limitation Depth profile abstract The interference of ammonia with chlorination is a prevalent problem encountered by water treatment plants located throughout South East Asia. The efficacy of high rate, plastic-packed trickling filters as a pre-treatment process to remove low concentrations of ammonia from polluted surface water was investigated. This paper presents the findings from a series of pilot experiments, which were designed to investigate the effect of specific conditionsdnamely low ammonia feed concentrations (0.5–5.0 mg NH 4 -N L 1 ), variations in hydraulic surface load (72.5–145 m 3 m 2 d 1 ) and high suspended solid loads (51  25 mg L 1 )don filter nitrifying capacity. The distribution of nitrification activity throughout a trickling filter bed was also characterised. Results confirmed that high hydraulic rate trickling filters were able to operate successfully, under ammonia-N concentrations some 10- to 50-fold lower and at hydraulic loading rates 30–100 times greater than those of conventional wastewater applications. Mass transport limitations posed by low ammonia-N concentrations on overall filter performance were insignificant, where apparent nitrification rates (0.4–1.6 g NH 4 -N m 2 d 1 ), equivalent to that of waste- water filters were recorded. High inert suspended solid loadings had no adverse effect on nitrification. Results imply that implementation of high rate trickling filters at the front- end of a water treatment train would reduce the ammonia-related chlorine demand, thereby offering significant cost savings. ª 2008 Elsevier Ltd. All rights reserved. 1. Introduction The absence of water catchment protection often results in contamination of drinking water supplies. Waters in South East Asia have been exploited to support extensive agriculture, industry, power generation, public water supply, fisheries and recreation use. The sub-optimal condition of the catchments can be largely attributed to elevated concentrations of nutri- ents owing to the discharge of waste from both industry and bank-side residents without adequate pre-treatment (Bukit, 1995; Palupi et al., 1995; Cammarota, 2001; Mustika Sari, 2004). Erosion within these waterways during rainstorm events and the effects of high suspended solids (SS), which can vary between 30 and 200 mg L 1 , are an additional concern with respect to water quality (Cammarota, 2001). Low concentrations of ammonia (0.5–5.0 mg NH 4 -N L 1 ) have been identified as a significant contaminant of raw water because of its ability to affect the disinfection efficiency of chlorine (White, 1999; Mustika Sari, 2004). The interference of ammonia with chlorination is a prevalent and expensive * Corresponding author. Tel.: þ61 8 82043032. E-mail address: ben.vandenakker@flinders.edu.au (B. van den Akker). Available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/watres 0043-1354/$ – see front matter ª 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2008.07.038 water research 42 (2008) 4514–4524