Treatment of discontinuous emission of sewage sludge odours by a full scale biotrickling filter with an activated carbon polishing unit F. Sempere, P. Winter, A. Waalkens, N. Hühnert, I. Cranshaw, B. Beigi and R. B. Thorpe ABSTRACT A SULPHUS TM biotrickling filter (BTF) and an ACTUS TM polishing activated carbon filter (ACF) were used at a wastewater treatment plant to treat 2,432 m 3 ·h 1 of air extracted from sewage sludge processes. The project is part of Thames Water’s strategy to reduce customer odour impact and, in this case, is designed to achieve a maximum discharge concentration of 1,000 ou E ·m 3 . The odour and hydrogen sulphide concentration in the input air was more influenced by the operation of the sludge holding tank mixers than by ambient temperature. Phosphorus was found to be limiting the performance of the BTF during peak conditions, hence requiring additional nutrient supply. Olfactometry and pollutant measurements demonstrated that during the high rate of change of intermittent odour concentrations the ACF was required to reach compliant stack values. The two stage unit outperformed design criteria, with 139 ou E ·m 3 measured after 11 months of operation. At peak conditions and even at very low temperatures, the nutrient addition considerably increased the performance of the BTF, extending the time before activated carbon replacement over the one year design time. During baseline operation, the BTF achieved values between 266–1,647 ou E ·m 3 even during a 6 day irrigation failure of the biofilm. F. Sempere (corresponding author) A. Waalkens Pure Air Solutions, P.O. Box 135, Heerenveen 8440 AC, The Netherlands E-mail: f.sempere@pureairsolutions.nl P. Winter N. Hühnert Thames Water, Innovation Centre, Reading STW, Island Rd, Reading RG6 0RP, UK I. Cranshaw MWH UK Ltd (Part of Stantec), Buckingham Court, Kingsmead Business Park, London Road, High Wycombe HP11 1JU, UK B. Beigi R. B. Thorpe Department of Chemical and Process Engineering, University of Surrey, Guildford GU2 7XH, UK Key words | activated carbon, biological air treatment, biotrickling filter, hydrogen sulphide, nutrient limitation, sludge odour INTRODUCTION The treatment of odour pollutants released from wastewater processes by biofilters and biotrickling filters (BTFs) are a proven technology (Shammay et al. a). Already in Germany in the late 1980s biofiltration was a more common technology than chemical scrubbing, due to its high efficiency achieved with slightly lower capital invest- ment and operating costs (Frechen ). Indeed, not even 20 years later industrial chemical scrubbers were success- fully refurbished into BTFs for hydrogen sulphide (H 2 S) and odour abatement in wastewater treatment plants (WWTPs) in the United States (Gabriel et al. ). This work showed that BTFs can treat inlet H 2 S concentration fluctuating between 5 and 40 ppmv at empty bed residence times (EBRTs) of 1.8–2.2 s with outlet H 2 S concentrations below 0.8 ppmv. The authors also estimated savings in chemicals and electricity in the range of $10,000–50,000 per year per scrubber, depending on the H 2 S loading. An additional advantage is chemical-free odour treatment, yielding worker health and safety advantages as a result of not using hazardous chemicals. Thames Water operates an estate of approximately 116 odour control units, the majority of them operating with BTFs or biofilters. BTFs with plastic media have a clear advantage against biofilters packed with organic materials when operational costs in the whole life costs of the odour control biotechnol- ogies are considered. When H 2 S is present in the air, the chemoautotrophic bacteria immobilised on the media of BTFs use H 2 S as their energy source, oxidising it to sulphu- ric acid, thereby fixing carbon dioxide as a carbon source for growing. Genus Thiobacillus includes acidophilic bacteria able to grow at the low pH values of the biofilms treating H 2 S-polluted streams (Smet et al. ). These acidic 2482 © IWA Publishing 2018 Water Science & Technology | 77.10 | 2018 doi: 10.2166/wst.2018.203 Downloaded from http://iwaponline.com/wst/article-pdf/77/10/2482/234973/wst077102482.pdf by guest on 24 March 2023