Browsing by Author "Collin, Thomas Denis"

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    Assessing the potential of enhanced primary clarification to manage fats, oils and grease (FOG) at wastewater treatment works
    (Elsevier, 2020-04-20) Collin, Thomas Denis; Cunningham, Rachel; Asghar, Mohammed Qasim; Villa, Raffaella; MacAdam, Jitka; Jefferson, Bruce
    Daily, sewage treatment works (STWs) receive large volumes of fats, oils and greases (FOG), by-products of food preparation. To increase FOG removal at STW, conventional primary sedimentation tanks (PSTs) can be enhanced using chemical coagulant or through dissolved air flotation (DAF) techniques. This work aimed to assess the potential benefits of enhanced primary treatment for FOG removal through an energy and costs analysis. To achieve this, a five-year sampling programme was conducted monthly at 15 STWs measuring FOG concentrations in crude and settled sewage (i.e. after primary treatment). In addition, two DAF pilot systems were trialled for four months and their performance, in terms of FOG removal, was assessed and compared to that of a control primary clarifier. Across the 15 STWs, influent FOG concentrations were found at 57 ± 11 mg.L−1. Chemical coagulants dosed prior to PSTs increased FOG removal rates on average to 71% whilst traditional sedimentation only achieved 50% removal. Effluent FOG concentrations were found between 12–22 mg.L−1 and 19–36 mg.L−1 respectively. By contrast, DAF achieved FOG effluent concentrations on average at 10 ± 4 mg.L−1 corresponding to 74% removal from a relatively low influent concentration of 40 ± 30 mg.L−1. Thus, enhanced primary treatments have the potential to reduce organic load to secondary treatment and increase energy generation through anaerobic digestion. The overall net energy balance was estimated at 2269 MWh.year−1 for the DAF compared to 3445 MWh.year−1 for the chemically-enhanced PST making it a less financially attractive alternative. Yet, in the case where the works require upgrading to accommodate flow or load increases, DAF appeared as a sensible option over sedimentation offering significantly lower capital costs and footprint. In relation to FOG management, upgrading all STWs is not realistic and will require understanding where the benefits would be the highest.
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    Towards sustainable fats, oils and greases (FOG) management: from waste to resource.
    (Cranfield University, 2019-10) Collin, Thomas Denis; Jefferson, Bruce; MacAdam, Jitka
    Fats, oils and greases (FOG) are by-products of cooking and food preparation originating from households, food service establishments (FSEs) and industrial food facilities. Under UK legislation, industries are the only sources of FOG monitored by water authorities under trade effluent consents. In addition, whilst all FSE kitchens must be fitted with an “effective mean of grease removal”, experience within the water sector has demonstrated that very few premises were managing their effluents to minimise FOG emissions. Critically, large volumes of FOG are entering drainage systems resulting in impacts both in the sewers (formation of fatbergs) and downstream at the treatment works (reduced treatment efficiency), and in turn contributing to high operational costs for water utilities. With changing food habits and projected population growth, FOG-related problems will only become an increasingly worrying operational and financial burden for the water industry. Yet, FOG can be a valuable resource for energy recovery with the potential to offset operational costs and improve the overall sustainability of wastewater treatment. This thesis establishes an evidence base by assessing the potential of alternative FOG management options in order to provide guidance to water utilities for improving current practices. A comprehensive study identified the contribution of current kitchen practices to FOG emissions from domestic and commercial sources, suggesting the need for educational campaigns to raise awareness on the problem. Production rates and quality of FOG from different sources were benchmarked clarifying variations amongst these wastes. The potential of FOG for energy recovery, via biogas generation from anaerobic digestion, was assessed through laboratory-scale studies. The occurrence of FOG at the treatment works was investigated, and the performance of enhanced treatment for its removal was further studied. Finally, data produced during this project was used to develop a business case for the implementation of more sustainable approaches.