Browsing by Author "Butterworth, Eleanor"

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    Assessing the potential for tertiary nitrification in sub-surface flow constructed wetlands
    (Taylor and Francis, 2016-06-10) Butterworth, Eleanor; Richards, Andrew; Jones, Mark; Dotro, Gabriela; Jefferson, Bruce
    The challenge of how to maintain or improve wastewater treatment performance without causing an excessive increase in energy or costs is increasingly focussed towards ammonia. On small sewage treatment works, solutions have historically been energy intensive: to divert waste to a larger plant, add a polishing step to the end of the process flow sheet or upgrade and replace upstream processes. Constructed wetlands (CWs) offer a low energy alternative to meet these challenges. This review explores oxygen transfer theory; nitrification performance of existing CW systems, and the key affecting factors to be considered when implementing the technology for tertiary treatment upgrades. Future perspectives include the use of artificial aeration and greater consideration of vertical sub-surface flow systems as they achieve the nitrification capacity in a smaller footprint than horizontal flow systems and, where suitable hydraulics permit, can be operated under very low energy demand.
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    Impact of aeration on macrophyte establishment in sub-surface constructed wetlands used for tertiary treatment of sewage
    (Elsevier, 2016-02-27) Butterworth, Eleanor; Richards, Andrew; Jones, Mark; Brix, Hans; Dotro, Gabriela; Jefferson, Bruce
    The effect of artificial aeration on plant growth in constructed wetlands in terms of above and below ground biomass and nutrient uptake of two macrophyte species Phragmites australis and Typha latifolia was carried out to provide quantitative, mechanistic evidence to support any differences between the plant species establishment. Pilot scale systems were built and supplied with different intensities of aeration and corresponding controls, with supporting evidence from two full scale operational sites. Results show T. latifolia was more impacted by aeration than P. australis when comparing against their respective non-aerated controls, evidenced in reduced height, growth rate and leaf length. However, the impact was less visible due to T. latifolia's faster growth rate compared to P. australis. Micro and macronutrient uptake by each species had no discernible pattern, preventing the identification of a definitive mechanism to explain the retarded growth. However, results suggest a synergy between iron and manganese may be at play.
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    Performance of four full-scale artificially aerated horizontal flow constructed wetlands for domestic wastewater treatment
    (2016-09-16) Butterworth, Eleanor; Richards, Andrew; Jones, Mark; Mansi, Gabriella; Ranieri, Ezio; Dotro, Gabriela; Jefferson, Bruce
    A comparison of the performance of four full-scale aerated horizontal flow constructed wetlands was conducted to determine the efficacy of the technology on sites receiving high and variable ammonia loading rates not yet reported in the literature. Performance was assessed in terms of ammonia and solids removal, hydraulic conductivity and mixing patterns. The capability of systems to produce ammonium effluent concentrations <3 mgNH4 + -N/L was observed across all sites in systems receiving variable loadings between 0.1 and 13.0 gNH4 + -N/m2 /d. Potential resilience issues were observed in relation to response to spike loadings posited to be due to an insufficient nitrifying population within the beds. Hydraulic conductivity and flow mixing patterns observed suggested deterioration of the reactor effective volume over time. Overall, the study demonstrates the efficacy of the technology where ammonium removal is required on small sites receiving high and variable flow rates, with adequate removal of organics and solids, but no significant benefit to the long term hydraulics of the system.
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    The use of artificial aeration in horizontal sub-surface flow constructed wetlands for tertiary nitrification
    (Cranfield University, 2014-03) Butterworth, Eleanor; Dotro, Gabriela; Jefferson, Bruce
    Increased treatment capability is required on small sewage treatment works to meet ammonium consents that are tightening to effluent concentrations of below 5 mg[Ammonical nitrogen (mg/L)] and in some cases as low as 0.5mg[Ammonical nitrogen (mg/L)] Optimisation of existing assets is preferential over the addition or expansion of the works to minimise associated costs and energy usage. Many small works in the UK currently employ horizontal sub-surface flow constructed wetlands (HSSF CWs) that have restricted capability to nitrify due to limited oxygen transfer and as such artificial aeration has been proposed as a potential upgrade technology. To assess the performance of the technology, full- scale sites were monitored in terms of ammonium and solids removal and hydraulic characterisation over 3 years. Supporting pilot studies were carried out to assess the effect of aeration on the planted vegetation and to determine optimum transfer efficiencies. Cont/d.