The Urban Wastewater Treatment Directive 91/271/EEC introduced a series of measures for the purpose of protecting the environment from the adverse effects of effluent discharge from wastewater treatment plants. There are environmental costs associated with attaining the required level of water quality set out in the directive such as greenhouse gas emissions due to energy production, and ecotoxicity from sludge application to land. The goal of this study is to assess the environmental costs in an Irish context, focusing specifically on the effects of variation in scale and discharge limitation. Life cycle assessment is the analytical tool used to evaluate the environmental impact. The life cycle impact assessment methodology developed by the Centre of Environmental Science, Leiden University (2010) has been adopted and implemented using GaBi 6.0 life cycle assessment software. Two plants of varying size and location were chosen for the study. The study found that energy consumption and sludge application to land are the largest contributors to the overall environmental impact associated with the treatment process at both plants. Economies of scale were observed in energy usage during secondary aeration.

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Hydrophobic membrane contactors represent a promising solution to the problem of recycling ammoniacal nitrogen (N-NH4) molecules from waste, water or wastewater resources. The process has been shown to work best with wastewater streams that present high N-NH4 concentrations, low buffering capacities and low total suspended solids. The removal of N-NH4 from rendering condensate, produced during heat treatment of waste animal tissue, was assessed in this research using a hydrophobic membrane contactor. This study investigates how the molecular composition of rendering condensate wastewater undergo changes in its chemistry in order to achieve suitability to be treated using hydrophobic membranes and form a suitable product. The main objective was to test the ammonia stripping technology using two types of hydrophobic membrane materials, polypropylene (PP) and polytetrafluoroethylene (PTFE) at pilot scale and carry out: (i) Process modification for NH3 molecule removal and (ii) product characterization from the process. The results demonstrate that PP membranes are not compatible with the condensate waste as it caused wetting. The PTFE membranes showed potential and had a longer lifetime than the PP membranes and removed up to 64% of NH3 molecules from the condensate waste. The product formed contained a 30% concentrated ammonium sulphate salt which has a potential application as a fertilizer. This is the first demonstration of hydrophobic membrane contactors for treatment of condensate wastewater.

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Wastewater treatment plants (WWTPs) typically operate continually and are subject to a number of pressures (e.g. population changes, varying influent due to storm water, more stringent environmental regulation etc.), making the implementation of resource efficiencies uniquely challenging. These challenges mean that, without intervention, WWTPs will become more resource intensive as they strive to meet environmental regulations. These challenges are set against the backdrop, in many countries, of an emphasis on cost reduction and increased concerns regarding the economic sustainability of the sector. Thus it is imperative that tools and methodologies are developed that allow the wastewater sector to measure resource efficiency and benchmark performance in a standardised and efficient manner. This can identify cost-effective measures that can improve WWTP performance. Measured data in WWTPs often contains errors that can greatly reduce the benefits of various performance assessment techniques. Existing benchmarking systems can offer detailed analysis of many aspects of wastewater treatment; however, these systems do not offer a means of assessing the accuracy of the data used for benchmarking. Furthermore, many benchmarking systems lack key performance indicators that focus on resource consumption and regulation performance. This paper presents a unique benchmarking methodology for WWTPs which addresses these challenges; enabling stakeholders to (i) benchmark a wide variety of WWTPs in an efficient and standardised manner (ii) identify data accuracy issues, (iii) isolate where and how resources are consumed in a WWTP and (iv) identify potential resource consumption mitigation measures. The methodology is implemented in a toolkit which is designed to be easily executed and effective in enabling benchmarking of WWTPs with varying capacity, technology, sampling frequency, data accuracy and management practices.