Personal reflections of a 1st year postgraduate student

Undertaking a postgraduate research degree can be a very exciting and daunting experience. The aim of this paper is to relate some of the experiences and reflections of a first year postgraduate engineering student. There have been other articles written on the PhD experience, however I believe that this paper offers insights into the industry based project experience, the benefits and drawbacks of multiple supervisors, and it offers the perspective of a student on an early point of the postgraduate learning curve

A detailed study of desalination exergy models and their application to a semi-conductor ultra-pure water plant

Ultra-Pure Water (UPW) is a high energy raw material used in the semiconductor manufacturing industry. However, to date, the production of UPW has received little focus in terms of energy consumption mitigation. Exergy analysis is perhaps the most powerful tool available in the search for industrial energy efficiency. The objective of this research was to develop an approach for the exergy analysis of Semiconductor UPW plants in an effort to characterise energy consumption. However, following an extensive literature review, it became evident that several desalination exergy models were in current use, and it was unclear which model was the most appropriate, presenting a serious challenge to researchers seeking to apply exergy analysis to water purification processes. A detailed study and comparison of two predominant desalination exergy models was undertaken to determine the most appropriate model for UPW and other water purification applications. Neither of these models was deemed suitable due to inappropriate underlying model assumptions. Two potentially suitable exergy calculation models were identified from the broader literature and developed further for UPW applications. A novel method (based on Szargut’s chemical exergy reference environment) was developed to calculate the chemical exergy of electrolytic solutions at non-standard dead state temperatures. It was found that, in general, the chemical exergy of ionic species was sensitive to changes in dead state temperature. The exergy models were applied to a UPW plant in an effort to compare the models and characterise the plant. In general, the exergy destruction rates were similar for the three models, the hot water heat exchanger being the main exception (and also a key source of exergy destruction). Chemical exergy proved vital for the calculation of several process exergetic efficiency values and the assessment of plant exergy losses. Following a detailed assessment of the UPW plant exergy analysis results, the most appropriate model was identified

Modelling the activity of seawater and implications for desalination exergy analyses

Exergy analysis has been applied to desalination membrane processes in an effort to characterise energy consumption and to optimise energy efficiency. Several models have been used to this end in the literature. One assumption that is common in these analyses is that of ideal solution behavior. However, seawater and other aqueous solutions of interest do not behave ideally. Indeed, even when ideal behavior is not assumed, there are several approaches to calculate these activity values, which are typically a function of the molality and ionic strength of the electrolytic solution. What is not clear from the published literature is the impact that the choice of activity calculation model has on the exergy analysis results. The objective of this research was to undertake the exergy analysis of a seawater membrane desalination plant using the Szargut chemical exergy approach and to compare the activity calculation approaches. The chemical exergy of the seawater was calculated using several activity coefficient modelling approaches including, (a) ideal mixture model, (b) the Debye-Huckel limiting law, (c) the Davies model, and finally, (d) the Pitzer model, which is more appropriate for higher ionic strength solutions such as seawater. The results showed considerable differences in the chemical exergy rates and the magnitude of chemical exergy destruction rates calculated using the various models. For example, there were percentage differences of 61.8% and 44.7% between the magnitude of chemical exergy destruction rates calculated using the Pitzer model when compared with the Debye-Huckel limiting law for the nanofiltration and reverse osmosis processes respectively

Design and implementation of a resource consumption benchmarking system for wastewater treatment plants

Energy and water are inextricably linked, and together they are the two of the most valuable global resources. Internationally, the links between the energy, wastewater and water sectors are attracting increasing attention. In the wastewater sector, pressures including increasingly stringent environmental regulations and greater volumes of wastewater being produced and treated are a major challenge. These challenges mean that, without intervention, wastewater treatment facilities will become more resource intensive and may increasingly exceed environmental requirements, such as discharge limits. These issues are set against the backdrop, in many countries, of an emphasis on cost reduction and increased concerns regarding sustainability of the sector. Thus it is imperative that tools and methodologies are developed that allow the wastewater sector to measure resource efficiency, benchmark its performance in a standardised and efficient manner and identify cost-effective measures that can improve plant performance. This research presents a novel resource benchmarking system for wastewater treatment plants (WWTPs). This toolkit is designed to be easily implemented and effective in enabling benchmarking of WWTPs with varying capacity, technology, sampling frequency and management practices. The research considers both centralised and decentralised facilities (manned and unmanned) and investigates the challenges of benchmarking plants where routine monitoring is sporadic

Impact of rainfall events on the electricity consumption of two wastewater treatment plants

Focus on the Energy/Water Nexus has led to interest and increased research activity into the relationship between water and society and understanding the energy requirement of Wastewater Treatment Plants (WWTPs) will be a key part of future development. Using wastewater treatment plant data the aim of this paper is to study the relationship between the energy requirements for Wastewater Treatment (WWT), with particular focus on the impact of Wet Weather Flows (WWFs). It has been established from the literature that the efficiency of treatment plant processes drops during these events and, should treatment works be subject to increased energy requirements during WWFs, this will have an impact on any benchmarking effort. Using linear regression, a potential link between increased flows to treatment and electricity consumption of one WWTP in Northern Ireland has been shown, while a second possible link is established between the catchment area rainfall and increased flows to treatment for two WWTPs, which was found to be consistent with previous work in the literature

The use of exergy analysis to benchmark the resource efficiency of municipal waste water treatment plants in Ireland

Exergy Analysis has been identified in the literature as a powerful tool to benchmark the resource efficiency of thermal systems. The exergy approach provides a rational basis for process optimisation, where, in theory, the processes with the greatest exergy destruction represent the greatest energy efficiency opportunities. Exergy analysis of a Waste Water Treatment Plant (WWTP) has been performed. In addition, two separate reference environments for WWTPs are defined based on plant location. Biological oxygen demand was identified as the most useful parameter when calculating the chemical exergy of organic matter in waste water. The results of this study indicate that organic matter is the principal contributor to chemical exergy values and that exergy analysis is a useful approach to identify inefficient processes within a WWTP

An optical colour sensor to monitor the marine environment

This research aims to develop a flexible, simple, low-cost, robust, deployable sensor with anti- fouling measures to detect colour change in marine environments. Such a sensor could be used to detect events, inform sampling regimes in coastal areas and act as a qualitative decision support tool. This is useful to decision makers in cities, coastal areas and globally and as gathering data can be expensive using commercial instruments a low cost sensor enables more data to be collected with a better spatial range and resolution. Detecting colour change in water could give warning of events like green tides, e.g. (right) in QuingDao, China, often caused by cyanobacteria