No description available.

No description available.

This research is concerned with the use of techniques of system analysis/operations research in the selection of the optimal - or most appropriate - wastewater treatment techniques in any given situation. An extensive investigation of existing treatment system optimization models, applying techniques of linear programming, dynamic programming and non-linear mathematical programming, has been carried out. None of these existing models deals with the socio-cultural and environmental conditions but merely with the economy of treatment. In this work the more subjective or intangible factors are included in the proposed optimization model in which twenty parameters are identified. These parameters are considered to be most important in the selection of appropriate alternatives for treating municipal wastewater. They include technical, economic, environmental and socio-cultural factors. The model was developed to rank a definite number (n) of wastewater treatment alternatives (decision variables) by the evaluation of the twenty parameters [ ... continues].

Technetium, as technetium -99, is present in environmental waters as a result of radioactive effluent discharges from nuclear installations. It is necessary to be able to measure aqueous technetium levels if accurate models are to be developed to predict the long term effects of technetium releases on man. As natural waters contain little -3 technetium, less than μg dm-3 ,relatively large samples are required ( >500 cm3). A method has been developed in which the technetium in the sample can be rapidly concentrated onto an anion-exchange column after the removal of ruthenium isotopes by a precipitation procedure. Further decontamination is achieved by washing the anion-exchange resin with sodium hydroxide prior to removing the technetium with sodium thiocyanate. The bulk of the concentrated technetium (> 75%) can be removed from the resin into less than 15 cm 3 of eluent and further concentration is achieved by extracting the technetium into butan-2-one. The butan-2-one can be evaporated onto a planchette and the technetium levels determined by measuring the amount of B-radiation emitted from the final concentrate. The method has been shown to be capable of removing between ca. 10-15 g and 10 -6 g of technetium from 500 cm 3 of water and has been used successfully with samples ranging from natural waters to nuclear installation effluent. Technetium in natural waters may be lost from solution onto soils and this has important consequences if environmental technetium levels are to be measured. Experiments have been carried out to investigate Some of the factors which influence technetium sorption onto soil and microbial action has been shown to play an important role in determining the rate at which technetium is lost from solution. Other parameters found to affect technetium sorption onto soil include the chemical form of the technetium and the type of water used in the experiment.

For decades microbial fuel cells (MFCs) have offered the potential to treat wastewater while concomitantly producing power, but to date scale-up has not been achieved. The goal for this thesis was initially to explore the capabilities of MFCs in the laboratory and then to test the technology in the wastewater treatment environment. The aim was to operate the demonstrator in an existing process, without altering infrastructure or adding extra energy (Le. pumping). Laboratory work yielded novel findings helping to achieve the thesis objective while also contributing to MFC knowledge. Investigations into the anodic development period revealed that inoculating while in continuous-flow primed MFCs for operation in conditions of high flow-rate. The phenomenon 'power overshoot' was described and its occurrence explained in terms of the internal resistance of the MFC. A new miniature tubular MFC was designed and up to seven units were connected in fluidic series (cascade) to mimic the trickling filter process. These efficiently removed up to 90% COD, to levels that comply with European guidelines. The influence that fluidic connection had on MFCs in terms of flow-rate and external resistance was described for the first time. To mimic hostile flocculating conditions, MFCs were fed feedstock with varying ferric chloride concentrations. Power production, COD treatment, metal reduction and increased pH were all achieved suggesting the technology could supplement and improve existing processes. Utilising experience gained in the laboratory and following visits to Wessex Water, the trickling filter was selected as test location for the demonstrator. Using a variation on the novel tubular design, under field conditions at the Saltford treatment plant, MFCs demonstrated the ability to produce power while reducing COD to levels acceptable for release into the environment. These results strongly support the hypothesis that MFCs are becoming ready to be incorporated into the wastewater treatment process.

The removal of low concentrations of aqueous phase organics using adsorptive techniques has traditionally used high capacity adsorbent materials, for example activated carbons. The drawback of these materials is that regeneration can be costly and complex. An alternative approach reported in this thesis involves the use of a highly conductive material, a graphite intercalation compound (GIC), as an adsorbent. This material, which has been shown to be non-porous with a low surface area, is capable of electrochemical regeneration. This electrochemical regeneration is achieved by the oxidation of the organics in the anodic compartment of a simple, divided cell. In comparison with activated carbons, it has been demonstrated that adsorption is quick, with up to 88% of equilibrium loading being achieved within 2 minutes. 100% electrochemical regeneration can be achieved in a simple divided electrochemical cell with 10 minutes treatment, by passing a charge of 25 C g-1. The efficiency of electrochemical regeneration depends on a range of variables including charge passed, current density, treatment time, electrolyte concentration and composition and the adsorbent bed thickness. Multiple adsorption and regeneration cycles indicate that there is little loss of adsorptive capacity on regeneration. Whilst a number of modes of operation are potentially possible, the m4jority of the work reported in this thesis is based on separate adsorption and electrochemical regeneration. However, some work on a process involving continuous adsorption coupled with continuous and simultaneous electrochemical regeneration is presented. A third design involving continuous adsorption and regeneration within separate zones IN a single unit is given as an area for further research.

Mineral carbonation allows to permanently store CO2 into materials rich in metal oxides. However, mineralization technologies still suffer of slow reaction rates and low carbonation efficiencies and, to improve them, there has been increasing interest in employing waste streams as feedstocks. In light of this, the aim of this thesis was to determine the potential use of wastes for permanent sequestration of CO2. It was found that waste streams available for mineral carbonation in the UK have a capture potential of 1Mt/year, and in many cases, waste resources are located close to the CO2 emitters. A novel closed-loop, multi-step mineralization process was developed. The process consists of extracting calcium from the feedstock followed by its precipitation as crystals of calcium sulphate, which are then converted into calcium carbonate. Carbonation efficiency of the process increased when temperature was raised and solid to liquid ratio and particle size reduced. A 74%, 67% and 59% of carbonation efficiency was achieved for steel slag, ground granulated blast furnace slag and phosphorus slag, respectively. Finally, a real case scenario, where the mineralization process would be retrofitted to a steel plant, was investigated. It was found that, because of the thermal and electrical energy required to run the process, the mineralization system would be carbon negative (i.e. storing more CO2 than the amount emitted during the process) when the solid to liquid ratio would be 240g/l or higher.

No description available.

Uncertainty and variability are prevalent in any engineering design. In this study, the uncertainty of input parameters for the stability of a landfill veneer cover soil and the integrity of a lining system were treated probabilistically using Monte Carlo simulation. Statistical information required to postulate the distribution types of input parameters, taken as random variables, were identified and characterised using available data from literature survey and a designed laboratory repeatability testing programme. The variability and uncertainty of interface shear strengths (τ) and the derived strength parameters for three generic interfaces, commonly found in a landfill lining system, were computed and compared using these types of information. The variability of τ computed using the combined global database were three-to-five times and could reach up to seven times higher for the derived strength parameters when compared to laboratory repeatability test results. Additionally, a normal distribution was recommended for interface shear strengths and derived parameters (except interface adhesion with high COV) for good quality data based on subjective and objective statistical test methods.

Sustainable and effective treatment of landfill leachate has become one of the most important environmental problems due to the fluctuating composition and quantity, as well as its high concentrations of pollutants. High-tech solutions applied for the leachate treatment are expensive and energy consuming, and in addition they are not suitable at many landfill sites, especially those in rural areas. Hence there is need to develop novel and sustainable low-energy systems for the effective treatment of landfill leachates. Constructed wetlands (CWs) are inexpensive simple to operate and they have the potential to remove not only organic carbon and nitrogen compounds, but heavy metals. This study focussed on the design, development and experimental investigation of a novel CWs for the treatment of landfill leachate. The CWs employed dewatered ferric waterworks sludge (DFWS) as the main substrate. The overall aim of the study was to design and assess the novel configuration of the CWs, whilst also contributing to advancing the understanding of pollutant removal from the landfill leachate in the CWs, through the development of models to explain the internal processes and predict performance. The key design and operational variables investigated were: the primary media used, i.e. the DFWS, and the wetting and drying regimes. The CWs was configured as 4-stages in series which was operated for 220 days. Thereafter, an additional unit was added due to clogging and the CWs was operated for 185 days in this second period. Results and experimental observations indicate that the chemical treatment processes (adsorption and precipitation) contributed to the clogging. The DFWS used served as adsorbent for heavy metals removal in the system. Results of heavy metals, organic matter (COD), ammonia and total nitrogen removal indicate average removals of 99%, 62%, 83% and 81%, respectively in first period; and 100%, 86%, 90% and 82% in second period, with an average heavy metals loading rate 0.76 g m-2 day-1, organic loading rate 1070 g m-2 day-1, ammonia loading rate of 178 g m-2 day-1 and total nitrogen loading rate 192 g m-2 day-1. Results were supported through mathematical analysis using STELLA model for heavy metals transformation in CWs and numerical modelling using HYDRUS CW2D, which enhanced understanding of the internal processes for organic matter and nitrogen 4 removal. The result from STELLA modelling showed that up to 90% of the removal of heavy metals was through adsorption, which is highly significant. While HYDRUS CW2D results showed that the main path of nitrogen removal was through simultaneous nitrification and denitrification. Overall, results have shown that CWs design has great potential for reduction of metals and nutrients in landfill leachate. Results of this study can contribute to future CW research and design for landfill leachate treatment, through the increased understanding of long-term pollutant removal in these systems. In time, this may result in the wider application of CWs for landfill leachate treatment to better protect the environment.