Phosphonates are a family of organophosphorus compounds characterized by the presence of a carbon- phosphorus bond. This bond provides greater chemical stability compared with analogous compounds containing the more reactive carbon-oxygen-phosphorus linkage (Quinn et al., 2007). Hence, it is important to consider their accumulation in the environment and possible toxic threat to ecosystems. This study explored the distribution ofphosphonate metabolic pathways among sequenced microorganisms and their prevalence and occurrence in the environmental metagenomic database using bioinformatic tools. Experiments carried out on a number of marine representative strains confirmed the capacity of their predicted phosphonate catabolic enzymes to utilize phosphonates for bacterial growth when supplied as phosphorus and to some extent, as nitrogen sources. The bacterium Roseovarius nubinhibens ISM was able to . produce methane through the aerobic degradation of methylphosphonate even in the presence of Pi concentrations up to 7.5mM. Also, this strain exhibited the unique characteristic of producing both polyhydroxybutyrate and polyphosphate concurrently as result of nutritional stress through either phosphorus or nitrogen limitation. Haloquadratum walsbyi was confirmed to be the only known archaeon to possess a phosphonate degradation pathway, and experiments confirmed the capability of this strain to consume phosphonates 2AEP, MPn and glyphosate as phosphorus sources.

Dolomite and charred dolomite have been evaluated for use in the removal of dissolved arsenic anions (arsenate and arsenite) from wastewaters. Experimental equilibrium isotherm investigations, kinetic experiments and fixed-bed column experiments have been used to assess the uptake from a wide range of aqueous arsenic solutions, employing both dolomite and thermally processed (charred) dolomite. Scanning electron microscopy, X-ray diffraction, FTIR analysis, Zetasizer (size analysis), mercury porosimetry and inductively coupled plasma atomic emission spectrometry (ICP-AES) have been utilized to aid in the evaluation of the dolomitic materials as adsorbents. Equilibrium experimental data have been analyzed using Langmuir, Freundlich, Henry and Redlich-Peterson isotherm models. Kinetic data have also been analyzed using elementary first and second reaction models and an intra particle diffusion model. The data from the models have been used to help determine the mechanism of arsenic removal. Dolomite and its thermally activated dolomites have shown potential as a cost effective material for use in the removal of arsenic from drinking water. Modifying the surface of the dolomite by charring, helped to overcome obstacles encountered with the adsorption of arsenic onto raw dolomite. The charred dolomite shows significant potential in removing As (III) from aqueous solutions and has been shown to operate effectively under a wide pH range. The thesis provides evidence for ion exchange, adsorption and precipitation mechanisms, to account for the removal of arsenic from aqueous solutions using dolomite and charred dolomite.

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The aim of this research is to investigate the effect of mecoprop (RS-MCPP) degradation in an anaerobic membrane bioreactor (AMBr) under a range of redox conditions (methanogenic, nitrate reducing and sulphate reducing). A method was developed for the analysis of (RS)-MCPP in aqueous form using High Performance Liquid Chromatography (HPLC). The study was carried out in five phases. Initially, Phase I investigated the effect of elevated (RS)-MCPP on AMBr under methanogenic conditions. In this phase, increasing concentrations of (RS)-MCPP (5 - 200 mg. L-1) promoted a progressive increases in the (RS)-MCPP substrate utilisation rate (SUR) (0.15 to 3.19 [ig-mgVSS' 1. d"'). However, the COD removal efficiency decreased gradually from 98 % to 94 % as the (RS)-MCPP concentration increased in the feed from 50 - 200 mg. L-1, respectively. Phase II investigated the effect of denitrifying conditions on (RS)-MCPP degradation. Results showed that (RS)-MCPP removal efficiency and (RS)-MCPP SUR improved from 2- 47 % and 0.5 to 60.7 Rg. mgVSS-l. d-1, respectively as the COD/N-NO3-1 ratio and OLR were reduced from 250 to 0.2 and 1.51 to 0.07 kgCOD M, 3 A-1, respectively. Phase III investigated the effect of sulphate-reducing conditions on (RS)-MCPP degradation. Results showed that sulphidogenic conditions were less effective than nitrate reducing conditions with an average (RS)-MCPP removal and (RS)-MCPP SUR at 20(±10.7) % and 16.4 ýtgm. gVSS-lffl, respectively. Phase IV investigated the effect of HRT on the kinetics of (RS)-MCPP degradation. The robustness and stability of AMBr was also investigated in response to hydraulic shock loads on the biomass imposed. Results showed that the AMBr is stable to a large transient hydraulic shock loads, and it recovered rapidly to baseline performance after the hydraulic shock load had ended. High (RS)-MCPP degradation (up to 75 %) and utilisation rates (43 gg. mgVSS'1. d") were observed at long HRT (16.9 days). Phase V was a confirmatory experiment study to investigate the possible effects of trace quantities of oxygen that had been present in the reactor headspace and the effluent tank during Phase IV. This confirmed that the system performance towards (RS)-MCPP biodegradation had not been affected by trace oxygen levels when comparison are made. The molecular-based method, fluorescent in situ hybridisation (FISH) was used for the direct identification and enumeration of microbial communities in the AMBr sludge. In general, FISH results showed populations were dominated by methanogenic archaea in methanogenic phase (Phase I and IV) comprising between 55-66 % of the DAPI count. However, as anoxic condition were introduced in Phase II and III (nitrate reducing and sulphate reducing), the results identified a definite population shift, with the predominance of eubacteria (70-86 % of the DAPI count). The two methanogenic genera detected were Methanosaeta and Methanosamina. Of these two genera, the former was dominant in the reactor accounting for 57-100 % of the total methanogenic archaea. Furthermore, a comparison of (RS)-MCPP utilisation rates in each phase of the research revealed wide ranges (RS)-MCPP degradation efficiency and (RS)-MCPP SUR, however, although changes were observed in the composition of the bacterial population, no direct linkage could be made with any of the individual groups identified by FISH.

Urban wastewater characteristics are altered during transportation through sewers as a result of biochemical processes. Quantification of these changes is relevant to predict inflow loads to wastewater treatment plants, to calculate pollutant emissions from urban drainage systems (CSOs) and to ascertain any in-sewer treatment effect. Improved knowledge of in-sewer processes potentially leads to changes in the design, analysis and management of urban wastewater systems. The aim of this thesis is to contribute to the understanding, description and assessment of mechanisms involved in the transport of pollutants in sewers, by combining experimental investigations with model development. The focus is restricted to dry weather flow processes occurring either in foul or in combined sewers, under aerobic conditions and free surface flows. The basic approach of the resulting model sought to provide a detailed description of the transport processes, together with the transformation processes modelled by a method similar to that of the lAWQ Activated sludge models nr.1 and nr.2. The intention was to separate the effect of advection-dispersion on the concentration of key pollutants from those due to biochemical transformation processes. The model thus contains modules for hydrodynamics, advection-dispersion and water quality. Processes such as reaeration, heterotrophic growth (suspended and attached), heterotrophic decay, hydrolysis and ammonification are included. COD fractionation describes the oxygen demanding components, and ammonia is included because of its environmental importance and active role in the transformation processes. Data requirements for both model calibration and verification were established by means of sensitivity analysis. Extensive experimental work was carried out at a case study site to supply data for model calibration and verification and to support the selection of the relevant processes occurring in sewers. Aspects studied include: quantification of COD, BOD, ammonia, nitrate and solids removals; determination of oxygen uptake rates (respirograms) in wastewater; evaluation of diurnal variation of flow and quality determinands; determination of the Manning coefficient; measurements of reaeration at drops; and estimation of the dispersion coefficient. The respirograms were essential to calculate model parameters and COD fractions. Model fit was found to be good for the COD fractions and ammonia but poorer for dissolved oxygen. The latter was found to be the key variable and very sensitive to small variations in parameter values. The relative importance of dispersion and transformation processes on pollutant concentrations was evaluated. Further applications and developments of the model are discussed.

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