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A slow sand filter system was developed which was suitable both for experimental purposes and full scale community water supply. The performance of the system was enhanced by the incorporation of pretreatments such as gravel prefiltration, sub-sand prefiltration and direct protection of filters by the incorporation of synthetic fabric layers. The system was used to examine aspects of the biological and physico-chemical nature of Slow Sand Filtration with particular reference to the removal of Rotavirus and a variety of bacterial and viral indicators. The results of the developmental phase and experiments conducted with operational filters and in the laboratory confirmed the importance of biological mechanisms, in particular adsorption to biological surfaces present in the upper horizons of slow sand filters. It was observed that both the efficiency and pattern of removal of Rotavirus in Slow Sand Filtration were similar to those observed for faecal indicator bacteria, bacteriophage and turbidity ie colloidal clay and other particles. Thus it was concluded that negatively charged particulate colloidal entities appear to behave similarly despite differences in size and surface characteristics and that Rotavirus is no more or less likely to pass through slow sand filters than any other particle. Thus, a well operated slow sand filter may be expected to achieve a reduction in Rotavirus densities of 2 log10 orders of magnitude. The principal mechanisms of removal of Rotavirus in the upper horizons would appear to be transportation by diffusion and adsorption to biofilms and biomass. Microbial predation is not likely to play a dominant role in the removal of Rotavirus from the aqueous phase but may be important in inactivation. A detailed examination of the incidence, prevalence and seasonal occurrence of rotaviral and other diarrhoeas in less developed countries led to the observation that unlike some of the bacterial pathogens, transmission of Rotavirus does not have a strong association with water quality. Hence. The case for low level waterborne transmission and thereby maintenance of endemicity in the community remains entirely theoretical. Moreover, bearing in mind the likelihood that slow sand filters will be operated sub-optimally in many cases, a moderate reduction in Rotavirus densities eg 1 - 2 log10 units may not be significant in terms of diarrhoeal disease risk, particularly for children and especially in the rural sector. In view of these observations and other factors eg the low infective dose of the virus and the undoubted pre-eminence of person-to-person spread, it was concluded that as a single process, Slow Sand Filtration is probably not capable of significantly reducing the incidence of rotaviral diarrhoea in less developed countries.

Toxicity of dissolved copper was examined in a common coastal mysid population {Praunusflexuosus). The life cycle and ecophysiology were studied under natural conditions throughout the year, and responses to dissolved copper were determined in the laboratory. Pronounced and ontogenic seasonal differences in copper toxicity for the mysid Praunus flexuosus were observed. Sublethal and lethal parameters (mortality, behaviour, metabolism, reproduction, and bioaccumulation) showed seasonal variation in response to copper toxicity, being highest toxicity in summer. Changes in the form of dissolved copper were measured during toxicity testing, using the chelating resin method to provide a measurement oftotal and labile (Chelex-available) dissolved copper in the natural seawater used in the toxicity tests. Labile dissolved copper did not show significant variations in the test seawater, confirming that organisms were exposed to constant labile copper concentrations during the toxicity test. The total dissolved copper concentration was significantly higher than the labile form, as organic complexation occurred in natural seawater and during toxicity tests. The labile fraction could be less than 50% ofthe total fraction. The total dissolved copper concentration decreased significantly when the organism was under stress. While the mortality of the population was insignificant after 10 days of copper exposure (0, 5,25, 75 and 200g 1"') in winter, lethal effects occurred at every copper exposure level after 24 hours (96h LC50 =30.8 g 1"') in summer. The effects of copper on metabolism (respiration and excretion) were very sensitive indicators of sublethal toxicity, which resulted in lethal effects with a prolonged time of exposure. Metabolism shifted to a greater reliance on protein catabolism under copper exposure in both seasons, demonstrating a stronger effect in summer. Total copper content accumulated in the organism increased with increasing copper concentration in solution. Copper accumulation rate was higher in summer . than in winter, increasing to rates of7^g g*1 dry weight day"1. Reproductive processes were severely disrupted at any copper treatment. Production ofjuveniles was reduced to zero, because of the high abortion rate, reduction on brood survival and damage to fertilisation processes.

Trace metals in natural colloidal material (l-400nm) were investigated in the River Beaulieu, the Trent- Humber system and the Celtic Sea. Colloidal and truly dissolved (<10,000molecular weight) fractions were separated by cross-flow filtration (CFF). Filtration artefacts (conventional and CFF) involving filter blockage and colloid aggregation/disaggregation transformations were minimised through appropriate protocols. 65Zn equilibration experiments were carried out with Beaulieu River colloids (<0A^m). The initial uptake of 65Zn onto colloidal material (10 to 15 %) was very rapid (seconds to minutes) but a large fraction of the tracer remained in the truly dissolved phase. Preliminary modelling to estimate the fraction of colloidal zinc under variable SPM concentrations and Kc sensitivities was completed using different partition coefficients (Kc and Kf) derived during the equilibration experiments. Initial 65Zn-colloid partitioning was related to the mass concentrations (and theoretical surface area) of colloids and colloidal aggregates. The 65Zn radiotracer/colloid association was exchangeable but overall equilibrium partitioning of colloidal/truly dissolved 65Zn did not change with increased total zinc concentration. Loose hydrophobic colloidal aggregates (filaments) with Mn hydroxide coatings formed during sample storage and were capable of removing ~60% of the 65Zn. Field flow fractionation (FFF) of colloidal Beaulieu River water highlighted the significance of the smaller colloidal fractions (<0.08^m and 0.08 to 0.134m) which contained the highest concentration of Fe, Mn and Zn when normalised to an assumed geometric surface area. A spatial and seasonal investigation of colloidal trace metals in the Trent/Humber system identified groups of metals with varying colloidal associations in the order (high to low); Fe> Pb, Mn > Cu, Zn, Ni > Cd. Colloidal Fe, Pb and Mn all illustrated removal in the low salinity region of the estuary. Ni (mainly truly dissolved) showed somewhat conservative behaviour. Total dissolved Cd (and Zn) consistently showed a mid-estuarine maximum (truly dissolved), which was attributed to chloro-complex formation or ionic exchange with major seawater ions. For most metals, the positioning and intensity of the turbidity maximum zone (TMZ) appeared to have greatest control on their removal. Cu is controlled seasonally by input of organic ligands (truly dissolved/microcolloidal). The existence of separate organic and inorganic colloidal pools was proposed, which may have seasonally variable signatures. The presence of lower molecular weight (<10,000Da) colloids is significant for Pb and Cu. Investigations of colloidal Al in the Celtic Sea highlighted problems with colloid disruption within the cross-flow system, and detection of Al colloids using a surface active fluorometric technique. Water column profiles of reactive and dissolved (<0.4/u.m) Al gave insights into processes controlling Al distribution and concentration. Resuspension of Celtic Sea sediment led to an instantaneous release of truly dissolved Al derived from authigenic mineral dissolution. FFF analysis of samples from the resuspension experiments showed that colloidal Al was not a significant fraction (<20% of total dissolved Al). On the basis of these experiments it was possible to estimate that, in the absence of scavenging, the input of truly dissolved Al from typical resuspension events could be sufficient to account for the 5-8nM increase in dissolved Al concentrations observed close to the bed. This research has contributed towards a new approach to interpretation of trace metal speciation and processes in a variety of natural waters. Assessment of the role of colloidal and truly dissolved phases within the 'dissolved' fraction has enabled better understanding of particle/water/metal interactions. The description of trace metal/colloid partitioning and associations within these multicomponent systems has the potential to enhance their modelling in the future.

The determination of surfactants in environmental surface water is required due to recent concern over possible adverse health effects that have been associated with them. This thesis is concerned with two aspects of the analysis of non-ionic and anionic surfactants in surface water. An HPLC phase-switching method has been developed in an attempt to overcome the problem of an interfering anionic species (thought to be humic acids) that masks the presence of any linear alkylbenzene sulphonate surfactants in river water samples. This problem has arisen following the development of an HPLC method for the determination of linear alkylbenzene sulphonates and alkylphenol ethoxylate surfactants in surface water in a previous research project. The phase-switching method allows the mobile phase to be diverted to either a C[1] or C[18] column or both. The linear alkylbenzene/humic acid portion was diverted to the C[18] column after elution from the C[1] column; the alkylphenol ethoxylate portion of the sample was then allowed to separate on the C[1] column as usual. Then the linear alkylbenzene / humic acid portion was separated on the C[18] column using a different mobile phase. The method works well with standards; however, with real samples it was not clear as to the identity of the peaks that may or not be linear alkylbenzene sulphonates. In addition, recent batches of the Spherisorb C[1] column were unable to adequately resolve the nonylphenol ethoxylate ethoxymers. The reason for this loss of resolution was investigated by elemental analysis and x-ray photoelectron spectroscopy. Bulk percentage carbon and surface carbon coverage both showed a similar trend. The earlier batch of Spherisorb column that produced the best resolution of nonylphenol ethoxylate ethoxymers had the lowest surface carbon coverage and the lowest percentage bulk carbon. Recent batches of the Spherisorb column along with columns from Supelco and Hypersil contained higher levels of carbon. These results suggest that resolution of the ethoxymers is due to the unreacted hydroxyl groups on the silica surface, and that the presence of the alkyl moiety actually hinders the process. In order to account for this a "pseudo reverse phase" mechanism has been invoked for this separation. The second section of this thesis involves the development of a new qualitative and quantitative method for the determination of nonylphenol ethoxylate surfactants in surface water by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. The sample was mixed with a concentrated solution of 2,5-dihydroxybenzoic acid or alpha-cyano-4-hydroxycinnamic acid as a matrix. Approximately 1 muL of the resulting solution was added to a stainless steel target and, after evaporation of the solvent, the target was placed into the mass spectrometer. The resulting spectra showed intense [M+Na][+] and [M+K][+] adducts for each ethoxymer group. Extracted samples from the River Don analysed by this method showed a similar characteristic envelope of peaks, corresponding to sodium and potassium adducts for nonylphenol ethoxylates. For quantitative determinations Triton X-100, an octylphenol ethoxylate surfactant, was added as an internal standard. A concentrated solution of lithium chloride was also added to produce much less complicated spectra consisting of solely [M+Li][+] adducts. Good linear relationships were seen for each individual ethoxymer over the entire distribution. The method showed excellent results for spiked surface water samples, but the concentrations of nonylphenol ethoxylates in recent samples were below the current limit of detection for this method of 100 mug/L.

In many biological reactors' bicarbonate ions are the major species determining pH buffering capacity, or alkalinity. In anaerobic digesters the bicarbonate levels should be within 10 to 50mM to ensure stable operation. Bicarbonate concentration in wastewater treatment processes is routinely measured off-line by titration with standard acid to a set pH value. However along with the bicarbonate/carbonate system, the phosphate, ammonia, sulphides and volatile fatty acids systems are present in anaerobic process. These systems can exert a significant influence on the accuracy of bicarbonate titration's to a set pH. An overload of 4.7 to 13.6 kgCODm-3d-1 1 administered to a 5m3 pilot scale anaerobic filter reactor showed that bicarbonate alkalinity, measured off-line by titration responded rapidly to the organic overload, decreasing by 10% after only 1 hour of the overload initiation. The propionic acid concentration (often regarded as the best indicator of instability in anaerobic digestion) increased from 170ppm to 190 ppm in the same period, which corresponds to an increase of 12%. At present the use of anaerobic digestion as a waste treatment method is partly limited because of the lack of reliable control procedures. This thesis introduces a simple on-line instrument for direct determination of bicarbonate concentration especially for automatic control of anaerobic digesters. The proposed method is based on a continuous flow rate measurement of carbon dioxide evolved from a continuous stream of sampled (&lt;15cm3min-1 ) solution after saturation with gaseous C02 and subsequent acidification with excess acid. Measurement of bicarbonate in this way eliminates the interferences of the phosphate, ammonia, sulphides and volatile fatty acids systems and removes the need for a pH probe which are subject to fouling.

Considerable controversy exists in the world with respect to coastal quality. A multidisciplinary project was initiated to examine the health effects of bathing in sewage contaminated coastal waters, using a popular beach resort, Whitmore Bay, close to the cities of South Wales; and to explore ways of measuring public perception of coastal pollution at selected beaches in South Wales including Whitmore Bay, Langland Bay and Cefn Sidan. The research also investigated the regulatory framework responsible for the sustainability of coastal tourism and the effectiveness of beach award flags as marketing tools in the promotion of resorts. Current legislation addresses coastal pollution in terms of physical health criteria with little regard given to aesthetic quality of sea/landscape and psychological well-being of the beach user. It is necessary to overcome the dichotomised approach to beach management by crossing the boundaries between the physical and social sciences in order to take an holistic view of the coastal scene, accounting for environmental, political, economic and social aspects. An epidemiological/microbiological investigation was conducted at Whitmore Bay during the summer of 1995. Statistical modelling. using Linear Logisitic Regression, indicated swimmers to significantly increase their chance of contracting an illness in comparison to non-swimmers and also identifed non-water related factors to have a confounding effect; no interaction was observed. These findings were in congruence with other major studies. Beach questionnaires were distributed to elicit information on the activities, health and socio-demographic characteristics of the subjects during the day of the survey (n=1276). A telephone interview schedule was utilised 10 days post the beach survey to investigate the differential in illness rates between the cases and controls (n=585). Water sampling was carried out on the days of the health risk survey. Although, high counts of both Ecoli and faecal streptococci were recorded, reaching an average of 3400 and 440 per 100ml respectively, no dose response relationship was observed between morbidity rates and bacterial indicator density. A semi-structured questionnaire was employed to obtain data on beach user perception to coastal pollution and beach award schemes for both the 1995 and 1996 surveys. The 1995 questionnaire served a dual approach running simultaneously with the epidemiological-microbiological analysis (n=1276). The 1996 survey questionnaire was developed from the original 1995 questionnaire. and distributed at an additional two beaches in South Wales, Langland Bay and Cefn Sidan, (n=821). Results of both surveys showed that beach users were acutely aware of coastal pollution both land based and marine and suggested that public awareness of the different beach award schemes is low. Of the different types of award systems included on the questionnaire, the European Blue Flag Award gained highest recognition (26-30%), but even those that identified with it often had a misunderstanding of its true meaning. If consumers misinterpret the meaning of the flag which flies on a designated beach. then the designation of the beach will do little to offset consumers' concerns about health risks.

The work described is primarily concerned with the understanding of the induced AC electrokinetic properties of the transmissive stages of two genera of waterborne protozoan pathogens, namely Cryptosporidium and Giardia. The assessment of viability through the use of electrorotation (ROT) has been investigated in comparison with conventional techniques. The optimum conditions for detennining C. parvum viability using ROT are described and discussed. Two Giardia and three Cryptosporidium species were investigated, as were a total of ten Cryptosporidium parvum isolates. With all species investigated a good correlation was found between the ROT response of clean particles and conventional vital dye techniques. Adherent bacteria on the particles surface have been identified as a major problem for subsequent ROT analysis. This is the first description of the effect of adherent bacteria on the dielectric response of biological particles . . A novel single layer electrode array was designed and successfully tested to overcome the problems of low particle concentration, interfering debris and particle position in the electrorotational electrodes. The device was shown to selectively concentrate particles into a central region whereupon their physiological state was then assessed through their ROT response. Modification of the device enabled the isolation of one or more particles onto a membrane, providing a suitable collection method for low particle number handling. The clearest demonstration to date of the effect of membrane integrity on the ROT response is described from spectra obtained for an oocyst before and after excystation in vitro. Storage time effects for oocysts of C. baileyi are also described as are isolate differences for C. parvum oocysts which are apparent in the low frequency region of the spectra. The implications of these results to the water industry and potential diagnostic applications of electrorotation are discussed.

This study was designed to investigate, at laboratory and pilot scale, the effects of various loading and climatic factors on the nitrification perfon-nance of four media, and to undertake a comparative assessment of the media. The media used were blast furnace slag and three random plastic media: Flocor RS, Etapak 160 and a new medium, Etapak 210. Laboratory experiments using pure cultures of Nitrosomonas europaea have determined the effect on nitrification of temperature, pH and substrate, BOD and inhibitor concentrations. Optimal values have been resolved for the temperature and pH and half- saturation constants for the substrate and inhibition are calculated for pure culture conditions. The presence of glucose and glutamic acid has been shown to have a beneficial effect on nitrification, although this observation could not be adequately explained. Pilot scale research, conducted over a two year period, has provided an accurate representation of a nitrifying trickling filter by using effluent from Cranfield STW in filters exposed to the full climadc variation. Data obtained from these filters have indicated the superior performance of the blast furnace slag media due mostly to its ability to maintain a large active bacterial Population without excessive accumulation. Results have been used to support or challenge previous publications, and to generate a set of desion curves. Conclusions from this research have been used in the design of a full scale nitrifying trickling filter which has been constructed at Cranfield STW, early data from which are presented.