The toxic effects of cadmium on aspects of the survival, behaviour and reproduction of Gammarus pulex and Asellus aquaticus are described in some detail. Some of the laboratory procedures were validated in field experiments. The presence of the parasites Pomphorhynchus laevis and Echinorhynchu_s1truttae does not modify the toxicity of cadmium (0.01-1.0 mgl ) to their intermediate-Fost G. pu7ex. Pretreatment for 24 hours with 0-47 μgl cadmium alters the distribution of separation times when precopula pairs of G. pu7ex are disrupted by the invertebrate anaesthetic 2- phenoxyethanol. Precop1la is directly disrupted by exposure to cadmium (0.1-12.7 mgl )_ýut recovery can follow. Pretreatment with cadmium (3-140 μgl ) for 24 hours, of similarly sizeci male G. pulex and subsequent exposure to 0.13 and 2.23 μgl while in competition for access to a female may increase tolerance and enhance reproductive success, or initiate irreversible toxic effects and impair competitive ability. Exposure of female G. pulex-1to 2.0 and 9.6 μg1 , and female A. aquaticus to 40.2 pgl cadmium pre-fertilization reduces their fecundity. Brood development times of G. pulex and A. aquaticus exposed to 2.1 and 12.4 μg1-1 cadmium postfertilization are extended by 2 and 2.7 days respectively. The embryonic development and abortion during brooding are described in detail for A. aquaticus. An explanation of reduced final brood size in Asel7us is Postulated. Growth of juveniles of both test species exposed during brooding is assessed. Single and repeated 24 hour field simulations of acidic deposition demonstrate increased host sensitivity of G. pulex infected with P. 7aevis. The effects of low pH and elevated aluminium concentrations are mitigated to some extent by liming. Six hour field simulations of the individual components of farm waste demonstrated that infected gammarids were more susceptible under conditions of low dissolved oxygen than uninfected conspecifics.

Biological Aerated Filters (BAFs) are wastewater treatment systems which contain support media for biofilm development and provide oxygen at the base of the reactor to sustain aerobic microbial treatment processes. The aims of this study were to characterise and quantify the treatment capability of non-backwash BAFs used in small sewage treatment works, and therefore establish design recommendations. Three full scale trial BAFs, a field operational small sewage treatment plant, and a full scale aeration testing facility were studied. The trial BAFs, with simulated secondary settlement, provided carbonaceous stabilisation under various hydraulic loadings and airflow rates. Nitrification showed no relationship with airflow rate, but was inhibited at high hydraulic loadings. Sludge production in the BAFs was less at higher airflow rates, due to improved stabilisation of organic solids. Media specific surface area had little effect on treatment performance. Downflow operation generally provided better treatment than upflow operation, with high levels of suspended solids stabilisation, considered a function of longer residence times. The mean BAF residence times determined empirically were considerably shorter than the design residence times, and may have inhibited treatment potential. The oxygen transfer efficiency (OTE) of coarse bubble diffusers was enhanced in a simulated BAF, due to the effects of the support media. Fine bubble diffuser OTE was inhibited by the media. Coarse diffusers may be more appropriate than fine diffusers for small non-backwash BAFs, a function of performance and cost efficiency. A small packaged sewage treatment plant incorporating BAFs produced a well nitrified effluent with reasonable organic stabilisation, and showed little diurnal or seasonal variation in effluent quality. The plant compared well to other small sewage treatment systems, providing treatment in a small footprint. Design recommendations for non-backwash BAFs and small sewage treatment plants incorporating BAFs have been established, based on the knowledge gained during this study. It has been demonstrated that non-backwash BAFs are appropriate for use in small sewage treatment works.

The purpose of this study was to investigate the role of soil erosion as a factor in lake pollution and in particular the transport of phosphorus from field soils to streams and lakes in association with mobile sediment. Four land uses were selected as representative of the Slapton Ley catchment area to investigate the levels of phosphorus in the soil. The surface soil samples from the selected land use areas were analysed to determine the water-soluble phosphorus level in solution and exchangeable phosphorus level in sediment. Twelve experimental plots were studied in order to assess the erosional effects of overland flow and thus to determine the level of phosphorus from different land uses which may be influencing the eutrophication of the lake. It was concluded that slope angle, vegetation cover, surficial soil properties, animal influence and agricultural practice are the main factors influencing sediment transportation by overland flow. Estimated results for the agricultural fields indicated that the actual phosphorus loss to the Ley is always greater in sediment than solution and actual phosphorus loss in sediment is greater in arable (root) and cereal than in grass. The point water samples (136) from 13 different sources were grouped. Mean value of phosphorus concentration from the point sources indicated that the agricultural land uses such as arable and cereal provide 2 times more exchangeable phosphorus attached to sediment than the other land uses whereas farm and sewage provided 5 times more soluble phosphorus in water than other sources. Phosphorus concentration during peak discharge was examined for the Cara catchment. The results indicated that the ratio of phosphorus concentration in suspended sediment to phosphorus concentration in water is 240: 0.3 and that there is a linear relationship between phosphorus in water and phosphorus in sediment during the peak discharge. Sediment phosphorus levels in the marsh area were also examined. The results indicated that the top layers of the marsh sediment particularly at the surface, have higher phosphorus concentration than the lower layers and that there are higher levels in sediment than in water. From these results the conclusion was drawn that the soluble phosphorus in water is at highest concentration in sewage works effluent. However this effluent contributes a small proportion of phosphorus load to the Ley compared with the arable (root), cereal and grass lands in the catchment. Agricultural sources, particularly arable sources such as root and cereal play an important role on soil erosion as a factor in lake pollution and in particular in the transport of phosphorus from field soils to streams and lakes in association with mobile sediment in the Slapton Ley catchment.

Contamination of freshwaters is of concern because of its effect on ecosystem health. The effect of contamination can be assessed at all levels of biological organisation, from the ecosystem level to the molecular level. At the biochemical level, enzymes that are involved in the detoxification of organic chemical contaminants are useful as markers of contaminant exposure as they are often one of the first systems to respond to chemical exposure. Furthermore, changes in the activity of these enzymes may be indicative of effects at higher levels of biological organisation. In this study, the use of the detoxification enzyme glutathione stransferase (E. C. 2.5.1.18) (GST) in the freshwater invertebrate Gammarus pulex (Crustacea: Amphipoda), as a biomarker of organic xenobiotic exposure and effects was assessed. Toxicant induced changes in GST activity were related to changes in energy status and physiological energetics. A GST assay was developed that allowed the rapid analysis of GST activity in up to ninety individual animal samples simultaneously. Optimum sample handling and assay conditions were determined for the assay of GST in G. pulex, and extrinsic factors (e. g. environmental temperature, feeding and holding conditions) and intrinsic factors (e. g. body size), affecting variability of GST activity in G. pulex were assessed The effect of exposure to the organic xenobiotics lindane( an organochlorinein insecticide) and alcohol ethoxylate( a non-ionic surfactand detergent)on GST activity in G.pulex was described. The magnitude and duration of the response of GST activity to exposure to both chemicals was assessed under laboratory conditions and with alcohol ethoxylateu, sing outdoor artificial streams. The use of GST as a marker of pesticide exposure in field populations of G. pulex that were subject to pesticide contamination was studied in comparison with animals from non-contaminated, reference sites. The differences in GST activity between animals from a contaminated site and clean site were investigated by short-term and long-term exposure to lindane in the laboratory. Changes in energy status and physiological energetics were investigated in G. pulex on exposure to lindane by measuring glycogen concentration and scope for growth. Measuring these parameters on short-term and long-term exposure to lindane allowed the sensitivity of these responses to be related to the GST response and allowed the energetic cost of exposure to be assessed. It was concluded that increase in GST activity may providea rapid and sensitive biomarker of xenobiotic exposure in the short-term and in populations subject to pesticide contamination. The affect on GST activity may be indicative of effects at higher levels of biological organisations, such as scope for growth and glycogen concentration However, GST activity is affected by a variety of intrinsic and extrinsic factors and should therefore be used only asp art of a comparative study. Because of the transient nature of the GST response in situ assessments should be based on 24-hour exposure periods.

The concentrations of trace metals: cadmium, copper, nickel, lead and mercury, in addition to aluminium, iron and manganese were determined in the sediments and pore water (except aluminium) of the Forth estuary. Organic matter (as loss on ignition), total organic carbon (TOe), total organic nitrogen (TON), particle size and redox potential were also determined in the sediments. In addition, chloride, sulphate, conductivity, alkalinity, pH, dissolved organic carbon, phosphate and nitrate were determined in the sediments pore water. Trace metals in the pore water were determined using a modified preconcentration technique and measurements were carried out by graphite furnace. Mercury was measured using the p.s.a mercury specific fluorescence detector. organic matter (TOC & TON) in the sediments were measured using CHNS/O analyzer. Samples were collected at seasonal intervals for a period of 18 months on board the survey vessel "Forth Ranger". Six stations were selected to represent upper, middle and lower estuary. Sediment cores collected at each station were subjected to centrifugation under nitrogen gas atmosphere to separate the pore water after being sectioned at 2.5 cm intervals for a depth of 10 centimetres. Concentrations of trace metals in the Forth estuary varied from station to station and from one season to another. Mean concentrations for sediments were as follows (mg\kg): lead, 56.9; cadmium, 0.22; copper, 38.9; nickel, 33.7 and mercury, 1.86. For pore water, the mean concentraxxi tions (Jlg\l) were as follows: lead, 3.14; cadmium, 1.86; copper, 31.9; nickel, 24.7 and mercury, 0.075. Measurements of sulphates, nitrates, phosphate, conductivity and dissolved organic carbon were used to examine the processes controlling their distributions in the pore water. The results indicated that the distributions of nutrients (phosphate and nitrate) in the upper 10 cm seemed to be controlled by macro-infaunal irrigation activities and their values varied according to the overlying water conditions. The distributions of trace metals in the sediments were found to be controlled by particle size and organic matter both spatially and temporally. Vertical distribution of trace metals in the pore water were found to be controlled by redox potential variations especially for iron and manganese. Concentrations of trace metals (Pb, Hg, Ni, Cd and CU) in the pore water were found to be higher than that in the overlying water. Enrichment factors were limited to 10-50 fold increase. Lead and mercury were 10 fold higher while 50 fold higher were found for nickel, copper and cadmium. Benthic flux calculations showed a significant flux of trace metals both in the summer and winter. However, flux of copper, nickel and lead tended to increase in the summer. Spatially, the lower estuary showed a higher flux of trace metals than the upper and middle reaches of the estuary.

In the design of urban drainage systems, synthetic design storms are commonly used to predict the peak flow rate in sewer systems and such storms are usually based on local intensity-duration frequency curves or design storm profiles. To estimate the quality of storm flow, the UPM Manual (1994) has highlighted the development of detailed and sophisticated simulation models to estimate the pollutographs, that is, the temporal variation in the concentration of pollutants in urban drainage systems. The data requirements of these models are quite onerous, and as a consequences implified models like SIMPOL have been developed. This model predicts the BOD at 1 hour time intervals and is based on the representation of the sewer system by a series of tanks. This approach may be considered satisfactory for the prediction of accumulative pollution over an annual series of events but for the prediction of acute effects, for example, the first foul flush, the temporal variation in the concentration pollutants in sewer flow is required. There is a need therefore to describe the change in pollution over a much smaller time interval than that proposed in SIMPOL and this is particularly so when consideration is given to the comparison of the design and control options which may be proposed, for example, the real time control of storage tanks to retain the first flush of pollutants. The work outlined in this thesis presents an alternate simple methodology to estimate the pollutographs corresponding to a particular storm event. The work is based on the results of the measured pollutographs recorded on the WRc sewer quality archive (1987) from two catchments at Great Harwood and Clayton-le- Moors in the North West of England. The relationships for the shape of the pollutograph were obtained by the direct comparison of the observed pollutographs. The peak TSS concentrations were obtained by a detailed regression analysis of the observed peak TSS concentrations, the antecedent dry weather period and the hydrological parameters of maximum rainfall intensity, average rainfall intensity and storm duration. These parameters were then related to the shape of the pollutograph and the results of this methodology were shown to satisfactorily reproduce results for the catchments considered. For practical applications, the suggested procedure provides a methodology to calibrate the design pollutographs for any catchment from a limited number of monitored storm events and to utilise these together with time series storms to assist in the performancea ssessmenat nd selectiono f alternative design options. The work has the limitation that it is catchment specific but as more information for different catchments becomes available, it may be possible to establish standard pollutographs for application to a wide range of catchment conditions.

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