No description available.

The aim of this research was to investigate the application and effects of pressure on an aerobic biological wastewater treatment process. For the purpose of the investigation two specially designed, identical, laboratory-scale rotating biological contactor (RBC) units were constructed. One of these was held in a steel pressure vessel while the reference unit was operated open to the atmosphere. The treatment capabilities of the pressurized unit, as compared to those of the reference unit, were determined for a variety of organic loadings at increasing pressures up to a limit of 6 bar. During the investigation, the substrate employed was a synthetic wastewater made up frequently in the laboratory. Most of the analytical work was carried out on composite druly samples of the feed wastewater and of the two effluents produced, both filtered and nonfiltered. In addition, sludge samples from both units were regularly tested for a variety of sludge parameters. The water quality parameters investigated were the 5-day Biochemical Oxygen Demand (BOD5), the Chemical Oxygen Demand (COD), Suspended Solids, pH, Temperature, Ammoniacal Nitrogen and Total Oxidized Nitrogen (TON). The yield of sludge produced and certain characteristics of sludge i.e. Specific Stirred Volume Index (SSVl). Specific Resistance to Filtration, were also obtained. The quantity of air required for the pressurized treatment unit was also investigated. The pressurized treatment unit has demonstrated the capability of operating with a high level of carbonaceous oxidation and nitrification at organic loadings of up to 13 g BOD5/ m2 of disc area per day. In comparison with the identical reference unit operated at atmospheric pressure, the pressurized unit demonstrated slightly improved BODs and COD removal efficiencies, a greatly improved level of nitrification and a substantially lower sludge production. All these characteristics improved with increasing pressure.Of particular importance the sludge yield coefficient was always significantly lower for the pressurized unit than for the reference unit and results such as 0.12 kg dry solids/ kg BOD5 removed at 6 bar pressure are highly signif1cant with regard to the requirements of the modern wastewater treatment industry. Additional investigations were carried out to determine the cost of a proposed full-scale pressurized treatment unit with a design based upon the findings of this investigation. These were compared with the costs of a conventional biological treatment process capable of treating an equivalent wastewater loading. The comparison between the pressurized unit and the selected processes were made for three populations (500, 1,000 and 3,000 persons). The sludge disposal costs of the pressurized unit were appreciably lower than those for the other processes. The results indicated that the cost of the pressurized unit (present value for a twenty-year period) and the costs of activated sludge and conventional RBC processes were found to be similar for the smaller populations. However a substantial saving could be obtained with the pressurized unit for the larger populations. In addition there is an indication that the land requirement of the pressurized treatment unit decreases appreciably as the flow rate increases.

No description available.

No description available.

No description available.

No description available.

Dissertation submitted in partial compliance with the requirements for the Master's Degree in Technology: Environmental Health, Technikon Natal, 2001. / The debate surrounding mercury pollution of the river system below Thor Chemicals in Kwa Zulu Natal, South Africa has been of concern to the people of the region for several years. No scientific assessment of Mercury pollution has been carried out to date, other then a study conducted by Johnston et al. (1991) in 1990 in an area restricted to within 5 kilometres of the plant. Due to elevated levels being detected directly below the plant, Johnston et al. (1991) have expressed concern that this could result in the mobilisation of Mercury into the ecosystem and possibly threaten the Ecology of the Inanda Dam which is located approximately 20 kilometres south of Thor Chemicals which is a major reservoir for Durban. Added to this, the community residing in the area has expressed a great deal of concern and the matter was taken up in parliament in 1998. These factors provide impetus for a follow up study to determine the extent of mercury transformation into the higher trophic levels in the area surrounding Thor Chemicals. In order to quantify the extent to which mercury has become mobilised in the ecosystem and to identify possible pathways of exposure to the community, samples of sediment, algae, cattle hair and fish were taken at ten sample sites. These sample sites were selected at intervals along the Mngceweni and Umgeni River. The first sampling site was situated below Thor and the final sample site was located at the head of the Inanda Dam. Sediment, algae, cattle hair and fish were specifically chosen as they are considered to be reliable indicators of mercury pollution and mobilization. Fish,form an important part of the diet of the community residing in the study area. Mercury concentrations for the above parameters, were compared to mercury concentrations found in the control area, upstream from Thor, as well as to international and local standards. Composite sediment samples taken at the first sample site, within 500 metres of Thor Chemicals, revealed a mercury level of 54j.lg/gram. Mercury concentrations detected in the remainder of the composite sediment samples were significantly lower and revealed similar levels of magnitude throughout the rest of the study area. The higher concentration of mercury in the sediment at the site directly below Thor Chemicals may be attributed to a high / M

A field study was carried out at Ardross forest, northern Scotland where heavy metal contaminated sewage sludge had been applied to a peaty podzol at rates of 500 (low) and 1000 (high) kg N ha-1 before tree (Sitka spruce) planting. Nitrogen mineralisation rates determined by field incubation of sealed cores ranged from 3.7 to 4.5 and 7.3 to 9.4 kg N h-1 over the growing season (May to September, 1991) in soils amended with low and high rates of sludge respectively. For the control soil, to which no sludge had been added, mineralisation rates ranged from 2.4 to 2.9 kg N ha-1. Mineralisation of residual sludge was estimated to be 0.56&'37 and 1.14&'37 in 1991, 8 years after sludge application at the low and high rates, respectively. Soils brought back to the laboratory and repacked according to the field profile enabled microcosm studies to be carried out to further investigate possible changes caused to N-cycling processes in coniferous forest soil due to application of heavy metal contaminated sewage sludge, and to consider possible mechanisms of any such changes. In the microcosm study, the two rates of application of sewage sludge increased N mineralisation. A linear relationship was apparent between N mineralisation and the rate of sludge application. Increased N mineralisation was associated with an increase in active fungal mycelium, biomass N and soil animal population densities. The availability of Cd, Cu, Mn, Pb and Zn was found to be related to the time of the year, with highest availability in Spring and Summer, and lowest availability in Winter. There was no evidence of any adverse effects in terms of heavy metals on the studied biological parameters and mineralisation rates in the field and microcosm studies. Total N, pH and moisture also increased due to sludge application.

The work in this thesis relates to understanding the potential effects of using surface liming of upland soils to ameliorate water acidification. Effects on vegetation, soil, and drainage water chemistry are considered. Part I of this thesis reviews the environmental conditions of British Uplands (climate, soils and vegetation), and the relevant literature on water acidification in North-East Scotland. In Part II, each chapter deals with materials, methods used, discussion of the results and conclusion for one of a series of individual experiments. This pattern is followed for a number of laboratory, greenhouse and field studies. Liming of different organic soils significantly increased only the surface layer pH of the soils. The consequence of surface liming should be highly beneficial in terms of water quality, since most of the precipitation in the catchment under consideration (Glendye) during heavy storms, when river acid episodes occur, drains near or over the surface. The effect of lime on pH below the surface should be considered after a year or more. Liming on the other hand increased the mineralisation of organic N and released NH4+ and NO3-. The balance between N mineralization and immobilization by vegetation and microbial biomass should be considered carefully for each individual soil and site. If the mobile NO3- reaches the river or streams and increases the NO3- to beyond an acceptable limit, this could be considered an adverse effect of liming. Although within the timescale of this project there was no adverse effect noticed on the heather under field conditions, the long term effects should be considered carefully in terms of changing vegetation pattern as a result of liming, which will favour growth of grass.

Section 1 deals with the effects of four low toxicity oiled drill cuttings samples and one diesel oiled cuttings sample on marine sediments. The sediments were contained in 18 onshore tank systems and, after equilibration for 3 months, cuttings were added at levels comparable to those found at about 500m from North Sea oil installations. Tanks containing uncontaminated sediments acted as controls. All contaminated tanks showed identical changes in redox profiles, becoming most reduced after 3 months and gradually recovering thereafter. The highest sulphide levels were recorded in tanks with the highest total oil and n-alkane levels and these reached a peak after 3 months before declining. Levels were still elevated after 15 months in all tanks. Total oil concentrations declined in all tanks over the period of the experiment, n-alkanes and naphthalenes being degraded first. A substantial decline in nematode abundance was observed in all treated tanks in the first month following cuttings application, after which the decline in diesel and the highest oil loaded low tox tanks continued more gradually. Nematode numbers in low tox tanks with lower oil loadings showed fluctuations with abundances greater than that of controls at some points. Interstitial copepods were eliminated in all tanks within the first three months and controls showed general declines over the experimental period. End/opibenthic copepods showed a more varied response with low tox treatments exhibiting enhanced populations, those with lowest oil levels showing the greatest abundances. Abundances in control and diesel treated tanks remained low and constant throughout the experiment. In the first few days after cuttings treatment the greatest evacuation rates for the burrowing bivalve Tellina were recorded from diesel treated sediments followed by the low tox treatments in order of oil loading. It is concluded that the long and short-term impact of diesel cuttings is greater than that of low tox cuttings containing equal oil concentrations. Section 2 deals with the effects of chemical inducing agents, drilling fluid base-oils, oiled drill cutting contaminated sediments and time of year on the hepatic cytochrome P-450 dependant monooxygenase system of the marine flatfish plaice (Pleuronectes platessa). Intraperitoneal injection of 3-methylcholanthrene, Aroclor 1254 and isosafrole greatly enhance several hepatic monooxygenase activities, with each inducing agent producing a slightly different profile of activity both in the presence and absence of a naphthoflavone in vitro. Intraperitoneal injection of oils from diesel and a low tox drilling fluid also induced several monooxygenase activities, and these oils also differed slightly in their induction profiles. These results suggest that more than one isozyme is responsive to chemical induction in the livers of these fish. Induction of monooxygenase was also demonstrated in fish exposed to cuttings contaminated sediments. Plaice exhibit a seasonal cycle for the basal levels of monooxygenase activity. These results are compared with similar work on rats and other fish species and the implications for environmental monitoring, carcinogenicity and reproduction are discussed.