This thesis examines the ecological consequences of sewage disposal in aquatic ecosystems. Sewage simultaneously represents a form of enrichment and a source of stress to a receiving system. Enrichment effects dominate when sewage loading does not exceed the capacity of the system to assimilate waste, as is presently the case in the St. Lawrence River. We developed a method to quantify the assimilation of sewage-derived organic matter by riverine biota, then used this method to examine the pathways by which sewage enhances secondary production in the St. Lawrence. We showed that the relative importance of dissolved nutrients and particulate organic matter to the river food web is to a large degree dictated by the physical and biological characteristics of the local environment. The effects of this enrichment on the receiving water community were also influenced by habitat characteristics. Analysis of body size distributions revealed that only the largest organisms had higher densities at enriched sites, and that the identity of these organisms depended on habitat structure. Densities of smaller organisms were controlled by a combination of habitat characteristics and feeding interactions. This pattern was consistent with food web models of top-down (consumer) control. At each trophic level, relatively invulnerable (large) prey achieved higher densities, whereas densities of more vulnerable (small) prey were controlled by their predators. Finally, we synthesized the ideas outlined above to predict how conditions in the St. Lawrence will change in the future as a result of lower water levels. More extensive macrophyte cover, slower current, and warmer temperatures in a shallower St. Lawrence will all enhance the ability of the system to physically retain and biologically process sewage nutrients, but will also increase the likelihood of negative effects such as anoxia.

Chlorine has a wide variety of applications in water treatment. Because of its disinfectant efficacy, it is used world wide for the treatment of potable water, sewage, swimming pools and for the control of nuisance organisms in cooling towers. A problem arises when such chlorinated water enters the natural environment, as chlorine's greatest advantage, i.e. its germicidal capacity, becomes its greatest disadvantage. In particular, the discharge of heated, chlorinated water from cooling towers and chlorinated, treated sewage into rivers have severe consequences for the riverine flora and fauna. This study focused on the effects of chlorinated, treated sewage effluent on the community structure of benthic macroinvertebrates in two rivers in KwaZulu-Natal viz. the Umsunduze River in the Pietermaritzburg area, and the Umbilo River in the Durban area. The study was conducted in three phases. The first two phases comprised a toxicological investigation of the effects of chlorine on a selected riverine macroinvertebrate, and the third phase comprised an ecotoxicological investigation of the effects of chlorinated treated sewage on benthic macroinvertebrate community structure. The first phase of the study involved the development of an artificial stream system which would be suitable for determining the response of a selected macroinvertebrate species to chlorine. Chlorine is both reactive and volatile, so this necessitated the development of a specialised flow-through system with apparatus which would allow continuous dosing of a sodium hypochlorite solution. The system was set up at the Process Evaluation Facility at Wiggins Waterworks, Durban, where raw water from lnanda Dam was used. The second phase involved the use of this artificial stream system to conduct acute 96 h toxicity tests. Baetid mayfly nymphs (Baetis harrisoni Barnard) were selected as the test organisms after a preliminary investigation found them to be suitable for survival under laboratory conditions. For comparative purposes, tests were run first on B. harrisoni from a relatively uncontaminated stream in a residential area of Westville, then on specimens from the severely impacted Umbilo River. The LC₅₀ of chlorine for organisms from both sources was found to be in the region of 0.004 mg/l (free chlorine). This value was well below the general effluent standard of 0.1 mg/l in effect at the time. The recommended acute environmental guideline is 0.001 mg/l. The third phase of the study involved field validation of the toxicity test results. It was hypothesised that since the LC₅₀ for free chlorine was 0.004 mg/l, B. harrisoni would not be found downstream from a point source of chlorinated effluent where the concentration of free chlorine ranged from 0.06 to 0.2 mg/l, and that the macroinvertebrate community structure would also be altered. In order to test these hypotheses, benthic macro invertebrate community structure was investigated at several sites up- and downstream from the outlets of the Darvill Wastewater Works in the Umsunduze River and the Umbilo Sewage Purification Works in the Umbilo River. In addition, in order to differentiate between the effects of chlorinated and unchlorinated treated sewage, a section of the Umbilo River (upstream from the chlorinated discharge) was exposed to unchlorinated, treated sewage. In this way, a limited "before and after" sewage and an "upstream and downstream" from sewage investigation could be carried out. Organisms were collected from riffles (and from pools in the Umbilo River) and the samples were then sorted and organisms were identified to species level, where possible, otherwise to genus or family. Changes in community composition were shown graphically as pie charts of relative proportions of organisms found at each site, graphs of the average number of taxa at each site; and graphs of the average number of individuals at each site; Data from the Umbilo River were also analysed using TWINSPAN (Two-way indicator species analysis). In both the Umsunduze and the Umbilo rivers, the deleterious effects of the chlorinated effluent were clearly evident. At Umsunduze Site 3 and Umbilo Site 5 (both immediately downstream from the chlorinated effluent) both the number of taxa and number of individuals were substantially reduced, sometimes to zero. Where organisms were found at the next sites downstream (Sites 4 and 6 respectively), the samples were dominated by Chironomus. In contrast, the unchlorinated effluent in the Umbilo River caused very little difference in community structure. As predicted, B. harrisoni was not found in downstream samples in which chlorine was present, yet appeared to be relatively unaffected by the unchlorinated effluent, suggesting that chlorine, rather than the effluent was responsible for its absence at downstream sites. In conclusion, it would appear that while treated sewage effluent certainly causes changes in macroinvertebrate community structure, chlorination of this effluent leads to large scale destruction of the riverine community. This in turn delays the recovery process of the river, rendering a longer stretch unfit for use. The consequences of this delayed recovery are that the failure to meet the water quality requirements of the natural environment results in those of the other water users (agriculture, industry, domestic and recreation) not being met. This reduces the natural capacity of the riverine community to process organic waste and recover from the discharge of sewage effluent. Chlorination increases the distance of impaired water quality and environmental integrity which result from organically enriched treated sewage effluent. The results of the study indicated that the draft water quality guidelines for aquatic ecosystems, derived from inadequate data, and calculated with a safety factor, were the correct order of magnitude. The approach followed in the study will be useful in the development and refinement of water quality guidelines for aquatic ecosystems.

CAPES / O acelerado crescimento da população e da industrialização, nos centros urbanos, ocasionam impactos negativos sobre os recursos hídricos, comprometendo, principalmente, a capacidade de proteção ambiental, no que tange a qualidade das bacias hidrográficas nas cidades. A bacia hidrográfica é um sistema ambiental complexo, resultante das inter-relações entre a sociedade e a natureza, e a atual situação dessas áreas são exemplos das pressões a que o meio ambiente está submetido. O uso das águas, no Estado do Paraná, é orientado pelos Planos de Bacias, enquanto que os Planos Diretores, procuram ordenar o uso do solo nos municípios. Esses dois planos se sobrepõem no trato da gestão de recursos hídricos. Dessa forma, este estudo se propõe a aplicar uma metodologia de Qualidade Ambiental Urbana – QAU, realizando adaptações, que foram aplicadas na Bacia do rio Barigui – Curitiba/PR, para analisar as inter-relações socioambientais e de infraestrutura. Os dados levantados para formar o banco de dados do QAU foram obtidos em diferentes instituições oficiais, que orientaram a adaptação dos indicadores da metodologia. A aplicação do QAU na Bacia Hidrográfica do rio Barigui, se deu por meio da divisão da bacia em cinco Unidades de Análise – UA, e na aplicação de indicadores de QAU em cada UA. Após a análise dos indicadores e agregação dos dados foi produzido o Índice de Qualidade Ambiental Urbana final – IQAU final. Todas as UA’s avaliadas apresentaram IQAU finais com qualidade satisfatória, porém os índices parciais refletem melhor a condição local. Os resultados obtidos por meio da metodologia da QAU, nesta pesquisa, foi comparada com os Planos da Bacia do Alto Iguaçu e Afluentes do Alto Ribeira e Diretor de Curitiba. O método QAU foi considerado adequado para servir de base na análise comparativa para o Plano de Bacia e o Plano Diretor. Desta forma, foi identificado que o primeiro considera a qualidade da água e a densidade demográfica, e o segundo, população, habitação, fatores econômicos, sociais, de segurança e mobilidade urbana. A comparação entre os dois Planos identificou a convergência na utilização e ocupação do solo e recursos hídricos, mas divergências no formato de agregação, o primeiro utiliza bacias e sub-bacias, e o segundo a unidade de agregação é a cidade. Os resultados da aplicação do QAU com as suas categorias de análise, variáveis e indicadores, na Bacia do rio Barigui, demonstrou o potencial desta metodologia para fazer as inter-relações necessárias visando uma orientação voltada a gestão de bacias hidrográficas urbanas. / The rapid population growth and industrialization in urban centers, has negative impacts on water resources, mainly compromising the ability of environmental protection, with respect to quality of river basins in the cities. The basin is a complex environmental system resulting from the interrelations between society and nature, and the current situation of these areas are examples of the pressures that the environment is submitted. The use of water in the state of Paraná, is guided by the Basin Plans, while the Master Plans, seeking to order the use of land in the municipalities. These two planes overlap in dealing with water resources management. Thus, this study aims to implement an methodology Urban Environmental Quality - UEQ, making adjustments that were applied in the Bacia do rio Barigui - Curitiba / PR, to analyze the social, environmental and infrastructure interrelations. The data collected to form the UEQ database were obtained in different official institutions, which guided the adaptation of the methodology indicators. The application UEQ of the Bacia do rio Barigui, was through the basin of the division into five Environmental Units - EU, and applying UEQ indicators in each environmental unit. After the analysis of indicators and data aggregation Urban Environmental Quality Index – UEQI end was produced. All EU's assessed presented final UEQI with satisfactory quality, but the partial indexes better reflect local conditions. The results obtained by the UEQ methodology in this research was compared with the plans of the Alto Iguaçu Basin and Tributaries of the Upper Ribeira and Director of Curitiba. The UEQ method was considered appropriate to base the comparative analysis to the Basin Plan and the Master Plan. Thus, it was identified that the first consider the water quality and population density, and the second, population, housing, economic, social, security and urban mobility. The comparison between the two plans identified convergence in the use and occupation of land and water resources, but differences in aggregate format, the first use basins and sub-basins, and the second aggregation unit is the city. The results of the application of UEQ with their categories of analysis, variables and indicators in the Bacia do rio Barigui, demonstrated the potential of this methodology to make the necessary interrelations seeking an orientation managing urban watersheds.

The Green Drop Certification Programme, launched in 2008 alongside the Blue Drop Certification Programme, aims to provide the Department of Water Affairs with a national overview of how municipalities and their individual wastewater treatment works (WWTW) are complying with licence conditions set by the National Water Act (NWA) (No. 36 of 1998; DWAF 1998) and the Water Services Act (No. 108 of 1997; DWAF 1998). By publishing the results of each municipality’s performance, the programme aims to ensure continuous improvement in the wastewater treatment sector through public pressure. The programme has been identified by this project as a necessary linking tool between the NWA and the Water Services Act to ensure protection and sustainable use of South Africa’s natural water resources. It does this through assisting municipalities to improve their wastewater treatment operations which in theory will lead to discharged effluent that is compliant with discharge licence conditions. These discharge licences form part of the NWA’s enforcement tool of Source Directed Controls (SDC) which help a water resource meet the ecological goals set for it as part of Resource Directed Measures (RDM). The link between meeting the required SDC and achieving the RDM goals has never been empirically tested. This project aimed to determine the present ecological condition of the Uie River, a tributary of the Sundays River which the Sundays River Valley Municipality (SRVM) discharges its domestic effluent into. It then determined whether the SRVM’s WWTW was complying with the General Standard licence conditions and what the impact of the effluent on the river was through the analysis of monthly biomonitoring, water chemistry and habitat data. Lastly, the project examined the effectiveness of the Green Drop Certification Programme in bringing about change in the SRVM’s wastewater treatment sector, which previously achieved a Green Drop score of 5.6 percent. It wanted to examine the underlying assumption that a WWTW which improves its Green Drop score will be discharging a better quality effluent that will help a water resource meets the RDM goals set for it. The Kirkwood WWTW did not have a discharge licence at the time of assessment and was thus assessed under the General Standard licence conditions. It was found that the Kirkwood WWTW was not complying with the General Standard discharge licence conditions in the Uie River. This was having a negative impact on the river health, mainly through high concentrations of Total Inorganic Nitrogen (TIN-N), orthophosphate and turbidity. The SRVM should see an improvement in its Green Drop score for the Kirkwood WWTW. However, the municipality showed no implementation of necessary programmes. Implementation of these programmes would help the SRVM meet the General Standard licence conditions (part of SDC) which would help the Uie River meet the RDM goals set for it.