Study of natural and artificial systems for reducing polluted loads for the sustainability of the hydric resources of the Baixo Ribeira de Iguape - SP

Abstract

Natural water systems typically consist of numerous mineral assemblages and often include a gas phase in addition to the aqueous phase; they almost always involve a portion of the biosphere. Aquatic ecosystems perform numerous valuable environmental functions. They recycle nutrients, purify water, attenuate floods, augment and maintain stream flow, recharged ground water, and provide habitat for wildlife and recreation for people. Nevertheless, rapid population increases have led to the pollution of surface waters by industrial and municipal sewage wastewaters, fertilizes, insecticides, motor oil, toxic landfillleachates among others. At the same time that water pollution and releases of nutrient-Iaden municipal sewage effluents have increased, water consumption has also increased, thus reducing the flows available for the dilution of wastes. Increased sediment delivery resulting from urban areas, agriculture and forestry also has resulted in greater turbidity and sedimentation in downstream channels, lakes, and reservoirs, with attendant losses of water storage and conveyance capacity, recreational and aesthetic values, and quantity and quality of habitat for fish and wildlife. This has led to aquatic organisms becoming extinct or imperiled in increasing numbers and to the impairment of many beneficial water uses, including drinking, swimming, and fishing. Moreover, the impacts pointed out are all connected and depended on the strength and the resilience of the natural water systems hit by them. Therefore, since the loss and impairment of aquatic ecosystems is accompanied by loss and impairment of environmental functions and amenities important to humans, and since preservation and restoration of aquatic ecosystem are possible, the previous treatment of the residuals discharged to the environment should be imperative. Biological waste treatment is one of most common solution adopted by sanitary engineering to reduce the pollution. The biological processes are conducted by technological systems throughout microorganism activities under aerobic (Stabilization Ponds, Activated Sludge, and Biological Filters) and anaerobic conditions (Biodigestor and landfills), as well as in nature conditions, inside rivers or wetlands. Stabilization ponds, as its denomination, can be seen as a bioreactor in order to develop a food chain among microalgae and bacteria, both involved with organic matter degradation under aerobic conditions. It is highly recommended to underdeveloped regions with tropical climate and enormous areas to reduce organic matter of municipal sewage wastewater. There are some advantages related to this biological process, and it could be highlighted the natural oxygen supply to the bacteria growth by the microalgae. In addition, stabilization ponds under anaerobic conditions are also applied to municipal wastewater treatment, and in this case the microbial activities are very similar to that found in biodigestors. However, some problems can be related to the operation of any kind of stabilization ponds, as the quality of its effluents discharged to the natural water system after the treatment. The focus of the present research is addressing to improvement the management of the stabilization ponds and natural effluents discharged in the aquatic systems. The area choose to be studied is located in the South of São Paulo State, including the Baixo Ribeira do Iguape region, particularly the Jacupiranga and Pariquera-açu Rivers watersheds. Those rivers received a sort of effluents from the stabilization ponds treatment plant and from the natural auto depuration systems such as wetlands. The research strategies are presented in three stages: (a) evaluation and prediction of the watersheds and on the quality of the biological treatment processes to reduce organic matter - e.g. geographic localization, hydrologic and climate characterization, and trophic state from nutrient loading; in addition, the microbial communities involved in the biological treatment systems will be ChgractQri2Qd by ClgggiCgl gnd moIQculgr techniques; (b) deterMination of primarY productivity and organic matter decomposition in the biological treatment systems as well as in the experiments carried on in the bench scale; (c) support baseline studies of the systems functioning to provide comparisons of different biological processes types among the regions considered, and to built an index for the local environmental sustainability. An interdisciplinary approach must be required to sustain the holistic view need to understand the real condition of the watersheds and to propose particular solutions to the problems found in the Baixo Ribeira do Iguape region. Scientific contribution is expected to be in national and international publications and congress and seminars participation as well. (AU)