Impacts of diffuse pollution on water resources

Transcription

1 12 th International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 E. Albuquerque. 1* and G. Oliveira 1** (1) Department of Hydraulic and Sanitation, College of Engineering of São Carlos of University of São Paulo (EESC/USP). Av. Trabalhador São Carlense, 400, , São Carlos SP. Corresponding authors, ; ABSTRACT In the last decades have seen a rapid growth in pollution and environmental disequilibrium. Within this framework, there is accelerated degradation of river water quality, streams and lakes for pollution loads from point and diffuse sources in the hydrographic basins. The point sources pollution are still prevalent and estimation simpler, and therefore, little attention has been given to nonpoint. A large number of studies have been developed for the study of characterization and modeling to estimate the loads of point source. Few existing studies, and even less number, the attempts of quantitative evaluation of diffuse loads. This paper presents a wide literature review focused on discussion of the impacts of diffuse pollution, particularly urban, on water resources. Were initially discussed concepts and key features of diffuse pollution, continuing with the possible pollution sources and pollutants generated and its main effects on water quality. Finally they were briefly reviewed some alternative mitigation measures by changing hydrological, and controls on emission and rainwater treatment, aiming at the quantitative and qualitative conservation of water resources. KEYWORDS: Diffuse pollution, Surface waters, groundwater, water resources, urban drainage. INTRODUCTION In last decades, the intense and uncontrolled urban growth has caused successive changes to the environment by changing the conditions of population s life and affecting the quality of available water resources. Faced with steadily increasing pressure on water resources and environmental needs of conservation of surface and groundwater, it is essential a better understanding of the risks of pollution of these resources. The urban drainage networks carry heavy loads of pollutants, constituting a major source of waterbodies degradation. This diffuse pollution is generated by runoff in urban areas, from the deposition of pollutants sparingly over the area of contributing watershed, reaching underground levels, threatening the quality of aquifers and reservoirs. The problem of point sources of water pollution is well documented and investigations about contamination form the bulk of the work of scientist hydrogeologic community. However, in urban areas there are many potential sources of diffuse pollution of groundwater and surface water, many of which are not explicitly known. Are considered nonpoint loads of pollution those in which the release from the pollution source is intermittent and dependent on the duration and rainfall intensity and the area generated. They are transported from long distances, it is not possible to determine exactly E. Albuquerque & G. Oliveira

2 12 nd International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 its origin (PORTO, 1995). Diffuse pollution, unlike point source pollution is difficult to control at source, it is related to anthropogenic changes on the environment and the natural phenomenon of the first rains. This type of pollution has a great variability in the concentration of pollutants released into waterbodies. Concentrations vary by orders of magnitude between basins, different precipitation events, and also during the same event (PORTO, 1995). To achieve the water quality of water bodies is necessary to monitor all effluents that affect the environment, they have pollution loads, including from rainwater. The lack of management and/or treatment of stormwater can make unfeasible the effort that is being made to obtain water quality. The identification of sources of generating diffuse pollution, as well as the quantification of pollutant loads influent to water body, becomes of relevant importance to the proper assessment of its polluter potential, of the impacts and also for the determination of control measures appropriate (BRITES et al., 2009) Thus, this paper aims to discuss how urban diffuse pollution can change the quality of surface water and proposed mitigation measures for the control of pollution, intending to conserve the water resources quantitative and qualitative. MATERIALS AND METHODS To develop this work was performed critical review of the literature through consulting of books, journal articles, conference yields, thesis, dissertations, specialization monographs, among other papers, besides sites of organizations, universities and government agencies in search of theoretical approach about the sources of diffuse pollution and its effect on water quality, specifically surface water and groundwater and even alternative management practices with the development of treatment technologies, hydrological modification and pollution control. RESULTS AND DISCUSSIONS Measuring the importance of diffuse sources of pollution in a river basin still involves many uncertainties, because diffuse pollution is difficult to be quantified as it depends on the interaction of several factors, such as intensity and duration of rainfall, soil type, terrain features and use form and occupation of the soil. Besides these factors, other conditions that characterize the diffuse sources also corroborate to the greater difficulty in managing these polluter sources such as the complexity of monitoring pollution loads in their origin point and the release control of these intermittent pollution loads. Thus, it is virtually impossible to establish a correlation between flow and pollutant load and then to specify quality standards for effluent discharge. Therefore, we must choose action over origin point of pollution, rather than just monitor the effluent at release point (REVISTA SANEAS, 2008).

3 12 th International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 There are innumerable polluting activities, whose location is difficult to determine and eliminate, as well as the variability of situations that may occur and their particularities. Thus, the diffuse pollution sources can be found both in rural and urban areas, besides, obviously, by atmospheric depositions (EIGER, et al., 2003). Illegal connections to sewers, septic tank effluent, leaking of underground fuel tanks, waste lubricating oil, paints, solvents and other toxic chemicals dumped into gutters and storm drains also contribute to the increase of pollutant loads transported by urban drainage networks. The pollution generated by flow in urban areas is called of origin diffuse, since it comes from activities that deposits pollutants sparsely on the contribution area of the river basin. Five conditions characterize the diffuse sources of pollution (NOVOTNY, 1991): Launch of the pollutant load is intermittent and is related to precipitation; The pollutants are transported from extensive areas; The pollutant loads cannot be monitored from its point of origin, even because its exact origin is impossible to identify; Control of diffuse pollution source must necessarily include action on the generating area of pollution, rather than including only the control of the effluent at the launch; It is difficult to establish quality standards for effluent discharge, since the pollution load released varies with the intensity and duration of weather event, the extension of production area in that specific event and other factors that make the correlation flow rate x pollutant load virtually impossible to be established. In rural areas the nonpoint sources are mainly the agricultural activities, livestock and minerals, sewage and waste generated by domestic activities (also quite common in urban areas). In agricultural activities the mainly responsible for the pollution load that impair surface water quality are the pesticides and fertilizers used, respectively, for combating pests (insects and rodents) and / or weeds and to improve agricultural productivity. Once these chemicals can keep in soil for long periods of time due to its high persistence and thus be loaded into water bodies becoming a potential risk for humans and animals. Hence the need for proper use of pesticides, always giving preference to products that are less persistent or even the use of other methods of combating pests. However, the diffuse loads from agricultural areas depend besides the use of fertilizers and pesticides, the crop type and the stage of the production cycle, and that the conveyance of such loads to the waterbodies is fundamentally associated with the occurrence of rain events (EIGER, et al. 2003; CERUTI, 2008). The diffuse loads from livestock activities depend on the creation and the technique used, as well as mining activities, which also depend on the type of mined material and techniques adopted for the protection and environmental control, and these activities have a high potential polluter (SEIFFERT, 2000). Already mining activities also depend on type of ore exploitation and techniques adopted for E. Albuquerque & G. Oliveira

4 12 nd International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 the protection and environmental control, and these activities have high pollution potential and are associated with both the operating characteristics of activity and the occurrence of precipitation. In urban areas, nonpoint pollution is mainly from domestic wastewater, liquid effluent, solid residues, movement of vehicles, surfaces washing, eroded areas with bare soil and washing materials construction (EIGER, et al., 2003). The launching of wastewater domestic and industries through improper practices or even by application technologies of liquid wastes in the soil can cause waters pollution both surface and groundwater. But can occur the indiscriminate launching of domestic and industrial sewage (partially treated or not) in water bodies the way direct (as in slums located on the margins of rivers). However, the disadvantages that this type of activity can cause a water body will diversify in terms of adverse effects that can cause water quality of receiving water body, or how this pollution will lead to limitations on the uses of such water. These charges vary daily and weekly cycles with characteristics slightly constant in time (EIGER, et al. 2003; CERUTI, 2008; JORDAN & PESSÔA, 2009). Another very common source of diffuse pollution are stormwater drains which also have significant impact on the environment. Often they are connected to sewage of residence, even clandestinely, they are not always treated adequately, or are rainwater draining poorer areas, where the system of public sanitation and garbage collection are not regular.these rainwater contribute an additional charge equivalent to relevant and primary sewage (JORDAN & PESSOA, 2009). The solid residues disposal in the ground incorrectly (open-air, garbage dumps) and launch right into the bed of the watercourse or storm water drainage network, domestic wastewater and commercial activities (such as fairs, markets, etc.). and industry can also cause several problems of environmental aspects. Thus, it is indicated the use adequate practices of solid residues disposal and removal from landfills and water resources, to prevent leachate (liquid generated from the decomposition of waste) contaminate water (CERUTI, 2008). Residues generated on the wear of pavements, residues tires, oils, lubricants, greases, cleaning of surfaces (lawns and gardens, driveways, roads and large areas), cleaning of construction materials (sand, cement, lime, etc.). public works or private construction (opening of subdivisions, building construction, etc..) are also deposited on the surface of the washed away roads and waterways during rain events (EIGER, et al., 2003). Particles suspended in the air deposited on the surface of roofs, sidewalks and streets and / or directly on the surface of water bodies and rainwater, whose particle, gases and other atmospheric contaminants are dissolved are diffuse sources of pollution of atmospheric origin. However, the nature of these polluting particles depends on the degree of atmospheric pollution and its sources, which may be at significant distances from areas of deposition; also often contain sulfur, metals, organic compounds, nutrients, among others (EIGER, et al., 2003). However, nonpoint depend on local conditions and which cannot always be described in a specific way, in addition, the release of these loads can cause a variety of impacts, which

5 12 th International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 depend on factors like the state of the water body before launch, its assimilative capacity, the amount and distribution of rainfall, land use in the river basin, type and amount of pollutant dragged. Thus, problems are generated from various magnitudes, such as physical changes, sediment deposits, depletion of dissolved oxygen, contamination by pathogenic organisms, eutrophication and harm due to the presence of toxic compounds (REVISED SANEAS, 2008). There are many types of pollutants that may be impacting on superficial water bodies and are commonly associated with diffuse pollution sources, among them the nutrients (nitrogen and phosphorus), which in high concentrations are mainly responsible for the excessive growth of algae (eutrophication). These nutrients are commonly found in domestic effluents and fertilizers (usually applied to excess in agriculture) and are subsequently transported to the surface water bodies causing many problems from eutrophication, such as changes in aquatic ecosystems, reducing the concentration of dissolved oxygen available for bacteria decomposing plants, algae and even physical changes (increased turbidity, color and odor) (REVISTA WATER QUALITY PROTECTION, 2004). The pathogens are also present in these pollutant loads can cause disease and are of fecal origin (human and animal), this group of organisms can include viruses, bacteria and protozoa. A common source of pathogens is solid waste released by animals that obviously are washed, because the runoff reaching surface waters, becoming a risk when present in drinking water (RAFFERTY E SKELLIE, 2005; REVISTA WATER QUALITY PROTECTION, 2004). Contaminants are usually toxic heavy metal compounds, organic and estrogenic substances that can threaten human health and the aquatic environment, due to its high toxicity, persistence and bioaccumulation potential. Are commonly found in fossil fuels, pesticides, industrial effluents, petroleum compounds and others (RAFFERTY & SKELLIE, 2005; REVISTA WATER QUALITY PROTECTION, 2004). In turn, sediment from construction, roads, agriculture, recreational fields, gardens and lawns, that reaches surface water bodies have been generating a series of conflicts within this aquatic environment, as they are deposited the bottom body of water affect the aquatic habitat, carries various pollutants, cause the death of fish (because they feeding these sediments and choking), and cause physical changes, decreasing water clarity (RAFFERTY E SKELLIE, 2005; REVISTA WATER QUALITY PROTECTION, 2004). Of course, it becomes extremely necessary to adopt appropriate management practices, aimed, mainly monitoring of effluent reaching the receiving bodies and also those of rainwater, which are higher loads of pollutants. Therefore, unless management can derail any project that has pretension to get better water quality. E. Albuquerque & G. Oliveira

6 12 nd International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 As LIMA (2001), some alternatives may be adopted, especially in urban areas such as best management practices, such as hydrological changes, the emission control and treatment of stormwater, is the first consists in control diffuse pollution emitted and transported to surfaces flow through, for example, permeable pavement that are quite effective, since it reduces hydroplaning, retain more water, are inexpensive and are very effective in flood control and reduction of diffuse pollution. Control the emission of pollutants can occur through infiltration ponds (where the runoff is stored temporarily before being filtered by the soil), infiltration trenches (deep excavations which act as underground storage tank) and swales with vegetation (remove sediment and other pollutants from runoff through filtration, deposition, infiltration, absorption, adsorption, decomposition and volatilization) among other examples. In turn, treatment of stormwater, which when used should be integrated into a comprehensive system of storm water management. An example of treatment are sand filters consist of a sand bed where the flow travels and it is retained in the colloidal particles, the grit chambers and other technology effectively responsible for the retention of sedimentary particles. However, treatment of stormwater should be viewed as the last solution to combat diffuse pollution (REVISED WATER QUALITY PROTECTION, 2004). However, diffuse sources of pollution are difficult to be monitored, so in addition to good management would be ideal that the people also collaborate changing daily habits to reduce emissions of these pollutants and prevent them from entering into bodies of superficial waters. Some examples can be cited as good practice in prevention, such as choose native plants for the garden because they are more tolerant of local conditions by reducing the need for fertilizer application, or when necessary to use organic produce, to recycle water in your back yard ; preserve as much green areas, thus reducing runoff, conserve water used in daily activities of the residence and wash vehicles on pervious surfaces, and where possible give preference to public transport, decreasing the emission of pollutants, among other changes that may auxiliary in reducing diffuse pollution (REVISED WATER QUALITY PROTECTION, 2004). CONCLUSIONS The diffuse pollution is difficult to control and results of the changes that man causes in the environment, being dispersed mainly by water drainage in urban areas. Shows great variability in the concentration of pollutants released into water bodies, for there is great variability among river basin precipitation events, and their loads of pollutants are related to the type of land use in the river basin. Noted that diffuse pollution is almost always responsible for the causes of pollution in superficial waters, however it is difficult to predict the temporal distribution of concentrations of these pollutant loads, thus, in most studies of nonpoint source pollution is

7 12 th International Conference on Urban Drainage, Porto Alegre/ Brazil, September 2011 the main objective assessing the impact of the stormwater launch on the receiving body, which is also a solution difficult to quantify. In general, the origin of diffuse pollution in urban areas is very diverse, being the main contributors to the sanitary sewage from irregular, accumulated garbage in the streets and sidewalks, organic waste, construction activities, waste fuel, oils and greases, air pollutants, etc. The main pollutants that are washed away so are sediment, organic matter, bacteria, metals such as copper, zinc, manganese, iron, lead, hydrocarbons from oil, toxics such as pesticides and air pollutants that are deposited on the surfaces. In rural areas the main pollutants are organic compounds generated from pesticides and fertilizers, waste with high nutrient load, high oxygen demand, suspended solids and pathogens such as viruses, bacteria and protozoa. Toxic contaminants are usually heavy metal compounds, organic and other substances. The discharge of these pollutants in superficial waters and groundwater degrades heavily quality, which may permanently affect the use of groundwater for certain purposes, or raising costs to its adequate classification. Thus, it becomes indispensable to implement best management practices to ensure water quality in the receiving environment, always considering the occurrence of so-called wash load (first flush) that this is the first rains, so the initial removal of material accumulated in the drainage system in the period between rainfall and eventually moving into the receiving bodies. However, management practices combine with pollution prevention habits would be the most suitable alternative in the long term, since it requires less maintenance and greater cost effectiveness. REFERENCES Ceruti, F. C. (2008). Apostila da disciplina de gestão de recursos naturais. UNICENTRO, Engenharia Ambiental, Irati Pr, 37p. Choe, J.S.; Bang, K.W.; Lee, J.H.(2009). Characterization Of Surface Runof In Urban Areas. Water Science And Technology. In: Brites, Ana Paula Zubiaurre; Gastaldini, Maria Do Carmo Cauduro. Avaliação da carga difusa da drenagem pluvial urbana na bacia hidrográfica cancela. Anais 23º Congresso brasileiro de engenharia sanitária e ambiental. Eiger, S.; Aranha, C. H,; Gomes, M. C. De A,; Perez, L. S. N,; Neto, A. S. B. Modelagem matemática de cargas difusas na bacia do guarapiranga, São Paulo. Universidade De São Paulo-USP. EPA - Environmental Protection Agency (1997). Guidance specifying management measures for sources of nonpoint pollution in coastal waters. Disponível Em < Acessado Em 08 De Julho De Haupt, Jaqueline P. O. (2009). Metodologia para avaliação do potencial de produção de poluição difusa: estudo de caso da bacia do rio Jundiaí. Dissertação De Mestrado - Escola Politécnica Da Universidade De São Paulo, São Paulo SP. Jordão, E. P.; Pessôa, C. A. (2009). Tratamento de esgotos domésticos. 5ª Ed. ABES. Rio De Janeiro p. E. Albuquerque & G. Oliveira

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