Abstract
The aquatic contamination from the discharge of untreated or inadequately treated municipal sewage, as well as from husbandry, agriculture, and the disposal of municipal garbage, metallic scraps and civil architecture residues in the neighborhood of the Turvo Limpo River basin was evaluated. The water-courses examined were the Sao Bartolomeu Stream, Turvo Sujo River, and Turvo Limpo River, located in the Minas Gerais State, Brazil. Water samples were collected at the river-side in the dry season (July, August, and September 2005) and analyzed for evaluation of pollutant inputs. The pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), total phosphate, total ammonia nitrogen (NH3 + NH4+), nitrate and metal concentrations (Al, Ca, Cr, Cu, Fe, Mg, Ni, Pb, and Zn) in water samples were determined. The concentrations of these metals in the suspended solids were also determined. The suspended solids showed high concentrations of Zn (15,350 mg kg-1) and Pb (3,590 mg kg-1), while the stream water was enhanced with Al (1,480 µg L-1). The pH and the concentrations of BOD, total phosphate and total ammonia nitrogen in the water-courses were far from those established by the Brazilian Environmental Standards for Class 2 water. In all examined sites there was an increase in the nitrate concentration compared with that of a spring (site 1). The nitrate concentrations were below those of the total ammonia nitrogen, indicating that the nitrogen in the water-courses was mainly originated from recent sewage discharges, since did not occurred larger mineralization with the formation of nitrate ions.
Highlights
The discharge of untreated or inadequately treated domestic sewage into aquatic environments can cause deleterious effects to health
The pH values of sites 1, 8 and 9 are far from those set by river water standards, i.e., from 6.0 to 9.0.10 The low pH levels can be explained by the local geological characteristics
Site 2 is located near a vegetable cultivation area and the stream water from this site is pumped to the water treatment plants of both Viçosa city and the Federal University of Viçosa
Summary
The discharge of untreated or inadequately treated domestic sewage into aquatic environments can cause deleterious effects to health. The introduction of biodegradable organic matter in water systems decreases the level of dissolved oxygen,[1] which is one of the more important parameters available in the field of water pollution control, as it permits the evaluation of the aerobic conditions of a water-course, which receives discharge of pollutants. The discarded materials contain potential toxic constituents, few efforts to purify water have been conducted in the Turvo Limpo river basin at Minas Gerais State, Brazil. 2001, only 52.2% of the Brazilian municipal districts had conventional treatment of sewage effluents.[2] only 0.9% of the municipal districts at Minas Gerais State, Brazil, treat adequately sewage effluents.[3]. Efficient waste management practices that include potential hazard minimization, recovery operations and treatment prior to stream emissions should be implemented
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