Avaliação da qualidade da água de poços artesianos utilizados no abastecimento público do município de Carlos Gomes-RS, através de análises físico-químicas, microbiológicas e testes toxicológicos

Abstract

Groundwater availability and the growing demand for drinking water accentuate the exploitation of aquifers, often causing them to be contaminated, and therefore the issue of groundwater quality has become increasingly important for the management of water resources in Brazil. The objective of this work was to evaluate the groundwater quality used for the public supply of the municipality of Carlos Gomes, located in the north of Rio Grande do Sul through physical-chemical, microbiological and toxicological analyzes of the water of three artesian wells in the municipality. The water samples were collected in three months in the year of 2017. In addition, the land use and occupation map were elaborated to establish possible relationship between land use and groundwater quality. The following parameters were analyzed: turbidity, electrical conductivity, temperature, pH, dissolved oxygen, alkalinity, phosphorus, total solids, chlorides, hardness, nitrate, nitrite, ammoniacal nitrogen and organisms indicating microbiological contamination (total coliforms and Escherichia coli). Toxicological tests (acute and chronic) were performed with the microcrustacean Daphnia magna. In the physical-chemical tests, the nitrate parameter presented values above the maximum allowed by the legislation for wells P1 and P3 in the month of June and close to the maximum allowed for P2 in the month of July. Regarding microbiological tests, P2 presented total coliforms and should receive disinfection treatment by chlorination. The acute and chronic toxicity tests with D. magna were carried out with samples from June, due to the high nitrate values. Samples from the three wells did not cause acute toxicity to D. magna. On the other hand, the chronic toxicity test had chronic effects on the average reproduction in organisms exposed in raw water of the P1 and P2 wells and chronic effects on the growth in organisms exposed in the crude sample of P1. P3 had no chronic effects, but had the highest number of males and the females who survived the test produced the highest quantity s in the bioassay. The surviving organisms were observed in magnifying glass and showed no morphological deformations. The wells located in agricultural area had higher values of phosphorus compared to the well located in urban area, which presented higher values of chlorides, electrical conductivity, hardness, alkalinity, total solids and in the month of June, higher values of turbidity. Due to the risks of constant water intake with high concentrations of nitrate, a constant monitoring of the groundwater of the municipality of Carlos Gomes - RS is required.