Impactos da poluição e contaminação das águas da microdrenagem urbana deficiente no corpo receptor

Abstract

Rainwater management is done through urban drainage, which captures, drains and directs it to the receiving water body. When the system is constructed properly, it does not interfere with contamination, river pollution or the spread of diseases, also avoiding the intense transport of solid waste and supporting the volume of rainwater that the structure will receive so as not to cause flooding. In Crateús/CE, the drainage system is characterized by an absolute separator type structure, which is the most suitable, where there is separation of rainwater and sewage, and interconnections between the sanitary sewage system and rainwater drainage were identified. Given this context, the main objective of this work is to analyze the impact of water from urban microdrainage in the city of Crateús/CE, on contamination and water pollution of the Poti river, the receiving water body, through physical-chemical, bacteriological analyzes and tests ecotoxicological tests with Allium cepa (onion) and Lactuca sativa (lettuce) seeds. To this end, samples were collected at four points in the Crateús urban drainage system. The physicochemical and bacteriological analyzes were carried out in partnership with the Regional Laboratory of UNBSC (Business Unit Bacia dos Sertões de Crateús) of Cagece (Companhia de Água e Esgoto do Ceará) following standardized methodologies. For ecotoxicity tests, 10 seeds of each species were placed in Petri dishes (90 mm in diameter), on filter paper to serve as a base, and exposed to 5 ml of each sample. Then, the plates were wrapped in film paper to minimize moisture loss. All plates were placed in a cardboard box, kept at a temperature of 25 ± 2ºC, in the dark, for 120h. Every 24 hours, the seeds were monitored to record germination and, at the end, the length of the radicle and hypocotyl was measured with the aid of a digital caliper to analyze growth inhibition. The results of the calculations for the ecotoxicological test showed that the effluent analyzed presented a low level of toxicity, with a stimulus for seed germination due to the presence of nutrients in the medium. The physical-chemical and bacteriological tests showed a higher level of toxicity as they showed results above reference values, considering the parameters studied and signaling the presence of sewage in the network. Ammonia, for example, was approximately 27 times higher than the reference value and Dissolved Oxygen (DO) was approximately 8 times lower at point 2 (Elevation Station). For total coliforms, the increase of 19 million was more significant and for E.coli it increased by almost 9 thousand times, both at point 1 (Poti river). This compromises unique health, being a risk to sustainability, which allows the spread of diseases through these waters, contributing to the contamination and pollution of water bodies and, consequently, increased costs in the public health network.