Avaliação de sistema de tratamento da água cinza e reúso da água no semiárido brasileiro

Abstract

The inadequacy of sewage systems in Brazil has compromised the health of rural and urban populations and the environmental quality. Considering this scenario and together with the scarcity of good quality water, it has been stimulated the agricultural use of wastewater for production of vegetables as well as other agricultural crops. This work aimed at the evaluation of a treatment plant for gray water using ultraviolet (UV) radiation in the disinfection of effluents and the hydraulic performance of drippers using gray water. A plant for the treatment of gray water was constructed in the Monte Alegre I Settlement Project, municipality of Upanema, midwestern region of the state of Rio Grande do Norte, and a reactor was equipped with ultraviolet lamps and installed in the Zoobotanical Park (PZO) of the Federal Rural University of the SemiArid Region (UFERSA), in Mossoró, state of Rio Grande do Norte. The treatment plant consisted of a passage box, a septic tank, an organic filter and a storage reservoir, and the artificial ultraviolet reactor was built in brick masonry in the dimensions of 1.08 m width, 1.18 m length and 0.40 m depth, containing two germicidal lamps (30 W, 254 nm). The treatments used to analyze the effect of UV radiation consisted of three slides (0.10 m, 0.20 m and 0.30 m) and five exposure times of (0, 1, 2, 3 and 4 h). For evaluation of the treatment system, we collected samples of the effluents at different sites of the system and analyzed them for physical, chemical and microbiological characteristics; the effect of UV radiation was investigated through the decay of the microorganisms. Data were evaluated using parametric (univariate) and non-parametric (multivariate) statistics, according to the complexity of the data set. During the experimental period, the performance of the irrigation system was analyzed by means of the mean flow (Q), flow variation coefficient (CVQ), distribution uniformity coefficient (CUD) and statistical uniformity coefficient (Us). The treatment plant was efficient in removing most of the characteristics analyzed, since they were within the standards set forth by the current legislation. The evaluation of the irrigation system evidenced the development of a biofilm in the dripper as well as the presence of microorganisms. The radiation effect was satisfactory however the radiation dose has to be calculated to improve the efficiency of the treatment. The set a passage box, septic tank, organic filter and ultraviolet radiation reactor provide a degree of gray water treatment that allows the irrigation of vegetables through a drip irrigation system, but drip clogging control measures are required to ensure maximum performance