TANQUE DE EVAPOTRANSPIRAÇÃO NO TRATAMENTO DE ESGOTO SANITÁRIO EM COMUNIDADES RURAIS

Abstract

Brazil has more than 19 million rural residents without sewage collection or treatment, which corresponds to 62% of the rural population. The lack of sewage collection networks leads to the extensive use of black sumps, and the consequent contamination of soil and water resources. Given this, the search for low cost technologies, easy to implement and management is essential. An alternative technology to conventional methods that has been shown to be quite effective is the evapotranspiration tank (TEvap). The system consists of a waterproofed tank, filled with different layers of substrate and plants. However, it is recommended to avoid vegetables that have eaten raw roots and creeping vegetables. However, there are no studies on the development and microbiological safety of species such as lettuce, arugula and radish in TEvap. Therefore, this study aimed to evaluate the development, chemical and microbiological composition of vegetables produced in different positions of the TEvap system for black water treatment. The system was implemented in the rural area of ​​Monte Carmelo / MG, with capacity to serve four permanent residents. Agronomic (height, diameter, yield), chemical (% dry mass; pH; electrical conductivity; phosphorus and total nitrogen) and microbiological (thermotolerant and total coliforms) parameters of lettuce and arugula were evaluated at the beginning, end and outside of TEvap. (witness). The estimated cost for TEvap is approximately R$ 1.150,00 for the Monte Carmelo region. Lower than estimated value for conventional septic tank and biodigester septic tank systems. There was a significant linear effect on lettuce diameter and arugula height as a function of time. Lettuce presented larger diameters when cultivated in TEvap, regardless of its position. Already the arugula had higher heights in the early part of TEvap compared to the final part and the witness. Productivity and chemical composition of lettuce and arugula did not differentiate between the crops at different positions of TEvap and the control. All coliforms found in the samples are thermotolerant. At the beginning of TEvap the lettuce presented the highest concentration of coliforms. From the lettuce and arugula samples from the different TEvap positions, only 50% of the lettuces were adequate for human consumption at the end of the system. However, irrigation water was possibly the main vehicle of vegetables contamination. Therefore, although the system demonstrates efficiency in the treatment of black water, it should also be concerned with the quality of irrigation water for safe food production.