Gray water treatment for agricultural reuse in the semiarid of Rio Grande do Norte, Brazil

Abstract

The reuse of gray water is an effective measure to face the difficulty of irrigation in the northeastern semi-arid region, considering that, with its practice, there is an decrease in the consumption of drinking water for agricultural irrigation. Therefore, the present work aimed to evaluate the treatment of gray water for reuse in a family farm in the semiarid region of Rio Grande do Norte. To assess the treatment of the effluent, raw and treated sewage were collected, evaluated and treated in the vermifilter of the family farm, where the pilot project used in this work is installed. The physical-chemical and microbiological properties of the effluent were elaborated through the parameters: temperature, electrical conductivity, pH, suspended solids, ammonia nitrogen, organic nitrogen, total Kjeldahl nitrogen (NTK), nitrate, total phosphorus, soluble orthophosphate, five-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD), dissolved oxygen and thermotolerant coliforms. The results indicate that there was a significant removal of Total Suspended Solids (TSS), COD, BOD5, and thermotolerant coliforms. Considering that the reduction of these concentrations allows agricultural reuse and that the biological treatment system used proved to be efficient in removing these parameters, it is clear that the treatment of gray water is a fundamental tool in guaranteeing the quality of life of the population, especially for those who live in rural areas and suffer from water scarcity. In addition, the system has low maintenance and operation costs, reduced fertilization costs, savings in potable water, reduced environmental pollution and preservation of the environment.