Association of septic tank and sand filter for wastewater treatment: full-scale feasibility for decentralized sanitation

Worldwide, 70% of the individuals who do not have access to sanitation facilities live in rural areas. A solution for these areas is the use of decentralized systems for wastewater treatment. However, most of the studies about this topic are performed in a laboratory or in pilot scale. This work investigated a full-scale decentralized system. The association of septic tank and sand filter was installed in a rural area in Brazil. Its feasibility, maintenance, and operational conditions were appraised. The septic tank was built with precast concrete rings (inner diameter: 1.90 m; total depth: 2.34 m; useful volume: 4.30 m3). The sand filter was also constructed with precast concrete rings (internal diameter: 1.90 m; surface area: 2.84 m2) and effluent application was intermittent. The hydraulic loading rate of the sand filter was 253 Lm−2day−1. The quality of the effluent met the legal aspects and the system proved to be effective for decentralized sanitation. The final effluent may be reused in agricultural activities; however, the frequency of maintenance of this system should be taken into account.