Urban wastewater treatment through a system of green filters in the Montañita commune, Santa elena, Ecuador

Abstract

In land application, soil is used as a natural filter to remove pollution from urban wastewater. The soil also has two other functions, first of all it’s the receiving medium of wastewater and secondly it works as an active agent because physical, chemical and biological reactions are made in the soil–water–crops ecosystem. This non-conventional treatment is effective at removing pollutants such as suspended solids, organic matter, nitrogen, phosphorus and microorganism form effluent streams. The aim of this study is to design a pilot plant using soil as a natural filter for the treatment of wastewater discharge from oxidation ponds located in the Montañita commune through selecting and evaluating the site, calculating the design hydraulic load and the area necessary for system application. To take samples at different depths, a lysimeter was constructed that allowed to take samples at 30, 60 and 90 cm of depth. The variables that were measured in the treated water were total coliforms and BOD5. These variables were related to the values calculated for the discharge of the oxidation ponds and the percentage of removal for each sample taken. As a result, high removal percentages were obtained at 90 cm depth with respect to the level of application of the residual water. Percentages of up to 79% for total coliforms and 80% for BOD5 were obtained. These results are consistent with the limits established in the UTSLME (Unified Text of the Secondary Legislation of the Ministry of Environment). Finally, it could be concluded that soil in the area where the land application pilot plant was developed is suitable for efficient removal of the contaminants present in the discharge of oxidation ponds. This system contributed to the reduction of the pollution generated; in addition, the treatment of wastewater helps reforestation of this arid zone.