Natural wastewater treatment system for a gastronomic tourism business in a flood-prone area: Performance and operational challenges

Abstract

Treatment wetlands have been studied and applied for decades in different configurations for the purification of many wastewaters; however, their application in natural wetland areas and other potentially floodable zones presents additional challenges. The objective of this work is to evaluate a nature-based treatment system, developed for the purification of wastewater from kitchen and bathrooms generated by a gastronomic tourism venture located in a natural wetland area (lower Paraná River Delta islands, Argentina), with the focus in some relevant physical and chemical water quality variables and operational issues. The hybrid system consists of a series of pretreatments (biodigesters, grease trap), a septic tank (ST), a horizontal subsurface flow wetland (HFW), and a maturation pond (MP). During flood events, the HFW can operate by tidal flow, storing wastewaterfor later discharge during base flow to prevent surface water pollution by partially treated Wastewater. During monitoring period (9 months) the ST and HFW stages allowed for efficient removal of total suspended solids (81 %) and chemical oxygen demand (73 %). A significant reduction (p < 0.05) in anionic surfactants levels was also observed, mainly due to the MP stage. For ammoniacal nitrogen, soluble reactive phosphorus, and fats, oils and greases, there was a trend to decreasing concentrations toward the final treatment stage, although no significant differences were found between sampling points (p > 0.05). The autochthonous plant species planted in the HFW grew vigorously and without observable signs of phytotoxicity. The operational challenges encountered are discussed, particularly those related to pumping and overall system operation under flooding conditions. Some improvements are proposed to optimize the application of this type of system in other flood-prone areas and to reuse treated water, plant biomass, and nutrients.