Sunflowers (Helianthus annuus L.) on Top of a Constructed Wetland as an Engineered Ecosystem to Clean Sewage Onsite

Abstract

The three main components of chemical fertilizers for field crops are nitrogen, phosphorus, and potassium, and they are considered limiting factors to plant growth. The concentration level of these macronutrients on treated wastewater effluents is considered appropriate to support crop production. The purpose of this case study was to use a real-scale model to treat and reuse sewage onsite using a recirculating vertical flow constructed wetland (RVFCW) as an engineered ecosystem planted with sunflowers (Helianthus annuus L.). Effluents from both the septic tank and the RVFCW were analyzed for water quality variables. Treatment efficiencies (removal) were high for fecal coliform bacteria (98%), biochemical oxygen demand (98%), ammonium-nitrogen (97%), total Kjeldahl nitrogen (96%), total suspended solids (92%), total nitrogen (77%), and total phosphorus (76%), while they were relatively low for potassium (38%). These results show that sunflowers growing on top of the RVFCW could be a sustainable alternative technology and a green mechanism to remove pollutants from sewage. A nutrient recovery through the direct use of sewage as fertilizer and water reuse is feasible.