Swine Wastewater Treatment System Using Constructed Wetlands Connected in Series

The main objective of this study was to analyze the efficiency of CWs for purifying swine wastewater in order to reduce its pollutant load. The system included a pretreatment module (raw swine wastewater tank, phase separator, and settlement tank), and three constructed wetlands connected in series and planted with Phragmites australis and Suaeda vera. Three treatment cycles were carried out with a total hydraulic retention time in the wetland of 21 days for each cycle. Pig slurry samples were collected in triplicate after each treatment module, and physical–chemical analyses were performed. The results showed that the phase separator decreased the suspended solids, turbidity, and the chemical oxygen demand in the treated swine wastewater. The system enabled considerable nitrogen reductions (Kjeldahl nitrogen, NH₄⁺, and organic nitrogen), and the highest removal was reported in the wetlands. However, the cations and anions showed different efficiencies. In some cases (Ca, Mg, and Na), the final concentrations were increased, which could be explained by their release from the substrate; however, there were no statistical differences among the CW effluents and the raw pig slurry. Therefore, the integral pig slurry treatment system with constructed wetlands increased the quality of the treated swine wastewater and thus can be used for its sustainable agronomic valorization. This thereby enables savings in inorganic fertilizers and irrigation water.