Performance Review of Hybrid Subsurface Constructed Wetlands in Urban Wastewater Supplementary Treatment

Today, the use of refined urban wastewater for agriculture is growing considerably. One of the methods for the natural treatment of wastewater is the constructed wetland. In this study, the effects of three and six days retention time on the vertical, horizontal and hybrid constructed wetland (first vertical and then horizontal) with perlite beds and Cyperus plants on the urban wastewater were investigated. In this study, horizontal wetlands were designed with 0.75 m width, 0.5 m depth and 6 m length; the vertical wetlands were designed as cylinders with a diameter of 0.7 m and the height of 1.2 m. On average, for the three days retention time, in the wetland with the vertical flow, 5the horizontal flow and the hybrid wetland, nitrate was 31.0, 36.7 and 56.3 percent, ammonium was 7.6, 32.7 and 37.8 percent, and the fecal coliform was decreased by 53.3, 93.4 and 96.9 percent, respectively. Also, during the six days retention time in the wetland with the vertical flow, the horizontal flow and the hybrid wetland, nitrate was 45.7, 58.5 and 77.5 percent, ammonium was 16.8, 75.2 and 79.4 percent, and fecal coliform was decreased by 58.0, 97.5 and 99.0 percent, respectively. Overall, the results showed that constructed wetland with perlite beds and Cyperus plants had a good function in removing pollutants, especially fecal coliform.