Effects of Vegetation and Temperature on Nutrient Removal and Microbiology in Horizontal Subsurface Flow Constructed Wetlands for Treatment of Domestic Sewage
The promotive effect of constructed wetlands (CWs) with polyculture on treatment efficiency is still a controversial problem. Additionally, there is limited information regarding the influence of temperature on CWs. In this study, the influence of vegetation type, different NH4+-N loading rates, and environmental temperatures on performance of CWs were investigated. Results of different vegetation type indicated that removal of NH4+-N and total phosphorus (TP) in polyculture was higher than other CWs. In polyculture, tested nutrients had removal percentages greater than 94.5%. Results of different NH4+-N loading rates demonstrated that NH4+-N was almost completely removed (around 99.5%) in polyculture under both NH4+-N loading rates. Temperature could substantially influenced the performance of CWs and the removal percentages of NH4+-N, NO3+-N, total nitrogen (TN), and TP in all CWs tended to decrease with a decline of temperature. Especially, a sharp decline in the removal percentage of NO3−-N of all CWs (greater than 39%) was observed at low temperature (average temperature of 8.9 °C). Overall, the polyculture also showed the best performance with the decline of temperature as compared to other CWs. This study clearly documented that polyculture was an attractive solution for the treatment of domestic sewage and polyculture systems were effective for domestic sewage treatment in CWs even at low temperature (8.9 °C).