Impact of green roof plant species on domestic wastewater treatment

Abstract Green roof is one of the nature-based solutions to provide environmental and social benefits for sustainable urban development. Green roofs irrigated with domestic wastewater solves not only their irrigation water resource but also the urban wastewater treatment. However, it is unknown whether the capacity of green roofs in pollutant removal meets the requirement of domestic wastewater treatment. This study was to investigate the capacity of pollutant removal by the green roofs with C4, C3, and CAM plant species when irrigated with domestic wastewater. Results showed that green roofs removed 79.27~97.38% of total suspended solids, 79.94~98.92% of chemical oxygen demand, 65.26~90.52% of total nitrogen, 83.32~96.31% of ammonium nitrogen, 77.83~93.97% of nitrate nitrogen, and 93.77~98.94% of total phosphorus, respectively. C4 and C3 plants contributed significantly higher runoff reduction, removal of total nitrogen, chemical oxygen demand, total nitrogen, ammonium nitrogen, nitrate nitrogen, phosphates, and total phosphorus than CAM plants. Water quality indicated by chemical oxygen demand, total nitrogen, ammonium nitrogen, and total phosphorus from the effluent complied with the widely accepted limits on domestic wastewater discharge. Our results demonstrate that green roofs can be designed for the ecological treatment of domestic wastewater on the household scale.