An interval steady-state multimedia aquivalence (ISMA) model of the transport and fate of chloridion in a surface flow constructed wetland system treating oilfield wastewater in China

A surface flow constructed wetland (SFCW) system was built up to treat oilfield wastewater after secondary treatment. Chloridion (Cl−) in the wastewater was selected as an indicator to investigate the transport and fate of inorganic salts at high levels in the multimedia environments (air, water, soil, flora, and groundwater) by developing an interval steady-state multimedia aquivalence (ISMA) model. The modeled Cl− profiles were in good agreement with the measured ones, as indicated by the interval average logarithmic residual errors (IALREs) (<0.6 logarithmic units). The modeled results showed that the Cl− accumulated in the soil (70.80%) and was outputted from the environmental system mainly through periodic collection (34.86%) and advection outflow in groundwater (33.03%). It was also proved from imagery interpretation that the saline soil area was reduced 5.52% after wastewater irrigation, indicating that the tertiary treatment of oilfield wastewater through the constructed wetland was contributed to the local ecological restoration.

► Treatment of oilfield wastewater by a surface flow constructed wetland system.
► Development of an interval steady-state multimedia aquivalence (ISMA) model.
► Simulation of Cl− transport and fate in the multimedia environments.
► Restoration of local ecological environment by wastewater irrigation.