Hydraulic characterization and removal of metals and nutrients in an aerated horizontal subsurface flow “racetrack” wetland treating primary-treated oil industry effluent

Constructed wetlands (CW) are an attractive technology due to their operational simplicity and low life-cycle cost. It has been applied for refinery effluent treatment but mostly single-stage designs (e.g., vertical or horizontal flow) have tested. However, achieve a good efficiency industrial effluents, different conditions (both aerobic anaerobic) needed. This means that hybrid CW systems typically required with respectively increased area demand. In addition, strong environment facilitates the formation of iron, manganese, zinc aluminum precipitates cannot be established passive wetland systems, while role these oxyhydroxide compounds in further co-precipitation removal heavy metals such as copper, nickel, lead, chromium can simplify overall wastewaters is poorly understood CW. Therefore, this study tests first time innovative design combines artificially aerated section non-aerated single unit oil wastewater treatment. Four pilot units were tested (i.e., planted/unplanted, aerated/non-aerated) (two hydraulic loading rates) characteristics estimate plants artificial aeration identify optimum configuration. The received primary effluent, i.e., after passing through dissolved air flotation unit. first-order under evaluated, along phenols nutrients. High rates Fe (96–98%), Mn (38–81%), Al (49–73%), Zn (99–100%) generally found, Cu (61–80%), Ni (70–85%), Pb (96–99%) Cr (60–92%) was also observed, likely co-precipitation. Complete ammonia nitrogen found. rate coefficient (k) calculated from collected data demonstrates represents advanced reaching higher at smaller demand than common systems.