PILOT-SCALE CONSTRUCTED WETLAND TREATMENT SYSTEMS FOR BENEFICIAL REUSE OF OILFIELD PRODUCED WATER, AFRICA

An oilfield in Africa generates low salinity produced water that is disposed of by injection. During the dry season the agricultural area adjacent to the oilfield is short on fresh water for irrigation. The area is sparsely populated, mostly desert, and economically poor. Some constituents in the produced water may limit reuse unless treated. The potential for social and economic benefits exists if an effective and low cost method can be found to treat the produced water. This research focused on four objectives: 1) determine the requirements for beneficial water reuse; 2) compile water reuse guidelines into a searchable database; 3) compare analytical data from the produced water to water reuse guidelines to discern constituents of concern (COCs); and 4) design pilot scale constructed wetland treatment systems (CWTSs) for removal of the COCs. Organic and inorganic requirements were determined for water reuse for irrigation, watering livestock, aquaculture, and drinking (potable water). A searchable database of water reuse guidelines was created to assist in decisions regarding water treatment and beneficial reuse. Zinc and polycyclic aromatic hydrocarbons (PAHs) were identified as potential COCs in the produced water. Pilot-scale CWTSs were designed and built to remove COCs using specific biogeochemical processes to transfer and transform the COCs. The design targeted synthetic produced water for zinc removal by sulfide formation and sorption and oil and grease removal by oxidation. For two pilot-scale CWTSs, subsurface flow wetland reactors were planted with Phragmites australis (common reed). Surface flow wetland reactors in a third pilot-scale system were planted with Typha latifolia (cattail). Hydrosoil characteristics and hydraulic retention time were selected to promote targeted biogeochemical processes. Following construction, plant density and oxidation-reduction potential of hydrosoil were monitored to evaluate acclimation and treatment readiness of the systems. This study provided encouraging results regarding beneficial reuse of produced water.