Oilfield produced water assessment from onshore treatment facilities in Niger Delta: Water quality susceptibility and suitability for soil irrigation

•Assessment of physicochemical properties of oilfield produced water was studied.•Suitability of treated-PW for soil irrigation was investigated.•Treated-PW was close to or within approved NUPRC standards except in few cases.•Reclaimed PW did not conform totally with US EPA standard.•Treatment facilities should be integrated to improve their efficiencies. The abundance of natural fossil fuel in the Niger Delta of Nigeria has instituted generation of oilfield produced water (PW) in large volume. This constitutes environmental pollution when discharged outside the permissible limit given by Nigerian Upstream Petroleum Regulatory Commission (NUPRC). PW can be used for soil irrigation if its constituents are remediated after treatment. This research assessed the physicochemical properties of untreated and treated samples of oilfield PW from Awoba, Imo River and Kolo creek oil fields of Niger Delta using electrometric, argentometric, colorimetric, titration, atomic absorption spectroscopy, APHA and HACH standard methods. Oil-treatment facilities effectiveness was investigated by comparing laboratory results for treated-PW with the permissible regulatory values of NUPRC. The pH, salinity hazard, sodium hazard, boron, chloride, TDS, carbonate and nitrate of treated-PW were measured to check the suitability of treated-PW quality for soil irrigation. Measured values were compared with the permissible standard of US EPA. Sodium adsorption ratio (SAR) and electric conductivity (EC) were used to determine the level of sodium and salinity hazards respectively. The results indicated that none of the untreated-PW samples complied with NUPRC permissible limit. Physicochemical properties of treated-PW revealed samples to be close to or within approved NUPRC standards except in few cases. All the measured parameters of treated-PW from Awoba and Imo River oil fields conformed to the US EPA standard value except their ECs and SAR of Imo River oil field which measured 2.46 and 2.93 ds m−1, and 2.57 respectively. However, all other parameters measured for treated-PW from Kolo creek oil field did not conform to the standard except pH and nitrate which measured 7.7 and 4.86 mg/L respectively. In conclusion, oil treatment facilities should be more robust to degrade a wide range of recalcitrant compounds in PW pollutants in order to minimize the impacts of toxic compounds in PW on the environment.