Wastewater quality index (WWQI) as an indicator for the assessment of sanitary effluents from the oil and gas industries for reliable and sustainable water reuse

Abstract

With the development of numerous industries, the increasing use of water resources and the discharge of pollutants into the environment, particularly industrial wastewater, has become extremely important. The purpose of this study was the assessment of sanitary wastewater treatment plants attributed to the oil and gas industries as reliable and sustainable water resources based on the wastewater quality index (WWQI). The findings revealed that the facilities under investigation effectively process and discharge their effluents following the Environmental Protection Organization's standards. Springtime has the maximum removal in wastewater treatment plants (WWTPs), with typical removal values of COD and BOD5 of 96.1% and 97.1%, while pH in the effluent of these WWTPs was 7.22, and DO in the range of 1–6.3 mg/L throughout this period. In addition, fecal coli removal efficiencies were 98.6%, respectively. Finally, the wastewater treatment system in the four refineries investigated has resulted in a considerable decrease in microbiological and organic pollutants in conformity with environmental regulations permitting wastewater reuse for irrigation and agriculture, as well as discharge into adsorption wells. However these treatment plants perform poorly in terms of cumulative and WWQI models (13.86–16.05), it is clear from the results and discussion of this research that the results of the treated wastewater from the under-investigation plants comply with the Environmental Protection Organization of Iran's standards required for discharge to surface water or reuse in agricultural land irrigation. Still, the treatment system should be constantly audited and improved to reach a higher rank according to the WWQI.