Refinery wastewater contains a complex pollutant load (hydrocarbons, phenols, heavy metals, sulfides) that requires advanced treatment before discharge. This study evaluates the effectiveness of a treatment system by analyzing physicochemical and bacteriological parameters based on the Water Quality Index (WQI) and the Inorganic Pollution Index (IPO). The methodology employed allowed for 61 days of monitoring at four treatment plant stations. The parameters analyzed included COD, TSS, hydrocarbons, volatile phenols, sulfides, ammonia nitrogen, heavy metals (Pb, As, Cr), and pH. The methods used combined UV spectrophotometry, ICP, and colorimetric tests. The primary treatment reduced COD by 85% and hydrocarbons by 92%. Secondary treatment maintained residual COD at 45.2 mg/L and phenols at 0.15 mg/L. At the outlet, regulatory compliance exceeded 95% for all parameters, with removal rates of 93% (COD), 98.8% (hydrocarbons), and 99.4% (phenols). The IPO and IQE indices confirmed a significant improvement in water quality after treatment. The performance demonstrates the effectiveness of a combined physicochemical and biological approach. Some variations in inlet pH and sulfide levels indicate the need for appropriate pretreatment. The use of the IQE/IPO indices facilitates environmental monitoring and decision-making. The treatment system studied is effective in meeting petroleum wastewater discharge standards. Targeted optimizations, particularly regarding pH regulation and sulfide monitoring, could further improve its performance. This study provides a methodological framework applicable in similar contexts, particularly in the Sahel region.
Adannou et al. (Tue,) studied this question.