Impact of olive mill wastewater on the operational efficiency of wastewater treatment plants in the Gaza Strip

The improper disposal of olive mill wastewater (OMW) presents a significant environmental challenge for wastewater treatment plants (WWTPs) in the Gaza Strip. This study aims to evaluate the impact of OMW discharge on the operational efficiency of WWTPs, particularly during the olive harvesting season. To achieve this, samples were collected from both olive mills and WWTPs across the region and analyzed for key parameters such as chemical oxygen demand (COD), biological oxygen demand (BOD5), phenols, oil and grease, and total suspended solids (TSS). The study also calculated the total pollutant load generated by the olive oil production process. The results revealed that olive oil production in the Gaza Strip generates substantial amounts of pollutants, including 3374.76 tons of COD, 797.55 tons of BOD5, 1.33 tons of phenols, 184.42 tons of oil and grease, and 1204.99 tons of TSS. During the olive harvesting season, influent pollutant levels at the Gaza Central WWTP spiked to 3040 mg/L for COD, 1382 mg/L for BOD5, and 1810 mg/L for TSS, which exceeded the plant's design capacity. In contrast, the North Gaza WWTP, which serves fewer olive mills, recorded lower pollutant values of 760 mg/L for BOD5 and 933 mg/L for TSS. These findings underscore the significant seasonal impact of OMW on the WWTPs, highlighting the need for improved management strategies to mitigate the environmental and operational challenges associated with OMW disposal.