Occurrence, removal and health risk assessment of phthalate esters in the process streams of two different wastewater treatment plants in Lagos and Ogun States, Nigeria.

Abstract

Phthalate esters (PEs) are one of the environmentally active organic pollutants capable of causing endocrine disruption. The levels of PE congeners were determined in the influent and effluent from Covenant Oxidation Pond (COP) and Ikeja Wastewater Treatment Plant (IWWTP). Standard methods were adopted for determining the physical and chemical parameters of the water samples. The water samples for PE congener's determination were collected, acidified and stored at 4°C prior to liquid-liquid extraction and analysis by gas chromatograph. The possible health risk associated with the usage of effluent-polluted river water was also investigated. The pH and temperature ranges were within the Federal Ministry of Environment (FME) 2001 guideline limits while the dissolved oxygen, biochemical oxygen demand and chemical oxygen demand were above the limits. The IWWTP performed better at removing PEs at 54% compared to 43.3% on average at COP. The health risk of individual PE congener showed no non-cancer effects (HQ) as the values varied from 5.01E-05 (DAP) to 1.52E-02 (DEHP) for adults and 1.17E-04 (DAP) to 3.76E-03 (DBP) for children at COP, while at IWWTP, it ranged from 8.06E-05 (DIBP) to 1.09E-02 (DEHP) for adults and 5.68E-04 (MMP) to 2.54E-02 (DEHP) for children. Notwithstanding, the usage of effluent-polluted river water by local communities downstream may result in carcinogenic effects due to the cumulative effects of the PE congeners as the values obtained for adults and children for the ingestion and dermal routes for the two waste process streams ranged from 4.67E-06 (IWWTP) to 6.22E-05 (IWWTP) and 2.18E-05 (IWWTP) to 7.18E-05 (COP), respectively.