Abstract
The loading and removal efficiency of 16 US EPA polycyclic aromatic hydrocarbons (PAHs) were examined in an inverted A2/O wastewater treatment plant (WWTP) located in an urban area in China. The total PAH concentrations were 554.3 to 723.2 ng/L in the influent and 189.6 to 262.7 ng/L in the effluent. The removal efficiencies of ∑PAHs in the dissolved phase ranged from 63 to 69%, with the highest observed in naphthalene (80% removal). Concentration and distribution of PAHs revealed that the higher molecular weight PAHs became more concentrated with treatment in both the dissolved phase and the dewatered sludge. The sharpest reduction was observed during the pretreatment and the biological phase. Noncarcinogenic risk, carcinogenic risk, and total health risk of PAHs found in the effluent and sewage sludge were also assessed. The effluent BaP toxic equivalent quantities (TEQBaP) were above, or far above, standards in countries. The potential toxicities of PAHs in sewage effluent were approximately 10 to 15 times higher than the acceptable risk level in China. The health risk associated with the sewage sludge also exceeded international recommended levels and was mainly contributed from seven carcinogenic PAHs. Given that WWTP effluent is a major PAH contributor to surface water bodies in China and better reduction efficiencies are achievable, the present study highlights the possibility of utilizing WWTPs for restoring water quality in riverine and coastal regions heavily impacted by PAHs contamination.
Highlights
Polycyclic Aromatic Hydrocarbons (PAHs) are a wide spread class of environmental pollutants of concern [1] due to their carcinogenicity, mutability and toxicity [2]
The partitioning behavior of PAHs is well understood [11], it is expected that the low molecular weight (LMW) PAHs are mainly in dissolved form whereas the high molecular weight (HMW) PAHs are predominantly bound to organic-rich surfaces or solids
PAHs concentrations (Table 1) in raw sewage are generally consistent throughout the study, as the level differences across the four sampling dates are small
Summary
Polycyclic Aromatic Hydrocarbons (PAHs) are a wide spread class of environmental pollutants of concern [1] due to their carcinogenicity, mutability and toxicity [2]. They originate primarily from incomplete combustion and petroleum spill [3] and are prone to bioaccumulation and biomagnification [4] as well as long-distance transport [5]. PAH concentration limits have been set by many countries, such as EU [7], US EPA [8], Netherlands [9] and China [10] Following their release from fuel spillage or atmospheric deposition, PAHs can enter the sewage system through domestic wastewater, industrial discharge, or surface runoff via the urban drainage. The partitioning behavior of PAHs is well understood [11], it is expected that the low molecular weight (LMW) PAHs are mainly in dissolved form whereas the high molecular weight (HMW) PAHs are predominantly bound to organic-rich surfaces or solids
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