Abstract
This study investigated the concentrations and congener profiles of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in intake source water (source water) and tap drinking water (tap water) of drinking water treatment plants (DWTPs). In order to have a better understanding on the influence of atmospheric PCDD/F deposition on drinking water, PCDD/Fs in the ambient air of a DWTP (DWTP-LN) were measured and both dry and wet deposition on the water treatment facilities were assessed. The results of this study indicated that the mean PCDD/F concentration in tap water (0.0039 pg WHO-TEQ/L) was found to be approximately 55% of magnitude less than that in source water (0.0086 pg WHO-TEQ/L). In addition, the total deposition flux (dry + wet) of PCDD/Fs entering the DWTP-LN was 27.0 ng I-TEQ/m 2 -year, and wet and dry deposition contributed approximately 12.0% and 88%, respectively. It reveals that dry deposition is more important than wet deposition of PCDD/Fs in the ambient air of DWTP-LN. Atmospheric deposition of PCDD/Fs will increase the level in source water of DWTP-LN up to 8.91 × 10 -3 pg I-TEQ/L, which is approximately 92% of the PCDD/Fs in source water. If a removal efficiency of 87% is achieved by conventional treatment processes including coagulation, flocculation, sedimentation and rapid sand filtration, the water after treatment may increase 1.16 × 10 –3 pg I-TEQ/L, which is approximately 43% of the concentration level in tap water. These results indicate that in the DWTP-LN, the influence of atmospheric deposition of PCDD/Fs on the drinking water is of great significance, and water treatment facility with a cover is suggested.
Highlights
Due to the potential adverse health effects from exposure to polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), such as reproductive difficulties and increased risk of cancer (US EPA, 2003), their presence in the environment is of great concern
The total deposition flux of PCDD/Fs entering the drinking water treatment plants (DWTPs)-LN was 27.0 ng I-TEQ/m2-year, and wet and dry deposition contributed approximately 12.0% and 88%, respectively. It reveals that dry deposition is more important than wet deposition of PCDD/Fs in the ambient air of DWTP-LN
These results indicate that in the DWTP-LN, the influence of atmospheric deposition of PCDD/Fs on the drinking water is of great significance, and water treatment facility with a cover is suggested
Summary
Due to the potential adverse health effects from exposure to polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), such as reproductive difficulties and increased risk of cancer (US EPA, 2003), their presence in the environment is of great concern. How PCDD/Fs enter tap water through deposition has seldom been investigated, a deficiency this study aims to address. In Taiwan, there were several studies regarding the atmospheric PCDD/F deposition from relevant sources. Shih et al (2006) investigated dry deposition of PCDD/Fs in the ambient air in southern Taiwan. Atmospheric dry deposition fluxes of total PCDD/Fs averaged approximately 150 pg/m2/day. The total dry deposition flux was found to decrease as the temperature increased. Calculated dry deposition velocities of total PCDD/Fs were averaged 0.42 cm/s. Atmospheric dry deposition of PCDD/Fs in the vicinity of municipal solid waste incinerators was investigated by Wu et al (2009). Asian dust storm (ADS) that originated in the deserts of Mongolia and Mainland China eventually reached Taiwan, and significantly increased the atmospheric PCDD/F concentrations. The amount of PCDD/Fs bound to suspended particles increased during the ADS episode (Chi et al, 2008)
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