Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Civil Engineering

First Advisor's Name

Berrin Tansel

First Advisor's Committee Title

Committee chair

Second Advisor's Name

Hassan Zahedi

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Shonali Laha

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Wallied Orabi

Fourth Advisor's Committee Title

Committee Member

Fifth Advisor's Name

Walter Tang

Fifth Advisor's Committee Title

Committee Member

Keywords

VOC emissions, wastewater, Volatile Organic Compounds, Risk Analisys, Monte Carlo simulation, sewer workers

Date of Defense

11-15-2019

Abstract

Many studies on volatile organic compound (VOC) emissions have focused on treatment plants sewage at various locations throughout the world, but they seldom report VOC emissions derived from sewer networks and sewer transportation systems, as compared to wastewater treatment plants. This study focuses on understanding the occurrence of VOCs produced from sewer networks in municipalities or counties throughout the State of Florida (United States) and identifying potential health risks to sewer workers. Common VOCs were identified in wastewater treatment plant influents using available analytical reports. Gas-phase samples from sewer manholes in the City of Hallandale Beach were collected and analyzed following the U.S. Environmental Protection Agency (USEPA) Method TO-15. The potential adverse health effects of the VOCs, according to their non-carcinogenic and carcinogenic classifications by the USEPA IRIS, were evaluated using risk assessment. Considering the toxicity classification and high concentrations of the identified VOCs, the risk was evaluated for tetrachloroethene, chloroform, 1,4-dichlorobenzene, methylene chloride, and toluene.

The hazard quotient (HQ) gave values less than unity for tetrachloroethene, chloroform, 1,4-dichlorobenzene, toluene, and methylene chloride concentrations from liquid-phase samples from Hallandale and Orlando. This result implies that the non-carcinogenic effects have no health concerns for the sewer workers. On the contrary, the HQ gave values of more than unity value for tetrachloroethylene and chloroform for concentrations measured in the gas-phase samples from Hallandale, which suggested a high probability of health concerns for sewer workers. The calculated HQ for tetrachloroethylene and chloroform for concentrations measured in the gas-phase samples in Hallandale ranged from 0.007 to 13.76 and 0.34 to 2.67, respectively. Based on Monte Carlo simulations, the 95th percentile of the total non-carcinogenic risk for the five VOCs was 31.13, which could pose a threat to human health because it surpasses the acceptable upper confidence limit (1.0).

Carcinogenic risks for tetrachloroethene and chloroform for gas-phase concentrations from Hallandale ranged from 7.12 x 10-8 to 1.43 x 10-4 and 7.88 x 10-5 to 3.74 x 10-4, respectively, which exceeded the acceptable USEPA level of 1.0 x 10-6. Carcinogenic risks for chloroform for concentrations identified in the liquid-phase from Hallandale and Orlando ranged from 7.88 x 10-7 to 5.7 x 10-6 and 9.98 x 10-7 to 7.51 x 10‑6, respectively, which also exceeded the acceptable level. Monte Carlo simulations were used to estimate the carcinogenic risks and to give a better understanding of the variability of exposure in the sewer systems and possible health effects on sewer workers. The 95th percentile of the carcinogenic risks for tetrachloroethene and chloroform from gas-phase concentrations in Hallandale was 1.32 x 10-4 and 4.72 x 10-4, which exceeds the acceptable upper level of 1.0 x 10-6. The 95th percentile of the carcinogenic risks for chloroform from liquid-phase concentrations in Hallandale and Orlando was 9.36 x 10-6 and 9.61 x 10-6, which also exceeds the acceptable upper level. These results suggest that there are possible adverse health effects, such as cancers, for sewer workers.

Identifier

FIDC008872

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