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Development and validation of novel extraction techniques for the determination of total and bioavailable polycyclic aromatic hydrocarbons (PAHS) in wastewater and wastewater sludge
Expanded Title:Polycyclic aromatic hydrocarbons (PAHs) belong to an important class of persistent organic pollutants commonly found at low concentrations in the environment. The sources of these compounds include entirely anthropogenic activities such as chemical industries, combustion and agricultural activities. Owing to their potential carcinogenicity, mutagenicity and teratogenicity, it is important to determine PAHs in several matrices, which include complex matrices such as waste water and waste water sludge. To date, very few local and international studies have examined the detailed presence and distribution of these compounds within environmental compartments such as waste water sludge. Although official methods approved by international bodies such as the United States Environmental Protection Agency are able to extract PAHs in waste water sludge, all of them involve two separate steps. The steps generally include extracting the target compounds along with other unwanted compounds followed by a cleaning step before analysis. The two-step approach increases the errors in measurements and its time-consuming. Further, these methods extract the total fraction of compounds in the sludge and not just the bioavailable fraction. In the context of the environmental impact of these compounds, especially when sludge contaminated with PAHs is used as an organic fertiliser, it is the bioavailable fraction that matters and not the total amount in the sludge. Therefore, the primary goal of this study was to develop, optimise and validate novel extraction techniques for to selectively extract PAHs from waste water and waste water sludge. The novelty of these techniques is that they combine two or three extraction steps into a single step, thereby minimising errors and sample turnaround time. Further, one of the techniques measures the bioavailable fraction while the other technique measures the total concentration, thus offering needed complimentary results. The first part of the work involved synthesising and characterising molecularly imprinted polymers (MIPs) that would enhance the specificity of the PAH extraction. Key in the synthesis was choosing the appropriate template that could selectively bind all 16 United States Environmental Protection Agency (US EPA) priority PAHs. The synthesised and characterised imprinted and non-imprinted polymers were found to have surface areas of 386.6 m2∙g−1 and 360 m2∙g−1 respectively. The high surface area of imprinted polymers is attributed to cavities from the imprinting process. The different PAHs consisting of low molecular weight (two and three rings), medium molecular weight (four rings) and high molecular weight (five and six rings) were investigated. The MIPs imprinted with medium molecular weight PAHs preferred high molecular weight PAHs. On the other hand, high molecular weight PAHs imprinted polymers performed better than all prepared polymers, and were selected for further investigations in this study.
Date Published:01/03/2018
Document Type:Research Report
Document Subjects:Wastewater Management - Sludge management
Document Format:Report
Document File Type:pdf
Research Report Type:Standard
WRC Report No:7025/1/17
ISBN No:978-1-4312-0894-4
Authors:Ncube S; Tavengwa NT; Cukrowska E; Chimuka L
Project No:K5/7025
Originator:WRC
Organizations:University of the Witwatersrand
Document Size:2 394 KB
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