Determination of volatile organic compounds in ambient air by using thermal desorber, sorbent tubes, canister and GC-MS
Mkhwanazi, Sipho Sydney
The dissertation deals with volatile organic compounds that evaporate from the water-oil separate in the refinery, which causes bad odour around the neighbouring communities, the existence of these compounds are being identified and quantified in different seasons for the year. VOC are emitted whenever wastewater is exposed to the atmosphere. As such, emission points include open drains ditches, manhole sewer outfalls and surface fore bays, separators and treatment ponds. Refinery units such as reactors, fractionators are periodically shutdown and emptied for internal inspection and maintenance. The amount of VOC entering the wastewater is not monitored. The effluent water discharged from the refinery is not checked for the amount ofVOC present. The monitoring of the amount of VOC in wastewater stream may lead to a decrease in the emission. From the quantified results at different season, the summer session has the highest VOC emission due to the heat that causes more vapours. The preparation of a method for determination of VOC's in air presents many difficulties, because of their high volatilities and low concentrations in air. As well, the results of determination are affected by the properties of the sorbent used, mainly its sorption capacity, depending on the properties of the compound under determination. The methods for sampling and analytical procedures for the measurements of volatile organic compounds that are hazardous to air pollution are compendium method T0-14 and sorbent tube method compendium T0-17. Both methods (sorbent tube and canister) differ from each other in their extraction and detection techniques. The well suitable method for the VOC determination is canister method; this method gives more representative sample of the ambient monitoring of 24 hours, where as sorbent tube can do for 2 hours only. The canister method is more advantages due to the sample that will be still remaining for further analyses or re-check. The integrity of API water-oil separator has been improved to cause less evaporation during high temperature season. As the temperature drops from season to season, the VOC also comes down as its being seen in this study that on the winter results that all the VOC were below 90 1-lg/kg.
M. Tech. (Chemistry, Department of Chemistry, Faculty of Applied and Computer Science), Vaal University of Technology
Volatile organic compounds, Waste water