The main objective of the present study was to investigate the efficiency of titanium dioxide (TiO2) assisted photocatalytic degradation (PCD) process for the removal of ammonium-ammonia (NH4(+)-NH3) from the aqueous phase and in the presence of co-pollutants thiosulfate (S2O3(2-)) and p-cresol (C6H4CH3OH) under varying mixed conditions. For the NH4(+)-NH3 only PCD experiments, results showed higher NH4 -NH3 removal at pH 12 compared to pH 7 and 10. For the binary NH4(+)-NH3/S2O3(2-) studies the respective results indicated a significant lowering in NH4(+)-NH3 PCD in the presence of S2O32- at pH 7/12 whereas at pH 10 a marked increase in NH4(+)-NH3 removal transpired. A similar trend was noted for the p-cresol/NH4(+)-NH3 binary system. Comparing findings from the binary (NH4(+)-NH3/S2O3(2-) and p-cresol/NH4(+)-NH3) and tertiary (NH4(+)-NH3/S2O3(2-)/p-cresol) systems, at pH 10, showed fastest NH4(+)-NH3 removal transpiring for the tertiary system as compared to the binary systems, whereas both the binary systems indicated comparable NH4(+)-NH3 removal trends. The respective details have been discussed.
Groundwater is the main source of potable water in many communities. This source is susceptible to pollution by toxic organic compounds resulting from the accidental release of petroleum products. A petroleum product like gasoline is a mixture of many organic compounds that are toxic at different degrees to humans. These various compounds have different characteristics that influence the spread and distribution of plumes of the various dissolved toxins. A compositional model utilizing properties of organics and soil was developed and used to study the concentration of benzene, toluene and xylene (BTX) in leachate from a hypothetical site contaminated by BTX. Modeling indicated the high and variable concentration of contaminants in leachate and its action as a continuous source of groundwater pollution. In a recent study, the status of underground fuel storage tanks in eastern Saudi Arabia and the potential for petroleum leaks was evaluated indicating the high potential for aquifer pollution. As a result of such discussion, it is concluded that more effort should be directed to promote leak prevention through developing proper design regulations and installation guidelines for new and existing service stations.
With the increase in the environmental awareness and reorganization of the need for its protection, the study of soil and groundwater contamination and its remediation have become the focus of numerous researchers. Intentional and unintentional release of hydrocarbon into soil and subsurface pose a great threat to the biosphere environment. The quantification of spilled volume has primary importance for carrying out the remediation work and is considered a first step in the remediation hierarchy. Different investigators approached the problem from many viewpoints, and the resulting achievements are so extensive and scattered that it seems essential to inventory the completed works. This paper presents a systematic study of the available experimental and theoretical works. A complete picture of the present status of the problem is also provided. Issues that remain unresolved and obscure by the current day investigators are pointed out to facilitate future research directions and more comprehensive analyses of the quantification of spilled hydrocarbon volumes.
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