Characterization and fenton treatment of hazardous organic substances in Para rubber industrial wastewater in Southern Thailand
Worawit Wongniramaikul
This study focuses on the characterization and treatment of the hazardous organic substances in rubber latex (Hevea brasiliensis) wastewater. In the characterization part, the organic substances in wastewater were extracted by liquid-liquid extraction (LLE) and solid-phase extraction (SPE) their separation and identification by size exclusion chromatography (SEC) and GC-MS, respectively. The variations of the raw and treated wastewater quality were monitored for 6 months, covering the cropping and leave shedding season. According to the monitoring results, there are 7 organic groups contained in the raw wastewater such as acids, indoles, phthalates, alcohols and phenols, thiazoles, thiocarbamates and the others. Two dominant species in the raw wastewater were 3-methylindole (3MI) and diisobutyl phthalate (DIBP). The first compound, 3MI, belongs to the category of bad smelling property, while the second is recalcitrant to biodegrade. Both cause the problems the para rubber industry suffers frequently, including the malodor and the effluent COD exceeding the standard value. Because of this, Fenton's treatment was proposed in this study. The synthetic wastewater of each compound was prepared and treated by Fenton's reagent. The optimum operating conditions were determined. The results show that the optimal molar ratio of [H[subscript 2]O[subscript 2]]:[Fe[superscript 2+]]:[DIBP or 3MI] is 5:5:1 for DIBP, and 1:1.5:1 for 3MI, given the pH of 3. With such information available, the optimum conditions were applied to the industrial wastewater, and the results of which were compared with those of the synthetic wastewater. According to the experimental results, there were significant differences in %degradation between the synthetic and the real wastewater. Consequently, the operating condition of both industrial raw and treated wastewater were re-optimized. The results show that the optimum condition for the raw wastewater was 20:10:1 for 3MI at pH 3, while the optimum values for treated wastewater were 617 mg H[subscript 2]O[subscript 2] L[superscript -1] and 70 mg Fe[superscript 2+] L[superscript -1] at pH 3. Under these conditions, the 3MI in the raw wastewater could be removed nearly 100% in 180 min, and the biodegradability index was increased by 0.1, approximately. Therefore, the Fenton's oxidation is recommended as pretreatment system for the subsequent industrial biological treatment. The DIBP and COD in the treated wastewater could be removed by 90% and 48%, respectively under the optimum condition. These are enough to meet the discharge. In addition, the empirical kinetic equations with respect to Fenton treatment were also determined for further application.
Performance Assessment of Incinerators and High-Temperature Industrial Processes for Disposing of Hazardous Waste in the United States
ET Oppelt
Since 1982, the U.S. Environmental Protection Agency (EPA) has been conducting performance assessments of hazardous waste thermal destruction facilities in the United States. The principal objective of these tests has been to characterize emissions and determine if these facilities are capable of meeting the waste destruction and control requirements of the current EPA regulations and standards. To date, the test program has involved performance assessments at 9 incinerators and over 20 high-temperature industrial processes employing hazardous waste as a fuel supplement in their operations. The testing has typically involved stack emissions assessment for SOx, NOx, particulate, hydrochloric acid (HCl), carbon monoxide (CO), carbon dioxide (CO2), oxygen (O2), metals, total hydrocarbon, and quantification of specific organic compound emissions. Engineering and other process operating variables (for example, excess air, steam load, and waste to fuel ratio) have also been recorded during the test program in order to examine the potential operating bounds for these facilities. The purpose of this paper is to summarize the extensive results of this testing program, which has, in general, indicated that high organic compound destruction and removal efficiencies (99.99%) are achievable in these facilities. Effective (99%) control of HCl emissions was attained in facilities handling chlorinated organic wastes. The current EPA particulate standard of 180-mg/dry m3 was the most difficult standard to attain for incinerators.