Search

The biotransformation of octylphenol polyethoxylate surfactant (Triton X-100) and bacterial communities in soil microcosms was investigated. The soil microcosms were designed to simulate real sites of bioremediation. The soil used in this study was contaminated with pesticides and alkylphenol polyethoxylate surfactants over a long period of time. The nitrogen source, (NH4)2SO4 and the mineral salt basal solution were added to the microcosm and the water content was adjusted to 50% with distilled water. The microcosms were aerated using an aeration system with an air flow rate of 0.3 l min(-1). The exogenous bacterial strain Pseudomonas sp. SH4 was added to the microcosms to increase the rate of biotransformation of the Triton X-100. The number of microorganisms and the theoretical extent of formation of carbon dioxide were estimated to evaluate the biotransformation of Triton X-100 in the microcosms. The analytical results revealed that the exogenous bacteria could increase the rate of transformation of Triton X-100 by approximately 50%. Aeration of the microcosm increased the biotransformation of Triton X-100 by 45%. Bacterial count of 6.8x10(10) MPN g(-1) of soil was achieved in the M5 microcosm. Analysis of the bacterial community by 16S rDNA sequences revealed that Pseudomonas sp. SH4 could dominate all the microcosms to which it was added as an exogenous bacteria. The quantity of the indigenous bacterial strains Stenotrophomonas maltophilia, Stenotrophomonas sp. and clone 4-70 were also enhanced in the microcosms by the aeration, and the addition of carbon and nitrogen source.

A novel fibrous-bed trickling filter was developed to remove toluene present in contaminated air. Pure culture of Pseudomonas putida F1 was attached on fibrous-bed and utilized toluene as the carbon source. Experimental results indicated the removal efficiency decreased with the increase of inlet concentration. In general, the removal efficiency of toluene was greater than 90% when the inlet loading capacity was below 70 g m-3h-3. The elimination capacity increased with increasing inlet loading capacity, but the increased rate decreased gradually. When the inlet loading capacity increased to 300 g m-3h-1, the elimination capacity could approach to 130 g m-3h-1. The first order kinetics model was useful to describe the removal of toluene in this filter and an excellent linear relationship was found between the apparent first order parameter and inlet concentration (ranging from 1.2 g m-3 to 3.5 g m-3). Also, the performance of fibrous-bed trickling filter was relatively stable during the four-month period of continuous operation. Slight clogging phenomena of filters were observed only under high loading capacity.

The decolorization and transformation of the anthraquinone dye, Reactive Blue 19 (RB-19), by ozonation with a semi-batch reactor were investigated. The effects of different operating parameters, such as the initial RB-19 concentrations, ozone feed rates and initial pH, on the performance of color, dye and total organic carbon (TOC) removal were also evaluated based on their pseudo-first-order rate constants and removal efficiencies. The experimental results indicated that the removal of color and the dye itself was more rapid and complete than that of TOC in all the ozonation tests. However, increasing the initial RB-19 concentration had a significant effect on decreasing the rate constant of RB-19 reduction. In addition, increasing the ozone feed rate had positive effects on the color, dye and TOC removal, particularly on the TOC diminution. The rate constant and efficiency of color removal were highest at initial acidic pH conditions, but the dye and TOC removal were more effective at initial basic pH values, possibly due to the more powerful and non-selective hydroxyl radical oxidation.

This study examined the factors that influence the reductive dechlorination of trichloroethylene (TCE) when direct current is externally supplied to a laboratory scale iron wall. Experimental results indicated that an anode electrode was placed in contact with the iron filling near the inlet of the column, and then a cathode was located on the top of the column. Excellent TCE degradation efficiency was displayed. The surface of the iron particles was acid-washed by H+, owing to water oxidation around the anode, and large quantities of Fe2+ were produced as a reductant which enhanced the TCE degradation, due to iron corrosion caused by the supply of external electrons. The cathode should be placed in sand fill atop the iron filling in order to avoid the formation of iron (hydr) oxide precipitates on the surface of the iron particles when the pH increases as a result of the release of OH+ around the cathode. Due to more H+ being released, which benefited the acid-washing of the iron filling, the TCE removal efficiency increased from 32% to 100% when the electric potential increased to 60V. However, black precipitates of iron (hydr) oxide were observed coated on the iron surface, causing the blocking of pores in the iron wall with the increase in the electric potential application. The efficiency of TCE degradation was almost equal regardless of groundwater velocity when direct current was applied to the iron wall. Based on observations of TCE degradation during long-term operations, the TCE removal efficiency in the effluent reached 100% after seven days of operation and maintained this high level after 25 days of operation. Thus, iron wall by electroremediation displayed excellent potential for development in long-term operations.