A novel hybrid system composed of a biotrickling filter and an activated sludge reactor was investigated under the conditions of four different SRTs (sludge retention times). The performance of the hybrid reactor was found to be directly comparable among the four different sludge ages. Discernible differences in the removal performance were observed among four different SRTs of 2, 4, 6, and 8 days. High removal efficiency was achieved by continuous circulation of activated sludge over the immobilized mixture culture, which allowed on pH control, addition of nutrients, and removal of paint VOCs (volatile organic compounds). The results also showed that the removal efficiency for a given pollutant depends on the activity of microorganisms based on the SRT. As the SRT increased gradually from 2 to 8 days, the average removal performance decreased. The highest removal rate was achieved at the SRT of 2 days at which the highest OUR (oxygen uptake rate), $6.1mg-O_2/liter-min$ was measured. Biological activity in the recycle microbes decreased to a much lower level, $3.6mg-O_2/liter-min$ at a SRT of 8 days. It is thus believed that young microorganisms were more active and more efficient for the VOCs removal of low concentrations and high flow rates. The apparent correlation of $R^2=0.996$ between the average removal efficiency and the average OUR at each SRTs suggests that VOCs degradation by young cells significantly affected the overall removal efficiency for the tested SRTs.

A long-path transmissometer is one of the optical instruments widely used to measure atmospheric light extinction coefficient without enclosing a light beam and perturbing aerosols. Over the past two decades, a number of measurements have been carried out using the long-path transmissometer manufactured by OPTEC, Inc. Calibration of the transmissometer should be performed when any component of the transmissometer system is interchanged or installation condition is changed. For a better calibration of the transmissometer, application of a modified calibration method for the existing neutral density (ND)-filter method was recommended for the computation of the atmospheric transmittance using model MODTRAN 4 in this study. It was revealed that the measured light extinction coefficient from the transmissometer which was calibrated using the existing ND-filter method could be overestimated due to the assumption of the atmospheric transmittance suggested by OPTEC, Inc. The uncertainty of the measured light extinction coefficient from the transmissometer calibrated based on the modified ND-filter method was calculated to be approximately $13Mm^{-1}$.

An experimental study was performed on the decomposition of gaseous ammonia and two selected volatile organic compounds (VOCs: toluene and acetone) in a combined nonthermal plasma reactor with corona and glow discharges. A lab pilot scale reactor (206 liter) equipped with a high electric power pack was used to determine the decomposition efficiency in relation with the inlet concentration and applied voltage. Three different types of discharging electrode such as wired rack, wire strings for corona discharge, and thin plate for glow discharge were put in order in the reactor. While decomposition of ammonia decreased with an increase in the initial concentration, acetone showed an opposite result. In the case of toluene however no explicit tendency was found in toluene and aceton. Negative discharge resulted in high decomposition efficiency than the positive one for all gases. A better removal of gas phase element could be achieved when fume dust were present simultaneously.

Domestic anthracite contains a large amount of fine particles, which causes to fire the back side of the boiler and to form the clinker deteriorating the combustion efficiency. At this time, the fine limestone adsorbents for a desulphurization agent may be used to facilitate an aggravation of the boiler, so that fine mode of limestone (<0.1mm) has been used no more than $25\%$ in local power stations of Korea. The present test carried out with an in-situ boiler, however, showed that higher content $(up\;to\;50\%)$ of fine limestone particles did not entail any mal-function. In addition, the desulphurization was found to be as good as the old mode of limestone adsorbents.