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To enhance nitrogen removal in an existing microbial contact oxidation (MCO) system with a treatment capacity of 900 m 3 /d, an upflow multilayer bioreactor (UMBR) was chosen as a preanoxic reactor for the removal of organic matter and nitrate. The removal performance of the retrofitted plant was evaluated during the startup phase at a low temperature in winter. The high removal (.80%) of organic matter and suspended solids in the UMBR provided stable nitrification conditions in the MCO system, as a result of the substantial reduction in organic matter and solids loaded onto the MCO system. This treatment system showed a stable nitrogen removal efficiency of 75.3%, even in the low temperature range 7 to 108C. Phosphorus was completely removed by chemical precipitation. Production rates of excess sludge, as a function of the loads of influent flowrate and biological oxygen demand (BOD), were 0.022 kg dry solid/m 3 wastewater and 0.132 kg dry solid/kg BOD. Water Environ. Res., 80, 757 (2008).

The purpose of this research was to quantify the effects of water content (0.3 to 0.75% for sand, and 0.4 to 1.25% for silt-clay) and temperature (4 to 40 °C) on the equilibrium distribution of the priority pollutants, dichloromethane and l,l,l-trichloroethane in dry Korean decomposed granite soil. The values of effective partition coefficient (Kerr) were largely decreased as the water content increased. Organic pollutant partitioning in dry soil is composed of both water saturated site and dry site in sorbent, and dry site which has high partition coefficient, is reduced as the water content increases. As the temperature increased, the Kef f values decreased, and this effect was magnified at lower water contents. The values of Keff were correlated better with the estimated values using proposed model. Therefore, in the analysis of distribution and transport of pollutant in unsaturated soil, the effects of water content and temperature on the partitioning should be considered.

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