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The objective of this work is to produce solid biofuel from sawdust using the HTC (Hydrothermal carbonization) process. The HTC process of feedstock involves the raw material coming into contact with high temperature and pressurized water. The HTC process could produce gaseous, liquefied and solid products, but this study focused on solid product only as an alternative to coal. In this study, sawdust used for a feedstock and its moisture content was under 5%. Water was added with the feedstock to raise moisture content to 80% and also used catalysts. The HTC process was performed at temperature range from 200 to 270℃ and reaction time was 15 to 120 min. Rising temperature resulted in increasing the higher heating value (HHV) of HTC product. In case of adding catalyst, HHV of solid biofuel was higher and reaction occurred at lower temperature and pressure. Also, HTC solid product had been characterized and found to be hydrophobic, increased HHV (over 40%), and pelletized easily compared to raw material.

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A B S T R A C TThis study aims to examine the treatment of graywater (GW), especially bathroom wastewater, using subsurface-flow constructed wetlands (CWs) in an apartment complex. It analyzed the removal of organic matters and nitrogen, the status of a wetland by depth, and microbial communities under the conditions of aeration and non-aeration at the inlet section, and planting and non-planting. The results of this study show that aeration at the inlet section and planting affect ORP, SO 2À 4 , and nitrogen by water flowing distance and water depth in a wetland. The result of COD cr removal seems to satisfy the Korean standard (below 20 mg/L (COD mn )) of reuse water quality in all three operational conditions. The aeration at the inlet section has the advantages of effectively removing organic matters at the inlet section, thus preventing its clogging, and removing nitrogen through the nitrification. Aeration at the inlet section and planting are expected to have a positive effect on the wetland status and GW treatment. Therefore, aeration at the inlet and planting will be helpful to construct and operate an artificial wetland in residential areas such as a multi-family housing complex. Ammonia-oxidizing bacteria including Nitrosomonas, Nitrosospira, Nitrosococcus and denitrifying or nitratereducing bacteria such as Thiobacillus, Achromobacter, Pseudomonas, Micrococcus belong to the classes of β-proteobacteria, γ-proteobacteria, and Actinobacteria. These microbial communities found in this study seem to contribute to nitrogen removal. But, the roles of microbial community in CWs need to be further investigated, both qualitatively and quantitatively.