This study aimed to investigate the feasibility of improving dewaterability and settleability of sewage sludge using coagulation sludge. When mixed with sewage sludge and coagulation sludge at 1:1 ratio, capillary suction time(CST) and specific resistance to filtration(SRF) decreased by about 56% and 68%, respectively. It is found that total solids(TS) and volatile solids(VS) of mixing sludge are increased by about 59% and 53%, respectively. Also, the turbidity of the mixing sludge supernatant was reduced from 99 to 16 NTU. It is observed that the mixing of sewage sludge and coagulation sludge at 1:1 showed better effect than using poly-aluminum chloride(PAC) coagulant at 25 mg/L.

Oxidized PAN (OXI-PAN) fibers were used for the precursors of activated carbon fiber in study. How drying temperature affected the properties of carbon fibers on activating process of carbon fibers was investigated. The specific surface areas of activated carbon fibers have been determined on a series of chemically activated carbons with KOH and NaOH. The experimental data showed variations in specific surface area, iodine and silver adsorptions by the activated carbon fibers. The amount of iodine adsorption increases with increasing specific surface areas in both activation methods. This was because the ionic radius of iodine was smaller than the interior micropore size of activated carbon fibers. Silver adsorbed well in NaOH activated carbon fibers rather than KOH activated carbon fibers in this study.

Recycling of incineration ash generated from domestic waste incinerators is important from environmental and energy conversation aspects. The main components of bottom ash are CaO, Al2O3, SiO2, P2O5, MgO, and Fe2O3, similar to geological components. However, it also contains heavy metal ions such as Cu2+, Pb2+, and Cr6+. The ash material was sintered at 1100 ~ 1150oC by adding pink kaolin to stabilize those heavy metals. The study analyzed the crystal phase and absorption rates of the sintered material for application as a sub-base layer material for roads and conducted tests for the requirements for sub-base layer materials for roads, such as CBR test, quantity of abrasion, and liquid limit. Considering the plasticity, water absorption, and compressive strength of the road base, the mixture with 76wt% bottom ash and 24wt% pink kaolin after sintering at 1,120oC, showed CBR test result of 33.0, quantity of abrasion of 30.3, and liquid limit of NP (no plasticity). These result indicated the possibility of using bottom ash as a sub-base layer material, which satisfied requirements of the standard specification for road construction.

The components of municipal solid waste incineration bottom ash produced over 3 million ton every year are similarto the components of geological features, therefore it is suitable to be used as the raw materials of lightweight aggregate.Development of lightweight aggregate using this bottom ash will be helpful to solve landfill and environmental problems.Lightweight aggregate was developed at 1,110oC by using clay, kaolin, bentonite and silica as the raw material to 50%of municipal solid waste incineration bottom ash. Silicon carbide (SiC) was used as a blowing agent. Optimal mixingratio is bottom ash 50%, kaolin 22%, clay 22%, bentonite 6% and blowing agent 0.1%. As the result of quality test,produced lightweight aggregate met the all appraisal standards. The result of heavy metal leaching test was much lowerthan the elution reference value of ceramic manufactures made by using bottom ash.

Ceramic welding backing material is a mullite-cordierite composite that is currently being used for welding processes in plant and shipbuilding. It is the optimal material for welding processes thanks to its extremely low thermal expansion coefficient and strong resilience against high temperature. However, due to the pollutants from welding such as iron and carbon, the entire amount of ceramic welding backing material is being land-filled after a single-time use. In this study, ceramic welding backing material was mixed with clay and kaolin to be used as a new ceramic body. A composition with 20 ~ 50% of ceramic welding backing material showed sufficient plasticity, and when fired at 1,250oC, it was deemed available for ceramic block and others with the porosity of 2.27 ~ 5.94%, water absorption ratio of 0.99 ~ 3.96% and bending strength of 720 ~ 810 kgf/cm2. In addition, color ceramic body, which was made from a waste welding backing material, of which iron was partially removed, added with 3wt% of high temperature pigment and fired at 1,250oC, displayed the unique color of the pigment, meaning that waste welding backing material could be used for ceramic bodies of a variety of colors.

Recycling the bottom ash from MSWI (Municipal solid waste incinerators) ash is required to reduce the secondary pollution. We characterized the bottom ash and investigated the possibility of application for subsidiary ceramic raw materials. Major components of bottom ash are analyzed as CaO, Al2O3, SiO2, P2O5, MgO, Fe2O3, which are the same components of the earth’s crust. This similarity of components implied that bottom ash could be recycled as ceramic products through systematic treatment. Considering the plasticity and water absorption results, the ceramics, which are the mixture with 74 wt % bottom ash and 26 wt% Pink Kaolin, showed 1.39% water absorption after sintering 1150oC for 1h. This result indicated the possibility of recycling of bottom ash for subsidiary ceramic raw materials.

Recycling of bottom ash which is the part of the non-combustible residues of waste combustion is very important for saving energy and resource recycling. In this research, we tried to develop recycling method for the bottom ash as the roadbase, the layer of aggregates under the paved layer of a road. We first removed ferrous and non-ferrous metals from the bottom ash with a 20 mm mesh strainer. After grinding ceramics and glass using jaw crusher, we mixed them with the bottom ash, and then they were further finely grounded up to the particle size less than 150 mm with ball mill. XRD analysis of the final ground material showed that the main ingredients were CaO, SiO2, Al2O3, P2O5, Fe2O3 and MgO. Also there were some heavy metals such as Cu2+, Pb2+ and Cr6+ in it. To make roadbase out of the processed bottom ash, we mixed it with purified sludge, pink kaolin (from Hadong, Gyeongnam, Korea), and silica sludge, and fired in an electric kiln at 1150 ~ 1200oC. Finally, the usefulness of the roadbase made of bottom ash was analyzed by testing absorption rate, crystallizing and strength as well as indoor California Bearing Ration (CBR) test, abrasion test, sand reduction test. The developed material from recycling the wasted bottom ash satisfied the requirement of roadbase properties.