• Journal of the Korea Organic Resources Recycling Association
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• v.11 no.2
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• pp.66-73
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• 2003

To investigate the availability of solidified wastes as resource, wastewater sludge, waste gypsum and fly ash were mixed and the results with various mixing ratios are as follows. Compressive strength turned out to be increasing as the amount of waste gypsum increases, keeps longer curing inhibition, and higher forming Pressure under the conditions of waste gypsum/sludge ratio 0.31-0.45, and 0.9kg cement as 15% and 1.2kg cement as 20% of total amount. Solidified agent under the fly ash/sludge ratio 0.45, 0.6, compressive strength seemed to be higher than standard one which means solidified wastes with these conditions could be applicable in real life. These results inform that concentrations of the leachate $Cr^{+6}$, Cu, Zn, Cd, Pb solidified matrix, containing low concentration of heavy metal, were cured with/without enough time it still will cause adverse effect on nature environment and application of heavy metal sequester must be needed to reuse industrial wastes from incineration plant solidified matrix. Total cost price, when considering manufacturing capability of the facilities for resourcerizing as 18,000ton was presented 678,664,000 won, as it were, manufacturing cost price was 37,704 won per ton. The results as above has shown that it's possible to use the mixture of waste gypsum/sludge, fly ash/sludge, cement, additions, and solidification matter as substitute of materials like brick, block, interlocking which has proper compressive strength of KS L 5201 and KS F 4004.

• Journal of environmental and Sanitary engineering
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• v.8 no.2
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• pp.65-84
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• 1993

This study reviewed the current status and problems of sewerage system in Korea and then proposed possible methods to correct the problems. Also, evaluation of future development in sewerage system is included. It can be summarized as follows : 1. Investment in sewerage system is relatively low . 0.23% of GNP, Considering that the investment portion is 0.35% in OECD and 0.63% in Japan, it should be increased further. 2. The reasons wily the investment in sewerage system is low can be ' (1) Low priority is given to the investment in sewerage system. Local government builds and operates its own wastewater treatment plant. Local government as well as residents prefer to invest their money in roadwork, housing and parks to in wastewater treatment facilities because of greater investment effects. (2) Besides capital investment, more maintenance cost is needed for sewerage system. Proper operation of wastewater treatment facilities requires a well-trained operator. Because of public conception that operation of wastewater treatment facility is a dirty job, it is difficult to find a well-trained operator. (3) It is difficult to estimate the effect of sewerage system (4) Cost required to build and maintain wastewater treatment facility should be paid by people, who benefit from the facility. People to benefit are sometimes different from people to pay. 3. Advanced treatment is necessary to protect the bay aura and raw water source as well as to prevent eutrophication of lakes and ponds. 4. Wastewater treatment facility were mainly build in big cities during the decade of 1980. Followings should be solved first to expand the facilities. (1) Rapid repair and construction of sewer. (2) Technical development of wastewater treatment . Prevention of efficient and economical wastewater . Development of efficient and economical wastewater treatment techniques . Development of high-efficiency treatment using bioreactor . Reuse of wastewater treatment plant effluent (3) Sludge treatment and disposal . Composting of sludge cakes . Development of techniques to reduce the volume of sludge cake : incineration and reuse of sludge ash and slag. (4) Utilization of wastewater treatment facilities . Construction of community parks or sports families(ie, on the tops of the covered aeration tanks and sedimention tanks) Construction of wastewater treatment facilities under ground and of parking facilities and community parks above ground. (5) Education of wastewater treatment personal.