Waste
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Waste Control Technology and Management

A. Summary of activities

The Group has evaluated the waste management methods in Hong Kong with an emphasis on waste minimization and waste recycling. The aims are to look for a more environmentally sound waste management system for Hong Kong while taking the technical, political and economic constraints into account. The Group has also been serving the community through carrying out a number of consultancy projects for Government and the private sector.

B. Representative projects

Chemical stabilization/solidification of hazardous waste

One of the major research areas of the Group is on using cement, pulverized fuel ash and other related materials for the stabilization/solidification of hazardous waste. This includes the study of the long term performance of cement based stabilized/solidified hazardous wastes which aims at developing a leaching model for the prediction of the long-term leaching behavior of chemically stabilized/solidified waste under an acidic leaching environment. The second focus in this research is to study the binding mechanism of waste contaminants in the matrix of the stabilization/solidification agents using microstructure techniques and sequential extraction procedures. This research is carried out in collaboration with Imperial College, University of London and University of Toronto.

Characterization and stabilization of sewage sludge

Chemically assisted primary sedimentation process has been adopted as the treatment process of the Strategic Sewage Disposal Scheme implemented by the Government. In order to better understand the potential risk associated with the disposal of the large amount of sludge, the sludge produced has been characterized with the special purpose of understanding the leaching characteristic of potential pollutants once the sludge is disposed of at landfills. The effect of pulverized fuel ash and lime stabilization on the sludge was also studied by leaching, pot trials and geotechnical testing methods to evaluate the suitability of land application of the sludge. The geotechnical property aspects are carried out in collaboration with the Civil Engineering Department of the Hong Kong University of Science and Technology.

Management of construction and demolition waste

The construction industry generates a large quantity of construction and demolition waste. Based on the experience of two consultancy studies for the Hong Kong Construction Association and the Government's Civil Engineering Department, the research focus of the Group is to devise ways to minimize waste production by studying the feasibility of using certain low waste (environmentally friendly) construction methods and to recycle the waste materials produced by investigating the options available for on-site and off-site sorting. The Group also plans to extend the study to investigate the feasibility of reusing the recycled construction and demolition materials in civil engineering applications.

Managing municipal solid waste in urban China

In urban China, safe disposal of municipal solid waste (MSW) averages less than 2%. Yet the quantity of MSW generation has been growing at 8-10% per annum. The Group's research study aims to find out the MSW composition, recyclable contents, waste generation rates and waste management practices in a few selected cities at different developmental stages in Southern China. The target is to devise a MSW management strategy that conforms to China's sustainable development agenda in the 21^st century. The experience and finding of this research would provide valuable guidance for other Chinese cities.

Waste management in Hong Kong buildings

Traditional building and estate design in HK stressed mainly on the efficient use of space. Public areas (including waste collection areas) are designed to fit the minimum requirement in terms of space consumption. Within individual units, maximising floor areas to conduct economically productive or utility generating activities is again the norm. While maximising space utilisation is likely to continue to be an essential aspect of building design, it should also be balanced with sound resource and waste management which is becoming a very important area in building design. A good building and estate design should be one that allows convenient waste recovery activities. The Group is carrying out a large scale study through the Areas of Strategic Development funding to study (i) the feasibility of adopting different types of waste handling facilities to facilitate better waste management in new buildings; and (ii) the feasibility of retrofitting appropriate facilities for sound waste management in existing buildings.

Construction waste problems on building site

Sorting of in-flight waste from aircraft

Plant grow experiment on stabilized sewage sludge

C. Selected recent output

	Chu, W., So, W. S., Modeling the Two Stages of Surfactant-aided Soil-washing, Water Research, Vol. 35, No. 3, pp182-188, 2001.
	Chu, W., Lead Metal Removal by Recycled Alum Sludge, Water Research, Vol. 33, No. 13, pp3019-3025, 1999.
	Li, X. D., Wai, W. H. O. and Li, Y.S., Coles, B. J., Ramsey, H. and Thornton, I. 2000. Heavy metal distribution in sediments of the Pearl River Estuary, South China. Applied Geochemistry, 15: 567-581.
	Zhang, F.Q., Li, X.D., Wang, C.C. and Shen, Z.G. 2000. Effect of cadmium on autoxidation rate of tissue and inducing accumulation of free proline in seedling of Mung Bean. Journal of Plant Nutrition, 23: 357-368.
	Li, X.D., Shen, Z.G., Wai, W. H. O. and Li, Y.S. 2000. Chemical partitioning of heavy metal contaminants in sediments of the Pearl River Estuary. Chemical Speciation and Bioavailability,12, 17-25.
	Shen, Z.G., Li, X.D. and Chen, H.M. 2000. Comparison of elemental composition and solubility in hyperaccumulator Thlaspi caerulescens with the non-hyperaccumulator Thlaspi ochroleucum. Bulletin of Environmental Contamination and Toxicology, 65, 343-350.
	Chen, J.S., Wang, F.Y. Li X.D., Song, J.J. 2000. Geographical variations of trace elements in sediments of the major rivers in eastern China. Environmental Geology, 39, 1334-1340.
	Li, X.D., Shen, Z.G., Wai, W. H. O. and Li, Y.S. 2001. Chemical forms of Pb, Zn and Cu in the sediment profiles of the Pearl River Estuary. Marine Pollution Bulletin, 42, 215-223.
	Li, X.D., Poon, C.S., Sun, H., Lo, M.C. and Kirk, D. 2001. The study of binding mechanism of metal contaminants in cement based chemical stabilised waste materials. Journal of Hazardous Materials, A82, 215-230.
	Li, X.D., Poon, C.S. and Liu, P.S. 2001. Concentration and chemical partitioning of road dusts and urban soils in Hong Kong. Applied Geochemistry (in press).
	Li X.D. and Thornton, I. 2001. Chemical partitioning of trace and major elements in soils contaminated by mining and smelting activities. Applied Geochemistry (in press).
	Li, X.D., Mai, B.X., Zhang, G., Sheng, G.Y., Fu, J.M., Wai, O.W.H., Li, Y.S. 2001. The distribution of organochlorine pesticides in a sediment profile of the Pearl River Estuary. Bulletin of Environmental Contamination and Toxicology (in press).
	C.S Poon and Z.Q. Chen (1999), "Comparison of the Characteristics of Flow-through and Flow-around Leaching Tests of Solidified Heavy Metal Wastes" Chemosphere, Vol. 38, No. 3, pp. 663-680.
	C.S. Poon, Q. Huang and P.C. Fung (1998), "Degradation Kinetics of Cuprophenyl Yellow RL by UV/H2O2/US Process in Aqueous Solution", Chemosphere Vol. 38, No. 5, pp. 1005-1014.
	C.S. Poon and C.W Chu (1999), "The Use of Ferric Chloride and Anionic Polymer in the Chemically Assisted Primary Sedimentation Process", Chemosphere, Vol. 39(10), pp. 1773-1582.
	C.S. Poon, Z.Q. Chen and O. Wai (1999) , "A Flow-through Leaching Model for Monolithic Chemically Stabilised/Solidified Hazardous Waste", Journal of the Air and Waste Management Association,. Vol. 49, pp. 569-575 .
	C.S. Poon and C.W. Chu (1999), "Planting Grass on Stabilized Chemically Assisted Precipitated Sewage Sludge", J. Toxicological and Environmental Chemistry, Vol 72 pp. 159-170.
	C.W. Chu and C.S. Poon (1999), "The Feasibility of Planting on Stabilized Sludge-Amended Soil" Environment International, Vol 25(4), pp.465-477.
	C.S. Poon, Z.Q. Chen and O. Wai, (2001) "The effect of flow-through leaching on the diffusivity of heavy metals in stabilized/solidified wastes", J. Hazardous Materials, Vol. B81, pp. 179-192.
	S.S. Chung and C.S. Poon (2000), "A comparison of waste reduction practices and the new environmental paradigm in four southern Chinese areas", Environmental Management, Vol. 26, No.2, pp. 195-206.
	I.M.L. Lo, C.I. Tang, X.D. Li and C.S. Poon (2000), "Leaching and microstructural analysis of cement-based solidified wastes", Environmental Science and Technology, Vol. 34, pp. 5038, 5042.

D. Contact person

Professor C. S. Poon

Tel:(852) 2766 6024, Fax: (852) 2334 6389, Email: cecspoon@polyu.edu.hk

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