CIVL3007-EIA-2010-6-Solid waste

CIVL3007-EIA-2010-6- - CIVL3007-2010 Dr Zhang T Sources Types Quantities Compositions and Environmental Impacts of Solid Wastes 1 Wasted Sludge 2

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1 Sources, Types, Quantities, Compositions, and Environmental Impacts of Solid Wastes CIVL3007-2010 Dr. Zhang T 1. Wasted Sludge 2. Municipal Solid Waste (MSW) 3. Construction Waste
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2 Sources of Wastes -1 • Municipal Solid Waste (MSW): – Domestic waste: household/street waste, junk and bulky waste – Commercial waste: commercial mixed waste, junk waste, market waste, paper waste • Sludge: – Waterworks sludge – Sewage sludge – Oil and grease • Construction and demolition waste: – Excavated material (site formation) – Mixed site clearance (new building works, road, railroads, tunnels, bridges, piers, etc.) – Renovation waste (building renovation) – Demolition waste (buildings and roadwork, etc.) – Roadwork material (maintenance of roadwork, etc.)
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3 Sources of Wastes -2 Dredged and excavated marine spoil Industrial waste : esp. from manufacturing industry Chemical waste : containing toxic chemicals/materials as specified by EPD; esp. from metal finishing and electroplating industry Clinical waste : hospital waste Special waste : animal carcasses, radioactive waste Ash: 1) Coal ash from electric power generation –2 ) Incinerator ash from waste incineration • Agricultural waste: – Livestock waste – Crop residue •O t h e r w a s t e : –A s b e s
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4 Sludge Treatment and Disposal • Generation – Primary – Secondary – Chemical • Characteristics – Water contents – VS (volatile solid) – Hazardous chemicals – Pathogen •T r e a t m e n t – Thickening – Stabilization – Conditioning – Dewatering –D r y i n
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5 What removed from watstewater? • Suspended solid •O r g a n i c s Where do they go? Sludge yield : 0.3-0.5 g/ g BOD
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6 Final disposal
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7 Sources and Amount of Sludge -1 Solid (primary solid/sludge): primary sedimentation tank Biosolid (secondary solid/sludge): secondary sedimentation tank Prediction of sludge generation : ( Mass Balance Model ) – Ws = Wsp + Wss Ws: total dry solid Wsp: primary solid Wss: secondary solid – Wsp = f • TSS • Q f : fraction of suspended solid removal in primary settling; 0.4-0.6 , 0.6 for domestic wastewater TSS: total suspended solid in wastewater Q: flow rate –W s s = Y ( B O D in -BOD out ) • Q Y (sludge yield): fraction of influent BOD that is converted into new bacteria cell body, 0.3-0.5 HK : TSS = 200 mg/L
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8 Sources and Amount of Sludge -2 Prediction of sludge amount (emission factors) Domestic wastewater – primary sludge (from primary treatment/sedimentation): 35 g/cap-day – secondary sludge (from secondary/biological treatment): 25 g/cap-day – chemical sludge (from tertiary/chemical treatment): varying – mixed or combined sludge: sum of the above • Commercial effluent 30 g/cap-day
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This note was uploaded on 12/01/2010 for the course CIVL 2007 taught by Professor Profchai during the Spring '10 term at HKU.

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CIVL3007-EIA-2010-6- - CIVL3007-2010 Dr Zhang T Sources Types Quantities Compositions and Environmental Impacts of Solid Wastes 1 Wasted Sludge 2

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