u_Lecture_Apr_13

u_Lecture_Apr_13 - IV ENVIRONMENTAL TECHNOLOGIES How Sewage...

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IV: ENVIRONMENTAL TECHNOLOGIES How Sewage is Dealt With 1. Contents of domestic wastewater 2. Conveyance/transport of wastewater 3. Design of wastewater treatment plants - preliminary - primary - secondary - tertiary - sludge/solid waste treatment 4. Other options
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Characteristics of domestic sewage Total solids 700 mg/L dissolved solids 500 mg/L suspended solids (SS) 200 mg/L fixed 50 mg/L volatile 150 mg/L Settleable solids 10 ml/L Biochemical Oxygen Demand (BOD 5) 200 mg/L
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Domestic sewage characteristics con’t Nitrogen (total as N) 40 mg/L Phosphorus (total as P) 10 mg/L
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Effluent standards Biochemical Oxygen demand (5 day) (BOD 5 ) 20 mg/L Suspended solids (SS) 20 mg/L
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Population Equivalent (PE) Domestic sewage BOD 5 = 200 mg/L flow = 330 Lpcd BOD 5 load per person = 66 g/d
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Milk processing plant BOD 5 = 1400 mg/L flow = 0.25 ML/d BOD load = 350 kg/d PE = industry load/domestic load = 350/0.066 = 5300 people
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IV: ENVIRONMENTAL TECHNOLOGIES How Sewage is Dealt With 1. Contents of domestic wastewater 2. Conveyance/transport of wastewater 3. Design of wastewater treatment plants - preliminary - primary - secondary - tertiary - sludge/solid waste treatment 4. Other options
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Suspended solids Amount of material which can be filtered from the sample on a standard filter media. (dissolved solids will not be trapped by filter media) SS contain a significance amount of the BOD and therefore exert an oxygen demand on receiving waters
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•Remove ±pathogens • Reduce organic carbon load, or biochemical oxygen demand (BOD) • Remove Toxic Chemicals
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Biochemical Oxygen Demand (BOD) – amount of oxygen that can be consumed by microbes. BOD 5 = amount of oxygen consumed over the period of 5 days at 20 o C N-BOD – nitrogenous BOD….amount of oxygen consumed due to the oxidation of NH 4 + to NO 3 - .
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Types of pathogens found in wastewater
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IV: ENVIRONMENTAL TECHNOLOGIES How Sewage is Dealt With 1. Contents of domestic wastewater 2. Conveyance/transport of wastewater 3. Design of wastewater treatment plants - preliminary - primary - secondary - tertiary - sludge/solid waste treatment 4. Other options
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Conveyence – sanitary sewerage system By gravity when possible. .. min velocity = 0.3 m/s
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Typical construction drawing
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Combined sewers exist in older cities…
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Pretreatment of Sewage Some treatment occurs in the sewer system prior to sewage reaching the treatment plant sewer pipes MUST NOT flow full pipes flow approx 2/3 full maximum provides oxygen for aerobic bacteria action
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IV: ENVIRONMENTAL TECHNOLOGIES How Sewage is Dealt With 1. Contents of domestic wastewater 2. Conveyance/transport of wastewater 3. Design of wastewater treatment plants - preliminary - primary - secondary - tertiary - sludge/solid waste treatment 4. Other options
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usually only physical treatment removes approx:
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u_Lecture_Apr_13 - IV ENVIRONMENTAL TECHNOLOGIES How Sewage...

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