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Sewage and Effluent Treatment

Sewage and Effluent Treatment. 2-4 November 2002 Seán Moran -The first few slides. Day One: 2 November 2002. Overview: Wastewater Engineering Wastewater Characteristics Wastewater Treatment Considerations Overview: Wastewater Treatment Plant Design

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Sewage and Effluent Treatment

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  1. Sewage and Effluent Treatment 2-4 November 2002 Seán Moran -The first few slides

  2. Day One: 2 November 2002 • Overview: Wastewater Engineering • Wastewater Characteristics • Wastewater Treatment Considerations • Overview: Wastewater Treatment Plant Design • Physical, Chemical and Biological Processes

  3. Overview: Wastewater Engineering • Wastewater Treatment • Wastewater is the water used by a community • Collected and treated prior to discharge • Standards of treatment vary but are generally becoming more stringent • Treatment is a process of removal of smaller and smaller particles

  4. Overview: Wastewater Engineering • Sludge Treatment • Sludges are the product of biological treatment of wastewater • Sludges comprise solids found in wastewater plus organisms used in the treatment process • Disposal is a major issue • Various disposal techniques are used but each has advantages and disadvantages

  5. Overview: Wastewater Engineering • Water Disposal and Re-Use • Wastewater treatment generates a Cleaned Water Stream • Cleaned water is often discharged to a larger body of water for dilution • Alternatively, cleaned water my be re-used for irrigation or rarely drinking water production

  6. Wastewater Characteristics Characteristics are normally estimated by empirical methods • Wastewater Flows • Flows arise from households, industry, infiltration and storm flows • Flows are considered in both hydraulic and process design • Levels of treatment may vary for different flowrates

  7. Wastewater Characteristics • Wastewater Flows • There is a variety of methods for estimating flowrates • However there may be great variability in the factors which affect flowrates from region to region • Different multiples of the Dry Weather Flow will receive each level of treatment

  8. Wastewater Characteristics • Wastewater Composition • Key design issues: • Solids: density, particle size, level of Volatile Suspended Solids • Biochemical Oxygen Demand • Temperature • Ammonia • Nutrient levels

  9. Wastewater Characteristics • Wastewater Treatment Considerations • Objective: to maintain or improve the quality of the receiving body of water • Treatment stages: • Preliminary • Primary • Secondary • Tertiary

  10. Wastewater CharacteristicsClassification of Methods

  11. Wastewater Characteristics • Applicability and Selection of Methods • Different processes are used to treat wastewater depending on the contaminants present • Similarly, different processes are used to treat sludges, depending on the objective of treatment

  12. Overview: Wastewater Treatment Plant Design • Flowrate and Mass Loading • Wastewater feed is not specified, therefore the plant must be able to treat whatever the wastewater contains • Plant design will take account of historical flows and loadings, but must also be able to deal with expansion • Plant must also be able to deal with a range of flow and load conditions, plus peak upstream flow conditions (eg storms)

  13. Overview: Wastewater Treatment Plant Design • Selection of Design Flowrates • Domestic: based on a flow per head. Varies between countries • Industrial: Based on records of discharge consents and of metered supplies • Infiltration/Exfiltration: based on a % of the domestic flow • Peaking Factors: Depends on size of community

  14. Overview: Wastewater Treatment Plant Design • Selection of Design Flowrates • Upstream Flow Equalisation • Plants are not normally designed to treat total peak arisings • Instead, hydraulic controls will direct flows above plant capabilities to storm system on larger works

  15. Overview: Wastewater Treatment Plant Design • Selection of Design Flowrates • Upstream Flow Equalisation • UK maximum flow to treatment plant is determined by Formula A: • Formula A = PG+E+I+1360P+2E l/d P=population G=average daily consumption per head l/h/d E=Industrial & commercial discharges to sewer l/d I=infiltration l/d

  16. Overview: Wastewater Treatment Plant Design • Selection of Design Flowrates • Upstream Flow Equalisation • For larger works with storm tanks, only “Full Treatment Flow” (FTF) will receive full treatment. FTF=3PG+3E+I • Formula A-FTF will pass to storm tanks

  17. Overview: Wastewater Treatment Plant Design • Selection of Design Mass Loadings • Average mass loadings for BOD and Suspended Solids are commonly determined by Population Equivalent (PE) • Design mass loadings are more complex and must take account of seasonal, diurnal and industrial load variations

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