REFRESHER COURSE ON SEWAGE TREATMENT PLANT DESIGN

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Module 2

• Wastewater Treatment Technologies

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I Flow Sheets of Water Treatment
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Sample 1 - Sample 7
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Indian Standards for Drinking Water Quality
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• Unit Operations and Processes
• Screening
• Aeration
• Sedimentation
• Coagulation
• Flocculation
• Filtration (Rapid sand/ Slow sand)
• Water softening
• Disinfection

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• Unit Operations and Processes
• Equalisation
• Neutralisation
• Grit removal
• Flotation
• Chemical ppn
• Ion exchange
• Adsorption
• Biological processes (aerobic / anaerobic)
• Chemical/ advanced oxidation processes
• Wet air oxidation
• Filtration processes (RO/UF/NF)

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• Factors considered for evaluating selecting
  Unit Operations Processes
• Process applicability
• Applicable flow range
• Applicable flow variation
• Influent ww characteristics
• Inhibiting constituents
• Climatic constraints
• Process sizing based on reaction kinetics
• Process sizing based on mass transfer rates

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• Factors considered for evaluating selecting
  Unit Operations Processes
• 9 performance
• treatment residuals
• Sludge processing
• Envi constraints
• Chemical requirements
• Energy requirements
• Other resource requirements
• Personnel requirements
• OM requirements
• Ancillary processes
• Reliability
• Complexity
• Compatibility
• Adaptability
• Economic life cycle analysis
• Land availability

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(a) Surface Water
Chlorination
Storage
Turbidity lt10 NTU No odour, No colour
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(b) Ground Water
Chlorination
Turbidity lt10 NTU No odour, No colour
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(c) Surface Water
Plain Sedimentation
Slow sand filtration
Chlorination
Turbidity gt50 NTU Sufficient area available
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(d) Surface Water
Highly polluted water with algae and
microorganisms)
Chlorination (pre)
sedimentation
Aeration
Coagulation
Flocculation
Chlorination (Post)
Rapid sand Filtration
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(e) Water with excessive hardness
Softening
Rapid Sand Filtration
Chlorination (Post)
Excessive Hardness
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II Flow Sheets of Wastewater Treatment
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Effluent Disposal and utilisation

• Water body, land ( disposal )
• Reclamation ( industrial reuse )
  
• Reuse in agriculture, horticulture
• GW recharge

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SOLIDS( Raw
sewage99.9 water0.1 solids)

• Solids 50 suspended 50 dissolved
• Solids 70 organic 30 inorganic

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Sewage characteristics (Major
Pollutants)

• Suspended solids
• Biodegradable organics
• Pathogens
• Nutrients
• Dissolved inorganic solids
• Waste Oxygen Oxidised
  waste
• New bacterias

bacteria
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Typical composition of domestic waste water
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Indian Standards Related to Disposal of Treated
Effluents
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Basic design considerations

• 1.Degree of treatment (Water Act1974)
• 2.Design period (30 years)
• 3.Population (future population)
• 4.Sewage Flows (Peak, Average, Min)
• 5.Sewage characteristics
  

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Basic design considerations (cont.)

• 6.Effect of industrial wastes
• 7.Effluent disposal and utilization
• 8.Unit operations processes for treatment
• 9.Design of process flow sheets for treatment
• 10. Choice of processes

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• Design of process flow sheets for treatment

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• Unit Operations and Processes
• Physical (screening, grit removal
  sedimentation)
• Chemical (Coagulation, flocculation)
• Biological suspended / attached growth, aerobic
  / anaerobic

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Typical wastewater treatment process
Pre-treatment Eg physical/chemical treatment,
solids separation
Treatment Biological treatment Eg aerobic/
anaerobic suspended/attached batch/continuous
Post-treatment Egfiltration, adsorption
Discharge of clean effluent
BIOREACTOR
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Aerobic Biological Treatment Processes

• Suspended Growth
• Activated sludge
• Oxidation ditches/ponds
• Aerated lagoons, stabilization ponds
• Attached Growth
• Trickling filters
• Rotating Biological Contactors (RBCs)

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CHOICE OF PROCESSES
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Activated Sludge

• Process in which a mixture of wastewater
  microorganisms is agitated aerated
• Leads to oxidation of dissolved organics
• After oxidation, sludge is separated from
  wastewater
• DT approximately 6 - 8 hr

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Trickling Filters

• Rotating distribution arm sprays primary effluent
  over circular bed of rock or other coarse media.
• Air circulates in pores between rocks.
• Biofilm develops on rocks and micro-organisms
  degrade wastes as they flow past

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Trickling Filters
Filter Material
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SLUDGE DRYING
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