CTC 450 Review

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CTC 450 Review

• WW Systems Operations

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Last Homework

• Will replace your lowest homework grade
• http//www.epa.gov/climatechange/ghgemissions/usin
  ventoryreport.html
• http//www.ipcc.ch/
• How significant are wastewater treatment plants
  in contributing to greenhouse gasses?
• Due next Monday

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Objectives

• Understand the basics with respect to advanced WW
  treatment

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Two systems

• Advanced (tertiary and ww reclamation)
• Remove phosphorous
• Convert ammonia to nitrate (nitrification)
• Convert nitrate to nitrogen (denitrification)
• Inactivate pathogens
• Remove heavy metals
• Remove organic chemicals
• Remove inorganic salts
• Eliminate all pathogens

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Limitations-Biological Treatment

• Doesnt remove phosphorous or ammonia
• Incomplete disinfection
• Doesnt remove all toxins
• Doesnt remove non-biodegradable soluble
  chemicals

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Excess Phosphorous

• Fertilizes receiving waters
• Causes algal blooms
• Depletes DO
• Reduces water transparency
• Releases foul odors
• Can lose finer fish species

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Excess Nitrogen

• Ammonia can be toxic to fish/aquatic animals
• Can increase eutrophication (but usually
  phosphorous is limiting)

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Pathogens

• Conventional biological treatment
• Up to 99.9 removal
• With disinfection up to 99.99
• Protozoal cysts and helminth eggs are resistant

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SS Removal-Advanced

• Granular-Media filters (similar to water
  treatment)
• Cloth Media filters
• Membrane filters

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Pathogen Removal-Advanced

• Remove solids first via filtration (pathogens can
  be protected in the solids)
• Chlorination (similar to water treatment)

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Toxic Substance Removal

• Toxic-Hazardous to aquatic life or human health
• Priority toxic water pollutants-over 100
• Evaluating toxicity
• Test influent/effluent for specific substances
• Biomonitor-fathead minnows, water fleas

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Phosphorous Removal

• Soluble or organic (organically bound)
• Conventional treatment removes 20-40 of
  phosphorus
• Example 13-1
• Advanced treatments
• Chemical-biological
• Reverse osmosis

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Example 13-1 (Where is the PO43-)

• Given the following, trace the inorganic, organic
  and total phosphorus through a conventional
  activated-sludge treatment plan.
• Assume
• Primary clarifier removal of 35 BOD
• Primary clarifier removal of 50 solids w/ 0.9
  phosphorous
• Activated sludge
• F/M ratio of 0.40 2 phosphorus in the sludge
• Filtrate recycles 5 of the influent phosphorus

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Example 13-1
Parameter Raw After Primary After Secondary
SS 240 120 30
BOD 200 130 30
Inorganic N 22 22 24
Organic N 13 8 2
Total N 35 30 26
Inorganic P 4 4 3
Organic P 3 2 2
Total P 7 6 5
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Example 13-1 (Refer to Figure 13-11)Plant
Influent / Primary Influent

• Total P is 7 mg/l into the plant (100)
• Primary influent is not the same as plant
  influent because of recycle of dewatered sludge
  filtrate
• Recycled P5 so influent P105
• Total P is 7.35 mg/l into the primary

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Example 13-1 (Refer to Figure 13-11)Primary
Effluent (2 routes)

• Sludge (15)
• 0.9120 mg/l 1.1 mg/l
• 1.1/7 15
• Effluent (90) 7.35-1.16.25 mg/l total
• Pi4.35 (see table no change in inorganic P)
• Po1.90 (6.25-4.35)
• 6.25/7 90

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Example 13-1 (Refer to Figure 13-11)Secondary
Effluent (2 routes)

• Sludge (20)
• From Fig 11-45 (pg 415) k0.5
• Biological sludge solids0.5130 mg/l65mg/l
• 2 of 65 mg/l 1.3 mg/l
• 1.3/7 20
• Effluent (70) 7.35-1.16.25 mg/l total
• Pi3.05 (see table inorganic P is removed)
• (6.25-1.3-1.9)
• Po1.90 (see table organic P is not removed)
• 4.95/7 70

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Example 13-1 (Refer to Figure 13-11)

• 70 of P remains in the treated WW
• 30 of P removed in sludge solids

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Chemical-Biological

• Chemicals used
• Alum
• Iron Salts
• Chemical-Biological
• Chemicals added in primary clarifiers
• Chemicals added before secondary
• Chemicals added before final clarifier

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Example 13-2 (Refer to Figure 13-12)Add alum to
remove P

• Alum applied to primary tank
• 18 of P remains in the treated WW
• 82 of P removed in sludge solids

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Nitrogen-Atmospheric

• Atmospheric Nitrogen to Organic Molecules
• Nitrogen-fixing bacteria (rhizobia)
• Live in root nodules of plants (symbiotic
  relationship)
• Legumes (beans, clover, peas, peanuts,)
• Plants get nitrogen in a usable form
• Animals get nitrogen from eating plants
• Animals excrete nitrogen as a waste product,
  usually in the form of ammonia

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Nitrogen

• Organic
• Excreted or Decomposed to ammonia
• Ammonia
• Nitrosomonas oxidize ammonia to nitrite
• Nitrite
• Nitrobacter oxidize nitrite to nitrate
• Nitrate
• Under anaerobic conditions via facultative
  heterotrophs, nitrates are converted to nitrogen
  gas (which escapes into the atmosphere)
• Nitrogen gas

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New Type of Microbe

• Ammonia to nitrogen directly
• NH4 NO2- ? N2 2H2O
• Anammox (anaerobic ammonium oxidation)
• Advantage No oxygen needed
• Strangeness anammox bugs also produce hydrazine
  (rocket fuel)
• Bugs store the hydrazine in a dense membrane
  structure of fused carbon rings
• Ref The Invisible Kingdom, Idan Ben-Barak

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Nitrogen in WW

• 40 ammonia 60 is bound in organic matter
• Usually not enough oxygen is available to convert
  to nitrites or nitrates

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Nitrogen Removal-Conventional

• Primary sedimentation (15 removal)
• Biological treatment (another 10)
• Remainder is mainly in the form of ammonia unless
  oxidation occurs (activated sludge at low BOD
  loading)

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Nitrogen Removal-Advanced

• After biological treatment
• Aeration
• Final settling
• Alkalinity is reduced when nitrification takes
  place lime or soda ash is added to maintain
  alkalinity

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Nitrate removal

• Nitrate can pollute groundwater
• Denitrification converts nitrates to nitrogen gas
• Process is anaerobic or anoxic
• Process requires an organic carbon source
  (methanol or raw ww)
• Via recycle, denitrification can be placed ahead
  of nitrification

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EBPR-Enhanced Biological Phosphorous Removal

• Anoxic zone (0.5 to 3 hours detention time)
  followed by aerobic zone (6-24 hrs)
• Helps remove both N and P