Sewage Treatment (1)
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Transcript of Sewage Treatment (1)
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Sewage TreatmentSewage Treatment
BIOS 415BIOS 415
Water MicrobiologyWater Microbiology
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What is Sewage or Wastewater?What is Sewage or Wastewater? Liquid wastes containing a variety of pollutants inLiquid wastes containing a variety of pollutants insuspension and solutionsuspension and solution
Eight General Categories of Water PollutantsEight General Categories of Water Pollutants
Oxygen Demanding Wastes (Biodegradable Organics)Oxygen Demanding Wastes (Biodegradable Organics)
Disease Causing Agents (pathogens and parasites)Disease Causing Agents (pathogens and parasites) NutrientsNutrients Synthetic Organic Compounds (SOCS)Synthetic Organic Compounds (SOCS) Inorganic Compounds and minerals (IOCS)Inorganic Compounds and minerals (IOCS)
SedimentSediment RadiationRadiation HeatHeat
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WasteWaterWasteWater Treatment FacilitiesTreatment Facilities
> 15,000 facilities in the US> 15,000 facilities in the US
Treat > 30 Billion gallons per dayTreat > 30 Billion gallons per day
80% small plants, treat < 1 MGD80% small plants, treat < 1 MGD
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Two General Types of SewageTwo General Types of Sewage
1) Sanitary or Domestic Sewage1) Sanitary or Domestic SewageCombination of Human and Animal excreta (fecesCombination of Human and Animal excreta (fecesand urine) (black water) and gray water fromand urine) (black water) and gray water from
washing, bathing and cooking.washing, bathing and cooking.
Human excreta: 100Human excreta: 100 500 g wet weight feces / day500 g wet weight feces / day
11 1.3 l urine / day1.3 l urine / day 1515 20 g BOD5 / day20 g BOD5 / day
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Domestic Sewage CompositionDomestic Sewage Composition
Protein: (40Protein: (40 60%)60%) CarbsCarbs: (25: (25 50%)50%)
Fats & Oils ( ~ 10% )Fats & Oils ( ~ 10% )
High in microorganisms, High in organic materialsHigh in microorganisms, High in organic materials
DeKalbDeKalb Sewage: 7Sewage: 7 mgdmgd w/ 2 tonsw/ 2 tonssolids per million gallonssolids per million gallons
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Two General Types of SewageTwo General Types of Sewage
2) Storm Sewage2) Storm Sewage Runoff. Carries excreta of animals, fecal and otherRunoff. Carries excreta of animals, fecal and otherorganisms, organic material (leaves, detritus) as well asorganisms, organic material (leaves, detritus) as well asminerals and metals.minerals and metals.
DeKalbDeKalb: Separate sanitary and storm: Separate sanitary and stormsystems, does NOT treat stormsystems, does NOT treat storm
Some localities: combined systems, problematicSome localities: combined systems, problematicduring large rainfallsduring large rainfalls
Infiltration / cross connectionsInfiltration / cross connections
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Primary Goals of Sewage TreatmentPrimary Goals of Sewage Treatment
Reduction / elimination of disease causingReduction / elimination of disease causingorganismsorganisms Pathogens and parasitesPathogens and parasites
Maintain Water QualityMaintain Water Quality
Reduction of organics (BOD)Reduction of organics (BOD) Reduction of nutrientsReduction of nutrients
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Sewage TreatmentSewage Treatment Primary: PhysicalPrimary: Physical
Screening or Bar FiltersScreening or Bar Filters Removal of large materialsRemoval of large materials
Grinding orGrinding or ComminutionComminution
Grinding and sedimentation of larger materialsGrinding and sedimentation of larger materials
Removal from Grit chamberRemoval from Grit chamber
Primary Sedimentation TanksPrimary Sedimentation Tanks
Decrease velocity of sewage:Decrease velocity of sewage:
Sedimentation of suspended solidsSedimentation of suspended solidsBiosolidsBiosolids (sludge) removed from bottom(sludge) removed from bottom
Low density material float (fats, oils)Low density material float (fats, oils)
Removed from surface by skimmer armRemoved from surface by skimmer arm
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PrimaryPrimary
Treatment:Treatment:
DeKalbDeKalb
Bar ScreensBar Screens
ComminutionComminution GritGritChambersChambers
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Rake andRake andSkimmerSkimmer
PrimaryPrimary
SedimentationSedimentation
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Primary TreatmentPrimary Treatment
Physical ProcessesPhysical Processes
Removes 45 to 85% of solidsRemoves 45 to 85% of solids
Removes about 25 to 50% BODRemoves about 25 to 50% BOD
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Sewage TreatmentSewage Treatment
Secondary: Primary + BiologicalSecondary: Primary + Biological
A)A) BiosolidsBiosolids from sedimentation and skimmingfrom sedimentation and skimming Organic CompoundsOrganic Compounds ---- MethaneMethane
Complex OrganicComplex Organic
MoleculesMoleculesMonomersMonomers
Organic Acids, AlcoholsOrganic Acids, Alcohols
andand KeytonesKeytonesAcetate, CO2, H2Acetate, CO2, H2
Methane (CH4)Methane (CH4)
Hydrolytic BacteriaHydrolytic Bacteria--FermentiveFermentive//AcidogenicAcidogenic
Bacteria e.g.Bacteria e.g. ClostridiumClostridium
--AcetogenicAcetogenic Bacteria e.g.Bacteria e.g.SyntrobacterSyntrobacter
--MethanogenicMethanogenic Bacteria e.g.Bacteria e.g.
MethanosarcinaMethanosarcina
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Secondary Treatment:Secondary Treatment:
A)A) BiosolidsBiosolids--Anaerobic DigestionAnaerobic Digestion
DewateringDewatering
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Sewage TreatmentSewage Treatment SecondarySecondary
B) Liquid Effluents from PrimaryB) Liquid Effluents from PrimarySedimentation TanksSedimentation Tanks
Containing soluble organic materialsContaining soluble organic materials
i) Trickling Filtersi) Trickling Filters
ii) Rotating Biological Contactors (ii) Rotating Biological Contactors (RBCsRBCs))iii) Activated Sludge Processesiii) Activated Sludge Processes
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Sewage TreatmentSewage Treatment
SecondarySecondary Liquid PhaseLiquid Phase
Trickling FiltersTrickling FiltersEffluent is sprayed over a bed of filter media,Effluent is sprayed over a bed of filter media,consisting of limestone, granite or plasticconsisting of limestone, granite or plastic
The media develops a The media develops a biofilmbiofilm consisting of: consisting of: Bacteria, fungi, algae, protozoa, rotifers andBacteria, fungi, algae, protozoa, rotifers and
variousvarious macroinvertebratesmacroinvertebrates
e.g.e.g. ZoogloeaZoogloea,, PseudomonasPseudomonas,, FlavobacteriumFlavobacterium,,AchromobacterAchromobacter,, AlcaligenesAlcaligenes, filamentous bacteria e.g., filamentous bacteria e.g.SpherotilusSpherotilus and nitrifying bacteria e.g.and nitrifying bacteria e.g. NitrosomonasNitrosomonas//NitrobacterNitrobacter..
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Secondary TreatmentSecondary Treatment LiquidLiquid
PhasePhase
AerobicAerobic
TricklingTrickling
FilterFilter
BODBOD up to 85%up to 85%
removalremoval
BacteriaBacteria 2020--90%90%
removalremoval
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Sewage TreatmentSewage Treatment
SecondarySecondary Liquid PhaseLiquid Phase
Activated SludgeActivated Sludge Employs an Aeration TankEmploys an Aeration Tank
Mix effluent with a slurry (liquor) of bacteriaMix effluent with a slurry (liquor) of bacterialaden waterladen water
Aerate vigorouslyAerate vigorously
Produces Produces flocfloc of Biomass of Biomass
> 300 strains of Bacteria and other organisms> 300 strains of Bacteria and other organisms
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Secondary TreatmentSecondary Treatment
LiquidLiquid
PhasePhase
AerobicAerobic
ActivatedActivatedSludgeSludge
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Sewage TreatmentSewage Treatment
Secondary / Tertiary ?Secondary / Tertiary ? Liquid PhaseLiquid Phase
Rotating Biological Contactors (Rotating Biological Contactors (RBCsRBCs)) akaaka:: BioDiscsBioDiscs
Series of plastic discs mounted on a horizontalSeries of plastic discs mounted on a horizontalshaft that rotate slowly through liquidshaft that rotate slowly through liquid pahsepahse
wastewater ~ 40% submergedwastewater ~ 40% submerged
Develop aDevelop a biofilmbiofilm
further reduce BOD and ammoniafurther reduce BOD and ammonia
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Secondary /Secondary /TertiaryTertiary
TreatmentTreatment
Liquid PhaseLiquid Phase
AerobicAerobic
Rotating BiologicalRotating BiologicalContactorsContactors
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Tertiary TreatmentTertiary Treatment Liquid PhaseLiquid Phase
Final SandFinal SandFiltrationFiltration
FurtherFurtherreducesreduces
BODBOD
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Disinfection:Disinfection:DischargeDischarge
ChlorinationChlorination
OzonationOzonation
UltravioletUltravioletirradiationirradiation