Sewage Treatment (1)

8/2/2019 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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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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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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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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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

Sewage Treatment (1)

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