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Wastewater Treatment Objectives, Characteristics

and Regulations

Jim Park, ProfessorCivil and Environmental Engineering

University of Wisconsin-Madison

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Treatment Objectives

1980 to 2000Removal of toxic compounds and nutrients

(N & P)

Early 1970s to 1980Based on aesthetic and environmental

concernsBegan to address nutrient removalImproved treatment efficiency and

widespread treatment of wastewater

1900 to early 1970s Removal of suspended and floatable materialTreatment of biodegradable organicsElimination of pathogenic organisms

21st CenturyEndocrine disrupting chemicals (EDCs) and

other synthetic compounds, emerging pathogens, etc.

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Change of Regulatory Policy

Conventional Pollutants (BOD & SS)

Conventional Pollutants (BOD & SS) +Specific Toxics (Priority Pollutants)

Water Quality-Based Permit Limitationsfor Toxic Pollutants

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Water Quality-Based Permit Approach

To control pollutants beyond specific toxics based controls

Applied where violations of water quality standards are identified or projected

Two-phased approach: Chemical specific approach Whole-effluent approach

Create a challenge to develop effective and economical techniques for toxics control

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Minimum National Standardsfor Secondary Treatment

Parameters Units 30-day ave. conc. 7-day ave. conc.

BOD5 mg/L 30/45a 45/65

Suspended solids mg/L 30/45a 45/65 Hydrogen-ion conc. pH units 6~9b 6~9b

Carbonaceous BOD5c mg/L 25 40

a Average removal 85%b Only enforced if caused by industrial wastewater or

by in-plant chemical additionc May be substituted for BOD5 at the option of the

National Pollution Discharge Elimination System (NPDES) permitting authority

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Water Quality Parameters Organic matter

Biochemical oxygen demand (BOD5) Chemical oxygen demand (COD) Total organic carbon (TOC)

Toxic compounds Priority pollutants

Fats, oils, and grease Inorganic matter

pH, chlorides, alkalinity, nitrogen (total Kjeldahl nitrogen [TKN], ammonia, nitrate, and nitrite), phosphorus, and sulfur

Bioassay

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Bioassay

Mysidopsis bahia, female, approx. 6 mm in length

Ceriodaphnia dubia

Brachionus calyciflorus

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Typical Composition of Raw Domestic Wastewater

Strength

WeakMediu

m StrongSolids, total (TS), mg/L 350 720 1200 Total dissolved (TDS), mg/L 250 500 850 Total suspended (TSS), mg/L 100 220 350Settleable solids, mg/L 5 10 20BOD5, mg/L 110 220 400COD, mg/L 250 500 1000Nitrogen (total as N), mg/L 20 40 85 Organic, mg/L 8 14 35 Free ammonia (NH4

+), mg/L 12 25 50 Nitrite & nitrate, mg/L 0 0 0Phosphorus (total as P), mg/L 4 8 15 Organic, mg/L 1 3 5 Inorganic, mg/L 3 5 10Chlorides, mg/L 30 50 100Sulfate, mg/L 20 30 50Alkalinity, mg/L as CaCO3 50 100 200Grease, mg/L 50 100 150

Total coliform, #/100 mL106~107 107~108 107~109

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Wastewater Treatment ProcessesSuspended solids

Screening and comminutionGrit removalSedimentationFiltrationFlotationChemical polymer additionCoagulation/sedimentationNatural systems (land treatment)

Volatile organicsBiological degradationAir strippingOff gas treatmentActivated carbon adsorption

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Biodegradable organicsActivated sludge variationsFixed-film reactor: trickling filtersFixed-film reactor: rotating biological contactorsLagoon variationsIntermittent sand filtrationPhysical-chemical systemsNatural systems

PathogensChlorination/hypochlorinationBromine chlorideOzonationUV radiationNatural systems

Wastewater Treatment Processes - continued

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Wastewater Treatment Processes - continuedNitrogen - nutrient

Suspended-growth nitrification/denitrification Fixed-film nitrification/denitrificationAmmonia strippingIon exchangeBreakpoint chlorinationNatural systems

Phosphorus - nutrientMetal-salt additionLime coagulation/sedimentationBiological phosphorus removalBiological-chemical phosphorus removalNatural systems

Nitrogen and phosphorus - nutrientsBiological nutrient removal

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Wastewater Treatment Processes - continued

Refractory organicsCarbon adsorptionTertiary ozonationNatural systems

Heavy metalsChemical precipitationIon exchangeNatural systems

Dissolved organic solidsIon exchangeReverse osmosisElectrodialysis

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Electrodialysis

Dissolved species are moved away from the feed stream rather than the reverse. Because the quantity of dissolved species in the feed stream is far less than that of the fluid, electrodialysis offers the practical advantage of much higher feed recovery in many applications.

Ion permeable membranes

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Electrodialysis - Application

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1,750 gpm

30~40%

1,050 gpm

15Austin, TX

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Sludge Processing/Disposal MethodsThickening

Gravity thickeningFlotationCentrifugationGravity belt thickeningRotary drum thickening

StabilizationLime stabilizationHeat treatmentAnaerobic digestionsAerobic digestionComposting

ConditioningChemical conditioningHeat treatment

http://biosolids.org/docs/mgp_chapter5_solids_thickening_dewatering_jan%202005.pdf

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DisinfectionPasteurizationLong-term storage

DewateringVacuum filterCentrifugeBelt press filterFilter pressSludge drying bedsLagoons

Thermal reductionMultiple hearth incinerationFluidized bed incinerationWet air oxidationVertical deep well extractor

Ultimate disposalLand applicationDistribution and marketingLandfillLagooningChemical fixation

Sludge Processing/Disposal Methods

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Sludge Volume ReductionExampleVolume of sludge: 10 × 106 gallonSolids content: 1%Weight of sludge = 10 × 106 gal × 8.34

lb/gal × 0.01 = 83,400 lbThickening & dewatering to 5, 15, 30, and

50%What are the volume reductions at each

solids content?What are the costs for hauling at each

solids content?

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Calculations - Volume5% solids content

x gal × 83,400 lb/gal × 0.05 = 834 lb Vol. = 83,400 lb ÷ (8.34 × 0.05) = 2,000,000

gal15% solids content

Vol. = 83,400 lb ÷ (8.34 × 0.15) = 667,000 gal

30% solids contentVol. = 83,400 lb ÷ (8.34 × 0.3) = 333,000 gal

50% solids contentVol. = 83,400 lb ÷ (8.34 × 0.5) = 200,000 gal

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Calculations – Hauling Costs$5 per cubic yard of biosolids1% solids content

10,000,000 gal × 0.00495 yd3/gal × $5 = $247,500

5% solids content 2,000,000 gal × 0.00495 yd3/gal × $5 = $49,500

15% solids content667,000 gal × 0.00495 yd3/gal × $5 = $16,500

30% solids content333,000 gal × 0.00495 yd3/gal × $5 = $8,250

50% solids content200,000 gal × 0.00495 yd3/gal × $5 = $4,950

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% Solids 0.01 0.05 0.15 0.3 0.5

Solids vol. (gal) 10,000 2,000 667 333 200

Water vol. (gal) 9,900 1,900 567 233 100

Hauling cost, $ 247,500 49,500 16,500 8,250 4,950

0

20,000

40,000

60,000

0 0.1 0.2 0.3 0.4 0.5 0.6

Hau

ling

cost

s, d

olla

rs

% Solids

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Process SelectionNeeds theoretical knowledge and practical

experiencePrincipal elements of process analysis

Development of the process flow diagramEstablishment of process design criteria and

sizing treatment unitsPreparation of solids balancesEvaluation of the hydraulic requirements

(hydraulic profile)Site layout considerations

Upgrading/expansion of existing facilityCompatibility with existing facilitiesRequires new operational procedures and

additional training for proper O&M of new units

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Activate Sludge Process

London Wastewater Treatment Plant

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Trickling Filter

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Design ConsiderationsCost - initial and annual O&M costs

Order of magnitude estimates for conceptual planning

Budget estimates (during preliminary design stage)

Definitive estimates derived from detailed quantity takeoffs of completed plans and specifications

Environmental - environmental impact statement

Equipment availabilityPersonnel requirementsEnergy and resource requirements

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Project ManagementFacilities planning: define problems, identify

design year needs (usually > 20 years), define/develop/analyze alternative treatment/disposal systems, select plan, and outline an implementation plan (financial arrangements and schedule)

Design: conceptual, preliminary, and final design with field testing for design criterion development

Value engineering: intensive review of a project by experts (1/3 and 2/3 of the project schedule)

Construction: ease of integration of new facilities into existing sites, clarity of presentation, spec. of high quality materials of construction, timely completion of work, and minimum changes

Startup and Operation: O&M manual

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Wastewater TreatmentPlant Layout

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Nine Springs Wastewater Treatment Plant, Madison, Wisconsin

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Hydraulic ProfileGraphical representation of the hydraulic grade line through the treatment plant.

The vertical scale is intentionally distorted to show the treatment facilities and the elevation of the water suface.

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Impact of Flowrate and Mass-Loading Factors on Design

Rated capacity - average annual daily flowrate

Peak hydraulic flowrates - control the size of unit processes and interconnecting conduits

Peak process loading rates - control the size of unit processes and support systems

Goal - provides a wastewater treatment system that is capable of coping with a wide range of probable wastewater conditions while complying with the overall performance requirements.

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Typical Design Flowrate and Loading Factors Used for Sizing

Flowrate based

Factor Application

Peak hour Pumping facilities and conduits, bar-rack; grit chambers, sedimentation tanks, and filters; chlorine-contact tanks

Max. day Sludge pumping system> 1-day max.Screenings and grit storageMax. week Record-keeping and reportingMax. month Record-keeping and reporting, chemical

storage facilitiesMin. hour Turndown of pumping facilities and low

range of plant flowmeterMin. day Influent channels to control solids

depositionMin. month Min. number of operating units required

during low-flow periods

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Typical Design Flowrate and Loading Factors Used for Sizing

Mass loading based

Factor Application

Max. day Selected biological processing units> 1-day max. Sludge-thickening and -dewatering systemsSustained peaks Selected sludge processing unitsMax. month Sludge storage facilitiesMin. month Process turndown requirementsMin. day Trickling-filter recycle

Procedure for selecting design flow rate:Average flow rates based on population projections, industrial flow contributions, and allowances for infiltration/inflow

Peak flow rate = Average flow rate Peaking factor

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Forecasting Design FlowratesExpansion projectPopulation of 15,000, 25,000 resident expected after 20

years plus 1000 visitors per day from a proposed college (assume 15 gal/capita/day)

A new industry - ave. = 0.22 Mgal/day, peak = 0.33 Mgal/day for 24 hr operation; present ave. daily flowrate = 1.6 Mgal/day

Infiltration/inflow = 25 gal/capita/day at ave. flow and 37.5 gal/capita/day at peak flow occurring during day shift

Residential water use in the new home is expected to be 10% less than in the current residences because of the installation of water-saving appliances and fixtures

Compute future average, peak, and min. design flowrates.

Assume that the ratio of min. to ave. flowrate is 0.35 for residential min. flow rates and the industrial plant is shut down one day a week.

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Solution1. Compute the present and future wastewater

flowratesa. For present conditions, compute the ave. domestic

flowrate excluding infiltrationInfiltration: 15,00025 gal/capita/day=375,000 gal/dayDomestic: Total ave. flow - Infiltration = 1,600,000 - 375,000 = 1,225,000 gal/day

b. Compute present per capita flowratePer capita flow rate = 1,225,000 15,000 persons

= 81.7 gal/capita/day c. Future conditions: 10% reductionFuture flow rate = 81.7 0.9 = 73.5 gal/capita/dayTotal dry-weather base flow: 120 gal/capita/day

[70 + 10 (commercial/small industrial flows) + 40 (infiltration)]

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2. Compute future ave. flowratea. Existing residents = 1,225,000 GPDb. Future residents = 10,000 73.5 = 735,000

GPDc. Day students = 1,000 15 gal/capita/day =

15,000 GPDd. Industrial flow (given) = 220,000 GPDe. Infiltration = 25,000 25 gal/capita/day =

625,000 GPD Total future flow rate = 2,820,000 GPD = 2.82

Mgal/day3. Compute min. flow ratea. Residential min. flowrate = 0.35 1.6 = 0.56

Mgal/dayb. Industrial min. flowrate = 0 Mgal/day Total min. flow rate = 0.56 Mgal/day

Solution - continued

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4. Compute future peak flow ratea. Peak hourly = 1.975 Mgal/day 3.1 = 6.12

Mgal/dayb. Industrial peak (given) = 0.33 Mgal/dayc. Infiltration = 25,000 37.5 gal/capita/day 0.94

Mgal/day Total future peak flowrate = 7.39 Mgal/day

Solution - continued

3.1

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Important Factors in Process SelectionProcess applicabilityApplicable flow rateApplicable flow variationInfluent-wastewater characteristicsInhibiting and unaffected constituentsClimatic constrainsReaction kinetics and reactor selectionPerformanceTreatment residualsSludge processingEnvironmental constrainsChemical requirementsEnergy requirementsPersonnel requirementsOperating and maintenance requirements

Ancillary processesReliabilityComplexityCompatibilityLand availability

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Treatment Efficiency

Treatment units BOD COD SS P Org-NNH3-N

Bar racks 0 0 0 0 0 0Grit chambers 0~5 0~5 0~10 0 0 0Primary sedimentation 30~4030~4050~6510~2010~200Activated sludge 80~9580~8580~9010~2015~508~15Trickling filters High rate, rock media 65~8060~8060~858~12 15~508~15 Super rate, plastic media 65~8565~8565~858~12 15~508~15Rotating biological contactors (RBCs) 80~8580~8580~8510~2515~508~15Chlorination 0 0 0 0 0 0

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Typical Design Periods

Facility Planning period range, yrsCollection systems 20~40Pumping stationsStructures 20~40Pumping equipment10~25

Treatment plantsProcess structures 20~40Process equipment 10~20Hydraulic conduits 20~40

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Secondary Clarifier

Use the upper level for beneficial use

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Top of the Wastewater Treatment Facility

Basket ball court and green area above the secondary clarifiers

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