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1
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
23
Activate Sludge Process
London Wastewater Treatment Plant
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Trickling Filter
25
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
26
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.
30
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.
31
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
32
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
33
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
38
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
39
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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