Post on 17-Jan-2016
Wastewater Treatment
Jae K. (Jim) ParkDepartment of Civil and Environmental
Engineering
University of Wisconsin-Madison
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Microorganisms – ClassificationsEnergy Solar radiation: Photo-synthetic autotrophs,
e.g., algaeOrganics: Heterotrophs, e.g., activated sludge
biomass, denitrifiers, etc.Inorganics: Chemoautotrophs, e.g., nitrifiersOxygen useObligate (strict): use only one condition for
growthFacultative: use either dissolved oxygen or
chemically derived oxygen (from nitrate, sulfate or carbonate) for respiration and use organic materials for energy and growth
Temperature Psychrophiles: < 20°C., opt. 13°CMesophiles: 20~45°C, opt. 35°CThermophiles: 45~60°C, opt. 55°C
Organic Matter Energy for Mircoorganisms
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Carbonaceous Energy: Carbon as energy
sourceHeterotrophs
Nitrogenous Energy: Nitrogen as energy
sourceChemoautotrophs
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Energy Measurement (1)
Theoretical Oxygen Demand (ThOD)Chemical Oxygen Demand (COD)Biochemical (Biological) Oxygen
Demand (BOD)Carbonaceous BOD (C)Nitrogenous BOD (N)
Total Organic Carbon (TOC)
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Energy Measurement (2)Theoretical Oxygen Demand (ThOD)1. Carbonaceous demand: C CO2; N NH3
2. Nitrogenous demand: NH3 HNO2; HNO2 HNO3
3. ThOD = O2 req. in steps 1& 2
Ex. Glycine (10 mg/L) [CH2(NH2)COOH] (MW = 75 g/mol)
1. Carbonaceous demandCH2(NH2)COOH + 1.5O2 2CO2 + H2O + NH3
2. Nitrogenous demandNH3 + 1.5O2 HNO2 + H2O; HNO2 + 0.5O2 HNO3
3. ThOD = [1.5 + (1.5+0.5)] mol O2/mol glycine
= 3.5 × 32 g O2/mol = 112 g O2/mol = 112 75 g/mol = 1.49 g O2/g
glycineThus, ThOD = 1.49 x 10 mg/L = 14.9 mg/LCannot be used if chemical composition is not
known.
Energy Measurement (3)
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H2SO4
322
272ban 2cCrOH
28ca
nCO 8cHOcCrOHC HeatCatalyst
silver sulfateDichromate
3b
6a
32n
c
Chemical Oxygen Demand (COD) O2 req. for oxidation of organics Oxidize carbonaceous matter with a strong
oxidant (e.g., hot dichromate sol. with sulfuric acid)
Reduction of O2
4e- + 4H+ + O2 2H2O1 mole of O2 (32 g) 4e- equivalents1 g COD 1 g O2 1/8 electron equiv.
NH3 not oxidized (carbonaceous energy only) Aromatic hydrocarbons (benzene and
toluene) and pyridines are not oxidized
Domestic WastewaterCOD Fractionation
Influent COD(Sti)
Particulateunbiodeg.COD (Supi)
Sol. readilybiodegradable
COD (Sbsi)
Solubleunbiodeg.COD (Susii)
Partic. slowlybiodegradable
COD (Sbpi)
BiodegradableCOD (Sbi)
UnbiodegradableCOD (Sui)
100%
~80%
~20% ~60% ~7% ~13%
~20%
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Energy Measurement (4)
Oxygen consumption by microorganisms
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Carbonaceousenergy
Time, days
DO
con
sum
ed
, m
g/L
Nitrogenousenergy
5
BOD5
BODu
Biochemical (Biological) Oxygen Demand (BOD) O2 required for microbial decomposition
Inadequate to assess the electron donor capacity; after 5 days, still some biodegradable matters exist.
~30
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Biochemical (Biological) Oxygen Demand (BOD) Carbonaceous BOD: aerobic heterotrophs
Decompose organic molecules to minerals (CO2) and residues
Obtain their cell carbon from the organic material
Nitrogenous BOD: obligate aerobic chemoautotrophs
Characteristics of nitrifiers (chemoautotrophs)DO < 2 mg/L action slowDO < 0.5 mg/L action ceasesOptimum pH: 8.0; pH < 7.2: slows downMore sensitive than heterotrophs to
toxinsSlow growers (longer sludge age
required)
Energy Measurement (5)
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Inert Organic MatterMeasured with CODNot biodegraded, thus not measured with
BOD5
Polymerized waste productInert material from lysed cellsRefractory organics: humic acid (M.W. -
5000~100,000); fulvic acid (2,000~10,000)Certain high M.W. carbohydrates alone or in
combination with humic material are resistant to microbial attack.
High M.W. carbohydrates are excreted at the end of the logarithmic growth phase and help forming flocs by bridging of bacterial cells.
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Acclimated Culture
Selection of populations by controlling environmental factors to encourage only the desired species.
An increase in the biodegradation rate of a chemical after exposure of the microbial community to the chemical for some period of time.
Example of Acclimation
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0 5 10 15 20 25 30 35 40Days
0
5
10
15
20
25
Con
cent
ratio
n, m
g/L
Result of acclimation
CO2 production
Microbial biomass
Chemical concentration
Lag phaseAcclimation
Bio
mass co
nc., m
g/L
CO
2 pro
ductio
n, v
ol.
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Example AcclimationHazardous Industrial Wastewater
Biological Treatment
RB
W
Day 1
RB
WN
BW
Day 2
RB
WN
BW
Day 3
RB W
NB
W
Day 4N
BW
Day 5
Feedratio
RBW: Readily biodegradable wastewater, e.g., glucose, methanol, domestic wastewater, etc.
NBW:Not readily biodegradable wastewater, e.g., industrial wastewater, hazardous wastewater, polychlorinated biphenyls (PCBs), pentachlorophenol, etc.
Influence of Acclimated Biomass
on COD of Treated Wastewaters
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CO
D, m
g/L
UntreatedRaw
Treated withunacclimated
biomass
Treated withacclimated
biomass
BOD5 equivalents
Not readilyBiodegradabl
eCOD
Non-biodegradableCOD
BOD: Not affected by acclimationCOD: Significantly affected by acclimation
Total COD – BOD5
BOD, CODCr, CODMn, TOC
Organic matter
Biodegradable Unbiodegradable
TOC
CODCr
CODMn
BOD5
Cl-, H2S
Cl-, H2S
Nitrification
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Total Organic Carbon (TOC) Oxidize in a combustion chamber with O2
Easy to measureGlucose, C6H12O6 (M.W. = 180)C6H12O6 + 6 O2 6 CO2 + 6 H2O6 moles O2 6 4 = 24 e-
24/6 = 4 e- available per unit organic CEx. 100 mg/L of glucose: TOC and COD = ? TOC: (6 12)/180 100 = 40 mg/L C COD: (6 32)/180 100 = 107 mg/L OGlycerol, C3H8O3 (M.W. = 92)C3H8O3 + 7/2 O2 3 CO2 + 4 H2O7/2 moles O2 7/2 4 = 14 e-
14/3 = 4.67 e- available per unit organic CEx. 100 mg/L of glycerol: TOC and COD = ? TOC: (3 12)/92 100 = 39 mg/L C COD: (3.5 32)/92 100 = 122 mg/L O
• TOC values are very similar for both glucose and glycerol; however, COD values are quite different.
• Thus, waste specific; cannot apply the result to other WWTPs.
• Good as an operational tool with previous historical data.Similar
Different
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Energy Measurement (6)O2 + 4H+ + 4 e- = 2 H2O
Energy Measurement (7)
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BOD5/COD ratio: a good indicator for biodegradability of a specific wastewater
Domestic wastewater BOD5/COD 0.4 ~ 0.8 BOD5/TOC 1.0 ~ 1.6
BOD5/COD 0.6: can be decomposed completely, biological treatment feasible
BOD5/COD 0.2: cannot be decomposed easily, chemical or physical treatment desired
BOD5/COD 0: has toxic materials
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TOC Analyzer
On-Line TOC Analyzer: a reagentless analyzer designed for continuous monitoring of organics.
Measure the amount of total organic carbon present in a liquid sample;
Convert inorganic carbon in the sample to CO2 after adding acid and strip CO2 by a sparge carrier gas;
Oxidize organic carbon by either combustion, UV persulfate oxidation, ozone promoted, or UV fluorescence; and
Measure CO2 stripped using the conductivity or non-dispersive infrared (NDIR) detection system.
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Use of BOD5, COD, and TOCBOD5Good for regulating organic loading to a
receiving water body for DO depletion by heterotrophs
Not good for design since some organics biodegrade slowly or after acclimation
CODNot good for regulation since it does not reflect
true organic loading impact to aqua systemsGood for design if the input and output within
a biological system is monitored; true energy count for carbonaceous energy only
TOCGood for operating a wastewater treatment
plant due to real time monitoring capabilityValues cannot be transferred to other
wastewater due to specificity of carbon in the wastewater in terms of electro donor capability
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Priority PollutantsDesignated by EPA in 1979 A list of 126 specific pollutants that includes
14 heavy metals and 112 specific organic chemicals
Heavy Metals (Total and Dissolved): heavy, dense, metallic elements that occur only at trace levels in water, but are very toxic and tend to accumulate
Pesticides: DDT, Aldrin, Chlordane, Endosulfan, Endrin, Heptachlor, and Diazinon
Polycyclic Aromatic Hydrocarbons (PAHs): naphthalene, anthracene, pyrene, and benzo(a)pyrene
Polychlorinated biphenyls (PCBs): organic chemicals that formerly had widespread use in electrical transformers and hydraulic equipment
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Fats, Oils, and Grease (FOG)
Sewage backups and overflows can lead to costly clean ups and repairs, as well as public health concerns.
Many utilities acknowledge fat, oil, and grease (FOG) as the main cause of sewer clogging.
EPA estimated that utilities spend on average $33,000 per mile of sewer per year on capital project and $8,000 per mile for O&M (2004).
The capital investment in wastewater infrastructure is over $13 billion annually (EPA, 2002).
Local government and utilities pay up to 90% of capital expenditures on wastewater infrastructure (AMSA and WEF, 1999).
Causes of Sanitary Sewer Overflow
Blockages (48%)
Wet weather I/I (26%)
EPA, 2004
Mechanical orpower
failures (11%)
Misc. (5%)Line breaks (10%)
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Causes of Sewer Clogging
FOG (47%)
Grit, rock, and other debris (27%)
Roots (22%)
Roots and FOG (4%)
EPA, 200423
Sewer Clogging
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FOG
Wastewater
Consequences of Sewer CloggingSewer overflow
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Consequences of Sewer CloggingOdor
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H2S + 2O2 H2SO4Crown corrosion of concrete pipes
Bacteria
Consequences of Sewer CloggingOdor
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Trans Fatty Acids (TFA)Created in an industrial process that adds
hydrogen to liquid vegetable oils to make them more solid
Easy to use, inexpensive to produce, and last a long time
Give foods a desirable taste and textureUse trans fats to deep-fry foods because
oils with trans fats can be used many times in commercial fryers
Raise bad LDL (low density lipoproteins ) cholesterol levels and lower your good HDL (high density lipoproteins) cholesterol levels
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Use of Zero Trans Fatty Acids
Inefficient removal in conventional grease removal systems
Potential foaming in wastewater treatment plant aeration basins
No knowledge on the fate of zero trans fatty acids in sewers and wastewater treatment plants
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Prevention of Sewer Clogging (1)
Grease trap or interceptors, exhaust hood filters, and floor mats
Proprietary grease removal devices
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Prevention of Sewer Clogging (2)
Chemicals and additives (emulsifiers, detergents or caustic substances) that claim to dissolve grease Prohibited for use as an additive because these
substances reduce the efficiency of the interceptor or trap
Best Management Practices (BMP) during daily operations to keep FOG out of drains leading to the sewer
EnzymesProhibited as additives due to the same effect as
emulsifiersMicroorganisms
Not prohibited as an additiveEducation
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NitrogenMain species
Organic nitrogenNH4
+: Ionized ammonia, nutrient to algae
NH3: Free (unionized) ammonia, toxic to fish
NO2-: Intermediate byproduct of
nitirification, < 1 mg/L, causes the hemoglobin in the blood to change to methemoglobin, cause methemoglobinemia (‘blue baby’ syndrome)
NO3-: Final product of nitrification,
undeveloped digestive tracts of an infant possess bacteria that convert nitrate into nitrite, < 10 mg/L
Nitrogen Transformationin Biological Treatment
ProcessesOrganic nitrogen(proteins, urea,
etc.)
Ammonia nitrogen(NH3-N)
Nitrite (NO2-)
Bacterial decompositionand hydrolysis
Organic nitrogen(bacterial cells)
Organic nitrogen(net growth)
Assimilation
Nitrate (NO3-)
O2
O2
Lysis and autooxidation
Nitrogen gas (N2)Denitrification
Organic carbon(substrate)
Nit
rifica
t ion
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Subdivision of Total Influent TKN
Influent TKN(Nti)
Unbiodegrad.soluble N
(Nui)
Biodegrad.N
(Nai)
Organicallybound N (Nti - Nai)
Unbiodegrad.Particulate N
(Npi)~3% ~10% ~12%
~75% ~25%
100%
NH3&NH4-
(Nai)
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Total Kjeldahl Nitrogen (TKN): sum of organic nitrogen, ammonia(NH3), and ammonium (NH4
+) in biological wastewater treatment
Free Ammonia (Unionized, NH3) and Ionized (NH4
+) Ammonia
Temperature effectMoretoxic
Moretoxic
pH effect
Ammonia not regulated in winter
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Nitrification: Chemoautotrophs (1)
Oxygen demand
N gO g
3.43N
molg
14mol 1
O 2molg
16mol 1.5
NO to NHof Conversion 24
N gO g
1.14N
molg
14mol 1
O 2molg
16mol 0.5
NO to NOof Conversion 3-2
Nitrification: Conversion from ammonia to NO2
- / NO3-
Total oxygen demand for nitrification: 4.57 g O/g N
NH4+ + 1.5O2 NO2
- + H2O + 2H+ + New biomass
Nitrosomonas
NO2- + 0.5O2 NO3
- + New biomassNitrobactor
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Nitrification: Chemoautotrophs (2)
CO2 (carbonate): carbon source
Ammonia: energy transfer source in a non-assimilative way so only a small amount of biomass (sludge) is produced
H+ +CO32-
→ HCO3-; H+ +HCO3
- → H2CO3
Alkalinity2H+ 1 mol alkalinity [CaCO3
(40+12+16×3=100 g/mol)]100 g Alk/14 g N = 7.14 g Alk consumed/g
N nitrified
NH4+ + 1.5O2 NO2
- + H2O + 2H+ + New biomass
Nitrosomonas
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Nitrification: Chemoautotrophs (3)
Example Influent TKN = 42 mg N/L; Effluent TKN 2
mg/LAlkalinity = 200 mg/L as CaCO3
Oxygen demand?4.57 g O/g N × (42 – 2) mg N/L = 182.8 mg
O/L Alkalinity after nitrification?7.14 g Alk/g N × (42 – 2) mg N/L = 285.6
mg/L as CaCO3 Unless additional alkalinity (CaO, Na2CO3,
NaOH, etc.) is added, nitrification will stop (see the next slide).
Since the influent is 200 mg/L, 85.6 mg/L + 10~15 mg/L (residual) = 95.6~100.6 mg/L as CaCO3 required
Effect of pH on Nitrification
Operational range
Nitrifiers: very sensitive to pHThus, buffer capacity (alkalinity) of wastewater important
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40
Denitrification: Heterotrophs (1)
2NO3- + 10e- + 12H+ → N2
+ 6H2O
N/e g 2.8e 10
molN g
14 mol 2
O2 + 4e- + 4H+ → 2H2O
O/e g 8
e 4mol
O g16 mol 1 2
N gO g
2.86
eN g
2.8
eO g
8
saved O 63%100tion)(nitrifica
N gO g
4.57
cation)(denitrifiN gO g
2.86
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Denitrification : Heterotrophs (2)
~1 mol of H+ is recovered from denitrification
Thus, Alk of 3.57 g/g N recovered
For low alkalinity water, denitrification is recommended.
Denitrification conditionsNo O2Readily biodegradable soluble substrate (COD)
For complete removal of nitrogen species from wastewater: nitrification followed by denitrification
Substrate Requirementfor Denitrification
CODutilized = CODbiomass + O2 utilized = fcv X + O2 utilized = YCOD CODutilized + O2 utilized
fcv = COD/VSS = CODbiomass/X (mg COD/mg VSS)YCOD = CODbiomass/CODutilized (mg COD/mg COD)
O2 utilized = (1 - YCOD) CODutilized YCOD = fcv Yh (mg VSS/mg COD)
C5H7O2N + 5O2 5CO2 + 2H2O + NH3
(5 × 16 × 2 g) (1 × 113 g) = 1.42 mg COD/mg VSSCOD/VSS = 1.42 mg COD/mg VSS
O2 = (1 - fcvYh) CODutilized
Nitrate consumption per mg COD utilized2.86 mg O2/mg NO3
- N (1 - 1.42·0.47) mg O2/mg COD = 8.6 mg COD req./mg NO3
--N denitrified42
Biomassempirical formula
0.67
0.67 0.33
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COD Requirement for Denitrification
ExampleCODinf = 400 mg/L, CODeff = 50 mg/L, TKNinf =
55 mg N/L, TKNeff = 5 mg N/L, Q = 10 MGDCOD (methanol) required for denitrification?Solution(55-5) mg N/L × 8.6 mg COD/mg N = 430 mg
COD/L req.[430-(400-50)] mg/L = 80 mg COD/L req.Methanol (CH3OH) (MW = 32 g/mol)CH3OH + 1.5O2 → CO2 + 2H2O80 mg COD/L×10 MGD 1.5×16×2 g COD/32
g MeOH = 202 kg/day = 445 lb of MeOH/day
Subdivision of Total Influent PInfluent TP
(Pti)
Organicallybound P (Pti - Pbi)
70 ~ 90% 10 ~ 30%
100%
10 ~ 20%in the activatedsludge process
Sol. PO4- (Psi)
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Source: human body waste, food waste, various household detergents
Phosphorus
Forms of Phosphate
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Old Now Forms5 4 Orthophosphate3 0 Tripolyphosphate (detergents)1 0 Pyrophosphate (breakdown of tri-
P)1 1 Organic phosphates0 ? Hexametaphosphate (corrosion
inhibitor)10 5 Total
mg/L
Why? Ban of phosphate-based detergents
Phosphorus in Wastewater
Addition to waterCorrosion (and scale) control in drinking water
Industrial water softeningBoiler watersCleaning compounds
Sewage1.2 lb/capita/yr from human and food waste
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PAOs
Mechanisms of Polyphosphate-Accumulating Organisms (PAOs)
Anaerobic condition Aerobic condition
Poly-P
PO4 3- PAOs
New Cell
PHA
GlycogenPHA
Glycogen
NADH, ATP
Short chain fatty acids
(SCFAs)(Acetate)
Organic substrate
Facultative microbes
ATP
Poly-P
PO4 3-
ATP
47PHA: Polyhydroxyalkanoates
Observations in Biological Phosphorus Removal (BPR)
Systems
Ortho-P
PHA
Acetate
Glycogen
AN O
Poly-P
BulkLiquid
Biomass
Reaction Time 48PHA: Polyhydroxyalkanoates
BPR Mechanism
Anaerobic Aerobicm
g/L
Time
Poly-β-hydroxybutyrate (PHB)(Storage) PHB Poly-
PPoly-P 49
Biomass Biomass
Acetate
Ortho-P
Anaerobic/Oxic Process
Excess sludgeBetter SRT control
Readily biodegradablesoluble COD
Vital for P Uptake
SRT: Solid retention time, sludge age, or mean cell residence time (MCRT); total biomass in the system/biomass wasted/loss
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Whole Effluent Toxicity
Bioassay
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Bioassay
52
Mysidopsis bahia, female, approx. 6 mm in length
Ceriodaphnia dubia
Part of whole effluent toxicity (WET) tests for NPDES permit
Use of a biological organism to test for chemical toxicity
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Use of Toxicity Testing in Water Quality Based
Toxics ControlTo characterize and measure the aggregate toxicity of an effluent or ambient waters
To measure compliance with whole effluent toxicity limits
As an investigative tool and to measure progress in a toxicity reduction program
As an ambient instream measure of toxicity to identify pollution sources
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BioassayTested sample: most commonly, effluent from
industrial or municipal wastewater dischargesSample holding time: max. 36 hrs stored at
4°CTest organisms
Ceriodaphnia dubia (water flea) Pimephales promelas (fathead minnow) Cyprinella leedsi (bannerfin shiner) Mysidopsis bahia (mysid shrimp) Menidia beryllina (tidewater silverside)
Acute test: 24, 48, or 96 hrs (species specific)Chronic test (short-term): 4~10 (7) days
Rules for Conducting Toxicity Tests
40 CFR 136.3 - Table 1A (List of Approved Biological Methods)
Effective November 15, 1995
Amended November 19, 2002 and effective December 19, 2002
Methods must be followed as they are written
Incorporate by Reference
Methods for Measuring the Acute Toxicity of Effluents to Freshwater and Marine Organisms. 5th Edition, USEPA, Office of Water, October 2002, EPA 821-R-02-012
Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms. 4th Edition, USEPA, Office of Water, October 2002, October 2002, EPA 821-R-02-013
Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Marine and Estuarine Organisms. 3rd Edition. USEPA, Office of Water, October 2002, EPA 821-R-02-014 56
USEPA Methods Documents
Health and safetyQuality assuranceFacilities, equipment and suppliesTest organisms and culture methodsDilution waterEffluent sampling and handlingEndpoints and data analysisIndividual test methodsReport preparation and test review
57
Test Types
Acute and Short-term Chronic TestsStatic non-renewalStatic renewalFlow through
Test Species dependentUse dependent
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Test Design5 Concentrations + Control
Serial dilution’s of effluent and “control water” (also termed “dilution water”)
Dilution series of 0.5 or greaterSingle concentration test
Replicates
Randomization (organisms/chambers)
Acute Toxicity TestsTest Procedures
96 hours or less (species specific)Mortality is the measured endpointFor daphnia mortality determined by immobilization
AdvantagesLess expensive and time consuming than chronic
Endpoint is easy to quantifyDisadvantages
Indicates only lethal concentrationsOnly the effects of fast acting chemicals are exhibited 60
Acute Test Acceptability Criteria
Minimum control survival at least 90%
Temperature maintained at 20±1o C
Maximum test organism age at start:14 days for fish5 days for Mysid shrimp24 hours for daphnids (Ceriodaphnia dubia and Daphnia magna)
61
Short-term Chronic Toxicity Tests
Test ProceduresTypically 4-10 daysMortality, growth, fecundity, reproduction
AdvantagesMore sensitive than acute, assess
parameters other than lethalityMay better reflect real world
LimitationsMore costly and time intensive than acuteMore sensitive to low level contamination
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Chronic Test Acceptability Criteria
Minimum control survival 80%Minimum control dry weight (average):
0.25 mg for fish0.20 mg for Mysid shrimp
Minimum of 15 young (average) for control C. dubia
Temperature maintained @ 25 +/- 1o CMaximum test organism age at start:
48 hours for fish7 days for Mysid shrimp24 hours for daphnids
63
Selection of Dilution Water
May be either a standard laboratory water or the receiving water
Choice of water is dependent on the objectives of the testAbsolute toxicity use standard waterEstimate of toxicity in uncontaminated receiving water, use receiving water
Contaminated receiving water, use laboratory water
64
Acute Test Endpoints
LC50 - Concentration of effluent that is lethal to 50 percent of the exposed organisms at a specific time of observation (e.g. 96 hr LC50), (expressed as % effluent)
NOAEC - No Observed Adverse Effect ConcentrationLowest concentration at which survival is not significantly different from the control
always set equal to 100% effluentEC - Effect Concentration
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Test Data
Typical dose response where mortality increases as the concentration of effluent in the mixture increases.
LC50 would be somewhere between 25% effluent and 50% effluent.
0% mortality
6.25 %
Effluent0%
Mortality
Control
20 % Mortality
12.5 %
Effluent 40%
Mortality
25.0% Efflue
nt80%
Mortality
50.0% Efflue
nt100%
Mortality
100.0%
Effluent
66
Chronic Test Endpoints
IC25 - Inhibition Concentration - Concentration of effluent which has an inhibitory effect on 25% of the test organisms for the monitored effect, as compared to the control (expressed as % effluent).
NOEC - No Observable Effect Concentration - Highest concentration of effluent tested which shows no statistically significant effect on the organisms as compared to the control (expressed as % effluent).
67
Toxicity Values
NPDES permits in the past used a “no observable effect concentration” (NOEC) to measure chronic toxicity and a 96-hour lethal concentration 50 (LC50) to measure acute toxicity.
Permits are now being issued with an inhibition concentration 25% (IC25).
68
Limit: more stringent
LC50, IC25
LC50, IC25, NOAEC
Toxicity
Toxic Units (TU’s)
Reciprocal of the fractional LC50, NOEC, IC25 value
Calculated by dividing the value into 100TUa = 100/LC50TUc = 100/IC25
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Methodology for Setting Limits (1)
IC25 is a calculation based on the design flow of the POTW and the seven-day low flow over 10 years in the receiving stream (7Q10) as follows:IC25 = design flow/(7Q10 + design flow) × 100
Example:The low flow for the receiving stream (7Q10) is
23 MGD. The design flow for the POTW is 4 MGD.IC25 = 4/(23+4) × 100
IC25 = 14.8% The POTW demonstrates toxicity if the test value
is less than or equal to the calculated value of 14.8%. This constitutes a violation of the NPDES permit.
71
A serial dilution that the laboratory: 59.2, 29.6, 14.8, 7.4, 3.7 and a control with 0% effluent.
Toxicity is demonstrated if there is a statistical significant difference in any dilution from the control set.
The difference can be in any of the three parameters: survival, reproduction, or growth.
In the example, the effluent fails if toxicity appears in the 14.8% or 7.4% or 3.7% dilutions.
Methodology for Setting Limits (2)
Redox Reaction
Organic molecule (C+H+O+N+S+P)
(wastewater, hazardous chemicals, etc.)
CO2, H+, and e-
A molecule
Oxidized
Reduced
Electron donor
Electron accepto
r72
Aerobic Condition
Aerobic respiration O2 present
Electron acceptor: O2 (→ H2O) Good for large volumes of dilute
wastewater (< 500 mg BOD5/L) High growth rates, thus high
sludge production (0.3~1 lb VSS/lb BOD5)
Produce a more stable end product
O
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Anoxic Condition
Anaerobic respiration (denitrification)
No dissolved oxygen
NO3- and NO2
- present
Electron acceptor: NO2- and NO3
- (→ N2 + H2O)
Relatively high sludge production
Should be avoided in the clarifier
AX
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Fermentation No O2, NO3
-, NO2-, or SO4
2- present Electron acceptor: endogenously generated
by the microorganism Good for concentrated wastes (> 1000 mg
BOD5/L) Low sludge production
Complex organic compounds
Low molecular weight fatty acids
CH4, CO2, and H2O
Anaerobic ConditionAN
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Microbial Classification
76
ChemoautotrophH2 bacteriaSulfur bacteriaNitrifiersIron bacteria
ChemoheterotrophAnimalsMost bacteriaFungiProtozoa
H2, S, H2S, Fe2+, NH3, NO3-Organics (reduced)
Organics (reduced)H2O, S, H2S
PhotoautotrophGreen plantsAlgaePurple bacteriaGreen bacteria
PhotoheterotrophFew algaeCyanobactorSome purple & green bacteria
Chemical
Electron donor
Electron donor
Light
EnergyCarbon
CO2 Organics
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Oxidation-Reduction Potential (ORP)
+300
+200
+100
0
-100
-200
-300
-400
ORPmV
Process
12
3
4
56 7
8
O2
SO42-
Carbonaceous organics
Electron acceptors
Conditions
Oxicor
aerobic
Anoxic
Fermentative anaerobic
1. Organic carbon oxidation2. Polyphosphate release3. Nitrification
4. Denitrification5. Polyphosphate uptake6. Sulfide formation
7. Acid formation8. Methane formation
NO3-
78
Three Origins of Life
Origin of life
Bacteria
Archaea
Eukarya
Phylogenetic Tree
The phylogenetic tree shows that the Eukarya are more closely related to the Archaea than they are to the Bacteria.
PROCARYOTA
79
ArchaeaA group of single-celled microorganismsRequires neither sunlight for photosynthesis
as do plants, nor oxygen. Absorbs CO2, N2, or H2S and gives off
methane gas as a waste product.
80
BacteriaSingle-celled microorganisms which can exist
either as independent (free-living) organisms or as parasites, typically 0.5–5.0 µm length
Shape
Ability to form spores Method of energy
production (glycolysis for anaerobes, cellular respiration for aerobes)
Nutritional requirements Reaction to the Gram stain
Classification
E. Coli