tech 110: pretreatment technologies
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Tech 110:Tech 110:Pretreatment TechnologiesPretreatment Technologies
Between the tank and the soilBetween the tank and the soil
Overview of PretreatmentOverview of Pretreatment
Adapted from The University Curriculum for Adapted from The University Curriculum for Decentralized Wastewater Management Decentralized Wastewater Management
Prepared by: John R. Buchanan, Univ. of TN; Prepared by: John R. Buchanan, Univ. of TN;
Robert W. Seabloom, Univ. of WA; Robert W. Seabloom, Univ. of WA;
Dave Lenning, Alternatives NorthwestDave Lenning, Alternatives Northwest
Edited by: David Lindbo and Nancy Deal, NCSUEdited by: David Lindbo and Nancy Deal, NCSU
NDWRCDP DisclaimerNDWRCDP DisclaimerThis work was supported by the National Decentralized Water This work was supported by the National Decentralized Water Resources Capacity Development Project (NDWRCDP) with Resources Capacity Development Project (NDWRCDP) with
funding provided by the U.S. Environmental Protection Agency funding provided by the U.S. Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881-01-0) through a Cooperative Agreement (EPA No. CR827881-01-0) with Washington University in St. Louis. These materials have with Washington University in St. Louis. These materials have
not been reviewed by the U.S. Environmental Protection not been reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by Agency. These materials have been reviewed by representatives of the NDWRCDP. The contents representatives of the NDWRCDP. The contents
of these materials do not necessarily reflect the views and of these materials do not necessarily reflect the views and policies of the NDWRCDP, Washington University, or the U.S. policies of the NDWRCDP, Washington University, or the U.S.
Environmental Protection Agency, nor does the mention of trade Environmental Protection Agency, nor does the mention of trade names or commercial products constitute their endorsement or names or commercial products constitute their endorsement or
recommendation for use.recommendation for use.
CIDWT/University DisclaimerCIDWT/University Disclaimer
These materials are the collective effort of individuals from These materials are the collective effort of individuals from academic, regulatory, and private sectors of the academic, regulatory, and private sectors of the
onsite/decentralized wastewater industry. These materials have onsite/decentralized wastewater industry. These materials have been peer-reviewed and represent the current state of been peer-reviewed and represent the current state of
knowledge/science in this field. They were developed through a knowledge/science in this field. They were developed through a series of writing and review meetings with the goal of formulating series of writing and review meetings with the goal of formulating a consensus on the materials presented. These materials do not a consensus on the materials presented. These materials do not
necessarily reflect the views and policies of University of necessarily reflect the views and policies of University of Arkansas, and/or the Consortium of Institutes for Decentralized Arkansas, and/or the Consortium of Institutes for Decentralized
Wastewater Treatment (CIDWT). The mention of trade names or Wastewater Treatment (CIDWT). The mention of trade names or commercial products does not constitute an endorsement or commercial products does not constitute an endorsement or
recommendation for use from these individuals or entities, nor recommendation for use from these individuals or entities, nor does it constitute criticism for similar ones not mentioned.does it constitute criticism for similar ones not mentioned.
CIDWT/University DisclaimerCIDWT/University DisclaimerThese materials are the collective effort of individuals from These materials are the collective effort of individuals from
academic, regulatory, and private sectors of the academic, regulatory, and private sectors of the onsite/decentralized wastewater industry. These materials have onsite/decentralized wastewater industry. These materials have
been peer-reviewed and represent the current state of been peer-reviewed and represent the current state of knowledge/science in this field. They were developed through a knowledge/science in this field. They were developed through a
series of writing and review meetings with the goal of series of writing and review meetings with the goal of formulating a consensus on the materials presented. These formulating a consensus on the materials presented. These materials do not necessarily reflect the views and policies of materials do not necessarily reflect the views and policies of
North Carolina State University, and/or the Consortium of North Carolina State University, and/or the Consortium of Institutes for Decentralized Wastewater Treatment (CIDWT). Institutes for Decentralized Wastewater Treatment (CIDWT).
The mention of trade names or commercial products does not The mention of trade names or commercial products does not constitute an endorsement or recommendation for use from constitute an endorsement or recommendation for use from
these individuals or entities, nor does it constitute criticism for these individuals or entities, nor does it constitute criticism for similar ones not mentioned.similar ones not mentioned.
Why Pretreat? Why Pretreat?
““Pretreat” wastewater so downstream Pretreat” wastewater so downstream component(s) can function more reliably component(s) can function more reliably
for longer termsfor longer terms
Pretreatment OptionsPretreatment Options
Traditionally, have been categorized as:Traditionally, have been categorized as: PrimaryPrimary – solids removal – solids removal SecondarySecondary –organics and BOD removal –organics and BOD removal TertiaryTertiary – generally, nutrient removal – generally, nutrient removal
Microbes typically used to assistMicrobes typically used to assist Aerobic Aerobic AnaerobicAnaerobic FacultativeFacultative
Aerobic and anaerobic processes are Aerobic and anaerobic processes are compatiblecompatible
Primary treatmentPrimary treatment
Septic tanksSeptic tanks Grease trapsGrease traps Grease interceptorsGrease interceptors
Primary treatment: Septic tanksPrimary treatment: Septic tanks
FunctionsFunctions Separate solids Separate solids
from liquidfrom liquid Anaerobic Anaerobic
decompositiondecomposition Attenuate Attenuate
surgessurges VentilationVentilation
Primary treatment: Septic tanksPrimary treatment: Septic tanks
Most common unit for OWTSMost common unit for OWTS Used alone or with other pretreatment Used alone or with other pretreatment
unitsunits Simple and generally inexpensive ($100s)Simple and generally inexpensive ($100s) 30-50% reduction BOD30-50% reduction BOD55, 60-80% , 60-80%
reduction TSSreduction TSS
Primary treatment: Grease trapsPrimary treatment: Grease traps FunctionFunction
Remove grease and oilsRemove grease and oils Used where greases/oils expected (usually Used where greases/oils expected (usually
commercial sites like restaurants)commercial sites like restaurants) Does not normally receive blackwaterDoes not normally receive blackwater
Primary treatment: grease separatorsPrimary treatment: grease separators
Typically, proprietary productsTypically, proprietary products High maintenance productsHigh maintenance products Historically, not good performance Historically, not good performance
because of poor maintenancebecause of poor maintenance
Advanced pretreatmentAdvanced pretreatment
Secondary treatmentSecondary treatment TSS and BOD removalTSS and BOD removal Microbes typically used to assistMicrobes typically used to assist
• Aerobic Aerobic • AnaerobicAnaerobic• FacultativeFacultative
Secondary treatmentSecondary treatment Use aerobic microorganisms to provide Use aerobic microorganisms to provide
secondary treatment to domestic wastewatersecondary treatment to domestic wastewater Focuses on removal of biodegradable organics Focuses on removal of biodegradable organics
and suspended solidsand suspended solids Convert soluble particulates to insoluble ones so Convert soluble particulates to insoluble ones so
we can remove themwe can remove them usually accomplished with biological reactorsusually accomplished with biological reactors
Biodegradable organics must be removed to Biodegradable organics must be removed to minimize impact on subsequent processesminimize impact on subsequent processes
Aerobic reactionsAerobic reactions
If enough dissolved OIf enough dissolved O22 is in the effluent is in the effluent
then the effluent is Aerobicthen the effluent is Aerobic OO2 2 > 1.0 ppm> 1.0 ppm
Bacteria break down waste constituents Bacteria break down waste constituents under these conditionsunder these conditions
RespirationRespiration
CO2 O2
H2O
NitrificationNitrificationNH3
NO2
NO3
H2O
NO2
O2
O2
Providing Dissolved Oxygen (DO)Providing Dissolved Oxygen (DO)
Advanced treatment systems are designed Advanced treatment systems are designed to provide lots of DOto provide lots of DO high-rate carbon removal and ammonificationhigh-rate carbon removal and ammonification occupies a small-footprintoccupies a small-footprint requires energy to maximize oxygen transferrequires energy to maximize oxygen transfer biological reactorbiological reactor
BODBOD
Often used as a measure of wastewater Often used as a measure of wastewater strengthstrength a high BOD suggests that the organic a high BOD suggests that the organic
compounds are easily biodegradablecompounds are easily biodegradable indicates the mass of dissolved oxygen that indicates the mass of dissolved oxygen that
could be removed by aerobic microbes as could be removed by aerobic microbes as they metabolize they metabolize
Secondary treatment devices reduce the Secondary treatment devices reduce the oxygen demand of a wastewateroxygen demand of a wastewater
Advanced pretreatmentAdvanced pretreatment
Tertiary treatmentTertiary treatment Generally, nutrient removal Generally, nutrient removal DisinfectionDisinfection
Anoxic/anerobic reactionsAnoxic/anerobic reactions
If all OIf all O22 is low effluent becomes is low effluent becomes
anoxic/anaerobicanoxic/anaerobic• OO2 2 < 0.5 ppm< 0.5 ppm
DenitrificationDenitrification
N2 gasNO3
CO2
It’s all about the It’s all about the bugs (Microbes)bugs (Microbes)
Optimizing a natural processOptimizing a natural process
Bioreactors are built to maximize the Bioreactors are built to maximize the production of beneficial end-productsproduction of beneficial end-products alcohols (beer, wine)alcohols (beer, wine) insulininsulin other medicationsother medications
AndAnd Renovate wastewaterRenovate wastewater
The good bugsThe good bugs
Convert colloidal and dissolved carbonaceous Convert colloidal and dissolved carbonaceous organic matter into various gases and into cell organic matter into various gases and into cell tissuetissue gases evolve (COgases evolve (CO22, N, N22, and others), and others) new cells can settle – thus carbon is removednew cells can settle – thus carbon is removed
Break other nutrients out of organic compoundsBreak other nutrients out of organic compounds nitrogenous compoundsnitrogenous compounds phosphorus speciesphosphorus species
The bad bugsThe bad bugs
PathogensPathogens Use disinfection to inactivate theseUse disinfection to inactivate these Generally UV, ChlorineGenerally UV, Chlorine
The soil…The soil…
Is a bioreactor too!Is a bioreactor too!
Groundwater
Well
Aerobic soil needed for treatment
Shallow system = Aerobic Shallow system = Aerobic treatmenttreatment
Groundwater
Well
Low OLow O22 results in less aerobic soil results in less aerobic soil
therefore treatment therefore treatment
Deep system = Less aerobic to Deep system = Less aerobic to anaerobic systemanaerobic system
Advanced treatmentAdvanced treatment
Lessens the burden placed on the soilLessens the burden placed on the soil Allows use of less-than-optimum sitesAllows use of less-than-optimum sites
Increased risk requires attention to O&MIncreased risk requires attention to O&M
Wastewater TreatmentWastewater Treatment
Examples of Aerobic Bioreactors used for Examples of Aerobic Bioreactors used for Secondary TreatmentSecondary Treatment activated sludge plantsactivated sludge plants rotating biological contactorsrotating biological contactors packed-bed media filterspacked-bed media filters
Highly-engineered systems that utilize Highly-engineered systems that utilize microbial metabolism to convert organic microbial metabolism to convert organic compounds into cells and carbon dioxidecompounds into cells and carbon dioxide
Environmental EffectsEnvironmental Effects
Microbes need more than organic carbon, Microbes need more than organic carbon, dissolved oxygen and waterdissolved oxygen and water need steady supply of food to maintain stable need steady supply of food to maintain stable
microbial populationmicrobial population pH needs to be monitoredpH needs to be monitored
• low alkalinity can cause large changes in pHlow alkalinity can cause large changes in pH Be careful with biocidesBe careful with biocides
• acid drain cleaneracid drain cleaner• antibiotics antibiotics
Environmental effects: Environmental effects: TemperatureTemperature
Overall, as temperature rises, microbial Overall, as temperature rises, microbial activity increases (but not too hot)activity increases (but not too hot)
Microbes can be grouped by temperature Microbes can be grouped by temperature preferencepreference Psychrophilic microorganismsPsychrophilic microorganisms
• optimum temperature 12optimum temperature 12° to 18° C° to 18° C Mesophilic microorganismsMesophilic microorganisms
• optimum temperature 25° to 40° Coptimum temperature 25° to 40° C Thermophilic microorganismsThermophilic microorganisms
• optimum temperature 55° to 65° Coptimum temperature 55° to 65° C
SummarySummary
Aerobic Treatment of WastewaterAerobic Treatment of Wastewater takes advantage of a natural processtakes advantage of a natural process process can be easily engineered into a process can be easily engineered into a
biological reactor for high-rate wastewater biological reactor for high-rate wastewater treatmenttreatment
removes the oxygen demand from wastewater removes the oxygen demand from wastewater before being discharged back into the hydrologic before being discharged back into the hydrologic cyclecycle
Carbon is transformed into cell mass and into Carbon is transformed into cell mass and into carbon dioxide carbon dioxide
Questions?Questions?
N Cycle in Septic SystemsN Cycle in Septic Systems
Nitrification and SorptionNitrification and Sorption
Denitrification ?Denitrification ?
Min
eral
izat
ion
Min
eral
izat
ion
ImmobilizationImmobilization
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