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