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Wastewater Treatment Wastewater Treatment in Soilsin SoilsJames L. Anderson, PhD
David GustafsonAziz Amoozegar, PhD
David Lindbo, PhD
Model Decentralized Wastewater Practitioner Curriculum
NDWRCDP DisclaimerNDWRCDP DisclaimerThis work was supported by the National Decentralized This work was supported by the National Decentralized
Water Resources Capacity Development Project Water Resources Capacity Development Project (NDWRCDP) with funding provided by the U.S. (NDWRCDP) with funding provided by the U.S.
Environmental Protection Agency through a Cooperative Environmental Protection Agency through a Cooperative Agreement (EPA No. CR827881Agreement (EPA No. CR827881--0101--0) with Washington 0) with Washington University in St. Louis. These materials have not been University in St. Louis. These materials have not been
reviewed by the U.S. Environmental Protection Agency. reviewed by the U.S. Environmental Protection Agency. These materials have been reviewed by representatives of These materials have been reviewed by representatives of
the NDWRCDP. The contents 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 policies of the NDWRCDP, Washington University, or the
U.S. Environmental Protection Agency, nor does the U.S. Environmental Protection Agency, nor does the mention of trade names or commercial products constitute mention of trade names or commercial products constitute
their endorsement or recommendation for use.their endorsement or recommendation for use.
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 peerbeen peer--reviewed and represent the current state of 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 these individuals or entities, nor does it constitute criticism for for similar ones not mentioned.similar ones not mentioned.
CitationCitationGustafson, D., J. Anderson, A. Amoozegar, and Gustafson, D., J. Anderson, A. Amoozegar, and
D.L. Lindbo. 2005. Wastewater Treatment in D.L. Lindbo. 2005. Wastewater Treatment in Soils Soils –– Power Point Presentation. Power Point Presentation. inin (D.L. (D.L. Lindbo and N.E. Deal eds.) Model Decentralized Lindbo and N.E. Deal eds.) Model Decentralized Wastewater Practitioner Curriculum. National Wastewater Practitioner Curriculum. National Decentralized Water Resources Capacity Decentralized Water Resources Capacity Development Project. North Carolina State Development Project. North Carolina State University, Raleigh, NC.University, Raleigh, NC.
OverviewOverview
What is Sewage?What is Sewage?What kinds of Systems?What kinds of Systems?What is Soil?What is Soil?How do Soils & Sewage interact?How do Soils & Sewage interact?
Biomat and the treatment environmentBiomat and the treatment environmentConcernsConcerns
SewageSewageWhat is it?What is it?
WaterWaterBacteria foodBacteria food
•• BODBOD•• NutrientsNutrients
TSSTSS•• SolidsSolids
PathogensPathogensSolutes Solutes OthersOthers
The BIG PictureThe BIG Picture
Impermeable Layer
Ground Water
Slow Moving
Lateral Flow
Deep Percolation
Slowly Permeable layer
Stream
Water Table
Ground WaterMounding
Vadose Zone
Septic System
WastewaterInput Runoff
Infiltration
Precipitation
Evapotranspiration
Well
SystemsSystems
High O2 flow to infiltrative surface – good treatment
Low O2 flow to infiltrative surface –poor treatment
Protection methodsProtection methods
Separation Separation VerticalVerticalCovered Covered
SetbacksSetbacks
What is Soil?What is Soil?Particles Particles –– TextureTexture
% Sand % Sand -- % Silt % Silt -- % Clay% ClayStructureStructure
Minerals & Nutrients Minerals & Nutrients Organic matterOrganic matter
Pores: Air & WaterPores: Air & WaterSurface AreaSurface AreaSoil OrganismsSoil Organisms
How wastewater is treated?How wastewater is treated?
Inside the trench the conditions are Inside the trench the conditions are AnaerobicAnaerobicAerobic environmentAerobic environmentBacteriaBacteriaUnsaturatedUnsaturatedFlow Flow
Depth & TreatmentDepth & TreatmentSeparation distance allows for interactions Separation distance allows for interactions with particles and bacteriawith particles and bacteriaOxygen is critical for aerobic environmentOxygen is critical for aerobic environmentShallower systems have more:Shallower systems have more:
ReRe--aeration potentialaeration potentialSeparationSeparationEvapotranspirationEvapotranspiration
Soil DevelopmentSoil Development
Parent MaterialParent MaterialSoil profileSoil profile
Environmental ChangesEnvironmental ChangesLandscape PositionLandscape Position
Parent MaterialParent Material
TillTillOutwashOutwashLoessLoessLacustrineLacustrineBedrockBedrock
Weather bedrockWeather bedrockOrganicOrganic
Environmental ChangesEnvironmental ChangesCompactionCompactionTemperatureTemperatureWaterWaterWindWindVegetationVegetation
Landscape PositionLandscape Position
ErosionErosionTransferTransferWetnessWetness
Soil Profile and HorizonsSoil Profile and Horizons
Understanding these Understanding these ideas will help in ideas will help in create a better create a better system designsystem design
Unsaturated SoilUnsaturated SoilSoil color is important in identifying the Soil color is important in identifying the Aerobic state of the soilAerobic state of the soilBright colors are Bright colors are well aerated or drainedwell aerated or drainedGrays Grays ((redoxredox features)features)are wetare wet
Color & SaturationColor & Saturation
Well Drained Moderately Well Drained
Poorly Drained
Munsell ColorbookMunsell Colorbook
Other visual keys Other visual keys determination to saturated determination to saturated
conditionsconditions
TextureTextureCoarser soils:Coarser soils:
Faster movementFaster movementLess surface areaLess surface areaLess removal sitesLess removal sites
Finer soils:Finer soils:Slower movementSlower movementMore surface areaMore surface areaMore removal sitesMore removal sites
TextureTexture
How big a system should I installHow big a system should I installSandSand-------- Loam Loam -------- ClayClay
StructureStructure
Soil Structure impactsSoil Structure impacts
# PoresWater
MovementMany High
Few Low
Major TypesGranularPrismaticBlockyPlatyMassive
Granular Soil StructureGranular Soil Structure
Photo by M. Stolt
Columnar Soil StructureColumnar Soil Structure
Photos by G. Loomis
Sandy Textured Structureless –
Single Grain Soil
Sandy Textured Structureless –
Single Grain Soil
High potential for poor wastewater treatment High potential for poor wastewater treatment
Soil Structure
Easily altered or destroyedDynamic, changed by:
• Moisture content• Chemistry of soil water• Biological activity• Construction/ management practices• Clay mineralogy
What happens when you put What happens when you put wastewater in the soil?wastewater in the soil?
BiomatBiomat formsformsCreating Creating unsaturated flowunsaturated flow
This means:This means:More contact with the soil particlesMore contact with the soil particlesAerobic organisms treat the wastewaterAerobic organisms treat the wastewater
A cross section of BiomatA cross section of Biomat
Biomat Biomat
How do pathogens get How do pathogens get treated?treated?
They are physically filteredThey are physically filteredThey are attached to the soil particlesThey are attached to the soil particlesThey die due to environmental conditionsThey die due to environmental conditionsThey are attacked by soil organismsThey are attacked by soil organisms
Given time the soil is a very effective Given time the soil is a very effective treatment mediumtreatment medium
Pathogen retentionPathogen retention
Pathogen removalPathogen removal
What Nutrients?What Nutrients?
Nutrients of concern Nutrients of concern Nitrogen & PhosphorusNitrogen & PhosphorusN N -- groundwater troublegroundwater troubleP P -- Surface water troubleSurface water trouble
Points of impactPoints of impact
PhosphorusPhosphorus
P complexes with other minerals in the soil P complexes with other minerals in the soil The complexes are insolubleThe complexes are insolubleP will move if the soil moves (erosion)P will move if the soil moves (erosion)Some of the P is used by the vegetationSome of the P is used by the vegetationSoils have finite capacities to sorbs Soils have finite capacities to sorbs PhosphorusPhosphorus
Very slowly solubleCa-P minerals
P retained by clay& iron & aluminum oxides
Soil solut ion
People
Animals
Fert ilizers
Readily solubleCa-P minerals
P occluded in iron& aluminum minerals
extremely insoluble
Loss in runoff
Loss on erodedsoil particles
Soil organisms biomass
P in active soil organic matter
P in slow & passivesoil organic mat ter
Plant residues,manure,biosolids
Root uptake
Desorption
Adsorption
Immobilization
Minerialization
Inorganic forms of P
Organic forms of P
Dominantforms of Pin high pH
&calcareous soils
Phosphorus Removal in Phosphorus Removal in Conventional Septic SystemsConventional Septic Systems
• Phosphorus adsorbed to iron, aluminum, calcium, and magnesium in soils
• P removal depends on soil surface area
• Sands have less surface area than finersoil particles
• Wet soils have potentially less iron in them, so less P removal potential
Nitrogen Removal in Conventional Septic System
Less than 15 percent removal in septic tank
Septic tank effluent composed of organic-Nand ammonium-N
Conversion to nitrate-N in drainfield
Nitrate-N very mobile
10 ppm EPA nitrate-N drinking water standard
NitrogenNitrogen
N starts as AmmoniaN starts as AmmoniaIn an aerobic environment it is transformed In an aerobic environment it is transformed to Nitrateto NitrateNitrate moves with the water unless Nitrate moves with the water unless additional treatment steps are takenadditional treatment steps are taken
NH4+
NO3-O2
N Cycle in Septic SystemsN Cycle in Septic Systems
Nitrification and SorptionNitrification and Sorption
Denitrification ?Denitrification ?
Min
erM
iner
ImmobilizationImmobilization
aliza
tion
aliza
tion
Nitrogen Removal in Nitrogen Removal in Conventional Septic SystemConventional Septic System
Less than 15 percent removal in septic tankLess than 15 percent removal in septic tank
Septic tank effluent composed of organicSeptic tank effluent composed of organic--NNand ammoniumand ammonium--N N
Conversion to nitrateConversion to nitrate--N in drainfield N in drainfield
NitrateNitrate--N very mobile and conservative N very mobile and conservative
10 ppm EPA nitrate10 ppm EPA nitrate--N drinking water standardN drinking water standard
VOC and HCsVOC and HCs
SourceSourcecleaning fluids, solventscleaning fluids, solvents
Variable amountsVariable amounts
VOC and HCs: ConcernsVOC and HCs: Concerns
CarcinogensCarcinogensToxinsToxins
VOC and HCs: ReactionsVOC and HCs: Reactions
SorptionSorptionMicrobial transformationMicrobial transformationVolatilizationVolatilization
Additives have been Additives have been shown to assist in a shown to assist in a
system stressed by VOCs system stressed by VOCs and HCsand HCs
Pollutant attenuation potentialPollutant attenuation potential
+ = promotes attenuation- = discourages attenuation
Pollutant
Phosphorus
Nitrogen
Pathogens
AerobicSoils
+
-
+
W etSoils
-
+
-
SandySoils
-
-
-
Non- SandySoils
+
+
+
Treatment ChallengesTreatment Challenges
Shallow bedrockShallow bedrockKarstKarst bedrockbedrockSaturated soilsSaturated soilsSlowly permeable soilsSlowly permeable soilsRapidly permeable soilsRapidly permeable soilsFill soilsFill soilsSeasonally used systemsSeasonally used systems
N Cycle in Septic SystemsN Cycle in Septic Systems
Nitrification and SorptionNitrification and Sorption
Denitrification ?Denitrification ?
Min
erM
iner
ImmobilizationImmobilization
aliza
tion
aliza
tion
Nitrogen Removal in Nitrogen Removal in Conventional Septic SystemConventional Septic System
Less than 15 percent removal in septic tankLess than 15 percent removal in septic tank
Septic tank effluent composed of organicSeptic tank effluent composed of organic--NNand ammoniumand ammonium--N N
Conversion to nitrateConversion to nitrate--N in drainfield N in drainfield
NitrateNitrate--N very mobile and conservative N very mobile and conservative
10 ppm EPA nitrate10 ppm EPA nitrate--N drinking water standardN drinking water standard
Soils are a Soils are a very effectivevery effectivetreatment media & treatment media &
TreatmentTreatment is the goalis the goal
Photo: Photo: Inspection Inspection
neededneeded