Advanced Treatment Systems-Secondary Treatment Systems for the Onsite Industry

8/14/2019 Advanced Treatment Systems-Secondary Treatment Systems for the Onsite Industry

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Secondary TreatmentSecondary TreatmentSystems for the OnsiteSystems for the Onsite

IndustryIndustry



Conventional Septic Tank SystemsConventional Septic Tank Systemscan be Problematic, Particularly incan be Problematic, Particularly in

Areas exhibiting:Areas exhibiting:

High Ground Water TableHigh Ground Water TablePoor SoilsPoor Soils

Increasing Population DensityIncreasing Population Density



Conventional OnsiteConventional Onsite



Secondary Treatment SystemsSecondary Treatment Systems

are used…are used…

To Protect Public HealthTo Protect Public HealthTo Protect the environmentTo Protect the environmentWhen soils cannot provideWhen soils cannot provideadequate treatment or disposaladequate treatment or disposal



Attached-Growth SystemsAttached-Growth Systems

Most are aerobic (ATU=somewhat of a misnomer)Most are aerobic (ATU=somewhat of a misnomer)Filter bed provides material with high surface area perFilter bed provides material with high surface area pervolume: easily passes water andvolume: easily passes water and oxygenoxy genMicrobial ecosystem establishes itself on the mediaMicrobial ecosystem establishes itself on the mediasurface (a.k.a. “fixed film”)surface (a.k.a. “fixed film”)Microflora include bacteria, protozoa (amoeba, etc.),Microflora include bacteria, protozoa (amoeba, etc.),rotifers, fungi, and other organismsrotifers, fungi, and other organismsThese established micro-communities consume andThese established micro-communities consume and

digest much of the pathogens and organic constituentsdigest much of the pathogens and organic constituentsin the wastewaterin the wastewater



The Attached-Growth ProcessThe Attached-Growth Process



Attached-Growth Systems:Attached-Growth Systems:Many Types of Natural and SyntheticMany Types of Natural and Synthetic

Media!Media!Natural MediaNatural Media• Sand/GravelSand/Gravel• ShaleShale

• LimestoneLimestone• Activated CarbonActivated Carbon• Peat or Peat FiberPeat or Peat Fiber• Coconut Fiber (Coir)Coconut Fiber (Coir)

Synthetic MediaSynthetic Media• Open Cell FoamOpen Cell Foam• Geo-textile FabricGeo-textile Fabric

• Crushed GlassCrushed Glass• Tire ChipsTire Chips• Hard PlasticHard Plastic



Sand FiltersSand Filters

Single-pass or RecirculatingSingle-pass or RecirculatingWastewater distributed evenly across sand bedWastewater distributed evenly across sand bedDosing (loading) importantDosing (loading) important

Size and quality of sand key to sand filter functionSize and quality of sand key to sand filter functionSand or gravel particles are screened to meetSand or gravel particles are screened to meetspecific grain-size specificationsspecific grain-size specificationsSpecifications are designed to provide surfaceSpecifications are designed to provide surface

area for bacterial attachment, with adequate voidarea for bacterial attachment, with adequate voidspace for airflow to aerobic organisms and largespace for airflow to aerobic organisms and largevoids to prevent cloggingvoids to prevent clogging



Geo-textile FiltersGeo-textile Filters

RecirculatingRecirculatingModular….installed as a unit (450 gpd, etc.)Modular….installed as a unit (450 gpd, etc.)…”plug and play” …”plug and play” Increased surface area and large void volume perIncreased surface area and large void volume perunit bulk volume of material while maintainingunit bulk volume of material while maintaininghigh water-holding capacityhigh water-holding capacityIncreased surface area-thus filter size can beIncreased surface area-thus filter size can besmaller for a given wastewater flowsmaller for a given wastewater flow

Aerobic conditions maintained due to largeAerobic conditions maintained due to largevolume of pore space through which air can flowvolume of pore space through which air can floweven while material is wettedeven while material is wetted



Peat Bio-FiltersPeat Bio-FiltersTypically single-passTypically single-passModular, “plug and play” Modular, “plug and play” Can be pressurized or gravity fedCan be pressurized or gravity fedNatural media-Canada, Ireland, and northern EuropeNatural media-Canada, Ireland, and northern EuropeHigh surface area and high void volumeHigh surface area and high void volumeMicroflora range from bacteria to nematodesMicroflora range from bacteria to nematodesTreated effluent often tea colored due to contact withTreated effluent often tea colored due to contact withorganic humus in the filterorganic humus in the filter

Peat fiber deteriorates-must be periodlically replaced (8-Peat fiber deteriorates-must be periodlically replaced (8-20 years.20 years.



Peat Bio-FiltersPeat Bio-Filters



Open Cell Foam SystemsOpen Cell Foam Systems

Single Pass or RecirculatingSingle Pass or RecirculatingModular-”plug and play” Modular-”plug and play” Utilizes polyurethane foam material in 2” cubesUtilizes polyurethane foam material in 2” cubesCombines large surface area for microbial attachmentCombines large surface area for microbial attachmentand long retention times with high void volumes andand long retention times with high void volumes andseparate paths for wastewater and air=loading ratesseparate paths for wastewater and air=loading ratesup to 10X greater than sandup to 10X greater than sandHelical spay nozzles for uniform distributionHelical spay nozzles for uniform distribution

Like other AGS’s-media must be periodically replacedLike other AGS’s-media must be periodically replaced



Open Cell FoamOpen Cell Foam



Suspended-Growth Treatment SystemsSuspended-Growth Treatment Systems(a.k.a. Aerobic Treatment Units)(a.k.a. Aerobic Treatment Units)

Think fish aqaurium! Microbes in these systems much theThink fish aqaurium! Microbes in these systems much thesame as in attached-growth systemssame as in attached-growth systemsEssentially miniature wastewater treatment plants (a.k.a.Essentially miniature wastewater treatment plants (a.k.a.activated sludge)activated sludge)

Often come as packages (trash trap, aeration chamber, andOften come as packages (trash trap, aeration chamber, andpump chamber in one unit) for residential applications.pump chamber in one unit) for residential applications.Commercial units often have additional chambers thatCommercial units often have additional chambers thatpromote removal of nutrients, suspended solids, andpromote removal of nutrients, suspended solids, andpathogens from effluentpathogens from effluent

Some units utilize attached-growth processes along withSome units utilize attached-growth processes along withsuspended-growth processes (ex: rotating biologicalsuspended-growth processes (ex: rotating biologicalcontactor, Biolclere unit, Delta Biopod, Multi-flo Unit).contactor, Biolclere unit, Delta Biopod, Multi-flo Unit).



Suspended-Growth TreatmentSuspended-Growth TreatmentProcessProcess

Primary treatment is provided by a “trash tank” or septic tankPrimary treatment is provided by a “trash tank” or septic tankthat is sized for shorter retention time than a standard STthat is sized for shorter retention time than a standard STWastewater enters the aeration chamber and is mixed withWastewater enters the aeration chamber and is mixed withdissolved oxygen (from an air compressor, etc..) anddissolved oxygen (from an air compressor, etc..) and

suspended susp ended or attached microbes, or bothor attached microbes, or bothMicrobes convert organic compounds into energy, new cells, andMicrobes convert organic compounds into energy, new cells, andresidual matterresidual matterTreated water moves into a clarifier, where remaining solids areTreated water moves into a clarifier, where remaining solids areseparated and returned to the aeration compartment for furtherseparated and returned to the aeration compartment for furthertreatmenttreatment

Treated wastewater flows out of the clarifier for in-groundTreated wastewater flows out of the clarifier for in-grounddisposaldisposal



Suspended-Growth Treatment Processes:Suspended-Growth Treatment Processes:Things to Consider Things to Consider

Organic and hydraulic loading is important!Organic and hydraulic loading is important!If there is more “food” than microbes, effluentIf there is more “food” than microbes, effluentquality will be poorquality will be poor

If there are more microbes than food, effluentIf there are more microbes than food, effluentquality will be highquality will be highHigh hydraulic loading (ex: from washingHigh hydraulic loading (ex: from washingmachines=low in soluble BOD) can cause “wash-machines=low in soluble BOD) can cause “wash-out” of microbesout” of microbesNo food (i.e. lots of H2O)= microbes cannibalizeNo food (i.e. lots of H2O)= microbes cannibalizethemselvesthemselvesPopulation of microbes is dynamic in SGTS’sPopulation of microbes is dynamic in SGTS’s



Suspended-Growth Treatment Processes:Suspended-Growth Treatment Processes:Things to Consider Things to Consider

All of these factors are important whenAll of these factors are important whenusing SGTS’s in decentralized applicationsusing SGTS’s in decentralized applicationsAGTS’s are easier to “phase” in (ex: whenAGTS’s are easier to “phase” in (ex: whenyou have only 4 homes in what willyou have only 4 homes in what willultimately be a 100 home subdivision)ultimately be a 100 home subdivision)Therefore, design is critical with SGTS’s!Therefore, design is critical with SGTS’s!



Suspended-Growth Treatment Processes:Suspended-Growth Treatment Processes:



Suspended Growth with Fixed FilmSuspended Growth with Fixed Film



Other Other

Secondary Treatment SystemsSecondary Treatment Systems



Constructed WetlandsConstructed Wetlands

“ “ Man-made” ecosystems designed toMan-made” ecosystems designed tooptimize natural wetlands fuctions,optimize natural wetlands fuctions,particularly those associated withparticularly those associated withwastewater treatment.wastewater treatment.



Constructed Wetland DesignConstructed Wetland Design

Treatment CellTreatment Cell• based on treatment (2.5 days HRT)based on treatment (2.5 days HRT)-- lined (butyl rubber, 45 mil)-- lined (butyl rubber, 45 mil)

Disposal Cell

•Size based on standard soil loading rates

-- 18-inch separation from restriction-- no liner-- 8 to 12 inches of #57 gravel



Lined cell 1

Unlined Cell 2

Advanced Treatment Systems-Secondary Treatment Systems for the Onsite Industry

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