Design Considerations for Design Considerations for High Strength Wastewater High Strength Wastewater Bruce Lesikar Bruce Lesikar Texas AgriLife Extension Service Texas AgriLife Extension Service Presentation Overview Presentation Overview ¾ Wastewater characteristics Wastewater characteristics ¾ Managing common processes of Managing common processes of flocculation, bulking and sloughing flocculation, bulking and sloughing ¾ Building treatment trains for a site specific Building treatment trains for a site specific facility incorporating sustainability & facility incorporating sustainability & recovery features recovery features ¾ How to work through design/loading How to work through design/loading challenges challenges Wastewater Loading Wastewater Loading ¾ Wastewater quantity Wastewater quantity z Hydraulic loading Hydraulic loading z Residential 100 Residential 100- 150 150 gallons per bedroom gallons per bedroom ¾ Wastewater quality Wastewater quality z Organic loading Organic loading z Residential < 300 Residential < 300 mg/L BOD mg/L BOD 5 z Oxygen demand Oxygen demand ¾ Residential and Residential and commercial facilities commercial facilities Wastewater Quantity Wastewater Quantity Types of Flow Types of Flow ¾ Residential Residential ¾ Commercial Commercial ¾ Design Design ¾ Daily Flow Daily Flow ¾ Average Average ¾ Surge Surge ¾ Peak Peak ¾ Seasonal Seasonal
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Design Considerations for Design Considerations for High Strength WastewaterHigh Strength Wastewater
Bruce LesikarBruce LesikarTexas AgriLife Extension ServiceTexas AgriLife Extension Service
Presentation OverviewPresentation Overview
Wastewater characteristicsWastewater characteristicsManaging common processes of Managing common processes of flocculation, bulking and sloughing flocculation, bulking and sloughing Building treatment trains for a site specific Building treatment trains for a site specific facility incorporating sustainability & facility incorporating sustainability & recovery featuresrecovery featuresHow to work through design/loading How to work through design/loading challengeschallenges
Single family dwelling (one or two bedrooms) - less than 1,500 square feet.
225
180
Single family dwelling (three bedrooms) - less than 2,500 square feet. 300 240 Single family dwelling (four bedrooms) - less than 3,500 square feet. 375 300 Single family dwelling (five bedrooms) - less than 4,500 square feet. 450 360 Single family dwelling (six bedrooms) - less than 5,500 square feet. 525 420 Greater than 5,500 square feet, each additional 1,500 square feet or increment thereof.
75 60
Commercial WastewaterCommercial Wastewater
StrengthStrengthUsually greater Usually greater than residentialthan residentialOperation basedOperation based•• Food Food
2) Effluent from a septic tank or other 2) Effluent from a septic tank or other pretreatment component that has:pretreatment component that has:
BODBOD55 >> 140 mg/L, 140 mg/L, and/or TSS and/or TSS >> 60 mg/L, 60 mg/L, and/or (FOG) and/or (FOG) >> 25 mg/L and is applied to an 25 mg/L and is applied to an infiltrative surface.infiltrative surface.
Mass Loading CalculationMass Loading CalculationResidential strengthResidential strength
Calculate mass loading to a systemCalculate mass loading to a systemConcentration in wastewaterConcentration in wastewaterVolume of wastewaterVolume of wastewater
Mass (lb) = 140 (mg/L) x 200 (gpd) x 0.00000834Mass (lb) = 140 (mg/L) x 200 (gpd) x 0.00000834
Mass (lb) = 0.23 lbs per dayMass (lb) = 0.23 lbs per day
Commercial strengthCommercial strengthMass (lb) = C (mg/L) x Q (gpd) x 0.00000834Mass (lb) = C (mg/L) x Q (gpd) x 0.00000834Mass (lb) = 600 (mg/L) x 500 (gpd) x 0.00000834Mass (lb) = 600 (mg/L) x 500 (gpd) x 0.00000834
Mass (lb) = 2.5 lbs per dayMass (lb) = 2.5 lbs per day
Mass LoadingMass LoadingCalculate mass loading to a systemCalculate mass loading to a system
Number of people (capita)Number of people (capita)Organic loading rateOrganic loading rate
Mass (lb) = P (# of people) x OMass (lb) = P (# of people) x OLL (lbs per capita(lbs per capita-- day)day)Mass (lb) = 5 (# of people) x 0.17Mass (lb) = 5 (# of people) x 0.17 (lbs per capita(lbs per capita-- day)day)
Mass (lb) = 0.85 lbs per dayMass (lb) = 0.85 lbs per day
Where:Where:AAOLOL =Infiltrative surface area (For high strength =Infiltrative surface area (For high strength wastewater based on organic loading) wastewater based on organic loading) –– ftft22BODBODEffEff = Facility BOD = Facility BOD –– mg/Lmg/LQ = Flow Q = Flow -- gpdgpdRa = hydraulic acceptance rate Ra = hydraulic acceptance rate -- gpd/ ftgpd/ ft22
0.77 = Safety factor0.77 = Safety factor
Note: This equation uses an example assumed value for septic tanNote: This equation uses an example assumed value for septic tank k effluent of 140. If the local code Ra values are based on an effluent of 140. If the local code Ra values are based on an assumed BODassumed BOD55 other than 140 mg/L, use that value insteadother than 140 mg/L, use that value instead..
Infiltrative surface area for high Infiltrative surface area for high strength wastewaterstrength wastewater
Example Cont.Example Cont.Area based on hydraulic loading rate:Area based on hydraulic loading rate:
Area = Q /RArea = Q /Raa
Area = 500 gallons per day / 0.25 gallons Area = 500 gallons per day / 0.25 gallons per ftper ft22--daydayArea = Area = 2000 ft2000 ft22
Infiltrative surface area for high Infiltrative surface area for high strength wastewaterstrength wastewater
Example Cont.Example Cont.Area based on organic loading rate (Method 1):Area based on organic loading rate (Method 1):
Organic loading rate:Organic loading rate:AAOLOL =[(BOD=[(BODEff Eff / 140) x (Q / Ra)]/0.77/ 140) x (Q / Ra)]/0.77AAOLOL = [(300 mg/L / 140) x (500 gallons/day / 0.25 = [(300 mg/L / 140) x (500 gallons/day / 0.25
gallons/ftgallons/ft22--day)]/0.77 day)]/0.77 AAOLOL = (2.14 x 2000 ft= (2.14 x 2000 ft22)/0.77)/0.77AAOLOL = 6114 ft= 6114 ft22
Required area: Required area: 5558 ft5558 ft2*2*
*more than 2.5 times as large as calculated with hydraulic *more than 2.5 times as large as calculated with hydraulic loadingloading
QuestionQuestion
What would the life What would the life expectancy be for a expectancy be for a
system operating at both system operating at both maximum flows and maximum flows and
BulkingBulkingWhat is bulking?What is bulking?What is the impact on a system What is the impact on a system
that has bulked?that has bulked?Reduction in the solids contained in a Reduction in the solids contained in a
treatment tank treatment tank Can resettle Can resettle
Naturally occurring bulkingNaturally occurring bulkingBlack in colorBlack in color Naturally occurring bulkingNaturally occurring bulking
Emulsification Emulsification What is emulsification?What is emulsification?
Discrete particles in suspensionDiscrete particles in suspensionLoss of stratificationLoss of stratification
CausesCausesTemperatureTemperature
•• Example: FOG emulsified by high temperatureExample: FOG emulsified by high temperatureChemical EmulsificationChemical Emulsification
•• Brownish or yellow in colorBrownish or yellow in color•• Fabric softeners and wax releasing agentsFabric softeners and wax releasing agents
EffectsEffectsHomogeneous mass of solids that is not contained in Homogeneous mass of solids that is not contained in the septic tankthe septic tankWill not settled back outWill not settled back out
Healthy septic tank
• Scum and sludge normal• Some carryover to second compartment• Limited flocculent in clear zone
Chemical emulsification near completion
• Homogeneous mixture• No clear zone• Solids carryover definite
Solids carryover from this chemically Solids carryover from this chemically upset systemupset system
Statistics –• Estimated 150 gpd• Family of 2 adults• 1000 gallon septic tank• System less than 3
years old• Excessive liquid fabric softener was used
• Other chemicals likely
After drying, this remaining material was fibrous in nature showing a definite texture.
Chemical EmulsificationChemical Emulsification Recoverable TrenchRecoverable Trench
Facilitate sludge Facilitate sludge removalremovalClean out pipe at Clean out pipe at bottom of trenchbottom of trenchClean out & Clean out & Inspection port at Inspection port at ends connected to the ends connected to the clean out pipe clean out pipe
SloughingSloughingWhat is sloughing?What is sloughing?
Loss of accumulated organic material / biological growth Loss of accumulated organic material / biological growth from surfacesfrom surfaces
Where does it occur?Where does it occur?Media, trickling filters, pipe interiorsMedia, trickling filters, pipe interiors
When does sloughing occur?When does sloughing occur?When gas develops between organic /biological growth When gas develops between organic /biological growth and surface it is attached toand surface it is attached toGas causes solids to loose grip on surface and solids Gas causes solids to loose grip on surface and solids become unattached and mobile.become unattached and mobile.Scouring velocity passing through a pipe.Scouring velocity passing through a pipe.
What impact does sloughing have on a system?What impact does sloughing have on a system?Naturally occurringNaturally occurringAdvanced treatment system designs usually account for Advanced treatment system designs usually account for thisthisSludge return pumps in trickling filtersSludge return pumps in trickling filtersLargely responsible for orifice cloggingLargely responsible for orifice clogging
ATU Working Properly ATU Working Properly –– sloughing should sloughing should happen according to designhappen according to design
Outletend
Sloughing in a pipe carrying Sloughing in a pipe carrying sewage/effluentsewage/effluent
FLOCCULENTFLOCCULENTWhat is flocculent?What is flocculent?
Neutrally buoyant organic material Neutrally buoyant organic material aggregating togetheraggregating togetherOften composed of fibrous materialsOften composed of fibrous materialsCan be sparse or denseCan be sparse or dense
Where is flocculent present?Where is flocculent present?Primary, recirculation, processing, Primary, recirculation, processing, and clarifier tanks or compartmentsand clarifier tanks or compartments
Heavy flocculent
Treatment TrainsTreatment Trains““Treatment trainTreatment train”” refers to the series of refers to the series of components functioning together in a components functioning together in a wastewater treatment system to remove wastewater treatment system to remove contaminants from wastewater. contaminants from wastewater. Order and specific component selection Order and specific component selection importantimportantMust understand:Must understand:
How each component operatesHow each component operatesHow the train functions as a wholeHow the train functions as a wholeThe limitations of each component within the The limitations of each component within the traintrainThe treatment processes occurringThe treatment processes occurring
Flow Equalization TanksFlow Equalization Tanks
Makes the flow introduced to the treatment Makes the flow introduced to the treatment system more consistent. system more consistent. Flow equalization is important ifFlow equalization is important if
The average flow is The average flow is ≥≥ 70% of the design 70% of the design capacitycapacityWater use habits or facility operations are Water use habits or facility operations are variablevariable-- Example church only open on Sun.Example church only open on Sun.
Frequent peaks exceed system capacityFrequent peaks exceed system capacity•• Wash day: cleaning serviceWash day: cleaning service
Flow Equalization/Surge TankFlow Equalization/Surge Tank
Moderates flow from Moderates flow from facilityfacilityDetermine peak/surge Determine peak/surge to be moderatedto be moderated
DailyDailyWeeklyWeekly
Improves treatment Improves treatment by ALL by ALL DOWNSTREAM DOWNSTREAM componentscomponentsUp stream sized for Up stream sized for peakpeak
TimeTime--Dosed / Pumping SystemsDosed / Pumping Systems Diversity of Flows from a Supermarket
Initial tank for each Initial tank for each facilityfacilityRental contract tied to Rental contract tied to wastewater quality & wastewater quality & quantityquantity
Data contained in reportsData contained in reportsMechanism in place to Mechanism in place to ensure they are occurringensure they are occurringLack of O&M leads to Lack of O&M leads to malfunction malfunction
O&M requirements O&M requirements MUSTMUST be included in plansbe included in plans
Accessibility for MaintenanceAccessibility for Maintenance
Manufacturers Manufacturers guidanceguidanceRisers to surfaceRisers to surfaceAppropriate size Appropriate size openings openings Appropriate depthAppropriate depthConnections to Connections to componentscomponents
All Systems NEED O&MAll Systems NEED O&MO&M Frequency is a function of:O&M Frequency is a function of:
•• Risk associated with soil typeRisk associated with soil type•• Dispersal method (surface requires more O&M because of Dispersal method (surface requires more O&M because of
greater risk) greater risk)
Wastewater loading to the environmentWastewater loading to the environment•• Watershed loading rate (subdivision on small lotsWatershed loading rate (subdivision on small lots-- greater greater
loadload——higher risk)higher risk)
Technology Technology –– system complexitysystem complexity•• Manufacturer recommendationsManufacturer recommendations
Wastewater source or useWastewater source or use•• Operating at >70% of design requires more O&MOperating at >70% of design requires more O&M
Monitoring FrequencyMonitoring FrequencyWho sets the monitoring Who sets the monitoring frequency?frequency?State requirements!State requirements!Local regulators! Local regulators! What factors?What factors?
Residential systemsResidential systemsCommercial systemsCommercial systemsSite conditionsSite conditionsWastewater loading to the Wastewater loading to the areaareaHuman and Environmental Human and Environmental risk factorsrisk factorsTechnology usedTechnology used
Operational DataOperational DataAll commercial systems All commercial systems must record flowmust record flowFlow recordingFlow recording
Flow meter Flow meter –– high quality high quality effluenteffluentElapse time meterElapse time meterCycle counterCycle counterPotable water meterPotable water meter
Amber alarm Amber alarm Add to flow equalization Add to flow equalization tank to water level in tanktank to water level in tank
Communication with Communication with ownerowner
System UpgradesSystem UpgradesA good business will growA good business will growHow will we deal with the How will we deal with the extra wastewater?extra wastewater?Centralized sewers have Centralized sewers have a set/accepted schedule a set/accepted schedule Performance based Performance based systems can be required systems can be required to upgrade treatment to upgrade treatment system system –– tied to food tied to food permitpermitFlexibility is key to future Flexibility is key to future system upgradessystem upgradesWaste minimizationWaste minimization
SummarySummary
Wastewater characteristicsWastewater characteristicsManaging common processes of Managing common processes of flocculation, bulking and sloughing flocculation, bulking and sloughing Building treatment trains for a site specific Building treatment trains for a site specific facility incorporating sustainability & facility incorporating sustainability & recovery featuresrecovery featuresOwner responsibility and good data are Owner responsibility and good data are essential to working through essential to working through design/loading challengesdesign/loading challenges