is this going to stink?
TRANSCRIPT
OverviewProject background
Bench scale pilot / bioreactor setup
Results to date
Continued Efforts
BackgroundLocated in La Crosse CountyRapidly GrowingMedian Resident Age
Holmen: 34 yearsWisconsin Avg: 44 years
Estimated 2011 MHIHolmen: $59,326Wisconsin Average: $50,395
2013 Estimate: 9,3182033 Estimate: 12,806
BackgroundAverage Influent Wastewater
Characteristics:0.50 MGD average daily flow330 mg/L BOD323 mg/L TSS38 mg/L NH350 mg/L SO4
The Village must have some significant high strength industrial dischargers, right?
BackgroundWrong!
Very Little Infiltration and InflowTight sewers (a lot of new construction)Sandy soilsNot many areas of high groundwater
Facility PlanningWWTF is nearing organic capacityLots of growthFuture P limit of 0.075 mg/L
Compliance OptionsOxidation Ditch A/S with Tertiary FiltrationMembrane BioReactorsRegional treatment at La Crosse WWTF (via
Onalaska)
Facility PlanningTreatment
Capital: $15.8 M Annual O&M: $243,000
RegionalizationCapital: $9.3 MAnnual O&M: $162,000
Regionalization was recommended
Facility PlanningRegionalization Assumptions
New regional pump station at location of WWTF
4.8 Miles of 16” Forcemain to OnalaskaChemical addition at the regional pump station
to control odors (hydrogen sulfide)Intermediate chemical feed building ~2 miles
away included in cost, but hopefully not necessary
Goal: feed chemical at regional pump station only
Facility PlanningRegionalization Assumptions, Continued
Estimated aqueous hydrogen sulfide generation of 16.8 mg/L or 70.5 lbs/day at startup flow (summer temps)
Calcium Nitrate dosage of 1.3 gallons per pound of sulfide
Roughly 33,000 gallons of calcium nitrate @ $4.25/gallon
Estimated annual chemical cost of ~ $140,000
Facility PlanningHydrogen Sulfide (H2S) forms when:
Conditions are anaerobic (no free oxygen)Food (BOD) is availableSulfate Reducing Bacteria (SRBs) are present
Rotten egg smell
Reported Odor Thresholds VaryIn Air: 0.005 – 0.3 ppm (Ruth 1986, Guidotti
1994) In Water: 0.000029 ppm (O’Neil 2001)
Facility PlanningShould we worry about odors in this case?
Odors are common in forcemains, especially when:Strong wastewater (Holmen BOD = 330 mg/L)Plenty of Sulfates (Holmen SO4 = 50 mg/L)Significant forcemain hydraulic retention times
Holmen HRT = 13 hours at startup flow Holmen HRT = 8 hours at design flow
Plan for odor control
Facility PlanningConditions of Regionalization Recommendation:
Condition 1Equitable agreements with Onalaska and La
Crosse would be reached
Condition 2Control of odors at the discharge in Onalaska
would be feasible and cost effective
Pilot TestGoal 1: Construct bench-scale bioreactors to
mimic forcemain conditionsGoal 2: Document and assess sulfide
generation potential of Holmen’s wastewaterGoal 3: Treat reactors with calcium nitrate
under and document inhibition of sulfide generation
Goal 4: Determine necessary dosage and compare projected O&M costs to facility plan estimates
Pilot Test BioReactors
4” Clear PVCPressure GaugesFill & Draw PortsBall ValvesRack
Pilot Test – Reactor Conditioning
Condition Reactors to establish anaerobic biofilm
Bioreactors were filled and emptied every 24 hours
Biofilm was visible after roughly 2 weeksH2S Odor was noticeable when emptying
reactors
Pilot Test – Reactor Conditioning
Influent and Effluent Sampling to Confirm Biological ActivitySulfate (influent should be higher than
effluent)Sulfide (influent should be lower than effluent)sBOD (influent should be higher than effluent)
H2S Odor was noticeable when emptying reactors
Pilot Testing – Sample Analysis
Certified lab was used for sulfide and sulfate during bioreactor conditioningSignificant expenseLong turnaround time = disadvantage
Colorimetric tests to measure dissolved sulfideUse for routine monitoring of bioreactor
influent & effluent; instantaneousSend some samples to certified lab to verifySave costs
Pilot Testing – Products
Hawkins HSX AquaHawk (Calcium Nitrate)Provided product as a courtesy
Other manufacturers’ products would be tested later as time permitted Bioxide (Siemens/Evoqua)CS41 (Hydrite)Other chemicals (Ferric Chloride? H2O2 ? )
Pilot Testing – Original PlanWeek 1
Feed R1 at 3x theoretical dosageFeed R2 at 2x theoretical dosageUse 24 hour HRT for simplicity
Fill & Draw (no dose) over the weekendWeek 2
Feed R1 at 1x theoretical dosageFeed R2 at 0.5x theoretical dosage
Document reduction in sulfide generation
Pilot Testing – Initial Results Large discrepancy between certified lab and
colorimetric test resultsColorimetric typically 5% - 20% of certified lab
resultBelieved to be interference with TSS
Sulfide generation actually increased Over fed the SRBs with nitrateArtificially created a population boomTests were too short to re-achieve equilibrium
Pilot Testing – Revised PlanRe-establish natural steady-state for biofilm
Fill & Draw reactors daily; no calcium nitrate addition
Try a new colorimetric test to see if interferences are eliminatedHACH Model HS-C Establish consistent results Then start splitting samples with certified lab
Wait for extreme cold weather to end…Keep busy by thawing some frozen laterals…
Pilot Testing – March 2014
Operate at HRTs of ~ 6-8 hours and ~ 15-17 hours
Operate one reactor as a control throughout testsNo calcium nitrate additionOperate the other reactor as the test caseBegin dosing calcium nitrate one week in advance of
trying to quantify resultsEstablish steady state of biomass and acclimate the
SRBsWeek 1: Dose at 1.5 x theoreticalWeek 2: Dose at 2.0 x theoretical
Pilot Testing – March 2014
Results are promisingTrends are visibleShorter HRTs result in lower sulfide levelsAmbient temperature influences
Cold influent takes a while to ‘warm up’ in the reactor
Likely delays the conversion of sulfate by SRBs in the biofilm
Pilot Testing – March 2014
Further Work
Continue pilot testingLong-term data should increase overall
consistencyCharacterize temperature impacts
Summertime operation will be criticalCompare modeled vs actual sulfide
production in untreated reactorTo date, observed sulfide concentrations are
much lower than modeledBegin splitting samples with certified lab