Primary Clarifier Odor Control Replacing Nitrates with D.O. Kevin Jacobs, P.E. ECO Oxygen Technologies

Primary Clarifier Odor Control Replacing Nitrates with D.O. Kevin Jacobs, P.E. ECO Oxygen Technologies

Presentation Outline Primary Clarifier Odor Challenges Odor Treatment Options Case Study Anson-Madison Sanitary District Conclusions

Primary Clarifier Odor Challenges

Quiescent by Design Flow is slowed to allow for solids settling Provides for little to no re-aeration

Major Odor Source The effluent weirs from a primary clarifier are a major source of odor Odor Release H2S Flux H2S Flux Sludge Blanket

Root Cause of Odor Electron Acceptors (Order of Preference): Oxygen Nitrate Sulfate U.S. EPA (1985) Odor and Corrosion Control in Sanitary Sewerage Systems and Treatment Plants Design Manual; EPA/625/1-85/018; Cincinnati, Ohio.

Root Cause of Odor Under Anaerobic Conditions: Bacteria consumes BOD Strips Sulfate of O2 Converts Sulfate to Sulfide SO4 & BOD H2S Sulfide No D.O.

Factors That Affect H 2 S Formation Limited solubility of oxygen in water High BOD Favorable ph levels Warm temperatures Unlimited supply of sulfates Long retention times

Odor Leads to Corrosion 100% Rate of Corrosion 50% 0 5 500 H2S Concentration (ppm) 1000

Corrosion

Common Solutions Allow H 2 S to Form and Treat Cover and Scrub Wet scrubbers Carbon units Biofilters Biotrickling Filters Chemical Addition Nitrate Iron Prevent H 2 S Formation Oxygen addition

Form and Treat Solutions

Form and Treat Solutions

Chemical Addition

Preventive Solution D.O. Addition No bubbles = No impact on settling Add enough D.O. to satisfy HRT Consume BOD ahead of aeration H2S Flux Aerobic Cap Sludge Blanket H2S Flux

SuperOxygenation as a Preventive Solution 40 mg/l at 1 ATM - Increasing pressure increases the saturation point - Use of pure oxygen versus air

SuperOxygenation Technology Overview Side Stream Pump ECO 2 Cone 90-95% O2 Absorption Efficiency Pure Oxygen Gas Unscreened Raw Wastewater Conveyance Pipeline SuperOxygenated Raw Water

Case Study Anson Madison Sanitary District Madison, ME Operated by Woodward and Curran 4 MGD Flow 3.5 MGD from UPM- Madison Paper 0.5 MGD from local community

Case Study Anson Madison Sanitary District Madison, ME Plant is located in close proximity to neighbors Frequent odor complaints

Case Study Anson Madison Sanitary District Madison, ME Physical Characteristics Diameter 90 ft Depth 12 ft Volume 0.57 MG Normal HRT 3.5 5 hours

Case Study Anson Madison Sanitary District Madison, ME Wastewater Characteristics Temperature 28-30 BOD 500-600 mg/l Oxygen Uptake Rate (OUR) 5-10 mg/l/hr PC Flow (MGD) HRT (hrs) OUR (mg/l/hr) 3.9 3.1 5.36 1.9 6.3 10.47 2.6 4.6 8.86 2.8 4.3 5.65

Primary Clarifier Odor No Treatment

Use of Nitrates Original Design 200 gpd = ~750 lbs O 2 @ $2.50/gal = $183,000 not working! Actual required dosage 400 gpd = 1,500 lbs O 2 @ 2.50/gal = $325,000

Design Calculations Low Flow Scenario: 2.7 MGD Flow results in 5 hour HRT 5 hr * 10 mg/l/hr * 8.34 * 2.7 MGD = 1,125 lbs O 2 /day Average Flow Scenario: 4 MGD Flow results in 3.5 hour HRT 3.5 hr * 10 mg/l/hr * 8.34 * 4 MGD = 1,168 lbs O 2 /day Peak Flow Scenario: 6 MGD Flow results in 2.3 hour HRT 2.3 hr * 10 mg/l/hr * 8.34 * 6 MGD = 1,151 lbs O 2 /day

SuperOxygenation System Design Considerations Available primary influent pump head capacity All influent pumped through cone Pump TDH at 25 Cone located at grade Resulting system capable of adding 1,680 lbs O 2 /day Up to 62 mg/l D.O. achieved

SuperOxygenation System Placement System capitalizes on PC pump head and available static head

Primary Clarifier Pumps

Oxygen Generators (2) 200 lpm (840 lbs/day) units generate oxygen at 93% purity

Economics ECO 2 Nitrates Chemical Cost $325,000 Oxygen Cost 254 kwhr/day per generator at $0.147/kwHr $27,250 Annual Savings $297,750 Equipment Capital Cost ECO 2 System, (2) O 2 Generators Installation Cost Engineering, piping, instrumentation, generator building, etc. Payback $310,000 $270,000 <2 years Oxygen cost reflects full operation of both generators

D.O. at Cone Discharge

H 2 S Level at Weir

D.O. Level at Weir

Measurement Location

Treatment Benefits Achieved H 2 S control is consistent Odor complaints eliminated BOD reduction across clarifier increased Prior to oxygen addition 15% removal Adding 1,000 lbs O 2 /day has increased BOD removal to 20% Additional 600-1,000 lbs BOD/day removed Less oxygen required in aeration $25,000-$40,000 additional annual savings

Revised Economics ECO 2 Nitrates Chemical Cost $325,000 Oxygen Cost 193 kwhr/day per generator at $0.147/kwHr $20,500 Aeration Savings $25,000 Annual Savings $329,500 Equipment Capital Cost ECO 2 System, (2) O 2 Generators Installation Cost Engineering, piping, instrumentation, generator building, etc. Payback $310,000 $270,000 1.76 years

Conclusions Operationally Compatible No impact to settling Efficient 90-95% oxygen absorption efficiency Oxygen is added to meet flow demand Economical Oxygen is inexpensive in comparison to alternatives District saves ~$300,000 per year over nitrates Reduced aeration requirements Effective H2S levels typically near non-detect

Acknowledgements Dale Clark, AMSD Plant Manager, Woodward and Curran

Questions? Kevin Jacobs (317) 706-6487 kjacobs@eco2tech.com