1

Process AerationProcess Aeration

Joe Hebert, Ottawa County Public Utilities

Micro-bubble Generators

Bubble Size Relationship

Course = ≥10 mm Medium = 4-9 mm Fine = 1-3 mm

Ultra-Fine = 1 mm Micro = 0.5-0.01 mm Nano = 0.001 mm

2

Bubble Size Relationship

1 cu ft = 1 bubble 10mm = 5.4 X 104 1mm = 5.4 X 107

0.25mm = 3.4 X 1097,300 square feet

0.02mm = 6.7 X 101234,000,000,000 square feet

Terminology and Formulas

Oxygen Transfer Rate of Diffuser = Oxygenation Rate

OTR Approximately = scfm air (1.036) SOTE = lb O2/hr

Example Airflow = 200 scfm & diffuser efficiency 22%OTR = 200 scfm air (1.036) 0.22 = 45.58 lb O2/hr

Oxygen Transfer EfficiencyEfficiency/Meter as % = Em

Em = % SOTE/meter submergence

gram/m3 air per m submergence = 1.036 (Em) 1000/2.206 (1.7)

Em as % = gram/m3 air per meter (2.2046) 1.7 / 1.036 (1000)

Em = SOTE/Ft submergence (3.2808)

3

Typical Oxygen Transfer Values (in clean water)

SystemSystemOxygen Transfer Efficiencya

percent

Oxygen Transfer RateOxygen Transfer Ratebb

lb/ hplb/ hp--hrhr

Micro Bubble GeneratorsMicro Bubble Generators 1010--2727

Fine Bubble Diffusers (total floor Fine Bubble Diffusers (total floor coverage)coverage)

22-32 6.06.0--6.56.5

Fine Bubble Diffusers (side wall Fine Bubble Diffusers (side wall installation)installation)

1818--2020 3.53.5--4.54.5

Jet Aerators (fine bubble)Jet Aerators (fine bubble) 1818--2525 3.03.0--3.53.5

Static Aerators (medium bubble)Static Aerators (medium bubble) 1010--1212 2.32.3--2.82.8

Mechanical Surface AeratorsMechanical Surface Aerators 2.52.5--3.53.5

Coarse Bubble Diffusers (wide Coarse Bubble Diffusers (wide band pattern)band pattern)

88--1212 2.02.0--3.03.0

Coarse Bubble Diffusers (narrow Coarse Bubble Diffusers (narrow band pattern)band pattern)

66--88 1.51.5--2.02.0

a at 15 feet submergence b 1 lb/hp-hr = 0.61 kg/kW-hr

Existing SystemExisting System

•• 3 cell lagoon system3 cell lagoon system

•• (2) 4.6 acres and (1) 1 MG final(2) 4.6 acres and (1) 1 MG final

•• 300,000 gpd flow300,000 gpd flow

•• Influent loading: 200 Influent loading: 200 –– 300 mg/l BOD300 mg/l BOD

•• 30 hp Hinde aeration in primary lagoon30 hp Hinde aeration in primary lagoon

Ackley, Iowa

4

The ProblemThe Problem

•• In 2000 In 2000 –– 30 inches sludge in primary lagoon30 inches sludge in primary lagoon

>15 inches in secondary lagoon>15 inches in secondary lagoon

•• Estimates for sludge removal were $250Estimates for sludge removal were $250--275,000275,000

•• Aging aeration systemAging aeration system

Ackley, Iowa

The SolutionThe Solution

•• August 2001 August 2001 –– Installed (4) 2 hp microbubble generators Installed (4) 2 hp microbubble generators from WTR Solutions LLC. from WTR Solutions LLC. 10.4 lbs O10.4 lbs O22/hp/hr each unit (600 lbs/O/hp/hr each unit (600 lbs/O22/day ea.)/day ea.)

•• 2005 2005 –– Installed 2 units in cell #2Installed 2 units in cell #2

CostCost

Approximately $10,000 each (installed)Approximately $10,000 each (installed)

Ackley, Iowa

5

Ackley, Iowa

ACKLEY AVERAGE SLUDGE DEPTHS

0

5

10

15

20

25

30

Jul-01 May-02 Oct-02 Sep-04 Jun-05 Oct-05 Jun-06

Inch

es

Cell #1 Cell #2 Cell #3

•• 2005 2005 –– owner was satisfied with results and owner was satisfied with results and purchased 2 more aerators for installation in cell purchased 2 more aerators for installation in cell #2 to help meet effluent quality limits.#2 to help meet effluent quality limits.

•• 2011 2011 –– Superintendant Jack Boelman, Superintendant Jack Boelman, PeopleServices Inc., reports sludge depths still at PeopleServices Inc., reports sludge depths still at 6” in cell #1.6” in cell #1.

•• No reported maintenance issues on units.No reported maintenance issues on units.

Ackley, Iowa

6

Final ResultFinal Result

Sludge in 1Sludge in 1stst and 2and 2ndnd cells was significantly reducedcells was significantly reduced

Project costs:Project costs: $60,000$60,000

Initial savings:Initial savings: >$200,000>$200,000

Ongoing savings:Ongoing savings: 18 hp equivalent less power usage18 hp equivalent less power usage

Ackley, Iowa

Existing system Existing system -- 20092009

•• 110,000 gpd (during harvest)110,000 gpd (during harvest)

•• 6,400 mg/l BOD6,400 mg/l BOD

•• 3 Lagoons (2.36M, 2.09M, 1.1M gallons)3 Lagoons (2.36M, 2.09M, 1.1M gallons)

•• brush aerators = 105 hp brush aerators = 105 hp

7

ProblemsProblems

•• High maintenance and electrical costs of aeratorsHigh maintenance and electrical costs of aerators

•• Low OLow O22 and odor problems (near tasting room)and odor problems (near tasting room)

•• Plugging drip irrigation systemPlugging drip irrigation system

•• Removed 250,000 gal sludge from last cell Removed 250,000 gal sludge from last cell –– 20092009

•• Up to 48” sludge in primary Up to 48” sludge in primary -- April 2010April 2010

The SolutionThe Solution

•• April 2010 April 2010 -- Installed (18) 3 hp VMB 750 Installed (18) 3 hp VMB 750 microbubble generators delivering 10.99 lbs microbubble generators delivering 10.99 lbs OO22/HP/HR each. (791.28 lbs O/HP/HR each. (791.28 lbs O22/day ea.)/day ea.)

Manufactured by: VMB Technologies Inc.Manufactured by: VMB Technologies Inc.

•• Project costs: approx. $189,000Project costs: approx. $189,000

8

The ResultThe Result

•• Reduced HP from 105 to 54 saving $39,152 yrReduced HP from 105 to 54 saving $39,152 yr

•• Received PG&E incentive $32,417Received PG&E incentive $32,417

•• 4 year simple payback4 year simple payback

•• Reduced maintenance on equipment and irrigations system Reduced maintenance on equipment and irrigations system

August 2010 August 2010 -- Reduced sludge in primary to 3”Reduced sludge in primary to 3”--14” (3014” (30--40%)40%)

Influent @ 4,090 mg/l BODInfluent @ 4,090 mg/l BOD55Effluent @ 36 mg/l BODEffluent @ 36 mg/l BOD55

Existing SystemExisting System

•• 2 Sequencing Batch Reactors 2 Sequencing Batch Reactors

•• .948 MGD capacity (.220 MGD average).948 MGD capacity (.220 MGD average)

•• MLSS 1,500 MLSS 1,500 –– 2,200 mg/l 2,200 mg/l -- 2020--30 day CRT30 day CRT

•• 3 3 -- 50,000 gallon sludge blending/holding tanks50,000 gallon sludge blending/holding tanks

•• Gravity belt thickening using polymerGravity belt thickening using polymer

•• $25,000 $25,000 -- $30,000 year to land apply sludge$30,000 year to land apply sludge

9

Pilot Study 2007 – Present

GoalGoal: Reduce sludge handling cost through aerobic digestion and on-site sludge drying

•• Installed (6) 2 hp microbubble generators from WTR Installed (6) 2 hp microbubble generators from WTR Solutions LLC. Solutions LLC.

10.4 lbs O10.4 lbs O22/hp/hr each unit (600 lbs/O/hp/hr each unit (600 lbs/O22/day ea.) /day ea.)

•• Installed reed drying beds Installed reed drying beds

Pilot Study 2007 – Present

•• Monitored DO (not ORP) in determining sludge retention Monitored DO (not ORP) in determining sludge retention time and wasting rate.time and wasting rate.

•• Series flow through sludge tanks before pumping to reed Series flow through sludge tanks before pumping to reed beds.beds.

•• Tried various operational techniques to reduce volatiles, Tried various operational techniques to reduce volatiles, decant supernatant, and maximize % solids. decant supernatant, and maximize % solids.

10

2010 Observed Results

“no aeration” pump 3 days/week @ 2 hrs/day to reed beds

“with aeration” pump yyyy1 day/week @ 2hrs/day to reed beds

VSS reductions of yyyy50%

More empirical data needed to determine true effectiveness and value

Operators are satisfied with performance

Joe Hebert

Ottawa County Road Commission, Department of Public Utilities

Email: jhebert@ottawacorc.com

Office: 616-850-7219 Cell: 616-638-0382

11

Equipment SuppliersEquipment Suppliers

VMB Technologies, Inc.

4042 Jeffrey,

Yorba Linda, CA 92886

Phone (626) 330-4311

Fax (626) 330-1850

www.mbgenerator.com

Sam.vmb@gmail.com

ClearBlu Environmental135 Aviation Way #1Watsonville, CA 95076office: 831-724-1377mobile: 408-828-3881clrblu.com

WTR Solutions, LLCPO BOX 515Earlham, Iowa 50072

John JacobsOffice: 515-758-3833Fax: 515-758-3912www.wtrsolutions.com