ENERGY REDUCTION IN SLUDGE HOLDING / PROCESS TANKS … · energy reduction in sludge holding /...

ENERGY REDUCTION IN SLUDGE HOLDING / PROCESS TANKS VIA

LARGE BUBBLE VERTICAL MIXING

LARRY L. BELLV.P. SALES – PULSED HYDRAULICS INC.

Typical Large City Energy Usage Pattern

Source: Texas Comptroller of Public Accounts

Wastewater23%

Traffic3%

Street Lights30%

Parks3%

Misc.1%

Libraries1%

Civic Center3%

BuildingServices

7%

Aviation10%

Water19%

Electrical Usage in WWTPs

Aeration is 54% of the Total Power Consumed

Aeration 54%Return SludgePumping 0.46%

Gravity Thickening 0.06%

AnaerobicDigestion 14.24%

Belt Press 3.91%

ChlorinationLighting &Buildings 8.14%

WastewaterPumping 14.26%

Screens 0.02%

Grit 1.26%

Clarifiers 3.15%

LARGE BUBBLE VERTICAL MIXING

• 25 Year Old Technology

• First used in the petrochemical and beverage industries

• Low energy and low maintenance requirements

• Low capital cost

• Used to mix any liquid that is in a vented tank or open top basin

ENERGY COST COMPARISON

• COURSE BUBBLE MIXING – 80 HP = $ 10,400 PER 90 DAYS

($115.55 PER DAY)

• SUBMERSIBLE PROPELLER – 120 HP = $ 15,500 PER 90 DAYS

JET PUMPS -120 HP ($172.22 PER DAY)

• LARGE BUBBLE VERTICAL – 20 HP = $ 2,600 PER 90 DAYS

MIXING ($28.88 PER DAY)

LARGE BUBBLE VERTICAL MIXING SAVED $12,900 PER 90 DAYS !

THE LARGE BUBBLE VERTICAL MIXING SYSTEM HAS BEEN WORKING FOR 5 + YEARS !

LARGE BUBBLE VERTICAL MIXING

• ACHIEVES SIMILAR ENERGY SAVING RESULTS FOR BIOSOLIDS UP TO 5% TSS

• REDUCES MAINTENANCE SINCE THERE ARE NO MOVING PARTS TO SERVICE IN THE TANK

• REDUCES ODORS BECAUSE OF LOW AIR USAGE COMPARED TO COURSE AIR SYSTEMS

• ACHIEVES A COMPLETE MIX WITHIN THE TANK

PROCESSING LIQUID SLUDGE REQUIRES ENERGY

ENERGY = HP = $$$$$• If HP Is Reduced, Then Fewer $$$$

Are Spent.

• When Doing Energy Evaluations In Your Plant, Look At The Mixing Systems First.

GREENSBORO, NC – T. Z. OSBORNE PLANTTWO 42’ DIAMETER SLUDGE HOLDING TANKS – OPERATING 8+ YEARS

HOW MUCH ENERGY CAN BE SAVED?LET’S USE THE GREENSBORO WWTP TANKS……

THE LARGE BUBBLE VERTICAL MIXING SYSTEM USES…..

• Each 42’ diameter sludge holding tank will require a mixer with two pulsing valves and 4 bubble forming plates. (2 tanks x 2 valves)

• Each valve will pulse once every 15 seconds (or 4 times per minute).

• Each pulse uses 3 cubic feet of compressed air.

• (4 valves) x (4 pulses) x ( 3 cu ft/pulse) = 48 scfm

• 48 cfm = 12 HP of compressor capacity = 415 KW

GREENSBORO WWTP PREVIOUSLY USED TWO 40 HP BLOWERS WITH COURSE AIR DIFFUSERS TO MIX THE SLUDGE TANKS

• The energy calculation can be made with a standard power formula……

KW = BHP x 0.746 x (hours) / motor efficiency (%)

• So, for two 40 HP Blowers……

80 BHP x 0.746 x 24 hours / 93% eff = 1540 KWH

1540 KWH (Course Air) - 415 KWH (Large Bubble) = 1125 KWH

At $0.08 / KWH……that is a savings of $ 90 per day.

BUBBLE FORMING PLATES FOR TANKS UP TO 60 ‘ DIAMETER – FLAT FLOOR

BUBBLE FORMING PLATES FOR TANKS UP TO 60’ DIAMETER – SLOPED FLOOR

BUBBLE FORMING PLATES FOR TANKS 60’ TO 90’ DIAMETER – FLAT OR SLOPED FLOOR

BUBBLE FORMING PLATE TANKS 90’ TO 120’ DIAMETER

CIRCULAR TANK DIVIDED IN HALF

RECTANGULAR SLUDGE TANK

WHAT IS A “LARGE BUBBLE?”

WHY ARE LARGE BUBBLES MORE EFFECTIVE THAN COURSE AIR BUBBLES ?

• They move more mass than do smaller bubbles using less energy.

• They move liquid & solids via the natural forces of buoyancy and gravity. The only energy required is that used to create the compressed air volume.

• They can develop velocities within tanks that approach 4 feet per second when bubbles are sequentially introduce into the tank.

WHAT ABOUT AERATED SLUDGE DIGESTION?

• Large Bubble Vertical Mixing decouples the mixing function from the aeration function….

• Traditional mixing / aeration systems try to do both but are not efficient at doing either function.

• By using a highly efficient mixing system, a much more efficient means of introducing oxygen into the sludge can be used.

“DECOUPLING” MEANS THAT AUTOMATED OXYGEN CONTROL IS MORE FEASIBLE

• On – line oxygen sensors or oxygen uptake rate monitors can be used to control oxygen addition.

• High oxygen transfer systems such as pure oxygen or ultra-fine bubble diffusers can be used.

• Oxygen is only added when needed to satisfy micro-organism requirements.

WHAT ABOUT ANAEROBIC DIGESTER MIXING?

• Large Bubble Vertical Mixing has been used for years in anaerobic digesters under various manufacturer’s brands…..one is the sludge cannon.

• The equipment required to handle methane obviously is built for explosion proof environs and is expensive.

GOVERNMENT AND ELECTRIC SUPPLIER INCENTIVES

• Numerous incentives exist from State and Federal governments and from energy suppliers to promote use of more energy efficient technologies.

• Large Bubble Vertical Mixing is a technology that meets most of the criteria described by these programs.

• The cost of the hardware needed to employ Large Bubble Vertical Mixing can be offset by these programs.

LONDON, OH – POST GRAVITY BELT THICKENER STORAGE TANK…..Hello Dan !!!

THANK YOU AND REMEMBER….

Any Mixing System That Propels Liquids In A Horizontal Direction Is Not Really Mixing.

IT IS STIRRING!

Horizontal Systems Leave Solids On The Tank Bottom Which Means The Tank Is Not

Being Mixed And The Energy Used Has Been Wasted !