Diffuser Design PU Sheet Membrane Strip & Plate Aerators • Product Construction Detail & Design Weaknesses

• WWT Application Limitations

T - Type

T - Type PU Sheet Strip Aerator Elastic PU Sheet

Membrane

Rigid

Stainless Steel Plate

Glue / Solvent Bonded

/ Caulking Cement

Plastic Crimp Profile

Stainless Steel

Crimp Profile

Connection detail to

lateral air supply manifold:

HDPE Pipe Compression FittingsDesign Evaluation:

• Elastic Polyurethane (PU) sheet fine bubble membrane is solvent bonded to a dissimilar material –

rigid stainless-steel bottom plate

• The PU sheet is folded over the edge of the bottom plate

• The PU sheet / bottom plate bond is secured by & bonded to plastic crimp profile

• Plastic crimp profile is reinforced by a stainless steel crimp

SD & Q - Type PU Sheet Strip AeratorPlastic Profile / Spline

Groove

Elastic PU Sheet Membrane

Glue / Solvent Bonded

/ Caulking Cement

Rigid

PVC Profile

SD & Q

- Type

Connection detail to

lateral air supply manifold:

HDPE Pipe Compression FittingsDesign Evaluation:

• Elastic Polyurethane (PU) sheet fine bubble membrane is solvent bonded to a dissimilar material –

rigid oval shaped PVC bottom profile

• The PU sheet is secured & bonded in a groove of the bottom profile.

• The PU sheet / bottom profile bond is secured a spline / hard plastic profile

Diffuser Design Evaluation:

Tech support – Quesons & Answers

PU Sheet - Plate Aerator

Elastic PU Sheet

Membrane

Rigid

Stainless Steel Plate

Glue / Solvent Bonded

/ Caulking Cement

Plastic Crimp Profile

Stainless Steel

Crimp Profile

Design Evaluation:

• Same base design as T-Type PU Sheet Strip Aerator

• 7 x strip chambers separated & held down by stainless-steel U profile

Diffuser Design Evaluation - continued:

PU Sheet Membrane Aerators - Poduct Design WeaknessesReplacing / repairing / retrofitting the solvent bonded PU sheet membranes after its

useful life at the local WWTP:

• Example field reports:

2007 field report – T-Type strip diffuser PU sheet membrane replacement: had need for maintenance sooner than anticipated; problems with heat, organics, algae etc., ... buying sheets of membranes from OEM.... they need to first solvent clean the frames... pull out the old membranes, then use sikaflex to glue new membranes into frames, allowing to cure for 24-48 hours..... panels are about 12' x 4";

2008 filed report – evaluation of PU sheet membrane sheet replacement of T-Type strip diffuser - Cumberland County: Step involved: Draining basin, breaking connections, removing diffusers (6 bolts), lifting to surface, transporting to maintenance room, removing outer frame, scraping off old cement, using solvent to remove residual cement, cutting new membrane, applying new cement, placing new membrane on frame, place frame over base and clamp, wait 24 hours, transport back to tank, lower to floor, secure to supports (6 bolts), attach to air supply. Estimated cost to replace amembrane is $180 - $200 in materials and labor including the basin downtime and cleaning involved.

-> Conclusion: replacing the PU sheet membranes in the filed is not viable, nor economical.

Elevated WW temp, blower discharge temp., diffuser insertion depth > 15’ [4.5m],

and/or high diffuser flux rates for extended time periods:

U Hold Down Profile

Stainless Steel

-> PU membranes stretch out due to elevated heat:

SOTE performance decreases due to increased coalescence

of tubular shape ; Headloss increases; PU Membranes rupture

Intermittent Aeration WW Application: BNR, SBR, Oxic Anoxic Applications &

Swing Zones, Nutrient Loading Driven Process Design, etc.:

Plastic Profile / Spline

Groove

Elastic PU Sheet Membrane

Glue / Solvent Bonded

/ Caulking Cement

Rigid

PVC Profile

Bonding failure: PU Sheet - Bottom PVC Profile - Spline

Possible Root Cause: Overall product design; Poor factory quality; Unsuccessful PU sheet filed replacement/repair

• Elongated PU Membrane deflates in the anoxic

phase of the aeration basin./ WWT process.

• It is compressed by the static head of water

@ diffuser insertion depth

• PU membrane folds & forms a sharp crease at the

centerline of the membrane

• PU membranes splits prematurely compared to

expected membrane life.

Crease Line

Note: Some manufactures install a complex air pressure control system including modulating air vales to keep the PU sheet membrane

inflated during anoxic phases. This measure is complex. It enhance biofouling of PU membranes.

Split PU Sheet Membrane

Split PU Sheet Membrane

View Online: https://vimeo.com/342826273/76f76bd686

Static water pressure at diffuser insertion depth is compressing

membrane at a rate of 1m [3.28’] insertion depth = 10 kPa

[1.45 psi] static pressure

Static water pressure

System Turn Down – Diffuser Flux Rate Range

15’

[4.57m]

Intermied

Aeraon

High Low

[9.14m]

30’

PU Sheet Plate Aerator - Canceling out of the high SOTE advantages due to

zones of high coalescence at medium to high flux rates

Zones of high coalescence

The 7 x strip chambers are in too close proximity of each other

WWT Application Limitations - PU Sheet Membrane Aerators

BNR, SBR, Oxic Anoxic Applications &

Swing Zones, Nutrient Loading Driven

Process Design, etc.:

System Turn Down – Diffuser Flux Rate Range

Connual Aeraon

PU Sheet Membrane Aerators

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Tech support – Quesons & Answers