SECTION 11367 FINE BUBBLE AERATION SYSTEM

This spec was part of the Des Plaines, IL River WRF project tat bid Feb 26, 2015.


SECTION 11367

FINE BUBBLE AERATION SYSTEM


PART 1 GENERAL

1.1 SECTION INCLUDES

A. New Fine Bubble Aeration Grid for Aeration Tanks 1 – 3.

B. Addition of fine bubble membrane diffusers assemblies to existing Aeration Grids in Aeration Tank Nos. 1 – 3.

C. Scope of Supply
1. Furnish all labor, materials and equipment to install, test and place into successful operation a fine bubble aeration system and as specified herein.
2. Include all applicable licenses required for use of the process.

1.2 REFERENCES

A. ASTM International:
1. ASTM A240 - Specification for Heat-Resisting Chromium and Chromium- Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels.
2. ASTM A276 - Standard Specification for Stainless Steel Bars and Shapes.
3. ASTM A380 - Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems.
4. ASTM A554 - Specification for Stainless Steel Tube, Welded, For Mechanical Applications.
5. ASTM A774 - Specification for austenitic stainless steel fittings (as-welded), for general corrosive service at low/moderate temperatures.
6. ASTM A778 - Specifications for welded, unannealed tubular products (for low/moderate temperatures and corrosive service).
7. ASTM D412 - Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension
8. ASTM D573 - Standard Test Method for Rubber—Deterioration in an Air Oven
9. ASTM D1784 - Specification for Rigid Poly (Vinyl Chloride) (PVC) Compounds and Chlorinated Poly (Vinyl Chloride) (CPVC) Compounds.
10. ASTM D1785 - Specification for Poly (Vinyl Chloride) (PVC) Plastic Pipe, Schedule 40, 80, and 120.
11. ASTM D2240 - Standard Test Method for Rubber Property - Durometer Hardness
12. ASTM D2466 - Standard Specification for Poly(Vinyl Chloride) (PVC) Plastic Pipe Fittings, Schedule 40
13. ASTM D3034 - Standard Specification for Type PSM Poly(Vinyl Chloride) (PVC) Sewer Pipe and Fittings

B. American Society of Civil Engineers (ASCE): Measure of Oxygen Transfer in Clean Water.

1.3 DESIGN REQUIREMENTS

A. General Design conditions:
1. Aeration Tanks:
a. Wastewater Characteristics:
1) Type: Municipal Wastewater.
2) Alpha value: 0.5
3) Beta value: 0.98.
b. Aeration Process: Extended aeration.
c. Number of Aeration Tanks: 3
d. Aeration Tank Dimensions: See Contract Drawings (Group 30).
e. Maximum wastewater temperature: 25º C.
f. Diffuser Type: Membrane Diffuser Elements.
2. Ambient air pressure, psia: 14.7.

B. Design the aeration system to meet the following design conditions in clean water at 14.7 PSI, 20°C, and zero mg/L dissolved oxygen; at the specified number of diffusers, submergence, air rate and pressure.

Parameter
Current Average Day
Design Average Day
Design Peak Day
Standard Oxygen Transfer Rate (lbs/day)
47,730
80,340
179,020
Number of Diffusers
6,000
8,000
8,000
Volumetric Air Rate (scfm)
5,970
10,400
25,600
Operating Pressure at top of Dropleg (psi)
7.0
7.1
7.8
Diffuser Submergence (ft)
15.0
15.0
15.0

C. Aeration Tank Nos. 1 – 3:
1. Grid No. 1:
a. Furnish new fine bubble membrane diffuser grid in each tank to replace the existing grid that will be removed, as shown on the Drawings.
2. Grid No. 2 - 4:
a. Provide additional fine bubble membrane diffuser assemblies for the existing grids, as shown on the Drawings.


Location
Number of Existing Diffuser Assemblies per Tank
Required Number of Diffuser Assemblies per Tank
Number of New Diffuser Assemblies per Tank
Total Number of New Diffuser Assemblies for Aeration Tanks Nos. 1-3
Grid No. 1
-
736
736
2,208
Grid No. 2
405
534
129
387
Grid No. 3
285
400
115
345
Grid No. 4
285
330
45
135

1.4 SUBMITTALS

A. Shop Drawings: Submit in accordance with Division 1, including the following.
1. Complete assembly and installation drawings, including plan and elevation views and appropriate cross-sections of aeration equipment.
2. Descriptive information on material and equipment furnished.
3. Headloss calculations and pressure requirements.
4. Certified performance curves for pressure loss and oxygen transfer efficiency.
5. Membrane longevity test reports.

B. Submit operations and maintenance data under the provisions of Division 1.

C. Submit certificates of proper installation and operator training under provisions of Division 1.

1.5 DELIVERY, STORAGE AND HANDLING

A. Deliver, store and handle the equipment under the provisions of Division 1.

1.6 TESTING

A. Performance Curves:
1. Submit certified oxygen performance curve in accordance with the Design Requirements before beginning fabrication of equipment.
2. Certified curve shall be log-log plot of pounds of oxygen per day per 1000 cubic feet of tank volume versus air per unit volume in tap water at 14.7 psia, 20º C and zero dissolved oxygen at the specified submergence.
3. Base certified curve on aeration test results from a full scale test facility per ASCE procedures for oxygen transfer in clean water with diffuser configuration equivalent to the actual project tank configuration.
4. Certified curve shall be prepared and sealed by a registered professional engineer.

B. Shop Test for Membrane Diffusers:
1. Conduct a performance test to demonstrate capability of the aeration equipment to meet the specified oxygen transfer requirements.
2. Test criteria:
a. A minimum of 3 tests for the Average Condition Design Requirements in accordance with ASCE Clean Water Test Procedure.
b. Conduct tests in a full scale aeration test tank (minimum of 300 ft²) at the specified submergence and water depth with a diffuser density equivalent to the specified tank configuration. Diffuser density is defined as the ratio of the total tank surface area to the total active diffuser surface area.
c. Conduct shop test with air rate and mass rate of oxygen transfer directly proportional to the ratio of the shop test tank volume and the design tank volume.

C. Membrane Longevity:

1. Provide test reports prepared by an independent testing agency to confirm membrane longevity . Membranes shall comply with the following maximum allowed percent change in each membrane property.
a. Property Maximum Change
1) Durometer 5%
2) Weight 5%
3) Permanent Set 0.5%
2. Data for a minimum of three diffusers from each installation shall be provided.


PART 2 PRODUCTS

2.1 MANUFACTURERS

A. Sanitaire, Xylem Water Solutions Inc.; Brown Deer, WI.

2.2 GENERAL

A. All equipment shall be the end product of one aeration system manufacturer. The manufacturer shall be responsible for the complete system including all items covered herein.

2.3 MATERIALS AND FABRICATION

A. Stainless Steel Materials And Fabrication - General
1. Stainless Steel:
a. Fabricate all welded parts and assemblies from sheets and plates of ASTM A240, 316L stainless steel with a 2D finish.
b. Fabricate non-welded parts and pieces from sheets and plates of ASTM A240, 316 stainless steel.
c. Cast pieces meeting ASTM A296, Type 316L stainless steel.
d. Fabricate drop legs and headers of tubular products and fittings meeting ASTM A778, ASTM A774, and ASTM A554.
e. Furnish all nuts, bolts, and washers including anchor bolts in 316 stainless steel.
2. Welding:
a. Do all welding in the factory using MIG, TIG or plasma-arc welding inert gas processes.
b. Add filler wire to all welds to provide for a cross section equal to or greater than the parent metal. Use ER 316L filler wire.
c. Fully penetrate butt welds to the interior surface and provide gas shielding to interior and exterior of joint.
d. Interior weld beads shall be smooth, evenly distributed with an interior projection not exceed 1/16" beyond the I.D. of the air header or fittings.
e. Continuously weld both sides of face rings and flanges.
f. Field welding will NOT be permitted.
g. Finish clean all interior and exterior welds and piping by full immersion pickling and rinse with water to remove all carbon deposits and contaminants to regenerate a uniform corrosion resistant chromium oxide film per ASTM A380.

B. PVC Materials And Fabrication - General
1. All PVC moldings and extrusions from PVC compound conforming to ASTM D1784, compound cell classification 12454-B with a minimum tensile strength of 7,000 PSI.
2. Minimize ultraviolet light degradation of PVC by adding two parts by weight of titanium dioxide per 100 parts of resin to PVC compounds for manifolds, air distributors, joints and PVC diffuser assembly components.
3. Factory solvent weld all PVC joints, with the exception of the connection between the lower droplegs and the manifolds. Field solvent welding is allowed at this point to prevent damage during shipping.
4. Design air distributors and manifolds to withstand 125° F mean wall temperature.
5. Provide 6-inch and larger diameter PVC piping with a minimum wall thickness of SCH 40 or equivalent, and 4-inch and smaller PVC piping with a minimum SDR of 33.5.

2.4 DIFFUSER ASSEMBLIES

A. General:
1. Diffuser assemblies shall consist of a membrane element with integral O-ring, diffuser element holder, and retaining device.
2. Diffuser assembly and retaining device shall be designed to prevent air escape at diffuser element-sealing gasket interface.

B. Membrane Diffuser Elements:
1. Circular membrane diffuser elements of EPDM synthetic rubber compound with integral O-ring and precision, die formed openings. Material shall include carbon for resistance to ultraviolet light.
2. Diffuser shall be a one-piece compression molded part with a minimum thickness of 0.080" for nominal 9-inch diameter unit.
3. Maximum tensile stress of the rubber membrane shall be less than 10 PSI when operating at 2.4 SCFM per square foot of membrane media.
4. EPDM rubber compound shall have the following minimum characteristics:
a. UV resistant
b. Specific gravity of 1.25 or less
c. Pass the ASTM D1171 Ozone Resistance test
d. Durometer (Shore A) of 58 ±5 points conforming to ASTM D2240.
e. Tensile strength of 1200 PSI conforming to ASTM D412.
f. Minimum elongation of 350% conforming to ASTM D412.
g. After accelerated aging @ 100 degrees C for 70 hours, maximum elongation shall be 75% conforming to ASTM D573.
5. Produce diffusers free of tears, voids, bubbles, creases or other structural defects.
6. Diffuser elements shall provide a uniform distribution of air bubbles across the active surface of the diffuser element when submerged in water.
7. Membrane shall collapse and seal when aeration system is turned off.
8. Membrane shall be able to collapse on to support base when air is not being diffused.

C. Diffuser Element Holders:
1. Element holders or element holders with baseplates shall provide complete peripheral edge support for ceramic or membrane diffuser element.

2. Factory solvent weld PVC diffuser element holders to the PVC distribution headers.
3. Holder to header connection shall resist a dead load of 200 pounds applied vertically to the outer edge of the diffuser unit.
4. Provide mechanism to attach ceramic diffuser to holder.
5. Include air flow control orifice and air plenum chamber below diffuser support plate.

D. Retaining Device:
1. Retaining device shall securely hold and seal the membrane diffuser to the holder.
2. Provide screw on retainer rings with a positive “O” ring seat and a minimum of 2½ complete threads for engagement. Threads shall have a minimum cross section of 1/8 inch.

2.5 AIR DISTRIBUTION PIPING

A. General:
1. All piping shall be either stainless steel or PVC.
2. All field piping connections shall be positive fixed threaded union type joints.
3. All underwater joints shall be positive locking type.
4. Threaded union joints shall consist of a spigot section with grooves solvent welded to one end of the distribution header, a threaded socket section with splines solvent welded to mating distribution header, an O-ring gasket and a threaded screw-on retainer ring. Solvent welding shall be done in the factory. The fixed union shall provide a rigid connection between headers and shall prevent rotation of either of the pipes. All fixed joints shall have interlocking splines and grooves to prevent rotation of the air distributors. All rotational forces shall be transferred through the interlocking splines. Joints that require the o-ring to transfer rotational forces between the splines are not acceptable. In lieu of   the fixed union described above, flanges with 150 pound drilling may be used to connect header pipes in accordance with ASTM standards for the specified header pipe.

B. Droplegs: Provide a band clamp coupling with gasket for the lower dropleg to manifold connection.

C. Manifolds:
1. Material: PVC
2. Fabricate manifolds with 4 inch diameter fixed threaded union or flanged joints for connection to the air distribution headers. Connection points shall be designed to prevent rotation or blow apart.
3. Design manifold, distributor connections and supports to resist thrust generated by expansion/contraction of the air distributors over a temperature range of 125? F.

D. Distribution Headers:
1. Provide 4 inch diameter air distributors perpendicular to the air manifold.
2. Header sections shall be field joined using positive threaded union type joints.

3. Diffuser element holders shall be factory solvent welded to the crown of the header in the shop.
4. Maximum spacing between distribution headers shall be 4 ft on center.
5. Provide 4 inch diameter threaded removable end caps complete with gasket, threaded coupling and end plate for clean out at the end of each distribution header.

2.6 SUPPORTS

A. Manifold Supports:
1. Manifolds shall be supported with a minimum of two supports. Manifold, connections, and supports shall resist thrust generated by expansion or contraction of the air distribution headers.
2. Manifold supports shall include stainless steel manifold hold down and guide straps mounted on stainless steel pedestals.
3. Guide straps shall have a minimum width of 2" and shall be designed to resist the following uplift without exceeding 24,000 PSI design stress.

Manifold Diameter (Inches)
Uplift Force Per Support
4
195
6-8
325
10-12
543

4. Provide supports with a mechanism to allow for plus or minus two inches vertical and ½ inch lateral adjustment for alignment of the manifold in the field.

B. Air Distribution Header Supports:
1. Each section of distribution header shall have a minimum of two stainless steel supports with a maximum spacing of 7'-6".
2. Distribution header supports shall be located to coincide with the zero bending moment point.
3. Distribution header sections shall have fixed supports to prevent longitudinal and rotational movement of the header.
a. Fixed supports shall consist of a hold down mechanism and self-limiting clamp device.
b. Hold down mechanism and clamp shall provide a 1-1/2-inch wide contoured bearing surface for the air distribution header.
c. Clamping device shall positively grip the air distribution header when tight and be self-limiting to prevent over stressing the header if the clamp is over tightened.
4. Intermediate distribution header supports or guide supports shall allow longitudinal movement of the header section to prevent stress build up due to expansion/contraction forces.
a. Guide supports shall consist of a self-limiting hold down and sliding mechanism.
b. Hold down and sliding mechanism shall provide a full circumferential 1- 1/2-inch wide contoured bearing surface with chamfered leading edges to minimize binding of the air distribution header.

c. Sliding mechanism shall provide minimum resistance to movement of the air distribution header under full buoyant uplift load. Mechanism shall provide 1/8" clearance around header and be self-limiting if the mechanism is over tightened.
d. Maximum horizontal thrust of 20 pounds or less shall initiate movement of the header relative to the support under full buoyant uplift load.
5. Supports shall be provided with a mechanism to provide for plus or minus 1-1/2- inch vertical adjustment for alignment of the air distribution headers in the field. Mechanism shall allow precise leveling of the air distribution headers and diffuser assemblies.

C. Anchors: Provide 316 stainless steel, adhesive concrete anchors, as specified in Section 05500.

2.7 DRAINLINE, SUMP AND AIR LIFT PURGE SYSTEM

A. A PVC drainline, sump and airlift purge system to drain the entire submerged aeration piping system shall be provided for each new aeration grid.

B. Each aeration grid shall be constructed with an integral drainline terminating at a sump. The sump bottom elevation shall be lower than the invert of the air distribution headers and drainline.

C. A 3/4-inch diameter airlift eductor line shall extend from the drainline invert elevation to a point 18 inches above the basin water level and terminate with a PVC ball valve.

D. Support airlift eductor by stainless steel wall brackets.

2.8 DIFFUSER PRESSURE MONITORING SYSTEM

A. Monitoring equipment shall be provided to measure dynamic wet pressure of a typical diffuser in each new aeration grid and air flow for each new grid.

B. Provide one portable monitoring panel with the system. Panel shall include:
1. Orifice differential pressure gauge.
2. Diffuser dynamic wet pressure gauge.
3. Bubble line rotometer.
4. PVC ball valves.
5. Quick coupling connectors.
6. Polypropylene fittings.
7. Polyethylene tubing.
8. One set calibration curves.

C. Furnish one connecting box, bubble tube, support brackets, polyethylene tubing and carrier pipe for each new aeration grid.
1. Mount connecting box on tank handrail.
2. Furnish fiberglass connecting box capable of transmitting the following to the portable monitoring panel.
a. Air distribution header pressure.
b. Diffuser element holder plenum pressure.
c. Submergence pressure.

3. Furnish ½-inch diameter bubble tube and appropriate 1/4-inch and 3/8-inch diameter polypropylene tubing for header and diffuser pressure in a 4" diameter PVC carrier pipe.


PART 3 EXECUTION

3.1 INSTALLATION

A. Install in accordance with Drawings, shop drawings, and manufacturer's instructions.

B. Clean all air piping prior to installation of diffuser elements.

C. Level aeration system such that all diffusers are within plus or minus 1/4-inch of a common horizontal plane.

D. Protect diffuser elements from freezing at all times.

3.2 FIELD TESTING OF SUPPORTS

A. Field test at least one percent of the air distribution manifold and header support assemblies after installation of the assemblies and before installation of the piping.

B. Conduct testing in the presence of the Engineer on assemblies selected by the Engineer.

C. Conduct tests on a complete support assembly including anchor bolt, hold down mechanism, and clamp.
1. Test by inserting into the assembly a metal pipe specimen attached to a lever which is placed on a fulcrum.
2. Apply a static load to the opposite end of the lever to produce a vertical extracting force on the complete support assembly equal to 4 times the calculated maximum buoyant force which the support assemblies will be subjected to during       normal operation.

3.3 MANUFACTURER'S SERVICES

A. Provide manufacturer's services under provisions of Division 1.

B. Minimum service requirements:
1. Installation: As required for proper installation.
2. Start-up, Field testing: Three trips, one half day on site for each trip.
3. Operator training: One half day on site.

C. Service to Repair Defective Work: Provide during one-year warranty period under the provisions of General Conditions.

END OF SECTION