FA5205-15-R-0007-0002_Atch._1_Addendum_No._2_Wastewater_Process.pdf

REPR Main Base WWTP, B1190 Misawa AB, Misawa, Japan

Addendum 2

Wastewater Process

Prepared by

04 June 2015 Attachment 1 to FA5205-15-R-0007-0002

Dated 5 Jun 15

Wastewater Treatment Plant Design Misawa AB, Japan

TABLE OF CONTENTS

A. Codes and Standards……………………………………………………….………. 1 B. Existing Conditions…………………………………………………………………. 1

1. General…………………………………………………………………….…… 1

2. Current Flows and Loadings………………………………………..………... 2

C. Sampling Program………………………………………………..…………………. 4 D. Proposed Modifications………………………………..…………………………… 5

1. Organic Loading……………………………………………………..………… 5

2. Hydraulic Design Criteria………………………………………….………….. 5

3. Headworks…………………………………………………………….……….. 6

4. Primary Treatment…………………………………………………..………… 6

5. Flow Splitting…………………………………………………………..………. 7

6. Activated Sludge System…………………………………………….………. 7

7. Secondary Clarifiers………………………………………………………….. 11

8. Disinfection ………………………………………………………………..….. 12

9. Sludge Processing……………………………………………………….……13

LIST OF APPENDICES

Appendix A – JEGS and Permit Limits

Appendix B – Plant Operation Information, September/October 2014

Appendix C – Influent and Effluent Test Data, September/October 2014

Appendix D – Influent and Effluent Summaries, September/October 2014

Page i 4 June 2015

PROCESS ENGINEERING

A. CODES AND STANDARDS

The following Codes, Standards and Regulations will be utilized in the design of this project:

• UFC 1-300-09N Navy And Marine Design Procedures

• UFC 3-240-01 Wastewater Collection

• UFC 3-240-02 Domestic Wastewater Treatment

• UFC 3-240-03N Wastewater Treatment Systems

• Recommended Standards For Wastewater Facilities, 2004

B. EXISTING CONDITIONS

1. General

a. Main Base:

The Wastewater Treatment Plant (WWTP) for the Main Base was constructed in 1988 for a design population of 13,000 persons. The average hydraulic design capacity of the WWTP is 1.3 million gallons/day (MGD), which equates to 100-gallons/capita/day. The peak hour hydraulic design capacity of the WWTP is 3.9 MGD [2,700 gallons/minute (gpm)], which is a peaking factor of 3.0. Design parameters for the Main Base WWTP are as follows:

Parameter Influent Effluent BOD 240 mg/L 20 mg/L COD 120 mg/L 20 mg/L SS 320 mg/L 40 mg/L Total N 50 mg/L 10 mg/L Total P 6 mg/L 1 mg/L FOG 107 mg/L 30 mg/L pH N/A 5.8 to 8.6 s.u.

Coliform N/A 1,000

PCS/cm3

The Main Base WWTP utilizes the activated sludge process for secondary treatment, and tertiary treatment consisting of separate nitrification / denitrification / coagulant settling.

Disinfection utilizes sodium hypochlorite.

Three structures make up the Main Base WWTF:

Building 1191 Headworks Building 83108 Treatment Works Building 1190 Control Building

Page 1 4 June 2015

b. North Base

The North Base WWTP was constructed in 1985. It has an average hydraulic design capacity of 0.43 MGD, which equates to 100-gallons/capita/day for a design population of 4,300 persons.

Similar to the Main Base WWTP, the North Base utilizes the activated sludge process for secondary treatment, and separate nitrification / denitrification / coagulant settling for tertiary treatment. Sodium Hypochlorite is added for disinfection prior to discharge.

Design parameters for the North Base WWTP are unknown, but may be assumed to be similar to the Main Base parameters.

There are two treatment structures at the North Base WWTP:

Building 83114 Treatment Works / Headworks Building 1950 Control Building

2. Current Flows and Loadings

a. Main Base WWTP Flows for the Main Base WWTP are summarized as follows:

Year Average Max. Day 2010 0.680

MGD

0.977

MGD

2011 0.636

MGD

0.915

MGD

2012 0.681

MGD

0.888

MGD

2013 0.672

MGD

1.340

MGD

Samples are taken throughout the treatment process in order to proactively control the process. Sample locations were noted to include the equalization (EQ) tank discharge, secondary clarifier effluent, and plant effluent/post-disinfection.

Test results of influent samples do not reflect what would be expected from domestic wastewater. Plant data results from 2010 through 2012 indicate average Biochemical Oxygen Demand (BOD) loadings less than 100 mg/L. Empirical data would suggest an average influent BOD concentration of 200 mg/L to be a reasonable value. Current sampling procedures utilize a single grab sample, which is likely not representative of the actual loadings.

Grab samples taken after various unit processes should provide a more representative result of the average, since flows and loadings are mixed and recycled throughout the treatment process.

Grab samples taken on September 12, 2012 were reviewed and indicate the following results:

Page 2 4 June 2015

Location Description

Assumed Sample

Location

BOD TSS N P

Influent EQ Tank 12 mg/L mg/

L mg/

L

1.9 mg/

L Discharge Secondary

Effluent 0.7 mg/L mg/ L mg/

L

0.6 mg/

L Effluent Plant Effluent <0.5 mg/L mg/ L mg/

L

0.8 mg/

L

While the unusually low influent sample concentrations may be attributed to sampling techniques, the secondary effluent and plant effluent results may reflect actual concentrations.

The required treatment standards are noted in the December 2012 Japan Environmental Governing Standards (JEGS), and are summarized below:

Parameter Allowable Limits

JEGS 2012 C4.3.1

BOD - 7-Day Avg. 45 mg/L BOD - 30-Day Avg. 30 mg/L TSS - 7-Day Avg. 45 mg/L TSS - 30-Day Avg. 30 mg/L COD 120 mg/L Total Coliform 3,000/ml Nitrogen 120 mg/L Phosphorus 16 mg/L

Comparing the September 12, 2012 sampling data to the JEGS requirements, one can conclude that the wastewater treatment after the secondary treatment process meets the JEGS requirements; the additional tertiary process is unnecessary to comply with current JEGS requirements. Also see Appendix A.

To confirm the loadings and level of treatment, a detailed Sampling Program is recommended in the Preliminary Design Phase.

b. North Base WWTP:

Flows from the North Base are summarized as follows:

Year Average Max. Day 2010 0.154

MGD

0.254

MGD

2011 0.148

MGD

0.340

MGD

2012 0.152

MGD

0.261

Page 3 4 June 2015

2013 0.180

0.518

Similar to the Main Base, test results are based on grab samples. While no influent test data was available, the effluent values were very low, indicating a high degree of treatment.

Appendix B contains plant operational information.

C. SAMPLING PROGRAM

Current loading data is atypical, and does not appear to be representative of what is found in domestic wastewater. The raw sewage strength may appear to be too low due to the sampling techniques being utilized. Valid data must be acquired, upon which a new, more efficient design may be based. Design team decided on the following sampling program:

1. Acquire and test samples for thirty (30) consecutive days.

2. Compare test results to empirical data utilized in the Design Charrette proposed treatment system.

a. Confirm or revise assumptions made with respect to the proposed design.

3. Testing Locations:

a. Main Base influent flume.

b. Main Base secondary effluent trough.

c. North Base influent flume.

4. Testing Parameters:

a. Biochemical Oxygen Demand (BOD).

b. Total Suspended Solids (TSS).

c. Ammonia.

d. Fats, Oil, Grease (FOG).

5. Continuous sampling is required to provide representative, accurate and repeatable results. A composite, automatic, refrigerated sampler is recommended.

Appendices C and D contain sampling results.

Page 4 4 June 2015

D. PROPOSED MODIFICATIONS

The Main Base Wastewater Treatment Plant (WWTP) is in need of modifications to accomplish the following objectives:

• Modernize the facilities and maintain JEGS requirements.

• Reduce energy consumption.

• Improve environmental impact by reducing chemical usage.

• Include wastewater flows and loadings from the North Base WWTP, and potentially the Industrial Plant flows/spills.

1. Organic Loading:

1.73 MGD = 17,300 Population Equivalent (PE)

2. Hydraulic Design Criteria:

Current average, design and maximum month flows to the Main Base and North Base WWTP are summarized as follows:

Current Average Flows

Main Base ......................................................... 0.681 MGD North Base ........................................................ 0.160 MGD Total.................................................................. 0.841 MGD

Current Maximum Month Flows

Main Base ......................................................... 0.737 MGD North Base ........................................................ 0.229 MGD Total.................................................................. 0.966 MGD

Current WWTP Design Flows

Main Base ........................................................... 1.30 MGD North Base .......................................................... 0.43 MGD Total.................................................................... 1.73 MGD

Utilize a peaking factor of 2.0 to provide a conservative design, a factor of safety, and allow units to be taken off-line (1.73 x 2 = 3.46). Utilize the original Main Base peak hour flow rate (2,700 gpm) as the design peak hour flow rate for a 60-minute period, as it is larger than the North Base and both are unlikely to occur simultaneously. Therefore, the hydraulic design criteria are:

Design Average Daily Flow ................................. 1.73 MGD Design Maximum Month Flow ............................. 3.46 MGD Design Peak Hour Flow ........................................ 3.9 MGD

Page 5 4 June 2015

It is important to note that the hydraulic capacity of the proposed system must be based on realistic flow data and reasonable peaking factors. Making the WWTP hydraulic capacity too small will lead to operational and compliance issues; while too large will lead to inefficiencies, increased Operation & Maintenance (O&M) costs and inflexibility, in addition to operational challenges.

100-Gal./Capita/Day

17,300 PE x 0.17 lbs. BOD/PE/Day = 2,941 lbs. BOD/Day

17,300 PE x 0.20 lbs. TSS/PE/Day = 3,460 lbs. TSS/Day

Add 25 mg/L Ammonia Loading:

25 g/L NH3-N x 1.73 MGD x 8.34 = 361 lbs. NH3-N/Day

3. Headworks:

The two (2) existing coarse screens will be demolished, and replaced with two (2) automatic units with bagging systems for material removed from the flow stream. The screens are activated by ultrasonic level sensors, utilizing a differential in the upstream/downstream water level. New stop gates are provided to isolate the individual channels for maintenance. Each screen is rated for 1.94 MGD.

The two (2) grit pumps, and the discharge hose and valves, will be demolished.

Submersible vortex type centrifugal pumps, matching the current make/model, are specified. The existing grit dewatering channel will remain in service.

The two (2) comminutors and two (2) fine screens will be demolished and not replaced, as they provide no benefit within the new facilities.

The influent flow meter will be replaced with an ultrasonic type level sensing flow meter.

The existing 18-inch Parshall flume will be utilized with the new instrumentation. An automatic, flow proportional, refrigerated sampler will also be provided.

The four (4) influent pumps will be replaced with new submersible, centrifugal type pumps with Variable Frequency Drives (VFD’s). The pumps will match the current pump make/model, with larger motors. The level control system will be replaced with a pressure transducer as the primary device, and floats for back-up control. The VFD’s will vary the speed of the pumps based on the wet well level. New discharge piping and valves will also be provided in the Headworks.

4. Primary Treatment:

The existing primary clarifier (oil/water separator) will be demolished. New microscreens will be provided. Two (2) dual belt units will have a capacity to treat an average flow rate of 1.73 MGD, and a peak hour flow rate of 3.9 MGD. In addition to removing floatable FOG, micro-strainers may remove 25% of BOD and 50% of TSS loading. This will reduce sludge volume produced and decrease electrical demand for aeration.

Page 6 4 June 2015

Primary Treatment Summary

Influent BOD ................................................. 2,491 lbs./day 25% Reduction ................................................ 735 lbs./day Primary Effluent ............................................ 2,206 lbs./day BOD

Influent TSS .................................................. 3,460 lbs./day 50% Reduction ............................................. 1,730 lbs./day Primary Effluent ............................................ 1,730 lbs./day BOD

Two (2) dual belt microscreens will be provided. Each microscreen unit utilizes two (2) independent belt systems and one (1) common dewatering assembly. This arrangement allows a single belt to handle the average daily flows. The 3.9 MGD peak hourly flow rate can be processed with one (1) dual belt unit and a single belt from the other unit.

This allows one (1) belt to serve as a redundant unit. Dewatered material is expected to range from 20% to 40% total solids. A common screw conveyor transports the dewatered material to a dumpster, where an automatic bagging system may be provided to contain the material.

The microscreens will be enclosed in a new structure, built on top of the northwest corner of the existing 83108 tankage. This allows for gravity flow from the microscreens through the entire treatment process.

5. Flow Splitting:

Wastewater from the microscreens flows to a splitter box. One (1) side of the influent splitter box evenly divides the forward flow between four (4) treatment trains. On the other side, Return Activated Sludge (RAS) and Nitrate-rich Mixed Liquor Return (MLR) are combined and evenly divided between the four (4) treatment trains. Each train may be isolated by raising the weir gate and preventing flow to the selected train. The same theory may be utilized to capture industrial spills in a single train to prevent upsetting the entire WWTP.

6. Activated Sludge System:

a. Check Tank Volumes

Convert Equalization (EQ) basins, aeration basins, secondary clarifiers, and one-half of the nitrification basins to a single plug flow reactor, with four (4) trains.

The secondary clarifier tankage will be demolished to allow new aeration tankage to be constructed, which has the same Sidewater Depth (SWD) and hydraulic profile as the other aeration tankage.

The SWD, as measured from the common floor elevation 26,900, will be 14.76-feet (4.50 m) for all aeration tanks.

Page 7 4 June 2015

A summary of the converted tankage is summarized below:

Tank Volumes

EQ Basins → Anoxic Tanks........... 481,499-gallons Aeration Basins → Aeration Stage A ..... 526,286-gallons Secondary Zone → Aeration Stage B ..... 348,744-gallons One-Half Nitrification Zone → Aeration Stage C ..... 201,637-gallons Total ............................. 1,558,166-gallons or 208,311 cu.ft.

b. Influent Loading

The design influent BOD loading to the activated sludge treatment system following microscreening is 2,206 lbs./day or 153 mg/L at average design flow conditions.

The design influent ammonia loading to the activated sludge treatment system is 361 lbs./day or 25 mg/L at average design flow conditions following microscreening. Influent Total Kjeldahl Nitrogen (TKN) is estimated at 35 mg/L or 505 lbs./day at average design flow conditions.

c. Secondary Treatment

The secondary treatment system is designed as a pre-denitrification single sludge nitrification/denitrification suspended growth system. The objective of this treatment system is to biologically remove nitrogen from the wastewater using aerobic zones for ammonia oxidation and anoxic zones for nitrate reduction to nitrogen gas.

Raw wastewater is introduced to the pre-anoxic zones along with nitrate-rich MLR flow from the aerobic stages and RAS from the secondary clarifiers.

Heterotrophic organisms in the mixed liquor use nitrate and nitrite as their oxygen source for oxidation and synthesis of organic matter (BOD) into cell mass in the absence of Dissolved Oxygen (D.O.). ORP instrumentation at the influent/effluent ends of each anoxic train, provide feedback to the Operator:

1) Anaerobic ORP Range: -100 to -200 mV

2) Anoxic ORP Range: -50 to +50 mV

3) Aerobic ORP Range: +100 to +300 mV

The process also recovers some of the alkalinity lost due to ammonia oxidation in the aerobic zones providing a more stable pH downstream. The existing sodium hydroxide feed system will remain in operation for backup purposes, should pH adjustment be necessary to prevent 8ldg.8ecation inhibition. pH instrumentation in each aeration stage provides feedback to the WWTP Staff.

Page 8 4 June 2015

The lower BOD concentration in the downstream aerobic zones provides a suitable environment for ammonia oxidation by the nitrifying organisms. The nitrate produced in the aerobic zone is then recycled back to the anoxic zone, as mentioned previously, where it is reduced to nitrogen gas and removed from the system. The remaining biodegradable fraction of BOD is also oxidized in the aerobic zones producing an effluent with very low BOD and ammonia concentra-tions, and total nitrogen concentrations less than 10 mg/L, provided that there is enough biodegradable carbon and residence time in the anoxic zones for complete denitrification. The existing methanol system will remain in service to provide a carbon source, should process conditions warrant. A nitrate sensor is provided in the clarifier effluent channel to provide feedback to the WWTP Staff.

Adjustments to the MLR rate may be made, once it has been confirmed that there is sufficient carbon available.

Typical design criteria for pre-denitrification nitrification/denitrification systems are as follows:

Parameter Values System SRT, days 6 – 30 HRT, hours

Anoxic Zones 2 – 5 Aerobic Zones 4 – 12

MLSS, mg/L 1,500 – 4,000 Mixed Liquor Recycle (2 – 4) Qin RAS Flow 100% (Qdesign) DO, mg/L

Anoxic Zones 0 Aerobic Zones 0.5 – 2

Source: Biological & Chemical Systems For Nutrient Removal, WEF, 1998.

The proposed treatment system is designed to include four (4) treatment trains, each with an anoxic tank consisting of three (3) completely mixed zones, followed by aerobic tanks with three (3) separate stages. The first stage includes three (3) grids followed by two (2) stages, each consisting of a single grid.

Channels are provided for bypassing the second and or third stages, as required based on required aeration capacity or maintenance needs. The anoxic zones are mixed using two (2) hyperbolic mixers per train. A wet well and submersible pumps are provided to return mixed liquor from the final aerobic stages to the head of the anoxic zones, along with the settled sludge (RAS) from the secondary clarifiers.

Page 9 4 June 2015

Two (2) treatment trains are required, based on design flows and loadings, providing the following design Hydraulic Residence Times (HRT) in each compartment at design average (1.73 MGD) flow with all stages in service.

HRTanoxic = 3.4 hours HRTaerobic = 7.6 hours

Additional trains are required to provide a suitable HRT at design maximum month (3.46 MGD) and design peak (3.9 MGD) flows.

While hand calculations were completed to confirm that other design parameters are within the range of typical values for the proposed system, system modeling is required to narrow in on specific design parameters including design MLSS concentration, sludge age and recycle ratios. It should be noted that operation of multiple anoxic trains, as well as methanol addition, may be required to meet a Total Nitrogen limit of 10 mg/L due to the low design influent BOD to nitrogen ratio in the wastewater. A BOD to nitrogen (TKN) ratio greater than 5:1 is desirable, while a ratio of only 4.4:1 exists based on influent design loadings, and it may be lower based on current influent loading data.

Modeling has been completed using BioWin, a wastewater treatment process simulator that ties together biological, chemical and physical process models.

The BioWin model is owned, developed and supported by EnviroSim Associates, Ltd., and is used worldwide for designing, upgrading and optimizing wastewater treatment plants of all types.

d. Aeration

The spiral roll aeration system in the EQ basins, aeration basins and nitrification basins will be demolished and replaced with a fine pore aeration system. Full floor coverage will be provided to enhance mixing, oxygen transfer and energy efficiency.

The modified aeration system utilizes four (4) parallel trains, taking advantage of the existing flow design. Three (3) separate aeration stages are created to allow flexibility to increase or decrease the HRT and the amount of oxygen being delivered. By opening gates to divert flow away from the next aeration stage, and directing it to the final clarifiers, the Operator can control the HRT and amount of oxygen transfer.

Aeration Stage ‘A’ is the initial aeration stage, and consists of three (3) grids due to the existing tankage configuration. The aeration diffusers are arranged in a tapered design to allow more oxygen to be transferred at the influent end, where the demand is the greatest. The tapered design incorporates an initial higher diffuser density, as compared to the effluent end of the stage. Within Stage A, Grid 1 consists of 175 diffusers per train, Grid 2 consists of 125 diffusers per train, and Grid 3 has 115 diffusers per train.

Page 10 4 June 2015

Flows from Stage A may be directed to the final clarifiers or to Aeration Stage ‘B’.

Aeration Stage B continues with the overall tapered design by having a lower diffuser density than Grid 3 in Stage A. Stage B consists of a single grid with 200 diffusers per train.

Flows from Stage B may be directed to the final clarifiers or to Aeration Stage ‘C’.

The tapered design for Stage C utilizes the lowest diffuser density and includes 96 diffusers per train.

The aeration system incorporates a full floor coverage concept in which the diffusers are spread-out on the basin floor. This design has the ability to provide better mixing and oxygen transfer, as compared to the previous spiral roll design.

The diffusers are 9-inch diameter EPDM membranes, which are mounted on a PVC distribution system. Due to increased efficiencies, less air is required for transferring oxygen, as compared to the previous spiral roll design.

Based on the design flows and loadings, two (2) of the four (4) aeration trains are required for treatment. This results in significant Operator flexibility, redundancy, lower O&M costs, and the ability to segregate and contain episodes of influent toxicity.

There are five (5) existing blowers; each rated for 35 m3/min. @ 53.9 kPa. At design conditions, the new aeration system will require 37.75 m3/min.. @ 57.4 kPa. This would allow a single blower to meet the air requirement most of the time by raising the discharge pressure to 3.5 kPa. It is possible to accomplish this by simply increasing the blow-off pressure of the pressure relief valve.

Three (3) of the five (5) existing blowers will be wired, while the remaining two (2) shall be backup units. Each wired blower will utilize a VFD. Together with D.O.

monitors, the blowers will speed up or down, based on the actual oxygen demand of the wastewater. Along with the benefit of using less energy, better process control can be achieved.

7. Secondary Clarifiers:

Utilize deep, circular clarifiers in lieu of the inefficient existing shallow, rectangular units.

Select Surface Overflow Rate @ ADF = 1,000 gpd/sq.ft.

Required Surface Area = 1,730 sq.ft.

Check Overflow Rate @ Maximum Month = 1,500 gpd/sq.ft.

Required Surface Area = 2,307 sq.ft.

- Provide 3,000 sq.ft. of Surface Area

Minimum Clarifier Size: = 43.7-feet Diameter

Page 11 4 June 2015

Utilize two (2) 50-foot diameter secondary clarifiers, each providing 1,963.5 sq.ft. of surface area. Locate in space occupied by existing nitrification / denitrification tanks (62-feet x 115.5-feet). The clarifiers and sludge pumping systems can be enclosed with removable covers or with a building structure. The type of enclosure will be evaluated further.

The clarifiers have a SWD of 12’ – 9-1/8” (3.89 m), which is significantly deeper than the existing final clarifiers. This allows for solids to settle and compact for removal from the flow stream.

The sludge removal mechanism consists of a tapered, rectangular unitube header. The tapered design has the cross-section decreasing from the center of the tank, where the sludge volume is the maximum, to the outer perimeter, where the volume is the least.

This results in a uniform sludge withdrawal velocity in the unitube. The header is mounted at a 45-degree angle to physically and hydraulically trap sludge and minimize the potential for re-suspension. Sludge enters the unitube through orifices. The orifice size increases proportionally with the smallest at the tank center and the largest at the periphery. Orifice spacing is a maximum of 30-inches (760 mm), such that a sludge particle travels a maximum of 15-inches (380 mm) to reach an orifice.

Sludge from each clarifier is transferred to a dedicated Return Activated Sludge (RAS) wet well, each containing two (2) pumps. Dual wet wells and pumps provide redundancy and Operator flexibility. Each RAS pump is rated for 2.55 m3/min. @ 5.06 m.

Floating material is swept to a pair of scum wet wells, each equipped with a single pump.

Scum is pumped to the existing final clarifier scum drain line, which flows back to the Headworks. Each scum pump is rated for 0.53m3/min. @ 1.82m.

8. Disinfection:

The existing chlorine contact chamber currently provides 8.0-minutes of HRT @ ADF.

This should be increased to provide at least 30-minutes @ ADF. Additionally, the L:W ratio should be increased as much as practical within the existing tankage, but not less than 10:1, with 40:1 preferable.

Using 1.73 MGD ADF, coupled with 30-minutes HRT, 36,042-gallons of tankage are required. A single existing final clarifier with new walls has an approximate volume of 32,500-gallons at a SWD of approximately 6’-9”. Converting two (2) final clarifiers into parallel chlorine contact chambers, with two (2) new baffle walls running the length of each tank, can easily satisfy the 30-minute HRT requirement at ADF, while providing a L:W ratio of approximately 33:1. Two (2) tanks will provide 24-minutes HRT @ 3.9 MGD PF, which exceeds the 15-minute HRT provided in the Recommended Standards for Wastewater Facilities, 2004 edition.

Continued use of sodium hypochlorite requires partial demolition of two (2) existing secondary clarifier tanks and associated upstream coagulation/flocculation zones for conversion of the tanks to new chlorine contact tanks. Construction of concrete baffle walls in the two (2) tanks, as well as cutting openings in existing walls to provide an inlet

Page 12 4 June 2015 and outlet to each tank, is required for conversion of the clarifiers to chlorine contact tanks. Four (4) new stainless steel weir gates are required for flow splitting, tank isolation and water level control. Sodium hypochlorite piping would need to be extended to the new feed point at the outlet of the new secondary clarifiers.

9. Sludge Processing:

a. Return Activated Sludge (RAS) / Waste Activated Sludge (WAS)

Settled sludge will be removed directly from the floor of the circular clarifier via a rotating unitube manifold and hydrostatic pressure. The manifold from each clarifier will discharge into a separate sludge wet well, each equipped with submersible centrifugal pumps and VFD’s. A magnetic flow meter will be utilized on each sludge Pump Station to allow the Operator to vary the sludge withdrawal rate based on influent flow or other parameters. Sludge pumped from each Pump Station will be directed toward the head end of the anoxic system as RAS, or directed toward the aerobic digestion system as WAS.

b. Aerobic Digestion

WAS will be directed to sludge concentrators. The existing units will be retrofit with new mechanisms. Supernatant will continue to be directed to the WWTP drain piping, while the thickened solids will be transferred to the aerobic digestion tank.

To minimize energy consumption and provide enhanced mixing, the side roll aeration system will be replaced with a fine pore aeration system, similar to the aeration basins.

The blowers required for the aerobic digestion system will be separate from the activated sludge system, as the pressure requirements will vary significantly. A submersible pressure transducer is provided to provide feedback to the WWTP Staff regarding tank level, and to allow automatic speed control of the blowers.

Two (2) blowers, each rated for 20.95 inlet m3/min. @ 0.607 Bar are provided.

One (1) is duty, while the other is standby. VFD’s allow the speed to vary automatically based on digester level, saving energy.

c. Dewatering

New submersible transfer pumps, each rated at 0.76 m3/min. @ 15.8 m will replace the existing pair, which pump stabilized sludge up to the second floor of Control Building 1190. The sludge will be discharged into the existing service (Day) tank. A positive displacement sludge pump, rated for 0.76 m3/min. @ 275 kPa, will feed sludge to a new centrifuge.

Page 13 4 June 2015

The existing centrifuge will be demolished and replaced with a new unit.

Similarly, the polymer make-up and feed system will be demolished and replaced with a new system. The existing conveyors will be reused, as will the existing hopper system. A new water booster pump, rated at 18 m3/hour @ 3.10 Bar, is provided to supply water to the centrifuge and polymer systems. The existing water supply system backflow preventers will be utilized to feed the existing water supply tank.

Page 14 4 June 2015

Appendix A – JEGS and Permit Limits

Appendix B – Plant Operation Information

September/October 2014

Appendix C – Influent and Effluent Test Data

Appendix D – Influent and Effluent Summaries

2. Current Flows and Loadings