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WASTEWATER TREATMENT

PLANT UPGRADE PROJECT

PRELIMINARY ENGINEERING REPORT

& SITE APPLICATION(AMENDMENT OF AN EXISTING SITE APPLICATION)

Mountain Water & Sanitation District

12365 Highway 285

Conifer, CO 80433

NPDES# CO-0022730

Unincorporated Jefferson County, Colorado

MARCH 2012

BY:


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TABLE OF CONTENTS

EXECUTIVE SUMMARY .....................................................................................................................4PLANNING CONDITIONS...................................................................................................................52.1 Planning Area.......................................................................................................................52.1.1 Overview ..............................................................................................................................52.1.2 Geography & Climate ..........................................................................................................52.1.3 WWTP Site ..........................................................................................................................62.1.4 Existing Site Application and Discharge Permit .................................................................62.1.5 PELS ....................................................................................................................................62.2 208 Plan Coordination .........................................................................................................72.3 Growth Areas and Population Trends ..................................................................................82.4 Wastewater Flow Forecasts .................................................................................................82.5 Wasteload Forecasts...........................................................................................................102.6 Summary of Proposed Capacity and Forecasted Loading .................................................11

DESCRIPTION OF EXISTING FACILITIES.........................................................................................123.1 Service Area Features ........................................................................................................123.2 Area Discharge Permits .....................................................................................................123.3 Facilities Layout and Description ......................................................................................123.4 Wastewater Flows ..............................................................................................................133.5 Financial Status and Users .................................................................................................134.1 Compliance ........................................................................................................................154.2 Security ..............................................................................................................................15

4.3 Operation and Maintenance ...............................................................................................154.4 Growth ...............................................................................................................................15ASSESSMENT OF ALTERNATIVES .................................................................................................16No Action .......................................................................................................................................16Optimizing Existing Facilities .......................................................................................................16Interconnecting to Nearby Facilities ..............................................................................................17Upgrade with a New Facility .........................................................................................................175.1 Description .........................................................................................................................17

5.1.1 Membrane Biological Reactor ...........................................................................................185.1.2 Sequencing Batch Reactor .................................................................................................235.1.3 Conventional Activated Sludge .........................................................................................295.2 Design Criteria ...................................................................................................................325.3 Environmental Impacts ......................................................................................................325.4 Land Requirements ............................................................................................................33


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TABLE OF CONTENTS

6.2 Technical Description ........................................................................................................396.3 Environmental Review of Selected Alternative .................................................................436.4 Green Project Reserve........................................................................................................436.4.1 Introduction ........................................................................................................................436.4.2 Component #1: Install WWTP Energy Efficient Process Equipment ...............................446.4.3 Component #2: Anaerobic Sludge Digestion ....................................................................466.4.4 Green Project Reserve Conclusion ....................................................................................486.5 Project Costs ......................................................................................................................496.6 Project Implementation ......................................................................................................516.7 Preliminary Effluent Limits Application and Site Application .........................................516.8 Process Design ...................................................................................................................526.9 Final Design .......................................................................................................................526.10 Discharge Permit ................................................................................................................52

6.11 Miscellaneous Permits .......................................................................................................52ABBREVIATIONS ............................................................................................................................53

TABLESTable 1. Preliminary Effluent Limits .............................................................................................. 7Table 2. Population Growth Estimate ............................................................................................. 8Table 3. Wastewater Flow Forecasts .............................................................................................. 8Table 4. Waste-load Forecasts ...................................................................................................... 10

Table 5. Design Capacity Summary Table ................................................................................... 11Table 6. Cost Estimates for Alternatives ...................................................................................... 35Table 7. MBR Advantages/Disadvantages ................................................................................... 35Table 8. SBR Advantages/Disadvantages..................................................................................... 35Table 9. Conventional Activated Sludge Advantages/Disadvantages .......................................... 36Table 10. Summary of Alternatives .............................................................................................. 37Table 11. Component Summary ................................................................................................... 43Table 12. Project Components ...................................................................................................... 44

Table 13. Current WWTP Power Consumption ........................................................................... 44Table 14. Energy Savings Summary ............................................................................................. 46Table 15. Fuel Savings .................................................................................................................. 48Table 16. Cost Savings ................................................................................................................. 48Table 17. Cost Savings Summary ................................................................................................. 49Table 18. Green Project Reserve Eligible Costs ........................................................................... 49


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TABLE OF CONTENTS

Figure 3. Chart of Alternatives Assessment Options .................................................................... 16Figure 4. MBR Design Flow Diagram .......................................................................................... 19Figure 5. Image of Kubota Membrane Filter ................................................................................ 20Figure 6. Overview of MicroBLOX Package MBR ..................................................................... 22Figure 7. Overview of Fluidyne ISAM Package SBR .................................................................. 24Figure 8. Fluidyne ISAM SBR Process ........................................................................................ 26Figure 9. Overview of Ashbrook Package Activated Sludge System .......................................... 32Figure 10. Conceptual Rendering of Proposed WWTP ................................................................ 39Figure 11. SBR Operational Cycle ............................................................................................... 42


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EXECUTIVE SUMMARY

The Mountain Water and Sanitation District (the District), located in unincorporated Jefferson

County, Colorado, provides municipal water and wastewater service to approximately 1050

people (389 taps). Currently, sewage is collected via a gravity-fed collection system and treated

by a RBC wastewater treatment facility. The existing facility was constructed in the early 1980s.

Although improvements to the plant were made in the 1990s, the facility is not capable of

meeting effluent limits for ammonia. In light of the age of the RBC unit and critical design

constraints that exist with the existing facility, the District has made the decision to initiate

planning activities needed to replace the facility.

The existing WWTP is permitted to treat 100,000 GPD of flow and 366 pounds per day of BOD.

Historically, the WWTP has treated, on average, 46,391 GPD of flow and 117 pounds per day of

BOD. There is potential for the flow to increase by an additional 27% as vacant properties withinthe service area are developed over the next 50 years. The upgraded facility will be rated at the

same hydraulic and organic limits as the existing facility, as there will be enough capacity at the

WWTP to handle the 27% growth within the District.

The alternatives evaluated included taking no action, optimizing the existing facility,

interconnecting to another facility, and upgrading the existing system with a new treatment

process. The treatment processes evaluated consisted of Membrane Biological Reactor,

Sequencing Batch Reactor, and conventional activated sludge process.

The Sequencing Batch Reactor was selected as the preferred alternative because of its capital

cost, small footprint, anaerobic sludge digestion, operation and maintenance costs, and required

amount of operator involvement.

The preferred alternative will result in a number of incremental environmental improvements

over the existing facility. These benefits include greater power efficiency and lower sludge

generation. The environmental benefits are significant and measurable and qualify the project for

the CDPHE Green Project Reserve Program.


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PLANNING CONDITIONS

2.1PLANNING AREA2.1.1 OVERVIEW

The Mountain Water and Sanitation District is located 2.8 miles southwest of Conifer, Colorado,

and covers approximately 640 acres, with roughly 340 of those acres developed and platted. The

District provides potable water and wastewater treatment services to approximately 389 taps.

The current planning area is fixed, and the District does not anticipate increasing the size of the

area to include more properties. Additional flow growth within the planning area is anticipated to

be minimal as the opportunity for growth is limited to the remaining vacant lots. The District

estimates that it will serve approximately 495 taps at build-out (year 2050).

Water consumers within the District are predominantly single-family residences and dischargedomestic sewage to the WWTP. A small portion of the service area is zoned for commercial use

and currently, a convenience store is being served in this area. Discharges to the WWTP from

the existing convenience store consist of domestic sewage. There is a second commercial area

that is currently vacant. It is anticipated that when this area is occupied, all of the discharges

from there will consist of domestic sewage.

2.1.2 GEOGRAPHY & CLIMATEElevations within the District area vary from 9,500 to 8,350 feet. The WWTP site is located near

the lowest section. A gravity collection system conveys sewage from the users to the WWTP.

Pump stations are not required to convey wastewater. The WWTP discharges to an unnamed

tributary to Gooseberry Gulch that runs near the Districts existing WWTP.

Project designs will recognize the need to mitigate cold weather conditions by utilizing below-

grade placements, weather treatment of exposed piping, and installing equipment inside of

climate-controlled buildings. Implementation will also be made for protection of sensitive

equipment from direct sunlight and electrical faults caused by extreme summer heat.


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2.1.3 WWTP SITEThe existing WWTP site is located at 12365 Highway 285, Conifer, Colorado, 80433. Access to

the site is obtained via a private driveway off of Old US Highway 285. The Districts

headquarters and administrative offices share the site with the WWTP. The existing WWTP is

located in the northeast of the northwest of Section 33, Township 6 South, Range 41 West

of the 6th Principal Meridian (39 29 32N, 105 20 46W). The upgraded WWTP will be

located on the same site.

2.1.4 EXISTING SITE APPLICATION AND DISCHARGE PERMITOn June 8, 2007 the WQCD issued a Site Application Amendment and Design Approval Letter

(#3431) for the Districts WWTP. The amendment and design approval permits the addition of a

sodium bisulfite dechlorination system. The letter maintains the permitted hydraulic and organic

loading of 100,000 GPD and 366 pounds BOD/day, respectively.

The Districts most recent discharge permit (CO-002730), was issued in May of 2005. Prior to

2005, the District was not required to meet ammonia limits in the effluent. The 2005 Permit

contained ammonia limits that were to be phased in as part of a compliance schedule. The

District requested a temporary modification of certain conditions in the permit to allow a study

of the aquatic life in Gooseberry Gulch and its tributaries. The Colorado Water Quality Control

Commission approved a Type iii Temporary Modification that extended through December 31,

2011. It is unknown when a new discharge permit will be issued by the CDPHE.

2.1.5 PELSThe District requested and received PELs dated October 18th, 2011 for the unnamed tributary to

Gooseberry Gulch. The PELs are for the same discharge location and volume of effluent as the

existing WWTP. The following is a summary table of the PELs:


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Table 1. Preliminary Effluent Limits

Preliminary Effluent L imits for Evaluation under the Site Approval ProcessDischarge to Unnamed tributary to Gooseberry Gulch

at a Design Flow of 0.1 MGD

Technology Based Limitations

BOD5(mg/l) 45 (7-day average), 30 (30-day average)

BOD5(% removal) 85 (30-day average)

TSS, mechanical plant (mg/l) 45 (7-day average), 30 (30-day average)

TSS, mechanical plant (% removal) 85 (30-day average)Oil and Grease (mg/l) 10 (maximum)

pH (s.u.) 6.5-9.0 (minimum-maximum)Other Pollutants WQBELs

E. coli (#/100 ml) 252 (7-day average), 126 (30-day average)

Total Residual Chlorine (mg/l) 0.019 (daily maximum), 0.011 (30-day average)

Total Ammonia, January (mg/l) 16 (daily maximum), 4.9 (30-day average)

Total Ammonia, February (mg/l) 18 (daily maximum), 5.1 (30-day average)Total Ammonia, March (mg/l) 15 (daily maximum), 4.8 (30-day average)

Total Ammonia, April (mg/l) 14 (daily maximum), 4.6 (30-day average)

Total Ammonia, May (mg/l) 15 (daily maximum), 4.8 (30-day average)

Total Ammonia, June (mg/l) 16 (daily maximum), 4.8 (30-day average)

Total Ammonia, July (mg/l) 17 (daily maximum), 4.3 (30-day average)

Total Ammonia, August (mg/l) 18 (daily maximum), 4.5 (30-day average)Total Ammonia, September (mg/l) 17 (daily maximum), 4.6 (30-day average)

Total Ammonia, October (mg/l) 15 (daily maximum), 4.8 (30-day average)

Total Ammonia, November (mg/l) 15 (daily maximum), 4.7 (30-day average)

Total Ammonia, December (mg/l) 15 (daily maximum), 4.7 (30-day average)

2.2208 PLAN COORDINATIONRegional planning coordination matters between the District, CDPHE, AquaWorks DBO,

DRCOG, and Jefferson County are anticipated to be minimal for the proposed project. The

District proposes to maintain the historical permit limits for the hydraulic and organic capacity of

theexistingwastewater treatmentworks.Manycharacteristicsof theexistingWWTPwill


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facilities have adequate capacity to serve ultimate build out within the planning area for flow and

loading. In January of 2011, the District requested a status update on the review process of the

Utility Report from DRCOG. DRCOG staff stated that a review of the report never took place.Furthermore, DRCOG stated that they no longer review Utility Reports and that that

responsibility has been transferred back to the CDPHE. The Utility Report has therefore not been

officially approved by a regulatory agency. This application for upgrades to the WWTP is

consistent with the findings of the Utility Report. The project should be favorably received by

stakeholders, given that the intent of this project is to upgrade a plant with better and more

reliable equipment without increasing capacity.

2.3GROWTH AREAS AND POPULATION TRENDSThe District does not anticipate adding additional users by increasing the size of the service area.

The only opportunity for growth (additional taps) is through the development of properties

already within the Districts service area. Steep terrain, unfavorable geographic conditions, and

zoning regulations limit the potential for additional taps. The District estimates the potential at

495 taps at complete build-out in the year 2050.

Table 2. Population Growth Estimate

Taps: Residents Per Tap: Estimated Population:

Current 389 2.7 1050 People

Build Out (Year 2050) 495 2.7 1337 People

The potential exists for the District to increase wastewater flow by 27% once complete build out

is achieved. The facility will not exceed hydraulic and organic loading capacities even if the

conservative estimate of 27% growth factor is applied to existing hydraulic and organic rates.

2.4WASTEWATER FLOW FORECASTSIt is possible to quantify current and forecast future flow rates as the District maintains

comprehensive flow and loading records. Complete flow records are included in the Appendix of

this report and are summarized below. Future flow rates were estimated by applying a 27%

growth factor:


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Portions of the Districts wastewater collection system were constructed over a period of five

decades and are susceptible to inflow and infiltration due to their age and condition. Figure #1graphically shows how influent flow can increase during the spring runoff months. There were

three times in 2007 when wastewater influent exceeded the discharge permit limit of 100,000

GPD. Evidence indicates that the three excursions from the discharge permit were due to I&I

artificially inflating the wastewater flow rates. Since then, the District has actively sought to

decrease I&I by making repairs to the collection system. The amount of I&I has substantiality

decreased since these efforts were taken. The amount of I&I for the most recent available runoffperiod (spring of 2011) was negligible.

Figure 1. Influent Flow Rates

0.0000

0.0200

0.0400

0.0600

0.0800

0.1000

0.1200

0.1400

0.1600

0.1800

Flow(M

GD)

WWTP Influent Flow (30-Day Average)

2005

2006

20072008

2009

2010

2011

Permit


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2.5WASTELOAD FORECASTSOrganic loading can be estimated similarly to hydraulic loading. Complete waste-loading records

are included in the appendix of this report and are summarized below. Future organic loading

rates were estimated by applying a 27% growth factor:

Table 4. Waste-load Forecasts

Current Future

BOD Concentration 316 mg/L 316 mg/L

BOD Loading 117 lbs/Day 149 lbs/Day

A graphical representation of the historical BOD loading is shown below. The figure shows that

there were two excursions from the BOD limit, one in 2007 and one in 2009. The cause of the

excursions of BOD (in pounds) is due to increased flows as a result of significant I&I and

variations in BOD sampling techniques. The quantity of flow for those two months was very

high. Reported BOD concentrations vary greatly from month to month as shown in theAppendix. The cause of the wide variation in BOD concentrations is likely due to sampling

methods. The source of wastewater is consistent each month and therefore the District would

expect the BOD quantity (in pounds per day) to remain consistent. The District has implemented

new BOD sampling procedures, including purchasing a composite sampler in February 2011,

with the goal of achieving greater consistency for their BOD concentration results. The influent

BOD results have been more uniform since using the composite sampler.

The historical empirical concentration for BOD averages to 316 mg/l. This is on the high end of

the theoretical concentration rates expected at a wastewater treatment facility. The US EPA

states that BOD concentration in typical residential wastewater ranges between 155 mg/l and 286

mg/l. The 316 mg/l is within reason as the District residents consume less potable water than

average (approximately 40-50 gallons per person per day) resulting in higher concentrations than

in typical wastewater. The data analyzed does not support increasing the BOD concentration forplanning purposes. Furthermore, additional conservatism is built into the design for BOD

loading. The historic loading for the facility has been 117 LB/Day. This is equivalent to 32% of

the permitted loading capacity of 366 LB/Day.


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Figure 2. Influent BOD Loading

2.6SUMMARY OF PROPOSED CAPACITY AND FORECASTED LOADINGThe current facility is rated at a capacity of 100,000 GPD of influent flow and 366 pounds per

day of BOD of organic loading. The upgraded facility will be rated at the same capacity of the

existing facility, maintaining the existing limits of the Site Application. Maintaining the existingcapacities still provides additional conservatism for the basis of design. The design parameters

are summarized below:

Table5. Design CapacitySummary Table

0

100

200

300

400

500

600

BOD(Pounds)

WWTP Influent BOD Loading

2005

2006

2007

2008

2009

2010

2011

Permit


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DESCRIPTION OF EXISTING FACILITIES

3.1SERVICE AREA FEATURESA total of 385 residences, one active commercial facility consisting of a gas station/convenience

store with restrooms, and one unoccupied commercial facility are located within the Districts

service area, for a total number of 389 taps. The District provides potable water supply and

domestic sanitary wastewater treatment services to platted lots. In addition to the platted lots,

there are eight tracts, totaling approximately 35 acres in size, within the District. Due to steepterrain, high multiple residence development cost, and a desire for privacy, three of these tracts

have been developed with only one single family residence. Three of the remaining five tracts

are steeper and less accessible than the developed tracts. It is very unlikely that these tracts will

have more than one single family residence and the forecast for future growth is based upon one

tap for each of these tracts. There are no industrial facilities within the District and the

commercial tracts are anticipated to contribute only domestic wastewater.

3.2AREA DISCHARGE PERMITSA five mile radius map is included in the appendix, showing WWTPs within a five mile radius of

the existing Mountain Water & Sanitation WWTP. The locations of the WWTPs were provided

by DRCOG. The EPA Envirofacts website provides locations of water discharges on their site.

The website lists the following wastewater treatment facilities within the 5-mile radius area:

Conifer Sanitation Association/Conifer Metropolitan District/Village at Conifer

Conifer High School WW Reclamation Plant

Aspen Park Metro District

3.3FACILITIES LAYOUT AND DESCRIPTIONThe existing facility consists of the following principal treatment components. A drawing of the

existing facility is included in the appendix:

Influent Flow Measurement: Ultrasonic flow meter with a 2 parshall flume and


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Rotating Biological Contactor: 57,900 square feet of media area. Two positive

displacement blowers with capacity of 175 CFM.

Solids Contact: Volume of 17,260 gallons. Average water depth of 16.5 feet. Hydraulicdetention time of 4 hours. Return sludge rate of 35 GPM. Design MLSS of 2,000 mg/l.

Two positive displacement blowers with a capacity of 70 SCFM.

Secondary Sedimentation: Final clarifier 8 feet deep. Two return sludge pumps with a

capacity of 35 GPM.

Disinfection/Chlorine Contact Basin: Sodium hypochlorite addition. Contact tank of

3,124 gallons providing 45 minutes of contact time. Dechlorination: Addition of sodium bisulfite prior to discharging.

Aerobic Digestion: Primary tank volume of 11,360 gallons. Secondary tank volume of

17,233 gallons. Solids retention time of 40 days. Two positive displacement blowers of

100 SCFM.

Backup Generator: 30 kW generator with ATS.

3.4WASTEWATER FLOWSThe upgraded WWTP will be designed to treat 100,000 GPD of flow and 366 pounds of

BOD/day. The basis of design is greater than the current flow rates plus a 27% growth factor.

Wastewater flow rates have peaked during spring runoff months because of I&I; however, the

magnitude of the peak flows has decreased over time. A graph of historic hydraulic loading ratesshows how the flow increased during these months. The projected hydraulic loading rates used to

size the upgraded wastewater treatment plant takes reasonable levels of I&I into account. The

hydraulic loading for the plant should continue to decrease over time as sources of I&I are

located and fixed.

There are no combined sewer systems to adversely affect flow rates.

3.5FINANCIAL STATUS AND USERSA ten-year financial projection, created in 2010, is included in the appendix of this report. The

financial records detail the income and expenses for the District including property taxes, user


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Green Project Reserve program) for the proposed project. The principal and interest payments

for these capital improvement projects are included in the 20-year financial projections. It is

likely that user fees and/or property taxes will need to increase to repay future capital projectfinancial obligations.

Also included in the appendix is a user Rate & Charges Schedule for 2011. The Districts rates

are consumptive based with a sliding fee scale that increases along with consumption.

There are two types of users within the District. In 2010 residential users consumed 12,565,000

gallons of potable water and the commercial users consumed 84,000 gallons.


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PROJECT PURPOSE AND NEED

4.1COMPLIANCEThe existing WWTP is not capable of meeting the ammonia limits that appeared in the 2005

Permit, or are set forth in the PELs. Due to the fact that the Type iii Temporary Modification

approved by the Water Quality Control Commission expired on December 31, 2011, and the

District anticipates that a new permit with ammonia limits will be issued by the CDPHE in the

near future, it is anticipated that the Districts WWTP will be deemed to be out of compliance.The intent of the District is to work with the CDPHE staff to develop a compliance schedule that

will allow the District sufficient time to replace the existing facility.

Increasingly restrictive and new limits, specifically ammonia and Total Nitrogen, will continue

to be introduced as the discharge permit is renewed every five years. The District is therefore

looking ahead at future compliance requirements.

4.2SECURITYThe currently facility consists of an RBC treatment building, an operations building, and

uncovered buried concrete tanks, all surrounded by chain linked fence with locked gates. The

existing configuration is adequate to protect the existing assets.

While currently satisfactory, security at the wastewater treatment facility will be improved withthe proposed upgrade project. All buried concrete tanks will be covered with concrete lids or a

building. Locked access hatches will be provided where necessary in the concrete lids to allow

for equipment access.

4.3OPERATION AND MAINTENANCEThe existing treatment facility is operator effort intensive. Maintaining the equipment is aconstant challenge for the facilities operators. Due to the age of the system, replacement parts

are difficult to obtain. Replacing the system with one featuring contemporary technology, such

as PLC control, will automate more functions and ease the demand for operator involvement.

System reliability will be improved and additional preventative measures such as a SCADA


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ASSESSMENT OF ALTERNATIVES

An analysis of potential reasonable alternatives was conducted for this project. The followingalternatives were evaluated:

No action.

Optimizing existing facilities.

Interconnecting to nearby facilities.

Upgrade existing facility with one of the following technologies:o Membrane Biological Reactor (MBR)

o Sequencing Batch Reactor (SBR)

o Conventional Activated Sludge

Figure 3. Chart of Alternatives Assessment Options

NO ACTION

Due to the fact that the WWTP is not capable of meeting the ammonia limits set forth in the

PELs, a No Action alternative is not feasible. Operations and maintenance personnel are also

concerned that the cost to repair or replace critical components of the WWTP would be

TreatmentTechnologies:

AlternativeCategories:

Upgradewith new

facility

MembraneBiologicalReactor

SequencingBatch

Reactor

NoAction

Optimizeexistingfacilities

Inter-connect

Convention-al Activated

Sludge


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meet ammonia and other future discharge permit limits would be prohibitively expensive. This

approach would require replacing critical components of the plant such as the rotating biological

contactor and concrete tanks and also providing additional concrete tank volume to treat forammonia and total nitrogen. Some of the equipment requiring replacement is not manufactured

anymore. Provisions would need to be made to keep the WWTP functional while the

optimizations were made. Retrofitting the facility to optimize its configuration and condition

would be more complicated and costly than starting with new treatment technology.

INTERCONNECTING TO NEARBY FACILITIES

The CDPHE provides direction, in Section 22.4(1)(b)(v), Consolidation Analysis of the

Guidance Document for the Site Location and Design Approval Regulations for Domestic

Wastewater Treatment Works, for determining if interconnecting to existing facilities is feasible.

The guidance document states that only one of five factors is needed to preclude consolidation

and make connecting to an existing facility infeasible. Only applications for new wastewater

treatment facilities must discuss the feasibility of consolidation, therefore excluding thisapplication from this requirement.

Nonetheless, there are a number of reasons that make connecting to an existing facility infeasible

such as expense, distance to the nearest facility, increasing the capacity of an existing facility,

crossing public lands/rights-of-ways, merging service areas, stream flow disturbance, impacts to

water rights, and the need to pump wastewater.

UPGRADE WITH A NEW FACILITY

The most feasible scenario is to replace the existing RBC with a different treatment technology.

The District has the opportunity to implement new technologies developed and improved since

the installation of the original facility. New treatment technologies can allow for a smaller

footprint, greater energy efficiency, simpler operations, greater operational control, and toproduce overall better effluent quality. A number of different treatment technologies are

available. Three options were evaluated for this project, Membrane Biological Reactor,

Sequencing Batch Reactor, and conventional activated sludge. Following are the evaluations of

the alternatives:


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5.1.1MEMBRANE BIOLOGICAL REACTORThe Membrane Bioreactor System evaluated for this project is supplied as a complete packaged

system to take advantage of efficiencies with the manufacture and installation of the system. The

MBR package, the microBLOX system by Ovivo USA, LLC, consists of an influent screening

channel and equalization basin, aerobic sludge, and WAS storage, as well as effluent chlorination

and de-chlorination. The configuration is typical for MBR systems.

The utilization of the membrane provides advanced capabilities for meeting effluent quality

standards. The separation created by a semi-permeable membrane allows the MBR to producehigh-quality effluent. The membrane prohibits solids material from reaching the effluent

channel. MBR systems consist of aerobic sludge manipulation that uses semi-permeable

membranes. The nominal pore size for the alternative analyzed is 0.4 m. This porosity limits

pathogenic flow-through and improves the ability to produce consistent effluent quality.

The microBLOX system is a pre-packaged system that allows for onsite shipment and minimal

physical adjustments once installed. The packaged MBR system consists of the following

operational processes:

Influent fine screening

Equalization Zone / Transfer Pump

KUBOTASubmerged Membranes

WAS Zone Pre-Wired, Factory Tested Equipment

Remote Monitoring Controls

The projects design requirements call for two parallel microBLOX systems, each with a design

capacity of 50,000 GPD (100,000 GPD total) with no additional provisions for maximum flow

rate attenuation. This design promotes redundancy of operations and increased success ofquality effluent. Phasing in the installation of two parallel systems is required to maintain the

ability to treat wastewater while the new facility is under construction. Details of the sequencing

can be found later in this report. The systems operational processes are discussed below.


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Figure 4. MBR Design Flow Diagram

Influent flow Conditions and Fine ScreeningTwo (2) Enviroquip Model FS600 fine screens are supplied for the removal of solids. One (1)

screen is an installed standby. Clear openings range from 2-14mm with max flow rates ranging

from 150-400 gpm.

Screening is designed to meet peak flow rates. Screenings are processed into a continuous bagger

assembly for ease of removal and disposal in a solid waste facility.

Equalization Zone / Transfer Pumps

An integrated 2,480 gal influent storage basin accommodates peak flow and I&I events to

circumvent short-circuiting of above-peak events. Redundancy includes two (2) transfer pumps,

(1d t d1 t db ) ith f df d t f 445 Th t f h l t l


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20,000 mg/l is maintained under constant aerobic conditions. KUBOTA membranes utilize

filtration to separate treated water from the mixed liquor. Air scour Rietschle Elmo blowers (2

duty, 1 standby) are supplied to provide constant aeration of the mixed liquor. The continuousscouring acts as a primary means of anti-fouling of the membranes. Typical operation of

membranes calls for a set permeate period of time, determined by the manufacturer, followed by

a rest function and/or a reverse flow. This alternating operation helps prevent overloading and

buildup on the membrane cartridges.

The membranes themselves are in a parallel arrangement of semi-permeable plates that use apermeate vacuum pump to achieve an optimal flow-through rate. Adjustments are made by the

operator to achieve constant pressure. This feature provides a balance between flow-through

capabilities and membrane fouling due to over-suction.

Figure 5. Image of Kubota Membrane Filter

WAS Zone

An integrated on-board WAS storage zone is provided in the microBLOX package plant. The

estimated storage volume for this project is 2,484 gallons. This basin is utilized as a means to

partially digest and thicken WAS up to an amount of 2-3% solids. Hauling cost is estimated to

beroughly5timeslessthanthatof aconventional activatedsludgeWWTP


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Biological Nutrient Reduction

To achieve nitrification and denitrification, which is necessary for total nitrogen removal, systemcontrols monitors dissolved oxygen levels in the biomass to indicate the changing biological

oxygen demand. Based on the results, the aeration is controlled to maintain low dissolved

oxygen (


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Figure 6. Overview of MicroBLOX Package MBR

OPERATION & MAINTENANCE

Operation of the MicroBLOX MBR is performed through an integral HMI interface panel. The

panel manipulates and monitors the operation of blowers, pumps, flows, & chemical additions.

The manufacturer suggests that the basins be cleaned with a chemical cleaning for organic

fouling 4 times per year and two times per year for inorganic fouling. Chemicals used will

consist of acid and caustic cleaners.

As with any process, a proactive procedure provides optimal performance for continuous quality

treatment. Influent, effluent, and in-basin monitoring of wastewater conditions will allow

trending and predictive measures to be taken to forecast possible interruptions in effluent quality.

A scheduled routine of sludge removal will be required at the intervals deemed necessary.

Chemical Addition

The MBR process will requires the five following chemicals for operations and maintenance:

Alum,topromotetheremoval of phosphorous in thesludge


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5.1.2SEQUENCING BATCH REACTOR

A SBR treatment facility consists of an activated sludge system with most required equipment

and controls supplied by a common manufacturer. There are a number of SBR manufacturers in

the marketplace. This report evaluates the SBR unit manufactured by Fluidyne Corporation. The

Fluidyne SBR Systems features the following major components:

Influent conditioning / sludge storage tanks / integrated anaerobic zone

Anoxic equalization basins (SAM Basins)

Jet motive / wastewater transfer pumps

Jet aspirator aeration system

SBR Basins

Automated solids-excluding decanters

Decant equalization and chlorine contact basins

PLC-based control system

The proposed system consists of two identical process trains, each rated at 50,000 gallons per

day. This configuration provides enhanced operator control and additional redundancy

capabilities. The function and basis of design for each of these project components are discussed

below. Please note that the illustrations below show equipment installed in steel tanks. The

proposed Mountain Water and Sanitation District project would consist of the equipmentinstalled in buried concrete tanks.


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Figure 7. Overview of Fluidyne ISAM Package SBR

*Not shown, the fourth chamber, consisting of an effluent EQ and Chlorine Contact Basin

Influent Conditioning / Sludge Storage Tanks

After influent flow measurement and screening (manual or automatic), raw wastewater will flow

by gravity into the first component of the biological process, the influent conditioning/sludge

storage chambers. These chambers will be constant-level chambers where heavy influent solids

and grit will settle out, similar to a primary clarifier. Here, settleable solids will be converted tosoluble BOD. Underflow baffles will be provided to prevent direct short-circuiting.

A second function of this chamber is to store and concentrate waste sludge. The anaerobic tanks

are designed to provide approximately 90 days of sludge storage, subject to influent conditions.


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Fluidyne has documented significant volatile solids reductions and typical sludge solids

concentrations of 3-4%. This results in an extremely efficient sludge storage system andminimizes the frequency of hauling, which meets the criteria outlined in the Green Project

Reserve program of the State Revolving Fund. Sludge will be removed periodically, based on

observation of stored sludge levels, with a vacuum truck and hauled offsite to a permitted entity.

Anoxic Equalization Tank

Conditioned influent, which is high in soluble BOD, then flows by gravity to the anoxic

equalization basin. The purpose of the anoxic equalization basin is threefold: (1) to retain andequalize peak influent flows, (2) to provide an ideal environment for high rate de-nitrification,

and (3) to act as a selector against filaments.

Jet Motive Wastewater Transfer Pumps

The multi-purpose jet-motive pumps serve three essential functions of the SBR. First, the pumps

act on an intermittent cycle to forward-feed partially treated water into the SBR while

simultaneously acting as Venturi aerators. Second, the pumps cycle water between the SBR and

anoxic basin to denitrify the wastewater. Third, the jet motive pumps feed WAS to the front of

the plant achieved by siphoning a side stream of the sludge. Enough jet motive pumps will be

supplied to provide redundancy.

Aeration System Aspirat ing Nozzles

The motive pump also activates an aspirating jet aerator. The nozzles are located in the SBRbasins. The oxygen delivery system is sized to exceed the calculated oxygen requirements to

accomplish treatment (CBOD and ammonia conversion).

Sequencing Batch Reactor (SBR)

Each batch of wastewater is treated within a cycle within the two SBR basins. Within each cycle

are four distinct phases:

1. Fill / React;

2. Interact / React;

3. Settle; and

4 Decant


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Figure 8. Fluidyne ISAM SBR Process


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The operating parameters for the SBR include an MLSS of 3,000 mg/l, an SRT of 16 days, 9.28

batches per day, power usage of 243 kWh/day, and an MLVSS of 2,400 mg/l.

Disinfection System

Supernatant will be decanted from the SBR basins into a dedicated holding and chlorine contact

tank. Liquid sodium hypochlorite (NaOCl) will be dosed directly into the decant pipe during

each decant period. Initial mixing is provided by the turbulent pipe conditions at the pipe exit to

the holding tank. A chemical metering pump with auto/manual control, capable of providing the

required dose (gallons per hour) of solution, will be used. The time between batches is greater

than 30 minutes, providing adequate contact time between the chlorine and stored effluent.

Effluent will flow from chlorine contact tanks to the discharge to the unnamed tributary of

Gooseberry Gulch by gravity or by pump. Sodium bisulfite (NaHSO3) will be dosed to de-

chlorinate the effluent stream during discharge. If gravity flow can be achieved, an effluent

control valve will be used to throttle the flow of effluent and engage the dechlorination metering

pump.


The Fluidyne ISAM has features that allow for BNR through the modulation of MLSS and React

cycles. Uric nitrogen is removed first by anaerobic process de-nitrification, which converts urea-

based nitrogen into ammonia. The Fluidyne system then allows for nitrification a semi-

anaerobic or anoxic process whereby the ammonia is converted to nitrite/nitrate molecules.

The ISAM allows for chemical alum addition in either the SBR or the effluent tank. Both options

allow for precipitate formation and phosphorous to accumulate in the sludge for ultimate

disposal offsite.


The Fluidyne ISAM is operated by a PLC with HMI manipulation. The process is automatedand allows for operator adjustment to achieve a quality effluent. The ISAM, as with all

wastewater facilities, runs best with daily supervision but provides consistent operation if a

proactive regiment is implemented. A true understanding of influent/effluent and in-basin

conditions will allow the operator to make educated adjustments and predictions for wastewater


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must be removed.

Chemical AdditionThe SBR process will require the addition of the three following chemicals:

Alum, to promote the removal of phosphorous in the sludge

Sodium hypochlorite, for disinfection in the effluent basin

Sodium bisulfite, for dechlorination prior to effluent discharge to the receiving

stream.

5.1.3CONVENTIONAL ACTIVATED SLUDGEWastewater treatment using the activated sludge process has been the stable constant of

wastewater since 1913, and the traditional means of removing the treated water from the

bacterial Bug-laden wastewater was through gravimetric settling. This traditional model of

activated sludge and clarification is a possible alternative for the Mountain Water & SanitationDistrict improvement. The package system evaluated for this alternative is the Ashbrook

Process Systems Groups Package Plant. The Ashbrook system utilizes a consecutive tank

interaction of;

Anoxic Chamber

Aeration Chamber

Mechanical Clarifier

Sludge Holding Chamber/Aerobic Digester

Disinfection

The proposed system consists of two identical 50,000 gallon per day process trains, providing

enhanced operator control and additional redundancy capabilities. The function and basis of

design for each of these components are discussed below:

Anoxic Chamber

The anoxic chamber utilizes RAS recycled activated sludge from the clarifier and introduces it


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The aeration chamber receives the partially treated sewage with a low oxygen reduction potential

and high oxygen demand. The process step utilizes consistent blower operation through course

diffusers as mixing and oxygen transfer mechanisms. The system incorporates a permanent in-basin air piping that is connected to two (2) blowers (1 duty, 1 standby).

The aeration basin has a steady state design for a MLSS concentration of 3,000 mg/L with a

sludge age of approximately 12 days. The lower SRT helps prevent against unwanted micro-

organisms that can impede the clarification process. The Diffuser submergence of 8.5 feet allows

for optimal oxygen transfer.

Mechanical Clarifier

The circular mechanical clarifier utilizes scum removal rotation, support bridges and a drive unit

to collect the activated sludge in a stilling well. The activated sludge is returned to the anoxic

basin through an airlift alongside the scum collections. The clarifier is equipped with adjustable

V-notch weirs and scum baffling.

The RAS is returned to the anoxic basin at a concentrated value through an airlift system that

offers the aerobic sludge a little respite before being exposed to an elongated anoxic period.

Sludge Holding Chamber/Aerobic Digester

Integrated within the package plant, is an aerobic sludge digester with the holding capacity of

roughly 16 days storage. Aerobic digestion is achieved with course air diffusers. Supernatant isthen decanted back into the wastewater flow stream.

Disinfection/Dechlorination

A single basin with a 2,000 gallon capacity is supplied at the end of the Ashbrook package

system for disinfection. Chlorine is delivered by a tablet dispenser. Effluent would be de-

chlorinated with a tablet dispenser.


The traditional activated sludge model allows for multiple zones of wastewater treatment but

requires the cycling of water through multiple zones multiple times before true treatment is


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progressions are required to achieve high quality BNR.

Phosphorus removal is handled with the addition of alum in the aeration basin. Phosphorous thenaccumulates in the WAS for removal off-site.


Conventional plant designs require daily inspection and a proactive maintenance regimen to

achieve optimal plant performance. Monitoring of influent conditions helps achieve peak plant

performance as well as in-basin and effluent monitoring for key wastewater indicators such as

MLSS, pH, alkalinity, COD, BOD, and temperature. Annual drainage and inspection of diffusers

is recommended to decrease the risk of blockage. Pumps and blowers are subject to the

manufacturers O&M requirements.

Waste-activated sludge will need to be removed from the WWTP at incremental time periods to

allow for future sludge growth and proper MLSS concentrations within the plant.

Chemical Addition

The activated sludge process will require the addition of the following three chemicals:

Alum, to promote the removal of phosphorous in the sludge

Sodium hypochlorite, for disinfection in effluent basin (tablet dispenser)

Sodium bisulfite, for de-chlorination prior to effluent discharge to the receiving

stream


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Figure 9. Overview of Ashbrook Package Activated Sludge System

5.2 DESIGN CRITERIADesign criteria for each of the three alternatives analyzed, such as anticipated influent and

effluent characteristics, basin sizing, pumping requirements, hydraulic retention time, solidsretention time, and sludge production, are included in the appendix of this report. Each

equipment manufacturer has included design criteria within its proposal. Additionally, equipment

data sheets and vendor information is included.

5.3 ENVIRONMENTAL IMPACTSThe proposed project will result in net improvements to the environment. The existing facility is

not designed for treatment of ammonia and total nitrogen. The new facility will be designed

utilizing todays available BNR, phosphorous removal, and automated technology and will treat

wastewater to a much higher level than the existing facility.


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example, the new WWTP will be designed to emit fewer odors than the existing facility.

It is anticipated that there will be unavoidable impacts during the implementation of the project,as is consistent with the construction of most public works projects. The District will do its part

to decrease these impacts to the lowest level possible by implementing measures such as

following runoff best management practices, limiting the times construction activities can take

place to daytime hours, and not disturbing any historic or architecturally significant features.

Work is not being proposed in wetlands for any of the alternatives. The existing effluent

discharge line will be reused, allowing the District to avoid having to work in the area of the

unnamed tributary to Gooseberry Gulch.

5.4 LAND REQUIREMENTSThe upgraded WWTP will be located on the same site as the existing facility, generally within

the limits of the existing chain link fence. Acquiring new property will not be required for thisproject. Planning will be required to locate all new construction on the property while still

maintaining the function of the existing facility.

The area used as the access drive and parking lot for the District will likely be required for

construction staging purposed during the build phase of the project. The area will be restored to

its original condition once the project is complete.

5.5 CONSTRUCTION ISSUESThe most significant construction problem anticipated with this project is maintaining operation

of the existing WWTP while the upgraded WWTP is being constructed. This problem is

applicable for all three alternatives reviewed.

A general phasing plan has been developed to best manage the process of maintaining

wastewater treatment capabilities throughout the duration of the project. The following primary

steps will be followed:


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Phase II I: Install Train #2 in the area made available by removing the existing WWTP.

Commence use of both trains.

This phasing approach will require that the system treat wastewater for a period of a few months

using one 50,000 GPD train while the existing plant is decommissioned and the second train is

built. The District believes that one train will be adequate to treat the volume of wastewater for

that temporary period. The historic average daily flow for the past five years has been 46,391

GPD. This number continues to decrease as the District makes repairs to its collection system,

decreasing the amount of I&I that enters the system. Over the past six years, the District hasmade significant progress reducing I&I from entering the system, as shown on Figure 1. I&I only

occurs during spring runoff months and as Figure 1 shows, the additional flow caused by I&I

ends by July of each year. The District anticipates that it would run on one train only during

periods of low I&I.

Additional construction problems may present themselves as the design of the project progresses.It is anticipated that bedrock will be encountered during excavation. During final design, the

District will evaluate the benefit of installing a lift station to decrease the excavation required for

the tanks. Provisions will need to be made to mitigate these problems to the greatest degree

possible. Additional potential construction problems will be similar for each of the three

alternatives analyzed.

5.6 OPERATIONAL ASPECTSThe District employs a Superintendent (Class A Operator License), Assistant Superintendent,

and Operator-in-Training, who maintain the existing facility. Maintaining the existing facility is

a very time-intensive process due to its age and process configuration. The upgraded plant will

require less operator involvement than the existing facility.

The MBR provides tertiary treatment (filtration) of the treated water which requires substantial

energy. It is expected that the MBR alterative would be significantly more expensive to operate

due to its power consumption. This system will require the highest level of operator involvement.


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SBR and MBR. This system will require periodic inspection and cleaning. This system also

generates the most amount of sludge.

5.7 COST ESTIMATESThe following is a high order magnitude cost estimate for each alternative:

Table 6. Cost Estimates for Alternatives

Alternative #1 Alternative #2 Alternative #3Equipment $1,300,000 $269,200 $894,000

Other Costs $1,300,000 $1,730,800 $1,356,000

Total: $2,600,000 $2,000,000 $2,250,000

5.8 ADVANTAGES/DISADVANTAGESThe following is a summary of the advantages and disadvantages of each alternative:

Table 7. MBR Advantages/Disadvantages

Advantages Disadvantages

Delivered as a packaged unit High capital costs

Uninterrupted quality effluent due to

physical nature of the membrane.

High power cost due to continuous blower and

permeate pump operationHigh Quality BOD, NH3 Removal Full enclosure in building required

Lower probability of coarse diffusers

plugging

Lower oxygen transfer rate due to coarse

diffusers

Increased MLSS concentration >20,000 mg/L

(smaller footprint required)

Chemical cleaning of membranes required

utilizing concentrated acids and bases

Smaller volume of sludge produced Possible membrane fouling

Requires influent lift stationRequires replacing membranes

Requires greater periodic maintenance

Purchase and disposal of cleaning chemicals


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SBR, eventually causing poor settleability.

Reduced amount of sludge generated and

ability to store sludge

Requires buried concrete tanks

No influent lift station required Does not come shipped as a packaged unit

Lower electrical consumption

No in-basin moving parts or maintenance

required

High level of automation

A number of green project reserve qualifying

elements

Innate anoxic/aerobic patterns for high level

of total nitrogen reduction

Provides internal biological buffering that

resist system upsets

Only a small operations building is required

May be able to decrease excavation by

installing lift station.

Table 9. Conventional Activated Sludge Advantages/Disadvantages

Advantages Disadvantages

Low level of operation understanding

required

Prone to operator errors and system upsets

Comes shipped as a packaged unit Requires influent lift station

Air diffusers prone to foulingRequires full enclosure in building

Requires influent lift station

Requires periodical draining of tanks to inspect

and clean

Large HRT required to cycle water repeatedly

for diminishing gains in overall quality

High degree of mechanical maintenanceHigh cost of long-term parts replacement

5.9 SUMMARY OF ALTERNATIVES


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Table 10. Summary of Alternatives

Section Item

Membrane

Biological Reactor

Sequencing Batch

Reactor

Conventional Activated

Sludge5.1 Description Ovivo USA Fluidyne Ashbrook Simon Hartley

5.2 Design Criteria Hydraulic Loading = 100,000 GPD & Organic Loading = 366 PPD

5.3 Environmental Impacts Similar Impacts

5.4 Land Requirements Smallest Footprint Medium Footprint Largest Footprint

5.5 Construction Problems Similar Level Anticipated

5.6 Operational Aspects Difficult to Operate Standard Effort Increased Effort

5.7 Cost Estimates Most Costly Least Costly Medium Cost

5.8 Advantages Effluent Quality Cost-effective Shipped Complete

Disadvantages Costly Buried Tanks Required Full Building Enclosure


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SELECTED ALTERNATIVE

6.1JUSTIFICATION OF SELECTED ALTERNATIVEThe versatility and innovation of Sequencing Batch Reactors has shown a SBR to be the most

suitable to meet the needs of the District. The advantages of using a SBR can be measured both

in monetary and nonmonetary value. The first determining factor is cost. The direct cost

comparison of SBRs to membrane filters and activated sludge designs show that SBRs have the

lowest capital and ongoing expenses. The greatest gain of the membrane technology is apermanent barrier that prevents solids from being inadvertently discharged, but this benefit does

not merit the incremental cost incurred.

The next determining factor is footprint and space availability. A package design SBR can utilize

the space in a compact efficient manner and can eliminate the need for additional sludge storage.

This in-line sludge handling adds an additional advantage for SBR design because it does not

require further tank volume or handling equipment. The SBR has a sludge reducing capability in

the form of anaerobic digestion, which requires less electrical and labor cost than a conventional

WWTP and a membrane design.

A measureable monetary value is electrical consumption savings. The design calculations

provided by SBR designers show a more efficient oxygen transfer rate per pound of BOD

treatment. The lower electrical cost comes from multiple areas of saving: aeration operationalstrategies, sludge treatment, sludge storage, and volume of sludge. All four of these areas have

advantageous properties that are more prevalent in an SBR design than the other alternatives.

A measurable savings will take place in the manual hours needed to maintain the SBR. This is

due to the high level of automation available through PLC operated controls, floats, ORP and/or

oxygen in-line measuring devices. Further, the SBR does not require maintenance of membranesor diffusers.

There are Green Project properties with the SBR design that are not realized by other

technologies. The combination of sludge handling, manual labor savings, and reduced electrical


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removal. The SBR process results in biological nutrient reduction with minimal operator

intervention. The SBR design provides a number of tools for operational manipulation to develop

optimal operational settings that are not part of the design of the alternative plants.

The attributes of the SBR application exceeds the benefits of the alternative forms of treatment.

The District can expect to see measurable gains in WWTP treatment operations, initially and

over the course of the plants life. It is anticipated that the District will realize a number of other

non-measurable characteristics about the proposed SBR design that will result in more efficient

time usage, higher quality effluent production, and overall improved sustainable practices.

Figure 10. Conceptual Rendering of Proposed WWTP

6.2TECHNICAL DESCRIPTIONTh dWWTP d i f h M i W dW S i i Di i ill


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The SBR process will consist of a series of four tanks. The first basin is an anaerobic selector

tank that performs multiple functions. The anaerobic tank acts as a trash trap and sludge settlingtank. Approximately 30% of the BOD available in wastewater is in the form of suspended solids.

The solids are removed gravimetrically in the anaerobic tank and settle to the bottom of the

basin. There is no functional mixing of this basin except that of the inflow and mild exit

turbulence. The lack of turbulence allows for a high degree of compaction on the basin floor,

thereby promoting anaerobic growth. The basin is always full; therefore, the amount of water

exiting the tank equals the water entering the tank.

As the solids entering the anaerobic tank are digested, concentrations of solids are reduced. The

exit flow carries the liquid with lower BOD and TSS into the next basin. The anaerobic process

reduces organics to either ethanol or methane gas, which is passed into the second basin through

a baffled overflow. Contrary to common expectations, the anaerobic tank does not typically

produce odors. Odors that are produced are quickly dissolved and carried into the aerobic

portion of the SBR, where they are oxidized into it less noxious forms. An example would behydrogen sulfide (H2S), which is commonly described as the rotten egg smell. Because of the

hydraulic profile of the SBR, the dissolved gases are put into a high aerobic environment before

being released to atmosphere. The H2S is converted to sulfate or sulfite (SO4 or SO3) or

organically digested by microbes by metabolic processes.

The internal baffles and the lack of mixing within the anaerobic basin allow for coagulation of

fats and oils to accumulate at the top 6 to 12 inches of surface water, often forming a mat ofhigh-energy grease. This mat is not detrimental to the process and actually, over time, can

produce a sustainable source of BOD to sustain organisms during low events. The baffled section

of the anaerobic tank functions as a trap for grease and adequately prevents it from reaching the

SBR in large quantities. Grease in large quantities can disrupt the settleability of MLSS and

cause upsets in effluent quality. Trapping grease in the anaerobic tank allows it to be either

digested anaerobically or hauled off site.

The second basin, the anoxic tank, is an equalization basin that receives its incoming flow from

the anaerobic basin. The partially reduced, solid removed wastewater has soluble characteristics

thatare ideal for initial aerobic treatment. In thisbasin,MLSSreactswithwastewaterunder ideal


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tank in two locations: 1) forward feed pumping and 2) return mixing.

Each anoxic basin houses one-jet motive pumps that forward feed the anoxic slurry into the thirdbasin, known as the SBR reactor. The anoxic and SBR reactor tanks are designed so that for

every gallon of MLSS wastewater slurry moved forward, one gallon of return MLSS wastewater

flows back through an overflow weir. This feature allows for continual cycling of MLSS into the

anoxic zone.

The jet motives perform multiple functions. The first function is pumping the wastewater from

the anoxic tank to the SBR reactor and the resulting overflow that mixes the anoxic basin. Thesecond function is to aerate the SBR. Aeration can be executed with aspirating nozzles or the

use of pressured air in a jet header manifold. The third function is for WAS conveyance. A

bleed off line of the header in the SBR reactor is operated intermittently to remove a portion of

MLSS from the SBR reactor. This feature conveys the aerobic sludge back to the anaerobic basin

where it settles and is digested by anaerobic organisms. It is estimated that 50% of the volatile

organics are removed, reducing the overall sludge hauling cost.

Once MLSS enters the third and largest basin, it progress in an aerobic/anoxic/static cycle that

facilitates microorganism growth, particulate uptake, and sewage treatment. This process either

progresses in the SBR or can be diverted back into the anoxic basin for cycling back into the

SBR reactor basin. The process of SBR reactor/anoxic tank interaction is called interact mode.

The isolated mixing process of the SBR is called the react mode.

The purpose of the aerobic/anoxic/static cycle is to achieve maximum BOD removal with

minimal aeration cost. The aeration mode facilitates the oxidation of nitrogen ammonia into a

less toxic nitrate/nitrite combination. Nitrate can still be hazardous and needs to be converted

into nitrogen gas to meet the PELs and minimalize effects on biological factors downstream. To

achieve this objective, wastewater reaches an anoxic stage wherein the nitrifying bacteria will

utilize the oxygen bound to nitrogen in nitrate (NO3) and produce nitrogen gas (N2) as a wasteproduct. Nitrogen gas makes up 78% of the earths atmosphere. The static operation is

considered an energy savings mode whereby the available dissolved oxygen is consumed. The

microscopic bacteria work together to achieve an ecosystem network of interconnecting

organismsthatusewastewaterastheirbasefoodsource.Themanipulationof thisecosystemby


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decanted out of the SBR reactor. Surface scum is prevented from leaving the SBR reactor by the

decanting method. The discharged volume progresses through a siphon and into the fourth tank,

an effluent equalization/chlorination basin. In this tank, a minimum of 30 minutes of chlorinecontact time is achieved. The water leaving the chlorine contact tank is de-chlorinated with

sodium bisulfite prior to final discharge to the unnamed tributary to Gooseberry Gulch.

After decanting is complete and the SBR reaches bottom water level, the PLC is signaled

through float or ultra-sonic level transducers to begin the fill cycle. The waiting water in the

anoxic basin is pumped into the SBR until the overflow weir spills water back into the anoxic

basin, allowing for continual pumping and aerating. The fundamental cycle of this SBR design isinteract/settle/decant/fill/interact. This, in combination with the anaerobic basin, makes for a

highly effective and efficient treatment process.

Supernatant is decanted to the effluent equalization/chlorine contact tank where a minimum of

30 minutes of chlorine contact time is achieved. Finished effluent will either be pumped or flow

by gravity to the unnamed tributary to Gooseberry Gulch.

This diagram below shows the anoxic/SBR reactor interaction cycle.

Figure 11. SBR Operational Cycle


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6.3ENVIRONMENTAL REVIEW OF SELECTED ALTERNATIVEThe proposed project involves replacing an existing WWTP with a system that will provide a net

benefit to the environment. The upgraded facility will be located on the same site as the existingfacility. Due to the extremely unlikelihood that any long-term incremental impacts to the

environment will be made with this project, the District believes it qualifies for a Category

Exclusion from the Environmental Assessment requirements.

The plant currently discharges to an unnamed tributary to Gooseberry Gulch via a PVC line that

originates at the existing WWTP and terminates in the swale of the gulch. This PVC line will be

reused with the project. The discharge area of the line will not be disturbed and therefore,

impacts within the wetlands, riparian area, and natural areas (if present) will be avoided.

6.4GREEN PROJECT RESERVE6.4.1 INTRODUCTION

The purpose of this section is to summarize and justify the eligibility of certain components of

the Mountain Water & Sanitation Districts wastewater treatment system upgrade project for the

CDPHEs Green Project Reserve program. The CDPHEs GPR sets aside a minimum of 20% of

SRF funding for the purpose of funding green infrastructure, water or energy efficiency

improvements, or other environmentally innovative activities.

The District plans on constructing a facility that will have two components that meet or exceed

the requirements of the GPR program:

Table 11. Component Summary

Part Category Section Item Business Case

Component #1 Energy

Efficiency

3.2-2 Reduction in Energy Consumption

(savings greater than 20%)

Categorical Eligible

Component #2 EnvironmentallyInnovative

4.5-5b Significant Reduction in Residuals Business CaseRequired

Component #1 is categorically eligible for the GPR program. This report will therefore


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Table 12. Project Components

Part Item

Component #1 Install WWTP process equipment that consumes less energy to treat the wastewaterComponent #2 Install anaerobic digestion to decrease biosolids generation

6.4.2 COMPONENT #1: INSTALL WWTP ENERGY EFFICIENT PROCESS EQUIPMENTEnergy efficiency is defined by the Green Project Reserve Program as the use of improved

technologies and practices to reduce the energy consumption of water quality projects, use

energy in a more efficient way, and/or produce/utilize renewable energy. The Districts existing

wastewater treatment plant was installed approximately 30 years ago. The proposed project will

use wastewater treatment process equipment that will consume less energy than the existing

facility by 1) using biological processes that require less energy and 2) consist of equipment that

is more efficient than the existing equipment. This section will show how at least a 20% energy

savings is achieved over current usage.

The District maintains records of the power consumed by the existing wastewater treatment

facility. These records are used to determine existing power demands as follows:

Table 13. Current WWTP Power Consumption

Item

Approximate

Consumption(monthly) Unit Cost Unit Price

Monthly Base Rate 1 $ 30.00 LS $30.00

Service Charge 15,000 $ 0.06363 kWh $954.45

Energy Charge 30 $ 11.60 kW $348.00

Total: $1,332.45

The District spent $15,913.56 for electricity at the WWTP in 2010.This checks with the annual cost of the monthly estimate (12 x $1,332.34 = $15,989)

Power records include consumption of the existing WWTP and district office.

Must therefore deduct the power consumed by the District office for this evaluation.


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Notes:

1) Energy Information Administration. 1995 Commercial Buildings Energy Consumption Survey

The proposed SBR treatment utilizes a combination of energy efficient processes to achieve an

energy efficient process. The Fluidyne ISAM is a four-basin package system that uses gravity to

feed wastewater into an anaerobic selector. This anaerobic chamber results in a passive process

that reduces the solid content of the wastewater stream by 30% or more. The solids are digested

over time by obligate anaerobic bacteria without any energy expended by the user. Anaerobic

digestion is preferable to an aerobic digestion system because electricity is required to power the

blowers required to perform aerobic digestion.

The second in-line basin, an anoxic tank, has an interact period with the aerated wastewater

returned from the SBR reactor. The anoxic conditions of the basin naturally select for specific

bacteria that treat the waste stream for biological nutrient removal, including nitrogen. There is a

submersible pump within the anoxic basin that forward-feeds the now partially treated waste

stream into the aerobic portion. Up to this point, raw sewage has been partially treated without

requiring any energy.

In conventional WWTP design, it common for a pump to only perform one function such as the

forward feed of water/sludge, aeration/mixing, return flow, or sludge removal. The Fluidyne

SBR design uses a single motive pump to perform 3 different functions to save on upfront capital

cost, long term maintenance, and operating cost. These functions include forward feed,

aerating/mixing, and WAS recirculation, saving capital and energy costs. The motive pump willbe regulated by a VFD to further improve the efficiency of the pumps, and closely match the

pumps output to actual demand. The current WWTP design does not use VFDs to regulate

motor output.

An additional energy savings feature included with the SBR design is the use of ORP sensing.

This capability allows the operator to monitor the demand for oxygen, preventing over-aeration

in the SBR reactor. The operator will be able to automatically perform the feature by creating

setpoints in the PLC.

The process design calculations from Fluidyne (included in the appendix) estimate the cost


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increasing the total plants consumption to 304 kWh/day.

The power consumption calculation by Fluidyne is based off of the design flow of 100,000 GPD

with a BOD concentration of 374 mg/L. The calculations by Fluidyne need to be adjusted to

make a direct comparison to the actual historic flow rate of the facility, 46,391 GPD, to

determine if a 20% power savings will be achieved.

Table 14. Energy Savings Summary

Existing

Facility Proposed Facility

Monthly

Cost Savings

Energy

Savings

Daily Demand 304 kWh/Day

Monthly Demand 9,120 kWh

Monthly Demand

(adjusted for flow)

4,231 kWh

Service Charge Rate $0.06363 kWh

Monthly Service Charge $269

Energy Charge Rate $11.60 kWMonthly Energy Charge $400

Monthly Cost $1,165 $669 $496 42%

The energy savings realized with the installation of the SBR process of approximately 42% is

greater than the 20% needed to be considered categorically eligible for the for the GPR program.

6.4.3 COMPONENT #2: ANAEROBIC SLUDGE DIGESTIONEnvironmentally innovative projects are defined by the Green Project Reserve Program as those

that demonstrate new and/or innovative approaches to delivering services or managing water

resources in a more sustainable way. The Mountain Water and Sanitation District will meet this

objective by significantly reducing the amount of biosolids generated by the new facility and

mitigating negative environmental impacts, such as those generated by hauling of the sludge.

Section 4.5-5b states that treatment technologies or approaches that significantly reduce the

volume of residuals, minimize generation of residuals, or lower the amount of chemicals in the

id l b li ibl f th GPR A b i i i df thi ti d


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Numerous wastewater facilities, including the RBC currently installed at the District, utilize

aerobic digestion as a means to reduce the volume of sludge by repeatedly over-aerating the

WAS in an attempt to burn up the residual organic pollutants. This is a diminishing-return

operation that severely limits the overall efficiency of any WWTP. The Fluidyne SBR utilizes an

in-line anaerobic selector as a sludge storage basin as well as a sludge digester. The anaerobic

action digests the sludge, reducing the volume. Also, the sludge is compacted upwards of 3-4%

solids through gravimetric settling. To achieve these concentrations, conventional plants must

enlist the use of costly belt presses and drying pits. Conventional approaches require space,

labor, energy, and substantial capital cost. Digestion and compaction improves the longer thesludge is retained in the anaerobic basin, decreasing the need for hauling.

Conventional aerobic digestion is not an efficient method because it requires aerobic bacteria to

digest aerobic bacteria. This process requires digestion of existing bacteria so that its bio-

nutrients can be broken down into simpler compounds. Bacteria, when unable to self-sustain,

enter into a sporocyte stage that resists degradation or consumption. Fluidyne avoids this

situation by putting aerobic bacteria into an anaerobic basin so that they can be killed more

efficiently. Fluidynes approach does not require electricity to digest and compact the bacteria.

Fluidynes approach allows the organic molecules to be dissolved and then recycled throughout

the treatment process. This strategy provides a more thorough treatment and a greater by-product

release of CO2, H20 and N2. These compounds are non-hazardous when released into the

environment and pose less of an environmental risk than their alternative forms, CH4 and NH3.

The Fluidyne calculations estimate that the new treatment facility will generate 256 gallons per

day (93,440 gallons per year) of biosolids for 100,000 gallons per day of flow. Adjusting the

sludge generation for 46,391 GPD of flow decreases sludge production to 43,348 gallons per

year. This calculation adjustment is needed to make an equivalent comparison to before and

after sludge generating amounts. The new plant will require sludge to be hauled about 9 times

per year if the District continues to use trucks with a capacity of 5,000 gallons.

The net impacts to the environment are significant and measureable. The most significant

impacts are those mitigated from hauling the sludge. The current process is inefficient and the

process yields asignificantamountof residuals thatmustunnecessarilybehauledoff and


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Table 15. Fuel Savings

Item Number Units

Trips per Year (current) 35 TripsTrips per Year (proposed) 9 Trips

Trip Length (roundtrip) 172 Miles

Miles per Year (current) 6,020 Miles

Miles per Year (proposed) 1,548 Miles

Vehicle Fuel Consumption 10 MPG

Yearly Fuel Consumption (current) 602 Gallons

Yearly Fuel Consumption (proposed) 155 GallonsYearly Fuel Savings 447 Gallons

Miles Saved (yearly) 4,472 Miles

The cost savings realized by decreasing the amount of residuals generated are considerable. It

costs $400 per load to haul sludge offsite. The District can save considerable money by

decreasing the frequency of hauling:

Table 16. Cost Savings

Item Number Units

Trips per Year (current) 35 Trips

Trips per Year (proposed) 9 Trips

Cost per trip $400 Dollars

Hauling cost per year (current) $14,000 DollarsHauling cost per year (proposed) $3,600 Dollars

Yearly Savings $10,400 Dollars

The annual cost savings do not show the additional capital cost savings that would occur by not

having to construct additional sludge holding facilities and aeration capabilities.

6.4.4 GREEN PROJECT RESERVE CONCLUSIONThe incremental green benefits realized by upgrading the existing wastewater treatment plant

to a Fluidyne SBR are significant, both environmentally and financially. The environmental

benefits include, but are not limited to:


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Smaller treatment works footprint

Reduced odor from anaerobic sludge digestion

Reduced biological nutrients in effluent discharge Improved receiving stream quality

The financial benefits achieved by improving sustainability are significant. Those savings are

summarized below:

Table 17. Cost Savings Summary

Item Amount

Category #1 $5,892/year

Category #2 $10,400/year

Total: $16,292/year

Given the substantial environmental and economic benefits, the District believes that $870,327

of the project costs is eligible for the Green Project Reserve Program. The costs are detailed asfollows:

Table 18. Green Project Reserve Eligible Costs

Item Cost

WWTP Equipment Package $292,600

Concrete Tanks $290,000Excavation $25,000

WWTP Treatment Building $40,000

Equipment Installation $125,000

Engineering Design Fees $97,727

Grand Total $870,327

The project therefore qualifies for inclusion into the GPR program by meeting the requirementthat at least 20% ($400,000) of the projects costs qualify for the program.

6.5 PROJECT COSTS


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2 Site Construction

Site Clearing 1 LS $7,500

Rock Breaking/Crushing 1 LS $75,000

Excavation 1 LS $25,000

Bedding 1 LS $20,000

Backfill & Grading 1 LS $15,000

Site Piping 1 LS $45,000

Site Restoration 1 LS $7,400

Erosion Control 1 LS $5,000

Demo Existing WWTP & Phasing of New WWTP 1 LS $125,000

Remove and Replace Chain Link Fencing 1 LS $25,000

3 Concrete

Precast Tanks (ISAM x 2, SAM x 2, EQ x 1) 1 LS $175,000

Cast in Place Concrete (SBR

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