26-8635_Exhibit_-_Tech_Memo_#9_Capacity_Expansion_Considerations_February_2011.pdf

TECHNICAL MEMORANDUM No. 9

To: Pete Schalt, PMP, Project Manager Date: February, 2011 Subject: Capacity Expansion Considerations

1.0 INTRODUCTION

The SCWRF has a permitted capacity of 16 MGD (maximum month average daily flow) along with the ability to handle influent flows as high as 40 MGD (wet weather peak) through the preliminary treatment facility prior to flow equalization. The ability to handle the wet weather peak flows assumes use of both of the preliminary treatment facilities. At the time of the last construction project, Collier County indicated to the neighbors this project would be the last major construction project on the site, other than a possible building in the area north of the aeration basins where the site was filled and planted with grass.

One opportunity which exists for capacity expansion at the SCWRF is the potential conversion of a portion of the aeration basin passes to MBR (membrane bioreactor) mode of operation.

Much of the work in such a conversion would be the installation of new equipment in the aeration basin passes which would be converted, thus not requiring construction of new aeration basins. The remaining components of the facility expansion would be those which have the potential of being constructed inside a building located to the north of the aeration basins. This Technical Memorandum considers this possibility, while identifying the likely scope of the project from a technical standpoint as well as “good neighbor” standpoint.

2.0 EVALUATION

The existing activated sludge facilities at the SCWRF consist of 14 aeration basin passes along with associated equipment such as blowers. Each aeration basin pass has a total volume of 500,000 gallons and a maximum month average daily flow capacity of 1.15 MGD, for a total volume of 7 million gallons and 16 MGD with 14 aeration basins in service. The dimensions of each aeration basin pass were provided to OVIVO in order for them to provide recommendations as to potential capacity in the event some of these aeration basin passes were converted to MBR using their equipment [other MBR system manufacturers would be consulted if this concept were to proceed to the next step of preliminary design, although anticipated to have similar capacity ratings]. Their recommendation was that the capacity could be rerated to 2.0 MGD per aeration basin pass (maximum month average daily flow) and 4.0 MGD per aeration basin pass (peak hourly flow). This increase in capacity factors in that a portion of each basin would be taken up for housing the submerged MBR membrane modules. The existing facility was sized for a peak equalized flow of 23 MGD. In the event of a large rain event, it was anticipated that this flow could be handled by ten out of fourteen aeration basin passes, with the other four passes used in the storm flow equalization mode of operation. For this reason, the peak hourly flow capacity of the conventional activated sludge portion of the system could remain at 23 MGD even with conversion of aeration basin passes to MBR.

As way of an example, if a single aeration basin pass was converted to MBR, the peak wet weather flow for the facility would be increased by 4 MGD, as the remaining aeration basins would retain their hydraulic capacity of 23 MGD, while the new MBR basin would have a peak capacity of 4 MGD. With regard to maximum month average daily flow capacity, conversion of a single aeration basin pass would only provide a net increase in capacity of 0.85 MGD [2 MGD for the MBR mode minus 1.15 MGD for the conventional mode]. Thus the conversion to MBR could be configured such that it would add a considerable amount of hydraulic capacity during peak wet weather conditions as the clarifiers and filters would retain their current capacity while additional capacity is added through the MBR system. One way to best utilize this potential for increasing capacity would be to construct new preliminary treatment facilities for the MBR system equal to the peak capacity of the MBR system as a stand alone system and to construct disinfection facilities for that same capacity. This also seems most appropriate as the MBR system would require finer screening than the existing portion of the facility.

Another way of looking at the peak hourly flow capacity, following conversion of some of the aeration passes to MBR, is that there would be more reserve capacity in the event of an equipment malfunction occurring during the most stressed conditions which the facility would experience. A comparison between hydraulic loading rates on the aeration passes remaining in conventional mode of operation, secondary clarifiers, and effluent filters is provided in Table 1.

Figure 1 provides a comparison of the capacity of the existing facility versus which might be achieved through conversion to MBR. For the purpose of the remainder of this evaluation, it will be assumed that conversion of 4 aeration basin passes are converted to MBR mode. This would provide a net increase in maximum month average daily flow of 3.5 to 4.0 MGD, with the MBR portion of the facility operating at 8 MGD and the remaining conventional portion of the facility operating at 11.5 MGD. The peak hourly flow for the MBR facility, during a wet weather flow event would be 16 MGD, while the peak equalized flow capacity for the conventional portion of the facility would remain at 23 MGD. The accessory treatment systems would need to be designed for a peak flow of 16 MGD for the MBR system capacity.

Exhibit 1 provides an aerial photo site plan for the northern portion of the existing aeration basins as well as the open site area to the north of the aeration basins which was filled with the previous construction project. This exhibit illustrates a conceptual layout for conversion of four aeration passes to MBR [net increase of 3.5 MGD maximum month average daily flow] plus the new building for adding 16 MGD of peak hydraulic capacity for preliminary treatment and disinfection. Exhibit 2 provides a preliminary layout for the conversion of the four aeration basin passes to MBR [2 MGD per pass for a total of 8 MGD maximum month average daily flow].

Exhibit 3 provides conceptual design elevation views of the building which would house the new treatment system components [in addition to submerged membranes]. These conceptual drawings are provided as representative of what would likely be needed in order to add 16 MGD of additional peak flow capacity. These building elevations were developed with the concept of housing the new facilities within a building to be consistent with the earlier “good neighbor” policy for this facility and would minimize noise, odors, and visual impacts to the neighbors.

The goal would be that from outside the plant site, that it would be likely that no new facilities would be viewed and if any portion of new facilities were indeed able to be viewed that it would only be the upper portion of the building with the appearance of a typical residential condominium or office building.

Exhibit 4 provides a conceptual representation of a section through the proposed building, identifying one option of equipment and systems placement. Exhibits 5 and 6 provide conceptual design development floor plans for the proposed building. These exhibits have been prepared with the primary purpose of developing this concept sufficiently in order to prepare a conceptual design level budget cost as well as provide sufficient information to explain to the non-technical audience the type of new facility being proposed as an option, including general appearance of the prospective new building that would be constructed on this site.

A number of companies manufacture the general type of submerged MBR systems which were identified in this conceptual design evaluation. One alternative MBR configuration which might be considered for this facility, in the event a preliminary design study proceeded might be that of having the membranes outside of the biological reactor, such as the DynaLift MBR system being marketed by Parkson Corporation. For a retrofit such as proposed for this facility, this has the possibility of minimizing construction activity in the existing aeration basins with essentially all of the equipment installed inside the proposed building. It is anticipated that this type of configuration would require the building to be somewhat larger, although no specific investigations were performed under this conceptual design evaluation.

3.0 PRELIMINARY ESTIMATE OF COST

The equipment cost for the MBR portion of the upgrades is estimated by the manufacturer to be $2.2 million per aeration basin pass. This is equipment only, and equipment only for the MBR portion of the upgrades. The preliminary treatment system and disinfection system costs, including the proposed building are in addition to this cost.

1. Conversion of four aeration basin passes to MBR

a. Equipment ($2.2 million/pass) $8.8 million

b. Preparation/Installation $1.7 million

2. New Building

a. Structural and architectural $3.0 million

b. Fine Screens (16 MGD) $2.0 million

c. Grit Removal (16 MGD) $1.5 million

d. Effluent Transfer pumps (11,000 gpm) $0.5 million

3. Auxiliary Systems

a. Bleach storage and feed systems $0.5 million

b. Odor Control $1.0 million

c. Electrical and Controls $2.5 million

4. Other

a. Miscellaneous $1.0 million

b. Contingency $3.5 million

c. Engineering $4.0 million

TOTAL $30.0 million

The proposed project not only provides 3.5 MGD of additional treatment capacity during peak tourist season, but it provides an additional 16 MGD during wet weather events (which can also be used to provide additional reliability to meet permit conditions). In particular, additional influent screening and grit removal capacities are provided, which can also be used to back up the existing units.

Table 1: Hydraulic Capacity Considerations

Aeration Basins

Current Wet Weather Configuration

• 4 aeration basin passes used for additional wet weather flow equalization

• 10 aeration basin passes used to treat 23 MGD of equalized peak hourly flow

• Minimum Hydraulic Retention Time = 5.2 hours

Current Maximum Month Average Daily flow Condition

• 14 aeration basin passes used to treat 16 MGD of equalized peak hourly flow

• Hydraulic Retention Time = 10.5 hours

Wet Weather Configuration after conversion to MBR

• 4 aeration basin passes used for additional wet weather flow equalization

• 4 aeration basin passes used for MBR to treat maximum of 16 MGD peak hourly flow

• Minimum Hydraulic Retention Time (MBR) = 3.0 hours

• Limiting factor for MBR will be permeate pump capacity (existing RML pumps have sufficient capacity to return mixed liquor at sufficient rate)

• 6 aeration basin passes used to treat 23 MGD of equalized peak hourly flow

• Minimum Hydraulic Retention Time = 3.1 hours

• Limiting factor for Conventional system will be clarifiers and RAS pumps which already have sufficient capacity for these flow conditions

Maximum Month Average Daily flow Condition after conversion to MBR

• 4 aeration basin passes used for MBR to treat MMADF of 8 MGD

• Hydraulic Retention Time (MBR) = 6.0 hours

• 10 aeration basin passes used to treat MMADF of 11.5 MGD

• Hydraulic Retention Time = 10.5 hours

Secondary Clarifiers

Current Wet Weather Configuration

• Two clarifiers at 110 feet in diameter plus two clarifiers at 130 feet in diameter

• Total surface area = 45,528 square feet

• Surface overflow rate at PHF of 23 MGD = 505 gpd/sq ft [< 1,000 gpd/sq ft, OK]

• Solids loading rate at PHF of 23 MGD, MLSS of 4,000 mg/l, and RAS of 17 MGD =

1.25 lbs/hour/sq ft [< 2.0 lbs/hour/sq ft, OK]

Current Maximum Month Average Daily flow Condition

• Two clarifiers at 110 feet in diameter plus two clarifiers at 130 feet in diameter

• Total surface area = 45,528 square feet

• Surface overflow rate at MMADF of 16 MGD = 352 gpd/sq ft [< 800 gpd/sq ft, OK]

• Solids loading rate at MMADF of 16 MGD, MLSS of 4,000 mg/l, and RAS of 12 MGD

= 0.85 lbs/hour/sq ft [< 1.0 lbs/hour/sq ft, OK]

Table 1: Hydraulic Capacity Considerations (continued)

• Two clarifiers at 110 feet in diameter plus two clarifiers at 130 feet in diameter

• Total surface area = 45,528 square feet

• Surface overflow rate at PHF of 23 MGD = 505 gpd/sq ft [< 1,000 gpd/sq ft, OK]

• Solids loading rate at PHF of 23 MGD, MLSS of 4,000 mg/l, and RAS of 17 MGD =

1.25 lbs/hour/sq ft [< 2.0 lbs/hour/sq ft, OK]

Maximum Month Average Daily flow Condition after conversion to MBR

• Two clarifiers at 110 feet in diameter plus two clarifiers at 130 feet in diameter

• Total surface area = 45,528 square feet

• Surface overflow rate at MMADF of 11.5 MGD = 253 gpd/sq ft [< 800 gpd/sq ft, OK]

• Solids loading rate at MMADF of 11.5 MGD, MLSS of 4,000 mg/l, and RAS of 8.5

MGD = 0.60 lbs/hour/sq ft [< 1.0 lbs/hour/sq ft, OK]

Effluent Filters

Current Wet Weather Configuration

• Eight filters at 960 square feet each

• Total surface area = 7,680 square feet

• Surface loading rate at PHF of 23 MGD = 2.1 gpm/sq ft [< 5.0 gpm/sq ft, OK]

Current Maximum Month Average Daily flow Condition

• Eight filters at 960 square feet each

• Surface loading rate at MMADF of 16 MGD = 1.5 gpm/sq ft [< 2.0 gpm/sq ft, OK]

• Surface loading rate at PHF of 23 MGD = 2.1 gpm/sq ft [< 5.0 gpm/sq ft, OK]

Maximum Month Average Daily flow Condition after conversion to MBR

• Surface loading rate at MMADF of 11.5 MGD = 1.0 gpm/sq ft [< 2.0 gpm/sq ft, OK]

16.0 16.9 17.7 18.6 19.4 20.3 21.1 23.0

27.0

31.0

35.0

39.0 39.0 39.0 40.0

44.0

48.0

52.0

56.0 56.0 56.0

0 1 2 3 4 5 6

Fl ow

, M G

D

Number of Aeration Basin Pases Converted to MBR

Figure 1: SCWRF - MBR Capacity Considerations

Maximum Month Avg Daily Flow Equalized Peak Hourly Flow Peak Flow prior to Equalization