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Ff VOLUSIA COUNTY SOUTHWEST REGIONAL WATER REUSE CASE STUDY

Larry Hayduk Volusia County Utilities Engineer

DeLand, Florida 32720-4612

William S. O'Brien Florida Power Corporation

St. Petersburg, Florida 33733

David A. Gierach, P.E. Project Manager

Conklin, Porter & Holmes-Engineers, Inc. Sanford, Florida 32772-2808

- ABSTRACT

In 1986, Volusia County purchased a private utility servicing the southwest section of the County. The private utility had two small wastewater facilities with limited land area for expansion and in marginal condition. Based on the projected growth for the area, the County determined that a new regional plant should be constructed to service the area.

The regional facility was to be placed in the vicinity of the DeBary Golf and Country Club, which is a large Planned Unit Development to be serviced by the facility; reclaimed water was to be supplied to the golf course for irrigation.

During site acquisition, citizen objections were quite vocal for several sites. As a result, the County began negotiations with Florida Power Corporation who owns and operates the DeBary Power Plant which is located on a 2,000 +/- acre parcel in the area.

Florida Power Corporation agreed to sell a portion of their site for the new water reclamation facility, and it was further agreed that Volusia County would supply reclaimed water to the Florida Power Corporation DeBary Plant

Reverse Osmosis/Demineralization Water Treatment Plant, which supplies water to their combustion turbines to limit the amount of nitrogen oxides (NO3 in the turbine exhaust. It was further determined that the Reverse Osmosis/Demineralizer Reject Water, along with the stormwater runoff from the vicinity of the turbine units which is treated by an oil/water separator, should be delivered from the FPC DeBary Plant to the new Volusia County Water Reclamation Facility for treatment and blending with the reclaimed water, to allow for the beneficial use of this stream rather than continuing to discharge to rapid rate infiltration basins.

for irrigation of their site for dust control and as a water supply to their t

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- This project provides for the beneficial use of reclaimed water and a reject water stream for irrigation of the DeBary Golf Course, irrigation of the FPC DeBary Plant, and for use in the combustion turbines of the FPC DeBary Plant. c

BACKGROUND

In 1986, Volusia County purchased a private utility servicing the Southwest Volusia area. The private utility had two oxidation ditch type wastewater treatment plants which were in marginal condition, had limited area for expansion, and were limited in capacity.

The population of the Southwest Volusia area was projected to expand from 18,971 to 31,686 over a ten-year period. This equates to an increase in wastewater flows from approximately 400,000 gallons/day to 1 ,OOO,000 gallons/day (gpd) for the area. As a result, the existing wastewater facilities needed expansion or a new wastewater facility was required. A Master Wastewater Plan was prepared by Conklin, Porter & Holmes-Engineers, Inc., and it was recommended that a new facility be constructed to service the West Volusia area and that one of the smaller existing wastewater plants, the Terra Alta Plant, with a capacity of 225,000 gpd, be removed from service.

SITE SELECTION

Volusia County began the search for a site for a Regional Wastewater Facility which could service the Southwest Volusia service area with primary emphasis on selection of a site large enough for future expansion and located in an area to limit impacts on surrounding land areas.

Several sites were identified and subsequently rejected due to various considerations, but primarily due to citizens' objections to the proposed locations.

Florida Power Corporation (FPC) owns, operates, and maintains the DeBary Plant on a two-thousand acre parcel located in Southwest Volusia. This peaking facility utilizes combustion turbine generators to supply power to their electrical distribution system during pea! demand perids. Apprc?ximate!y thirty acres of the two-thousand acre site contains improvements, with the remainder left natural to serve as a buffer to adjacent development and for future expansion. The DeBary Plant property is also located adjacent to DeBary Golf and Country Club, a major Planned Unit Development which was to be serviced by the proposed wastewater plant and supplied reclaimed water from the wastewater plant for irrigation of the golf course.

Considering the above information, Volusia County began discussions with Florida Power Corporation to purchase a portion of their site for a new . wastewater treatment facility. FPC was very receptive to the idea and discussions continued on how the program could benefit all involved.

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FPC utilizes groundwater from two wells on their site. The groundwater is treated at their Reverse OsmosidDemineralizer Water Treatment Plant and is injected into the combustion system of the gas turbines to limit the amount of nitrogen oxides (NO3 in the turbine exhaust. This limitation is required by strict Federal and State Air Pollution Control Regulations. Water flow to the turbine combustors is a function of total fuel flow, relative humidity, and ambient temperature. The water is burned with the fuel and the water/fuel ratio is established through field compliance testing of the individual unit per Federal Standards. Per this testing, the units require approximately 550 gallons/minute of water during operation.

Due to the tremendous growth within the Central Florida area and the continued growth projected for the area, the use and availability of groundwater is becoming a critical issue. Salt water intrusion is also becoming more of a problem as groundwater withdrawals increase due to the continuing demands for potable water.

*

FPC and Volusia County are both keenly aware of this major environmental issue and are continually working to find ways to improve the environment or limit their impacts.

It was discussed that Volusia County could supply reclaimed water from the new wastewater facility to FPC, thus eliminating their use of high quality groundwater in their combustion turbines. In addition, Florida Power Corporation required water for irrigation of their DeBary Plant site for fugitive dust control.

FPC also produces a reject water supply from their Reverse Osmosis/Demineralizer Water Treatment Facility and from their oil/water separator unit which treats stormwater runoff. This combined stream is currently discharged to Rapid Rate Infiltration Basins and it was determined that this reject water could be delivered to the new Volusia County Wastewater Plant and blended with the plant effluent, allowing this reject water to be used for a beneficial purpose rather than just discharging it to the Rapid Rate Infiltration ---.-.,. Rncinc

The basis was established for Florida Power Corporation to sell a portion of their DeBary Plant site to Volusia County for construction of the new Southwest Regional Water Reclamation Facility. The sale was contingent upon Volusia County and FPC working to develop a program to allow the following:

1) Volusia County to deliver reclaimed water to FPC for use in irrigating their site and for use in their combustion turbines; and, 2) FPC to deliver the R. 0. /Demineralizer/Oil/Water Separator reject water stream to Volusia County for treatment and blending with the Water Reclamation Facility’s reclaimed water. Volusia County would have FPC as a reclaimed water customer and a wastewater customer.

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The County purchased approximately forty (40) acres of land for the new water reclamation facility as shown on Figure 1. The site is surrounded by 100 foot power easements on all four sides to buffer the site and provide potential pipeline routes for forcemains and reclaimed water lines. Property to the north, west, and south is owned by Florida Power Corporation and utilized for a power plant; therefore, the new water reclamation plant would be a compatible land use.

Property to the east of the site is the DeBary Golf and Country Club, which is a major wastewater and reclaimed water customer to be served by the new regional water reclamation facility. The site was purchased by the County without a single objection from the citizens and all involved benefitted from the selected site, including Volusia County, Florida Power Corporation, utilities' customers, and most importantly, the environment.

SITE PLAN DESIGN AND PROCESS CONFIGURATION

The projected growth for Southwest Volusia County dictated the need for a major regional wastewater facility with a twenty-year wastewater flow ranging from a present flow of approximately .5 million gallons/day to a projected future flow of over 3.3 million gallons/day. The available capital funds, current customer base and bonding capability dictated the need for phasing to reasonably match capacity to needs, thereby helping to keep the County rates reasonable. Volusia County's rates are among the lowest charged by utilities in the area. The phased expansion schedule for the Southwest Regional Water Reclamation Facility is shown on Figure 2. The phasing was scheduled in 500,000 gpd treatment capacity increments. The process selected for the facility was selected to allow this phased expansion program and yet meet the stringent EPA Class I Reliability requirements dictated by the Florida Department of Environmental Protection for wastewater facilities which supply reclaimed water for public access use.

Figure 3 shows the process flow diagram from the Southwest Regional Water Reclamation Facility, and Figure 4 shows the layout of the plant on the site.

F i g ~ r e 1 shnws the relatinn of the plant to the surrounding area.

The plant was constructed utilizing concrete tankage to ensure the longevity of the plant and to reduce maintenance requirements. The biological treatment system is a modification of the oxidation ditch type process called the "Orbal System", as manufactured by Envirex Corporation. The system is a multiple channel oxidation ditch initially constructed with two channels for a capacity of 500,000 gpd and readily expandable to 1,000,000 gpd by the addition of a third exterior channel on the ditch. Disc aerators are provided for aeration and mixing of the activated sludge with the return sludge and raw wastewater. Each of the multiple channels is capable of being separately dewatered to meet EPA Class I Reliability Criteria and to allow cleaning of each channel, retrieval of any items dropped in the channels or other maintenance related activity. The flow from the biological treatment system is equally split in an integral flow splitter box to the clarifiers.

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FIGURE 1

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The plant has two clarifiers with capacities of 375,000 gpd each. The flow splitter box was built integral with the oxidation ditch to eliminate costs of a separate external structure. The clarifier capacity was designed for 75% of permitted plant capacity with the largest unit out of service to meet EPA Class I Reliability Criteria. The addition of a third clarifier will increase the plant capacity to 1,000,000 gpd.

Tertiary filtration is provided by upflow type sand filters manufactured by Parkson Corporation. High level disinfection is also provided as required by Florida regulations for public access reuse. Continuous on-line monitoring is performed by chlorine residual and turbidity to ensure the quality of the reclaimed water. The control system automatically diverts reclaimed water to reject disposal any time chlorine residual is less than 1 mg/l or turbidity is greater than 2 NTU. 1

Residuals produced at the facility are aerobically digested and dried in Vacuum Assisted Sludge Drying Beds (VASDB), manufactured by U. S. Environmental Products. The dried residuals are land applied to promote a beneficial use for this byproduct.

The Operations Building was designed to serve multiple functions. The building houses the following: motor control center; office/control room; chlorination facilities; maintenancehtorage room; and equipment room containing a 350 KW standby generator, duplex air compressor, and vacuum sludge dewatering equipment.

Future expansion was considered throughout the design and various items which were logical and cost-effective to oversize were designed accordingly. Examples include the Motor Control Center, where all conduit is provided for a 2,000,000 gpd facility; the generator and air compressor are sized to handle a 2,000,000 gpd facility, and, with the addition of a single vacuum bed, the facility will be able to dry the residuals for the 2,000,000 gpd facility. This philosophy was followed for the entire facility to ensure facility expansion could be accomplished cost-effectively without interruption or interference with ongoing operation and

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Off-site reclaimed waterlines were required from the Southwest Regional Plant to an existing 1.5 million gallon storage pond, located at the DeBary Golf and Country Club, to existing Rapid Rate Infiltration Basins no longer used by the abandoned Terra Alta Wastewater Plant, and to a 12 million gallon steel storage tank located at the Florida Power Corporation DeBary Plant. With the use of the existing 12 million gallon tank at FPC, the available reclaimed water storage was 13.5 million gallons, which provides flexibility to maximize the use of reelaimed water, which can be stored in wet weather conditions and used during dry conditions when it is needed most.

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The golf course is projected to use 210,000-400,OOO gpd of reclaimed water. At full load operation, FPC DeBary Plant would use nearly 800,000 gpd; however, average annual use is projected to be between 100,000 - 150,000 gpd of reclaimed water. These capacities exceed the initial design capacity of the Southwest Regional Water Reclamation Facility and the demands will be supplemented with groundwater until additional reclaimed water flows become available.

REGULATORY PERMITTING

This project had a number of unique features which required special coordination with the regulatory agency which permits wastewater facilities in Florida, the Florida Department of Environmental Protection, and with the U. S. Environmental Protection Agency. Reject water from an R.O./Demineralizer Water Plant and from an OiVWater Separator is permitted as an industrial facility. If a publicly owned treatment works, i.e. Volusia County Southwest Regional Water Reclamation Facility accepts the reject flow, they are responsible for ensuring the flow will not interfere with the plant operation.. Volusia County is preparing an Industrial Waste Pretreatment Program (IWPP) which must be approved by the Environmental Protection Agency, which will set quality and flow limits on the reject stream to ensure the stream will not interfere with the proper functioning of the water reclamation facility. The IWPP will also determine if any other industrial activities are in the service area which may affect the water reclamation facility. In addition, the University of Florida Institute of Food and Agricultural Science performed a study to ensure the blended reclaimed water and reject water flow would not be harmful to the turf grass on the DeBary Golf Course, since this stream is to serve as an irrigation supply for the course. Sample plugs from the golf course were taken and various applications and concentrations of the combined reclaimed water and reject water were applied to the plugs over a several month period and the grass growth and soil were analyzed to determine the effects of the application. It was determined that the stream did not affect the turf detrimentally to allow planning to continue. This report provided technical support data for assistance in permitting of the project.

The detailed planning and investigations provide the basis to help ensure the success of the program. Coordination and keeping the regulatory agency involved and updated on the program also helped in ensuring the program was acceptable and permittable by the regulatory agencies.

CONCLUSION

Volusia County developed a unique and positive working relationship with private industry (Florida Power Corporation) and private development (DeBary Golf and Country Club) to allow the construction of a cost-effective water reclamation facility beneficial to all parties including the utility customers, and most importantly, the environment.

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Volusia County was able to purchase a wastewater plant site which is extremely well buffered yet centrally located in the service area and fully supported by the citizens. The reuse system also gains use of valuable existing water storage facilities.

Florida Power Corporation, with their environmental consciousness, will be able to eliminate or greatly reduce their use of groundwater for site irrigation and burning in their combustion turbines, thus providing a beneficial reuse of reclaimed water. They will also be able to eliminate the disposal of their Reverse Osmosis/Demineralizer Reject Water to rapid infiltration basins and be able to provide for the beneficial reuse of this water by sending it to the new Volusia County Southwest Regional Water Reclamation Facility for treatment and blending.

DeBary Golf and Country Club is able to eliminate the use of groundwater for irrigation of their golf course and provide for the beneficial reuse of reclaimed water.

Volusia County provided long-term planning to ensure the Southwest Regional Water Reclamation Facility was a cost-effective facility that can be easily maintained and operated, cost-effectively expanded without interfering with plant operation and maintenance and that the program was acceptable and permittable to the regulatory agencies. Most importantly, the project provided for advanced secondary treatment of wastewater and beneficial use of reclaimed water (a resource) to reduce groundwater withdrawals, thus helping to preserve the available groundwater supplies.

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. . . . . . . . . . . . . . . . . . . 1994 WATER REUSE SYMPOSIUM

PROCEEDINGS . . m . . m m . m m m 8 . m m . m 1 m

FEBRUARY 27.- MARCH 2, 1994 DALLAS, TEXAS

American Water Works Association