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4.11 Case studies (Topic k)

4.11.1 Reuse

History

The Orange County Eastern Water Reclamation Facility is located in one of the most rapidly growing areas in the United States. This advanced water reclamation system was designed to enhance the environment of the Econlockhathee River basin in east Central Florida, reduce demand on potable groundwater by providing sufficient reclaimed water for non-potable uses, and provide sufficient wastewater treatment capacity for the East Orange County in Florida and constructed in phases since 1984. This facility allowed the decommissioning of six secondary treatment plants that had directly discharged effluent into surface water. The plant has a permitted capacity of 72 ML/d, and currently 43 ML/d of municipal wastewater. The plant was recognized for its outstanding performance by many regulatory agencies and professional organizations.

Plant Description

Raw wastewater is first screened, then enters a pista grit- grit removal system. Following grit removal is a five-stage Bardenpho nutrient removal system consisting of an in-line fermentation tank, followed by the first anoxic tank, an aeration basin, the second anoxic tank, reaeration and secondary clarification. Final ABW filters polish the effluent, which is chlorinated. Dechlorination occurs in the dechlorination zone of the wetlands, prior to reclaimed water entering wetlands vegetation zone. The treatment facility is linked with an integrated reuse system consisting of aquifer recharge, industrial reuse and wetlands enhancement. Air from the headwork's is treated for odor control in three biofilters.

Reclaimed Water Quality

The following table compares the permitted annual average values for the reclaimed water and the actual measured values for 1998:

The plant consistently produces reclaimed water considerably better than required by stringent regulatory permit. The reclaimed water quality is analyzed daily using 24-hour flow proportional composite sampling.

Reuse

Reclaimed water is 100% reused, thus reducing the demand on precious groundwater in the Florida aquifer. The reuse system supplies cooling water for the Orlando Utilities commission's Stanton Energy Center, a 900-megawatt power plant located adjacent to the facility. The facility now supplies this power plant with 90% of reclaimed water produced at the facility. The reuse of reclaimed water for cooling purposes was one of the first approved programs in Florida.

The water reclamation facility also reuses reclaimed water in a combination of natural and created wetlands. This was one of the first such systems permitted by the Florida Department of Environmental Protection (FDEP) under exemptions to the wetland rules. The County in cooperation with the University of Florida- Center for Wetlands conducted extensive research on the effect of reclaimed water in wetlands. This research has produced very valuable information on the use of reclaimed water in the wetlands. These wetland's provide nutrient reduction and additional cleansing of the reclaimed water. Currently, less than 10% of the reclaimed water is reused in the wetlands. In turn, the natural wetlands are enhanced to provide a valuable habitat for diverse plant and animal species.

The wetlands are sized for 23.5 ML/d. There are 60.7 ha of natural wetlands and 60.7 ha of former pine flatwoods that have been converted to wetlands. A distribution system with seven application zones delivers reclaimed water to the wetlands uniformly. A channel collects and carries the water from the natural wetlands to the created wetlands. There is an additional 66.8 ha of off-site wetlands through which effluent flows before reaching a small creek that is connected to the Econlockhatchee River. This river was designated as Outstanding Florida Water by the State of Florida, partially due to benefits created by the water reclamation project.

There is also a 9.5 ML/d rapid infiltration basins for aquifer recharge.

In addition to the above, nearby golf courses are permitted to irrigate with the reclaimed water. Provisions for expansion include additional golf courses and green space irrigation.

Sludge Handling

Waste sludge discharged from the clarifiers is dewatered in belt filter presses to 14 to 15% solids and hauled to a nearby landfill where the sludge is landfilled with the municipal solid waste.

Financing

The wastewater customers pay a monthly fee to cover the operations cost. All developers pay an impact fee to cover the plant capacity required for their development, which finances plant expansions.

Operations, Maintenance and Management

The plant employs 30 people with annual operating costs of $5.2 million U.S. The County helps pay for certification classes, certification renewals, commercial driver's licenses, work related training and professional registration. As a result, 19 of the plant's employees are certified by the State of Florida. The County also reimburses the employees up to $1,000 per year who continue their education at local colleges and universities. Many of the staff are long term employees, with an average of 12 to 15 years' experience at this plant.

Management places a high priority on planning ahead through yearly capital improvement program based on operational and upcoming regulatory requirements.

The facility uses computers for data management, record-keeping, maintenance and personnel scheduling, purchase orders and interactive safety training. A Computer Maintenance Management System (CMMS) and a Supervisory Control and Data Acquisition (SCADA) system are being implemented in accordance with the Automation Master Plan to improve the County-wide wastewater service efficiency.

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