Southwest Water Reclamation Facility Conceptual Design Facilities Plan Update

Orange County Utilities, 
Florida

Southwest Water Reclamation Facility Conceptual Design Facilities Plan Update

Service Type: 
Project Highlights: 

Carollo provided engineering services to prepare a conceptual design for the proposed Southwest Water Reclamation Facility (SWWRF), including:

  • a review and update of the previous capital improvements and
  • a facilities plan prepared for the plant
  • a conceptual level comparison of four biological process alternatives to the MBR alternative that was proposed under the previous capital improvements plan

Orange County Utilities (OCU), FL currently owns and operates three regional water reclamation facilities (WRF) to treat the wastewater generated in its collection system. All three treatment facilities produce reclaimed water for public access reuse as regulated by 62-610 F.A.C. As part of a previous master plan developed for OCU, a fourth new WRF was proposed to be constructed by 2015 to serve a portion of the south-west portions of service area, currently being served by its South WRF. The master plan also recommended that this new WRF treat the wastewater to advanced wastewater treatment (AWT) standards while using a 5-stage Bardenpho™ process for biological nutrient removal (BNR) followed by a membrane bioreactor (MBR) process for tertiary filtration. The AWT standards require the effluent to meet the following treatment levels on an annual average basis:

  • 5-Day, Carbonaceous Biochemical Oxygen Demand (cBOD5) of less than 5 mg/l
  • Total Suspended Solids (TSS) of less than 5 mg/l
  • Total Nitrogen (TN) of less than 3 mg/l
  • Total Phosphorus (TP) of less than 1 mg/l

Other effluent water quality standards include:

  • Minimum Chlorine Residual of 1 mg/l
  • pH range of 6.0 – 8.5
  • Fecal Coliforms of non-detect in more than 75% of samples over a 30-day period and any one sample less than 25 per 100 mL sample.

As part of the Program Management Contract (Y9-901) with OCU, Carollo Engineers was tasked with preparing an updated facilities plan for the new facility. The goal of this task was also to re-evaluate the MBR process with other conventional alternatives on a life cycle cost basis. The first phase of the new facility will be designed to treat an average daily flow of 5 mgd. At build-out, the facility is anticipated to treat flows up to 15 mgd on annual average day flow basis.
Carollo evaluated the following five liquid treatment process alternatives:

  • 5-Stage Bardenpho™ with secondary clarifiers and cloth disk filters;
  • 5-Stage Bardenpho™ with secondary clarifiers and tertiary membrane filters;
  • Step-feed Bardenpho™ with secondary clarifiers and cloth disk filters;
  • 3-Stage BNR with secondary clarifiers and deep-bed denitrification filters; and
  • 5-Stage Bardenpho™ with MBR.

To help compare the five alternatives, a weighted evaluation matrix was created for a set of six economic and non-economic parameters. Economic parameters included, construction costs, operation and maintenance (O&M) costs and life cycle costs. O&M costs included costs for power, chemical, and labor costs. Non-economic parameters included energy consumption, chemical consumption, biosolids production, overall plant footprint, and water quality.

Conceptual level site plans were developed for each of the five alternatives showing the facilities anticipated in the initial phases while showing sufficient space reserved for future similar facilities to treat the anticipated build-out flows.

The analysis recommended that the facility implement the step-feed Bardenpho™ BNR process followed by secondary clarifiers and cloth disk filters and disinfection using sodium hypochlorite.