AWWA MTC69670

Increases in the population of the City of Ormond Beach, Florida (the City) placed increased demands on the City's existing 8.0 mgd conventional lime softening WTP. Coupled with the anticipated deterioration of raw water quality due to the intrusion and upconing of salt water, the City requested CDM to conduct a pilot study and complete the preliminary and final design for a 4.0 mgd low pressure reverse osmosis (LPRO) expansion. Final design was completed in 2006, construction activities for the LPRO expansion commenced in 2006, the system was placed online in 2007, and all construction activities concluded in early 2008. A collaborative effort by the City, the FDEP, and CDM resulted in the successful permitting of an innovative and sustainable method of disposing of up to 1.0 mgd of concentrate produced by the City's LPRO expansion. This unique method of concentrate disposal provided for the blending of the LPRO concentrate with reclaimed water at the City's WWTP. The most significant benefit associated with the implementation of this disposal method includes the ability to reuse this previously unutilized resource and augment the City's reclaimed water supplies. Furthermore, no portion of the City's WWTP capacity was consumed, as concentrate blending occurs in the equalization basin downstream of all treatment processes. The past seven months of operation demonstrate the success of this innovative and sustainable method of concentrate disposal. Blending the LPRO concentrate with the City's reclaimed water has increased the City's supply of this resource by approximately 0.5 mgd. While the use of reclaimed water is heavily affected by the amount of precipitation, approximately 80 to 90% of the LPRO concentrate is reclaimed, and during periods of high reclaimed water demand, 100% of the LPRO concentrate is reclaimed. While the TDS and chloride values of the blended reclaimed water have increased as a result of concentrate blending, no adverse effects to the vegetation or soil structure have been observed. This paper discusses the permitting efforts and challenges associated with the implementation of this innovative method of concentrate disposal. Includes tables.