four-log virus treatment of groundwater: city of boca ...€¦ · boca raton glades road water...
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Background
On November 8, 2006, the United States Environmental Protection Agency (USEPA) published the final Federal Ground Water Rule (GWR) which applies to public water systems that use groundwater sources for their raw water supply. Under the GWR and Chapter 62-550.828, Florida Administrative Code (FAC), groundwater systems shall provide four-log virus treatment of groundwater sources, or conduct “triggered” and “assessment” microbial monitoring. These requirements took effect in December 2009. To avoid the additional monitoring requirements, as well as potential public notices and “boil water orders” resulting from non-complying monitoring results, many utilities have elected to implement four-log virus treatment within their treatment processes. Since 2008, MBC has assisted several large South Florida utilities in evaluating their treatment processes, developing cost-effective four-log virus treatment strategies, implementing appropriate process improvements, and obtaining four-log virus treatment “certifications” of their facilities (letters of “Determination of Four-Log Virus Treatment of Groundwater) from the appropriate regulatory agencies. The water treatment facilities that MBC has served as Engineer of Record for four-log virus
Client City of Boca Raton City of Pompano Beach Broward County (BCWWS) Scope of Services Preparation of Compliance Studies analyzing treatment process and recommending process modifications, desk-top laboratory treatability studies, design and construction administration for implementation of recommended process improvements, and preparation of Demonstration submittals to regulatory agencies. Contacts Boca Raton Mr. Chris Helfrich Director of Utility Services 1401 Glades Road Boca Raton, Florida 33487 561.338.7303 [email protected] Pompano Beach Mr. A. Randolph Brown Utilities Director City of Pompano Beach 1205 NE 5th Avenue Pompano Beach, FL 33060 954 545.7043 [email protected] Broward County Mr. Rolando Nigaglioni, P.E. BCWWS 2555 W. Copans Road Pompano Beach, FL 33069 954.831.0882 [email protected] Key MBC Staff Frank A. Brinson, P.E. Audra McCafferty, P.E. Andrew Barba, E.I.
Four-Log Virus Treatment of Groundwater: Compliance Studies, Process Improvements, and Demonstration Submittals Multiple South Florida Utilities
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Four-Log Virus Treatment of Groundwater: Compliance Studies, Process Improvements, and Demonstration Submittals Multiple South Florida Utilities
treatment “Determinations” include the Boca Raton 70 mgd Glades Road Water Treatment Plant (WTP), the City of Pompano Beach 50 mgd WTP, the Broward County Water and Wastewater Services (BCWWS) 16 mgd WTP 1A, the BCWWS 30 mgd WTP 2A, and the BCWWS 5 mgd WTP 3A. A brief summary of the services provided for each facility follows:
Boca Raton Glades Road Water Treatment Plant
MBC’s services for the City of Boca Raton associated with four-log virus treatment implementation included the following:
Compliance Study. The objectives of the Compliance Study were to evaluate the ability of the facility to comply with the new disinfection requirements, develop a list of alternatives for process modifications to meet the requirements, and provide conceptual planning-level capital cost estimates for the recommended modifications. MBC found that the City could implement four-log virus treatment by utilizing free chlorine disinfection of the individual lime softened water stream and membrane permeate stream prior to blending, and then apply ammonia to develop a combined chloramine residual. Dinsinfection by-product (DBP, total trihalomethanes and five haloacetic acids) formation potential curves were generated and evaluated under the study to evaluate the impact of the proposed disinfection compliance alternatives on compliance with the D/DBP Rule. It was determined that continued compliance with the City’s goals for DBPs would not be compromised by the conversion to free chlorine disinfection due to the characteristics of the formation potential curves and the low levels of DBPs in the disinfected membrane permeate to be blended with the lime softened water.
Design and Construction of Treatment Process Modifications. Following completion of the Compliance Study, MBC provided design and construction services to implement the recommended process modifications. The modifications to the treatment process included:
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Provision of free chlorine residual, pH, and temperature monitoring for documentation of CT for 4-log virus treatment.
Relocation of ammonia feed points for compliance with 4-log virus treatment while minimizing the formation of DBPs.
Installation of new 0.8% sodium hypochlorite eductors and feed points. Replacement of the automatic polymer batching machines for the lime
softening process. Installation of hypochlorite piping for periodic disinfection of membrane
cleaning tanks and piping. Installation of sodium hydroxide (caustic) piping and controls to provide a
high pH permeate flush for control of organic fouling of the nanofiltration membranes.
Installation of citric acid piping for batching of low pH membrane cleaning solution in the membrane cleaning tanks.
Installation of variable frequency drives (VFDs) on the membrane cleaning and permeate flush pumps.
Preparation of the “Demonstration of Four-Log Virus Treatment of Groundwater” submittal to the Palm Beach County Health Department (PBCHD). The PBCHD issued the Determination letter certifying the Glades Road WTP as a four-log virus treatment facility on December 22, 2009. This approval was the first issued in Palm Beach and Broward Counties.
Pompano Beach Water Treatment Plant
MBC’s services for the City of Pompano Beach associated with four-log virus treatment implementation included the following:
Compliance Study. The objectives of the Compliance Study were to evaluate the ability of the facility to comply with the new disinfection requirements, develop a list of alternatives for process modifications to meet the requirements, and provide conceptual planning-level capital cost estimates for the recommended modifications. MBC found that the City could implement four-log virus treatment by utilizing free chlorine disinfection of the blended lime softened water / membrane permeate stream within a newly constructed, baffled blending and disinfection clearwell, and then apply ammonia to develop a combined chloramine residual. DBP formation potential curves were generated and evaluated under the study to evaluate the impact of the proposed disinfection compliance alternatives on compliance with the D/DBP Rule. It was determined that continued compliance with the City’s goals for DBPs would not be compromised by the conversion to free chlorine disinfection of the blended stream.
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Design and Construction of Treatment Process Modifications. Following completion of the Compliance Study, MBC provided design and construction services to implement the recommended process modifications. The modifications to the treatment process included:
Construction of a new sodium hypochlorite storage and feed system. Construction of yard piping improvements to route the lime softened water
to an existing blending clearwell for blending with the nanofiltration membrane permeate, and construction of internal baffling within the blending clearwell to provide a free chlorine contact zone.
Provision of free chlorine residual, pH, and temperature monitoring for documentation of CT for 4-log virus treatment.
Relocation of ammonia feed point for compliance with 4-log virus treatment while minimizing the formation of DBPs.
Preparation of the “Demonstration of Four-Log Virus Treatment of Groundwater” submittal to the Broward County Health Department (BCHD). The BCHD issued the Determination letter certifying the Pompano Beach Water Treatment Plant as a four-log virus treatment facility on August 1, 2014.
BCWWS Water Treatment Plant 1A
MBC’s services for the BCWWS WTP 1A associated with four-log virus treatment implementation included the following:
Compliance Study. The objectives of the Compliance Study were to evaluate the ability of the facility to comply with the new disinfection requirements, develop a list of alternatives for process modifications to meet the requirements, and provide conceptual planning-level capital cost estimates for the recommended modifications. MBC found that the County could provide four-log virus treatment by utilizing free chlorine disinfection of the lime softened water within a newly modified baffled disinfection clearwell, and then applying ammonia to develop a combined chloramine residual. DBP formation potential curves were generated and evaluated under the study to evaluate the impact of the proposed disinfection compliance alternatives on compliance with the D/DBP Rule. It was determined that continued compliance with the County’s goals for DBPs would not be compromised by the conversion to free chlorine disinfection of the process stream.
Design and Construction of Treatment Process Modifications. Following completion of the Compliance Study, MBC provided design and construction services to implement the recommended process modifications. The modifications to the treatment process included:
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Construction of a new sodium hypochlorite storage and feed system. Construction of piping improvements to route one-half of the process flow
from an adjacent clearwell to a newly modified, baffled clearwell for disinfection of the single (total) plant process stream.
Installation of free chlorine residual, pH, and temperature monitoring for documentation of CT for 4-log virus removal/inactivation.
Relocation of the sodium hypochlorite and ammonia feed points for compliance with 4-log virus treatment while minimizing the formation of DBPs.
Modifications to the transfer pumping and high service pumping systems to allow single-point disinfection and compliance monitoring of the plant process stream prior to transfer to on-site ground storage and pumping to distribution.
Preparation of the “Demonstration of Four-Log Virus Treatment of Groundwater” submittal to the BCHD. The BCHD issued the Determination letter certifying the BCWWS WTP 1A as a four-log virus treatment facility on October 22, 2013.
BCWWS Water Treatment Plant 2A
MBC’s services for the BCWWS WTP 2A associated with four-log virus treatment implementation included preparation of the “Demonstration of Four-Log Virus Treatment of Groundwater” submittal to the BCHD. The BCHD issued the Determination letter certifying the BCWWS WTP 2A as a four-log virus treatment facility on August 12, 2015.
BCWWS Water Treatment Plant 3A
MBC’s services for the BCWWS WTP 3A associated with four-log virus treatment implementation included the following:
Treatability and Water Quality Study. The objectives of the Treatability Study were to verify that BCWWS could provide four-log virus treatment of the water supply delivered to the WTP 3A facility from the City of Hollywood, and to confirm that the proposed four-log virus treatment protocol would not adversely impact compliance with the D/DBP Rule or other water quality parameters. MBC found that BCWWS could implement four-log virus treatment by utilizing free chlorine disinfection in a newly constructed section of large-diameter pipe in the storage tank fill piping, and then apply ammonia to develop a combined chloramine residual. DBP levels in prepared water samples representing the proposed four-log virus treatment protocol were evaluated relative to compliance with the D/DBP Rule. It was determined that
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continued compliance with the County’s goals for DBPs would not be compromised by the conversion to free chlorine disinfection of the process stream.
Design and Construction of Treatment Process Modifications. Following completion of the Treatability and Water Quality Study, MBC provided design and construction services to implement the recommended process modifications. The modifications to the treatment process included:
Construction of a new sodium hypochlorite storage and feed system. Construction of piping improvements to provide a free-chlorine disinfectant
contact and compliance monitoring zone within the ground storage tank fill piping.
Provision of free chlorine residual, pH, and temperature monitoring for documentation of CT for 4-log virus treatment.
Relocation of the sodium hypochlorite and ammonia feed points for compliance with 4-log virus treatment while minimizing the formation of DBPs.
Preparation of the “Demonstration of Four-Log Virus Treatment of Groundwater” submittal to the BCHD. The BCHD issued a conceptual Determination letter certifying the BCWWS WTP 3A as a four-log virus treatment facility on December 16, 2015 (pending completion of construction of the proposed process improvements).