Technical_Memo_Polyphospate_2024_11-13.pdf

Technical Memo

Plant City Drinking Water System

Continuation of Aqua-Solv Polyphosphate Chemical feed

Introduction

Plant City’s Drinking Water System started utilizing Polyphosphate in 1982 to mitigate metal piping corrosion issues from metal piping within the community.

These issues were corrosion of house hold plumbing, copper piping, and brass fixtures. Proposals were solicited to present a solution to the issue. Four proposal were received and evaluated, and choice the city selected was Flo –Tec Automation’s Aqua- Solv chemical. The selected bidder was approved at the December 14th 1981 city commission. Since that time, the polyphosphate formula has been adjusted to match specific conditions in the City’s water chemistry. The addition of the polyphosphate has resulted in reduced pipe corrosion issues.

In the late eighties, growing concerns on lead and copper in homes reached Washington; leading to the passing of the USEPA Lead and Copper rule in 1990.

This rule is to address preventing and controlling Lead and Copper leaching into the drinking water from the home piping system and lead or copper service lines.

Below is a typical house and the sources of the possible contamination:

The United States Environmental Protection Agency, USEPA says the Lead and Copper Rule is designed to limit exposure to lead "that can cause damage to brain, red blood cells, and kidneys, especially for young children and pregnant women." It also is designed to limit copper exposure “that can cause stomach and intestinal distress, liver or kidney damage, and complications of Wilson disease in genetically predisposed people.”

The USEPA, the Clean Water Act, and the State of Florida Department of Environmental Protection (FDEP) require drinking water facilities to treat drinking water for control corrosion and color in the drinking water systems across America.

The action level for lead is 0.015 mg/L. The action level for copper is 1.3 mg/L.

Water suppliers must monitor locations as specified in the rule. If the 90th percentile value of all the samples exceeds the action level, action must be taken.

Actions may include investigation, recommendation of treatment, installation of treatment, checking of source water, removal of lead containing plumbing, and public education.

The main point is that addressing the leaching of lead and copper is a regulated requirement, and exceeding maximum limits leads to cost to the City, and potential permit violations, which could mean additional costs.

CURRENT APPLICATION

Flo-Tec Automation Associates, Inc. is the sole producer of a polyphosphate compound Aqua-Solv-SC approved by the Hillsborough County Health Department for use as a corrosion control agent in the Plant City Drinking Water System. The City of Plant City’s Drinking Water System started feeding Polyphosphate in 1982 to address corrosion issues from metal piping the residents were experiencing. Flo –Tec Automation has done studies on our water to formulize the right chemical compound for plant city water characteristic’s.

The chemical Aqua- Solv has been feed for water treatment of lead and copper control for the last 36 years with great success. Aqua-Solv-SC is a propriety chemical and sole source manufactured by Flo-Tec Automation. Aqua solv SC is made to NSF /ANSI 60 standards. A study completed in 1998 indicated the product supplied by Flo-Tec Automation Associates, Inc. was effective in the prevention of corrosion in the distribution system.

The application of Aqua-Solv-SC polyphosphate at our four drinking water treatment plants have successfully controlled the distribution system corrosion as evidenced by regulatory sampling and reporting. Customers service calls has not reported corrosion issues since feeding this compound. This success of feeding the current chemical has allowed the City of Plant City to be moved to a reduced monitoring schedule.

Currently FDEP allows Cities in compliance to monitor every three years (rather than two times a year) and has also allowed the City to reduce the required number of samples in each (from 60 samples to 30). This reduced monitoring schedule currently costs the City $1500 in analytical costs per sampling event, which is currently every 3 yrs. Thus, the City’s expense is $1500 every three years. If a new corrosion inhibitor is introduced, an increased amount of samples per year would be required per rule. The new requirement includes sampling twice a year, every year. Thus, in the same 3 yr period, the cost to the City would increase to a yearly cost of $3000.00 (for just the analytical costs, not including the cost of additional City labor time). For a three-year period, the cost would increase from $1500.00 to $9000.00 just for analytical costs.

POTENTIAL IMPACTS OF CHANGING CORROSION INHIBITIOR

In order to change the corrosion inhibitor for any reason, The City would be required to demonstrate to the FDEP the performance of any new corrosion control inhibitor prior to its implementation. To do this the City would be required to perform a paper evaluation and some rack testing by using coupons and other methods to simulate the distribution system, to demonstrate no significant, or adverse impacts to the corrosion of the distribution system. Such an evaluation is time consuming and costly. It would take six to nine months to perform and get measurable results. The Costs would range between $50,000 to $100,000 for the study.

If a new chemical is selected and passes testing, from the study, for being suitable candidate for full scale use in the distribution system; State and federal rules for lead and copper would require the City to resume the original plan of the Lead Copper Rule compliance sampling plan of 60 samples. Currently the city is on reduced monitoring because the corrosion control chemical the city is currently feeding has been very successful. The City of Plant City is currently required to sample 30 sites once every three years. The new chemical selected would by rule necessitate sampling twice a year for at least three years to prove effective in the distribution system and increase the number of samples from 30 to 60 each event. Also these events are labour intensive, have sample bottle prep time, and sampling education and pickup sampling from each of the 60 homes twice a year. A conservative estimate of cost increase for labour would be $10,000 over the course of the three-year period.

The items described above would also apply to any future change in corrosion control chemical and should it be every time a different chemical is selected to prove its effectiveness.

RECOMMENDATION

With the recent events of action level Lead and Copper issues in Flint Michigan, and Washington DC; as well as, many other cities across America. These cities, are finding corrosion within the distribution system, home plumbing and the associated water quality are a rising concern. In Flint, the city chose to change water sources and their corrosion control chemical which effected their water distribution system and water quality drastically.

One of the most important factors to prevent corrosion issues is to maintain stable, non- corrosive water quality throughout the distribution system.

Changing the water chemistry could, within the distribution system, put the stability of the water at risk.

The cost of the Aqua- Solv – SC product has been slightly increasing based on the cost of raw materials form the Covid -19 storage. Flo Tec sees the price remaining stable for the foreseeable future and is committed to the City. The city has previously used sole sourcing to purchase this chemical.

The City Utility Department requests maintaining usage of the Aqua -Solv –SC manufactured by Flo Tec as a sole source provider for the following reasons:

• Success of the current corrosion control inhibitor

• Stable Cost of the current corrosion control inhibitor

• Results of our Lead leading program have shown testing results well below the action levels

• The costs of engineering services, coupon testing, and another corrosion control study (potentially $50,000 to $100,000)

• The cost increases due to additional analytical testing and sampling required by rule when changing a corrosion control inhibitor (potentially >$10,000)

• A 42-year business partnership to provide good water quality to our community

BACKGROUND OF SAMPLING

Initial lead and copper plan was developed and approved in 1992. Population served during initial study for Plant City was 25,000. 303 sites were selected for <COPPER PIPE WITH LEAD SOLDER > 1982. Data used to develop the initial sampling plan:

Distribution System Materials

• Distribution system maps and record drawings

• Capital Improvement plan and / or master plans for distribution system development

• Utility records including meter installation records, customer complaint investigations and all historical documentation which indicate an /or confirm the location of lead service connections

• Interviews with senior personnel

• Review permit files

Interior Plumbing Materials

• Plumbing and / or building codes

• Plumbing and / or building permits

• Contacts within the building department, municipal clerk’s office, or

State regulatory agencies for historical documentation of the service area development

• Interviews with building inspectors

In December of 1992 the first round of analysis was completed. A total of 60 sites were sampled. The 90th percentile met the Action Level Requirements.

In July 1993 the second round of analysis was completed. A total of 60 sites were sampled. The 90th percentile met the Action Level Requirements. The City requested Reduced Monitoring from 60 to 30 sites per 40 CFR 141 and 142 for Lead & Copper. The request was approved November 29, 1993.

Yearly sampling was completed in 1995 and 1996. In 1996 a request was submitted and approved for Reduced Monitoring of 30 sites from annually to tri-annual.

Since then the City has sampled every 3 years as required by EPA and FDEP.

The Action Level has been compliant with each sampling period.

In 2007 the EPA revised the rules to required notification to residents involved in the sampling of the results for their sample. The reporting of results to the customers was started by the city during the 2005 sample period so compliance with the new rule was not a problem.

The 2011 sampling period added some additional changes by EPA to customer notification regarding Lead warning advisories. The templates were issued by EPA and adopted by FDEP. One template was for notices under the Action Level; the other was for notices over the Action Level. During the 2011 sample period Plant City had one site which exceeded the action level.

The 2014 sampling, 30 sites were sampled for both lead and copper. The 90th percentile met the Action Level Requirements. In fact, all sampling was below and in compliance with the established action levels for both lead and copper.

In 2017 the plan again was changed to meet changes in the rule and added a sampling questionnaire to check on homes plumbing, to see if replacement plumbing has been installed. This is in order to keep the right homes (COPPER PIPE WITH LEAD SOLDER > 1982) in the sampling plan.

The 2017 sampling, 30 sites were again sampled in reduced monitoring for both lead and copper. The 90th percentile met the Action Level Requirements. In fact, all sampling was below and in compliance with the established action levels for both lead and copper

In2024 the Operations division successfully passed all compliance testing for lead in our drinking water

POLYPHOSPHATES

Phosphates are water treatment chemicals used to solve specific water quality problems resulting from inorganic contaminants (iron, manganese, calcium, etc.) in ground water supplies and also to maintain water quality (inhibit corrosion, scale, biofilm, reduce lead and copper levels) in the distribution system. Polyphosphates work together, stabilizing water quality and minimizing color, scale, deposits, corrosion, and chlorine demand in drinking water systems.

Phosphates are used in municipal water systems to perform three broad functions: inhibit corrosion of water mains/plumbing (iron, steel, galvanized, asbestos/cement, lead, copper), sequester nuisance metals in the water supply (iron, manganese, calcium, magnesium). They can also improve the quality of water in the distribution system by removing scale deposits & tuberculation, discourage microbial film formation/regrowth, and stabilizing free chlorine disinfectant residuals.

Polyphosphate type chemicals react with soluble metals (iron, manganese, calcium, magnesium, etc.) by sequestering (bind-up) the metals to maintain their solubility in water. The phosphate sequestering process minimizes the risk of discoloration, staining, scaling, taste / odor and other water quality complaints.

Phosphates easily adapt to any pre-existing water quality without changing the water chemistry. Referred to as inhibitors, phosphates have a selective function, yet wide range of performance. Primary treatment benefits include: corrosion control, lead/copper control, sequestration of iron/manganese, control of calcium carbonate scale, and water softening, etc.

Many secondary benefits develop, such as: reduced chlorine demand due to corrosion inhibition and sequestration of Fe/Mn, lower color and turbidity in the distribution system, less staining, removal of system scale deposits, control of biofilm regrowth, lower TOC, fewer system coliform violations, increased C-factors and hydraulic flow rates in system, reduced electrical demand, fewer main breaks, better valve operation, improved meter accuracy, increased revenue, reduced hydrant flushing frequency, less wasted water during flushing, less maintenance and service expenditures, fewer complaint calls, and overall improved consumer satisfaction.

The formation of scale on surfaces in potable water systems is due to the crystallization of carbonates or sulfates of magnesium or calcium from solution.

Very low levels of polyphosphates (1-10 ppm) interfere with crystal growth. This type of scale inhibition is referred to as a threshold property because it occurs at a level much lower than would be required for a stoichiometric reaction.

Threshold inhibition by polyphosphates of calcium and magnesium carbonate formation is particularly effective at a pH range of 8 to 10 where carbonate scale in potable water is a major problem. Calcium sulfate scale is often a problem at lower pH ranges. The same mechanism of scale inhibition that can occur with calcium carbonate at a high pH range can also occur with calcium sulfate at a lower pH range at similar low (1-10 ppm) levels of phosphate addition.

Experience has shown that polyphosphates not only inhibit scale formation, but they can also help remove existing hard deposited carbonate or sulfate scale.

Pipelines carrying potable water treated with polyphosphate for extended periods of time (several months) first show a gradual softening of the scale followed by disintegration and removal. The soft scale particles are deflocculated by the polyphosphate and carried away resulting in a clean piping system.