Bacteria and Corrosion Control in Reclaim Water: Kurita America Mitigates Risk While Reducing Costs by 35%

At ten cents for every 1000 gallons, the use of reclaim water provided significant water cost savings for a thriving and innovative 900+ bed hospital located in Western Florida. However, it also presented a host of challenges—one of which was microbiological growth. At the time, the hospital’s previous biocide solution consisted of a stabilized bromine program in conjunction with periodic chlorine dioxide shocks.

Lacking a non-oxidizing biocide, the program had no long-term solution to anaerobic bacteria forming protective layers of slime in large colonies. These bacteria are resistant to bromine/chlorine biocides even at high concentrations. As colonies continued to grow within tower basins and chiller tubes, they significantly reduced chiller efficiency by fouling heat transfer surfaces with sludge. This was quickly identified as the underlying issue with the hospital’s water treatment program.

Kurita America was contacted to conduct an audit of the facility’s water treatment program to provide recommendations for controlling biological growth. Biofouling of building chillers from unchecked bacteria growth had led to plugged chiller tubes and a significant increase in approach temperatures, indicating loss of heat transfer efficiency. As the largest consumer of energy for a healthcare facility, small losses of efficiency in chiller plants can lead to significant increases in power costs. Biofouled chillers can be manually cleaned but this would require them to be taken offline and opened, leading to increased maintenance costs and downtime. Their first sign of a problem was when the tower basins were observed to be black. This indicated high bacteria levels present in the water. Laboratory testing confirmed that aerobic bacteria was just within acceptable ranges while anerobic bacteria was exceptionally high.

The Kurita America team implemented an integrated solution to provide effective bacteria control at a lower cost than the hospital’s previous program. The components of the solution included the following:

  • A Lumyn controller was installed on-site for 24/7 system monitoring. Facility operators and Kurita America engineers were able to react to alarms and trend data remotely to respond to system upsets in between physical wet testing.

  • A non-oxidizing biocide (fed once per week) along with a biodispersant (fed twice per week) was used to penetrate and break-up slime layers. Chlorine was fed continuously at a low concentration rate, via an ORP sensor, to oxidize the dispersed bacteria to prevent colonies from reforming between chemical feeds. A colony can reform during a simple biocide slug feeding because bacteria is able to be re-established once the oxidizer is burned off.

  • Copper corrosion is often an issue when controlling bacteria levels with chlorine. While high chlorine residuals lead to low bacteria counts, free copper levels will spike indicating increased corrosion rates. A high azole polymer-based corrosion inhibitor was selected to overcome this challenge with corrosion coupons providing corrosion rates to dial in feed rates. The Kurita America engineering team worked alongside building operators to monitor chemical balances, maintaining daily wet testing logs for weekly review, to determine the best course of action for future system upsets.

Lab results confirmed a significant drop in aerobic bacteria levels–from 100,000 CFU/mL back into the industry standard of 10,000 CFU/mL over the course of three months. Slime-forming bacteria levels dropped from <30,000 CFU/mL to less than 1000 CFU/mL in the same period. Proper monitoring of the chiller tubes for slime build-up, aerobic bacteria counts kept at or below <10,000 CFU/mL, and anaerobic bacteria counts at a non-detectable level will ensure a positive long-term solution for bacterial control. The program was later modified to a two-part chlorine activated sodium bromide program which is more effective at the < 9 pH of reclaimed water than standard chlorine and is softer on copper. Corrosion rates in Mils Per Year (MPY) on copper were reduced from 0.679 MPY to 0.192 MPY over a six-month period after this change. While steel corrosion rates also dropped from 1.958 MPY to 0.545 MPY over the same period. Both results indicate excellent or very good protection of the customer’s assets per the chart below:

Kurita America provided excellent bacteria and corrosion control through our integrated solutions, including equipment, chemical and a team-based approach. This collaborative effort provided significant cost savings on chemical products and a superior monitoring system that saved a third of the cost from the previous year. This system increased operational efficiency and continues to provide peace of mind to the facility staff and Kurita America personnel. The solution was also an excellent example of putting Kurita’s corporate philosophy into action: “By studying the properties of water and mastering them, we create an environment in which nature and man are in harmony”.

If you would like more information on our unique approach to microbiological control, please contact Kurita America today.

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