Customer partners with GTI to identify and treat cyanobacteria issue in raw water source

A Case Study in Quick Response, Successful Trial and Product Conversion

The Customer

2 MGD water treatment facility located in southern U.S. supplied by 114-million-gallon raw water reservoir.

Plant’s daily consumption of GTI PAC1 coagulant more than doubled for reasons unknown. Gulbrandsen Technologies helped customer identify problem and treat cyanobacteria issue in raw water source.

The Challenge

Unidentified cyanobacteria issue in raw water reservoir resulted in increased coagulant consumption from 1,200 to 3,260 pounds per day
  • Variation in source water pH (increasing during the day, decreasing at night)
  • Greenish color observed visually in raw water and elsewhere within treatment plant, including settling tanks
  • Unusual ‘grassy’ odor
  • Filter surface scums
  • Decreased filter run times
  • Difficulty in maintaining a finished water chlorine residual
  • Difficulty meeting turbidity goals

Collaborative Innovation

Customer partnered with GTI to identify and treat issue
  • After jointly ruling out any coagulant product quality issues, operating anomalies pointed to conditions in the raw water reservoir.
  • Alongside almost zero water movement, it was discovered that the lagoon had been exposed to unusually high temperatures over a prolonged period of time resulting in the growth of cyanobacteria.

GTI designed a series of jar tests to find the best coagulant solution that would better react to seasonally changing water conditions.

  • Source water pH stabilized

  • Filter run times improved

  • Improved chlorine residual in finished water

  • Turbidity goals maintained

  • The Solution

    3-week trial successfully met all water utility’s goals
    • Testing with Gulbrandsen’s extensive product line revealed that GPAC 2350 would be the best product to proceed to full scale testing
    • Solution met with all regulatory parameters
    • Resulted in lower coagulant dosage and improved operations with no violations in Turbidity (Finished Water), Total Organic Carbon (TOC), Trihalomethane or Haloacetic Acid


    Cyanobacteria is often difficult to detect and treat in potable water treatment systems. As plant personnel increasingly face operational challenges posed by warmer raw water sources, Gulbrandsen will be ready with targeted solutions. Our staff of talented account managers are trained to diagnose and solve difficult water treatment challenges. By narrowing down Gulbrandsen’s wide range of polyaluminum chloride products through observation and analysis, we were quickly able to propose the most operator friendly and cost-effective solution to control this troublesome contaminant.