Click here to enlarge imageThis is a two-tank system, with each tank treating 1,050 gpm, which allows plant redundancy for dialing down the flow as demand dictates or to shut down one treatment train for any needed maintenance.
Plant Performance
This plant was designed for turbidities up to 400 NTU to preempt increased seasonal runoff conditions. To date, the Trident system is achieving a combined effluent turbidity of 0.08 to 0.16 NTU and turbidity removal efficiencies of 96 to 99%.
The system was designed to meet the following criteria:
- 400 NTU turbidity max.
- 100 True Color units max.
- Iron & Manganese < 10 ppm
- Total log credit potential of 6.5
- An additional 1.0 log credit may be obtained for filters producing less than 0.1 NTU effluent
Once the water has been clarified and filtered, the combined filter effluent passes through a Wallace & Tiernan UV Barrier M medium pressure system for inactivation of pathogenic microorganisms. The treatment plant uses onsite sodium hypochlorite generation for maintaining chlorine residual. Before installation of the UV system, the plant was using a chlorine residual around 2 mg/L. Now with the UV system in place, reduction in chlorine residuals has been realized.
Reducing the chlorine usage may potentially reduce the Total Trihalomethane (TTHM) level. Although the plant has not experienced high TTHM formation, plant personnel wanted to stay ahead of the ever-changing regulatory limits. To date, there has not been a microbiological occurrence.
Conclusion
In just 13 months, the 3-MGD Trident HS surface water treatment plant was fully operational and producing water with a turbidity level well below the regulatory standard of 1 NTU. Regulatory compliance of 4 log inactivation of microorganisms has been met with the multi-barrier treatment system and disinfectant protocol of UV and chlorine residual in the distribution system. Bloomfield has consistently maintained a zero occurrence of Fecal Coliforms and E.coli.
The Trident HS multi-barrier system has proven to be an effective water treatment system for meeting regulatory standards and providing operational flexibility, and is also designed for future expansion capability while delivering lower overall lifecycle cost.
About the Author: Anthony Galvan is Technical Sales Manager, General Filter and Microfloc Products, at Siemens Water Technologies in Colorado Springs, CO. He can be reached at [email protected].