The UV-oxidation system installed at the Neshaminy Falls Water Treatment Plant (WTP), owned and operated by Aqua Pennsylvania, has lead to:
- Lower operating costs
- A significantly reduced carbon footprint
- An improvement in water quality.
The plant serves approximately 100,000 people in Buck and Montgomery Counties in Southeastern Pennsylvania. The source water for the WTP is Neshaminy Creek, which is prone to seasonal algae blooms.
A powdered activated carbon (PAC) system was in place to remove taste and odor (T&O), but the system was unable to provide sufficient removal of MIB and geosmin, the compounds responsible for seasonal T&O. Further, increasing PAC dose led to high carbon costs and a large increase in residual waste sludge.
As part of a comprehensive WTP upgrade, engineers examined alternative T&O treatment technologies. The design objective was to determine the most cost-effective T&O-treatment technology for the Neshaminy Falls WTP.
Of PAC, UV-oxidation, and ozone, ozone was ruled out after estimates revealed that the added building footprint costs were prohibitive.
The TrojanUV Solution
Engineers working on the Neshaminy Falls WTP equipment upgrade conducted a comparison of the capital and operation/maintenance costs for PAC and the TrojanUVSwift™ECT UV-oxidation system for T&O.
Investigations revealed that while the treatment objective was the same, treatment performance would be significantly different between the two technologies. Historical data from PAC use illustrates that a PAC dosage of 30 mg/L was only able to achieve a 55% reduction in geosmin concentration. Conversely, the UV-oxidation system provides an 80% reduction at peak flow and a 90% reduction at average flow. This comparison is illustrated in Figure 1.
With respect to treatment cost, the results of an evaluation to remove taste and odor compounds for 90 days per year for 20 years are presented below. On a net present value (NPV) basis, UV-oxidation is a more economical solution than PAC (Figure 2). Further, in addition to providing a higher level of geosmin removal, UV-oxidation also provides a 3-log inactivation of Cryptosporidium and Giardia.
Thereby, UV-oxidation gives the WTP the ability to meet current and future disinfection regulations (for example the USEPA Long-Term 2 Enhanced Surface Water Treatment Rule).
Other benefits of UV-oxidation include no additional dry solids removal and the elimination of the dust and handling requirements associated with PAC.
In collaboration with the University of Western Ontario, Trojan conducted a life cycle assessment (LCA) of PAC versus UV-oxidation for the Neshaminy Falls WTP. Specifically, the climate change potential of each system was calculated by totaling greenhouse gas emissions associated with each system’s manufacture, operation, energy consumption and transportation over a 20-year lifetime.
Results indicate that the installation and operation of UV-oxidation at the Neshaminy Falls WTP would release 74% less carbon dioxide (as measured by carbon dioxide equivalents or CO2e) versus PAC (Figure 3). This equates to 23,670 less tons of CO2 being released into the atmosphere, equivalent to the fossil fuel emissions released by driving 4,931 cars for 1 year (12,000 miles per car per year at a fuel economy of 25 miles per US gallon¹). The relatively high climate change potential associated with PAC in a WTP is due in part to the energy required, in the form of heat and steam, to convert coal into PAC (a process known as “activation”). Conversely, the climate change potential of UV-oxidation systems is largely derived from the generation of electricity.
Advantages of UV-oxidation For Seasonal Taste & Odor
- UV-ox removes >90% of geosmin (versus 55% for PAC) at average flow
- UV-ox does not require dry solids removal, drying equipment, or handling of powdered carbon
- UV-ox is cheaper on a 20-year net present value basis when compared to PAC
- Operating a UV-ox system for seasonal taste and odor releases 74% less CO2e when compared to PAC
- UV-ox requires a very small physical footprint and can often be retrofitted into existing WTP piping
System Design Parameters
|Peak Flow Capacity||15 million gallons per day (MGD)|
|Average Flow||12 MGD|
|Disinfection Target||3-log inactivation of Cryptosporidium and Giardia|
|Design Geosmin Reduction||1.0-log (average flow); 0.7 (peak flow)|