New York facility adds UV disinfection to treat effluent discharged into major river
The Hudson River, in the Capital District of Albany, N.Y., is a popular recreational area for boating, swimming and fishing. Unfortunately, combined sewer overflows following storm events and snow melt from sewer systems dating back to the 1800s were causing increased fecal coliform counts, which, in turn, resulted in health alerts and limited access to the river. The six communities of the area, known as the Albany Pool, as well as the Albany County Sewer District (ACSD) and Rensselaer County Sewer District, formed a consortium to address these issues, and together they developed a Long-Term Control Plan (LTCP) for combined sewer overflows. One of the major provisions of the LTCP was to provide seasonal disinfection of the wastewater, including storm flows, discharged from the sewer districts’ treatment plants.
ACSD’s South Wastewater Treatment Plant (WWTP) is one of the major treatment plants discharging into the Hudson. While it was originally equipped with chlorine disinfection, the use of chlorine had been discontinued for many decades. It was time to upgrade to a safer, more effective disinfection method. It was time for ultraviolet (UV).
The ACSD South WWTP is a conventional activated sludge plant with an average flow of 19.5 mgd and a maximum flow of 45 mgd. Constructed in 1974, it receives domestic and commercial wastewater from Albany and has no industrial wastewater component. ACSD required a state-of-the-art disinfection system that could quickly and efficiently respond to the rapid flow increases during storm events and then could just as efficiently scale back as the flows subsided.
Reliability, ease of maintenance, small footprint and cost effectiveness were all key requirements. The disinfection season runs from May 1 to October 31, so ease of shutting down the system for the winter months also had to be considered.
The automated lift and modular design makes maintenance quick, easy and safe.
After considering several alternatives, the ACSD selected a Wedeco Duron 60i2-2.5X4 with high-power Ecoray 600-W lamps for its disinfection system. UV systems are safe and effective, eliminating 99.99% of pathogens, including bacteria, viruses and parasites. UV achieves disinfection goals without creating chlorine byproducts or adding harmful chemicals to the water – a definite plus when discharging into recreational waters.
The Duron system is a 45-degree inclined UV system and is available with variable bank widths, which allowed the units to be installed in the existing chlorine contact channels, greatly reducing construction costs. The South WWTP has four chlorine contact channels, and the full dosage at the peak 45 mgd can be achieved using only three channels, allowing one channel to remain in reserve. The Ecoray technology reduces the required lamp count by 50% compared to conventional amalgam UV lamps. The low lamp count, combined with the inclined orientation, allows for a much smaller footprint, again enabling the use of the existing chlorine contact channels and allowing for expansion of the system in the future.
The Duron system is equipped with a chemical-free automatic mechanical wiping system that cleans the lamps, preventing the fouling and loss of UV intensity without adding the cost of consumables. The automated lifting system pulls the lamp banks up for easy lamp or ballast maintenance without the need for a crane. At the end of the disinfection season, the automated lift system lifts the banks out for quick and easy winterization.
Online sensors monitor the UV transmittance of the wastewater in real time, as well as measuring the UV intensity from the lamps and, of course, the flow. Control protocols adjust the lamp power, number of banks online and even the number of channels in service to ensure that the correct dosage is delivered for the current conditions, regardless of the flow or changes in water quality.
Stainless steel air-conditioned ballast cabinets supply the power to the UV lamps.
Chief Operator Vince Cordi says that the Duron UV system ramps up well during storm events and peak flow periods, ensuring that the effluent discharged even at the highest flow rate is in total compliance with room to spare. The control protocols have failsafe programming to ensure that the dosage is always delivered, even as the system is turning off banks, lowering the lamp power and taking channels offline as the flows return to normal.
“It has always disinfected well,” Cordi said. “We have coliform counts going out in the single digits. If we get even in the twenties, it is a high number for us to get regarding colonies per 100 mL. Twenty or thirty would be a high number for us.”
The ACSD is confident that, thanks to the reliability of the Wedeco Duron UV system, the effluent leaving the South WWTP is free of dangerous fecal coliform, making the Hudson River cleaner and safer for everyone.