The Bergen Point treatment plant looks at every facet of operations for ways to save energy and reduce environmental impacts
The 30-mgd Bergen Point Wastewater Treatment Plant in Suffolk County, N.Y., has made big strides in cutting energy usage and greenhouse gas emissions.
Through a long list of projects, the plant has reduced greenhouse gas emissions by 1,000 tons per year, saved the equivalent of 3,400 barrels of oil annually, and reduced annual energy costs by $375,000. Those are just a few of the benefits, according to Ben Wright, chief engineer.
“The first one was really the easy stuff, like more efficient motors, lighting retrofits, variable-frequency drives — the low-hanging fruit.” The total cost of about $3 million will be funded through the savings. The plant will also get some utility rebate money from the Long Island Power Authority.
The second project will be more extensive, and more beneficial. The construction cost will be about $1.5 million, and the payback will be relatively short.
Payback on items in the first phase of projects ranges from seven to 12 years. The plant was built in the 1970s, and its T-12 fluorescent lighting fixtures were outdated. The plant staff replaced them with high-efficiency T-8 fluorescent fixtures. “We put occupancy sensors in areas with significant lighting loads to knock down some of the power use,” Wright says.
The old HVAC controls and reheat coils were replaced with Johnson Controls to improve air-handling efficiency. Motors across the plant were also changed out. “On most motors — anything above 3 hp — we used high-efficiency motors and variable-frequency drives wherever it made sense, to match the flow more closely and not have big peaks on motor startup,” Wright says.
“We had old high-energy and maintenance-intensive reciprocating compressors for our instrument air, so we added much more efficient rotary screw units (Hibon-Ingersoll Rand). The baseline load will be met with one of the new units, while the second unit will modulate the speed and load to match the demands. The third unit will provide redundancy.”
Besides the energy savings, the plant received $128,500 in rebate money from Long Island Power: $100,000 for lighting improvements and motors, and $28,500 for three high-efficiency 100-hp air compressors.
Next up, and still in the planning stage, is the second-phase project. “Our energy engineer, Javed Ashraf, is developing the project and obtaining proposals that will result in savings of around $425,000 a year, not counting utility rebates,” Wright says. The simple payback will be less than three years.
About $550,000 of the $1.5 million cost will pay for efficient gas-fired condensing boilers to replace the 1980s-era heating system. “The new boilers will have a payback of four years,” says Wright. “Right now we have a central plant, and we run heated lines as much as 1,000 feet, so they lose some heat and aren’t as efficient as they could be. We’re thinking a decentralized system may be better, but then we might need more maintenance staff. It’s a balancing act.”
The work will also include new chillers and air-handling units. “We’re one of the higher users of power in the county, so we’re always looking at ways to reduce,” Wright says. “A lot of it comes from the operations staff and their day-to-day work, and where they see where some improvements may be made.”
Bergen Point has also added a SCADA system (Reflex Technologies and GE-Intellution) to automate control of various plant processes. “We put in fine-bubble diffusers (Parkson) about 10 years ago and saved about $1 million a year in power costs,” says Wright. “We had three 1,750-hp aeration blowers. Going to fine-bubble diffusers allowed us to turn off one of those blowers.”
The plant staff also knows the environmental impact of chemical use. “We use chemicals for odor control, sludge thickening and dewatering, disinfection, and pH control,” Wright says. “We always look for ways to do the same thing for less cost or fewer pounds of chemicals.
The staff has already reduced chemical use by about 1,500 pounds per day. The impact extends beyond Bergen Point: “Somebody is producing those chemicals and transporting it to us. There’s a significant energy reduction by doing that.”
Wright expects a significant reduction in the plant’s transportation carbon footprint from steps being taken to improve biosolids handling. Since its incinerators went offline in 2002, the plant has been shipping raw sludge to southern states. “We are evaluating our sludge management plan right now,” says Wright. “Whatever it ends up being, it has to be energy efficient, possibly a beneficial reuse that is compatible with the county and our neighbors.”
Already, improved dewatering has reduced hauling. New belt filter presses (Ashbrook) have increased the solids content from 22 percent to nearly 30 percent. That means 40 fewer trucks per month driving from the plant to a rail site in New Jersey for transportation a thousand miles one-way to Georgia, South Carolina or Virginia. “It saves about five pounds of carbon emissions per mile, per truck as well as less rail-related emissions,” Wright says.
The dewatering project cost $5 million, but it saves $1 million a year in trucking costs. “The payback is pretty good for us, and we haven’t even put a dollar figure on what we’re doing to help the environment,” Wright says.
Looking into UV
For disinfection, the plant now uses chlorine, but Wright and his team are considering a switch to UV disinfection.
Choosing between a new chemical method and UV has to account for more than the cost. “If I just said we’re using chlorine now and we’re putting in ultraviolet, there is a significant power load that someone could question,” Wright admits.
“But when you compare UV against chlorine disinfection and chlorine removal by chemicals, the amount of chemicals is significant when compared to the increased power. The cost-effectiveness analysis says use UV. We’re going to save money, and it’s safer for the environment.”
Another project on the planning board now is a natural-gas-fueled cogeneration facility. A 4-MW unit would power the entire plant. If it is cost-effective to build a larger unit, the excess power could be sold to the utility.
Bergen Point’s efforts to use energy wisely are part of a larger statewide initiative. The New York Power Authority in 2009 launched a program to reduce energy demand from water and wastewater treatment plants by about 20 percent by 2015.
In honoring Bergen Point and Suffolk County earlier this year, NYPA president and CEO Richard M. Kessel said, “The energy efficiency upgrade at Bergen Point crystallizes the benefits of clean energy technologies for wastewater treatment plants, which are among the most energy intensive of industrial applications. The upgrades are also reducing greenhouse gases and other emissions, as we do our part for a healthy and clean environment.”
NYPA says electricity accounts for 25 to 40 percent of the budget of a typical wastewater treatment plant and 80 percent of the cost of drinking water treatment systems. The utility is promoting measures such as on-site solar electric systems, biogas recovery to supply on-site power, and energy efficiency measures. Wright and the staff of Bergen Point are helping to pave a trail to meet the NYPA goals.