Puerto Rico’s government-owned utility takes on a massive program to update facilities, enhance energy efficiency and improve performance.
The Puerto Rico Aqueduct & Sewer Authority is the only source of water and wastewater services for nearly all of Puerto Rico’s 3.7 million people.
With annual electricity costs of $209 million, the government-owned utility has plenty of incentive to cut its power bill, second in size only to labor costs. One reason for the high bill is the price of energy — 22 cents per kWh, more than twice the United States national average. The authority paid 28 cents before its rates were reduced by an act of the Puerto Rico Legislature.
“Our system is quite complex,” says Lynnette Ramirez, executive director of infrastructure. “We have 121 water treatment plants, 52 wastewater treatment plants and eight dams — big numbers for an island that is only 100 miles by 35 miles.” The authority also has nearly 1,500 storage tanks, 1,800 pump stations and 270 wells, all connected to more than 10,000 miles of water mains and aqueducts and 2,000 miles of sewage lines across the island’s 3,500 square miles.
In its first year of a new five-year strategic plan to upgrade its entire system, PRASA is already seeing success, reducing its annual electric demand from 750 million kWh to 720 million. “We have a goal to become more efficient, have excellent operations, focus on sustainability, and reduce electricity costs and consumption,” says Ramirez. “We want to be a world-class utility.”
One company helping is Honeywell, which has 10- to 15-year energy performance contracts at four wastewater plants and two drinking water plants. The $53 million in contracts will be funded through guaranteed energy savings of more than $7.5 million a year, says Pete Chase, a Honeywell engineer. He says the work involves “a little bit of everything” as determined by the authority and its engineering firm, Arcadis. Work is to be completed in 2015 and 2016.
At one wastewater treatment plant, the work included replacement of an 80 mgd influent pump system and bar screens, new blowers for the grit chamber and the addition of a SCADA system. Another facility received new blowers, diffusers, controls and influent pumps, and its belt press dewatering system was replaced by a centrifuge. Another plant received a new aeration system and centrifuge dewatering. All plants received lighting improvements and other smaller efficiency projects.
The dewatering upgrades will enhance performance at the Puerto Nuevo plant’s biosolids incinerator to meet new limits on mercury emissions. “We’ll be burning the material and making steam to generate electricity,” says Chase. “We should get about 75 percent of the electrical needs of the plant.”
The incinerator burns solids from three wastewater treatment plants; reducing water content increases electrical generation while saving on transportation. Honeywell adapted technologies from the mining industry to help make the project affordable — less than half of what the authority had budgeted.
Two drinking water plants, each more than 100 mgd, are receiving new pumps, and one will have a major electrical upgrade to support synchronous bypass controls. “It has one variable-frequency drive that can be applied to any one of the five pumps,” says Chase. “VFDs are expensive, so we have the redundancy of five pumps and only have to buy one VFD. We have the cost reduction, the redundancy and the energy savings.”
Honeywell used Flygt pumps on all the wastewater projects. Blowers came from Houston Service Industries, diffusers from Environmental Dynamics International and centrifuges from Alfa Laval.
In addition, the authority is replacing a 1.1 MW hydroturbine at the Carraizo Dam to increase its generation. That alone will save about $1 million a year in purchased power. The utility has also signed a series of purchased power agreements that will provide around 40 MW of renewable energy at reduced rates from 11 to 16 cents per kWh, saving $1.2 million annually.
Internally, the authority has been optimizing its system since 2009. It has eliminated 10 water treatment plants, eight wastewater plants and about 300 pump stations. Another 17 treatment plants are planned for retirement by 2018. An initiative to identify and reduce water losses is already paying dividends. Nonrevenue water has been reduced from 62 percent to 58 percent in two years.
Getting it done
Six plants have individual performance contracts. Planning at each began with a walk-through. “We take a pretty high-level look,” says Chase. “We try to get the best readings to assign energy load to everything. We don’t just use nameplate ratings. We put data loggers on equipment and monitor it for a period of time. We put a lot of effort into defining what energy they’re using and where they’re using it.”
Operational improvements also contribute to more efficient processes and improved operations. “They had six 900 hp and three 350 hp centrifugal blowers at the Barceloneta wastewater plant,” notes Chase. “That’s a lot of equipment to maintain. That all goes away and you have five high-speed turbo blowers in their place, and we took a digester offline.”
Honeywell will handle preventive maintenance on the new equipment for the life of the contracts, and the schedule is aggressive. “Electricity costs are high, so you get the benefits back from things like diffuser cleaning a lot sooner,” says Chase. “In places where power costs are lower, that cleaning schedule may be double what we see in Puerto Rico.”
Capital vs. O&M
Dave Robinson, Honeywell energy services senior marketing manager, adds that many treatment plants have been delaying capital expenditures for lack of funds: “We see more and more that they are deferring upgrades three or four years. The net effect is to lose all that energy savings during that time. They’re spending money on energy when they could be putting it into capital improvements instead.”
Ramirez adds that once work at the first six facilities is completed, the authority will continue with other projects across its system as it updates its strategic plan every two years. “It’s a very holistic approach,” she says. “We’re doing a lot, and we’re seeing the results.”
That includes monthly metrics to guide more than 5,000 employees through the changes needed to achieve the strategic goals. “Employees say it is good that they have clear goals that are achievable,” Ramirez says. “We have seen the cultural change. It’s been a very positive experience. Challenging, but we’re working really hard.”