Solar energy helps an updated Maryland wastewater treatment plant cut utility power costs. A blower upgrade will soon follow.
When the Town of Hurlock, Maryland, upgraded its wastewater treatment plant to meet new effluent limits, the project cost $7.5 million and operating costs went up. Today, the plant is saving money through renewable energy and more efficient equipment.
A solar photovoltaic system activated last September will help, as will new high-efficiency blowers being phased in to reduce electricity demand.
Ten years ago, Hurlock replaced its 2 mgd lagoon plant with a 1.65 mgd four-stage Bardenpho activated sludge facility with enhanced nutrient removal to meet effluent standards of the multistate Chesapeake Bay Watershed Agreement. Maryland set a nitrogen limit of 4 mg/L, and the plant’s annual average is 2.6 mg/L. The phosphorus limit is 0.3 mg/L, and the plant’s annual average is 0.05 mg/L.
Designed by Reid Engineering, the new facility was named the 2008 Maryland Rural Water Association Wastewater Treatment Plant of the Year and won a 2009 U.S. EPA regional award for operations and maintenance.
“The lagoon system was cost-efficient; we just weren’t getting good effluent numbers like you do with an activated sludge plant,” says Eric Barnhart, wastewater plant superintendent. Each of the four lagoons covered 30 acres; one is now used for biosolids storage and another is being kept for emergency use.
“It’s a lot cleaner water. It looks like drinking water when it comes out of here,” says Barnhart. But the new plant uses about $20,000 a month in electricity and $18,000 a month in chemicals, versus $3,000 and $1,000 for the old plant.
To help offset some of that added cost, the town (population 2,200) pursued a purchase power agreement for the solar system with VW Energy of Severna Park, Maryland. John Avery, town administrator, saw the company’s display at a Maryland Municipal League conference. The $2 million solar array provides about 1.4 million kWh annually. VW Energy funded the project and owns and operates it.
The town provided only the 5 acres of land for 3,420 solar panels on 114 fixed-array tables. “We buy electricity from VW Energy, and it saves 10 to 12 percent on our electric bill,” says Barnhart. “After 20 years, we’ll save about $500,000 and the system will belong to us.”
The plant will soon switch to all LED lighting, a change already made at the water treatment plant and town office building. But next on the list of energy savings is changing out blowers.
Most of the plant’s influent is from two food processing facilities with high organic loads. About 70 percent is from a poultry processing plant and 5 to 10 percent from a food processing plant that makes pickles, spices and brand name prepackaged items. Both facilities pretreat their waste to 425 mg/L BOD and 500 mg/L TSS. Those Monday-through-
Friday flows add up to about 1 mgd, some of it held in a 2.5-million-gallon flow equalization tank for treatment on weekends.
Even though the existing blowers are just 10 years old, more efficient blowers are now available. “We just ordered two 75 hp Atlas Copco blowers that will save 30 percent on electricity,” says Barnhart. “Over the next three years, we’ll phase out the other three blowers and replace them with the Atlas Copco models.”
As one of the largest municipally owned solar installations in the state, the Hurlock facility is helping the plant be more sustainable both environmentally and economically for its ratepayers.