Looking into Lewes wastewater treatment crisis
“We’ve put out the fire, now we’re going back and looking at causes and solutions,” said Preston Lee, president of the Lewes Board of Public Works.
The fire in this case was failed wastewater treatment. The Delaware Bay is getting burned.
The Lewes wastewater treatment plant started releasing partially-treated wastewater on Dec. 19. It went on for nine days, and then for about two hours more in a separate problem on New Year’s Day.
According to the Department of Natural Resources and Environmental Control, water flows from the Lewes Rehoboth Canal into Roosevelt Inlet, then into the Delaware Bay, a body of water already struggling with pollution.
The problem at the treatment plant might be under control, but fish aren’t exactly breathing a sigh of relief. They might not be breathing much of anything.
The chemicals in partially-treated wastewater that affect marine life are primarily nitrogen and phosphorus. Both are useful nutrients, but in large quantities, they cause excessive plant and algae growth, depleting the oxygen for fish and other marine life.
According to Center for the Inland Bays Executive Director Chris Bason, excess nutrients are Delaware’s number one water quality issue.
“Low oxygen problems affect all our fish and shellfish,” he said. “All our estuaries are nurseries for these baby fish and shellfish-blue crabs, sea trout, summer flounder, even striped bass to some extent. They all grow up here, that’s why estuaries are so important. And young fish are particularly susceptible to these conditions.”
A failed alarm
The Lewes wastewater treatment plant is about 12 years old and is still considered state-of-the-art. At this time of year, it processes about 325,000 gallons of wastewater a day.
White Marsh Environmental Systems, a wholly-owned subsidiary of Tidewater Utilities Inc., runs the plant and has since 2017. Lee doesn’t blame them.
“This was a total shock. This was such an anomaly. The meter problem is not a common one,” he said.
Though his suspicions have not yet been confirmed, Lee and others at the plant believe the malfunction occurred because a meter failed to alert them that solids were building up in the final phase of the treatment system.
“There’s a vacuum … that pulls the water going by into these tubes, and the openings in the tubes are microns [in size]. They are very, very, very fine filters,” Lee said. “And periodically, like any filter, it has to be backwashed to blow away things accumulated against the filter.”
Those filters, also referred to as membranes, cost about $250,000 and are manufactured by Suez Water Technologies and Solutions. There are four sets in the treatment system.
“One filter had a failure and solids got through,” Lee said. “The meter … is supposed to send an alarm and shut down the system when it detects solids. For some reason that didn’t happen, so when it came time for the backwash, the solids got stuck.”
That created a chain reaction.
The second failure, which resulted in the release of partially-treated wastewater for about two hours on the night of Jan. 1, was due to a different problem.
When the plant went back to fully treating wastewater, only one of the filters was in operation. The solids that would normally build up on four filters built up much faster on one. Rather than allowing the pressure to build up and break the new filter, which would mean again releasing partially-treated wastewater for days, the staff paused operations for two hours while they made adjustments.
“It wasn’t really a failure, more of a startup problem,” Lee said.
The Lewes Board of Public Works is continuing to investigate. Representatives from Suez were at the plant Jan. 9 to analyze the malfunction.
“What we have to address, I think, is to make sure all the meters are working properly and maintained,” Lee said. “The tank the clean water goes in, we may put a meter in there, too, so if any of the other meters fail [to detect solids] we can pick it up there.”
Where will it end up?
In a press release about the partially-treated wastewater release, the Department of Natural Resource and Environmental Control said that past studies determined that “net flow” of the Lewes discharge travels northwest, through the canal and into Delaware Bay, not southeast into Rehoboth Bay.
“I think it’s important to note there have been studies that have shown that a small amount of the discharge from that facility does enter the inland bays,” Bason said.
According to the Lewes Board of Public Works’ National Pollutant Discharge Elimination permit fact sheet, one study found that somewhere between 0.3% and 5% of the discharge reaches the Rehoboth Bay. The inland bays’ water quality is also degraded by pollutants from other sources.
DNREC has issued an emergency shellfish closure in the lower Delaware Bay, from the Mispillion River Inlet to The Point at Cape Henlopen State Park and east to New Jersey. The closure will continue through Jan. 18, 2020.
The ban applies to clams, oysters and mussels. Crabs, conch and fish are not affected.