Outfall one more step in improving Rehoboth Bay

By former Mayor Sam Cooper's reckoning, Rehoboth Beach has been discharging treated wastewater from its sewer system into the Lewes-Rehoboth Canal since about 1938. That's 80 years, and all the nutrients in the treated wastewater - primarily nitrogen and phosphorus - have taken their toll on Rehoboth Bay.

In early June this year, that ended. The canal discharge shut down and the new ocean outfall went into operation. Marine scientists, Rehoboth's treatment plant operator and Cooper are all optimistic the result can be nothing but positive.

The worst years for Rehoboth Bay came between 1996 and 2002. Slimy green sheets of sea lettuce, fertilized by a gross imbalance of nitrogen and phosphorus pouring into the bay from Rehoboth and other sources, began to thrive. This rapid growth robbed the water of oxygen. Clammers started finding traditionally healthy and productive beds filled with dead and dying shellfish.

Heaps of the useless lettuce washed up on the bay's sandy shorelines. It stank, drew flies, and began to have the predictable effect. People started leaving communities at the head of the bay where the heaps were the worst. The beaches that had once attracted them for walking and swimming started offending them.

Delaware paid hundreds of thousands of dollars for specialized marine harvesters to attack the sea lettuce and reverse the problem. But that was only treating the symptom. The solution lay at a deeper level.

Bob Stenger credits Kent Price. He said the longtime director of University of Delaware's College of Marine Studies in Lewes pointed his finger at phosphorus as the primary culprit. "He told us we needed to reduce the levels of phosphorus in our discharge," said Stenger. Price, at the time, told the Cape Gazette that one part of phosphorus would trigger 16 parts of nitrogen, making it available as a fertilizer in the system.

Cooper remembers it too. "The state was focusing on nitrogen, but the scientists, including Price and Bill Ullman, told us to forget nitrogen, attack phosphorus. We got a real education in phosphorus."

Cooper said the city made two significant upgrades to the treatment plant between 1996 and 1998. Then another came a few years later. Stenger said the first upgrade focused on getting nitrogen out of the wastewater, the thinking being it was the fertilizer causing the worse problems. "But then, a few years later, based on Price's suggestion, we shifted focus to phosphorus. We installed equipment to precipitate phosphorus out. It didn't take long before our phosphorus loading went from an annual average of about 5,500 pounds - which met government standards - down to about 1,200 pounds." That did the trick.

Sea lettuce left quickly and so did the harvesters.

Dramatic improvement

Ullman, a University of Delaware marine scientist, said the difference made by that last big upgrade at the plant was like night and day. "We watched the water clarity change dramatically in two years. Light started getting to the bottom of the bay again, and healthier grasses began to return. Plants are able to live better in cleaner water. People started seeing bottom in places they hadn't before."

Ullman said everything Rehoboth has done to improve has been good for the bays. "I think the likelihood of sea lettuce blooms like we had before 2002 is very low. We will continue to see improvement. That's presuming that industrial pollution, like the problems we've seen with Mountaire, and continuing population increases don't reverse it. I don't see that happening. Things like that may slow improvement, but they won't reverse it."

Stenger said Rehoboth is continuing to improve the quality of its wastewater treatment. "We recently upgraded filters for removing solids, from a 32-micron mesh down to a 13-micron mesh. That will mean fewer nutrients going into the ocean. Most people say the ocean has a nutrient deficit, but we're going this way anyway."

Cooper said after more than 100 meetings through the last two decades with lawyers in D.C., EPA officials in Philadelphia, DNREC regulators in Dover, and private and Sussex County engineers and officials, he's happy that the outfall project is finally online and that there were no major construction glitches to hold up progress.

"I'm still a firm believer that ocean outfall was the right decision. Our freshwater supply has never been a problem, so taking that water out of the ground and putting it in the ocean was never a good argument. The biggest concern is keeping contaminants out of our ample groundwater supply, and there were concerns that going with spray irrigation could upset the chemistry of the soils, affecting the groundwater."

George Luther, a marine chemist who lives on Bald Eagle Creek at the head of Rehoboth Bay, has witnessed fish kills, algal blooms and sea lettuce problems through the years. He worked with Price on phosphorus studies focusing on Rehoboth Bay. He said poor flushing in Rehoboth Bay has contributed to problems through the years, and it concerns him that phosphorus does not leave the system as it would in a better-flushed scenario. "There's much more phosphorus out there than in a more natural system. But taking all of it out now should be helpful. I'm optimistic about the bays making a better recovery."

Luther also had a positive take on the nutrients going to the ocean. "The nutrients in the water around the end of the outfall may benefit fishing. They could lead to production of little organisms that get eaten by bigger organisms that get eaten by little fish and then bigger fish. It may be better than people think. Nature always finds a way to use something."