Rehoboth plant cited for sludge discharge

Brown discharge into the Rehoboth Beach wastewater treatment plant found its way into the Lewes-Rehoboth Canal in July leading to the plant being cited for a violation of its discharge permit by Delaware Department of Natural Resources and Environmental Control.

According to DNREC, the U.S. Coast Guard received a citizen complaint about a discharge of brown solids from the outfall pipe at the plant on July 10. The citizen supported his report with photographs showing brown liquid from the outfall pipe at the plant that empties into the canal.

“These photos clearly show a heavy dark brown colored discharge exiting the outfall and a blanket of dark brown floating solids, scum and sludge deposits emanating from the discharge point out into the Lewes-Rehoboth Canal,” said Glenn Davis, program manager of DNREC’s surface water discharges section, in a letter to plant manager Bob Stenger.

On July 11, Stenger contacted DNREC to report that the plant was having problems with solids in the clarifiers - the large sediment tanks that are intended to remove solids from the effluent.

A DNREC investigation showed that the plant experienced problems with filamentous bacteria in the clarifiers. At the right levels, filamentous bacteria can be helpful in wastewater treatment because it helps break down solids in the effluent.

“Excessive growth of these filamentous bacteria can cause potential problems with sludge settling.  Bulking and foaming are considered the major problems caused by excessive amounts of filamentous bacteria. Bulking - rising sludge - can occur and the activated sludge that usually settles to the bottom of the clarifier can rise to the surface of the clarifier, and be carried over to the effluent discharge,” said DNREC spokesman Michael Globetti.

Globetti said the plant initiated steps to control the filamentous bacteria immediately, and is once again showing very low solids in their effluent.

DNREC’s investigation also showed that the plant’s micro screens, which filter out smaller solids, were not working.

The department cited the plant for discharging pollutants to the surface water and not having working micro screens. The city is required to submit a formal report and plan to address the violations within 30 days of the notice of violation, dated July 26. Mayor Sam Cooper said the city has begun to undertake its report and he expects it to be done within the 30 day time period. He said DNREC did not find any violations of the city’s discharge limits or any suspended solids.

The city has plans in place to give the plant a $10 million upgrade as part of the city’s ocean outfall project, which would move the discharge from the canal to a site in the ocean 6,000 feet off Deauville Beach. Cooper said part of the upgrade is to replace the micro screens, which he acknowledged the city has known to be a problem for years.

However, he said he was frustrated that the process has taken so long - the city has been seeking an alternative to dumping in the canal since 1998 - mainly because of the time it took to find an alternative, secure $52.5 million in state funds to undertake the project and going through the state and federal permitting process.

Cooper said he is not concerned about the perception the recent violations will have on the ocean outfall project, mainly because of the upgrades in technology to the plant. He said the city hopes to seek bids for the plant improvements within a year, although construction on the outfall will not come until later due to permitting and selecting contractors for the work. The city plans to have three contractors work on the project: one to build the pipe, one to perform the plant upgrades and one to build the discharge point in the ocean.