Smith, Bruce, Lukegord, John, Mueller, Mark. 1998. Alternative to Mechanical Cleaning for Blue Mussel Fouling in Main Circulating Water Condensers.

The Salem Harbor Station of the New England Electric System, located north of Boston, MA, has been plagued in recent years with severe fouling due to blue mussels (Mytilus edulis) in the main condensers. The problem manifested itself to a point where condensers were entered on almost a nightly basis to maintain full operating capacity on three of the units.

A test was undertaken three years ago on Unit 4 to minimize macro-fouling problems with the main condenser. A blend of cationic surfactants (n-dodecylguanidine hydrochloride and n-alkyl dimethylbenzyl ammonium chloride) was shown in screening studies to be effective in controlling blue mussels and was approved for use by the Massachusetts DNR and USEPA. With respect to the condenser cooling system, blue mussel colonization occurred almost exclusively in the intake pump bays and not in the piping system. The proposed treatment plan involved proactive, 24-hour "Static Treatments," of the intake pump bays, at eight to ten week intervals. At that frequency it was hypothesized that blue mussels would be prevented from attaining a size where they would plug main condenser tubes. The other operating units served as controls to assess the performance of the treatment program on Unit 4.

Static treatments were performed with the unit off-line, and the cooling supply isolated from the intake box with the use of stop logs. This effectively creates a cavity, isolated from the cooling water supply and the main circulating water pumps. With the intake box isolated, air lances are placed in strategic locations, and the traveling screens kept operational. The blend of surfactants is injected into the intake bay to achieve a total concentration of 5.2 ppm active surfactant. The surfactant solution is allowed to remain in the intake bay for 24 hours, after which bentonite clay is added to adsorb and inactivate the surfactants. The evaluation has been in progress for the past two years.

Results to date have shown the technique to be a favorable alternative to mechanical cleaning. The main condenser on Unit 4 has not been opened in the past two years for the purpose of manual removal of blue mussels from the tube sheet. By contrast, Units 2 and 3 required frequent manual tube sheet cleanings and, during scheduled outages last spring, yielded blue mussels from their intakes in the amount of 63 and 65 tons, respectively. The paper reviews our two years of experience with application techniques, environmental impacts, comparative economics, and performance of the cationic surfactants for blue mussel control.

Contact: Bruce Smith, BetzDearborn, 200 Witmer Road, Horsham, PA 19047
Keywords: Chemical_control, Prevention, Nonindigenous
Product Type: Publication, Proceedings
User Type: Industrial_and_Municipal