The air-conditioning systems within the twin office towers at Purdy's Wharf, one of the most distinctive landmarks along the waterfront in Halifax, Nova Scotia, have been protected against some of nature's smallest, but most damaging creatures - mussels.

Like many other buildings in shore-line locations, the office towers use seawater as a cooling agent.

The pumps, piping and valves were made of highly corrosion-resistant materials, but it was realised that mussels could be a serious problem if not guarded against and, therefore, the building was originally protected by a chlorine injection system. Later, another solution was provided by Cathelco Ltd., the British specialists in the design and manufacture of electrolytic anti-fouling systems for ships and shoreline applications.

The air-conditioning systems in the twin towers of Purdy's Wharf, Halifax, Nova Scotia which use sea water for cooling purposes, are being protected against mussel growth in pipes and valves by a British made system from Cathelco Ltd.

Seawater, in volumes of up to 2,500 US gallons per minute, enters the system through submerged inlets on the harbour floor which are 75 feet below the low water mark. It then travels through two 600 ft. pipelines to the base of the towers where it is raised by pumps to the air-conditioning heat exchangers.

The Cathelco system prevents barnacles and mussel blockages by using the electrolytic method, avoiding the use of harmful chemicals. Pipework, pumps and ancillary equipment are protected by copper anodes which are fed with an impressed electrical current resulting in the production of copper ions. Although concentrations are less than 24 parts per billion, they are sufficient to prevent crustacea from settling and multiplying.

By locating the anodes at the seawater inlets at Purdy's Wharf, all of the water entering the pipework is dosed with ions. These are carried throughout the system, protecting it against marine growth.

Another important reason for the choice of this system was its relative simplicity and safety in operation, and the two to three year pay-back period for the initial capital cost of changing the system.

The firm's anti-fouling technology has been proven in over 2,000 marine and shore-based applications.