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Controlling Crustacean infestations in pipelines

17 October 2013

A study undertaken by Aquatic Sciences Inc. has demonstrated that the ENiGMA Electronic DeScaling System can successfully control the settlement of crustaceans in pipelines.

The research was carried out over a six-week period along the Welland Canal in Southern Ontario where densities of Zebra Mussels have historically exceeded 20,000/m2. Results showed that the ENiGMA system had reduced the amount of molluscs by up to 97%.

Molluscs in the Great Lakes affect industry and small-volume water users by clogging pipes and intake structures.  Industries in infected areas regularly treat the water with oxidants, heat or molluscicides to eradicate mussels from the service water system.  Heightening awareness of aquatic environments and health issues has resulted in increased regulations and lower discharge limits for chemical treatment resulting in industry now requiring alternative methods to control infestations.

The ENiGMA system is extensively used in industry throughout the world to control fouling resulting from the build-up of hard water scale.  Industries in Japan found that the system not only controlled scaling but also crustaceans in the pipe system to a heat exchanger. This observation led ENiGMA to hypothesise that the ENiGMA system may also control mussels.

Crustaceans and mussels are similar in the way they use calcium. They both convert calcium, in a free ion form, to calcium carbonate to construct their shell or exoskeleton.

ASI set up a study to determine whether the ENiGMA system inhibits mussel settlement compared to an untreated control system. Using a research trailer, ASI installed a 200-gallon head tank filled with canal water at the north end of the trailer.

The test and control systems were gravity fed by the head tank. One inch PVC tubing was connected to a 1inch ball valve and to a 1” gate valve on the head tank. The control chambers were connected to the ball valve outlet and the ENiGMA test system and chambers were connected to the gate valve outlet.  The 1” tubing leading from the gate valve was connected to an 18” length of 2” inch galvanised steel pipe.

Signal cable leads from the ENiGMA unit were wrapped around the steel pipe which in turn was connected to the test system which consisted of a set of three test chambers (bio boxes) simulating the mussels' preferred colonisation environment.

Three 0.015 m2 PVC culture plates were placed in each test chamber to measure zebra mussel settlement. Constant flow rates, through control and test bio boxes, were maintained by manipulating ball valves leading into the bio boxes. Technicians took measurements daily recording conductivity and water temperature for the control and test systems.

At the end of the test, the culture plates were removed and samples taken for analysis. It was found that the density of the mussels on the plates treated by the ENiGMA unit was 10 times lower than the plates of the control. These results confirmed that the ENiGMA unit inhibited the settlement of mussels.

This research will have a significant bearing on a number of industries in the UK, which are situated on the coast and use seawater for cooling such as nuclear power stations. It will also prove of interest to the shipping industry, which often finds molluscs affect water inlet pipes, as well as countries using desalination plants. 

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