How Biofouling Control Saves Energy Consumption and Maintenance Costs

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A flange or a valve, which is closed, is a part of the piping system, where there is no water flow. This is called a dead end or a dead leg. These are the critical areas in every water system. A portion, where there is no flow of water, is the typical place where corrosion or biofilm will start taking place in a water system.

Contextually, microbial biofilms develop when microorganisms irreversibly adhere to a submerged surface. Once there is a biofilm established in a system, the biofilm creates biofouling, and in a lot of cases the biofilm will contaminate the whole water system.

Solving the Biofouling Problem

Adding chemical inhibitors or introducing heat is able to solve the problem in the parts of a water system, where water is flowing. In a dead leg, adding chemicals or using UV-light does not solve the problem, because the water in this dead end is not circulated, it is mostly local in this flange. So, bacteria, algae or biofilm can grow there, and are not affected by the chemicals added to the system or by heat. The common dead leg definition is implicated in the Good Manufacturing Practice. (GMP) wording, which says, “Not to have an unused portion greater in length than six times the diameter of the unused pipe – measured from the axis of the pipe in use.”

Action and observation of Pipeworks

In the return line of the cooling loop, so called biocide was added in the water to stop the growth of algae. But, at the cooling tower heavy growth of algae was found. These algae had been taken by the water from the cooling tower and contaminated the entire system. The biofouling or biofilm was forming a slimy film on the inner surfaces, this film was reducing the heat transfer drastically – and so the cooling was not sufficient anymore.

After survey, the comapny decided to install Merus Rings at different strategic locations throughout the cooling loop to get maximum results, with as little as possible investment from the customer’s end. During demo, the cooling H₂O loop was running with full capacity, in order to get the system cleaned as much as possible.

Results after two months

Exactly after two months, the spots checked before were opened again. It was clear to see that a lot of the existing fouling was proactively removed, and the inner surfaces of the pipes started to get clean. Even old corrosion spots were slowly fading away. The rust was taken downstream and was settling in the sump of the cooling tower. The corrosion rate, which had been in average 8.5 Mils Per Year (MPY), lowered in the two months to less than 1.5 MPY.

* The author is the Director – Operations at Merus Engineering

* Pvt. Ltd., India. Tel.: +91 9833875336

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