Bio Fouling at a refinery in Dubai removed and stopped

The refinery ISO OCTANE in Dubai, UAE is a rather small refinery. The refinery is not operating constantly but is used the only batch wise. Due to this mode of operation, the cooling loop is not running at full capacity all the time. The cooling loop is operated with limited water circulation if there is no production in the refinery. During as inspection, of the cooling water system, there was found a heavy fouling, caused mainly by organic material. The so-called biofilm caused by biofouling.It was found that this fouling is the same in the entire system.
A flange or a valve which is closed and has two dead end pipes full of biofouling 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 parts in each 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. 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. The problem of such biofilm is they might house bacteria, which might cause MIC, corrosion caused by the microorganism.
Adding chemicals 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 is not solving the problem, because the water in this dead end is not circulated. It is mostly located 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 GMP (good manufacturing practice) 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.” 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 have been taken by the water from the cooling tower and have contaminated the entire system. The biofouling or biofilm is forming a slimy film on the inner surfaces, this film is reducing the heat transfer drastically and so the cooling was not sufficient anymore.
After survey at the side, it was decided to install PursanovaTMDisk at different strategic locations throughout the cooling water loop, in order to get maximum results, with as little as possible investment from customer, side. During the demonstration, this open cooling water loop was running at full capacity, in order to get the system cleaned as much as possible.
Exact after two months the spots checked before have been opened again. It can be clearly seen, a lot of the existing fouling is removed, and the inner surfaces of the pipes start to get clean.
Even old corrosion spots are slowly starting to be removed, the rust is taken downstream and will settle in the sump of the cooling tower.
How long it will take to remove all the corrosion cannot be determined. This will have to be seen over time. The corrosion rate which has been in average 8.5mpy, has lowered in the two months to less than 1.5MPY.