London and Quadrant (L&Q) have successfully installed and adopted a chemical-free water treatment approach to their district heating system at Bollo Bridge Road in South Acton.
“I have seen great results on this problematic site using the IWTM's chemical free solutions and will be looking at this for future installs, as well as retro-fits where the system water quality condition requires attention”
The site was suffering from poor water quality and corrosion resulting in component failures on pumps, pipework, boilers and heat interface units resulting in disruption and downtime of the system leaving residents without heating and hot water on more than one occasion.
To try and control the corrosion more chemicals were added, a costly process which only accelerated the issues as overdosing with chemicals introduced even more problems with seal and gasket failures and increased conductivity.
Faced with another chemical clean quoted at £27k alongside more disruption and downtime the Senior Building Services Engineer at L&Q decided to adopt a different approach and to follow the VDI 2035 German standard for chemical-free water treatment.
Water samples were taken and laboratory tested so the starting point was known and a magnesium anode reaction tank was installed in a side stream application replacing the existing side stream filter and chemical dosing pot.
To work with the reaction tank a demineralisation unit was installed on the pressurisation unit. The unit provides demineralised water on demand using an ion exchange resin bed to remove harmful salts, alkaline and hardness. This ensures that any raw fill water is low in conductivity with has a controlled pH of 8.2. The cost of these two items of equipment was just £9,500 making the ROI instant.
The system was installed over two days by a single engineer with no draining down, no effluent discharge, no interruption to supply and no loss of service to the residents. The chemical free solution then commenced its gradual non-aggressive clean which filtered the 28,800 litre system volume which passed through the reaction tank every 24 hours. During this cleaning period the magnesium hydroxide breaks down sludge and scale and brings it back to the unit ready to be blown down as part of the PPMs.
45 days into a 90 day proof of concept sign off was given as the bacteria which was present in the system had been removed to the level required by VDI 2035 (a standard which is stricter than BSRIA). A blow down procedure to flush out the collected debris was carried out monthly along with regular laboratory analysis on the water. Despite considerable remedial works during the trial period the water quality was maintained by the self-regulation of the anode and because the fill water was demineralised.
The client's new service company who carried out the rectification works now look after the simple maintenance of the system, knowing that all is required to maintain the VDI levels is to ensure the anode is replaced every three years at a cost of £575.
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