HOFOR (Greater Copenhagen Utility) is the result of a merger between Copenhagen Energy and the water utilities in Albertslund, Brøndby, Dragør, Herlev, Hvidovre, Rødovre and Vallensbæk municipalities.
Every year, HOFOR distributes 52 million cubic meters of water to 1 million customers and manages 14 waterworks and more than 4,000 kilometres of water and wastewater pipelines.
HOFOR's water loss was previously at 9 per cent, but is now down to 5 per cent.
Area surveys every three years
A close eye - not to mention ear - is kept on leakages in water pipes in HOFOR's supply area. HOFOR has divided the City of Copenhagen into 76 map areas. These areas are surveyed at three-year intervals. The seven other municipalities under HOFOR follow the same three-year cycle.
Area surveys are carried out by allocating an employee to each of the 76 areas. The task for each employee is to go out and check the section valves marked on the map. While doing so, the employee will listen to the valves and make a note if they hear something that might indicate a leak nearby.
Once the next valves have been inspected, the employee will return to the noise for a closer listen. This time, the employee will also listen to the stopcock in order to ascertain whether the noise stems from private land.
The next step is to pinpoint the leak by using correlation: Two acoustic leak correlators are placed along the stretch of pipe where there is a suspected leak. Finally, a subsurface acoustic sensor is used to register any noise made by small rocks and other materials clattering near the leak. The results are then compared to the results of the correlation. The excavation point can now be marked and a contractor can be called in.
Pressure and flow meters instead of compartmentalisation
While surrounding municipalities have been compartmentalised, HOFOR has investigated whether it would make sense to compartmentalise the pipeline grid of the City of Copenhagen. It was assessed that doing so would jeopardise the water supply to the many industrial businesses, as well as sprinkler and fire-fighting systems in the city. Instead, 24 meters have been fitted so that HOFOR can constantly monitor pressure and flows in different parts of the pipeline grid and react to any abnormal changes.
Focus on particularly vulnerable areas
HOFOR has special focuss on certain areas of Copenhagen. These include the cobbled streets and roads in Østerbro. Large leaks will most often be visible at ground level. However, if a leak occurs here, the material below the cobbles will be swept away and the cobbles will become lodged together. At some point cave-in when someone drives or walks across the surface.
In order to keep abreast of leaks in particularly vulnerable areas, HOFOR selects a larger area and erects 20-25 noise loggers. After 48 hours, the data will be collected and plotted onto a map. A blue label on the map indicates that the noise logger did not register anything unusual. A red label indicates that the noise logger has registered a sound nearby. After this, personnel are dispatched to inspect the area using correlation and subsurface acoustic sensors.
HOFOR ascribes much of its success at keeping water loss to a minimum to its personnel in the field. HOFOR management has prioritised employee training so that personnel have the correct tools and allocate sufficient time to search for leaks. This has had a positive derivative effect on employee commitment.