Drinking water on board
With up to 70,000 passengers daily and more than 20 million passengers annually, Düsseldorf International Airport is the third largest in Germany. Almost 20,000 people are employed to keep the airport running smoothly and safely. When it comes to safety on board aircraft, nothing is left to chance – including the drinking water on board, which is disinfected using the Grundfos Oxiperm Pro system. To find out more about the Düsseldorf Airport solution click on the next tab, and to find out more about water disinfection, click on tab 3.
Oxiperm Pro and chlorine dioxide
The Oxiperm chlorine dioxide disinfection system has a number of advantageous compared to other systems. These include:
- Chlorine dioxide is able to disinfect even in low concentrations
- It is effective against the biofilms in which bacteria can grow
- There are no discernable by-products, such as the smell of chlorine
- It has a long residual time in water
- Integrated control system
- Exact dosing using digital dosing pump.
Reduced operating costs
A further plus with the system is the elimination of the risk of corrosion in the pipes and the subsequent cost of replacing them. The Oxiperm system produces chlorine dioxide using diluted solutions of sodium chlorite (NaClO2, 7,5%) and hydrochloric acid (HCl, 9% in a volumetric 1:1 relation. Other systems use a 1:3 relation to produce chlorine dioxide, which risks the diluted hydrochloric not reacting to chlorine dioxide and therefore corroding the pipe material.
On board the aircraft, drinking water is used for making coffee, heating food and in wash hand basins. At Düsseldorf International Airport, aircrafts have their 400-800 litre tanks filled with disinfected water delivered by special fresh water-refuelling vehicles.
The drinking water is passed through a water filter and a system separator to an electromagnetic measuring water meter. The meter measures the flow and passes a 4-20mA signal on to the Grundfos Oxiperm Pro system.
While the vehicle is being filled with drinking water, the Oxiperm Pro system doses the correct amount of chlorine dioxide into the drinking water. The system has a stepper-motor driven dosing pump installed that ensures the precise quantity of chlorine dioxide is delivered, using the signal from the water meter to do this. The concentration is checked by a chlorine dioxide measuring cell that sends the value to a two-channel recorder. The German drinking water regulations specify that the concentration be recorded, but this is no problem with the integrated Oxiperm Pro solution. It is even possible to define a limit value in the control system to eliminate any possibility of over-dosing.
The Oxiperm system supplied by Grundfos ensures that the airport lives up to all the standards and regulations. The system supplied consists of the following components:
- 2 Oxiperm Pro 5 g ClO2 / h
- Digital dosing pump DDI209
- 2 chlorine dioxide measuring cells Aquacell
- Chlorine dioxide gas warning device DIS-G
- Two-channel writing capability
- Grundfos’ start-up assistance and after-sales service.
Regulations and standards
The Public Health Department takes a monthly water sample from the refuelling vehicles to ensure all drinking water standards are met. Drinking water for aircraft is covered by a special set of standards known as DIN 2001/part 2, as well as European aviation industry regulations and, in the case of Düsseldorf International Airport, German regulations. Finally, there is an IATA (International Air Transport Association) guideline for the actual fuelling of drinking water on aircraft, which states that aircraft may only be fuelled with drinking water 30 minutes before take-off.
Safe drinking water
Even well managed water resources can become infected with microorganisms, where bacteria can multiply in tanks, pipes and water handling equipment under the right conditions. Water treatment is therefore an important element in keeping drinking water safe.
Typical treatment methods
The availability of safe drinking water is vital, whether on aircraft or anywhere else. To ensure this, a number of methods of water treatment are available. Read on to find out the pros and cons of the solutions that are typically used. The conclusion is clear – the chorine dioxide solution of the Oxiperm Pro system is the best solution for water treatment and disinfection. Methods for treating water typically include:
- Chlorine dioxide: Chlorine dioxide does not react with water but dissolves physically. It kills microorganisms in the water by causing irreversible oxidative destruction of the transport proteins in the living cells. It works against bacteria and also viruses, bacteria, fungi and algae. Also, as opposed to the other methods, it is effective in removing biofilm even with low doses.
- Thermal treatment: Often used to combat the Legionella bacteria that can be found in water systems. The water in the system is heated to above 70oC to kill the bacteria.
- UV radiation: Water is disinfected by being radiated with ultra-violet rays with a wavelength of 254 nm. A UV-bulb is used for radiation of the water. The UV rays damage the genetic information and reproductive systems of the bacteria.
- Filtration: Ultra- or microfiltration uses membrane systems to filter out bacteria, viruses, suspended particles and other unwanted elements.
- Ozone: Ozone is a sanitizer produced by passing oxygen through a high intensity electrical field to form ozone gas. Once generated it breaks down rapidly and must be used immediately. It is also non-selective and reacts not only with organic compounds but all materials that can be oxidized, including pipe sealings and materials.
- Chlorination: Three processes are used, including chlorine gas disinfection, electrolytic chlorine generation and dosing of liquid sodium or calcium hypochlorite. All three methods produce hypochlorous acid (HCIO), which acts as the active disinfectant in the water. The methods are not, however, as effective as the use of Chlorine dioxide.
Characteristics of typical disinfection solutions