Drinking water treatment
The Next Generation of Waterworks
EUROWATER has supplied the process plant for this ultra-modern waterworks that utilizes the newest technologies for online measurement, aeration and pressure filtration to ensure high security of supply and drinking water safety.
The Danish waterworks of Braedstrup was established in 1909 and for more than 100 years, the waterworks has remained at the forefront of the technological development.
Starting back in 1937, before automated monitoring, the engineer fitted a flotation device with a tall rod so he could keep an eye on the water level from his home with a pair of binoculars. Perhaps this is the first example of analog remote monitoring in Denmark?
In 2015, more than 105 years after the founding, a new and ultra-modern waterworks was ready to supply approximately 2,200 households with fresh and clean drinking water. The hardware and machines are now stainless steel much like in the modern food processing industry. In many respects, the waterworks is at the cutting edge of technological development. It has some of the most advanced equipment for online monitoring of water quality available on the market, ensuring its main purpose: a reliable supply of pure drinking water for the consumers.
Water treatment in closed systems
The water comes from three bored wells. The water extraction scheme is based on the lowest possible operating costs and the “recipe” production is based on analyses of historical data. This means that the water extraction is evenly distributed on all 24 hours – not only on the relatively short periods during morning and afternoon in which the citizens typically use large volumes of water. The raw water pumps are controlled by alternate operation, which means that they operate in turns and that the well in use is switched after a stipulated operating time. This takes best possible care of the source wells and gives a high degree of security that the groundwater quality does not change all of a sudden, resulting in less than optimal water treatment with regards to efficiency.
The water treatment happens in closed systems. The waterworks of Braedstrup used to oxidize the water over a cascade aerator and open sand filters, but because of the obvious advantages of a closed system in regards to hygiene and drinking water safety, the waterworks is now using closed pressure filters.
Before iron and manganese is removed from the water, pure oxygen generated by an oxygen generator is added. The use of pure oxygen gives optimum conditions for controlling the oxygen dosing, resulting in the most efficient filtration process.
The aeration and filtration processes happen in two independent production lines. Each line has its own oxidation equipment and two stainless pressure filters, each with a treatment capacity of up to 100 m³/h. The normal operation is approximately 40 m³/h, providing a high degree of flexibility and supply reliability in the production system. The treated water is stored in two independent clean water tanks. The technical facilities as a whole are doubled so that one line can be disconnected for preventive maintenance while the other produces drinking water, thus ensuring a very high supply reliability.
Roughly 270,000 m³ of water are pumped to the town of Braedstrup and its surrounding area per year amounting to an average daily consumption of 740 m³.
Measures against bacteriological contamination
In the event of bacteriological contamination, a bypass has been installed on the outlet of the waterworks as part of a contingency measure. This means that operation quickly be restored by connecting a mobile UV system for disinfection of the water. SILHORKO-EUROWATER A/S has a number of rental units for this purpose. In this way, the consumers are guaranteed a safe and good supply of drinking water.
Online measurement of water quality
Reliable, regular and quick measurements of selected water parameters are crucial for controlling the water quality. The measurements are used in the internal inspection of the waterworks and are thus a central element in fulfilling the quality standards and compliance with statutory limit values governing drinking water. Furthermore, a stable water treatment process is ensured and downtime is prevented.
In cooperation with HACH, SILHORKO-EUROWATER A/S has designed a special drinking water analyzer for on-line measurement of a number of water parameters, such as turbidity, oxygen, pH, temperature, conductivity, and redox. Braedstrup waterworks has online measurement installed in four places: on raw water, after the two filtration lines, and on the outlet from the waterworks.
Online monitoring of the water treatment process.
Measurements before and after filtration are important tools in monitoring the water treatment process.
Measurements from outlet of the waterworks are important to document the quality of the drinking water conducted to the consumers.
|Measurement parameter||Raw water||After filtration||Waterworks outlet|
Redox is a contraction of 'reduction' and 'oxidation', expressing the extent of groundwater reduction and thus its protection against nitrate percolation.
Conductivity means the contents of dissolved salts in water. Used as a quick method to determine salt content.
pH-value expresses the acidity of water. The value at outlet waterworks must be between 7 and 8.5.
Temperature: Too high a drinking water temperature influences taste sensation and could increase the risk of bacterial growth. There are no water quality requirements for temperature, only recommendations. The pH-electrode of the analysis control has an integral temperature sensor for automatic compensation.
Turbidity: Turbidity is the degree of cloudiness or haziness of a fluid. Turbidity can be caused by very fine particles invisible to the naked eye. Measurement of turbidity is a key test of water quality.
Oxygen: During water treatment, the water is oxidized to filter off iron and manganese, so knowledge of the oxygen level is essential. There must be a certain oxygen content in the pipe system to ensure the good taste of the water and to prevent growth of bacteria, which thrive under oxygen-free, anaerobic conditions.
Measurements from the drinking water analyses are collected in a database and presented on-line in the SCADA system of the waterworks. The number and composition of possible reports generated by the system are almost limitless. Reports can be printed or stored as continuous documentation. Measurements can be exported to other systems and form the basis of causality analysis, which raises the level of knowledge of water treatment. These are important tools for optimizing operation, energy consumption, water quality, etc. The binoculars on the tall rod have been exchanged for present-day remote monitoring.