Efficient Pump for multiphase Mixtures in Wastewater Treatment Plant
Dissolved air flotation (DAF) is a frequently used treatment method in wastewater treatment. The air-mixed liquid represents a major challenge for pumps. Energy efficiency is also very important. This is a case for the EDUR multiphase pumps, which as a unique product differ in their characteristics significantly from common centrifugal pumps. The basic idea is to use the pumps not only for fluids but also for liquid-gas-mixtures and gas enrichment as a dynamic mixer.
Task
The wastewater treatment plant Bülk handles approx. 20 million cubic metres of wastewater of the city of Kiel and surrounding communities each year. For the treatment of cleaning water from the cloth filtration originally a conventional system with dispersion pumps, compressors and pressure tanks was used. Four standard pumps with 15,0 kW drive power each were installed as dispersion pumps to feed the recycled water to the pressure tanks with approx. 8 bar for air saturation. For the air saturation of the recycled water a pressure tank, two dissolving tanks and two compressors with 14,0 kW output were additionally installed.
A similar system was also used by a communal wastewater treatment plant in the USA. A total of eight circulating pumps with 160,0 kW each was used. Four compressors with 7,5 kW output each additionally were installed. The total requirement was 1.310 kW.
Solution
The system of the wastewater treatment plant Bülk was replaced by three newly developed EDUR multiphase pumps of type LBU 603 D160L with 15,0 kW drive power each, whereby one of these three pumps serves as a standby pump. All three components (dispersion pumps, pressure tanks and compressors) were replaced by multiphase pumps during the retrofitting. By throttling down the pumps to approx. 0,2 to 0,3 bar artificial vacuum at the suction side, the pumps suck the required air into the pumped liquid. The pumps simultaneously operate as a dynamic mixer and, due to the increase of pressure to approx. 8 bar, achieve an excellent solution. This causes a fine-bubble dispersion of the pumped liquid during the pressure release which leads to an excellent flotation result. By operating in three shift system during assumed 220 working days, the energy savings only amount to more than 100.000,00 € (at 0,10 € / kWh) anually.
An EDUR system with twelve multiphase pumps LBU size 6 with 22,0 kW each was installed in the USA without any compressors. Only 264,0 kW are used in total after this plant modification.
