AERZEN provides energy efficient process air generation in the Kötz wastewater treatment plant Stronger in combination For process air generation, the Kötz wastewater treatment plant selected an ideal solution: the compound system of AERZEN turbo compressors for base load, and AERZEN positive displacement blowers, or rotary lobe compressors, for peak load, to provide failure-free supply of the biological wastewater treatment plant at optimal cost. View over aeration basins 1 and 2 onto the allocated oxygen station. Oxygen station for supply of aeration basins 3 to 6, equipped with two AERZEN positive displacement blowers with air bearings, installed in the year 2000. Hans Kempfle, sewage work operator in Kötz: "Due to their high reliability and low maintenance costs we absolutely recommend AERZEN positive displacement blowers and turbo compressors." Surface of aeration basin 3. The oxygen bubbles on the surface are clearly visible. Two AERZEN positive displacement blowers have aerated the sand collector since the year 2000. The Kötz wastewater treatment plant, located a few kilometres south of Günzburg, was designed for a population equivalent of 45,000. About 20,000 inhabitants are connected at present. Due to the additional discharge of industrial wastewater, the average daily load corresponds to a population equivalent of about 35,000. The wastewater treatment plant works according to the mechanical-biological principle. In the two stage nitrification process, the wastewater, which is mechanically precleaned by a sand collector, is supplied with oxygen, to assist the action, and reproduction, of the bacteria which are required for wastewater purification. In the activated sludge basin, the activated sludge sinks to the bottom, and the cleaned clear water, with a CSB degree of purification of 96 per cent, is then fed into the adjacent River Günz. Tailor-made solutions Sewage plant operator Hans Kempfle has experience with process air generation by turbo compressors as well as by positive displacement blowers, as both systems are in operation in Kötz. In the current equipment configuration, two AERZEN positive displacement blowers, with a maximum intake volume flow of 2,370 Nm³/h and 35 kWmotor, have supplied one part of the aeration basins with oxygen since the year 2000. Since 2009, two AERZEN turbo compressors type AT 50-0,6S, equipped with air bearings with maximum intake volume flow of 2,187 Nm³/h and 37 kW motor, have been supplying the other. Furthermore, since 2000, two small positive displacement blowers have supplied oxygen for the sand collector aeration. The units were installed in separate buildings in close proximity to the aeration basins which they support. This compound system offers the operator two key advantages: for each loading situation, even where process air requirements can fluctuate considerably, it ensures an optimally adapted and safe process air supply, and makes particularly energy efficient generation possible. This is significant because energy consumption involved in process air generation at a wastewater treatment plant can amount to up to 80 per cent of total costs. New dimensions in terms of energy efficiency Due to the compound concept, the energy efficiency of the process air generation achieves excellent results, as it is possible to respond with great precision to varying requirements. Furthermore, up to now the units have been failure- free and require very little maintenance. Comparing the investment and maintenance costs, even with a long-term consideration of both systems, Kempfle assumes a balanced cost-ratio, as the lower procurement price of positive displacement blowers, plus their ongoing maintenance costs, roughly corresponds with the higher investment costs of turbo blowers. Therefore, he absolutely recommends both air-bearing AERZEN turbo blowers as well as AERZEN positive displacement blowers for generation of process air in wastewater treatment plants. The process air requirements of a sewage plant, whether operated locally or industrially, can only be achieved efficiently when different machine types are combined. This has been proved by cost-effectiveness calculations undertaken by various engineering concerns.
