Edition 04/16

Energy efficiency is becoming more and more important in the German wastewater treatment sector. From a technical point of view, the focus is on CO2 minimisation and digitalisation (Water 4.0), as well as on the A 216 rulebook of the German Association for Water and Waste Water Technology (DWA). But the requirement for optimal use of government funding is also gaining in importance. As a result of these developments, there are opportunities as well as new challenges. Accordingly, the wastewater forum offered operators, engineering offices, system manufacturers and blower suppliers a platform to combine theory with practice. 

Wastewater treatment plant as energy producer

The first day of the event was dedicated to the press and addressed the following question - which new technological approaches and concepts are currently being tested around Europe which could ultimately result in a wastewater treatment plant changing from being a municipality’s biggest energy consumer into an energy producer?
Wolf-Uwe Schneider, Plant Manager of municipal wastewater drainage operation Rheda-Wiedenbrück, presented current operational activities at the Rheda-Wiedenbrück wastewater treatment plant. Using the example of his current “POWERSTEP” project, promoted by the EU (www.powerstep.eu), Christian Loderer presented the wastewater treatment plant of the future. The useable chemical energy in the activated sludge is discharged right at the beginning of the wastewater purification process, in order to produce a higher biogas return and ultimately more heat and more energy. Technologies such as carbon extraction, mainstream deammonification, ammonium stripping, and also power-2-gas and heat-2-power technologies, are being tested at six European wastewater treatment plants. 

Energy-efficient aeration

The second day of the event involved around 40 industry practitioners. First of all, Schneider gave a brief historical overview of the individual construction measures at the Rheda-Wiedenbrück Wastewater treatment plant. The focus of the actual reconstruction measures was on optimisation of the biggest energy consumer of the wastewater treatment plant, i.e. the biology. A new energy-efficient aeration system, including a newly designed compressed-air station made by AERZEN, was installed, and this resulted in tremendous savings in operating costs.
During his presentation, Markus Haver­kamp, who is responsible for projects at the consulting and engineering company aqua consult GmbH, pointed out how important it is to observe and implement correctly the DWA-A 268 rulebook and stressed the advantages that this brings. Using the example of the Rheda-Wiedenbrück project, forum participants could see the implementation of the new design and automation of the single-stage aeration basin by applying the DWA-rulebook in practice.
Afterwards, Rüdiger Vrabac, of UD Umwelt-Dienste, gave a lecture on the topic of aeration. He not only presented the new membrane strip ventilation technology, but also demonstrated how optimal oxygen entry into the aeration basin can be guaranteed with a skilled allocation of basins by means of diffusers.
Besides energy-efficient aerators, an optimised aeration system needs energy-efficient blowers. With positive displacement blowers, DELTA HYBRID rotary lobe compressors and turbo machines, AERZEN offers all three machine technologies (Performance³) from a single source. Markus Leidinger, AERZEN wastewater manager in the EMEA division, presented the successful upgrade of the blower station to the new Performance³ concept with AER­smart: a turbo for covering the base load, a Delta Hybrid, on the one hand for exclusively covering the weak load and in combination with the Turbo for covering the air consumption during full load operation. In this way, it is possible to dimension the required oxygen volume for any load by means of the most efficient machine. Thanks to the comprehensive data provided by the AERsmart control system, energy analyses of the machines currently running can be prepared and displayed. These give systematically detailed information about the energy consumption of the blowers, and provide a comparison between the current actual value and the plant-specific ideal value, so that, if necessary, suitable energy optimisation measures can be taken. As a result, the recommendations of the DWA A 216 rulebook which refer to meaningful performance values of a compressor station, are available at the push of a button.
The principle behind AERsmart is that it optimally distributes the required air volume at all loads to the individual degree of efficiency of the installed machine combination, and can be connected to master control systems. As a result, the installed machinery is able to operate at an efficiency level which is very close to the highest level theoretically possible. Another major advantage: blowers made by other manufacturers can also be integrated into the control system. The engineering office, the system manufacturer and the operator receive a consistent concept from a single source for the visualisation, communication and optimisation of process-relevant machine data, thus enabling them to manage the best possible energy concept.
At the Rheda-Wiedenbrück wastewater treatment plant they have had enormous success: the new machine technology Performance³ with AERsmart has resulted in savings of approximately €40,000 per annum being made. The costs of the upgrade will be fully amortised after just four years.

Financing options

Finally, Andreas Koschorrek, of e.qua, presented information about government funding programmes in respect of CO2-minimisation which elicited great interest among the specialist audience. Start-up funding costs of up to 50 per cent, and development funding costs of up to 90 per cent, depending on the individual federal state involved, can be claimed. Therefore, AERZEN has developed, together with e.qua, network energy recovery and resource management, a customer-specific, and very streamlined, way to apply for corresponding funding when using energy-efficient compressors and seeking possible heat recovery.