污水处理产生剩余电力

自2010年以来，玛尔丽斯堡污水处理厂已将其重点从最大限度地减少能源消耗转向最大限度地实现净能源剩余。如今，该厂同时能够发电和生产热能，为丹麦第二大城市奥胡斯的区域供暖系统供电，相应减少了35%碳足迹。

水和废水处理设施通常是一个城市最大的用电大户。水和废水处理工艺通常占城市用电量的25–40%。高消耗与能源密集型工艺有关，但也与其每年24/7和365天的连续运行周期有关。

多年来，人们一直致力于开发新的工艺和控制策略，以减少每公升处理水的能耗。与此同时，对污水处理质量的要求也在日益增长，例如在去除杂质的同时也增加了能耗。

优化能源中和

水和污水处理过程的特点是全年侯24小时不间断高负荷运转。因此，对变频器的需求量也在逐步递增，因为水处理厂需要利用变频器加强对风机、泵和其他设备应用的控制，以适应不断变化的需求。

自2010年以来，奥胡斯水务公司一直与水环境顾问密切合作，以改善玛尔丽斯堡污水处理厂的能源中和。

Key steps in the strategy

• Optimization of the nitrogen removal process using online sensor control. The frequency converter adapts the level of aeration precisely to the need. This control system reduces energy consumption and increases the amount of carbon left in the system.
• Blower technology upgrade to a high-speed turbo blower. The upgrade achieves further reduction of energy consumption in the aeration process.
• Aerobic sludge age control as a function of temperature and load on the plant. Here frequency converter control of the return sludge pumps is the key to achieving energy reduction and increased retained carbon in the system.
• Upgrade of combined heat and power (CHP) process for energy production, with 90 % energy efficiency.

These changes together with improvements including the effective co-production of electricity and heat based on methane gas extracted from the aerobic sludge digestion process have created the impressive results of:

• 130 % electricity production (30 % excess electricity)
• Excess heat production of about 2.5 GWh/year

VLT® in every corner

Frequency converters are installed on almost all rotating equipment at Marselisborg WWTP: blowers, pumps, mixers and dewatering pumps. The frequency converters allow the plant to adapt to load variations, with maximum flexibility. Over 100 motors are controlled by VLT® frequency converters at Marselisborg.

Energy generation vision

The vision for Aarhus City is to extend energy generation even further, to achieve surplus production of energy from its wastewater treatment plants so high, that it can also meet the energy requirement of the city’s potable water supply. This will transform the single largest electricity consumer for the authority into an energy-neutral party.

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