污水处理厂的能源与资源回收方式及其碳排放核算:以芬兰Kakolanmäki污水处理厂为例

Analysis of energy recovery and carbon neutrality for the Kakolanmäki WWTP in Finland

探索切实可行的资源与能源回收方案、实现污水处理的碳中和运行,是污水处理领域的重要发展方向。北欧国家一些污水处理厂已凭借污泥厌氧消化产甲烷(CH4)并热电联产(CHP)、以及余温热能利用等技术实现了能源的回收利用。以芬兰Kakolanmäki污水处理厂为例,结合该厂的污水处理工艺流程分析其能源回收方式,并运用碳足迹模型核算了其污水处理工艺与能源回收环节的碳减排量,以确定其整个运行中的碳足迹。分析结果表明,该厂污水处理工艺不仅可以满足严格的出水水质排放标准,还可通过回收出水余温热能等方式实现能源中和与碳中和运行,并向社会供热。其中,该厂的总回收能量(电能+热能)大于其自身能耗的6.4倍。出水余温热能回收潜力最大,约占全部可回收能量的90%;厌氧消化并热电联产所回收的化学能不足10%。回收能源不仅使该厂实现碳中和(碳中和率333%)运行,而且剩余碳汇(以CO_(2)当量计)达24931 t·a^(−1)。该厂的实践表明,污水处理实现碳中和运行的关键在于重视出水中大量的余温热能回收。芬兰Kakolanmäki污水处理厂的案例可为国内污水处理厂探索高效能源利用、并实现碳中和运行提供参考。

Sustainability is an orientation of future wastewater treatment,in which carbon-neutral operation plays a key role.Energy recovery has been achieved via combined heat and power(CHP)technology based on CH4 production by anaerobic digestion,and thermal energy recovery at some wastewater treatment plants(WWTPs)in Northern Europe.The practical experience from the WWTP at Kakolanmäki in Finland demonstrates that the plant can not only meet the strict effluent discharge standards but also achieve the goal of both energy and carbon neutrality via recovering thermal energy from the effluent and even become an energy factory by supplying heat and electricity to the society,up to 6.4 times the energy consumption of the plant.Among all the recovered energy including anaerobic digestion of excess sludge and solar energy,the thermal energy from the effluent has the maximal potential,up to almost 90%of the totally recovered energy,whereas anaerobic digestion plus combined heat and power(CHP)takes a share less than 10%.The recovered energy can not only make the plant achieve carbon-neutral(333%in the carbon-neutral efficiency)operation but also can produce a huge carbon sink,up to 24931 t CO_(2)-eq·a^(−1).The practical operation of the plant reveals that realizing carbon-neutral operation of WWTPs is achievable,and the key lies in recovering the thermal energy from the effluent.The case study of the Kakolanmäki WWTP provides reference for exploring efficient energy recovery and realizing carbon neutral operation at WWTPs in China.