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• Opportunities for wastewater heat recovery in Hungary and its role in the circular economy

  Zoltán Gabnai

  Kornél Németh

  Erzsébet Péter

  Ardit Sertolli

  Albiona Pestisha

  Nóra Mezőfi

  Attila Bai

  Views:

  416

  Most of the energy content of wastewater can be found in wastewater heat, however, its recovery is limited. In this article, the current situation, future opportunities of wastewater heat recovery are presented based on secondary data collection, mentioning the constraints and main influencing factors of sustainable implementation of heat recovery systems in Hungary. Besides, the already existing systems are described. As regards the capacities of treatment plants, 103 of the 574 domestic plants have a capacity of over 20,000 Population Equivalent (PE), of which 25 plants have a capacity of over 100,000 PE. According to our calculations, in big cities/capitals (20.000 – 100.000, and over 100.000 inhabitants), it may be possible to recover wastewater heat sustainably in several places. In small towns (5.000 – 20.000 inhabitants), wastewater heat recovery can be technologically and economically sustainable only in the presence of agricultural or industrial plants with high and continuous wastewater feed into the pipeline system. Taking into account the temperature conditions at each place of use and their estimated fluctuations, it can be said that proper, careful planning, sizing and implementation have a crucial effect on the efficiency of microbiological activity in the treatment plants. In bigger cities, of course, the effect of the temperature drop of one main collector may be minimal, however, in smaller and medium-sized settlements, excessive heat extraction may result in complete inhibition or cessation of nitrification. In Hungarian case studies, the maximum acceptable temperature drop is approx. 2-3 °C. It can be stated that energy recovery from wastewater may be very promising considering the size and temperature limitations. Therefore, the rational recovery of wastewater heat can be an important part of the implementation of circular economy and sustainable energy utilization in wastewater management, resulting in significant energy savings and pollutant reduction.

  JEL CODE: Q25

• Energy alternatives in large-scale wastewater treatment

  141-146

  Zoltán Gabnai

  Views:

  216

  In my article, after describing the characteristics of recent wastewater treatment activity, I introduce different traditional and innovative energetic opportunities of the compulsory waste management activities at large-scale operational level, covering national and international examples. Furthermore, the wastewater-based biomethane production and the certain plant’s energy self-sufficiency are highlighted topics as well. In the former case, it is possible to utilize the wastewater-based biomethane as fuel (and even to operate own vehicle fleet), while the second one gives the opportunity for the internal usage of produced electricity and waste heat, which can also result in significant cost-savings. As an additional option, algae-based wastewater post treatment is presented, based on the conditions of a Hungarian wastewater treatment plant, which biogas production efficiency and thus energy self-sufficiency has developed favourably due to the technological improvements. These plants may have a twofold role in the future: they are responsible for the compulsory waste management activity and on the other hand they can serve as excellent raw material mines.

  JEL Code: Q25