Possibility of obtaining wastewater heat from a sewage treatment plant by the means of a heat pump – a case study

The research was carried out in the mechanical and biological wastewater treatment plant of the city of Prószków in Poland. There is a demand for heat for hot tap water, heating and technological purposes. There is no gas network in the town, therefore it is necessary either to install solid fuel boiler or electrical equipment to generate heat. Instead, a system based on a heat pump (HP) was proposed, which is a pro-ecological and pro-economical alternative. The research involved the measurements necessary to develop energy balances and collection of local climate data. As a result, possible heat from sewage was determined for an exemplary heating season. For the assumed calculation conditions, the maximum amount of heat is 346 kW of which 98% will be used for heating up the sequential biological reactor (SBR) and 2% will be used for social needs. The current SBR temperature in the winter period is 8°C, which significantly limits the process of biological treatment. The optimum temperature range of sewage in SBR is 15–25°C. Based on the collected data, the concept of a HP-based system for generating heat was developed to maintain the optimum temperature. Sewage is a very effective heat source for the HP. This ensures the highest coefficient of performance (COP)