Possibilities of using wastewater in sewage treatment plants as a source of heat
autor:
Władysław Szaflik
ORCID ID:
0000-0003-3767-8766
Numer miesięcznika:
05/2022 Instal s. 10-14
DOI:
DOI 10.36119/15.2022.5.2
Preventing climate change is a priority for the European Union. In order to reduce CO2 emissions into the
atmosphere and thus the negative impact of human activity on the environment, the European Parliament and the
Council of the European Union have developed and enacted a number of directives. Improving the energy efficiency
of systems used by people is a priority task included in the European Union policy.
Energy obtained from the combustion of biogas and sewage sludge is widely used at wastewater treatment plants,
while the heat recovered from wastewater is used only to a small extent.
The article presents methods of heat recovery from wastewater and possibility of its application at wastewater
treatment plants. The heat contained in the wastewater is discharged into the sewage system and further into the
wastewater treatment plant. In most wastewater treatment plants in Poland, the heat is not utilized and flows with the
treated wastewater to the reception tank. The lack of utilization of this heat is due to the low temperature of the
wastewater, which is higher than the temperature of cold water supplied to buildings by only a few to several
degrees Celsius. This limits the direct use of the heat contained in them with heat exchangers. In wastewater
treatment plants, the higher temperature heat is used for heating, hot water preparation and technological needs.
A higher temperature of the heated medium than in heat exchangers may be obtained with heat pumps, where
wastewater can be used as lower heat source. Unfortunately, this temperature cannot be too high as the efficiency of
heat pumps (COP) decreases with the increase of the temperature in the condenser. The basis of any analysis of the
possibility of using heat from wastewater is the determination of its temperature. The analysis is based on the
example of the Zdroje Wastewater Treatment Plant in Szczecin, for which the results of wastewater temperature
measurements are presented for individual days in 2020. Analysis was also performed for water taken at the
Miedwie intake, which feeds the wastewater treatment plant’s inflow areas, and for the average daily outdoor air
temperature. The average daily efficiency of heat extraction with heat pumps from sewage at the plant and from
outdoor air was determined for selected months. The efficiency of heat extraction depends on the temperature of the
lower and upper heat source. The paper presents the results of performance calculations when the lower heat
sources are wastewater and outside air. The efficiency of heat extraction from wastewater is higher than that of heat
extraction from air. The relative increase in pump efficiency was also determined when wastewater is the lower heat
source instead of the outside air.
Słowa kluczowe:
Informacje o autorach:
prof. dr hab. inż. Władysław Szaflik https://orcid.org/0000-0003-3767-8766 – Zachodniopomorski Uniwersytet Technologiczny
w Szczecinie, Wydział Budownictwa i Architektury, Szczecin; Corresponding adress: Wladyslaw.Szaflik@zut.edu.pl