Advisory Guideline DWA-M 114E Energy from Wastewater – Thermal and Potential Energy

Wastewater contains a large amount of heat which, using modern heat pump technology, can be used to heat buildings. The potential of this renewable energy source is huge. Using wastewater heat we could – in terms of availability – heat 10 % of all the buildings in Germany. Due to rising energy prices on the one hand, and the technological progress in the fi eld of heat pumps and heat exchangers on the other, the use of wastewater heat is becoming increasingly attractive from an economic point of view. Given the right parameters, wastewater heat recovery plants are already economically competitive compared to fossil fuel heating systems. With the right planning and execution, they do not present any disadvantages either for the drainage system or the wastewater treatment. Wastewater heat recovery is used for heating buildings and for water heating. Larger individual buildings or district heating networks with several buildings are especially suited. Wastewater heat recovery is also ideal for heating swimming pools, for drying sewage sludge and – given the right temperature conditions - for commercial applications. The lower the temperature level of the heat recipients is, the more effi ciently the heat pump is able to operate. The heat pumps can also be used simultaneously for cooling purposes, e.g. for commercial refrigeration, or in summer for cooling rooms. Here, the heat pump acts in “reverse” as a refrigerating machine. In all cases however, a suffi cient amount of heat from wastewater needs to be available in the locality. The heat can be taken from the wastewater in the building itself, the sewer or the sewage treatment plant. The first option is not examined here because it concerns building-internal heat recovery. The use of the sewer or the sewage treatment plant, on the other hand, concerns sewage disposal and therefore falls within the scope of this Advisory Leafl et. The Advisory Leafl et DWA-M 114 “Energy from Wastewater – Thermal and Potential Energy” describes the aspects of energy production from wastewater plants relating to planning, construction and maintenance. The main focus is put on heat recovery from drains and sewers. This can also be adapted and applied to potential energy. Another focus is on the effects of energy production plants on the sewage treatment plant downstream from the drainage system. The experience already gained from the guidelines in Switzerland and Germany has been incorporated in the Advisory Leafl et. One section of the Advisory Leafl et deals with the economic viability of such plants.