Energy-efficient heating and cooling with groundwater – with a water treatment plant from FERMANOX®
Almost 90% of a household’s energy needs are for heat, namely hot water and heating. But a large proportion of primary energy is also used in commerce and industry to heat or cool buildings and machines. The great environmental impact of CO2 emissions, but also rising prices for fossil fuels, underline the importance of using energy as efficiently as possible. Heat pumps are therefore becoming increasingly important in heating and air conditioning systems.
Groundwater is an ideal heat carrier because it is available at an almost constant temperature of around 10°C regardless of the season. Where this temperature level can be used to cool buildings and machines, direct cooling with groundwater is the most efficient method.
But groundwater is also an ideal energy carrier for heat pumps, which can provide a lot of usable energy at higher temperatures (e.g. at 35°C for underfloor heating) with little use of primary energy (electricity or gas). The groundwater is pumped from a well, cooled by 4 – 6°C in the heat pump and then returned to the same aquifer via an absorption well at a sufficient distance. A so-called water-water heat pump, for example, can provide a total of 5 kW of heating power at 35°C with a drive power of 1 kW and the energy extracted from the groundwater, which corresponds to a performance factor of 5.
This not only saves a lot of primary energy, but is also more efficient than using outside air (for air-water heat pumps) or geothermal probes (for brine-water heat pumps), because their heat transfer media, air or brine, have significantly lower temperatures than groundwater, especially during the heating period in winter.
In the 1980s, the water-water heat pump experienced a boom in Germany because the outstanding energy efficiency of using groundwater as a heat transfer medium was recognized.
Unfortunately, in practice, problems with operational safety often arose due to the poor quality of the raw water. Iron and manganese dissolved in the groundwater lead to deposits (calcification, siltation) in this system, especially in heat exchangers and injection wells. In the heat exchangers, this results in poorer heat transfer and higher flow resistance, and thus increasing energy requirements. The increasing calcification of the wells leads to a lower delivery capacity in production wells and, above all, to a lower absorption capacity and, ultimately, to the overflow of injection wells.
The underground iron and manganese removal of groundwater (process water treatment) (UEE) with FERMANOX® activates a natural treatment process in the aquifer before extraction. With little effort, iron and manganese concentrations at drinking water level can be generated there. This effectively prevents all discoloration and ochre formation. At the same time, the process is particularly sustainable because
- no filter material is required,
- no waste water or waste is produced,
- energy requirements are particularly low and
- the service life of the boreholes is increased.
The basic idea behind underground iron and manganese removal is to introduce water enriched with atmospheric oxygen into the aquifer. Even small amounts of oxygen activate an effective water treatment process there, because a reaction space with an increased redox potential is created around the well.
The substances that were dissolved in the aquifer due to reduced conditions are returned to the solid state by oxidation and are then permanently fixed again in the same aquifer at another location. This achieves efficient iron and manganese removal of the groundwater and also nitrification of ammonium, a reduction in easily oxidizable organic substances and a reduction in arsenic.
Continuous underground water treatment is based on the operation of at least two wells that work alternately as extraction or infiltration wells. The size of the reaction space around each well is determined by the amount of infiltration and the proportion of active pore volume in the aquifer. It requires an individual design for each well, which is based primarily on the raw water quality and the required treatment capacity.
The FERMANOX®-water treatment process guarantees iron, manganese and ammonium-free water – directly from the well. The ideal process for heating & cooling!
As a pioneer and market leader in compact systems for underground water treatment, FERMANOX® has the know-how to evaluate the hydrogeological and water-chemical conditions on site and the resulting design of the FERMANOX® water treatment plant.
The first FERMANOX® plant was put into operation in 1983. The iron content of the original raw water was 6.7 mg/l, which corresponds to 33.5 times the limit value according to the Drinking Water Ordinance. The plant has been running smoothly to this day, even though the borehole is now around 60 years old.
In the meantime, over 10,000 systems have been put into operation.
A crucial step in the construction or modernization of a waterworks is the process engineering planning of the water treatment. When choosing between above-ground and underground iron and manganese removal, it is worth comparing both alternatives based on efficiency and cost-effectiveness.
If you compare underground iron and manganese removal with an open gravel filter without additives (i.e. without hardening or addition of auxiliary materials, etc.), the following qualitative picture emerges:
Concept comparison FERMANOX compared to the gravel filter process
