The pump station's function is to lift the wastewater several meters in pressure in order to drive the flow further. The stations are built both above ground and below ground. The stations are dimensioned for current flow requirements. Capacity requirements vary from small systems for individual houses to very large facilities.
Many pump stations are today heated to between 15 ° - 20 ° C, all year with direct-acting electricity. As the number of pumping stations is large, this means that there are large energy gains to be obtained by safely lowering the temperature in the pumping stations. However, when the heat is lowered, it increases relative humidity unless the water is removed from the air. This can cause problems with, among other things, corrosion, mould and odour. In order to lower the temperature in the pumping stations, the relative humidity (RH) needs to be checked. Airwatergreen dehumidifiers are built with a technology that allows them to dehumidify the air energy efficiently regardless of the temperature. This makes the technology suitable for low temperatures. Lowering the temperature in 100 pump stations in a municipality enables an energy saving of about 260 MWh per year. This corresponds to an emission reduction of carbon dioxide of about 23.4 tones per year!
Corrosion is an electrochemical reaction to metals exposed to corrosive gases and / or high relative humidity (RH). This can lead to high maintenance costs and reduced life of important components. Sulfur hydrogen emitted from the grounds is an example of a common corrosive gas in pump stations.
Corrosion in pumping stations is typically due to:
- High relative humidity
- Sulfur hydrogen from sewage pit
- Other corrosive gases from sewage pit
Odour comes from the sewgae pit and penetrates the superstructure. This effects the working environment and can lead to nearby residents complaining.
Examples of odour-emitting gases are:
- Hydrogen sulphide
- Sulfur dioxide
The amount of hydrogen sulphide present in the air in a pumping station can effect the health of those working with pump stations. The health effects are linked to the concentration of hydrogen sulphide in the air. To work for 8 hours, the Swedish Work Environment Authority has guidelines on 5 ppm hydrogen sulphide in the air.
Health effects of hydrogen sulphide:
- Sore throat
- Physical collapse
- Difficulty in breathing
Correct humidity level
What is needed is a controlled moisture level of below 60% relative humidity (RH) to avoid corrosion and mould, but also to reduce bacterial growth. This requires a controlled relative moisture level at the prevailing temperature. See the Mollier diagram where the condensation (saturation) curve is given as 100% RH at different temperatures.
The following calculation is based on a dissertation from Uppsala University. Here, the energy consumption was measured in a small pump station in two cases.
The pump station has a floor area of about 5.8 m2.
- In the first case, a heating element was allowed to maintain 18 ° C in the pump station and the relative humidity varied freely.
- In the second case, a condensing dehumidifier, FLEX Integrate, was allowed to maintain an RH of 50% and the temperature was allowed to vary freely above 5 ° C.
The figure shows the energy consumption values for a pump housing i with temperature data during 2015. The blue line shows the values for the pump housing with an element that maintains the temperature of 18 C. The red line shows the energy consumption values for a condensing dehumidifier. The result shows that with a condensing dehumidifier, the energy consumption for a year is 513.8 kWh and with an element 3101.57 kWh. The energy consumption if a condensing dehumidifier is used instead of elements becomes 83.0% lower.
The figure below shows the energy consumption in a pumping station where the relative moisture level is controlled for a full year. The blue line shows the energy requirement when heating with an element and the red line shows the energy requirement when using a condensing dehumidifier to control the climate and keep the relative humidity at a stable level. As the figure shows, our dehumidifier needs a fraction of what an electrical element requires.
The red line shows the lower energy consumption when a dehumidifier maintains the same climate
CARBON FILTER AGAINST SULFUR HYDROGEN
A carbon filter can adsorb gases that cause corrosion and odour problems such as hydrogen sulfide, ammonia and mercaptans. However, activated carbon also adsorbs the water vapor present in the air if the relative humidity exceeds 70%. The water vapor in the air causes the pores in the carbon to become clogged and the activated carbon loses its ability to capture the harmful gases. This means that the carbon has to be changed irregularly, leading to high maintenance costs and unsafe operation.
Easy installation as we do not need to take any holes in the walls or ventilation pipes. Our dehumidification technology is as energy efficient in cold as in warm spaces. The dehumidifier can be mounted on a wall bracket so that the floor is kept free in the station building. Ordinary 1-phase 230V plug is enough as a power supply for a FLEX.
The water is easily drained away with a hose or other draining.
ESTABLISHING ODOUR-FREE CLIMATE
To handle the challenges associated with moisture in the pump stations, the following set up is used. A carbon filter sucks air directly from the sewage pit. This creates a negative pressure in the sewage pit. Dry air from the superstructure penetrates the sewage pit and is mixed with the harmful gases. The mixed air is discharged via the carbon filter. In the superstructure, a wall-mounted condensing dehumidifier maintains the right climate. The dehumidifier regulates the relative humidity but can also ensure that frost and ice formation are avoided by a built-in frost guard.
LIFE CYCLE CALCULATION (LCC)
Heating using a typical electric element consumes just over 3200 kWh per year. An Airwatergreen dehumidifier consumes an average of 500 kWh in a normal sized pumping station. This gives a huge saving in energy and also ensures that the cost of renovation due to rust and mould is eliminated!
Our dehumidifier is called FLEX and has a capacity of 5 liters water / day which is more than good in a normal sized pumping station.
The pump station package includes:
- Dehumidifier FLEX Smart or a FLEX Integrate
- Wall mount
- Service agreement
In our solution ODOUR FREE CLIMATE which removes hydrogen sulphide also includes:
Airwatergreen has today a large number of installations in pump stations. In most installations, the dehumidifier works independently to the desired relative humidity level (RH) and in other cases it is connected to an existing monitoring system. The products are built to withstand the harsh environment that applies with few moving parts and well thought-out material choices and an IP63 rating. The air that passes through the dehumidifiers is not only dehumidified but also filtered so that dust and insects are trapped. It creates the conditions for a good working environment!
Do not hesitate to contact us for a climate study to define the moisture levels and to design a suitable solution for your business!