Pump Stations

DRY PUMP STATIONS

The purpose of the pump station 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 to address specified flow requirements. Capacity requirements vary from small systems for individual houses to very large facilities.

CHALLENGES

Pump stations are sometimes warmed up to between 15° – 20°C, all year around using direct-acting electricity to maintain a healthy relative humidity level. Using heating to maintain a good relative humidity level is 5 times more expensive than using a dehumidifier.

There are many pump stations in use meaning a lot of energy is used to protect the stations from too high levels of humidity. However, when the temperature is lowered, the relative humidity level will go up unless some water is removed from the air. If the relative humidity level go up – there will be a risk for corrosion and mold.

FLEX i en pumpstation

Airwatergreen dehumidifiers are built with a technology that allows them to dehumidify the air energy efficiently regardless of the temperature.  Lowering the temperature in 100 pump stations in a municipality enables an energy saving of about 260 MWh per year (depending on the cost for the electricity). This correspond to an emission reduction of carbon dioxide of about 23.4 tones per year!

INSTALLATION

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 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! The water is easily drained away with a hose or other draining.

 

CORROSION

Corrosion is an electrochemical reaction to metals exposed to corrosive gases and / or high relative humidity (RH). This can lead to increased maintenance cost 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

Correct humidity level

What is needed is a controlled moisture level of below 60% relative humidity (RH). This will prevent corrosion and mold, 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.

ENERGY SAVING

The following calculation is based on a study made at the 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 heater was used to maintain 18°C in the pump station and the relative humidity varied freely.
  • In the second case, a FLEX dehumidifier, was used to maintain an RH of 50% and the temperature was allowed to vary freely above 5°C.

I figuren nedan visas värden på energiförbrukningen för ett pumphus i med temperaturdata under 2015. Den blå linjen visar värdena för pumphuset med ett element som håller temperaturen på 18°C. Den röda linjen visar värdena för energiförbrukningen för en kondenserande avfuktare. Resultatet visar att med en kondenserande avfuktare blir energiförbrukningen för ett år 513.8 kWh och med ett element 3101.57 kWh. Energiförbrukningen när en kondenserande avfuktare användas istället för element blir 83.0% lägre!

The figure below show the energy consumption over time ​​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 18C. 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, is 83% lower.

The red line shows the lower energy consumption when a dehumidifier maintains the same climate

 

ODOR INSIDE AND AROUND PUMP STATIONS

Odor come from the sewage pit and penetrates into the superstructure and out of the building. This effects the working environment and can lead to nearby residents complaining about bad odor.

Examples of odour-emitting gases are:

  • Hydrogen sulphide
  • Ammonia
  • Mercaptans
  • Sulfur dioxide
  • Methane

 

WORKING ENVIRONMENT

The amount of hydrogen sulphide present in the air in a pump station can effect the health of those working there. 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:

  • Dizziness
  • Cough
  • Sore throat
  • Nausea
  • Headache
  • Physical collapse
  • Seizures
  • Difficulty in breathing

OUR SOLUTION TO REMOVE HYDROGEN SULPHINE

A carbon filter called Blackbox 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.

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.

 

PRODUCT CHOICE

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:

  • Blackbox

REFERENCES

Airwatergreen has today a large number of installations in pump stations. More than 200 installlations at more than 70 water companies in Europe. 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. Please refer to our User stories for a few case descriptions and many pictures.

Do not hesitate to contact us for a climate study to define the moisture levels and to design a suitable solution for your business!