Waste water digesters
Thermal insulation solutions for digesters operating at above ambient temperatures. Our high compressive tank base and wall systems will limit heat transfer and provide moisture, corrosion and mechanical resistance so that process control is assured.
Wastewater treatment is a key factor in the water cycle in most industrial countries. An essential processes of wastewater treatment is done in digesters where thickened sewage sludge is exposed to microorganisms and heat.
Digesters are usually medium or large size, vertical, cylindrical tanks made in heavy water tight concrete or sometimes in steel. Often they have a conical bottom and a conical, spherical or flat roof. They contain liquid at a moderate temperature in which biological and chemical reactions take place.
The operating temperature is often around 30°C to 40°C (86°F to 104°F). The conical bottom is normally below the ground level. Their diameters range from 5 m to 40 m (16 ft to 131 ft). Their heights range from a few meters to 30 m (98 ft), sometimes even more.
These digesters need a well performing insulation system to make sure that the operating temperature inside the digester is kept constant at all times. The biological and chemical reactions require a certain temperature to take place so it is vital that influences from outside temperatures don’t influence the inside temperatures. At times there can be a big difference between the temperature in the tank and ambient temperatures so the insulation system makes sure that the heat transfer through walls or base is limited.
FOAMGLAS® insulation is ideal for this application as it does not let any moisture through and is resistant to the chemical content should a spillage or overfill occur. The process includes the release of high energy gases (sometimes methane) which is why it is advisable to opt for an incombustible insulation material like FOAMGLAS® insulation.
The base of the digester needs to withstand great amounts of pressure, that is why a digester bases should be insulated with FOAMGLAS® High Load Bearing insulation blocks that can withstand pressure op to 240 kPa.
Typical configuration
for digesters:
For the bottom:
- One or several layers of FOAMGLAS® cellular glass adhered with PC® adhesive, the joints being filled with the same product
- A PC® finish
For the wall and the roof:
- A primer
- One or several layers of FOAMGLAS® cellular glass adhered with PC® adhesive, the joints being filled with the same product
- A coating or a jacket for the wall
- A coating or roofing membranes for the roof depending on its shape
