Today a lot of the sludge from municipal wastewater treatment plants is dewatered to a dry solid content of 20-30 %. This results in high costs and other problems.
Watewater from housholds and indistries is cleaned and purified in a wastewater treatment plant.
From this process a sludge with high water content is obtianed. Around 0,5-2 % dry solid content.
The sludge is dewatered and dried with the Freeze Dry Unit to a dry slid content of 95 %.
The sludge is mechanically dewatered with a screw press or centrifuge to a dry solid content of 20-30 %.
The dried sludge is transported to the area of disposal. Few transports are needed as the dry sludge have a small volume.
The sludge is transported to the area of dsiposal.
The dry sludge has a variety of different ways to dospse of the sludge. It can be incinerated, pyrolized, used as fertilizer and more.
Ways to dispose of the sludge are limited. For example it can be used as fertilizer i agriculture, as a bulding material for a deposit cover or be composted.
The high water content results in unnecessary transports between the plant and the disposal, as it is mostly water that is transported. The options for disposals are also limited as some alternatives, like incineration, do not go well with wet or damp sludge. Future laws and regulations can also prohibit sludge to be spread on farmlands, as polymer accumulates in the ground and little is known what effects this gives in the future. In some cases, the incoming water is so polluted that the use of the sludge is very limited. As the sludge from the Freeze Dry Unit is very dry, pyrolysis can be used to eliminate pollutions and obtain a bio coal.