The scope of the project
The municipality of Herning wanted to increase the capacity of Herning Wasterwater Treatment Plant by adding a new digester for mesophilic after digestion to handle the sludge from the existing thermophilic digester.
To determine the base of the design for the new mesophilic digester, historic data including load data, sludge volumes before and after digestion, gas production, and the amount of precipitation chemcicals was analyzed to ensure the best solution for this specific plant.
The solution
The solution includes a new mesophilic digester for after digestion of sludge from the exiting thermofilic digester. The digester is constructed with a stirring and heating exchanger installation for bith heating and cooling of the sludge. Furthermore a new building with a liquefier and flow measurement on the gas from both the thermofilic and mesopholic digesters is build.
Finally a new gas tank of 250 m3 is constructed as a gas storage for smooth running of the gas motor, kettle and gas flare. The key benefits of the new solution are found in the combination of a thermofilic main process and a mesophilic after digestion, which creates an extra-large gas output, since the amount of organic material is always much lower in the mesophilic process.