Pulp and paper industry in Europe is impelled to cut down the amount of solid waste used nowadays in land filling. To avoid land filling sludges are usually burned, but because of their low dry solids contents, sludges need to be dewatered before burning. Dewaterisation takes place usually by mechanical means.
http://www.actapress.com/Abstract.aspx?paperId=26644

"Deshidratarea namolului biologic si a namolului prehidratat mecanic, prin intermediul presei elicoidale".

"Sludge can be divided into primary sludge from mechanical treatment and bio-sludge from biological treatment."

Handbook of paper and board
De Herbert Holik pg.430