Real projective structures on Riemann surfaces

A method of treating an aqueous biological slurry comprising the steps of feeding the slurry through an evaporator plant where it is subjected to heat treatment and where a part of its water content is removed by evaporation, filtering the slurry which has passed through the evaporation plant and recycling the aqueous filtrate for further treatment with the slurry in the evaporator plant and an installation for performing same.