TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Process: The process comprises changing the direction of flow in the filtration operation in periodical spacing and taking a backwashing, promoting the filtrate against the filtration direction by the membrane element for a defined period of time. The reactor consists of several separate chambers, and the chemical cleaning takes place only in a chamber or only in a partial number of chambers, while the remaining chambers further continue to run in the filtration operation. The cleaning takes place in the cross-flow procedure, where the cleaning solution is pumped from a cleaning tank to filtration modules in the chambers and it occurs in a filtrate exit, and flows in the axial direction through the membrane elements in the form of hollow fiber membranes, discharges at another filtrate exit and flows back into the cleaning tank. The cleaning solution passes through the pressure inside the hollow fiber membrane cleaning solution from the inside out through the pores of the membrane elements. The filtration module in the chamber stands a time long in cleaning solution after completion of the flow of the cleaning solution through the membrane element of the filtration module in the chamber, which dissolves in the membrane outer wall remaining coatings. The hollow fiber membrane is used as membrane element and the medium to be filtered is vacuumed from outside to inside through the hollow fiber membranes in the filtration operation by a vacuuming pump. The process is conducted over a blower air in the medium to be filtered, containing container, and creates a turbulence behavior in the medium. In a first step, a press screw separator (13) is used, which separates the crude solid material contained in the digestate. The pressing obtained filtrate is sieved in at least one of step following the pressing step, preferably by at least one vibrating screen (14). The filtrate of the sieve step is subjected to a divided procedure with submerged low pressure membranes. EXAMPLE - No suitable example given.