TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Process: The suspended sediment is recycled directly into the biogas fermenter. The biogas fermentation and subsequent stages up to and including UF are carried out anerobically. The material removed from the fermenter (specifically in at least two different processes) is subjected to at least two successive mechanical separation procedures, one (preferably the second) of which involves UF (7) with recycling of the suspended sediment. The material from the fermenter is removed to a fermentation residue receiver (3), with a separate solid-liquid separator (4). A liquid component from the solid-liquid separator (especially the turbid outflow) is treated with flocculant and recycled to the separator; and the solids from the separator are recycled to the fermenter (if fermentable) or pasteurized and converted into a spreadable organic fertilizer using heat from the process. Material removed from the fermenter via an outlet is supplied to a second solid-liquid separator (5) and the solid components are recycled to the fermenter. The liquid components from the fermenter are combined and supplied (preferably through a magnetic field) to the UF stage (7), and the filtrate from the UF is subjected to RO, preferably in two stages (10, 11). At least part of the RO filtrate (preferably permeate from the first stage (10)) is recycled to the pre-storage pit (1) as mixing water. The receiver (8) for filtrate for RO is acidified, preferably with sulfuric acid from a compost drying process operating in parallel. The retentate from the first RO is tested for free ammonia, which is bound by supplying a stoichiometric amount of acid, preferably with beating, especially with simultaneous supply of oxygen and fluidization. The retentate from the second RO is is recycled to the receiver (8) for filtrate for RO. The RO retentate is converted into a spreadable, phosphate-depleted ammonium sulfate-potassium chloride fertilizer using heat from the process. The RO permeate is beaten with ozone or chlorine dioxide. ACTIVITY - Fertilizer.    MECHANISM OF ACTION - None given in the source material.