Method for recovering and stabilizing fat and fatty substances as well as proteins and proteinous substances from process water

A method for treatment of aqueous effluents from slaughter houses or fat refining plants, said effluent containing organic materials defined as fats, fatty substances, proteins, proteinaceous substances as well as deterioration products thereof in order to recover said organic materials in the form of a stabilized sludge, consisting essentially in the following sequential steps of (a) contacting the effluents with ions selected from the group consisting of iron and aluminum in an amount sufficient to bind, by complexing the present organic material, (b) reducing the pH to below 4 by addition of a mineral acid and mixing said effluent for a time sufficient to complex said organic material, (c) adding a compound selected from the group consisting of CaO and Ca(OH).sub.2 in an amount sufficient to raise the pH to 6-9 to coprecipitate the complexed organic material, and (d) separating said complexed organic material from said effluent as a stabilized sludge by flotation.