The issue of this article is one stage washing of reaction blend after enzyme hydrolysis under which we are able to recycle almost all contained chromium in solid leather waste. During hydrolysis we gain protein hydrolysate as a filtrate that is appropriate substance for use. On the basis of equation for streaming of liquids through layer of substance we determined optimal pressure differential for filtering and washing of reaction mix and we applied mathematical description valid for filtering and one stage washing and on the basis of this models we able to optimize washing process that is add to filtering and which aim is to reduce content of protein hydrolysate in filter cake.