By adding flocculant in a special treatment system or in the washing water tank of the penetration test, the test agent components are bound by the flocculant, which then collects on the bottom or on the surface. This separates the water from the test oil and water. The water can be removed or separated using simple filters and then fed into the public sewage system or fed into the cycle. The flocculant and penetrant sludge is discarded. Due to the high running costs and the lack of suitability for a continuous process flow, the use of flocculants is usually recommended for small to medium-sized systems with different loads.