A process in which dirty water is stripped of its solids and made suitable for recycling into a mud system or disposal into sewer systems or other places. In closed mud systems, water containing colloidal matter can be cleaned and recycled. Efficient agglomeration of colloidal solids is achieved by pH adjustment, small additions of alum or a high-molecular-weight polymer. Agglomerated solids are then filtered or centrifuged from the fluid.