Abstract: A generally horizontal container, interposed in a drilling mud conductor, forms an enlarged area passageway for the drilling mud. The container transversely journals a plurality of spaced rotating plate-like discs forming positive electrodes between negative electrodes formed by a plurality of spaced-apart interconnected panels with a peripheral portion of each disc immersed in the drilling mud. Solids in suspension are attracted by and deposited as a layer or film on opposing surfaces of the respective discs. A stationary scraper blade element, adjacent the discs, removes the deposited solids. Pressure operated plungers, disposed on opposing sides of the respective disc, periodically move the collected solids toward a discharge end portion of the scraper blade element for removal.