In this research, ground walnut shells were used in order to improve the sewage sludge treatment The influence of walnut shells on capillary suction time (CST): the sludge moisture content (MC), bound water (BW), the specific resistance to filtration (SRF) as well as the total bacteria number was investigated. The results have shown that the addition of ground walnut shells into sewage sludge affected the reduction of total bacteria count and the improvement of sewage sludge dewaterability. The addition of ground walnut shells in the amount of approximately 200% of sewage sludge dry mass (DS) decreased the MC by 66%, CST by 68% and SRF by 64%. The total bacteria number was reduced by approximately 88% after physical conditioning with the use of walnut shells in a dosage of 200% DS. It was proved that walnut shells might be considered as a material assisting the sewage sludge treatment. (C) 2019 Elsevier B.V. All rights reserved.