Evaluation of diamond grinding slurry solids separation strategies and reuse as a soil amendment

Diamond grinding slurry (DGS), an alkaline by-product of highway concrete resurfacing with diamond grinding machinery that is generated in large volumes, poses challenges for management and disposal. In this study, we evaluated two alternative DGS management strategies: (1) enhancing solids separation using polyacrylamide (PAM) flocculants and (2) potential use of separated DGS solids as liming agents during vegetation establishment. DGS from three road grinding operations in North Carolina were paired with compatible PAM flocculants to find effective treatment doses for improving settling efficiency. Following DGS separation, clay loam and sandy loam soils were amended with DGS solids (0-260 Mg ha^-1) to determine the effect on soil properties (pH and electrical conductivity) and grass seed germination. Results showed that PAM-assisted settling enhanced DGS separation and improved water quality for reuse, but the efficacy and optimal doses were contingent on DGS-PAM compatibility. The alkaline solids increased soil pH and electrical conductivity when used as a soil amendment, but the clay loam and sandy loam soils showed sufficient capacity to buffer amendments up to 45 Mg ha^-1 before approaching alkaline conditions. Moderate rates of DGS solids amendments (up to 45 Mg ha^-1) did not adversely affect vegetation germination. These findings highlight the potential for PAM flocculants to be used for enhanced separation of DGS in sediment basins, and separated DGS solids may have potential to be used instead of lime during roadside vegetation establishment.