Onsite Diamond Grinding Slurry Wastewater Disposal

Marketing Paragraph: Statement of Purpose: The North Carolina DOT has over 130 planned projects in the next decade geared toward pavement rehabilitation, widening existing roads, and creation of new concrete highways. Each of these may require diamond grinding, a construction method used to restore and prolong the lifespan of concrete pavement. Unfortunately, this process produces large volumes of wastewater that are difficult to manage. The most common disposal method in the state is currently the transportation of the waste to an offsite press-plate system where the solids and liquids are separated by machine. Conversely, sediment basins are being used to separate diamond grinding solids from the wastewater and, with permitting, allow for land application to improve soil and aid in roadside vegetation establishment, thus improving waste disposal efficiency. The solid fraction proved to be a safe means of reducing soil acidity, but further research is needed to determine ideal application rates of the liquid fraction. Results will be used to reevaluate current permitting requirements or propose modifications to the permits.

Full Abstract: Complete Proposal for Your Session: Diamond grinding slurry (DGS) is a solid waste by-product of road resurfacing and maintenance operations. The current and most common DGS disposal method in North Carolina involves the transportation of the DGS from the construction site to an offsite press-plate system, where the solid and liquid fractions are separated by machine. The reclaimed water is then transported back to the construction site and reused. This, however, requires a lot of time, money, and labor. Separation of DGS solids from wastewater with sediment basins, and onsite wastewater disposal may offer some advantages for improving DGS disposal efficiency.

With over 130 planned road projects between 2024 and 2033, there is a growing need for improved approaches to manage the resulting influx of waste. With the majority of existing DGS disposal research coming from the western and central U.S., less is known about the impacts of DGS and associated wastewater on the more acidic, highly weathered soil found in the southeast. This research aims to complete four objectives: 1) Determine a range of reasonable estimates for volume of DGS wastewater generated in a typical grinding operation. 2) Use greenhouse experiments to determine effects of varying DGS wastewater application rates on soil properties and vegetation establishment. 3) Test the same DGS wastewater application effects at field scale. 4) Develop site-specific DGS wastewater application recommendations.

A review of the data collected will investigate if using this wastewater on site is feasible, increasing the cost-effectiveness of sediment basin separation. Through greenhouse and field trials, wastewater application as irrigation will be tested for its effect on vegetation establishment and growth, as well as possible impacts on soil properties and the environment. The results of this research would allow the NCDOT and the NCDEQ to make informed decisions regarding the current permitting process for DGS sediment basins and the land application of the slurry or its wastewater.