Beneficial Use of Water Treatment Residuals in Hydroseeding Operations

Consumers Pennsylvania Water Company (CPAWC) has conducted a demonstration project to evaluate the use of water treatment residual (WTR) in the reclamation of strip mine lands. The project was performed on land owned by CPAWC that is leased to a local coal operator. The WTR for this project was generated at the Roaring Creek Water Treatment Plant. Permission was obtained from the Pennsylvania Department of Environmental Protection (PA DEP), Bureau of Land Recycling and Waste Management, to conduct this project. The goal of this project was to evaluate the use of WTR in hydroseeding operations for establishing vegetation on strip mine areas. This is the first documented use of WTR for this purpose. If successful, this would have numerous benefits:CPAWC could beneficially reuse WTR, reducing reliance on conventional disposal methods, such as land surface disposal and landfilling.Support the pursuit of coproduct status for WTR. Coproduct status would allow the declassification of this WTR as a residual waste, and help to gain recognition as a valuable commodity.Enhance the recovery of strip mine lands, thus providing environmental benefits through reduced erosion, improved wildlife habitat, and proactive watershed management.Provide economic and logistical benefits to coal operators, hydroseeders, and CPAWC.The unique properties of WTR were expected to benefit the hydroseeding process and eventual site recovery. WTR was used in place of water, and was evaluated both as a water/binding agent mixture and as a tackifier after mulching. The project compared areas using conventional hydroseeding techniques to areas where the WTR were used in the process. The project was conducted on a 10- acre site where prior recovery efforts using conventional methods were unsuccessful in establishing an adequate vegetative cover.The project revealed that WTR provided benefits to site recovery as measured by results obtained after the first growing season. The site that used WTR as part of the hydroseeding mixture had a much higher percent coverage of plants compared to the control site that used conventional hydroseeding. This clearly indicated that the binding nature of WTR aided in retaining the seed mixture on the site, and contributed to enhancing seed germination. The site that used WTR as a tackifier exhibited greater retention of mulch compared to other sites. While first season plant yield data shows little difference compared to control sites, long-term site recovery will benefit from greater quantities of organic material retained on the soil surface. These retained organic materials will eventually decompose, become part of the soil matrix, and aid in further enhancement of the site.A steeply sloped area on one site received WTR treatment in hydroseeding and as a mulch tackifier. The percent coverage on this site was very high (visibly greater than 70%), and is considered a valuable result of this project. The combination of steep slope and poor soil conditions made this site very challenging, and showed the benefits of combining restorative techniques using WTR.Hydroseeding techniques also were enhanced using WTR. The lubricity of the WTR significantly reduced friction in hydroseeding pumps and piping, as evidenced by the ability of the hydroseeding mixture reaching a much greater distance. This minimizes the number of times that a hydroseeding truck must travel back and forth on a given site, and reduces compaction of the soil on the site. The dark color of the WTR allowed for a very clear indication of where the hydroseeding mixture was applied, thus helping to ensure complete yet efficient coverage.A comparison of soil test analyses before and after hydroseeding on sites using WTR revealed no detrimental impacts. With all these favorable results, combined with the consistent and unique qualities of this WTR, CPAWC was able to pursue and obtain coproduct status for their WTR from the PA DEP.