Recycled Green Roof Media and its Effect on Water Quality

Open Access
- Author:
- Robinson, Byron C
- Graduate Program:
- Environmental Pollution Control
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- April 02, 2012
- Committee Members:
- Shirley Elizabeth Clark, Thesis Advisor/Co-Advisor
- Keywords:
- Green Roof
Water Quality
Class A Biosolids
Compost
Crumb Rubber
E. coli
Greenroof Water Quality - Abstract:
- Green roofing is listed as one of the best management practices (BMP) for the control of stormwater quantity (DEP, 2006). Green roofs can capture and retain rainwater, decrease the peak rate of runoff from roofs, and delay the runoff peak. In addition to quantity control, green roofs also may provide water-quality benefits. The focus of this research was the potential use of green roofs containing recycled materials as a pre-treatment device prior to rainwater harvesting for non-potable use. This project evaluated three recycled materials, crumb rubber, compost and biosolids, for their potential use in green roof media as complete or partial replacements for the current inorganic and organic components of green roof media. To be a viable green roof component the media must maintain or increase rainwater pollutant retention, compared to commercially-available green roof media, while not releasing problematic pollutants such as additional nutrients or heavy metals, e.g. the water collected afterwards would be safe enough for re-use in non-drinkable applications and/or discharge. In addition, the media must not have a substantial impact on plant growth. Two runs were performed, one without adding an E. coli spike on day two and one with the spike, to determine the impact of increased biological activity on pollutant retention in both commercial and recycled-component media. Both synthetic stormwater and the resultant effluent were collected from each media combination and were analyzed for the following parameters: Total Nitrogen, Total Phosphate, Chemical Oxygen Demand (COD), Nitrate, Ammonia, and Dissolved Copper. After analysis, the bacteria appeared to decrease or prevent an increase in concentration the following parameters: Nitrate, Total Nitrogen, and COD. In general, mixtures with the compost appeared to meet water quality guidelines, although decreasing the organic content to a level that the plants need, but no more, should further reduce any nutrient leaching.