EFFECT OF THE PRESENCE OF PHOSPHATE BASED FERTILIZER ON METAL REMOVAL CAPACITY OF NATIVE BIORETENTION MATERIALS

Batch tests were conducted on several Texas native bioretention media to estimate the removal capacity of lead and copper from contaminated water and to understand the effect of the presence of phosphate (due to application of phosphate based fertilizers in the watershed) on metal removal. The results show that the 77% of lead and 58% of copper precipitated as the phosphate added to the contaminated water even before adding any media. Cedar mulch and hardwood mulch performed best and removed 99.2% of lead and 97.5% of copper from aqueous solution. When phosphate was added, removal increased to 97.8% for copper and 100% for lead (under detection limits). The removal capacity of metals was with the order of cedar mulch > hardwood mulch > pine mulch > sawdust > loam soil > silica sand. The leaching of metals from the media was much lower than the original solution and decreased when phosphate was added.