Restoring Anthracite Filter Media

Problem

Operated by American Water, the Woodlane Ground Treatment Plant supplies water to the Mt. Holly, New Jersey area. The well water is aerated, settled and then filtered through three pressure vessels containing manganese, greensand/anthracite filter beds to remove excessive manganese. Its filter media had been installed in 1992 and was scheduled for replacement in 2004 due to declining performance. American Water considered using Blue Earth Labs’ Media Master cleaning chemistry as a cost-effective alternative to filter media exchange.

The first step in the cleaning process was to conduct an extensive laboratory analysis of the filter media to determine both the compositions and extent of the contamination. The analysis also determines the optimal dosing required for the cleaning. Media samples from all three pressure filters were tested.

Microscopic analysis showed that the anthracite was completely covered by a black crust and brown, grainy deposits. The original anthracite surface was not visible. Additionally, the samples contained nickel-sized mud balls as well as other solid aggregates.

Solution

Numerous chemical combinations of Media Master and Floran Catalyst® were explored. The most effective combination was a two-step treatment using 8 lbs. of Media Master and 0.7 gallons of Floran Catalyst per square feet of filter media. The treatment protocol resulted in a dry weight loss of 5-7% and released 2,970 mg of manganese and 6,260 mg of iron from each kilogram of media.

The results of the full-scale media treatments were consistent with the laboratory test results. The treatment resulted in the complete restoration of the anthracite and removal of the excessive coating on the greensand.

The cleaning procedure also removed significant manganese sludge from the vessels, which had built up over time and was not removed during backwashing. The manganese concentrations for all three filters dropped from 0.05 ppm before the treatment to 0.01-0.02 ppm after.

Results

Overall, Blue Earth Labs’ Media Master cleaning chemistry effectively returned 13 year-old greensand filters to near new operating conditions. The two-step treatment was less than a third of the cost of media replacement and saved the customer over $100,000. The entire three-filter project was completed in one week and removed approximately 10,000 pounds of contaminants from the filter with no noticeable side effects.