The Mills Filtration Plant in Riverside, California experienced consumer complaints from
manganese (Mn) after installing pre-ozonation followed by biologically active filtration. Test
results indicated that Mn, deposited after multiple years of using Mn-containing ferric
chloride (FeCl<sub>3</sub>) for coagulation, leached from the plant filter media. Using FeCl<sub>3</sub> without
filter chlorination, soluble Mn was released at a maximum concentration of 105 µg/L and took
approximately 2.5 weeks to fall below 50 µg/L, the U.S. Environmental Protection Agency (USEPA) secondary standard for Mn.
Core samples of the tri-media filter before and after the test revealed that only the anthracite-associated
Mn was removed (74 percent) from the filter. Pretreatment with alum coagulation
showed a more muted release curve (maximum 27 µg/L Mn) over ferric chloride coagulation.
By modulating the number of non-chlorinated filters within the plant, Mn was successfully bled
from the filters and the filters were allowed to go biological. However, elevated turbidity and
particle counts at the plant effluent limited the "controlled-release" option's usefulness.
Chemical cleaning of the filter media only removed Mn from the anthracite coal layer (>94%),
less so for the sand (~ 40%), and was ineffective on the hematite layer. Polyphosphates
successfully sequestered soluble Mn up to 105 µg/L and 10 days of holding time. Ultimately,
filter media replacement was recommended to avoid any further problems with Mn leaching from the filter media. Includes 24 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 1.9 MB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 20 |
| Published : | 06/17/2005 |
