Water suppliers are putting bacteria to work for the removal of iron and manganese from drinking water. There are now three water suppliers in New England using this technology at their water treatment facilities. Biological filtration was the subject of a treatment session at the New England Water Works Association (NEWWA) Spring Conference in Worcester, MA on April 3, 2019 https://newwa.org/Events/SpringConference.aspx. I had the honor of moderating a session which included presentations that reviewed the theory, experiences pilot testing and lessons learned from the full scale treatment facilities.
The process of using bacteria for iron and manganese removal requires minimal chemical feed as compared with other technologies. Only the supply of air is required before the filters. Additionally, biological filtration is capable of removing much higher levels of iron and manganese with lower run times as compared with pressure filtration using manganese oxide coated media. However, the bacteria are contaminant specific so, depending on the levels of iron and manganese in the water supply, you may need one set of filters for iron removal and another set of filters for manganese removal.
Advantages of biological filtration include:
1. Ability to remove high levels of iron and manganese.
2. Longer filter run times between backwashes and lower backwash rates conserve water supply and energy.
3. Higher filter loading rate and smaller filter surface area and/or number of filters as compared with pressure filtration with manganese oxide coated media which may allow for a smaller building footprint.
4. Fewer chemicals required which simplifies operations and costs.
5. Operation of the filter system itself is similar to that of a traditional pressure filter system.
Disadvantages of biological filtration include:
1. Two sets of filters are needed for iron and manganese removal which may offset the space savings offered by the smaller filter surface area and higher loading rate ability.
2. Start-up times are longer than traditional treatment systems since it takes time to establish the bacteria colony and achieve iron and manganese removal, a process that can take days to weeks or even months in some cases.
3. Process can be taken off-line for brief periods (days) but would not be suitable for seasonally operated systems or sources.
4. Backwash supply must be from a non-chlorinated source.
In summary, biological filtration is a viable alternative for iron and/or manganese removal. Depending on the water supply, biological filtration may offer advantages that make this process an advantageous solution. If you are interested in hearing more about biological filtration, please contact us!
Comments