Civil Engineering Reference
In-Depth Information
filtration
•
Use of Cl
2
reduces KMnO
4
requirement and therefore cost
complaints
Rapid reaction to oxidize both metals
Two chemicals required
•
•
Operationally simple
Not effective on organically complexed iron without a clarification
step
•
•
Readily accepted by regulatory agencies
•
KMnO
4
is corrosive, so special handling is required
•
Chlorine dioxide and
filtration
•
Effective for Fe removal
•
Mn removal requires significant reaction times
•
Can provide some benefits in terms of taste and odor
•
Not effective on organically complexed iron without a clarification
step
•
Provides primary disinfection
•
On-site generation required—operationally complex
•
High equipment costs
Oxide-coated or
catalytic media
Can be effective for both Fe and Mn removal
Media require regular or continuous regeneration to maintain
effectiveness
•
•
Greensand
•
Operationally simple
•
Media are sensitive to the TOC level in the raw water and may
not be effective
•
Use of greensand results in shorter filter runs and lower filter
loading rates because of the small media size
Manganese dioxide ore
Lowers chemical costs relative to using ozone or KMnO
4
MnO
2
ore media require very high backwash rates
•
•
Readily accepted by regulatory agencies
•
May allow oxidation of the Mn through the use of only Cl
2
•
Biological filtration
•
Capable of consistently producing lowest concentrations of Fe
and Mn and therefore the best water quality
•
Would require extensive pilot testing for acceptance by regulators
•
Will not apply to all water qualities
•
Simple operation—chemical handling minimized
•
Two-stage filtration required for high-rate Fe and Mn removal
•
Reduced backwash requirements, flows, and time
•
Limited experience in North America
•
Smaller space requirement because of high filter loading rates
•
Long initial start-up for manganese removal
•
Longer filter runs and less sludge production and handling
•
A short start-up period required after each shutdown of more than
7 days
•
Capital cost savings of 20 to 30% over conventional treatment
•
Operations and maintenance costs reduced by reduced chemicals
and fewer operations
•
Impacted by the presence of ammonium, zinc, and H
2
S
