Bowker & Associates, Inc.
Services Qualifications Odor Information
Consulting Engineers
Specialists in Odor Control
& Corrosion Control in Sewer Systems & Wastewater Treatment Plants
CHEMICAL ADDITION TO CONTROL ODORS
Chemicals are often injected into or applied
to odor sources to reduce the generation and/or release of odor.
Injection of chemicals into wastewater or sludge for the purpose of controlling
hydrogen sulfide (H2S) is common practice. Although in some
cases containment and treatment of odorous air is not practical, it is the
experience of Bowker & Associates that chemical injection is a less
effective odor control technique. Available data suggest a reduction in
odor detectability (D/T) of up to 50 percent with chemical addition, whereas
containment/treatment systems can provide odor reductions of up to 95
percent. The following table summarizes the chemicals commonly used to
control hydrogen sulfide in wastewater.
|
SUMMARY OF HYDROGEN SULFIDE CONTROL TECHNIQUES |
||||||
|
Technique |
Frequency
|
Advantages |
Disadvantages |
|||
|
I. OXIDATION |
|
|
|
|||
|
Air injection |
Low |
Low cost, adds DO to wastewater to prevent further sulfide
generation |
Applicable only to force mains; potential for air
binding. Limited rate of O2 transfer |
|
|
|
|
Oxygen injection |
Low |
5 times solubility of air; high DO possible; economical in
force mains |
Applicable only to force mains; requires on-site
generation or purchase as liquid O2 |
|
|
|
|
Hydrogen peroxide |
Medium |
Effective for sulfide control in gravity sewers
or force mains; simple installation |
Costs can be high to
achieve low (<0.5 mg/L) sulfide; safety |
|
|
|
|
Sodium hypochlorite |
High |
Applicable to gravity
sewers or force mains; effective for broad range of odorants |
Safety considerations;
high chemical costs |
|
|
|
|
Potassium permanganate |
Medium |
Effective, powerful
oxidant; good for sludge handling applications |
High cost, difficult to handle |
|
|
|
|
II. PRECIPITATION |
|
|
|
|||
|
Iron salts |
High |
Economical for sulfide control in gravity sewers
or force mains |
Does not control non-H2S
odors; sulfide control to low levels may be difficult; increased sludge
production |
|
|
|
|
III. pH ELEVATION |
|
|
|
|||
|
Sodium hydroxide |
Medium |
Intermittent
application; simple, little equipment required |
Does not provide
consistent control; safety considerations |
|
|
|
|
Magnesium hydroxide |
Low |
Maintains pH at
8–8.5; adds alkalinity; economical for high (>5 mg/L) sulfide
levels; safe |
Requires mixer to
maintain slurry in suspension; cost is independent of sulfide concentration |
|
|
|
|
IV. OTHERS |
|
|
|
|||
|
Nitrate formulations |
High |
Can be used to prevent
sulfide generation or oxidize sulfide in gravity sewers and force mains; safe
to handle |
Dosages vary depending
on use: prevention vs. removal |
|
|
|
|
Anthraquinones |
Low |
Prevents sulfide
generation biochemically by disrupting sulfur cycle |
Not well developed;
results inconsistent and difficult to predict |
|
|
|