Grade 3 wastewater Exam Questions with Verified Answers| Latest Update Graded A+
Nitrification all or none Either mcrt is long enough to allow nitrifiers to populate the mixed
liquor or it's not. When mcrt is long enough complete nitrification will occur if enough DO is
provided.
1 lb ammonia-nitrogen oxidized during nitrification requires 4.6lbs oxygen
Nitrification is required because Reduce toxicity from release of unionized ammonia. Reduce
oxygen demand in receiving waters caused by nitrification. It's is the first step in nitrogen
removal.
Nitrification produces Makes acid which consumes alkalinity. This can cause drop in ph
which can interfere with treatment process.
Denitrification Reduction of nitrate to nitrogen gas. Facultative bacteria use nitrate ion as a
source of oxygen.
Operational problem of denitrification In secondary clarifier entrapped nitrogen gas causes
sludge to float to the surface, potentially allowing solids to escape in effluent. This can happen
when the activated sludge is not returned to the aeration basin quickly enough or if inadequate
DO is present in the mixed liquor when it is discharged to the secondary clarifier.
Second step in nitrogen removal Denitrification. Allows nitrogen gas to escape into the
atmosphere.
3 conditions required for denitrification to occur Nitrate present (nitrification must occur
first), no oxygen present, readily degradable BOD present.
Nitrogen removal plants Denitrification typically carried out in anoxic zones before the
aerobic zones in the aeration basins where the BOD is available. Nitrate is delivered to the
anoxic zone in the RAS flow and when used the mixed liquor recycle flow abbreviated MLR.
Nitrification all or none Either mcrt is long enough to allow nitrifiers to populate the mixed
liquor or it's not. When mcrt is long enough complete nitrification will occur if enough DO is
provided.
1 lb ammonia-nitrogen oxidized during nitrification requires 4.6lbs oxygen
Nitrification is required because Reduce toxicity from release of unionized ammonia. Reduce
oxygen demand in receiving waters caused by nitrification. It's is the first step in nitrogen
removal.
Nitrification produces Makes acid which consumes alkalinity. This can cause drop in ph
which can interfere with treatment process.
Denitrification Reduction of nitrate to nitrogen gas. Facultative bacteria use nitrate ion as a
source of oxygen.
Operational problem of denitrification In secondary clarifier entrapped nitrogen gas causes
sludge to float to the surface, potentially allowing solids to escape in effluent. This can happen
when the activated sludge is not returned to the aeration basin quickly enough or if inadequate
DO is present in the mixed liquor when it is discharged to the secondary clarifier.
Second step in nitrogen removal Denitrification. Allows nitrogen gas to escape into the
atmosphere.
3 conditions required for denitrification to occur Nitrate present (nitrification must occur
first), no oxygen present, readily degradable BOD present.
Nitrogen removal plants Denitrification typically carried out in anoxic zones before the
aerobic zones in the aeration basins where the BOD is available. Nitrate is delivered to the
anoxic zone in the RAS flow and when used the mixed liquor recycle flow abbreviated MLR.
