4.3 Nutrient Removal/Recovery from Wastewater
107
mixed with the influent to the denitrification tank [20]. The denitrification depends
on the recycle flow and the available BOD of the influent.
Further improvement to the MLE process is the Bardenpho and Biodenipho
process in which an additional denitrification and nitrification stages are added
to provide further conversion of the nitrate to the nitrogen gas, as displayed in
Fig. 4.1d. The anaerobic (anoxic) tank after the initial anoxic process provides uptake
of phosphorous by microorganisms, and hence reduces phosphorous in the treated
wastewater.
– Alternatives to traditional biological methods
The patented SHARON process (single reactor system for high-activity ammonia
removal over nitrite) is a cost-effective alternative to the traditional biological
nitrogen removal process. It involves the oxidation of ammonia to nitrogen gas
by using nitrite as an electron donor without the need for the addition of external
organic matter. Compared to the traditional nitrification–denitrification method, the
SHARON process significantly reduces the organic matter and oxygen consumption
for nitrogen removal. This process is described as follows [21]:
2NH
+
4 + 3O 2 → 2NO
−
2 + 2CO 2 + 4H 2 O + 4H
+
(4.6)
2NO
−
2 + 4.8 g COD + 2H
+
→ N 2 + 1.8g sludge
(4.7)
Autotrophic anaerobic ammonium oxidation (ANAMMOX) is another alternative
to the traditional biological nitrogen removal process. In this method, ammonium is
directly oxidized by nitrite to N 2 by anaerobic ammonia-oxidizing bacteria such as
Planctomycetales. This method has low biomass yield, no need for aeration, and no
addition of external carbon sources [22–24].
NH
+
4 + NO
−
2 → N 2 + 2H 2 O
(4.8)
The main disadvantage of this method is the slow growth rate of the microorganisms which makes it difficult for implementation in wastewater treatment plants.
The combination of SHARON and ANAMMOX processes is more flexible and has
a more stable performance compared to each separate process. In the combination
method, partial nitrification (partial SHARON) is performed to transform ammonium
into nitrite. The nitrite-ammonium mixture is then converted into nitrogen gas. This
process is simplified as follows:
NH
+
4 +
3
4
O 2 + HCO
−
3 →
1
2
NH
+
4 +
1
2
NO
−
2 + CO 2 +
1
2
H 2 O Partial SHARON
(4.9)
107
mixed with the influent to the denitrification tank [20]. The denitrification depends
on the recycle flow and the available BOD of the influent.
Further improvement to the MLE process is the Bardenpho and Biodenipho
process in which an additional denitrification and nitrification stages are added
to provide further conversion of the nitrate to the nitrogen gas, as displayed in
Fig. 4.1d. The anaerobic (anoxic) tank after the initial anoxic process provides uptake
of phosphorous by microorganisms, and hence reduces phosphorous in the treated
wastewater.
– Alternatives to traditional biological methods
The patented SHARON process (single reactor system for high-activity ammonia
removal over nitrite) is a cost-effective alternative to the traditional biological
nitrogen removal process. It involves the oxidation of ammonia to nitrogen gas
by using nitrite as an electron donor without the need for the addition of external
organic matter. Compared to the traditional nitrification–denitrification method, the
SHARON process significantly reduces the organic matter and oxygen consumption
for nitrogen removal. This process is described as follows [21]:
2NH
+
4 + 3O 2 → 2NO
−
2 + 2CO 2 + 4H 2 O + 4H
+
(4.6)
2NO
−
2 + 4.8 g COD + 2H
+
→ N 2 + 1.8g sludge
(4.7)
Autotrophic anaerobic ammonium oxidation (ANAMMOX) is another alternative
to the traditional biological nitrogen removal process. In this method, ammonium is
directly oxidized by nitrite to N 2 by anaerobic ammonia-oxidizing bacteria such as
Planctomycetales. This method has low biomass yield, no need for aeration, and no
addition of external carbon sources [22–24].
NH
+
4 + NO
−
2 → N 2 + 2H 2 O
(4.8)
The main disadvantage of this method is the slow growth rate of the microorganisms which makes it difficult for implementation in wastewater treatment plants.
The combination of SHARON and ANAMMOX processes is more flexible and has
a more stable performance compared to each separate process. In the combination
method, partial nitrification (partial SHARON) is performed to transform ammonium
into nitrite. The nitrite-ammonium mixture is then converted into nitrogen gas. This
process is simplified as follows:
NH
+
4 +
3
4
O 2 + HCO
−
3 →
1
2
NH
+
4 +
1
2
NO
−
2 + CO 2 +
1
2
H 2 O Partial SHARON
(4.9)