The document discusses removal of nitrogen and phosphorus from wastewater. It describes biological and chemical processes for nitrogen removal through nitrification, denitrification, and ammonia stripping. For phosphorus removal, it discusses the biological process where phosphorus accumulating organisms take up phosphate under aerobic conditions and release it under anaerobic conditions. The Ludzack-Ettinger and Modified Ludzack-Ettinger processes are presented for nitrogen removal, while the University of Cape Town (UCT) process is highlighted for combined nitrogen and phosphorus removal.

1. Removal of Nitrogen (N) and phosphorus (P)
Presented By
Md. Rafiqul Islam
ID: 0422042131
CE 6304
Theory of Sewage Treatment
Presented To
Dr. Md. Delwar Hossain
Department of Civil Engineering, BUET

2.  PROBLEM
Nutrient Pollution
(Eutrophication)
Outline Of the Presentation
 SOLUTION
1. Nitrogen Removal
Biological Process
Chemical process
2. Phosphorus Removal
Biological Process
Chemical process

3. Forms of Nitrogen
 Organic nitrogen, NH4
+, NH3, NO2
-, NO3
-
 Nitrogen present in the wastewater is present as:
 TKN (Total Kjeldahl Nitrogen): Organic Nitrogen + Ammonia
 TN (Total Nitrogen) : TKN + NO2
- +NO3
-

4. Nitrification
 Biological Process:
 2NH4
+ + 3O2 2NO2
- + 4H+ + 2H2O (Ammonia oxidizing bacteria
like Notrosomonas)
 2NO2
- + O2 NO3
- (Nitrate oxidizing bacteria like Nitrococcus)
 Overall 2NH4
+ + 4O2 2NO3
- + 4H+ + 2H2O (Nitrifiers)
 Synthesis of cells:
 Autotrophic: CO2 to cell mass.

5. Denitrification
 In the second stage of nitrogen removal heterotrophic bacteria
oxidizes organic substrate
 The process takes place under anoxic condition
 Bacteria utilize nitrite / nitrate as electron acceptor
 The process of denitrification goes on:
 NO3
- NO2
- NO N2O N2

6. Denitrification Process
 For organic substrate laden wastewater the overall denitrification reaction
can be represented as:
C10H19O3N + 10NO3 5N2 + 10CO2 + 3H2O + NH3 + 10OH-
 Here wastewater is a electron donor
 If required supplementary source of electron donor like “methanol” or
“acetate” is also added.
For methanol
5CH3OH + 6NO3
- 3N2 + 5CO2 + 7H2O +6OH-

7. Nitrogen removal using Ludzack- Ettinger process

8. Nitrogen removal using Modified Ludzack- Ettinger process

9. Chemical Nitrogen Removal
 Ammonia Stripping
NH4
+ NH3 + H+
 Depends on PH and Temperature
 PH must be in excess of 11 for complete conversion to NH3
 For economical reason, lime is the most common means of raising
the PH.

10. Forms of Phosphorus in wastewater
 Available to the micro-organism in the form of ortho phosphate (PO4
3-)
 Polyphosphate like Sodium Tripolyphosphote (Na5P3O10) are also concern
 Source: Detergents
 Total inorganic –P = Ortho-P + Polyphosphate

11. Phosphorus removal using biological method
 Biologically phosphorus is removed by Phosphorus accumulating
organisms (PAOs) by providing them alternatively aerobic and
anaerobic conditions.
Aerobic Conditions
 Stored products (PHB) are oxidized to
release energy
 Uptake phosphate within cell material and
gets phosphate enriched
 P-enriched cells are wasted with waste sludge
Anaerobic Conditions:
 Proliferation of PAOs occur
 PAO assimilate fermentation product
(acetate) into storage products
(polyhydroxybutyrate-PHB)
 Release stored polyphosphate as
ortho phosphate

12. Phosphorus removal using biological method

13. Combined N & P removal (University Of Cape Tower Process, UCT)