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.
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0422042131_Removal of N & P.pptx
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
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-
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