Biological Nutrient Removal From Municipal Wastewater

1. Biological Nutrient Removal From
Municipal Wastewater
1

2. INTRODUCTION
 Main problem - the rising concentration of nutrients
 Primary causes of eutrophication - nitrogen and
phosphorus
 Most recognizable manifestations - algal blooms.
 Symptoms - low dissolved oxygen, fish kills, murky
water and depletion of flora and fauna
2

3.  Biological Nutrient Removal ( BNR ) is a process used to
remove nitrogen and phosphorus using micro-organisms
3

4. 4

5. BNR PROCESSES
BNR mainly consists of :
 Biological Nitrogen Removal
 Biological Phosphorous Removal
5

6. 6
Effluent TN and TP Components

7. Biological Nitrogen Removal
 Ammonia, nitrate, particulate organic nitrogen and
soluble organic nitrogen
 Nitrification and denitrification
 Ammonia is oxidised to nitrite and nitrite is then oxidised
to nitrate
 Reduction of nitrate to nitric oxide, nitrous oxide and
nitrogen gas
7

8. Biological Phosphorous Removal
 Soluble and particulate phosphorous
 The treatment process designed to promote the growth of
PAOs
 PAOs convert available organic matter to PHAs
8

9. Common Treatment Processes
 Integrated Fixed Film Activated Sludge (IFAS) Process
 Sequential Batch Reactor ( SBR) Process
 Oxidation Ditch Process
 Membrane Biological Reactor (MBR) Process
 Moving Bed Biofilm Reactor (MBBR) Process
 Step Feed Process
9

10. Integrated Fixed Film Activated
Sludge Process (IFAS)
 Process combines fixed film technology with
conventional activated sludge
 Filter media are added to an aeration basin to increase
the overall microbe population
 Media can be fixed or floating
10

11. 11
Fixed Systems

12. 12
Floating Systems

13. 13

14.  Filter media provides surface area for the biological
growth to attach
 Fine-mesh screens should be installed at the influent end
 IFAS uses a secondary clarifier to settle sludge and
recirculate RAS
14
IFAS Continues..

15. 15IFAS Process

16. Advantages
 Higher capacity in same volume
 Reseeding of suspended phase
 Self-correcting system
16
IFAS Continues..

17. Sequential Batch Reactor Process
(SBR)
• Treat wastewater such as sewage or output from
anaerobic digesters or mechanical biological treatment
facilities in batches
• Consists of two or more identically equipped tanks
with a common inlet
17

18. 18

19.  There are five stages in the treatment process :
1) Fill
2) React
3) Settle
4) Decant
5) Idle
19
SBR Continues..

20. 20

21. Advantages
 Flexible and easy to operate
 Mixed-liquor solids cannot be washed out by hydraulic
surges
 Equalization is provided
 Quiescent settling provides low effluent TSS
 5 to 8 mg/L TN is achievable concentration
21
SBR Continues..

22. Disadvantages
 More complex process design
 Effluent quality depends upon reliable decanting facility
 May need effluent equalization of batch discharge before
filtration and disinfection
22
SBR Continues..

23. Oxidation Ditches
 Modified activated sludge
biological treatment
process that utilizes long
SRTs to remove
biodegradable organics
23

24. 24
 Treatment systems consist of a single or multi-channel
configuration within a ring, oval, or horseshoe-shaped
basin
 Horizontally or vertically mounted aerators provide
circulation, oxygen transfer, and aeration
 May also be operated to achieve partial denitrification
Oxidation Ditch Continues…

25. 25

26. 26

27. 27

28. Advantages
 More reliable owing to a constant water level and
continuous discharge
 Long hydraulic retention time and complete mixing
 Produces less sludge due to extended biological activity
 Energy efficient operations result in reduced energy costs
28
Oxidation Ditch Continues…

29. Disadvantages
 Effluent suspended solids concentrations are relatively
high compared to other modifications of the activated
sludge process.
 Requires a larger land area than other activated sludge
treatment options
29
Oxidation Ditch Continues…

30. Membrane Biological Reactor Process
(MBR)
 Combination of
microfiltration or
ultrafiltration with a
suspended growth
bioreactor
30

31.  Biological reactor with
suspended biomass
 Solids separation by
micro filtration
membranes with
nominal pore sizes
ranging from 0.1to
0.4µm
31
MBR Continues…

32.  Common configurations are :
1) Internal or submerged
2) External or sidestream
32
MBR Continues…

33. 33
External
Internal

34. 34

35. Advantages
 Higher volumetric loading rates
 Longer SRTs resulting in less sludge production
 Operations at low DO
 High quality effluent in terms of low turbidity, bacteria,
TSS and BOD
 Less space required for wastewater treatment
35
MBR Continues…

36. Disadvantages
 High capital costs
 Limited data on membrane life
 Potential high cost of periodic membrane replacement
 Need to control membrane fouling
36
MBR Continues…

37. Moving Bed Biofilm Reactor (MBBR)
 Consists of an activated sludge aeration system
 Uses polyethylene biofilm carriers operating in mixed
motion within an aerated wastewater treatment basin
 Bacteria/activated sludge that grow on the internal surface
of the carriers break down the organic matter
37

38. 38

39. 39

40. 40

41. Advantages
 Compact Design
 Expandable
 Single Pass Process
 Load Responsive
 Minimal Maintenance
41
MBBR Continues…

42. Step Feed Process
 Continuous flow process
 Influent flow is split to several feed locations
 Contains alternating anoxic and aerobic stages
42

43. 43

44. Advantages
 Nitrogen concentrations less than 5 mg/L are possible
 5 to 8 mg/L TN is achievable
44
Step Feed Process Continues…

45. Disadvantages
 More complex operation
 Potential Nocardia growth problem
 Requires dissolved oxygen control in each aeration zone
45
Step Feed Process Continues…

46. Comparison of BNR configurations
Process Nitrogen Removal Phosphorus Removal
IFAS Good Moderate
SBR Moderate Inconsistent
Oxidation Ditch Excellent Good
MBR Excellent Moderate
MBBR Excellent Good
Step Feed Moderate None
46

47. REFERENCES
1. Margarida Marchetto, “Technologies Used in the Wastewater
Treatment for Nutrient Removal”, International Journal of
Waste Resources, 2013, Vol. 3, Issue 2
2. American Society of Civil Engineers (ASCE), Environmental
and Water Resources Institute (EWRI), Water Environment
Federation (WEF) “Biological nutrient Removal (BNR)
Operation in Wastewater Treatment Plants”, 2005, Manual of
Practice No. 29
47

48. 3. Davood Nourmohammadi, Mir-Bager Esmaeeli, Hossein
Akbarian and Mohammad Ghasemian, “Nitrogen Removal in a
Full-Scale Domestic Wastewater Treatment Plant with
Activated Sludge and Trickling Filter”, Journal of
Environmental and Public Health, 2013, Vol. 5
4. Franklin. L. Burton, H David Stensel, “Wastewater
Engineering”, Tata McGraw – Hill Publishers, 2012, Edition 4
5. Santhosh Kumar Garg, “Sewage disposal and air pollution
engineering”, Khanna Publishers, 2012, Edition 24
48

49. Any Questions ????
49

50. Thank You
50