1. 2004 Biological Wastewater Treatment Operators School
Advanced Treatment Systems
May 13, 2004
Dean Pond, Black & Veatch

2. Advanced Treatment Systems
What are the forms of nitrogen found in wastewater?

3. What are the forms of nitrogen found in wastewater?
TKN = 40% Organic % Free Ammonia
Typical concentrations:
Ammonia-N = mg/L
Organic N = 10 – 35 mg/L
No nitrites or nitrates
Forms of nitrogen:
Organic N
Ammonia
Nitrite
Nitrate
TKN
Total N

4. Advanced Treatment Systems
Why is it necessary to treat the forms of nitrogen?

5. Why is it necessary to treat the forms of nitrogen?
Improve receiving stream quality
Increase chlorination efficiency
Minimize pH changes in plant
Increase suitability for reuse
Prevent NH4 toxicity
Protect groundwater from nitrate contamination

6. Advanced Treatment Systems
What are the effects of N and P in receiving waters?

7. What are the effects of N and P in receiving waters?
Increases aquatic growth (algae)
Increases DO depletion
Causes NH4 toxicity
Causes pH changes

8. Advanced Treatment Systems
Why is it sometimes necessary to remove P from municipal wastewater treatment plants?

9. Why is it sometimes necessary to remove P from municipal WWTPs?
Reduce phosphorus, which is a key limiting nutrient in the environment
Improve receiving water quality by:
Reducing aquatic plant growth and DO depletion
Preventing aquatic organism kill
Reduce taste and odor problems in downstream drinking water supplies

10. Advanced Treatment Systems
How is P removed by conventional secondary (biological) wastewater treatment plants?

11. How is P removed by conventional secondary (biological) WWTPs?
Biological assimilation
BUG = C60H86O23N12P
0.03 lb P/lb of bug mass
GROW BUGS, WASTE BUGS = REMOVE P

12. Advanced Treatment Systems
Where in the treatment plant process flow could chemical precipitants be added?

13. Where in the treatment plant flow could chemical precipitants be added?
At pretreatment
Before primary clarifiers
After aeration basins
At final clarifiers
Ahead of effluent filters
Considerations:
Effective mixing
Flexibility
Sludge production

14. Advanced Treatment Systems
How is N removed or altered by conventional secondary (biological) treatment?

15. How is N removed or altered by secondary (biological) treatment?
Biological assimilation
BUG = C60H86O23N12P
0.13 lb N/lb of bug mass
Biological conversion by nitrification and denitrification

16. Nitrification NH4+  Nitrosomonas  NO2- NO2-  Nitrobacter  NO3-
Notes:
Aerobic process
Control by SRT (4 + days)
Uses oxygen  1 mg of NH4+ uses 4.6 mg O2
Depletes alkalinity  mg NH4+ consumes 7.14 mg alkalinity
Low oxygen and temperature = difficult to operate

17. Denitrification
NO3-  denitrifiers (facultative bacteria)  N2 gas + CO2 gas
Notes:
Anoxic process
Control by volume and oxic MLSS recycle to anoxic zone
N used as O2 source = 1 mg NO3- yields 2.85 mg O2 equivalent
Adds alkalinity  1 mg NO3- restores 3.57 mg alkalinity
High BOD and NO3- load and low temperature = difficult to operate

18. Advanced Treatment Systems
What are typical flow application rates in tertiary filters?

19. What are typical flow application rates in tertiary filters?
Automatic backwash filters (1-2 ft media depth) = 2 to 4 gpm/sf
Deep bed filters (4-6 ft media depth) = 4 to 8 gpm/sf

20. Advanced Treatment Systems
What are typical backwash rates for a tertiary filter (in gpm/sf)?

21. What are typical backwash rates for a tertiary filter (in gpm/sf)?
Automatic backwash filters
20 to 25 gpm/sf
5 to 10% of throughput
Deep bed filters
15 to 20 gpm/sf
3 to 5% of throughput

22. Advanced Treatment Systems
Define advanced treatment…

23. Define advanced treatment …
Treatment that improves or enhances secondary treatment processes
Further removal of organics, nutrients and dissolved solids

24. Advanced Treatment Systems
Explain circumstances under which advanced treatment may be necessary…

25. Explain circumstances under which advanced treatment may be necessary…
Limited assimilative capacity of stream
Toxicity reduction / elimination
Nutrient control
Closed systems
Water reuse

26. Advanced Treatment Systems
Identify and explain the objectives of the following advanced treatment systems:
Further removal of organics
Further removal of suspended solids
Nutrient removal (N and P)
Removal of dissolved solids

27. Identify and explain the objectives of the following advanced treatment systems:
Further removal of organics
Reduce effluent BOD to reduce receiving stream DO depletion
Improve disinfection
Reduce effluent N to improve water quality
Further removal of suspended solids
Removing TSS removes BOD
Removing TSS removes N and P (BUG = C60H86O23N12P)
Protects stream  sediment oxygen demand
Improves efficiency of disinfection

28. Removal of nutrients (N and P)
Identify and explain the objectives of the following advanced treatment systems:
Removal of nutrients (N and P)
Reduce oxygen demand of receiving stream
Control nutrients and algae
Control taste and odor in downstream drinking water
Suitability for reuse (examples: boiler water recycle, irrigation – N&P control of runoff, groundwater recharge)

29. Removal of dissolved solids
Identify and explain the objectives of the following advanced treatment systems:
Removal of dissolved solids
Removal of specific pollutant – zinc, chromium, lead
Pretreatment of industrial waste
Control effluent toxicity
Make suitable for reuse

30. Advanced wastewater treatment… Describe the purpose or procedure and mechanism by which it is done for each of the following:
Activated carbon adsorption
Chemical coagulation
Flocculation
Phosphorus removal
Nitrogen removal
Effluent Filtration
Polishing lagoons
Nitrification
Denitrification
Ammonia striping
Alum or ion precipitation
Lime precipitation
Reverse osmosis (RO)
Electrodialysis

31. Activated Carbon Adsorption
Purpose
Tertiary treatment
Removal of low concentration organic compounds
Application:
Influent Primary Trt Biological Trt  Filtration Carbon Disinfection
Many variations

32. Activated Carbon Adsorption
Continued …
Carbon Regeneration
5 to 10% loss
Less capacity than new carbon
Hot 350oF
Chemicals (sodium hydroxide)
Fire / Explosion
Carbon usually replaced after 5 regenerations
Mechanism:
Active sites “Activated Carbon”
Molecular bonding
Particles adhere to surface

33. Chemical Coagulation Purpose Application Chemical feed with rapid mix
Enhanced removal of organics and fine particles
Addition of lime, alum, iron, polymer to change ionic charge
Application
Chemical feed with rapid mix
Ahead of final clarifiers
Ahead of filtration

34. Chemical Coagulation Lime+ Heavy metals Alum+ SS removal
Continued …
Lime+ Heavy metals Alum+ SS removal
SS removal P removal
P removal
Polymer + - SS control Iron+ SS removal
Mechanism:
Destabilization by ionic charge neutralization
Reduce charge that keeps small particles apart
Aluminum sulfate
Ferric chloride
Ferric sulfate
Ferrous sulfate _ _ _ _ + + _ + + _ _ _ + + _ + + + + _ _ + _ _ + + + _ + + _ + + + + + + _ _ + _ _ + _ _ + + + + _ _ + _ _ _ _ _ + _ + + + + + +

35. Flocculation Purpose Application
Produce larger, more dense floc particles that will settle or filter easily
Application
Gentle mixing after rapid mix (coagulation)
Mixing – Mechanical or Aeration Q
Infl Q
Gentle
Mix /
Flocculation
Rapid
Mix /
Coagulation
Sludge

36. Flocculation Mechanism
Continued …
Mechanism
Coagulated particles strung together into larger floc particles (snow flake floc) +

37. Phosphorus Removal Purpose Application / Mechanism Reduce effluent P
Biological or chemical method
Reduce nutrient load on stream
Reduce algae growth
Reduce oxygen depletion
Application / Mechanism
Biological
Chemical

38. Phosphorus Removal Biological Continued … RAS WAS P Release
Final
Clarifier
RAS
WAS
Effl Q
P Release
Anaerobic
Zone
Aerobic
P Luxury Uptake
P Removal

39. Phosphorus Removal Chemical Continued … Chemical Coagulant Chemical
Primary
Clarifier
Aerobic
Zone
Effl
Final
Clarifier Q
Chemical
Coagulant
Chemical
Coagulant
RAS
WAS
P Removal

40. Nitrogen Removal Purpose Application / Mechanism
Reduce effluent N (ammonia and nitrates)
Biological or chemical
Reduce nutrient load on stream
Reduce algae growth
Reduce oxygen depletion
Application / Mechanism
Advanced Activated Sludge Processes
Nitrification (remove ammonia)
NH4  NO2  NO3

41. Nitrogen Removal Deep Bed Filtration Air Stripping Continued …
Denitrification (remove nitrate)
NO3  NO2  NO, N2O or N2 gas
Deep Bed Filtration
Anaerobic fixed film bacteria (denitrify)
Air Stripping
Removes ammonia
Elevated pH to NH4 as gas Q
Media
6-8’
Methanol
(carbon) Q

42. Effluent Filtration Purpose Application Remove SS (usually after FC)
Reduce BOD and insoluble P
Application
Deep Bed
4-6’ sand and gravel
Large cells 10’ x 30’
Similar to WTP
(batch backwash)
hL = ft
$$$
2. Traveling Bridge
1-2’ sand and anthracite
Small cells 1’ x 14’
Contiuous backwash
hL = ft

43. Effluent Filtration Loading Rate Mechanism Backwash
Continued …
Loading Rate
Backwash
2 – 4 gpm/sf
Frequency depends on loading
20 – 25 gpm/sf
5 – 15% of throughput
Must clean beds
Air scour
Mechanism
Filtration by granular media

44. Polishing Lagoons Purpose Application
To further treat or polish the effluent
After final clarifier
Facultative pond (aerobic and anaerobic)
Application
Typical volume = 1 day average flow
i.e., 1 mgd plant = 1 mgd lagoon
24 hour detention time
Surface aerators

45. Polishing Lagoons Mechanism
Continued …
Sunlight
Surface
Aerator
Algae M
Settling
Aerobic
Anaerobic
Sunlight  Photosynthesis  Algae + Organics & Nutrients
Organic Matter  Anaerobic Decomposition
Mechanism
Algae and bacteria grow in pond consuming organics and nutrients in FC effluent. Algae settles and degrades by anaerobic process.
methane
gas

46. Nitrification Purpose Application Mechanism
Reduce ammonia on plant effluent
High ammonia concentrations are toxic to streams
Quickest impact on DO versus nitrates
Application
SRT > 3 days in activated sludge process
Grow Nitrosomonas and Nitrobacter
NH4  NO2 NO3
Mechanism
Biological conversion of ammonia to nitrate

47. Denitrification Purpose Application Mechanism
Reduce nitrate on plant effluent
Usually in combination with nitrification to reduce Total N to the stream
Application
Activated Sludge Process
Deep Bed
Filters
Mechanism
Biological conversion of nitrate to N2 gas Q
Anx
Oxic FC
Oxic Recycle
RAS
WAS

48. Ammonia Stripping Purpose Application / Mechanism
Reduce ammonia either before or after biological treatment
Not commonly used in the US
Application / Mechanism
Raise pH  10.8 to 11.5, usually by adding lime
Move equilibrium point to ammonia 250C and pH 11
NH4 gas = 98%

49. Ammonia Stripping
Continued …
Break wastewater into droplets and strip off ammonia gas with air
Freefall through tower that circulates a lot of air to remove ammonia to atmosphere
NH4
Air
Lime Q
NH4
Stripper
Floc
Precip.
Lime Sludge
Air Q

50. Alum or Iron Precipitation
Purpose
To remove orthophosphate
Application
As a backup to Bio-P process
As chemical P removal
As chemical process
Mechanism
Al+ or Fe+ + PO4  Aluminum or Iron Phosphate
Al+ or Fe+ Q
Filtration
Optional Q
Precipitate
Rapid
Mix
RAS
WAS + Precipitate

51. Lime Precipitation Purpose Application Mechanism
P removal before primary clarifier or following biological treatment
Application
As a backup to Bio-P process
As chemical P removal
As chemical process
High pH can be a problem in effluent or in biological treatment
Mechanism
Chemical conversion of phosphorus to calcium phosphate is in pH range of 9.5 to 11.0

52. Reverse Osmosis (RO) Purpose Application Mechanism
High quality removal of various salts – calcium, sodium, magnesium
Application
Water reuse
AWT
Mechanism
Chemical separation / filtration across a semi-permeable membrane
High pressure
Tertiary process
Used in Gulf War to treat sea water sodium removal

53. Electrodialysis Purpose Application Mechanism
Removal of ionic inorganic compounds
Application
AWT
Medical
WTP
Clinical
Mechanism
Apply electrical current between two electrodes
Water passes through semi-permeable membranes (ion-selective)
Alternate spacing of cation and anion permeable membranes
Cells of concentrated and diluted salts are formed

54. Electrodialysis Purpose Application Mechanism
Removal of ionic inorganic compounds
Application
AWT
Medical
WTP
Clinical
Mechanism
Apply electrical current between two electrodes
Water passes through semi-permeable membranes (ion-selective)
Alternate spacing of cation and anion permeable membranes
Cells of concentrated and diluted salts are formed
Sludge – concentrated salt waste stream as process reject water
Problems – plugging, fowling of membranes, MUST pretreat activated carbon, multi-media filtration _ +
H20
Cl- H+ _ +
OH-
Na+
Bipolar Membranes

55. Advanced wastewater treatment… What would be the effect on sludge production for each of the following advanced treatment processes?
Activated carbon adsorption
Chemical coagulation
Flocculation
Phosphorus removal
Nitrogen removal
Effluent Filtration
Polishing lagoons
Nitrification
Denitrification
Ammonia striping
Alum or ion precipitation
Lime precipitation
Reverse osmosis (RO)
Electrodialysis

56. TANSTAAFL (tanstaffull)
What would be the effect on sludge production for each of the advanced treatment processes?
TANSTAAFL (tanstaffull)
“There ain’t no such thing as a free lunch.”
REMOVE MORE STUFF = GET MORE SLUDGE
More BOD & TSS Removal  MORE SLUDGE
Add chemicals  MORE SLUDGE
N & P Removal  MORE SLUDGE
Some processes produce more sludge than others:
Electro/mechanical – some sludge
Biological – more sludge
Chemical – MOST sludge