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1. Dr. Alaadin A. Bukhari
Centre for Environment and Water
Research Institute
KFUPM
Tertiary Treatment of Domestic
Wastewater
By

2. PRESENTATION LAYOUT
•Introduction
•Tertiary Treatment Technologies
•Removal of Residual Constituents
–Suspended Solids Removal
–Nutrients Removal
–Removal of Toxic Compounds
–Removal of Dissolved Inorganic Compounds
•Tertiary Treatment of Wastewater in Saudi
Arabia
•Summary

3. •Definition
Further removal of suspended and dissolved
contaminants, not normally removed by
conventional treatment
Influent
Influent
Effluent
Prim ary
clarifier
Aeration
tank
Secondary
clarifier
Te rtiary
treatm ent
unit
INTRODUCTION

4. •Need of Tertiary Treatment of Wastewater:
–Continued increase in population
–Limited water resources
–Contamination of both surface and groundwater
–Uneven distribution of water resources and
–periodic draughts

5. •Typical Constituents Present in Wastewater:
–Suspended solids
–Biodegradable organics compounds
–Volatile organic compounds
–Toxic contaminants
–Nutrients
–Other organics and inorganics

6. •Options for reuse of treated wastewater

7. TERTIARY TREATMENT
TECHNOLOGIES
•Classification of Technologies
•Primary Treatment Systems
•Secondary Treatment Systems
•Tertiary Treatment Systems

9. •Factors affecting the selection of
treatment processes:
–The potential use of the treated effluent
–The nature of the wastewater
–The compatibility of the various operations
and processes
–The available means to dispose of the
ultimate contaminants, and
–The environmental and economic feasibility
of the various systems

10. Typical performance data:

11. •What are the contaminants removed
during tertiary treatment?
–Suspended solids
–Nutrients
–Toxic compounds
–Dissolved organics and inorganics

12. REMOVAL OF RESIDUAL CONSTITUNTS
• Suspended Solids Removal:
–Granular-medium filters
•the bed depth
•the type of filtering medium used
•whether the filtering medium is stratified or
unstratified
•the type of operation
–Microstrainers

13. Fig. 12a. Types of shallow-bed filters (a) mono-medium downflow,
(b) dual-medium downflow

14. Fig. 12b. Types of deep-bed filters (a) mono-medium
downflow, (b) mono-medium upflow

18. •Sizing of a filter:
–Principal design criteria of a filter design is water
flow rate and head loss
–Usually we know
•flow rate of influent
•surface loading rate
Flow rate
Surface area of filtering unit = --------------------------
Surface loading rate
•Head loss can be calculated using reference (MetCalf &
Eddy, 1991)

19. • Removal of Suspended Solids by Microscreaning:

21. •(II) Nutrients Removal
Basic nutrients present in the domestic wastewater are
–Nitrogen (ammonia, nitrite, nitrate)
–Phosphorus (soluble and insoluble)
–Sulfate
–Other compounds of nitrogen & phosphorus
Problems associated with nutrients presence in
wastewater are
–accelerate the eutrophication
–stimulate the growth of algae & rooted aquatic plants
–aesthetic problems & nuisance

22. –depleting D.O. concentration in receiving waters
–Toxicity towards aquatic life
–increasing chlorine demand
–presenting a public health hazard
–affecting the suitability of wastewater for reuse
•Nutrient Control could be accomplished by:
–physical methods
–chemical methods, and
–biological methods

23. Control and Removal of Nitrogen (Biologically):
•Removal of Nitrogen by Nitrification/Denitrification
Processes:
–It is a two step processes
aerobic
NH
4
-
—> NO
3
-
(nitrification)
anoxic
NO
3
-
—> N
2
(denitrification)
•Removal of Nitrogen by Nitrification Processes:
–1) Single-stage process
–2) Separate-stage process

24. Influent
Effluent
Prim ary
clarifier
Nitrification
tank
Nitrification
clarifier
Primary sludge
Returned sludge
Waste sludge
Fig. 8a. Typical carbon oxidation and nitrification processes
(single-stage)

25. S econdary
clarifier
Effluent
Nitrification
tank
N itrification
clarifier
Returned sludge
W aste sludge
Influent
Prim ary
clarifier
Aerobic
tank (BO D)
Prim ary sludge
Returned sludge
W aste sludge
Fig. 8b. Typical carbon oxidation and nitrification processes
(separate-stage)

27. •Nitrification/Denitrification systems can be
classified as:
(a) Combined Nitrification/Denitrification Systems
1) Bardenpho process(four stage)
2) Oxidation Ditch process
(b) Separate-Stage Denitrification Systems

28. Fig. 9a. Combined-stage nitrification/denitrification system (four-stage
Bardenpho)
Effluent
Aerobic
zone
Secondary
clarifier
W aste sludge
Influent
Aerobic com bined
oxidation nitrification
zone
Returned sludge
Anoxic
denitrification
zone
Anoxic
denitrification
zone
M ixed liquor return

29. Fig. 9b. Combined-stage nitrification/denitrification system
(oxidation ditch)
Aerator
Aerobic zone
Anoxic zone
Influent
Secondary
clarifier
Return sludge
W aste sludge

30. Fig. 10. Separate-stage denitrification process using a separate carbon
source
O
2
Denitrification
clarifier
Return sludge
Effluent
EffluentMedia
Carbon
source

31. •Control and Removal of Nitrogen (Physical &
Chemical Methods):
– air Stripping
– breakpoint chlorination
– selective ion exchange

32. Vent
Inflow
Packing media
Effluent
Air
Fig. 11. Cross-section of a countercurrent ammonia-stripping tower

33. •Breakpoint chlorination:
–Oxidation of ammonia-nitrogen can be done by adding
excess chlorine
–Basic chemical equations:
Cl
2
+ H
2
O  HOCl + H
+
+ Cl
-
NH
3
+ HOCl  N
2
 + N
2
O  + NO
2
-
+ NO
3
-
+ Cl
-

34. • Ion exchange process
Initial stage Final stage
NH
3
Na
+
Ca
++
Na
+
etc.
K
+
Na
+
Ca
++
NH
3
NH
3
NH
3
NH
3
Ion exchange
sites
Influent
Effluent

36. Phosphorus Removal
Biologically:
Key to the biological phosphorus removal is
the exposure of the microorganisms to alternating
anaerobic & aerobic conditions
• Phosphorus Removal Processes
–(1) Mainstream process
–(2) Sidestream process
–(3) Sequencing Batch Reactor (SBR)

37. Clarifier
Return sludge W aste
Influent
Effluent
Anaerobic
stages
Oxic stages
Fig. 12a. Biological phosphorus removal (mainstream process)

38. Influent Effluent
Aeration basin clarifier
Returned sludge
W aste sludge
Anaerobic
phosphorus
stripper
Fig. 12a. Biological phosphorus removal (sidestream process)

40. Removal of Phosphorus (Chemically)
•Commonly used chemicals are
–alum, sodium aluminate, ferric chloride, ferric sulfate,
lime, and etc.
•Factors affecting the choice of chemicals
•Influent phosphorus level
•Wastewater suspended solids
•Alkalinity
•Chemical cost
•Reliability of chemical supply
•Sludge handling facilities
•Ultimate disposal method
•Compatibility with other treatment processes

43. (III) Removal of Toxic Compounds:
Special attention is given to priority pollutants &
refractory organic compounds in recent years, due to:
– carcinogenic
– mutagenic
– teratogenic
– they are resistant to microbial degradation

44. •Treatment methods
–Biological
–Chemical
•chemical oxidation
•coagulation, sedimentation, and filtration
–Physical
•carbon adsorption
•air stripping

45. •(1) Carbon Adsorption:
It is an advanced wastewater treatment method used
for the removal of refrectory organic compounds as
well as residual amount of inorganic compounds
•Types of carbon contactors:
•Upflow columns
•Downflow columns
•Fixed beds
•Expanded beds

46. Fig. 17. Typical upflow countercurrent carbon column
Back wash drain
Influent
U nderdrain system
C arbon filling port
Effluent
Carbon column
W astewater flow

47. (2) Chemical Oxidation:
Chemical oxidation mainly done by
–chlorine
–chlorine dioxide, and
–ozone
Basic chemical equation:
Oxidant + Compound  CO
2
+ H
2
O + other products

48. (IV) Removal of Dissolved Inorganic
Compounds
–chemical precipitation
–ion exchange
–ultra-filtration
–reverse osmosis
–electrodialysis

49. Secondary
effluent
U ltra filtration
M ultim edia
filtrationt
D ecarbon
ation
R everse
osm osis
Polym er
Backwash
Reject
Reject
Effluent
Fig. 19. Ultrafiltration and reverse osmosis for the removal of
dissolved organics

50. Fig. 20. Processes of reverse osmosis (a) direct osmosis, (b) osmotic
equilibrium, (c) reverse osmosis
Fresh water Saline water Semipermeable
membrane
Osmotic pressure

52. Tertiary Treatment of Wastewater in
Saudi Arabia
•Large quantity of wastewater is being generated in
kingdom of Saudi Arabia
•Quantities of wastewater generated
–In 1994: Water Demand = 1.8 billion m
3
– WW Generated = 1.0 billion m
3
– WW Treated = 0.4 billion m
3
– WW Recycled = 0.1 billion m
3
–Water Demand in year 2000 = 2.8 billion m
3

53. Table 21: Present and projected flow of wastewater, generated
(m3/d) in three cities of kingdom
YEAR DAMMAM AL-KHOBAR QATIF
2000 242,057 118,539 100,766
2005 291,324 137,419 120,735
2010 326,985 159,306 144,785
2015 375,794 187,100 173,627
Source Al-Elaiw, M. (1994).

54. •Secondary treatment is practiced in Dammam,
Khobar, Qatif and Khafji
•Tertiary treatment is practiced in Royal
Commission of Jubail and Yanbu (RCJY)
•In Jubail 100% of tertiary treated wastewater is
being reused

56. •Summary:
–Growing demand and scarcity of water resources
necessitate the need for the tertiary treatment of
wastewater for reuse purposes
–Tertiary treatment of wastewater mainly depends on the
availability and practicality of technologies
–Selection of the processes depends on the requirement
–Residual contaminants to be removed during tertiary
treatment are suspended solids, nutrients, toxic
compounds, and dissolved inorganics