1. WASTEWATER TREATMENT TECHNOLOGIES MEDAWARE
Prof. George Ayoub
Faculty of Engineering and Architecture
American University of Beirut

2. OUTLINE Overview of the Conventional Wastewater Treatment Process
Discussion of Existing Biological Treatment Technologies
Examples from the Mediterranean Region
Examples from the Lebanese Context

3. Conventional Wastewater Treatment Process
Pretreatment involves:
Screening
Grit Removal
Oil separation
Flow equalization
Chemical Treatment is used in conjunction with the physical and chemical processes:
Chemical precipitation
Adsorption
Sludge Treatment and Disposal involves:
grinding, degritting, blending, thickening, stabilization, conditioning, disinfection, dewatering, heat drying, thermal reduction, ultimate disposal
Disinfection can use:
Chlorine compounds
Bromine Chloride
Ozone
UV Radiation

4. Biological Treatment
In the case of domestic wastewater treatment, the objective of biological treatment is:
To stabilize the organic content
To remove nutrients such as nitrogen and phosphorus
Types:
Aerobic Processes
Anoxic Processes
Anaerobic Processes
Combined Aerobic-Anoxic-Anaerobic Processes
Pond Processes
Attached Growth
Suspended Growth
Combined Systems
Aerobic
Maturation
Facultative
Anaerobic

5. Major Aerobic Biological Processes
Type of Growth
Common Name
Use
Suspended Growth
Activated Sludge (AS)
Carbonaceous BOD removal (nitrification)
Aerated Lagoons
Attached Growth
Trickling Filters
Carbonaceous BOD removal. nitrification
Roughing Filters (trickling filters with high hydraulic loading rates)
Carbonaceous BOD removal
Rotating Biological Contactors
Packed-bed reactors
Combined Suspended & Attached Growth
Activated Biofilter Process
Trickling filter-solids contact process
Biofilter-AS process
Series trickling filter-AS process

6. Activated Sludge Process
The aeration tank contains a suspension of the wastewater and microorganisms, the mixed liquor. The liquor is mixed by aeration devices (supplying also oxygen)
A portion of the biological sludge separated from the secondary effluent by sedimentation is recycled to the aeration tank
Types of AS Systems: Conventional, Complete-Mix, Sequencing Batch Reactor, Extended Aeration, Deep Tank, Deep Shaft

7. Advantages/Disadvantages
Flexible, can adapt to minor pH, organic and temperature changes
Small area required
Degree of nitrification is controllable
Relatively minor odor problems
Disadvantages
High operating costs (skilled labor, electricity, etc.)
Generates solids requiring sludge disposal
Some process alternatives are sensitive to shock loads and metallic or other poisons
Requires continuous air supply

8. Trickling Filters
The trickling filter or biofilter consists of a bed of permeable medium of either rock or plastic
Microorganisms become attached to the media and form a biological layer or fixed film. Organic matter in the wastewater diffuses into the film, where it is metabolized. Periodically, portions of the film slough off the media

9. Advantages/Disadvantages
Good quality (80-90% BOD5 removal) for 2-stage efficiency could reach 95%
Moderate operating costs (lower than activated sludge)
Withstands shock loads better than other biological processes
Disadvantages
High capital costs
Clogging of distributors or beds
Snail, mosquito and insect problems

10. Rotating Biological Contactors
It consists of a series of circular disks of polystyrene or polyvinyl chloride that are submerged in wastewater and rotated slowly through it
The disk rotation alternately contacts the biomass with the organic material and then with atmosphere for adsorption of oxygen
Excess solids are removed by shearing forces created by the rotation mechanism

11. Advantages/Disdvantages
Short contact periods
Handles a wide range of flows
Easily separates biomass from waste stream
Low operating costs
Short retention time
Low sludge production
Excellent process control
Disadvantages
Need for covering units installed in cold climate to protect against freezing
Shaft bearings and mechanical drive units require frequent maintenance

12. Major Anaerobic Biological Processes
Type of Growth
Common Name
Use
Suspended Growth
Anaerobic Contact Process
Carbonaceous BOD removal
Upflow Anaerobic Sludge-Blanket (UASB)
Attached Growth
Anaerobic Filter Process
Carbonaceous BOD removal, waste stabilization (denitrification)
Expanded Bed
Carbonaceous BOD removal, waste stabilization

13. Anaerobic Contact Process
Untreated wastewater is mixed with recycled sludge solids and then digested in a sealed reactor
The mixture is separated in a clarifier
The supernatant is discharged as effluent, and settled sludge is recycled

14. Advantages/Disadvantages
Methane recovery
Small area required
Volatile solids destruction
Disadvantages
Heat required
Effluent in reduced chemical form requires further treatment
Requires skilled operation
Sludge to be disposed off is minimal

15. Upflow Anaerobic Sludge Blanket
Wastewater flows upward through a sludge blanket composed of biological granules that decompose organic matter
Some of the generated gas attaches to granules that rise and strike degassing baffles releasing the gas
Free gas is collected by special domes
The effluent passes into a settling chamber

16. Advantages/Disadvantages
Low energy demand
Low land requirement
Low sludge production
Less expensive than other anaerobic processes
High organic removal eficiency
Disadvantages
Long start-up period
Requires sufficient amount of granular seed sludge for faster start-up
Significant wash out of sludge during initial phase of process
Lower gas yield than other anaerobic processes

17. Major Anoxic and Combined Biological Processes
Type of Process
Type of Growth
Common Name
Use
Anoxic
Suspended Growth
Suspended Growth Denitrification
Denitrification
Attached Growth
Fixed-film Denitrification
Combined Aerobic, Anoxic, and anaerobic Processes
Single- or multi-stage processes, various proprietary processes
Carbonaceous BOD removal, nitrification, denitrification, phosphorus removal
Single- or multi-stage processes

18. Pond Treatment Processes
Common Name
Comments
Use
Aerobic Stabilization Ponds
Treatment with aerobic bacteria; oxygen is supplied by algal photosynthesis and natural surface reaeration; depth of 0.15 to 1.5 m
Carbonaceous BOD removal
Maturation (tertiary) Ponds
Use aerobic treatment; applied loadings are low to preserve aerobic conditions
Secondary effluent polishing and seasonal nitrification
Facultative Ponds
Treatment with aerobic, anaerobic and facultative bacteria; the pond has 3 zones: a surface aerobic zone, a bottom anaerobic zone, and an intermediate zone partly aerobic-anaerobic
Anaerobic Ponds
Treatment with anaerobic bacteria; depths of up to 9.1 m to conserve anaerobic conditions
Carbonaceous BOD removal (waste stabilization)

19. Examples from the Mediterranean Region (1)
Country
Name of the Plant
Capacity m3/day
Treatment Technology
Reuse Application
Spain
Vitoria
55,000
Secondary treatment (screening, sedimentation, nitrification-denitrification) + tertiary treatment (coagulation-flocculation, sand filters, chlorine disinfection)
Irrigation of orchards
Tenerife
90,000
Secondary treatment (activated sludge), tertiary treatment
Irrigation of banana, potatoes, and tomatoes
Greece
Chalkis
9,000
Pretreatment, clarification, aeration tanks, final clarifiers, advanced treatment
Irrigation of trees and bushes

20. Examples from the Mediterranean Region (2)
Country
Name of the Plant
Capacity m3/day
Treatment Technology
Reuse Application
Palestine
Dan Region Project
330,000
Secondary treatment (activated sludge, or stabilization lagoons), soil aquifer treatment
Irrigation of field crops, fruit plantations, vegetables, flowers
Italy
Grammich-elle
1,500
Activated sludge, chlorine contact tank, tank storage
Irrigation of orange, olive trees, crops for caning industry, and vegetables to be eaten cooked
Clatagiron-e
5,200
Activated sludge, sand filtration, reservoir storage
Cyprus
Larnaca
8,500
Oxidation ditches, sand filtration, chlorination
Irrigation of corn, alfalfa, in addition to gardens, parks and fields

21. Examples from the Mediterranean Region (3)
Country
Name of the Plant
Capacity m3/day
Treatment Technology
Reuse Application
Jordan
Al Samra
150,000
3 trains of ponds: 2 anaerobic, 4 facultative, 4 maturation
Irrigation of olive trees, forest area, fodder crops and non-restricted vegetables for experiments
Morocco
City of Drargua
600
Primary treatment (anaerobic basins), secondary treatment (sand filters), tertiary treatment
Irrigation of alfalfa, tomatoes, zucchini, corn and grass
Turkey
Gaziantep
200,000
Primary treatment, secondary treatment (Activated Sludge)
Irrigation of edible crops, vegetables and nearby fields

22. Examples from Lebanon
Lebanon has been rebuilding its water and wastewater infrastructure since 1992; in this context, the Government initiated the construction of large-scale WWTPs employing AS and Biofilter treatment systems mainly
Except for the Ghadir pre-treatment station, no single large-scale plant achieving secondary treatment has started to operate
Some community-based plants funded by NGOs are achieving secondary treatment; however, these are small-scale plants and rarely function properly

23. Technology to be used inside WWTPs proposed by the Government
Coarse Screening
Fine Screening
Grit and Grease Removal Tank
Pumping
Primary Settling Tank
Degassing Tank
Pumping
Aeration Tank or Biofilter
Treated Water Pumping Station
Venturi Flume
Distribution Structure
Secondary Settling Tank

24. Ghadir Preliminary Treatment Station
Serves the Greater Beirut Southern Wastewater Collection Basin (population of 977,000)
Maximum instantaneous flow: 2.6 m3/s; average: 1.6 m3/s; expected minimum: 1.1 m3/s
Accepts also septic tank septage and leachate from the Naameh landfill
Effluent is discharged into the sea at a distance of 2.6 km away from the shore and at a depth of 60 m
In periods of overflow, the plant partially or completely shuts down, and the effluent is discharged into the sea at a distance of 500 m from the shore
GHADIR STATION

25. Treatment Steps At Ghadir
LIFTING
SCREENING
DEGRITTING

26. Baalbeck WWTP Completed in summer 2000
Not yet functional because the collection network is not yet finished
Serves a population of 130,600, and has a daily capacity of 19,600 m3/day
Will achieve secondary treatment

27. Treatment Technologies in Community-based WWTPs
There are 42 plants as shown by the table
Process
NGO
CHF
CAI
MCI
YMCA PM
Extended Aeration 1 2 7
Activated Sludge 5 6
Anaerobic Digestion 17
Aerobic Digestion
Mixed Treatment
Total 18 10 8

28. EXTENDED AERATION
ACTIVATED SLUDGE

29. ANAEROBIC DIGESTION
AEROBIC DIGESTION
MIXED TREATMENT

30. EXTENDED AERATION
KAWS AKKAR
YMCA

31. ACTIVATED SLUDGE
KFEIR
YMCA

32. ANAEROBIC DIGESTION
HASBAYA
MCI

33. AEROBIC DIGESTION
MARJ EL ZOUHOUR
YMCA

34. WASTEWATER PONDS SYSTEM
MIXED TREATMENT
ADVANCED INTEGRATED
WASTEWATER PONDS SYSTEM
AIN HARSHA
YMCA

35. THANK YOU