WASTEWATER TREATMENT
TECHNOLOGIES
MEDAWARE
Prof. George Ayoub
Faculty of Engineering and Architecture
American University of Beirut
OUTLINE

Overview of the Conventional Wastewater
Treatment Process

Discussion of Existing Biological Treatment
Technologies
Examples from the Mediterranean Region

Examples from the Lebanese Context

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
Disinfection can use:
Chlorine compounds
Bromine Chloride
Ozone
UV Radiation
Sludge Treatment and
Disposal involves:
grinding, degritting, blending,
thickening, stabilization,
conditioning, disinfection,
dewatering, heat drying,
thermal reduction, ultimate
disposal
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-AnoxicAnaerobic Processes
Pond Processes
Attached Growth
Suspended Growth
Combined Systems
Aerobic
Maturation
Facultative
Anaerobic
Major Aerobic Biological Processes
Type of
Growth
Common Name
Use
Suspended
Growth
Activated Sludge (AS)
Carbonaceous BOD removal (nitrification)
Aerated Lagoons
Carbonaceous BOD removal (nitrification)
Attached
Growth
Trickling Filters
Carbonaceous BOD removal. nitrification
Roughing Filters (trickling
filters with high hydraulic
loading rates)
Carbonaceous BOD removal
Rotating Biological
Contactors
Carbonaceous BOD removal (nitrification)
Packed-bed reactors
Carbonaceous BOD removal (nitrification)
Combined
Suspended &
Attached
Growth
Activated Biofilter Process Carbonaceous BOD removal (nitrification)
Trickling filter-solids contact
process
Biofilter-AS process
Series trickling filter-AS
process
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
Advantages/Disadvantages
Advantages




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
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
Advantages/Disadvantages
Advantages



Good quality (80-90%
BOD5 removal) for 2stage 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
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
Advantages/Disdvantages
Advantages







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
Major Anaerobic Biological
Processes
Type of
Growth
Common Name
Use
Suspended
Growth
Anaerobic Contact Process
Carbonaceous BOD removal
Upflow Anaerobic SludgeBlanket (UASB)
Carbonaceous BOD removal
Attached
Growth
Anaerobic Filter Process
Carbonaceous BOD removal,
waste stabilization
(denitrification)
Expanded Bed
Carbonaceous BOD removal,
waste stabilization
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
Advantages/Disadvantages
Advantages



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
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
Advantages/Disadvantages
Advantages





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
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
Denitrification
Suspended
Growth
Single- or multi-stage
processes, various
proprietary processes
Carbonaceous BOD removal,
nitrification, denitrification,
phosphorus removal
Attached
Growth
Single- or multi-stage
processes
Carbonaceous BOD removal,
nitrification, denitrification,
phosphorus removal
Combined
Aerobic,
Anoxic, and
anaerobic
Processes
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
Secondary effluent
loadings are low to preserve aerobic polishing and seasonal
conditions
nitrification
Facultative
Ponds
Treatment with aerobic, anaerobic
Carbonaceous BOD
and facultative bacteria; the pond
removal
has 3 zones: a surface aerobic
zone, a bottom anaerobic zone, and
an intermediate zone partly aerobicanaerobic
Anaerobic
Ponds
Treatment with anaerobic bacteria;
depths of up to 9.1 m to conserve
anaerobic conditions
Carbonaceous BOD
removal (waste
stabilization)
Examples from the Mediterranean
Region (1)
Country
Name of Capacity Treatment
the Plant m3/day Technology
Reuse Application
Spain
Vitoria
55,000
Secondary treatment
(screening,
sedimentation,
nitrificationdenitrification) + tertiary
treatment (coagulationflocculation, sand filters,
chlorine disinfection)
Irrigation of orchards
Spain
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
Examples from the Mediterranean
Region (2)
Country
Name of Capacity Treatment
the Plant m3/day 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
Italy
Clatagiron
-e
5,200
Activated sludge, sand
filtration, reservoir
storage
Irrigation of orange, olive
trees, crops for caning
industry, and vegetables
to be eaten cooked
Cyprus
Larnaca
8,500
Oxidation ditches, sand
filtration, chlorination
Irrigation of corn, alfalfa,
in addition to gardens,
parks and fields
Examples from the Mediterranean
Region (3)
Country
Name of Capacity Treatment
the Plant m3/day 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
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
Coarse
Screening
Degassing Tank
Distribution
Structure
Fine
Screening
Pumping
Aeration Tank
or Biofilter
Technology to be
used inside
WWTPs proposed
by the Government
Grit and Grease
Removal Tank
Pumping
Secondary
Settling Tank
Primary Settling
Tank
Venturi Flume
Treated Water
Pumping Station
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
Treatment Steps At Ghadir
LIFTING
SCREENING
DEGRITTING
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
Treatment Technologies in
Community-based WWTPs
There are 42 plants as shown by the table
Process
CHF
Extended Aeration
Activated Sludge
Anaerobic Digestion
Aerobic Digestion
Mixed Treatment
Total
CAI
NGO
MCI
1
5
YMCA
PM
2
6
7
1
1
1
10
1
1
8
17
1
5
18
EXTENDED AERATION
ACTIVATED SLUDGE
ANAEROBIC DIGESTION
AEROBIC DIGESTION
MIXED TREATMENT
EXTENDED AERATION
KAWS AKKAR
YMCA
ACTIVATED SLUDGE
KFEIR
YMCA
ANAEROBIC DIGESTION
HASBAYA
MCI
AEROBIC DIGESTION
MARJ EL ZOUHOUR
YMCA
MIXED TREATMENT
ADVANCED INTEGRATED
WASTEWATER PONDS SYSTEM
AIN HARSHA
YMCA
THANK YOU