4. Introduction
At 2.8%, MENA has one of the highest average
population growth rates in the world.
This situation is compounded by the high
urbanization rate in MENA, which at 3.2%, is higher
than the rate for developing countries as a whole,
2.9%. Overall, within the region, about 80% of fresh
water is used in agriculture.
This means that the region will increasingly suffer
from twin and related problems of food and water
insecurity.
5. Most nations in the region are already importing virtual
water, in the form of food, and will likely have to increase
specific imports, such as cereal crops. Despite this, many
countries wish to increase fresh water supplies to
domestic, and industrial usages, and at the same time,
expand irrigated agriculture.
How can these seemingly contradictory objectives be
reconciled ????
6. The answer
is water demand management–more efficient water
use within all sectors. One specific component is to
increasingly reuse domestic wastewater .
this what we are called Wastewater Treatment by ;
Wastewater treatment plants, also called sewage
treatment plants or water pollution control plants,
remove most pollutants from wastewater before it is
released to local waterways.
7. Process of W.W.T
At the wastewater treatment plants, wastewater
undergoes five major processes :
Preliminary
treatment
Secondary
treatment
Primary
treatment
Sludge
treatmentDisinfection
8. Preliminary treatment : incoming wastewater, called influent, passes through
screens consisting of upright bars, spaced one to three inches apart. These bars
remove large pieces of trash including rags, sticks, newspaper, soft drink cans,
bottles, plastic cups and other similar items .
Primary treatment : Next, the wastewater enters primary settling tanks, also called
sedimentation tanks, for one to two hours. The flow of the water is slowed, allowing
heavier solids to settle to the bottom of the tank and the lighter materials to float .
Secondary treatment : Secondary treatment is called the activated sludge
process. This is because air and “seed” sludge from the plant treatment process are
added to the wastewater to break it down further .
Disinfection : Even after primary and secondary treatment, disease causing
organisms may remain in the treated wastewater to disinfect and kill harmful
organisms, the wastewater spends a minimum of 15-20 minutes in chlorine-contact
tanks mixing with sodium hypochlorite .
Sludge treatment :
1. Thickening
2. Digestion
3. Sludge dewatering
9. Methane Gas
Methane gas is often used as an energy source at
the wastewater treatment plants. The gas may be
used in engines to produce electricity or directly
drive plant equipment. Gas is also used in boilers
to provide heat for digestion and plant-wide
buildings.
Fuel cells convert the methane gas and carbon
dioxide into heat and electricity that is then used
to operate the plants. This technology efforts to
enhance clean air operations at its facilities. There
is a significant reduction in air emissions as a
result of using fuel cells.
10.
11. Benefits
There are several benefits of treated wastewater reuse :
1. It preserves the high quality, expensive fresh water for the
highest value purposes–primarily for drinking.
2. Collecting and treating wastewater protects existing
sources of valuable fresh water, the environment in
general, and public health.
3. Treated wastewater can sometimes be a superior source
for agriculture, than some fresh water sources. It is a
constant water source, and nitrogen and phosphorus in
the wastewater may result in higher yields than
freshwater irrigation .
13. Isn’t used to
irrigate
vegetables or
salad crops eaten
raw
Available
information on
crops and soil
sensitive to
wastewater
irrigation
Mapping sensitive
areas, such as
shallow aquifers
solution
14. Conclusions
Domestic WWTR is one tool to address the food
and water insecurity facing many countries in
MENA.
In most MENA countries, valuable fresh water will
have to be preserved solely for drinking, very high
value industrial purposes, and for high value fresh
vegetables and salad crops consumed raw .
The economic, social and environmental benefits
of such an approach are clear.
15. To help the gradual and coherent introduction of
such a policy, which protects the environment and
public health, governments shall have to adapt an
Integrated Water Management approach, facilitate
public participation, disseminate existing
knowledge, and generate new knowledge, and
monitor and enforce standards.
