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1. Introduction
Municipal solid waste management is a challenging issue for the Sultanate of Oman because
of its adverse impacts on environment and public health. With population of almost 3 million
inhabitants, the country produces about 1.9 million tons of solid waste each year. The per
capita waste generation in Oman is more than 1.5 kg per day, among the highest worldwide.
Solid waste in Oman is characterized by very high percentage of recyclables, primarily paper
(26%), plastics (12%), metals (11%) and glass (5%). However the country is yet to realize the
recycling potential of its municipal waste stream.
The predominant waste disposal method in Oman is landfilling. Most of the solid waste is
sent to authorized and unauthorized dumpsites for disposal which is creating environment and
health issues. There are several dumpsites which are located in the midst of residential areas
or close to catchment areas of private and public drinking water bodies.
Solid waste management scenario in Oman is marked by lack of collection and disposal
facilities, as well as lack of public awareness about waste in the country. Solid waste,
industrial waste, e-wastes etc are deposited in very large number of landfills scattered across
the country. Oman has around 350 landfills/dumpsites which are managed by municipalities.
In addition, there are numerous unauthorized dumpsites in Oman where all sorts of wastes are
recklessly dumped.
1.1 Al Amerat Landfill
Al Multaqa engineered landfill or known as Al Amerat landfill is the first engineered sanitary
landfill in Oman. The project designed in 2001 in 2005 cell 1 was design by STRABAG LLC
and the tender documents and designs were prepared by a renown consultants FICHTNER ,
which began its operations in early 2011. Cell 2 was designed by SUEZ and award of the Cell
2 construction & Operation in 2014.
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The visit was arranged to Multaqa (Be’ah) site with approximately 40 students for around 3
hours from 9am to 12pm on 25th of March 2019 under supervision of Dr. Basim Al Khateeb,
responsible tutor and the visit was further accompanied by Mr. Khalid Al Maashari, the
project manager at Be’ah and Mr. Krishnan, the leachate plant supervisor.
1.2 Geographical information’s
The geographical location for Multaqa site on Longitude 23°20’21.2″N and latitudes
58°26’57.7″E .The plain, with slight gravel and sand inclination, is in the center of
mountainous region with height around 10 − 30 m in south and north as well as surrounded
by wadi in the northeast, east and west. The gravel bed wadi in the western region has depth
reaching 6 m and width of about 100 m. The eastern wadi reached depth of about 10 m.
Isolated rocks with height of approximately 10 m are scattered across the mountains
bordering in the southern region.
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1.3 Climate information’s

From end of November to March is a relatively cool winter

During the summer months (April to October) temperature seldom exceed 46 due
to the low elevation of the area and humidity can reach as high as 90%
1.4 Oman regulations of solid waste management system
Solid waste is managed in Oman by Be’ah, also known as the Oman Environmental
Services Holding Company S.A.O.C was established in 2007 and was granted
Authorization and the legal status as the Responsible institution for solid waste
management in all over Sultanate of Oman In 2009, by Royal Decree No 46/2009. It
develops rapidly in the management of waste materials and following the international
standards by pre-stating the suitable infrastructure, Restructuring the waste collection
service system and Promote awareness and knowledge of waste management in the
country.
Oman regulations of solid waste management are as pointed bellow:

Occupants of premises used for residential, commercial, industrial, agricultural or other
purposes shall store and dispose solid non-hazardous waste such that there is no nuisance
or hazard to the public health.

The collection, storage and transport of waste shall not produce nuisance or hazard to the
public health.

Occupants or users of residential areas shall deliver all waste produced from the use to the
system established for the collection of such waste.

The users of commercial, industrial, agricultural or any other sites waste except domestic
waste shall collect this waste and transport it in a safe manner to a site designated.

It is not permitted for any person to dispose of waste in place other than the waste
containers provided by the authority.
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License shall be issued for establishing waste treatment facilities and sanitary landfills.

The waste treatment facility and landfill shall be operated in a proper manner to ensure
the environmental protection.

Government has the right to carry out feasible studies to see the possibilities of re-use of
the components of waste.

Operators of waste treatment facility and landfills shall keep records of daily operation as
directed by the government.

The treatment and disposal of waste shall be carried out without creating any health or
environmental hazard. Waste treatment facility, landfill and dumping sites shall be
registered under government.

No solid non-hazardous waste shall be mixed with any category of hazardous waste at
any time.

An Environmental Impact Statement shall be prepared for each sanitary landfill or
dumping site.

The Government will issue a Master Plan Summery to all the projects involving the
collection, storage, transport, treatment and disposal of solid waste.

The Government will issue a permit to all the projects involving the collection, storage,
transport, treatment and disposal of solid waste.

Import of solid waste to the sultanate is prohibited except with the approval.
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2. Design of the project visited (Design aspect)
The landfill site, spread over an area of 9.6 hectares, consists of 5 cells with a total capacity
of 10 million 3 of solid waste and spread over an area of over 9.6 hectares. Each cell has 16
shafts to take care of leachate (contaminated wastewater).
All the shafts are interconnected, and will help in moving leachate to the leachate pump. The
project is part of the government’s initiatives to tackle solid waste in a scientific and
environment-friendly manner.
2.1 Design of cell 1
The first cell was completed within 4.5 years and it was designed with asphalt as base of the
cell. The base of the first cell was constructed by placing 8cm thick layer of asphalt followed
by 6 cm thick layer of asphalt. The two layers of asphalt provided to prevent the leachate to
infiltrate to the groundwater. However, the first cell has been constructed by a pyramid shape
with a slop of 1:2 vertical to horizontal. The total area of the first cell was 9.5 hectare with a
total capacity of one million tons. Moreover, the total height of the cell from the ground level
was 30 m. The solid waste has been placed by layers each layer of less than1m thick of noncompacted solid waste. The layers of solid waste have been covered daily by soil cover with
20 cm thick after compaction (AL Mashani, 2017).
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2.2 Design of cell 2
The second cell designed and management by SUES company. It is designed to hold more
capacity of solid waste, the total capacity of second cell is 2.4 million tons with area of 14
hectare and with slope of 1:3 vertical to horizontal.
As shown in figure () the base of second cell was consist of six layers. The first layer of
lining was made of Geotextiles which has been directly laid on the surface of landfill base.
Then, second layer was made of high shear strength Geo-synthetics clay liner (GCL) which
provided to prevent water to pass through lining layers. The GCL consist of two sheets and
the clay is located between these two layers. After that, 1.5mm thick layer of high density
polyethylene (HDPE) was laid to be a third layer. The HDPE layer is the most important
layer of lining because it is prevent leachate from mixing with underground water table. The
HDPE sheets are welded to be connected to each other and to close all openings. Moreover,
the forth layer of lining was HDPE Geo-net which provided to protect the HDPE layer from
damage due to large or sharp elements. Further, the fifth layer was high strength geotextiles
protection layer that used to protect lining layers from liquid or leachate. Finally, these five
layers were covered by 300 mm thick of compacted gravel layer to protect the lining system
from solid waste (AL Hinai, 2017)
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The final lining of the cell is designed according to the project life span. It will have a default
life as specified in the specification that starts from the grading layer to be placed directly on
the waste, then gas venting layer, posteriorly Geo-textile with puncture resistance of 3.5 KN ,
after that add the GCL Geo-synthetics clay liner, thereafter 1.5 mm LDPE liner, HDPE Geonet, then Geo-textile with puncture resistance of 10.5 KN ,In the end add a layer of natural
soil at a height of 400 mm
2.3 Design of leachate system
The leachate system designed for the first cell consist of 16 shafts. The shafts connected with
HDPE perforated pipes to collect the leachate from the cell. The width of the perforated pipes
is 100 , those pipes connected to header pipe with diameter of 150 . The collected
leachate from the cell will transferred to the evaporation pond. There are two evaporation
ponds in Al Multaga landfill, the total capacity of ponds is 10000 3 and it has 6 depth
(Ashor, 2017)
However, the groundwater may contaminated due to the resulting leachate from the disposal
of the solid waste. Therefore, wells provided to check the purity of the groundwater. Beah has
been provide five wells with 80 m deep. Two wells pored as upstream and three wells pored
as downstream (Ashor, 2017)
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2.4 Gas management system
In addition, other perforated pipes used to collect the produced gas from the landfill which
placed vertically to collect the gases. The diameter of these pipes is 200mm and placed inside
pore holes of 600mm diameter. The pipes should reach up to 2 m above the bottom to prevent
the penetration of liner layer (AL Mashani, 2017).
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2.5 Existing problems
Some of existing problems of design aspect which highlight the following points:

Gas emissions are issue, while the final covers of the cells are not done, the
atmospheric layer affected by harms gases like CH4, SH, etc which are released from
the cells

A vast number of tires which are stacked over each other and there is no clear way to
dispose them.
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3. Operational Aspects of Al Multaqa Facility
3.1 Source and composition of waste
The sources of the solid waste which allowed to enter Al Multaqa landfill are agriculture
waste, industrial waste, residential waste, commercial waste, municipal services waste
and any non-hazardous waste. While the composition of solid waste excepted in the
landfill are papers, cardboard, food waste, plastics, metals, glass, wood, street sweeping
and small electrical. However, there were some solid waste not disposed in the landfill
such as, paint tins, construction and demolition waste, used tyres, radioactive materials,
large electronic etc. (Beah, 2016)..
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3.2 Waste collection system
Beah sign a contracts with different private companies to collect waste needed to be disposed.
The contract may extend for 7 years and it can be renewal. The responsibility of waste
collection either on the site or near to it is the scope of private companies .The solid waste
collected from residential, institutional, commercial, and industrial area in Quraiat, Busher,
Matrah and AL Amerat a closed container that supplied by Beah. The waste is collected by a
small truck and its transfer to AL Misfah transfer station for short period of time. Then,
through the uses of hopper the solid waste will be loaded in a semi-trailer which stranded on
a ramp. After that, the solid waste will transfer to the landfill by semi-trailer (AL Hinai,
2017)
In addition to this, the solid waste collected from municipal activities will be transported by
special trucks belong to municipality. In some cases, collection trucks or bulk transportation
trailer are directly transfer the solid waste to the landfill because, the collection area is close
to the landfill. The average of solid waste which collected daily in Al Multaqa landfill is 1100
tons/day (AL Hinai, 2017).
Table: Number of solid waste shipment
Nature of Waste
Municipality Collection Truck
Municipality Bulk Transport Trailers
Private Companies Trucks
Total
Number of Shipments/ day
2467
490
2214
5171
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3.3 Operation and Maintenance
The solid waste that reach the landfill is weighted and the properties are mentioned. Nonhazardous waste will sent directly to disposal area. While hazardous and other unaccepted
wastes will be rejected. After the truck empty the waste in the specified area, the tuck will
pass through a certain area which contain water to wash out any materials stuck in the wheels
of trucks which may affect the environment. The trucks are re- weighted after cleaning to
identify the amount of waste.
The emptied waste which placed in the specified area is compacted by using 45kg weight of
landfill compactor with spiked steel wheels. The waste is placed in layers each layer less than
1m height. The compaction of solid waste will remove air, reduce or close the voids on the
waste and reduce the height of the solid waste layer up to 40%. Landfill life time will
increase when the compaction of the solid waste is properly processed. The compacted waste
has density of 0.95 ton/ 3 However, there are three different layer of soil used to cover the
compacted solid waste. First type is daily cover which used to protect the solid waste from
birds and animals, and it’s used to reduce the odor of waste. The daily coves of soil extended
to 20cm thick. The second type of soil cover provide in case temporary stop for a period of 3
months. The second layer is called inter mediate cover and it’s extended up to 30-40 cm.
Third type of soil cover called final cover and its used to cover the top of the cell after
completed. The final cover of soil extended to 40-50 cm (AL Mashani, 2017)
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The daily working area should be small area to ensure the well compaction of solid waste and
to ensure the coverage of solid waste with soil to prevent any animals and birds from spoiling
the compacted solid waste. The landfill should be maintained annually by the workers to
ensure of the safety and the good condition of the facility of the landfill. In addition to this,
pumps and equipment should be checked.
During site visit students observed 2 workers were cleaning the border of cell 2 and they were
interested to ask Mr. Khalid about the reason behind that “This is landfill, but when you
arrived the site do you feel it is landfill?? or normal mountains.” And my answer was normal
mountains, “they are cleaning the boarders because it is necessary to give aesthetic
appearance to the landfill”. From this answer I felt Bea’h vision “To conserve the
environment of our beautiful Oman for our future generation”.
Add to that, as shown in
figure() the student saw cat was sleeping in cell 1 which reflect clean atmosphere at landfill.
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3.4 Leachate Treatment
The leachate collection system is consist of different types of pipes which are perforated
pipes, shafts, evaporation pond. First, the perforated pipes are placed at top of the liner and
bottom of the cell. The leachate will pass through the perforated pipes and collected by
collection pipes that transferred the leachate to the shafts due to the gravity force. Then, the
leachate transfer from the shaft to the evaporation pond by gravity due to the slope of pipes.
There are two evaporation ponds in the landfill with capacity of 5000 3 for each one. After
that, by uses of mechanical pump the collected leachate in the evaporation pond will pumped
to leachate treatment facility (Ashor, 2017).
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The capacity of the leachate treatment facility is about 100 3 / day and it can be increased up
to 180 m/ day. However, the amount of leachate generated from the landfill is about 30-40
m’/day (Ashor, 2017).
After a period of time the leachate will move from the evaporation pond to the MBR station
to complete the process of treatment. The leachate treatment process consists of two main
stages which are biological and mechanical treatment. First stage, biological treatment which
aims to reduce the organic up to 95% . The biological treatment consists of 4 storage tanks
which are De-Nitrification, Nitrification 1, Nitrification 2 and Foam tank. The first tank of
the biological treatment is De-Nitrification tank which used for reduce the amount of BOD,
COD and 3 . This tank considered as anaerobic process, therefore the nitrate ( 3 ) will
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change into nitrite ( 2 ). During the broken of nitrate the amount of bacteria will be
reduced. The value of BOD and COD exceed 20000 mg/l before the treatment (Ashor, 2017).
The second tank is Nitrification 1 tank which considered as aerobic process used to supply
oxygen required for bacteria to complete the treatment process of leachate. The dissolved
oxygen will pumped to the tank by air blower. After oxygen pumped to the tank, the bacteria
will start decreasing the amount of organic matters. During to the uses of air blower, some
bubbles will form, therefore the leachate will transfer to foam tank to remove the bubble.
Also, the temperature will increase caused reduce in bacteria productivity. Automatic cooling
system is provided to avoid the loss of bacteria, when the temperature of leachate reaches
380 automatically leachate will flow to heat exchanger which cooled. The heat exchanger is
cooled by cooling tower. Then the leachate flow to the third tank which is Nitrification 2 tank
which apply the same process of the first Nitrification tank. The fourth tank is foam tank that
used to remove the bubbles generated during the uses of air blower. The upper layer of the
leachate which contains bubbles will transfer to the foam tank. In the foam tank, anti-foam
chemicals will be added to reacts with bubbles and to condensate the leachate. Then after
removing of bubbles, the leachate will flow again to the de-nitrification tank (Ashor, 2017).
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Second stage, mechanical treatment that consists of two steps which of physical and chemical
treatment. The leachate resulting from nitrification tank will pass to first container to apply
the Ultrafiltration process. In this process, the leachate will pass through 4 different rolled
membranes. Each membrane is located in separate pipe. In addition to this, there are two
extra pipes that may be needed in the future to increase the capacity of leachate to pass
through the ultrafiltration. The cells inside the membranes responsible for the separation of
solids from liquid. The particles resisting from the separation of liquid and soil that have
more than 1 m will be flow again to the de-nitrification tank. While the liquid without solids
will flow to the dewatering storage tank in container 2. In the dewatering storage tank some
chemicals such as, sulfuric acid to decrease the PH value of the liquid. Then, the water after
storage will flow to reverse osmosis container where salt is removed from the water (Ashor,
2017).
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Generally, the leachate treatment produces about 70 % of pure water and 30 % of retained
leachate. The retained leachate contain high amount of solids and organics. Therefore
retained leachate will be sent again to the landfill to continue the cycle of leachate life.
Treated leachate used in internal purposes as shown in figure () and cleaning, Aeration
system, cooling tower and cleaning plants … etc.
However, the whole process of leachate treatment is controlling and monitoring by using of
monitoring unit which located at the first container. There are some maintenance activities
used to increase the landfill treatment life such as Anti- Scalant. Anti- Scalant fluid used to
remove any membranes to ensure that all materials stuck in the membranes. Then, the
membranes are washed through the uses of pressurized water to ensure that all materials
stuck in the membranes.
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It is important to make sure that the operation goes properly. As mentioned in chapter 2 wells
used to cheek the purity of groundwater. Each 6 weeks they take sample from well as shown
in figure () and send it to the lab to compare the report with base line which is the first
reading before operation. As Mr. Khalid said they don’t found any leak from the first
operation till today which is mean the works done properly.
3.5 Existing problems
There are different problems that engineers face during the operation of the landfill. The most
important problem is the bad odors that mainly increase at high temperature such as,
afternoon period or in summer. The bad odor resulting from the solid waste is annoying the
people live near to the landfill. In addition, in rain season the solid waste will be saturated
with water. Therefore, the amount of leachate in the landfill will be increased. Also, the
compaction will be affected. Further, wind is one of the most problems especially in working
days because it may case volatilization of light and small substances. This problem can be
reduced by well compaction of solid waste, well compaction of soil cover, providing thin riprap layer on the side of cells or by surrounding fence of 6m high built up around the cells.
Moreover, the ability of ignition is very high because of the generated methane gas. So,
maintaining the safety of the landfill is very important to avoid any causes of fire.
In addition to landfill problems, there are problems related to the leachate facility. The most
important problem is the possibilities and qualifications are very poor. In the same time a lot
of tests on the parameters of treated leachate such as, COD, BOD TSS, heavy metals etc.
must be tested. Further to this, the generation of leachate is very slow therefore it gives more
period of time for the process.
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4. Contribution of Be’ah towards Environment
The proper disposal of solid waste in the sanitary landfill is affective process which protects
the environment, human health and other living organisms, The following points state the
advantages of engineering landfill:

Protect air, soil and water from pollution and contamination.

Avoid emissions of gases which cause pollution to the atmosphere.

Prevent spread animals and birds from spoiling the compacted solid waste Protect
groundwater from pollution due to leachate resulting from the disposal of solid waste

Reduce the odors in the landfill due to methane gas which produced from disposal
process of solid waste.

Prevent the waste and leachate from interfere with underground biological chain.
Prevent spread of chemicals and toxic element that may cause cancer or other hard
diseases

Avoid spread of volatile solid waste, produce methane gas can be used to produce
electrical power and energy
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5. Conclusion and Recommendation
All in all, this assignment was conducted to reflect the information about trip to Al Multaqa
engineered landfill. Mr. Khalid Al Mashani a site engineer who gave us a briefing about the
history of landfill facility. Add to that, he explained about the techniques which is used in
managing solid wastes, design and operational aspects of the landfills along with their
contribution towards countries environment. Moreover, Mr. Khalid gave as the opportunity to
observe the procedure of leachate treatment and outline of their operations.
Finally, I would recommend for Beah Company the following valid points which could help
them in developing their services:

As Mr. Khalid mentioned that the leachate generate after 2 months instead of 2 years
and after investigations and research they found that in general in GCC we don’t use
on-site segregation and this effect on duration of leachate form. From this point, I
recommend educating citizens on segregation of solid waste and let them feel
responsibility for our beautiful Oman. And supply special containers which have
divisions, so that each composition will place in separate division.

Take advantage of produced gas to generate electricity and energy Surround the
landfill area by tall trees with thick leaves to prevent the erosion of cells

Provide the site with warning signs to avoid fire causes such as, smoking. . Cover the
inclined slope with rip rap to avoid any loses from compacted solid waste and to
prevent air penetration
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