This landfill is operated by World Wide
Landfill Sdn Bhd; under a 25 year concession agreement with the Kuala Selangor
state government. They started operations on 1st January 2007. The landfill is 160 acres big and is
designed with a capacity to hold 6 million tons of waste. Currently approximately 2000
tons of waste is disposed off at the landfill every day, and to-date 4.1
million tons of waste has been added to the landfill. World Wide Landfills
estimate that the area will be completely filled by 2017. Hence the company is
in planning stage to acquire 100 acre land near the existing site to extend the
lifetime of this landfill.
The current list of clients of the landfill
include the city councils of Shah Alam and Petaling Jaya, the municipal
councils of Subang Jaya and Klang, the district council of Kuala Selangor and
private waste collectors. The landfill charges a tipping fee of RM 36 for each
ton of waste brought to the site by government collectors, and RM 50 for each
ton of waste brought in by the private collectors. The tipping fee is
calculated based on the price of purchasing and welding together liner
materials (presently it cost RM 100 per sq m). According to World Wide, the
district council of Kuala Selangor alone spends about RM 500 million per month
to dispose their waste at the site.
Landfill Waste Cell Design
The waste cells
are made by excavating earth to a depth of 3 m, the groundwater at the cell is
properly dewatered and made dry. Liners are laid; geo-membrane layer, 2 mm HDPE
layer, Geotextile layer followed by 2 inch aggregate layer. The three layers
are welded together by heat pressing at about 500 oC before the
aggregate layer is laid.
The initial design
was to stack up the cell up to 39 m, however due to the muddy nature of the
sediment (marine clay) the company is facing difficulty reaching this height.
The maximum they can stack up is 20 m now. This considerably reduces the
initially designed life-span of the landfill.
Construction of
retention walls etc. to allow stack to climb up 39 m is not cost effective.
Process flow in landfill
The waste trucks are weighed on arrival at
the entrance, each are allowed to dispose maximum 60 tons per day. Then they proceed
to the wet platform and dispose the waste into the respective waste cell and
return to re-weigh where the landfill personnel will calculate the net weight
of the waste disposed and charge accordingly.
Waste truck on weigh bridge (to measure weight)
Once the waste cells are filled they are
temporarily closed. The main by-products of waste cell are leachate and
landfill gas. The
gas generated is currently burned using a “Gas Flaring Unit”, but plans are
made to purchase a generator and use the landfill gas produced to generate
electricity.
The leachate produced is pumped into
treatment system that consists of three main stages; primary stage, secondary
stage and the tertiary stage. During the primary stage the leachate is passed
through three equalizations ponds (also referred to as Sequential Batch
Reactors) in
each pond the leachate is aerated for continuous 16 hours followed by 2 hour
break; each time the resulting supernatant is transferred to the next tank and
volume of remaining activated sludge measured if it exceeds 50% it is
transferred to sand bed, where it is dried and sent back to landfill. The same
process is repeated in the secondary stage but with only two Sequential Batch
Reactors. Once the secondary stage is completed the remaining liquid is
subjected to physical and chemical treatments to ensure compliance with DOE
standards[1]
Table 1 DOE standard
followed by Landfill to control quality of leachate
Parameter
|
Unit
|
Standard
|
Temperature
|
oC
|
40
|
pH
value
|
-
|
6.0
– 9.0
|
BOD5
at 20oC
|
mg/L
|
20
|
COD
|
mg/L
|
400
|
Suspended
Solids
|
mg/L
|
50
|
Ammoniacal
Nitrogen
|
mg/L
|
5
|
Mercury
|
mg/L
|
0.005
|
Cadmium
|
mg/L
|
0.01
|
Chromium,
Hexavalent
|
mg/L
|
0.05
|
Chromium,
Trivalent
|
mg/L
|
0.20
|
Arsenic
|
mg/L
|
0.05
|
Cyanide
|
mg/L
|
0.05
|
Lead
|
mg/L
|
0.10
|
Copper
|
mg/L
|
0.20
|
Manganese
|
mg/L
|
0.20
|
Nickel
|
mg/L
|
0.20
|
Tin
|
mg/L
|
0.20
|
Zinc
|
mg/L
|
2.0
|
Boron
|
mg/L
|
1.0
|
Silver
|
mg/L
|
5.0
|
Selenium
|
mg/L
|
0.02
|
Barium
|
mg/L
|
1.0
|
Fluoride
|
mg/L
|
2.0
|
Formaldehyde
|
mg/L
|
1.0
|
Phenol
|
mg/L
|
0.001
|
Sulphide
|
mg/L
|
0.50
|
Oil
and Grease
|
mg/L
|
5.0
|
Colour
|
ADMI
|
100
|
Tertiary treatment starts at the Dissolved
Air Floatation (DAF) lagoon, where suspended particles are removed, the
resulting liquid is then passed through a mixing tank which contain a coagulant
Ferrric Chloride to flocculate the solids, and Poly Acrylamide and Sodium
Hydroxide solutions. The liquid then passed through a DAF unit where the flocculent
is removed (as sludge). The
resulting liquid fed into Filter Press machine for 6 hours, the resulting
sludge bricks are
then taken back to landfill.
Before treatment with DAF unit (right) and after treatment to left
Sludge bricks produced by filtering process
Resulting liquid is subject through sand
filter (to remove remaining suspended solids) and activated carbon filter (to
remove unpleasant odor). Since the new standard issued by the DOE for leachate
requires them to reduce the Manganese level to 0.20 mg/L. Chemicals used to
reduce Manganese results in a higher color standard than that required hence
they now use an extra micro-filter after removal of Manganese in the liquid.
Activated Carbon Filter
The resulting water is discharged in the
river Sembilang (locally called Sungai Sembilang). A total of 450 cubic meter
of treated leachate is produced per day. It costs the company roughly RM 9 to
treat one cubic meter of leachate.
The company is required by the DOE to
monitor the level of Suspended Solids, Biological Oxygen Demand and pH of the
river, as they use to discharge treated leachate into river.
[1] Environmental Quality (Control of Pollution from Solid Waste
Transfer Station and Landfill) Regulation 2009 (PU(A) 433 - Second Schedule (regulation 13) Acceptable
conditions for discharge of leachate
