Processes from home to landfill


  • Metro News
  • Wednesday, 11 Mar 2020

The leachate treatment plant at the transfer station in Kepong has several tanks to remove suspended solids and de-acidify the effluent before releasing it into the river. — Photos: AZLINA ABDULLAH/The Star

EVERY day Marjohan Yaakob, 65, wakes up as early as 5.30am to get ready for his work as a rubbish collector with Alam Flora Sdn Bhd.

Dressed in his red uniform and blue hat, he begins his duty at 6.30am. He works six days a week.

Having served the company for the past seven years, he is accustomed to the stench that emanates from the rubbish truck that he rides in daily.

His colleague Amrin Buyung, 67, said apart from the smell, he did not face many challenges.

He, however, reminded city dwellers to refrain from disposing of rocks and wood.

“We are not supposed to load those items into the rubbish truck, ” he said.

The task performed by these two diligent men is a small part of the bigger picture of waste management in the city.

StarMetro follows the trail of a rubbish truck — from waste collection at homes to their pre-treatment at a facility and disposal in a landfill.

Pre-treatment facility

The transfer station in Taman Beringin, Kepong that has been operating since April 2002 is the only such facility in Kuala Lumpur.

It is owned by the Housing and Local Government Ministry and monitored by Solid Waste Management and Public Cleansing Corporation.

This 5.22ha facility is currently operated by Dhes, a subsidiary of Alam Flora.

Person-in-charge Mohd Hashanuddin Hussin said the waste collected would be compacted before being transported to the Bukit Tagar landfill, located some 60km away.

1 Rubbish collectors in the city begin work as early as 6.30am daily.1 Rubbish collectors in the city begin work as early as 6.30am daily.

“With compaction, more waste can be transported to the landfill at one time, ” he said, adding that the station received about 2,400 tonnes of waste daily. 

Hashanuddin said apart from compaction, another crucial step involved in the pre-treatment was leachate extraction from the waste.

“This is to ensure that no leachate drips onto the road from the container during delivery to the landfill, ” he said.

Upon entering the station, the trucks stop by the washing area to discharge the leachate.

The leachate is then diverted to the leachate treatment plant by underground pipe.

“Over 120 cubic metre of leachate is collected daily. Usually, up to 3% to 5% of the weight of the waste is leachate, ” said Hashanuddin.

The trucks would then head to the incoming weighbridge where their initial weight would be taken, before heading towards the hoppers to discard the waste.

Control room

Perched some floors above the hoppers and separated by a glass panel is the control room, from which movements inside the station are monitored.

Hashanuddin said the hoppers were equipped with CCTV cameras that provide live feed from the control room.

3 Rubbish trucks discard waste into hoppers at the transfer station for compaction before delivery to the landfill.3 Rubbish trucks discard waste into hoppers at the transfer station for compaction before delivery to the landfill.

“Personnel inside the control room will see if there is any bulk waste inside the hopper and they will remove it, if any, using the excavator.

“This is crucial because the bulk waste could damage the inner parts of the compactor, ” he said, adding that common bulk waste included furniture and wood.

Compaction

Once waste is discarded into the hoppers, it would be crushed and loaded into containers to be transported to the landfill.

Hashanuddin said there were four compactors on-site, three of which would work concurrently while one undergoes maintenance.

4 Containers with treated waste are ready to be sent to the landfill.4 Containers with treated waste are ready to be sent to the landfill.

“One hopper can accommodate up to 60 tonnes of waste at any given time, ” he said, adding that each compactor could produce 20 tonnes of compacted waste in 15 minutes.After discarding the waste into the hoppers, the trucks would proceed to the outgoing weighbridge to have their weight taken again before exiting the compound.

“We can find out how much waste is carried by a truck by calculating the difference between its initial and final weight, ” said Hashanuddin.

Effluent treatment

The leachate collected at the transfer station undergoes several stages of treatment before the final effluent is released into a river.

Hashanuddin said the station followed the guideline as stipulated by the Environmental Quality Act 1974 (Control of Pollution from Solid Waste Transfer Station and Landfill) Regulations, 2009.

“Raw leachate is normally quite acidic at pH4 or 5 and it must be treated to a pH between 6 and 9.

5 Alam Flora rubbish trucks waiting to be weighed at the outgoing weighbridge on the way out of the transfer station in Kepong.5 Alam Flora rubbish trucks waiting to be weighed at the outgoing weighbridge on the way out of the transfer station in Kepong.

“The BOD must be reduced to below 20ppm and the effluent must not contain more than 50ppm suspended solids, ” he said, adding that the concentration of suspended solids and ammonia must also not be more than 50ppm and 5ppm respectively.

(BOD stands for “biochemical oxygen demand” and referred to the amount of oxygen required by microorganisms to decompose organic matter. Higher BOD indicates a higher amount of organic matter. The ppm measure stands for “parts per million” and is a measure of the concentration of particulates in water.) 

The leachate collected from the washing area would be accumulated inside the collection tank at the leachate treatment plant (see graphic).

Dhes senior executive Zulhilmi Abdul Karim said the tank would filter out solids and the leachate would then enter the oil-skimmer tank to remove its oil content.

Hashanuddin says the pre-treatment facility processes waste before transporting them to the Bukit Tagar landfill.Hashanuddin says the pre-treatment facility processes waste before transporting them to the Bukit Tagar landfill.

“Due to its lower density, oil would float to the surface while the leachate will occupy the bottom half of the tank.

“A pipe at the bottom of the tank will then collect the leachate and channel it into the pH adjustment tank for further treatment, ” said Zulhilmi.

In the adjustment tank, sodium hydroxide is added to neutralise the acidic leachate, before it is fed into the coagulation tank.

“A coagulant called PAC polymer will be added to the tank. This substance will cause the organic matter and heavy metal present inside the leachate to bind, forming coagulates.

“The leachate will then be fed into the flocculation tank where the same process will be repeated to allow for bigger coagulates to form, ” he said.

Zulhilmi said the leachate would then enter the sludge thickener tank, where the coagulates would form sludge.

“The sludge will be collected and sent to a third-party vendor registered with the Department of Environment for disposal, ” he said.

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