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Eco-friendly engineered waste system

Brunei’s First-ever Eco-friendly Engineered Waste System Built by ST Engineering's Marine Sector

For almost a decade, the Brunei government faced rising social concerns and environmental pressures from rapidly filling dumpsites in the country. With dumpsites at distributed localities reaching the end of service life, increased attention had to be given to control pest infestation, leachate discharge, methane emissions and odour arising from these sites. These factors spurred the need for a new, systematic way of handling the waste.

The solution - implementing an Integrated Waste Management System (IWMS) to process the country’s waste which is increasing in tandem with the country’s development. Together with a Brunei consortium partner, QAF Limited, we won the bid by the Brunei Economic Development Board (BEDB) to design and build the IWMS. The system consists of an engineered landfill in Sungai Paku and a transfer station in Sungai Akar. Upon completion of the construction of the waste processing facilities, the site was immediately put into operation to ease the strain placed on the other existing dumpsites across the country.

The contemporary waste management system can process and hold up to four (4) million tonnes of rubbish via its engineered landfill. While the contract requires us to provide Operation and Maintenance for three (3) years, we were able to flexibly adapt to BEDB’s needs, servicing the client for a total of four and a half (4½) years. Of which, we were able to manage complexities arising from early operations while concurrently undertaking construction within the same site during the early start of six (6) months. Following transition procedures and training, the project was recently handed over to the Brunei government on March 2016.

Sungai Paku Engineered Landfill

The engineered landfill is a fully integrated eco-solution which also takes care of the downstream treatment of gaseous and liquid by-products. Landfill gas flare help reduce greenhouse gas emissions, while leachate treatment plant (capable of also simultaneously handling restaurant grease and septic sludge) removes toxicity in liquid effluents prior to responsible discharge in water courses.

Unlike traditional dumpsites where the surrounding land can be contaminated with leachate, each cell in the engineered landfill is lined with an impermeable membrane to ensure waste is securely contained. Leachate is an unavoidable phenomenon where rainwater percolates downwards through waste stored in the landfill and eventually seep into the ground. By putting in place a gravity pipe system to collect these from within the membrane liners, the leachate is then directed safely into the treatment facility where the liquid is removed of its toxicity and closely monitored through the stages.

Not only do we enforce controlled areas for tipping operations, a layer of compacted soil is always spread by landfill machineries to cover the waste at the end of each day’s operation. This stringent discipline goes a long way in preventing the undesirable spread of leachate and odour into the surroundings. In addition, a perimeter buffer zone lined with greenery serves as a natural screen to prevent odour from travelling beyond the landfill. Our engineers have also designed and constructed a 16m-wide creek diversion at the northern perimeter to improve drainage capacity of the existing water courses cutting across the landfill, thereby mitigating effects of construction on the selected site responsibly.

Almost all landfills release methane, a highly flammable gas carrying distinctive odour released during decomposition. Landfills can therefore potentially be turned into a source of complaints by locals and workers alike if not properly managed. With stringent protocols put in place and standards to meet, we employ reliable technological solutions as well as constant community stakeholder engagement for safe complaint-free operations. The gas flare at the landfill maintains methane levels at the accepted US Environmental Protection Agency (EPA) standards by burning off excess gas. As methane is considered a greenhouse gas,  any harmful impact on the environment and climate change is therefore also reduced.

At the landfill’s construction and demolition resource recovery facility, discarded construction materials are broken down into stone aggregates and repurposed for paving internal access roads into the waste-filled landfill cells, thereby creating self-sustainability in landfill operations.

In January 2015, guests from Japanese integrated trading and investment business conglomerate, Marubeni, and Brunei Branch of US-based oil and gas EPCI company, McDermott, visited the Sungai Paku Engineered Landfill. They were impressed by the minimal odour from the rubbish, and its clean and tidy surroundings and commented that it was a notable and positive improvement from the sanitary landfill solutions in the region. Much of Sungai Paku used to be a wasteland after the sand miners extracted most of what the land had to offer. However, the engineered landfill brought new use to the land.

Sungai Akar Transfer Station

The now defunct Sungai Akar dumpsite had to be closed due to full capacity but was given a fresh lease of life after undergoing a land rehabilitation process, as commissioned by the BEDB. Situated in close proximity to the city, the land plot now houses our transfer station facility which receives 500 tonnes per day (tpd) of municipal and commercial waste from Brunei’s capital before transporting to the engineered landfill.

Compacting rubbish tipped from six (6) to eight (8) rear-end loader trucks into a single purpose-built trailer, waste is consolidated and compressed before our fleet of prime movers reliably and hygienically transports these trailers across to the engineered landfill over 70km away from the city. By maximising the throughput for each trip by means of mechanical compaction, the overall number of trips made between the transfer station and the landfill is thus reduced, making the process more cost and environmentally efficient. Further streamlining of operations includes the removal of recyclable materials from incoming waste stream at the Material Recovery Facility housed inside the same compound as the transfer station. Our workers systematically identify and sort recovered materials. Of which, they are subsequently baled for repurposing. In the long run, it minimises the amount of waste entering the landfill and prolongs the lifespan of the landfill.

Solar panels installed at the rooftops of the transfer station help to defray the facility’s operating costs by harnessing recoverable energy for its administrative operations. With a light environmental footprint to the immediate surroundings, the transfer station is able to serve its purpose whilst sharing its land with Sungai Akar’s recreational park.

The Impact

The IWMS is our maiden environmental project which includes both aspects of Design-Build (DB) and Operation & Maintenance (O&M) services. Not only was the initial phases of the project completed six (6) months ahead of schedule, the O&M services were extended for an additional year to suit the needs of the Brunei government. To ensure the continuation of IWMS operations after the handover, we provided training to local government representatives in the form of attachments and formal trainings.

Our environmental engineering solutions enabled the community nearby Sungai Akar and Sungai Paku to co-exist amicably with our solid waste management plant. This was made possible through the efforts our employees, who constantly engaged the local communities to consolidate feedback on effectiveness of operations and its impact to the surroundings. Through such thorough and insightful interactions, we were able to build rapport and foster ties on the sidelines while construction and operation of the city’s transfer station was fulfilled. The abandoned sand-mining quarry at Sungai Paku was also given a new purpose as an environmentally-friendly, world-class landfill. This integrated approach to waste brings out the best of various engineering technologies we can provide, while meeting the needs of Bruneians sustainably.