Moving wastewater treatment underground

Despite space constraints, wastewater treatment plants are crucial in ensuring that there is enough of the vital finite resource for all. But the challenge of constructing sprawling treatment facilities with limited land has led to some innovative solutions – which in the case of Pantai 2 Regional Sewage Treatment Plant, was to bring underground.

Built by the government of Malaysia, Pantai 2 Regional Sewage Treatment Plant (P2RSTP) is a state-of-the-art mechanised underground facility with public amenities close to the prime area of Kuala Lumpur City Centre.

Its 6,700 hectares of sewage catchment include high density areas such as Bangsar, Kerinchi, Bandar Baru Sentul, Bukit Kiara and parts of Petaling Jaya, as well as Eco City, Mid Valley, and KL Sentral, the largest transit hub in Malaysia.

With an ultimate design capacity of 320 million litres of treated effluent per day for a population of 1.423 million, the project faced numerous challenges when building the underground plant, including addressing the issues housing and sustainable living for residents in the apartments constructed around the plant under the Government’s Housing Programme, among others.

Water & Wastewater Asia had the chance to sit down with Ir. Mohamed Haniffa Hj Abdul Hamid, Chief Operating Officer of IWK, to learn more about the innovative Pantai 2 RSTP.

Ir. Mohamed Haniffa Hj Abdul Hamid, Chief Operating Officer of IWK

This article, a first of two parts, will focus on the challenges faced when moving an entire sewage treatment plant underground.

Optimising land

Though Malaysia itself is a sprawling country, the capital city, Kuala Lumpur, by contrast, is constrained by finite land that presents a number of issues for development and expansions, among other challenges.

“There is also a growing need to provide for Green Lung space, community centres for the community to live aligned with the Government aspiration to promote sustainable living,” Haniffa explained. “Therefore, optimising the land for the dual purpose of serving community needs and sewage treatment was paramount.”

Pantai 2 RSTP is located close to the prime area of Kuala Lumpur City Centre

With that in mind, the government embarked on a project that sought to upgrade an existing aerated lagoon (AL) to an advanced underground mechanised sewage treatment plant able to serve more than a million residents while also reducing the footprint required. From there, the vacant land was transformed into an attractive space that would serve as the neighbourhood community centre promoting sustainable living.

“During the development planning, part of Pantai 2 RSTP was planned to be an underground facility to free the ground level for open space, now known as the Pantai Eco Park,” Haniffa added. “Now the 12-hectare Pantai Eco Park comes with various facilities, which includes the community centre, jogging track, football and futsal courts, and even courts for badminton, basketball and volleyball, on top of open spaces that can be used for other recreational activities.”

But allowing members of the public in an area also occupied by a sewage treatment plant presented completely unique problems of its own. To address the issues, the area was fashioned in such a way, members of the public would not be able to cross from the open space, the treatment facility guarded with security fences and surveillance services running 24 hours a day, 365 days a year.

In optimising land, the wastewater treatment facilities were moved underground

“Both Pantai 2 RSTP and Pantai Eco Park were designed as two independent facilities with separate controlled entry access. Both facilities are also secured by security fencing to avoid unauthorised trespassers from one facility to another,” Haniffa expounded.

“Additionally, the Pantai 2 RSTP site was designed and equipped with photo beam detector systems located at 17 zones inside the plant compound and is also surrounded by closed-circuit television (CCTV) units. Any trespasser will also be detected by the perimeter intrusion detection system (PIDS), where the alarm signals will be connected directly to the cameras which are able to position and capture the image of the trespasserautomatically. The security guard will then respond to the alarm and conduct an inspection immediately to address potential security threats.”

Moving wastewater treatment underground

For Pantai 2 RSTP, the main challenge was not running an underground facility, but constructing a new underground plant on the site of an existing sewage treatment plant that was still in operation was.

“Key tasks in executing this mega project included diversion and temporary treatment for the site planning,” Haniffa revealed. “Traffic movements, working space, material storage, odour, dust pollution, as well as community engagement were all very challenging.”

And that was just during the construction, even before operations were fully moved below ground level – operations that include the Advanced Anaerobic-Anoxic-Oxic (A2O) process in order to ensure that effluent discharged from the plant is of the quality prescribed in the Environmental Quality (Sewage) Regulations 2009.

“On top of construction difficulty, dealing with increased building cost was also one of the major challenges. And after that, the post construction challenges were – and still are – the health and safety related issues in regards to the workers in the underground facility,” Haniffa continued.

“They are exposed to obnoxious gases generated from the sewage treatment such as methane (CH4), carbon dioxide (CO2), and hydrogen sulphide (H2S), and these represent potentially serious health and safety threats to the workers underground if the ventilation systems fail to circulate fresh air into the plant, making it of paramount importance.

Emergency protocol, such as response and evacuation of workers underground also had to be planned carefully. Moreover, other major challenges included space limitation and obstruction during maintenance work especially in situation which involve the manoeuvring of equipment that is big and bulky.”

But the challenges only served to heighten the level of innovative solutions found in Pantai 2 RSTP. “Solutions to the challenges we faced include covering the odour-generating sources to contain the obnoxious gases and extracting the gases for treatment at the odour scrubber system, ventilation systems were incorporated, and the emergency escape route was meticulously planned out and proper emergency response plans were provided as well,” Haniffa said.