Singapore has a robust, diversified and sustainable water supply from four sources, known as the ‘Four National Taps’: water from local catchment, imported water, NEWater and desalinated water. As Singapore’s economy and population grow, water demand is projected to nearly double by 2065. NEWater, our third tap which is recycled from used water, plays a crucial role in meeting this demand and enhancing Singapore’s water security amid climate change.

2     PUB monitors trade effluent discharge into public sewers to ensure that the used water quality meets NEWater production standards. Used water is collected from households and trade premises and conveyed via an extensive sewerage network system¹ for biological treatment at PUB’s Water Reclamation Plants (WRP). A portion of this treated used water undergoes further purification at our NEWater factories to produce NEWater. If trade effluent² contains prohibited substances such as selected volatile organic compounds or excessive concentrations of regulated substances like heavy metals, it can disrupt the treatment processes at PUB’s WRPs and downstream NEWater production. In addition, illegal discharges can endanger the health and safety of workers maintaining the sewerage system.

Prevention and deterrence

3     PUB reviews the chemicals used, and the quantity and quality of discharge from trade premises before granting approval for trade effluent discharge. This process protects the public sewerage infrastructure, operations at our WRPs and NEWater production from hazardous or toxic discharge. PUB will also assess whether these premises have adequate wastewater treatment facilities or have engaged licensed toxic industrial waste collectors for waste removal.

4     There is round the clock monitoring of our sewers through an extensive network of online used water quality sensors that provide real-time data. This includes more than 150 microbial electrochemical sensors (MES) to monitor heavy metals, cyanide and other toxic chemicals and over 100 volatile organic compound (VOC) remote monitoring units for detecting prohibited organic compounds. Should abnormalities be detected, PUB promptly deploys officers to address illegal discharges at their source and mitigate any impact on the used water treatment process.

Regulation and enforcement

5     PUB has put in place a suite of measures to effectively deter illegal discharges into the sewerage system. The first step is the rigorous vetting process before approvals are granted for trade effluent discharge. Second, we conduct regular inspections and monitoring throughout the network. When illegal discharges are detected, PUB may issue stop work orders, revoke approvals for trade effluent discharge, and impose penalties on offenders. While most companies have acted responsibly, there are still some irresponsible offenders, including recalcitrant ones, whose actions have threatened our used water system. From 2017 to 2023, PUB prosecuted 90 offenders for 295 trade effluent-related offences in court. On average, about 70% of the offenders prosecuted every year are repeat offenders.

6     The Sewerage and Drainage Act (SDA) and the Sewerage and Drainage (Trade Effluent) Regulations (TER) are the main legislative tools used to regulate trade effluent discharge and enforce compliance among trade premises. These legislations are regularly reviewed to strengthen deterrence against illegal discharges, keeping pace with industrial trade changes and new chemicals used in emerging or technologically advanced industries.

7     The recently passed Sewerage and Drainage (Amendment) Bill on 11 November 2024³ includes increasing maximum penalties and introducing mandatory minimum penalties (see Annex) to reflect the severe consequences of illegal discharges on our water supply and NEWater production. In addition, General Waste Collectors (GWCs) that are permitted by PUB to dispose of certain waste at WRPs will be required to install Global Positioning System (GPS) devices on their waste tankers. This will allow PUB to promptly investigate illegal disposal of waste (e.g. toxic industrial waste) that is not permitted to go into sewers and follow up with the necessary enforcement action.

8     The TER which was gazetted on 1 July 2024 will enhance regulatory controls on the discharge of substances into public sewerage system. The key amendments include expanding the list of prohibited compounds to include compounds that had or may cause disruptions to NEWater production and stipulating that trade premises must not tamper with pre-treatment plants, as well as monitoring and control devices. Trade premises are also required to inform PUB of any changes that will affect the amount or nature of trade effluent discharged. They need to furnish documentation for a period of up to 12 months prior to the date of PUB’s request for record submission. This documentation may include inspection or maintenance records of wastewater pre-treatment plants, laboratory results of trade effluent samples and disposal records of any toxic industrial waste.

Capability development

9     PUB continually seeks to harness technology to enhance its monitoring and surveillance capabilities. Besides scanning for new off-the-shelf technologies to improve work efficiency and effectiveness, PUB also collaborates with research institutions and industries to develop robotic solutions and sensor technologies when commercial options are unavailable. Such collaboration efforts have resulted in technologies that facilitate source tracing work, enabling PUB officers to identify factories suspected of illegal discharge. Examples of technologies developed through PUB’s partnerships with our stakeholders, and successfully implemented, include the microbial electrochemical sensors system and the volatile organic compound remote monitoring unit.

Stakeholder engagement

10     PUB adopts a proactive approach in engaging key stakeholders such as factory owners and trade associations through regular industry-wide dialogue sessions to raise awareness on the importance of discharging trade effluent that complies with discharge limits, provide guidance on regulatory requirements and share best practices on managing trade effluent discharge.

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Footnotes:
[1] More info on Singapore’s public sewerage system: https://www.pub.gov.sg/Professionals/Requirements/Used-Water  
[2] Trade effluent refers to any liquid, including particles of matter and other substances suspended in the liquid, that is the outflow from any trade premise, business, or manufacturer, or arising from any engineering or construction works.
[3] Refer to PUB’s media factsheet: https://www.pub.gov.sg/Resources/News-Room/PressReleases/2024/11/Amendments-to-Sewerage-and-Drainage-Act 

Annex: Penalties for illegal discharge into the sewerage system