Industrial facilities discharging process wastewater into Singapore’s public sewer need PUB Written Approval (WA) before any connection or discharge begins. Facilities whose effluent exceeds 400 mg/L BOD or TSS also require Trade Effluent Fee (TEF) permission, a conditional route with fee bands and upper concentration caps. The practical next step is to begin the application through the GoBusiness Licensing Portal and commission accredited laboratory testing early, since results feed directly into the WA documentation package.
TL;DR:
- PUB aims to review a complete application within 30 working days; include accredited lab results, process diagrams, discharge estimates, and accessible sampling point evidence.
- TEF fees follow concentration bands; approval stops above 6,000 mg/L BOD or TSS, or COD at 10,000 mg/L or three times BOD, whichever is lower.
- After approval, maintain treatment equipment and monitoring instruments, retain calibration and maintenance records, and report changes in chemistry, volume, or effluent quality within 14 days.
- A second or later conviction can bring fines up to $30,000 and continuing penalties of $1,000 per day; PUB can also order discharge to stop.
- PUB inspectors check sampling points onsite; inaccessible or unrepresentative locations, missing documents, and unclear evidence can trigger rework, refusal, or revocation.
Table of Contents
- Who needs a Written Approval and when to apply
- Discharge standards and prohibited substances under the regulations
- Trade Effluent Fee permission: when it applies and what it costs
- What PUB requires in a Written Approval application
- Monitoring, maintenance and change notifications after approval
- Penalties, enforcement powers and common reasons for refusal
- Treating written approval as an ongoing compliance program
- How we support PUB Written Approval and industrial compliance submissions
- FAQ
- Sources
Who needs a Written Approval and when to apply
Trade effluent covers any liquid waste discharged from industrial, trade or business premises, distinct from ordinary domestic sewage. It typically includes wastewater from manufacturing lines, metal plating baths, food processing operations, non-toilet medical wastewater, and process liquids generated during construction works. If your premises generates any of these streams and connects to the public sewer, PUB Written Approval must be secured before discharge begins.
- WA must be obtained before connecting to or discharging into the public sewerage system, not after.
- Any process change affecting effluent quantity or quality must be reported to PUB in writing within 14 days.
- PUB requires the complete documentation set before processing moves forward.
Facilities planning a new production line or a change in chemical inputs should start this process well ahead of the target operating date.
Discharge standards and prohibited substances under the regulations
The Sewerage and Drainage (Trade Effluent) Regulations set the baseline concentration limits that determine whether a facility can discharge under standard conditions or needs TEF permission.
400 mg/L is the baseline threshold for BOD and TSS under the Sewerage and Drainage (Trade Effluent) Regulations, beyond which prior PUB permission and fee assessment apply.
- Discharges exceeding 400 mg/L BOD or TSS, or 600 mg/L COD, require prior PUB permission under the TEF scheme.
- COD must not exceed 10,000 mg/L or three times the BOD value, whichever limit is lower.
- The Regulations prohibit or restrict substances that endanger sewer worker safety or disrupt downstream treatment processes, and PUB retains the authority to refuse permission outright.
Fee schedules and detailed concentration bands are set out in the Regulations and its Amendments, so facilities with variable process chemistry should check the current schedule before estimating costs.
Trade Effluent Fee permission: when it applies and what it costs
TEF permission exists for facilities whose effluent strength sits above the 400 mg/L baseline but within the permissible upper range. Fees are billed according to concentration bands under the Sewerage and Drainage (Trade Effluent) Regulations, and late payments attract a 1% surcharge on the outstanding balance.
- TEF permission applies once BOD or TSS exceeds 400 mg/L, with fees scaled to the concentration band the discharge falls into.
- Approval is unavailable above the absolute caps: BOD or TSS beyond 6,000 mg/L, or COD beyond 10,000 mg/L or three times BOD.
- PUB may attach conditions, require a performance bond or security deposit, and revoke permission if the discharge becomes hazardous or interferes with sewer treatment operations.
Facilities operating near these upper caps should budget for pretreatment upgrades rather than assume TEF permission will be granted indefinitely.
What PUB requires in a Written Approval application
A complete WA submission moves faster through PUB’s review, and PUB’s Trade Effluent guidance outlines the documentation expected for every application.
- Company details confirming the legal entity operating at the premises.
- Process flow diagram describing production steps that generate effluent.
- Layout drawings and process and instrumentation diagrams showing piping, treatment units and sanitary connections.
- A written description of effluent sources and estimated monthly discharge quantities.
- Accredited laboratory test results covering the parameters specified in the Regulations.
- Photographs and a clear description of the representative sampling point, confirming it is accessible for routine inspection.
Pro Tip: Submit your process and instrumentation diagrams and sampling point photos early rather than waiting for a PUB query, since incomplete submissions can delay processing beyond the usual 30 working days.
PUB inspectors physically check sampling points during site visits, so a point buried behind equipment or lacking clear labeling invites a request for rework before the file progresses.
Monitoring, maintenance and change notifications after approval
A WA is a live condition set, not a one-time clearance, and ongoing compliance depends on disciplined record-keeping.
- Keep pretreatment systems, including grease traps, oil interceptors and any on-site wastewater treatment plant, in good working order with documented maintenance logs.
- Run a regular sampling and monitoring program, and keep pH monitors and automatic shut-off penstocks properly maintained.
- Retain calibration and maintenance records in a format ready for PUB’s periodic audits.
- Notify PUB in writing within 14 days of any change to process chemistry, production volume or effluent characteristics that could affect discharge quality.
Pro Tip: Keep maintenance records available for inspection and ensure they accurately document upkeep and monitoring.
Renewal of a WA typically follows the same documentation pattern as the initial application, with updated lab results and an account of any operational changes since the last approval.
Penalties, enforcement powers and common reasons for refusal
Under the 2025 Amendment Regulations, a first conviction for breaching core trade effluent requirements can carry a fine up to $15,000 and imprisonment up to three months, with a continuing-offence fine of $500 per day.
A second or subsequent conviction raises the fine ceiling to $30,000, with continuing daily fines up to $1,000, under the 2025 Amendment Regulations. Some minor contraventions, such as failing to install a proper sampling point, are capped at $5,000 with a $500 daily continuing fine.
- PUB can issue stop-discharge orders, mandate remediation steps, or revoke a WA outright when discharge poses a hazard.
- Common causes for refusal or revocation include incomplete application documentation and inaccessible or unrepresentative sampling points.
- Keep PUB informed of relevant process changes and maintain pretreatment equipment.
Treating written approval as an ongoing compliance program
Our view is that operators should treat Written Approval as an ongoing compliance responsibility, rather than paperwork to file once and forget. Maintaining instruments and keeping maintenance logs current can help prevent documentation gaps during renewals.
Starting the application early, with P&IDs and sampling point evidence prepared before PUB asks for them, avoids the iterative clarification rounds that stretch out the standard 30 working day review window. For facilities with complex effluent chemistry or limited in-house compliance staff, an experienced authority-submission consultant may help organize the application.
— Aman
How we support PUB Written Approval and industrial compliance submissions
We prepare engineering documentation for authority submission packages.
- We assemble process descriptions, layout drawings and sampling point documentation into a package for submission.
- We can coordinate with statutory boards on behalf of industrial clients managing authority approvals.
- We advise on compliance when effluent chemistry is complex or in-house technical capacity is limited.
Facilities planning a new production line, a change in process chemistry, or a WA renewal can engage us to help prepare their application, which PUB reviews based on the documentation submitted. Visit our services page for an initial consultation and a document checklist tailored to your facility.
FAQ
What is the Sewerage and Drainage Act (SDA)?
The Sewerage and Drainage Act is the Singapore statute governing sewerage infrastructure, drainage systems and trade effluent discharge, with detailed obligations set out in its subsidiary Sewerage and Drainage (Trade Effluent) Regulations. It gives PUB the authority to require Written Approval before any trade effluent enters the public sewer.
What is a trade effluent licence?
In Singapore, the equivalent of a trade effluent licence is PUB’s Written Approval (WA), which authorizes an industrial premises to discharge trade effluent into the public sewerage system. Facilities with higher-strength effluent also need separate Trade Effluent Fee permission on top of the WA.
What are the effluent discharge standards in Singapore?
The baseline limit for BOD and TSS is 400 mg/L, above which TEF permission and fees apply, while COD must stay below 10,000 mg/L or three times the BOD value, whichever is lower. Absolute caps of 6,000 mg/L for BOD and TSS mark the point beyond which approval is not available at all.
Does Singapore have a sewer system?
Yes, Singapore operates a public sewerage network that collects both domestic sewage and industrial trade effluent, feeding into water reclamation infrastructure managed by PUB. Industrial facilities connecting to this network must hold a valid Written Approval before any discharge begins.
How long does a Written Approval application take to process?
PUB aims to process a complete Written Approval application within approximately 30 working days once all required documents and accredited lab results are submitted. Incomplete applications or unclear sampling point documentation commonly extend this timeline.
Sources
Recommended
- Guide to Industrial Change Applications in Singapore
- Get All Four PUB Drainage Clearances First Time for Singapore QPs