Trade Effluent FAQs

If your company generates trade effluent intended for discharge into the public sewerage system, you will have to apply for a Written Approval (WA) from PUB. The WA specifies the conditions you have to comply with, if you wish to discharge trade effluent into the public sewerage system.

You can apply online for a WA through the GoBusiness Licensing Portal. For more details on the WA application procedures and requirements, please refer here.

You are responsible for ensuring your trade effluent is collected and disposed of responsibly. Discharging trade effluent into the public sewerage system without PUB’s approval constitutes a violation of the Sewerage, Drainage and Coastal Protection Act (SDCPA) and is illegal. As a business operator, you have a duty to ensure that any waste you generate is handled safely and in accordance with all environmental legislations.

All trade effluent discharged into the public sewerage system shall meet the water quality criteria specified in the SD(TE)R under the following categories:

a) Nature and type of trade effluent to be discharged;
b) Trade effluent to be free of certain substances; and
c) Maximum concentrations of certain substances.

For more details on the water quality requirements for trade effluent discharge into the public sewerage system, please refer to the latest Sewerage and Drainage (Trade Effluent) Regulations available on the Singapore Statutes Online website.

The trade effluent samples collected for analysis should be representative of the treatment quality from the pre-treatment plant.

Samples must be collected from the sampling tank or sump of the pre-treatment plant (see figure above). The pollutants or parameters to be tested depend on the type of trade activity. In general, trade premises should test for:

• Biochemical Oxygen Demand (BOD)
• Chemical Oxygen Demand (COD)
• Total Suspended Solids (TSS)

These tests help assess the chemical and biological load of the trade effluent.

Trade premises should also test for specific water quality parameters relevant to their industry. For example, an electroplating facility that carries out copper plating should test for heavy metals such as copper.

For the full list of parameters and discharge limits, please refer to the Requirements for Discharge of Trade Effluent into the Public Sewerage System.

You can send your samples to an accredited laboratory for analysis. For a list of accredited laboratories, please visit the Singapore Accreditation Council (SAC) website.

If you are unable to meet the water quality limits stipulated in the SD(TE)R, you can either:

• Install a wastewater treatment facility within your premises to pre-treat non-compliant trade effluent, ensuring that water quality parameters meet discharge limits and prohibited substances are removed before discharge into the public sewerage system; or
• Engage a licensed waste collector authorised by the National Environment Agency (NEA) to collect and dispose of your trade effluent off-site.

The handling of toxic industrial wastes is regulated by the Environmental Public Health Act (EPHA), governed by the NEA. Under the EPHA, you need to engage a licensed toxic waste collector to collect and dispose of your toxic waste off-site. You should not engage a general waste collector to collect your toxic industrial waste. You will need to properly account for all your waste generation. You may also be required to declare your waste disposal through NEA’s e-consignment system.

For more information on the proper handling of toxic industrial wastes, please refer to NEA’s website.

Trade premises that are unable to install a wastewater treatment plant (WWTP) (e.g. due to space constraints), or engage a licensed waste collector, to meet discharge limits for BOD or TSS may apply for the TEF scheme if their trade effluent contains BOD or TSS concentrations above 400 mg/L.

However, approval will not be granted if the trade effluent contains:

• BOD greater than 6,000 mg/L;
• TSS greater than 6,000 mg/L; or
• Chemical Oxygen Demand (COD) greater than 10,000 mg/L, or more than 3 times the BOD concentration (whichever is lower).

If you know of or suspect an accidental discharge or non-compliant trade effluent being discharged into the public sewerage system, please inform us immediately. This allows us to alert the water reclamation plants of any incoming non-compliant trade effluent, enabling them to take necessary action. You can contact us through PUB-ONE, our 24-hour hotline, at 1800-CALL-PUB (1800-2255-782).

Here are some practical tips to help prevent the accidental discharge of illegal trade effluent:

Housekeeping and Proper Storage of Chemicals

• Store and handle raw materials, wastes, chemicals and fuels properly to prevent them from entering sanitary drain lines, floor traps and sewers within your premises.
• If chemicals or industrial solvents are used within your premises, obtain Safety Data Sheets (SDS) from suppliers. These provide important information such as chemical composition and proper disposal methods for spent chemicals.
• Provide proper containment measures, such as metal trays or bund walls, around chemical and solvent storage areas to prevent accidental leakage or spillage into drain lines or the public sewerage system.
• Store materials such as grease, paints, detergents, metals and raw materials in suitable labelled containers. Outdoor storage containers should be covered with properly secured lids. Stockpiled materials should also be protected from rain by storing them indoors, under shelter, or beneath tarpaulins.

Process Monitoring

• Maintain an up-to-date sanitary drainage plan showing the locations and flow directions of all drains and sewers within your premises.
• Ensure proper maintenance of pre-treatment plants and water quality monitoring sensors (where installed) to keep them functioning effectively.
• Clearly demarcate discharge points for spent solvents and train workers on proper collection and disposal procedures using licensed waste collectors. When discharging trade effluent, ensure that it is connected to the correct system.
• Explore alternative materials or practices that may help reduce effluent contamination.

Maintenance Work

• Conduct maintenance work on equipment and vehicles in designated or covered areas where used water can be separately collected and disposed of. Use drip pans to contain leaks or spills during maintenance activities. Collected liquid waste should be disposed of by licensed waste collectors.

Emergency Preparedness and Response

• Keep spill kits or absorbent materials (e.g. granules or sawdust) readily available in areas where there is a risk of spills or leakage into the public sewerage system. Ensure employees know where these materials are kept and how to use them.
• Never wash spilled chemicals into sewers or drains. Use absorbent materials, spill kits, paper wipes or rags to clean up spills, and dispose of them as solid waste. Do not wash and reuse contaminated rags.

Educating Employees and Contractors

• Conduct regular briefings and in-house training for workers and contractors on the proper handling, disposal and discharge of liquid waste.

Maintenance Schedule

If your facility has a pre-treatment plant, a maintenance schedule is essential to ensure its proper operation and adequate treatment of trade effluent. Refer to the plant’s operation manuals or consult your vendor, contractor or consultant to develop a comprehensive inspection and maintenance schedule.

Here are some useful pointers:

• Keep proper records of all mechanical components used in the plant, such as pumps and stirrers.
• Implement a regular servicing schedule, including thorough equipment inspections and replacement of consumable parts.
• Maintain servicing and calibration records for all process instruments used in the plant.

Process Monitoring Schedule

A process monitoring schedule, together with a maintenance schedule, helps ensure that your treatment process is operating effectively.

Here are some useful pointers:

• Implement a regular schedule to collect trade effluent samples from the plant and verify compliance with discharge limits stipulated in the SD(TE)R. Commercially available analytical kits and sensors may be used to measure water quality parameters.
• Periodically send trade effluent samples to an accredited external laboratory for analysis.
• Maintain records of all test results, monitor process trends, and revise the monitoring schedule where necessary.

An oil interceptor is a device that separates oil and grease from trade effluent. Oil interceptors are important as they reduce the amount of oil and grease entering the public sewerage system, thereby minimising the risk of sewer blockages. The figure below illustrates a typical oil interceptor.

Here are some useful pointers:

i) Implement a Maintenance Schedule

Oil interceptors require regular maintenance to ensure effective treatment of trade effluent. Your maintenance schedule should include regular checks for:

• Excessive build-up of scum and debris that may be carried into the public sewerage system;
• Accumulation of oil stains on interceptor walls; and
• Sufficient water levels within the interceptor.

ii) Implement a Monitoring Schedule

You should implement a monitoring schedule to regularly check the quality of trade effluent discharged from the oil interceptor. Consider the following:

• Collect trade effluent samples from the interceptor outlet and send them to accredited laboratories for testing of “Oil-and-Grease (Total)” and “Oil-and-Grease (Hydrocarbon)”.
• If you operate a motor workshop or activities involving industrial solvents such as metal degreasers, you are also encouraged to send trade effluent samples for Gas Chromatographic Mass Spectrometry (GCMS) analysis to detect inflammable substances.

Use the laboratory test results to review and adjust your oil interceptor maintenance schedule where necessary.

iii) Clean the Oil Interceptor Regularly

Oil interceptors should be cleaned regularly. The recommended cleaning steps are illustrated in the figure below.

iv) Collection, Transportation and Disposal of Toxic Waste

The collection, transportation and disposal of toxic waste, including waste oil and spent solvents, are regulated under the Environmental Public Health (Toxic Industrial Waste) Regulations administered by the National Environment Agency (NEA). You should consult NEA for guidance on the proper collection, transportation and disposal of waste oil and spent solvents.

The discharge of effluent into the watercourse (e.g. open drains, canals and rivers) is regulated under the Environmental Protection and Management Act (EPMA) and the Environmental Protection and Management (Trade Effluent) Regulations. These are administered by the NEA.

For more information you may visit NEA’s website.

PUB aims to process all permit applications within 30 working days upon receiving all required documentation. This includes permits such as:

1. Written Approval for discharge of trade effluent into public sewerage system
   • For Written Approvals, the documentation required are as follows in the table below.

2. Permission to discharge TE exceeding BOD, COD or TSS limits (also known as Trade Effluent Fee (TEF) Scheme).

3. Permission to NEA-licensed General Waste Collectors (GWCs) to dispose effluent or organic sludge at Water Reclamation Plants.

Please ensure all supporting documentation is prepared and completed accurately to avoid processing delays.