Further Information
- CP 100: 2004 Code of Practice for Hazardous Waste Management
Excerpted from Workplace Safety and Health Guidelines – Laboratory Handling Chemicals
Waste Segregation, and Storage
In a laboratory, chemical wastes are usually segregated on-site into appropriate waste bottles or carboys, before collection by a licensed TIW collector. Proper segregation of waste will allow for maximum treatment and recovery by the TIW collector.
Recommended Practice for Segregating Laboratory Waste
- Separate chemical wastes into different types, for example, waste organic solvents, aqueous waste, wastes that are incompatible with one another.
- Further separate waste organic solvents (i.e., hydrocarbon-based) into halogenated and non-halogenated solvent waste. Non-halogenated organic solvent waste can either be recycled or burnt for energy recovery, while halogenated solvent organic waste must be specially incinerated to minimize the formation and release of dioxins.
- Separate aqueous waste containing toxic compounds from waste organic solvent. Only innocuous aqueous waste (such as sodium chloride solution) may be poured down the wash basin.
- Segregate the following and package separately:
- strong oxidizers from organics;
- acids from bases;
- heavy metal solutions from salts;
- chemical carcinogens;
- cyanide-containing materials;
- peroxide-forming chemical from combustible materials and mineral acids; and
- water-reactive chemicals from moisture, water and other chemicals.
- Collect waste elemental mercury separately for reclamation.
- Collect chemically contaminated solid waste and broken glass in plastic containers or plastic-lined cardboard. Broken glass that is contaminated with chemicals is usually not suitable for recycling.
Recommended Practice for Storage and Handling of Chemical Waste
- Ensure that chemical reactions are complete before discarding the chemical waste. This is because incomplete reactions may continue inside the waste container, leading to pressure build-up within the container.
- Store all chemical waste in durable, leak-proof containers (usually bottles or carboys) that are in good condition and compatible with their contents. Chemical waste in containers that are bulging, rusted, cracked, and/ or have improper or missing caps must be transferred to an appropriate container in good condition for storage. Refer to guidance on Container Compatibility. Table C.1 (Annex C) of Singapore Standard CP 100: 2004 Code of Practice on Hazardous Waste Management provides further details on the chemical compatibility of common containers with different hazardous waste types.
- Establish and implement SWPs for all chemical waste handling work.
- Work under the fumehood when transferring chemical waste into a container.
- Use the appropriate PPE when handling chemical waste, for example, impervious gloves, face shield, safety goggles, chemical-resistant apron and safety boots.
- Label each waste container so that its contents can be easily identified, and label it “HAZARDOUS WASTE” if the contents are flammable, corrosive, toxic or reactive. At minimum, the label should state the:
- waste type;
- volume of the waste;
- its key chemical constituents;
- purity of the waste (if available);
- date of disposal;
- associated safety and health hazards; and
- the recommended PPE if necessary.
- If the waste container is already partially filled, conduct a RA and check for chemical compatibility before pouring in more waste. Never mix one waste with another waste in the same container unless the constituents in both waste sources are known. If necessary, conduct laboratory testing to ascertain the hazardous substances in each source before combining waste from different sources. Refer to Section 3.1.2 on Chemical Compatibility and in particular the chemical compatibility matrix given in Table C.3 (Annex C) of Singapore Standard CP 100: 2004 Code of Practice on Hazardous Waste Management.
- Do not fill waste containers to their brims – fill up to three-quarters of the container’s maximum capacity. This leaves sufficient headspace at the top of each waste container to cater for temperature changes, increased vaporization and potential pressure build-up.
- Cap all waste containers prior to storage. Keep all waste containers closed except when adding to or removing from the container.
- Store chemical waste in a designated area away from normal laboratory operations. Never place waste containers in common areas like hallways or corridors, or near wash basins and floor drainage points.
- Ideally, store chemical waste in a dedicated chemical storage cabinet. Incompatible wastes should be properly segregated to prevent inadvertent mixing, which can result in undesirable chemical reactions. Use a physical barrier (e.g., a separate cabinet compartment, a different leak proof shelf, or secondary containment such as a plastic container or tray) to separate incompatible wastes. Lock the storage cabinet to prevent unauthorized access.
- If waste is stored in a central storage room, the room should be provided with appropriate ventilation, fire suppression facilities or equipment (e.g., an automatic water sprinkler system and fire extinguishers), emergency equipment (e.g., a respirator and spill kit) as well as containment dikes to avoid sewer contamination in the event of spills.
Waste Disposal
The laboratory officer in charge of chemical waste disposal is responsible for engaging a licensed TIW collector and communicating relevant waste disposal requirements to contractors. The updated list of TIW contractors licensed by the National Environment Agency (NEA) under the Environmental Public Health (TIW) Regulations may be found at NEA’s website (www.nea.gov.sg) under Anti-Pollution & Radiation Protection > Chemical Pollution > Toxic Industrial Waste.
Recommended Practice for Disposing of Chemical Waste
- Never pour liquid chemical waste down the drain or throw solid chemical waste into the trash bin unless the waste is innocuous and safe for disposal as normal refuse.
- Do not treat hazardous waste on-site unless the laboratory has special facilities to do so.
- Seek the services of a licensed TIW collector who can assist with and ensure proper treatment and disposal of hazardous chemical waste.
- Containers used for the storage of chemicals are to be regarded as TIW.
- Return all gas cylinders to the industrial gas supplier/ distributor/ vendor.
- Use appropriate mechanical lifting or handling devices to aid in the transfer of heavy waste containers and gas cylinders.
- Record the details of the waste disposal (e.g., description of the waste, characterization analyses where applicable, volume or weight of the waste, date of disposal, TIW contractor responsible for the disposal) in the waste register.
Note that chemical waste (whether in solid or liquid form) or any materials contaminated by chemical waste should never be deposited into bins meant for general waste as this may lead to uncontrolled reactions and/ or severely injure the janitor/ cleaner in-charge of clearing the general waste.