Guidelines for Safe Collection and Storage of Hazardous Waste

These hazardous waste storage guidelines provide guidance on the type and suitability of containers that can be used to collect hazardous waste, how hazardous waste containers are identified and color-coded, the design and management of hazardous waste storage areas, and the provision and use of materials for cleaning up hazardous waste spillages.

Improper hazardous waste storage may result in serious incidents, such as fire & explosions, contamination of land, or exposure of persons to hazardous materials, with significant liabilities for the company. Hazardous waste may be in the form of a liquid, a gas, or a solid. The waste may be generated continuously from a process plant or sporadically from a batch production activity.  To manage hazardous waste efficiently, waste producers should select the most appropriate way to collect and store the waste so it can be prepared for treatment and disposal.

Collection and Intermediate Storage of Hazardous Waste

Hazardous waste can be collected and immediately stored in a variety of containers or vessels, such as Intermediate Bulk Containers (IBCs), skips, drums, kegs, bottles, boxes, sacks, and bags. Bulk liquid wastes can be stored in fixed or de-mountable ISO tanks.  To select the most appropriate storage option, it is necessary to consider the following:

  • the type and nature of the hazardous waste;
  • how much hazardous waste will be generated;
  • how the hazardous waste will be transported;
  • which disposal method will be used.

Hazardous wastes should only be stored in tanks or containers made from compatible materials. For example, hazardous wastes with a pH of less than three should not be stored in mild steel tanks or drums unless they have been lined with an appropriate material such as glass or plastic.  Furthermore, incompatible wastes should not be collected in the same location.

Containers should be placed away from busy thoroughfares, and systems should be developed so they can be transferred safely to a storage facility.  Spill kits should be provided in close proximity to all waste collection areas.

If it is intended to transport the waste, the container should be specified accordingly. The container should also allow the waste to be processed directly by the waste management contractor.  For example, most hazardous waste incinerators can only process solid wastes that can fit onto standard pallets or into 205-liter (55-gallon) drums.  If larger containers are used, the waste may need to be removed and placed on pallets or in drums before it can be processed.  This may add cost and has safety implications.

Whenever bulk liquid wastes are stored in tanks that are used for a variety of duties, documented systems should be implemented to ensure that incompatible materials are not allowed to mix.

If a large volume of liquid waste is generated continuously, it should be pumped directly to a fixed storage tank. Fixed tanks used for hazardous wastes should be designed to the same standards required for hazardous materials. In some circumstances, it may be appropriate to use de-mountable ISO tanks to store bulk liquids as they allow waste to be transported directly without needing it to be pumped into a road tanker.  If road tankers or ISO tanks are used to store or transport hazardous wastes, checks should be made to ensure that the barrel, tank connections, and seals are compatible with the waste.

Specifying Containers for the Storage of Hazardous Waste

The United Nations (UN) makes recommendations concerning the specification of containers that should be used for the transport of “dangerous” substances, which include hazardous wastes.  They establish design specifications for the manufacture and testing of containers and provide conditions for the use of containers. Recommendations are made for many different types of containers, including IBCs, drums, boxes, and bags.

If a container meets all the UN recommendations, manufacturers are entitled to mark them with the UN symbol, or, in the case of metal containers, the letters “UN” can be stamped.

Whenever possible, waste producers should use UN-approved containers for the storage and transport of hazardous wastes.  However, it should be remembered that containers are UN-approved at the time of manufacture, and these markings do not necessarily imply conformity upon damage or reuse.

Liquid Waste Containers

Open-top containers are not suitable for the storage of liquid wastes.  If 205 liters (55 gallons) of drums are used, they should have “bung” tops.  “Clip-top” containers, smaller than 205 liters (55 gallons), should only be used if they have adequate seals on the lids, and seal materials should be compatible with the waste.

If liquid waste is placed into a sealed container, the container should be sufficient to withstand any pressure increases caused by environmental changes (temperature and pressure).

Clinical Waste Containers

If clinical waste is to be incinerated, one-way cardboard burn-boxes with internal plastic liners should be used. This makes the disposal process more secure. If plastic bags alone are used, they should have a minimum gauge of 225 (55m). The bags should be placed in a rigid reusable container when they are transported.

If clinical waste is to be autoclaved, plastic bags with a minimum gauge of 225 (55m) should be used. The bags should be placed in a rigid reusable container when they are transported. Autoclave tape or another indicator should be applied to the bags showing when the bags were processed.

Sharps waste should be placed in robust, UN-approved sharps containers. Sharps containers should not be overfilled, or it will not be possible to close containers securely. Sharps containers should not be placed in clinical waste bags or other waste containers. If a container becomes damaged, it should be placed in a larger undamaged one, and the outer container should be appropriately labeled.

Asbestos Waste Containers

Asbestos waste should be placed in strong (500 gauge or 110m) color-coded polythene bags (double bagged) or polythene sheeting for larger items. Air should be excluded from bags as far as possible before sealing. If sharp or heavy items are present that could pierce the plastic, a more rigid container, such as a drum, should be used.

Containers for Bioengineering Wastes

Bioengineering waste should be separated from the non-hazardous waste and stored in UN-approved containers that are puncture and leakproof. The containers should be suitable for thermal treatment, such as autoclaving or incineration.

Management of Hazardous Waste Containers

Inspection of Hazardous Waste Containers

Before any container is used, it should be inspected to check that it has the UN mark. It should also be checked to ensure that it is undamaged and uncontaminated. If a steel drum is used, it should not be corroded. Any container that shows signs of being unfit for purpose should not be used. Poor-quality containers should not be used for waste as a means of disposing of the container.

Steel drums should be inspected with care as many are reconditioned using a heating process that destroys seals and renders the containers unsuitable for the storage of liquid wastes. If reconditioned drums are used, they should be in good condition and not be used for liquids.

Labeling Before Transport of Hazardous Waste

Waste producers are best placed to identify the wastes that they generate. This information should be recorded on the label. Whenever possible, the label should also record where the waste was generated because this enables problems to be investigated quickly should problems develop.

When hazardous waste is being treated on-site, labels should be used to differentiate between the wastes that have been treated and those which have not. If the waste is being autoclaved, the heat-sensitive tape can be used, which, when processed, irreversibly changes color.

Labels should be placed in a position where they can be easily read. They should not be placed on lids because the lids may become separated from the waste. Labels should be sufficiently durable to ensure legibility in wet or damp conditions.

Old labels should be removed or obliterated before new labels are applied so wastes can be properly identified.

Most countries specify how dangerous materials, including hazardous wastes, should be labeled for transport. International legislation also applies. 

Management of  Empty Hazardous Waste Containers

If a container has been used to store hazardous waste, it will become contaminated. Even though the container may appear “empty,” it should be treated as hazardous waste until a formal inspection, test, or cleaning activity has been performed. Following an inspection, test, or cleaning activity, it should be documented that the container has been emptied or cleaned to a defined standard.

Many countries have specified de minimis standards, which, provided they are not exceeded, allow the container to be treated as empty. In the case of a nominally empty container, this is typically assumed to be less than 1% of the total volume.  For some wastes, a simple visual inspection may be sufficient to confirm this. However, for other “sticky” wastes, a validated washing procedure may be needed.

If it is decided to implement such measures, systems should be implemented to ensure that “hazardous” containers cannot be mixed up with “clean” containers. Because of the complexities of setting up such systems, it is recommended that the concept of “de minimis” is applied with care and whenever possible in consultation with Regulatory agencies.

Hazardous Waste Storage Areas

When hazardous wastes have been collected, they should be transferred to a single location where they can be stored securely until arrangements can be made for them to be collected and transported from the site.

Design of Hazardous Waste Storage Area

Hazardous wastes should be stored in a purpose-built bunded area. The volume of the bund should be sufficient to contain at least 110% of the volume of the largest vessel or 10% of the total volume of all the containers located in the bund. Tank connections should be retained within the bunded area to prevent the escape of spills or leaks during waste transfer operations. Liquids should not be allowed to accumulate in the bunded area because this will reduce their volume. Access into the bunded area should be provided by means of a ramp.

The bunded area should fall to a sump so all liquids resulting from spills, leaks, or precipitation drain away from the waste containers.  The provision of a sump also facilitates the removal of liquids from the bund. Drains should not be located in the bunded area.

All tanker trucks or other vehicles off-loading or collecting hazardous waste materials should be loaded in a specified area or roadway that is constructed of impervious materials. The area should have appropriate curbing and a road depression leading to a holding tank adequate to contain 110% of the volume of the largest tanker, should a spill occur. A drip tray should be placed under the connection between the hose and the vehicle.

If hazardous materials are stored for longer periods, a shelter is provided to prevent the ingress of water into the bund and to prevent packaged wastes from being weathered. If flammable gases or liquids are stored, care should be taken to provide adequate ventilation. Precautions against fire should also be taken.

The storage area should be adequately lit. At least 300 lux, measured at ground level, is recommended.

If the storage area is used for packaged wastes, these should be placed sufficiently far from the bund wall so that their contents cannot spill or escape over the wall into an un-bunded area. Whenever possible, racking should be provided, and, as a minimum, drums and other containers should be raised off the ground to allow easy access for inspection and maintenance.  This also prevents the base of steel drums from being corroded by the “sweating” of the concrete.

Storage areas for hazardous wastes should be secured to prevent unauthorized access. They should also be labeled appropriately.

Storage of Biohazardous or Clinical Waste

It is recommended that biohazardous or other clinical wastes are refrigerated (below 5°C) to minimize malodors. This is particularly important if the waste is stored for longer than 48 hours.

Storage of Laboratory Wastes

Where large quantities of laboratory wastes require storage, a mobile chemical store may be used. Such stores enable several hundred items to be stored securely.

Storage of Gas Cylinders

Unless it can be proven that cylinders are empty, it should always be assumed that they contain a residual volume of gas.  The contents of such cylinders may be explosive, oxidizing, corrosive, or toxic and, if liquefied, may need to be stored under extremely low temperatures.  The pressure under which the gases are placed in cylinders poses its own hazards.

Storage facilities for compressed gas cylinders should preferably be located outside or in a well-ventilated area and should be isolated from other waste storage areas and any potential ignition sources.  Cylinders should be kept upright, and all tall cylinders should be secured to a permanent fixture by, for example, clamps or chains.

Segregation of Hazardous Waste

Hazardous wastes should be segregated from non-hazardous wastes. If hazardous wastes are allowed to mix with non-hazardous wastes, the entire mix should be classified as hazardous. Color-coded containers can be used to aid segregation activities.
Incompatible wastes should be segregated to prevent violent reactions from occurring if spills and leaks occur. Following are some potential reactions if incompatible wastes are allowed to mix.

Examples of incompatible materials that should be segregated from each other include:

  • chlorinated and non-chlorinated solvents;
  • aliphatic and aromatic solvents;
  • freon and methylene chloride;
  • water-based materials and flammable materials.

Hazardous wastes can be segregated using a variety of methods.

Hazardous Waste Segregation Guide

* : Segregation is not required from the same class of substance.
0 : Separation may not be necessary, but suppliers of the hazardous substances should be consulted about special requirements.  In particular, it should be noted that some types of chemicals within the same class may react violently, generate much heat if mixed, or evolve toxic fumes.
1 : “Keep apart” – Separate packages by at least 3 m or one gangway width, whichever is the greater distance in the store room or storage compound outdoors.  Materials in non-combustible packaging that are not hazardous substances and which present a low fire hazard may be stored in the 3 m space.  At least this standard of separation should be provided between substances known to react together readily if that reaction would increase the danger.
2 : “Segregate from” – These combinations should not be kept in the same building compartment or outdoor storage compound.  Compartment walls should be imperforate, of at least 30-minute fire-resisting construction, and sufficiently durable to withstand normal wear and tear.  Brick or concrete construction is recommended.  One alternative is to provide separate outdoor compounds with adequate space between them.
3 : “Isolate” – This is used for organic peroxides, for which dedicated buildings are recommended. Alternatively, some peroxides may be stored outside in fire-resisting secure cabinets.  In either case, adequate separation from other buildings and boundaries is required.

Class 1 substances (explosives) and class 7 substances (radioactive) should be completely isolated from all other substances and waste materials; hence they are not included in the above table. Where a particular material has the properties of more than one class, the classification giving the more onerous segregation requirements should be used.

Inspection of Waste Storage Areas

Waste collection and storage areas should be regularly inspected. The inspection should investigate the following:

  • physical condition of the storage area, including the integrity of the bund or secondary containment;
  • security provisions to ensure that free access is prevented;
  • presence of liquid in the bund, and if the liquid is contaminated, it should be treated as if it were a hazardous waste;
  • labeling and segregation to ensure that wastes have been correctly identified and segregated;
  • period of time that containers have been stored.

Containers used to store hazardous waste often deteriorate with age. Procedures should be developed to ensure that wastes are removed as soon as possible. Several systems can be used to track how long wastes are stored. The simplest system is to mark each container using a paint pen, with the date that it was filled, and to record this in a card index system or a computer spreadsheet.

Loading, Unloading, and Internal Transfer of Hazardous Waste

Handling hazardous waste and opening hazardous waste containers should be kept to a minimum. However, where opening a waste container is unavoidable, the container should be closed again as quickly as is practicable to minimize emissions and the risk of an accident. Hazardous wastes should never be poured directly from one container to another.

Before hazardous wastes are loaded, unloaded, or transferred, a chemical risk assessment should be performed. The assessment results should determine how the person handling the waste should be protected from the hazards associated with the waste. Because of the nature of waste, overalls, safety boots, safety glasses, and plastic gloves should be specified as a minimum standard. Additional personal protective equipment (PPE) such as Respiratory Protective Equipment (RPE) or impermeable “coveralls” may be required where, for example, toxic or corrosive waste is handled.

Containers of hazardous waste should be transported in a manner that will minimize the risk of damage to the container and spillage of the contents. Containers such as drums or IBCs should only be mobilized using trolleys, powered equipment (e.g., forklift trucks), or hand trucks. Under no circumstances should containers be tipped or rolled, even when empty. Negligent handling may damage the seams resulting in future leaks or ruptures. Where possible, the trolleys or forklifts should incorporate a bund or drip tray to contain spills. If a forklift is used to transport an individual drum, a “drum clamp” should be used to help stabilize the drums during transportation. 

Hazardous waste collection activities should be supervised at all times. Equipment such as absorbent pads and barrier materials (sandbags or proprietary absorbent granules) should be located in close proximity to where hazardous waste is collected, transported, or stored.  If 205 liter (55 gallons) drums are used to store liquids, “over-drums” or salvage drums should be available. Leaking drums can be placed inside these containers to contain the leak.

Spills of liquid waste should be soaked up using absorbent materials and disposed of as hazardous waste. Spills of dry hazardous wastes should be cleaned using an industrial vacuum cleaner. Some hazardous wastes are water-reactive, and on no account should such wastes be cleaned up using water.  Dry waste should not be cleaned up by dry brushing because the waste may become airborne and be inhaled.

HSE Windsock

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