Management of laboratory wastes

 Waste is defined as material that is discarded, is intended to be discarded, or is no longer useful for its intended purpose. The best strategy for managing laboratory waste aims to maximize safety and minimize environmental impact. In waste management there are four tiers to waste management to reduce its environmental impact:

         i.            Pollution prevention and source reduction:

The best approach to laboratory waste is preventing its generation e.g.

·         Reducing the scale of laboratory operations

·         Reducing the formation of waste during laboratory operations

·         Substituting nonhazardous or less hazardous chemicals in chemical procedures.

 

       ii.            Reuse or redistribution of unwanted, surplus materials

Practices that implement this strategy include

·         Purchasing only what is needed

·         Keeping chemical inventories to prevent the purchase of duplicates

·         Reusing excess materials.

 

      iii.            Treatment, reclamation, and recycling of materials within the waste

 

     iv.            Disposal through incineration, treatment, or land burial

 

 

Biological wastes

Biological waste must be managed separately from other forms of wastes. All wastes should be treated before disposal.

Treatment methods for bio-hazardous waste

·         Incineration

·         Auto-claving : Longer times may be required depending on the amount of waste, the presence of water and the type of container used.

·         Dry heat [160 C., 2 hr]: Time of exposure begins after attaining then specific temperature and does not include lag time.

·         Chemical disinfection: 10% hypochlorite or sterilant used according to manufacturer's direction.

Disposal methods of treated bio-hazardous waste

·         Place in a puncture resistant container and deposit treated waste in the Landfill.

·         Flush disinfected liquid into the Sewer System.

·         Interment or cremation

·         Carcasses of animal that die in the field may, under certain conditions, be buried on site under supervision of the University Veterinarian.

·         Place encapsulated sharps in a dumpster for Landfill disposal.

·         Dispose of ashes in the Landfill.

Types of biological wastes

·         Sharps: All sharps should be placed into properly labeled sharps containers or other rigid, puncture-proof containers. The container should be well sealed, labeled, and in-tact.

·         Liquid biological waste: should be collected in containers for autoclaving or chemical disinfection. Autoclaved or chemically disinfected liquid wastes can be disposed via the laboratory sink.

·         Use of sanitary sewer for the disposal of certain liquid wastes as it reduces the chance for leaks or spills during transport and reduces disposal costs. N/B: Do not autoclave containers containing bleach. The combination of bleach and residual cotton and oil (improperly cleaned autoclaves) may result in an explosive combustion within the autoclave.

·         Solid biological waste: such as solidified agarose gels should be collected in appropriate bio-hazardous waste autoclave bags and well-sealed.

·         Animal carcass disposal: Collect frozen carcasses, tissues, etc. in cardboard boxes.  Disposal method is through incineration. 

 

Transport and Storage of Biological Waste

The transport of biological waste outside of the laboratory, for decontamination purposes or storage until pick-up, must be in a closed leak proof container that is labeled "biohazard". Labeling may be accomplished by the use of red or orange autoclave bags or biohazard box-bag units. Container requirements for bio-hazardous wastes:

·         Heavy duty plastic bag or other appropriate container such as BIOHAZARD BAGS

·         Heavy duty leak proof container

·         Puncture resistant container

Labeling of hazardous wastes

Containers of bio-hazardous materials must be clearly identified and marked with the BIOHAZARD symbol.

Chemical wastes

According to the Environmental Protection Agency, wastes can be classified into three subcategories:

·         F list: waste from nonspecific sources (e.g., spent solvents and process or reaction waste);

·         U list: hazardous waste (e.g., toxic laboratory chemicals); and

·         P list: acutely hazardous waste [e.g., highly toxic laboratory chemicals, that is, chemicals having a lethal dose (LD50) of <50 mg/kg (oral, rat)].

Good practices for accumulating chemical waste in the laboratory:

·         Collect hazardous or flammable waste solvents in an appropriate container pending transfer to the satellite site for chemical waste handling or pickup by commercial disposal firm.

·         Take care not to mix incompatible waste.

·         Keep wastes segregated by how they will be managed.

·         Collect waste in dependable containers that are compatible with their contents. Keep containers closed except when adding or subtracting waste.

·         Use an appropriate container for the collection of liquid waste. Glass bottles are impervious to most chemicals but present a breakage hazard, and narrow-neck bottles are difficult to empty. The use of plastic (e.g., polyethylene jerry cans) or metal (galvanized or stainless steel) safety containers for the collection of liquid waste is strongly encouraged.

·         Do not use galvanized steel safety cans for halogenated waste solvents because they tend to corrode and leak.

·         Clearly and securely label waste containers with their contents.

·         Securely cap waste containers when not in immediate use.

·         Collect aqueous waste separately from organic solvent waste. Solutions containing flammable or hazardous waste, even if water-miscible, are almost never allowed, and water-immiscible substances must never be put down the drain. Collect aqueous waste for non-sewer disposal in a container selected for resistance to corrosion. Do not use glass for aqueous waste if there is danger of freezing.

·         Place solid chemical waste, such as reaction byproducts or contaminated filter or chromatography media, in an appropriately labeled container to await disposal or pickup.

·         Consider how to dispose of nonhazardous solid waste in laboratory trash or segregate it for recycling.

 

Treatment methods of chemical wastes

Treatment, recycling, reclamation, and recovery of valuable materials can be achieved through neutralization, oxidation-reduction, distillation, digestion, encapsulation, and several forms of thermal treatment.

The expense and practicality of these technologies is largely based on the specific nature and volume of the material, treatment or recycling is preferable to incineration for some hazardous wastes.

For example, high- and low-pH wastes may be neutralized, resulting in treatable wastewater and salts. Incineration of mercury and other toxic metals is restricted; recycling, recovery, or encapsulation is environmentally preferred.

Disposal methods of chemical wastes

Use of sanitary sewer

Liquid laboratory wastes that are commonly disposed of in the sanitary sewer include spent buffer solutions, neutralized mineral acids and caustics, and very dilute aqueous solutions of water-soluble organic solvents (e.g., methanol, ethanol).

After checking with authorities, some laboratories flush small amounts of water-soluble nontoxic solids into the sanitary sewer with excess water e.g.  Sodium or potassium chloride, nutrients, and other chemicals generally regarded as safe. Disposal of water-miscible flammable liquids in the sewer system is usually severely limited. Water-immiscible chemicals should never go down the drain.

Release of vapors to the atmosphere

Devices for releasing vapors to the atmosphere should be equipped with appropriate trapping devices to eliminate discharge to the environment.

Incineration

Incineration is normally performed in rotary kilns at high temperatures (1200–1400 °F).

This technology provides for complete destruction of most organic materials and significantly reduces the volume of residual material which must be disposed of by landfill.

However, it is an expensive option, generally requiring the use of significant volumes of fuel to generate the required temperatures. Also, some materials, such as mercury and mercury salts, may not be incinerated because of regulations and limitations of the destruction capability.

 

Mixed wastes

It exists as a combination of multi-hazardous waste containing both chemical and radioactive hazards. It is the most problematic form of waste.

Common laboratory waste management methods for radioactive constituents in waste include storage for decay and indefinite on-site storage, burial at a landfill site, incineration, and sanitary sewer disposal.

 

 

Think Tank: How can be chemical-biological wastes be treated and disposed?                      (5 marks)