Planning and Purchases
It is your responsibility as generators of hazardous waste to make every attempt possible to minimize the amount produced. To the extent that chemicals can be recovered, recycled, or reused safely there is obvious economic incentive to do so. In addition, materials that are recovered, recycled, or reused do not become a liability problem or a problem for the environment.
The planning of every experiment must include the consideration of the disposal of leftover starting materials and of the products and by products that will be generated. Questions to be considered include the following:
Almost 75% of our present laboratory waste consists of partially used or unopened bottles of chemicals that have been accumulating for decades. Chemicals should be purchased in the smallest possible volumes to reduce the amount of unused chemicals that could end up as laboratory wastes. As the cost of chemical reagents and disposal continues to climb, any reduction in volume of chemicals purchased will offer benefits. Keep in mind that the perceived economy of buying in bulk is more than offset by disposal costs for the package and its residues.
Surplus chemicals should be returned to the stockroom in a timely manner so that they have an opportunity for redistribution. Departments or individuals will be reimbursed for chemicals in good condition. See also Chemical Management Guide.
Recovery and Recycling
The recycling process is exempt from hazardous waste regulation except that waste accumulated prior to recycling must be managed according to accumulation requirements. Distillation is an example of a viable recovery option. All residues such as still bottoms from the recycling process are regulated and must be managed as hazardous waste.
Hazardous waste regulations now require that wastes containing mercury be sent to a facility where mercury can be recovered in a retort or roasting thermal process unit. These recovery methods are very expensive ($30/kg). Most mercury waste at Colgate is the result of broken thermometers or instruments. The remainder is from surplus reagents or experiments.
Waste minimization is the best way to reduce the disposal problems related to mercury. Liquid metallic mercury should be collected for shipment to a reclamation facility. Small quantities can be made relatively free of insoluble contaminants by filtering a few times through conical filter paper with a small hole at the bottom of the cone.
Alcohol or mineral spirit thermometers will be substituted for mercury thermometers whenever possible. In most cases, these can meet accuracy and range requirements. If mercury thermometers must be purchased, use only teflon coated. Stainless steel thermometers can be used in heating and cooling units.
Many substitutes are available for mercury reagents as well. Some alternatives to mercuric chloride as a biocide are solutions such as 5-10% methylene chloride, 1% formalin, 1 N hydrochloric acid, sodium azide, and sodium hypochlorite. If mercury compounds are used as catalysts, an alternative is to simply eliminate the catalyst and let the reaction run longer. Mercury free catalysts such as CuSO4 , TiO2 , or K2SO4 can be used in Kjedahl digests.
Mercury spills can be collected in a flask equipped with a pipette and rubber hose connected to a vacuum source. Small droplets of mercury can be amalgamated with zinc dust and the resulting solids swept up. Droplets in crevices can be converted to mercuric sulfide by dusting with sulfur powder.
Photographic fixer solutions cannot be discharged to the sink and will be collected for silver recovery. The EHSO operates a silver recovery unit in Sb-3 McGregory.
Other candidates for recycling include precious metals, scrap metals, waste oil, and formaldehyde. Every effort must be made to determine if other materials can be reused, recovered, or recycled.
In-lab treatment of small quantities of hazardous waste is an effective way of minimizing off site treatment and disposal costs. Elementary neutralization of corrosive wastes and treatment in accumulation containers is exempt from permitting requirements for hazardous waste treatment. Ideally, these treatment steps should be written into every laboratory procedure. Potential treatment methods include phase separation of organics/aqueous solutions and liquids/solids; acid/base neutralization; precipitation of toxic metals and inorganic salts; oxidation of inorganic cyanides and sulfides. Many procedures for the neutralization or destruction of laboratory wastes are available in the following reference books available in Cooley Science Library:
Hazardous Chemicals Information and Disposal Guide, by Dr. Margaret Ann Amour. CRC Press, Boca Raton, FL, 1987.
Prudent Practices for Disposal of Chemicals from Laboratories, by the National Research Council. National Academy Press, Washington, D.C., 1983.
Destruction of Hazardous Chemicals in the Laboratory, by George Lunn. Wiley, New York, NY, 1990.
TREATMENT OF HAZARDOUS WASTE SHOULD BE DONE VERY CAREFULLY AND IN ACCORDANCE WITH WRITTEN PROCEDURES TO AVOID INJURY.
Return to: Lab Waste Flowchart