1. Legal Disposal into Sewer Systems
   1. Acids and Bases
   2. Other Inorganic Compounds
2. Illegal Disposal into Sewer Systems
3. Satellite Hazardous Waste Accumulation Sites
   1. Containers
   2. Records
   3. Labels
   4. Inspection
4. Unknowns
5. Summary

Current disposal regulations are intended to prevent harm to human health and the environment by industrial wastes. Unfortunately because the regulations were written for industrial situations, materials that are harmless in laboratory quantities may be regulated as hazardous wastes, and laboratory materials known to be hazardous may be unregulated. Nonetheless, it is our responsibility as citizens and especially as chemists, to dispose of the materials with which we work safely and in accordance with the law. Laws regarding the disposal of chemicals are enforced by the Federal Environmental Protection Agency (EPA) and the Maine Department of Environmental Protection (DEP).

The law requires that a "hazard assessment" be done when one is preparing to dispose of waste. All potentially hazardous constituents of the waste must be considered. When in doubt, one should consider that disposing of a harmless material as a hazardous waste is better than dumping into the environment something that later may be found to be harmful.

An important point to remember here is that nothing is waste until you say it is. As long as you have an MSDS, and follow safe practice in storage, you may keep chemicals forever if you wish. No law requires you to throw out anything. But once you decide to get rid of something, the law regulates how you may do so.

A. Legal Disposal into Sewer Systems.

The large majority of chemical substances must be disposed of by transmitting them to a company licensed to operate a disposal facility (see below). Others may be treated by a trained individual to reduce the quantity of material that must be disposed of. A few substances can be treated and flushed down the drain by any reasonably careful person.

1. Acids and Bases. Mineral acids and bases may be neutralized and the resulting salt solutions flushed down the drain, provided that the material is not hazardous for reasons other than its acidity or basicity. Follow the steps below:
   • Prepare a dilute aqueous solution of the acid or base to be destroyed in a beaker or wide-mouth flask. Always add acid or base to an excess of water. Never add the water to the acid or base, because the heat generated may be enough to boil the water, and expel the substance violently from the container. Set the container in a plastic tub containing ice-water while preparing the solution.

   • Similarly, prepare a dilute solution of sodium hydroxide if you wish to neutralize an acid, or hydrochloric acid if you are neutralizing a base. Cool this solution in ice-water also.

   • Using pH paper or a pH meter, and keeping the receiving flask in the ice-bath, neutralize to pH 6.6-7.4. Stir well while mixing the solutions.

   • Turn on the cold water in the sink to a vigorous stream, and wash the neutralized solution down the drain.

2. Other Inorganic Compounds also may be dissolved in water and flushed down the drain with much cold water, provided they do not contain any heavy metals or toxic anions, and are not powerful oxidizers or water reactive. Thus, lithium, sodium, potassium, magnesium, and calcium salts may be disposed of in this way, but arsenic, barium, copper, tin, lead, silver, iron, cobalt, nickel, chromium, zinc, manganese, and mercury salts may not be. Chlorides, bromides, carbonates and bicarbonates, sulfates, and nitrates may go down the drain, but fluorides, sulfides, bisulfides, and cyanides may not. Many states and towns have ordinances against phosphates in detergents; hence, phosphate salts generally should not go down the drain. Obviously, insoluble materials of whatever type should not be flushed down the drain.

B. Illegal Disposal into Sewer Systems

With the exception of the inorganic compounds noted under (A), the treatment of hazardous wastes is unlawful without a permit from the Maine DEP, no matter what the treatment may be. All other wastes must generally be treated as hazardous. Questions regarding whether a particular mixture is hazardous can be directed to the Department Safety Committee (use the form on this Web site) or the University EH and S office.

In general, the following are always considered hazardous wastes:

• All heavy metals and their salts;

• All sulfides, bisulfides, and cyanides;

• All other toxic, oxidizing, or otherwise corrosive inorganics;

• All organic compounds except ethanol below 48 proof (yes, gin, scotch, etc., are hazardous wastes in a laboratory)

• All gases not normally constituents of the earth's atmosphere.

C. Satellite Hazardous Waste Accumulation Sites

Other than the limited number of substances described above, all laboratory wastes, unused chemicals, and research generated samples must be considered hazardous waste, and disposed of by having them collected by the University Environmental Health and Safety staff.

The EPA defines the places within our laboratories where we store temporarily the wastes generated in our teaching and research as "Satellite Hazardous Waste Accumulation Areas". These areas, usually consisting of a few glass containers in the back of a hood, must be managed in accordance with the following rules.

1. You must keep separate containers for incompatible kinds of waste. Incompatible here means exactly what it did when we discussed storage. Thus, for example, acidic and basic wastes should not be added to the same container.

2. A record must be kept of the nature and approximate quantity of each addition to a waste container. The record must be attached to the container, or kept immediately adjacent.

3. The container must be labeled as "Hazardous Waste" (even if it isn't really hazardous); bright yellow labels are available in the stockroom. Sub-labeling, such as "Chlorinated Solvents" is useful in keeping wastes properly segregated.

4. Containers must be kept closed, unless there is potential danger of gas formation. In such cases a vented cap should be employed.

5. Each site must be inspected each working day by a responsible individual, usually a graduate student designated by his or her advisor as in charge of a particular laboratory. A form confirming the inspection must be signed, and kept adjacent to the storage area. Weekends and legal holidays are excluded from this requirement; apparently leaking waste containers are not dangerous at these times.

6. A hood that is used for waste storage may not be used for experimentation! EPA and OSHA differ, in fact, on just where waste containers may be stored; OSHA prefers otherwise unused hoods, but EPA prefers any storage location where a spill will not reach a floor or sink drain. Consult with your advisor to establish the best location for your laboratory.

D. Unknowns.

Unidentified substances present a major problem for both storage and disposal. A substance may not be kept in the stockroom or laboratory without an MSDS being available (unless it is a substance for which no MSDS exists - a research generated sample), and an identifying label attached.

Unknowns can be removed by the EH and S staff, but their disposal by the firm with which the University contracts is expensive. Hence, the best policy is:

• Do a thorough cleanup of your laboratory, and dispose of all unknowns at one time.

• Subsequently follow the storage and labeling practices described above to ensure that no unknowns are generated in future.

• Keep chemical storage in the laboratoy to a minimum. Oder only what you need, and dispose of any residue promptly.

E. Summary of Disposal Recommendations

To maintain a safe stockroom and laboratory, one must:

1. Regularly inspect the chemical and waste storage areas, removing outdated and leaking chemicals.

2. Collect safely and dispose of promptly all mixed experimental wastes.

3. Have wastes collected frequently. No quantity of waste is small enough to be kept past a scheduled pickup date.