The lab technologist approached the Lab Safety Officer to ask what should be done with a collection of liquid wastes that were collected from the chemistry analyzers. The LSO had worked with multiple labs for years helping to determine how to dispose of their liquid chemical wastes according to the regulations. He thought he was pretty well aware of the hazardous chemical wastes coming from the labs, but he had no idea this chemistry analyzer waste existed. He dug a bit deeper. As he called around to the different labs in the system, he learned not all sites were handling the waste the same way. Some sites saved the excess waste and poured it into other containers to use on the analyzers. Some labs threw the containers in the trash with liquid inside, and other sites simply poured the excess chemicals down the sink drain.
Some laboratories and lab systems are very large, and there are probably many practices, some newer, some older, that have developed over time, because “someone said so,” or because a vendor said it was acceptable. The LSO may not always be able to know about every practice in each lab. Staff should always escalate questions about waste processes when there is a concern.
Managing hazardous (chemical) wastes is a complicated process, and training and education is needed in all laboratories. The regulations surrounding waste are numerous and complicated, and it would be unlikely that every lab employee would be aware of all of them. Here are some basics that are true for all laboratories:
Pouring Bulk Wastes Down the Drain is (Usually) Incorrect and Possibly Illegal
In general, manually pouring bulk amounts of chemical waste down the drain is not permitted by the EPA. What is a bulk waste? It is defined as 200 mL or more. That means if you have >200 mL of a reagent left over in a container, you cannot pour it down a drain for disposal. That chemical is now waste and must be properly collected, labeled, and stored until a waste contractor can pick it up.
There are, of course, exceptions to every rule. If a waste drain line is connected to a drain, for example, that is not considered “pouring,” and it is acceptable provided a lab has informed the local wastewater treatment center about what is going down the drain. Performing a gram stain in microbiology and letting the residual chemicals go down the drain is allowed also. That is considered part of the gram stain process, and it is not viewed as “pouring” chemicals down the drain. Also, the wastewater facility is aware that these chemicals are going down the drain.
Another exception exists in some laboratories that have an external “chemical pit” which is tied to certain sinks and drains in the lab. That means that all wastes poured down these drains go straight to a collection tank which neutralizes the chemicals. The tank is emptied periodically by a contracted vendor. Since there is no waste going to the local wastewater system, the local authority does not need to be contacted about what goes down the lab drains.
Hazardous Waste Must be Properly Stored
Anytime a lab collects chemical waste, it must be properly stored. There are two types of waste storage areas, Satellite Accumulation Areas (SAA) and Central Accumulation Areas (CAA). A Satellite Accumulation Area is a storage area near to where the waste is generated. The SAA must be within the line of sight of where the waste is made, it cannot be in another room or around the corner. You must store the waste where it can be seen from where it was generated. You cannot move waste from one SAA to another SAA. You can. However, move waste from a SAA to a Central Accumulation Area (like a hazardous waste shed outside, for example).
SAAs can store up to 55 gallons of waste. Waste must be stored inside of a flammable cabinet if it is flammable, and acid wastes cannot be stored next to bases. SAAs and CAAs must have a specific emergency contact poster hung nearby which indicates the location of the nearest fire extinguisher as well as an emergency contact in case of a spill or accident. CAAs must be checked weekly for proper labeling, open containers, and leaking, and these checks must be documented.
Hazardous Waste Must be Properly Labeled
Anytime a lab collects chemical waste, it must be properly labeled per EPA regulations. All waste containers must be labeled with the identity of the contents and the words “Hazardous Waste.” There must also be an indication of the waste hazard(s), such as a pictogram or an NFPA diamond. If waste is collected into an empty reagent jug, you may not use the wording or warning label from the original jug.
Dates should never be placed on chemical waste labels when stored in a Satellite Accumulation Area, but dates always need to be on containers once moved to the Central Accumulation Area. If the waste vendor picks up containers directly from your SAA, you never need to place dates on the containers.

Again, the proper management of the laboratory hazardous wastes is complicated. There is a great deal to learn and to put in practice. Many regulations have exceptions, and some of them depend on the facility’s waste generator status. If you have questions, reach out to your EPA (or state branch) representative, or ask an available safety expert. Make sure your lab is handling chemical wastes appropriately and safely.