August 2014, Vol. 26, No.8

Safety Corner

Playing by the rules

Hazardous waste in labs is no small matter How labs can identify, manage, and treat their unique waste streams

Elizabeth Turner

Laboratories, especially water and wastewater laboratories, produce minuscule amounts of hazardous waste. But this waste presents a challenge unique to labs. Why? Simply put, no other class of waste generator produces anything close to the number of different chemical wastes of a laboratory.  

Most of today’s environmental management requirements are based on regulations that were designed for relatively simple processes in manufacturing (such as printing) and service (such as dry cleaning) entities. Federal and state laws govern the identification, labeling, packaging, storing, and disposal of such hazardous waste. The framework is the Federal Resource Conservation and Recovery Act(RCRA; 40 CFR 260–279). This act, passed in 1976, introduced the concept that the generator of a waste is responsible for its management from “cradle-to-grave” (i.e., generation to disposal).  

Small lab operations, in general, are different from those industries as Table 1 (right) indicates. The uniqueness of small lab operations means that typical approaches to environmental management need careful consideration, and possible adjustment, to work well.  

By educating workers on the federal, state, and local requirements for hazardous waste and what constitutes a hazardous waste, labs can protect the public, its workers, and the environment. It also can manage and safely dispose of the myriad wastes that enter and leave its doors.  

Waste generator status, recordkeeping

All laboratories are waste generators. Generators are classified as  

  • conditionally exempt small quantity generators (CESQGs),
  • small quantity generators (SQGs), or;
  • large quantity generators. 


Most water and wastewater laboratories are either CESQGs or SQGs. Table 2 (below) lists the waste limitations and regulatory requirements for the each type of generator. If a laboratory is a CESQG, it is required to identify all the hazardous waste generated and ensure that monthly quantities are less than 220 lb/month with a maximum accumulation of 2200 lb. There are no time limits on how long the laboratory can store the waste before disposal as long as the accumulation is less than 2200 lb.

All generators are required to characterize accurately their wastes based on process knowledge or through testing. Testing can be expensive, even if done in-house, so the least expensive option for small labs is documenting process knowledge. A simple form such as the one in the figure (below) can be used. The form must be maintained in the laboratory and readily accessible. Material Safety Data Sheets are an excellent resource for completing a process knowledge form. Regulatory requirements vary based on the generator status so any laboratory must maintain thorough records. A hazardous waste log is useful for tracking the amount of waste generated each month. The log should include  

  • date of waste generation, 
  • description of the waste, and 
  • quantity of waste generated. 

To effectively manage hazardous waste, it must first be identified. Waste identification is a four-step process.

Step 1: Is the material a solid waste?  

Solid waste is any garbage, refuse, sludge, and can be in gas, liquid, or solid form. If any material does not meet the definition of a solid waste, it is not a hazardous waste (see RCRA for a definition).


Step 2: Is the waste specifically excluded in 40 CFR 261.4? 

Such excluded wastes that are relevant for labs include  

  • mixtures of untreated sanitary wastes and other waste discharged to a publicly owned treatment works, and 
  • waste characterization samples and treatability study samples (until they are designated for disposal by the laboratory).


In addition, empty hazardous waste containers are not considered hazardous unless they contained P- or U-listed wastes.
P- and U-listed wastes can be found in 40 CFR 261.33. For example, many labs use acetone, which is a U-listed waste.


Step 3: Is the waste listed as a hazardous waste per 40 CFR 261.3? 

Waste codes F001 through F005 are hazardous wastes associated with solvents, which are relevant for labs. It is important to note that solvent wastes, unlike other wastes, are hazardous based on the starting composition of the solvent — not on the end product.


Step 4: Is the waste a “characteristic waste” per 40 CFR 261.3? 

By far, the greatest amounts of hazardous wastes generated by a laboratory are characteristic wastes. Even if a lab determines a waste to be hazardous, it must also determine if it is a characteristic waste, based on the following:


  • Ignitability – Liquids with flash points less than 60°C (140°F) and nonliquids that spontaneously combust. 
  • Corrosivity – Usually aqueous solutions with pH less than 2 or greater than 12.5. 
  • Reactivity– Wastes that are unstable, explosive, detonate when heated, or react violently with water. Cyanide wastes usually are reactive wastes. 
  •  Toxicity – Wastes determined to contain certain regulated constituents above specified concentrations when subjected to the Toxicity Characteristic Leaching Procedure (TCLP) test method.  


Waste management 

Labs should consider how waste is accumulated as part of waste management. Will “satellite” accumulation areas or only one central accumulation area be used? The lab’s physical size and layout usually dictate accumulation options.

Satellite accumulation areas. These are located at or near the site that generates the waste. Regulations allow for the accumulation of up to 208 L (55 gal) of hazardous waste or 1 quart acutely hazardous waste in a satellite accumulation area. Regardless of generator status, there is no maximum time limit to accumulate these types and amounts of waste at a satellite accumulation area. However, once the maximum is reached, the waste must be moved to the central waste accumulation area within 72 hours. The waste must be kept in a closed, properly labeled container.

Central accumulation areas. This is where waste is stored before it is sent to a treatment, storage, and disposal (TSD) facility. There are no special requirements for this area other than it must be secure and incompatible wastes must be separated. Secondary containment is recommended for CESQGs. An unused fume hood can be the waste accumulation area. The waste container must be dated when it enters the accumulation area and labeled with the words “Hazardous Waste.” Hazardous waste can remain in the accumulation area for the time allowed for each generator class. Weekly inspections of the accumulation area are not required but strongly encouraged for CESQGs.


Waste treatment 

Laboratories are not allowed to treat any waste onsite unless the laboratory is a permitted TSD facility. However, no laboratory wants to be a TSD facility. But lab wastes can still qualify for exclusions that will permit some treatment to reduce the amount generated.

The U.S. Environmental Protection Agency and most state regulators allow the use of elementary neutralization units (ENUs) to reduce corrosive waste accumulation. Two important points to remember are that elementary neutralization refers only to pH adjustment and that neutralized waste can be washed down the drain if it meets all applicable discharge standards (i.e., local, state, and federal limits). ENUs are tanks, tank systems, containers, transport vehicles, or vessels used for neutralizing wastes that are hazardous only because they exhibit the corrosivity characteristic or because they are listed solely for the characteristic of corrosivity (40 CFR 260.10). In addition, generators managing hazardous waste immediately upon generation in an onsite ENU are not required to count those wastes toward their monthly generator status (40 CFR 261.5[c][2]).

For example, the waste accumulation container on an ICP-MS can be used as an ENU. Usually the metal waste content is low and its hazardous waste status is only due to low pH. The waste can be neutralized as it is added to the ENU by adding sodium hydroxide to the container. Before disposal, the solution should be checked to confirm that its pH is between 2 and 12.5. The metal content also should be checked to confirm that the limits are less than TCLP limits.

Preserved samples, such as those preserved with nitric acid for metals analysis or sulfuric acid for ammonia analysis, are not waste until the samples are no longer required for analysis and can be designated for disposal. These samples also can be neutralized through the use of an ENU or neutralize tank. Undersink neutralization tanks containing limestone are relatively inexpensive to install and maintain. If neutralization is performed as the samples are designated for disposal, the samples do not need to be included in the hazardous waste totals. However, if a laboratory accumulates samples and neutralizes a large batch at one time, that batch must be recorded as generated hazardous waste. The general rule is, if you accumulate it, you must count it.

Pretreatment regulations apply to determine if neutralized waste or nonhazardous waste can be discharged down the drain. Often a material will not be considered hazardous but it cannot be discharged down the drain, including


  • solutions with a pH less than 5.0 or greater than 10.5, 
  • solutions that contain oil or grease, or 
  • solutions that exceed specific metals content such as arsenic levels greater than 0.5 mg/L or zinc levels greater than 5.0 mg/L. 


Material that is not hazardous waste but cannot be directly discharged into the sanitary sewer system may be disposed of in the trash. 


Waste disposal 

The laboratory must contact a hazardous waste disposal firm to transport waste to a TSD facility. The disposal firm may assist the laboratory in inventorying and classifying the waste, but it is still the laboratory’s responsibility to properly classify the waste.

A hazardous waste manifest form must accompany all shipments of hazardous waste. Usually the disposal firm will complete the manifest, but it is the laboratory’s responsibility, as the waste generator, to ensure that the manifest is completed correctly. It also is the laboratory’s responsibility to track down the signed manifest if it is not received by the TSD facility within 45 days. All waste records must be retained for 3 years.


Reduce and reuse where possible 

Regardless of their generator status, all labs as waste generators must classify their waste, document their waste classification process, properly label the waste containers, track the amount of waste generated each month, and maintain all waste records.

It is important that a lab understand its waste streams. Waste streams could include the purchased chemical, empty container, residue or contaminated soil, water or other debris resulting from a spill or its cleanup. For toxicity characteristics, a review of the Material Safety Data Sheet is helpful.

Before final classification of a waste, the lab should be sure that the material cannot be reused for another purpose. One example is the use of used acetone to clean containers for whole effluent toxicity testing. The material may not be suitable for analytical work but may be useful to remove labels and writing from the outside of containers.


Elizabeth Turner is the environmental services manager of the North Texas Municipal Water District (Wylie, Texas). She also is a member of the Water Environment Federation Laboratory Practices Committee. 


What about other types of wastes in a lab? 


Universal waste  

Universal waste is hazardous waste that can be handled in a manner to promote recycling. RCRA (40 CFR 261.9) lists batteries, pesticides, and mercury-containing equipment and lamps as universal waste. States may allow other hazardous waste to be managed as universal waste. In Texas, for example, paint also may be considered universal waste.  

The benefits of classifying a waste as universal are the waste does not count toward generator status and it may be accumulated up to 1 year. SQGs or larger waste generators can benefit by classifying such materials as batteries, pesticides, mercury-containing equipment, lamps, and paint to reduce generator status. 


Waste in aerosol cans 

Empty aerosol cans are not hazardous waste when they have been emptied of contents, but nonempty aerosol cans are considered hazardous wastes even if the product they contain is nonhazardous.   

Regardless of the contents, most aerosols are hazardous because they are ignitable due to the propellants used. Nonempty aerosol cans commonly are discarded for a number of reasons (for example, the spray mechanism is clogged and no longer works). The nonempty aerosol can is a hazardous waste if the aerosol can contains pressurized contents that may explode when heated; if the propellant is ignitable or toxic; or the product itself is ignitable, corrosive, or toxic.  


Safety table 1

Safety table 2