a generator may accumulate up to 55 gallons of hazardous waste, or 1 quart of acutely hazardous waste, "at or near any point of generation where wastes initially accumulate which is under the control of the operator of the process generating the waste...." Under this provision, which is recognized by some but not all state RCRA-enforcement agencies, individual laboratories, or "satellite" locations as they are sometimes termed, may be allowed to accumulate and store hazardous waste, but the waste must be dated and removed within 3 calendar days after reaching the 55 gallon limit. However, safe practice and the requirements of state and local regulation should guide laboratory managers in adhering to reasonable limits on accumulation volume and time. Prudent practice is to limit accumulation time to no more than 1 year (preferably less), and 55 gallons may be too large a quantity for a laboratory location, because of space limitations, fire code limitations, and potential spill or release hazards. When waste accumulates for long periods, laboratory workers tend to forget about it. Hazardous waste, even in small quantities, should never be forgotten.
Only a few years ago, it was common practice to dispose of many laboratory wastes down the drain. Today, the indiscriminate disposal to the sanitary sewer of laboratory chemicals is not acceptable. Most laboratory drain systems are connected to sanitary sewer systems, and their effluent will eventually go to a sewage treatment plant. Some chemicals can interfere with the proper functioning of sewage treatment facilities or affect particularly sensitive bodies of water into which the chemical is discharged. In the laboratory drain system itself, some chemicals can create hazards of fire, explosion, or local air pollution. Others can corrode the drain system.
It is essential to recognize that the characteristics of wastewater treatment plants vary from one locality to another. These factors and local regulations govern what types and concentrations of chemicals can be disposed of. While RCRA regulations do exempt mixtures of hazardous waste and domestic sewage from hazardous waste regulation, local regulations of drain disposal are often more restrictive. While drain disposal of some nonhazardous chemicals may be acceptable, drain disposal of hazardous chemicals is permissible only under carefully prescribed circumstances. Some institutions, responding to strict local controls and concerns, have, as a matter of policy, simply adopted a conservative course and banned the drain disposal of any laboratory chemicals.
If the institution, after appropriate consideration, determines that some drain disposal should be permitted, the following general points of guidance should be adhered to:
Use drain disposal only if the drain system flows to a wastewater treatment plant, and not into a septic tank system or a storm sewer system that flows directly into surface water.
Make sure that the chemical to be disposed of is compatible with other materials being disposed of, and compatible with the piping material.
Monitor sewer disposal of laboratory waste by individual workers or students for adherence to guidelines on types of chemicals, quantities and rates, and flushing procedures.
Remember that only those compounds that are reasonably soluble in water are suitable for drain disposal.
(Chapter 7 contains more detailed guidance on these and other points regarding drain disposal.) Under the Federal Water Pollution Control Act, all direct dischargers, that is, those who discharge effluents directly into rivers, streams, or other bodies of water, are required to have a National Pollutant Discharge Elimination Systems (NPDES) permit. Indirect dischargers, that is, those who discharge effluents into publicly owned sewage treatment works, are not required to have a permit, but must be subject to discharge conditions set by the local wastewater treatment authority. Because many of these local sanitary sewer and water treatment districts have their own, more restrictive, requirements, there should be no drain disposal of hazardous materials without checking with local authorities.
A container or inner liner of a container that contained hazardous waste is "empty" under RCRA regulations if all waste has been removed by standard practice and no more than 2.5 cm (1 inch) of residue, or 3 percent by weight of containers less than 110 gallons, remains. These should be taken as upper limits, and in practice all "capturable" quantities of the substance should be removed. As an "empty" container, it is no longer subject to RCRA regulation. It should be noted, however, that if the container held acute hazardous waste, triple rinsing or equivalent measures are required before the container is "empty" within the RCRA regulations. Indeed, rinsing with water or a detergent solution is prudent for all hazardous waste containers. Rinsates resulting from the cleaning of empty containers that contained acutely hazardous waste are themselves hazardous waste and must be