Disposal in the Sanitary Sewer

Laboratories that manipulate infectious agents, blood, or body fluids may generate waste that is contaminated with these mataials and toxic chemicals. In most cases, blood and body fluids that contain toxic chemicals can be disposed of safely in a sanitary sewer, which is designed to accept biological waste. Approval for such disposal should be requested from the local wastewater treatment works. Chemical concentrations in such waste are typically low enough to be accepted by a local treatment works. OSHA recoimnends that a separate sink be used exclusively for disposal of human blood, body fluids, and infectious waste. It may be prudent to treat blood and body fluids with bleach (usually a 1 10 aqueous dilution of household bleach) prior to disposal in the sanitary sewer. The worker should take care to prevent personal exposure while waste is being discharged into the sewer. 

Some institutions grind radioactive animal tissue for disposal in the sanitary sewer, although the U.S. NRC requires that all sewer-disposable waste be dispersible. Preventing contamination and exposure of waste handlers to dust or particles is an iir tortant safety measure in this operation. 

Sanitary Sewer - Some chemicals (acids or bases) may be neutralized and disposed to the sanitary sewer. This disposal option must be approved by the local waste water treatment authority prior to disposal. This may not be an option for some small communities that do not have sufficient treatment capacity at the waste water treatment plant for these types of wastes. Hazardous waste may NOT be disposed of in this manner. This includes heavy metals. 

Dechlorination is the process of converting highly reactive chlorine from these waters into less reactive chloride ions prior to disposal into receiving streams. Various chemical and nonchemical techniques are currently used for disposal of chlorinated waters by water and wastewater agencies. For example, wastewater treatment plants use sulfur dioxide gas or sodium metabisulfate to dechlorinate treated effluent prior to release into receiving streams. Many water utilities often use passive, non-chemical methods such as discharge to sanitary sewers for disposal of chlorinated waters. Impurities such as organics, iron, and sulfide in the sanitary sewer exert a chlorine demand and neutralize chlorine in the released water. 

Although the sewer was the traditional dumping ground for many liquid laboratory wastes, such disposal is now out of the question for most waste chemicals and carries heavy penalties. Nevertheless, not all chemical waste is hazardous, and some may be disposed of in the sanitary sewer under carefully defined conditions. RCRA also controls and defines the in-laboratory treatment of hazardous wastes. Some methods for treatment, most of which may require a permit, are discussed in Chapter 7. 

Disposal in the sewer system (down the drain) had been a common method of waste disposal until recent years. However, environmental concerns, the viability of publicly owned treatment works (POTW), and a changing disposal culture have changed that custom markedly. In fact, many industrial and academic laboratory facilities have completely eliminated sewo" disposal. Again, like trash disposal, most sewo" disposal is controlled locally, and it is therefore advisable to consult with the POTW to determine what is allowed. Yet, it is often reasonable to consider disposal of some chemical waste materials in the sanitary sewer. These include substances that are water-soluble, that do not violate the federal prohibitions on disposal of waste materials that interfere with POTW operations or pose a hazard, and that are allowed by the local sewer facility. 

When possible, select a single management option. Some waste management methods are appropriate for more than one waste hazard. Low-level radioactive animal tissue (a radioactive-biological waste) can often be incinerated on-site, which may be a satisfactory disposal option for both the radioactive and the biological characteristics of the waste. Some multihazardous waste can be disposed of safely in the sanitary sewer when allowed by the local publicly owned treatment works (POTW). 

Use of nonignitable scintillation fluid (e.g., phenylxylylethane, linear alkylbenzenes, and diisopropylnaphthalene) instead of flammable scintillation fluid (e.g., toluene, xylene, and pseudocumene). Liquid scintillation fluid that is sold as being "biodegradable" or "sewer disposable" is more appropriately labeled as "nonignitable" because biodegradability in the sanitary sewer can vary considerably with the local treatment facility. 

Nevertheless, there are still justifiable and legal reasons to carry out such opaations in the laboratory when hazards can be reduced safely. Neutralizatiorr, oxidation, reductiorr, and various otho" chemical conversions as well as physical methods of separation and concentration can be applied prudently to many laboratory-scale mixed wastes. However, the dual character of the hazard, chemical and radioactive, requires that additional precautions be exercised. Treatment for the chemical hazard must not create a radioactivity risk for personnel or the environment. For example, vapors or aerosols from a reaction, distillation, or evaporation must not lead to escape of unsafe levels of radioactive materials into the atmosphere. Fume hoods appropriate for such operations should be designed to trap any radioactive effluent. When mixed waste is made chemically safe for disposal into the sanitary sewer, the laboratory must ensure that the radioactivity hazard is below the standards set by the publicly owned treatment works (POTW). Several examples for reducing the hazard of mixed waste are described below ... 

Some trichloroacetic acid (TCA) solutions contain chloroform in excess of 6 ppm. Such a solution is considered a hazardous chemical waste because it fails the TCLP test. If the neutralized solution is not acceptable to the sewage treatment plant because of the presence of chloroform, it may be possible to remove that component from the solution % filtration through activated charcoal. The resulting radioactive filtrate can usually be disposed of in the sanitary sewer, and the contaminated charcoal can usually be disposed of as a chemical waste. 

High-performance liquid chromatography (HPLC), used to purify radiolabeled proteins and lipids, can generate a waste radioactive solution of acetonitrile, water, methanol, acetic acid, and often a small amount of dimethylformamide. When the solution is distilled by rotary flash evaporation, the distillate of acetonitrile, methanol, and water is nonradioactive and can be handled as a hazardous chemical waste. The radioactive still bottom, containing 1 to 5% methanol and acetic acid, can usually be neutralized, diluted, and disposed of in the sanitary sewer. 

While on-site incineration is the preferred method of managing radioactive animal carcasses and tissue, several alternatives exist. Alkaline digestion of animal carcasses containing H, and formaldehyde, followed by neutralization, results in an aqueous radioactive stream that can usually be disposed of in the sanitary sewer. The process uses 1 M sodium hydroxide at 300 °C and pressures up to 150 psi. Commercial units are available for this process. Radioactive animal carcasses may be accepted at a low-level radioactive waste site when packed in lime. 

Radioactive blood, body fluids, and other sewer-compatible liquids may be disposed of in the sanitary sewer if quantities are within U.S. NRC license and treatment works limits. Precautions must be taken to prevent exposure of waste handlers. OSHA recommends that disposal of human blood and body fluids be done in a dedicated sink. 

Neutralization of acids and bases (corrosives) is generally exempt from a RCRA treatment permit. However, because the products of the reaction are often disposed of in the sanitary sewer, it is important to ensure that hazardous waste such as toxic metal ions is not a part of the effluent. 

To the hydride solution in a flask equipped with a stirrer, ethyl acetate is added slowly. The mixture sometimes becomes so viscous after the addition that stirring is difficult and additional solvent may be required. When the reaction with ethyl acetate has ceased, a saturated aqueous solution of ammonium chloride is added with stirring. The mixture separates into an organic layer and an aqueous layer containing inert inorganic solids. The upper, organic layer should be separated and disposed of as a flammable liquid. The lower, aqueous layer can often be disposed of in the sanitary sewer. 

Potassium and sodium hydride (KH, NaH) in the dry state are pyrophoric, but they can be purchased as a relatively safe dispersion in mineral oil. Either form can be decomposed by adding enough dry hydrocarbon solvent (e.g., heptane) to reduce the hydride concentration below 5% and then adding excess t-butyl alcohol drop wise under nitrogen with stirring. Cold water is then added drop wise, and the resulting two layers are separated. The organic layer can be disposed of as a flammable liquid. The aqueous layer can often be neutralized and disposed of in the sanitary sewer. 

Calcium hydride (CaH2), the least reactive of the materials discussed here, is purchased as a powder. It is decomposed by adding 25 mL of methyl alcohol per gram of hydride under nitrogen with stirring. When reaction has ceased, an equal volume of water is gradually added to the stirred slurry of calcium methoxide. The mixture is then neutralized with acid and disposed of in the sanitary sewer. 

Alkali metals react violently with water, with common hydroxylic solvents, and with halogenated hydrocarbons. They should always be handled in the absence of these materials. The metals are usually destroyed by controlled reaction with an alcohol. The final aqueous alcoholic material can usually be disposed of in the sanitary sewer. 

The solids of this class (e.g., PCI5) tend to cake and fume in moist air and therefore are not conveniently hydrolyzed in a three-necked flask. It is preferable to add them to a 50% excess of 2.5 M sodium hydroxide solution in a beaker or wide-mouth flask equipped with a stirrer and half-filled with crushed ice. If the solid has not all dissolved by the time the ice has melted and the stirred mixture has reached room temperature, the reaction can be completed by heating on a steam bath, and then the acidic solution neutralized and disposed of in the sanitary sewer. 

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. 

No liquid waste can be disposed of directly into the environment or into a storm sewer system. Unless collected and handed over to a waste disposal company, it goes into the sanitary sewer. There are specific rules concerning the quality of what may be disposed of in this manner. Materials that are routinely sent to the sewer from a home may not be permissible from a commercial source. Normally accepted waste water rules are often made more restrictive by local ordinance. 

Routine sewage treatment destroys the VHP viruses. Therefore, staff can dispose liquid medical waste, includmg feces and vomims in me sanitary sewer. However, they should take care to avoid splashmg me materials when disposing of mem. 

Disposal of regulated hazardous waste into the sanitary sewCT is allowed only in limited situations. The total wastewater must be a mixture of domestic sewage along with the waste whose amount and concentration meet the regulations and limits of the POTW. If approved of by the local district, it may be allowable to dispose of dilute solutions of metals and other hazardous chemicals into the sanitary sewer. 

Biological waste can also be disinfected with chemical agents such as bleach or phenolic disinfecting agents. The most common agent is bleach since it is inexpensive and will likely result in a product that can be disposed of down the sanitary sewer. Other chemical disinfection may result in chemical waste that needs further handing by chemical waste management. 

How do you properly dispose of spent chemicals at the end of an experiment In some cases this involves simply flushing chemicals down the drain with the aid of large volumes of water. As an example, solutions of sulfuric acid can be neutralized with a base such as sodium hydroxide, and the aqueous solution of sodium sulfate that results can safely be washed into the sanitary sewer system. However, the environmental regulations that apply in your particular community may require use of alternative procedures. Be certain to check with your instructor before flushing any chemicals down the drain ... 

C. Waste disposal methods Waste material shall be disposed of in a manner that is not hazardous to employees or to the general population. Spills of acrylonitrile and flushing of such spills shall be channeled for appropriate treatment or collection for disposal. They shall not be channeled directly into the sanitary sewer system. In selecting the method of waste disposal, applicable local. State, and Federal regulations should be consulted. 

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