Waste collection and disposal safety knowledge

Waste generated in the laboratory can be divided into three categories: waste gas, waste liquid and waste residue, namely "three wastes".

Classification of liquid waste

① General wastewater: mainly comes from laboratory cleaning water and can be discharged directly.

② Chemical waste liquid: divided into organic chemical experimental waste liquid and inorganic chemical experimental waste liquid. Organic chemical experimental waste liquid generally includes oils and fats, halogen-containing organic solvents, halogen-free organic solvents, formaldehyde-containing organic solvents, etc.; inorganic chemical experimental waste liquid generally includes heavy metal-containing waste liquid, acidic waste liquid, alkaline waste liquid, hexavalent chromium-containing waste liquid, mercury-containing waste liquid, fluorine-containing waste liquid, cyanide-containing waste liquid, etc. It must be collected and disposed of in accordance with regulations.

③ Infectious waste liquid: refers to experimental waste liquid that carries pathogenic microorganisms and has the risk of causing the spread of infectious diseases.

Precautions for waste liquid collection and storage：

① The container for waste liquid should be labeled with the name, quantity, composition, waste liquid producing unit, address, telephone number, contact person, safety measures, date and hazardous characteristics of the waste liquid; the label should be pasted in a position that is easy to observe and not easily damaged by the waste liquid.

② Chemical waste liquids of different categories or sources that may have dangerous consequences after mixing should not be stored in the same container to avoid violent chemical reactions and accidents.

③ When handling chemical waste liquids, appropriate personal protective equipment (such as protective glasses, gloves and laboratory coats) must be worn, and slippers, shorts, etc. must not be worn.

④ When pouring a large amount of liquid waste into a chemical waste container, a funnel should be used to prevent leakage.

⑤ When transporting chemicals or transferring chemicals to waste containers, they must be handled with care to avoid violent collisions; to prevent the release of vapor, the container should be covered in time.

⑥ When using containers to store liquid chemical waste, there should be enough space in the container, and it should not be too full. It can only be loaded to 70% to 80% of the total capacity.

Treatment methods for common chemical waste liquids in laboratories：

① Inorganic waste liquid disposal method: Inorganic acids, neutralize with excessive aqueous solution containing sodium carbonate or calcium hydroxide or waste alkali liquid; waste liquid containing sodium hydroxide and ammonia, neutralize with hydrochloric acid aqueous solution, dilute to pH 6-8; fluorine-containing waste liquid, add slaked lime milk (calcium hydroxide slurry) to alkaline, leave overnight, filter; chromium-containing waste liquid, first add ferrous sulfate under acidic conditions to reduce Cr (VI) to Cr (III), then add alkali to precipitate it as Cr (OH) 3 for reuse; mercury-containing waste liquid, adjust the pH value to 6-10, add excessive sodium sulfide to precipitate it; arsenic-containing waste liquid, add Fe3+ and lime milk to precipitate it, separate; cyanide-containing waste liquid: be sure to adjust the pH value to alkaline first, add sodium thiosulfate, ferrous sulfate, sodium hypochlorite, potassium permanganate to generate thiocyanate; waste liquid containing multiple heavy metal ions, convert them into hydroxides or sulfides that are insoluble in water and precipitate them.

② Organic waste liquid disposal method: organic solvents that do not contain halogens and have been biodegradable can be diluted and discharged directly, those that are difficult to decompose can be sent to professional institutions for incineration, and those containing heavy metals are oxidized and decomposed and treated as inorganic waste liquid; organic solvents containing nitrogen, sulfur, and halogens are generally sent to professional institutions for incineration. During incineration, measures must be taken to remove the harmful gases produced by their combustion. Difficult-to-combustible substances are treated by extraction, adsorption and hydrolysis; oils and fats are sent to professional institutions for incineration.

③ Infectious waste liquid disposal method: Infectious waste liquid must be sterilized and then treated as ordinary experimental waste liquid. For specific sterilization methods, please refer to the disposal method of infectious waste in biochemical solid waste.

Solid waste disposal：

① Solid waste generated during the experiment must be prevented from being scattered, lost, leaked or polluted by other measures; solid waste must not be dumped, piled, discarded or scattered without authorization.

② Abandoned hazardous solid medicines must not be dumped, abandoned or piled without authorization, and it is strictly prohibited to dump them in domestic garbage.

③ Waste must not be collected, stored or transported in a mixed manner. It must be classified and disposed of according to the characteristics of the waste, and waste identification signs must be affixed to the collection bags to indicate the nature of the waste. Hazardous waste must be treated and detoxified before being discarded.

Hazardous solid waste disposal methods：

① Disposal of chemical solid waste: refers to expired solid chemicals and waste solid chemicals generated during the experiment. They need to be collected and labeled and handed over to qualified units for disposal after notification from the school, and records of disposal and handover should be kept.

② Disposal of biochemical solid waste: refers to solid (solid) waste and related waste experimental tools generated by various biomedical experiments, including infectious waste, damaging waste, pathological waste, and other general biochemical solid waste, such as pipettes, "gun tips", blades, syringes, disposable gloves, EB glue, experimental animal corpses and tissues, etc.

Teaching laboratories should use yellow special plastic bags to package biochemical solid waste (excluding damaging waste), mark them, collect them by category, and hand them over to professional units designated by the school with disposal qualifications for disposal, and keep records of handover. Among them: infectious waste must be sterilized in the laboratory before storage to reduce or limit its potential pathogenicity. Damage waste (sharps) must be placed in a sharps recycling box (usually 3/4 of the capacity is appropriate) and labeled.

Note: The sterilization methods include: high-pressure steam sterilization, and the waste must be placed in a leak-proof container (such as a high-pressure sterilizable plastic bag with a yellow mark) for sterilization. Chemical disinfection is suitable for treating liquid waste and object surfaces. It has a better disinfection effect on waste with non-porous and non-adsorbent surfaces; commonly used chemical disinfectants include acids, alkalis, aldehydes, ethanol, peracetic acid, hydrogen peroxide, etc. The disinfection method should determine the type, concentration and disinfection time of the chemical disinfectant to be used according to the type of pollutants, degree of contamination, protein content, etc. For example, the method of soaking and disinfecting in 2000mg/L effective chlorine disinfectant for 1h is used for inactivation disinfection.