Laboratories, especially chemical laboratories, are prone to produce toxic and harmful gases when conducting experiments, threatening the safety of laboratory operators and laboratory equipment. Therefore, laboratory waste disposal is very important.
I. Laboratory exhaust gas
(1) Composition and hazard of exhaust gas
There are many kinds of indoor air pollutants in chemical laboratory, including organic gas and inorganic gas. These gases are directly discharged into the atmosphere, which will aggravate the formation of acid rain and constitute a serious social hazard. If people inhale more, they will cause direct harm.
1, inorganic waste gas mainly includes: nitrogen oxide, sulfuric acid fog, argon hydrogen chloride fluoride, hydrogen sulfide sulfur dioxide and other inorganic waste gas.
2, organic waste gas mainly includes aromatic: benzene, toluene, xylene styrene, etc.; Aldehydes and ketones: formaldehyde, acetaldehyde, glutaraldehyde, butyral, acetone, cyclohexanone, methyl ethyl ketone, acetophenone, etc. Esters: isobutyl acetate, ethyl acetate, butyl acetate, methyl acetate, banana water, etc. Alcohols: methanol, ethanol, butanol, isopropyl alcohol, ethyl alcohol, etc.
(2) the main principles and methods for waste disposal
At present, the treatment methods of gaseous pollutants can be generally divided into two categories: wet method and dry method. It is necessary to select high-efficiency and low-cost methods according to the characteristics of waste gas in chemical laboratories.
A, wet waste gas treatment wet method
Waste gas treatment by acid fog purification tower for waste gas treatment, suitable for purification hydrogen chloride gas (HC) fluoride argon gas (HF), ammonia gas (NH3), sulfuric acid fog (H2SO4), chromic acid fog (CrO3), hydrogen cyanide acid gas (HCN), hydrogen sulfide gas (H2S). Low concentration of NOx waste gas and other water-soluble gases, with good purification effect, compact structure, small footprint, corrosion resistance, good aging resistance, convenient installation, transportation, maintenance management, equipment structure is simple, less one-time investment and other characteristics, so it is widely used in the treatment of gaseous pollutants. Acid mist purification tower, suitable for high-rise buildings are installed on the roof, the working principle is purified by acid mist exhaust fan pressure into the tower, after spray and packing layer, waste gas with sodium hydroxide absorption and good contact with liquid in gas liquid two phase absorption neutralization reaction, acid mist exhaust after purification, remove waste liquid layer liquid treatment and then discharged into the atmosphere. The purified acid fog exhaust gas can be lower than the national emission standard.
B, dry waste treatment dry method
Waste gas treatment refers to the process of adsorbing a component or some components of the mixture on the solid surface by using the unbalanced molecular attraction or chemical bond force on the solid surface when the gas mixture is in contact with the porous solid. The solid with adsorption is called adsorbent. The advantages of this method are simple equipment, convenient operation and easy to realize automatic control. However, due to the different physical and chemical properties of adsorbents, they have strong pertinence, so the waste containing different harmful substances should be configured with different physical and chemical properties of adsorbents, in order to play a good role in gas purification; If the exhaust gas passes through the adsorbent for a short time, the content of harmful substances in the exhaust gas is too high, the effect of exhaust gas purification will be not ideal. When the exhaust gas passes through the adsorption medium, because the air flow is blocked by the solid medium, the power of the fan must be increased to ensure the normal wind speed of the ventilation system. The adsorbent needs to be replaced or regenerated regularly to ensure the normal operation of the absorption device. Therefore, this method needs to invest a certain amount of cost and manpower in practical application. This method is generally used for the treatment of waste gas with relatively stable types and low content of harmful substances in waste gas, so as to facilitate the use of a targeted adsorbent.
Dry exhaust gas treatment is generally used organic gas activated carbon adsorption device, the principle is that activated carbon has a lot of micropores and a large specific surface area, depending on molecular gravity and capillary action, can make solvent vapor and volatile substances adsorbed on the surface, and according to the boiling point of different substances, with steam adsorbed substances precipitation. When steam is used as the desorption medium, the organic solvent vapor precipitated and water vapor condense together through the condenser and enter the separation bucket to recover the organic solvent after separation.
Two, laboratory waste water
1. Composition and harm of waste water
Waste water produced in the laboratory includes excess samples, standard curves and sample analysis residues, failed reservoir fluids and lotions, large amounts of washing water, etc. Almost all the routine analysis projects have different degrees of wastewater pollution. These wastes contain a wide range of components, including the most common organic matter, heavy metal ions and harmful microorganisms, as well as relatively rare cyanide, bacteria, toxic surface, various pesticide residues, drug residues, etc.
Wastewater containing excessive amounts of heavy metals, once discharged cleanly downstream, can contaminate large areas of water supply. Since the water contaminated with heavy metals is no different from normal water in color, smell and other aspects, once the water is used for irrigation, it will inevitably make the soil and crops become heavy metal pollution objects. People who eat crops grown on soil contaminated with heavy metals are vulnerable to poisoning by heavy metals.
2, waste water treatment methods
Generally, there are physical, chemical and biological methods. Physical method mainly uses physical action to separate suspended matter in wastewater; Chemical process mainly uses chemical reactions to treat dissolved substances or colloidal substances in wastewater; The biological process is to remove colloids and dissolved organic materials from wastewater. The above three basic treatment methods have their own characteristics and applicable conditions. When wastewater is discharged into surface water, the degree of treatment should be determined according to the discharge requirements. At the same time, it should be combined with the self-purification capacity of water body. Usually, the allowable load of water body is determined according to the indexes of harmful substances and dissolved oxygen, that is, the allowable concentration of water body.
A. Treatment of acid wastewater:
Alkaline wastewater was used for neutralization to make the PH value of mixed wastewater close to neutral. Neutralizing agent is added to acidic wastewater, which is filtered and neutralized through alkaline filter layer.
B. Treatment of alkaline wastewater:
The use of acidic waste water neutralization, in the alkaline substances put acid neutralizer: to the alkaline waste water into the flue gas (acid gas carbon dioxide or sulfur dioxide); Use carbon dioxide in water to neutralize alkaline wastewater.
C. Treatment of comprehensive waste liquid:
The process of water quality homogenization + neutralization filtration - neutralization coagulation - internal electrolysis - biological adsorption tank - sedimentation tank and clean water tank is adopted. In the wastewater treatment, in order to protect the on-line pH control system, neutralization filtration technology is adopted to ensure that the acid and alkali wastewater can reach the standard stably and save the reagent. The sludge is immobilized by combined fillers. Advanced ozone generator is used for disinfection in the disinfection treatment section. In sludge digestion, a pulse water distributor is used to distribute water to realize sludge reduction. The process can decompose complex organic matter and stabilize the effect of chemicals produced in the experimental wastewater. And the process operation cost is low, management through reasonable layout, as far as possible to reduce the area; Make a good green design and make a reasonable plan for the sewage station, so that it will become a landscape in the center of the laboratory.
D. Treatment of special wastewater:
All waste water containing radioactive nuclide, should according to the half-life of nuclide length, divided into two kinds of short life and long life radioactive nuclide waste water, and shall be handled separately, long-life radioactive nuclide, and radioactive concentration and high waste water, waste water should be centralized, until after a certain number, purification process can be treated by purification method of a small amount of concentrate, Short life radionuclide wastewater can be treated by curing method, and should be treated by storage method; Wastewater containing radionuclides should be treated in accordance with the current Regulations on Radiation Protection. Wastewater from biosafety level 4 and biosafety level 3 laboratories must be disinfected. After treatment, sewage should meet the requirements of Hospital Sewage Discharge Standards.
Three, laboratory solid waste
Solid wastes generated in laboratories include excess samples, analytical products, consumed or broken laboratory supplies (e.g. glassware, gauze), residual or failed chemical reagents, etc. The composition of these solid wastes is complex, covering all kinds of chemical and biological pollutants, especially many expired and ineffective chemical reagents. A little careless treatment can easily lead to serious pollution accidents.
The treatment method of laboratory pollutants is to prevent the diffusion of laboratory pollution. The general treatment principles of pollutants are as follows: classified collection, storage, and centralized treatment respectively. Waste recycling, curing and incineration treatment should be adopted as far as possible, and appropriate methods should be selected for testing in practical work to reduce waste volume and pollution as far as possible. The discharge of waste shall comply with the relevant national environmental discharge standards