summary of deodorization methods in practical water treatment system
1. Deodorization methods
Deodorization methods have gone through a development process, from the initial water washing method to the microbial deodorization method with better effect. Common methods are: activated carbon adsorption, biological deodorization, plant liquid deodorization, high-energy ion deodorization and so on.
1.1 activated carbon adsorption method
Activated carbon adsorption technology has been used for refining and decoloring in pharmaceutical, chemical and food industries in China for many years. It has been used for industrial wastewater treatment since 1971s. Activated carbon adsorption has gradually become one of the main methods for odor treatment.
activated carbon is a very fine carbon particle with a large surface area, and there are even smaller pores-capillaries in the carbon particle. This kind of capillary has a strong adsorption capacity, and because of the large surface area of carbon particles, it can fully contact with gas (impurities). When these gases (impurities) touch the capillary, they are adsorbed and play a purification role.
adsorption is a slow process in which one substance adheres to the surface of another. Adsorption is an interface phenomenon, which is related to the change of surface tension and surface energy. The specific surface area and pore structure of activated carbon directly affect its adsorption capacity. When selecting activated carbon, it should be determined by experiments according to the properties of waste gas. In addition, ash also has an effect. The smaller the ash, the better the adsorption performance. The closer the size of adsorbate molecules is to the pore diameter of carbon, the easier it is to be adsorbed. The concentration of adsorbate also affects the adsorption capacity of activated carbon. In a certain concentration range, the adsorption capacity increases with the increase of adsorbate concentration. In addition, temperature and pH value also have influence. The adsorption capacity decreases with the increase of temperature and increases with the decrease of pH value. Therefore, low temperature and low pH value are beneficial to the adsorption of activated carbon.
in order to deodorize effectively, activated carbon with different properties is usually used, and activated carbon for adsorbing acidic substances, activated carbon for adsorbing alkaline substances and activated carbon for adsorbing neutral substances are arranged in the adsorption tower, and the odor is discharged from the adsorption tower after contacting with various activated carbons.
Characteristics of activated carbon deodorization:
1) The reaction is complete, and volatile organic compounds in waste gas can be almost completely removed;
2) The corresponding adsorbent can be selected according to the type of waste gas. At present, the commonly used adsorbents are activated carbon, activated carbon fiber, silica gel, diatomite, activated alumina, synthetic zeolite, etc.
3) For waste gas components with small gas volume and difficult treatment, such as polychlorinated biphenyls, impregnated adsorbents, such as potassium permanganate, can be used to impregnate carbon to achieve complete purification;
4) The adsorption and regeneration cycle of activated carbon is short;
5) Small floor space;
1.2 biofiltration deodorization
The biofiltration deodorization system utilizes microbial membranes attached to the surface of fiber fillers or porous fillers to adsorb and degrade odor molecules and convert them into nontoxic, harmless and tasteless simple materials molecules. Firstly, the odor is collected and transported to the humidification and heat preservation system, and after passing through the biofilter rich in microorganisms, the treated fresh gas is discharged into the atmosphere after adsorption and degradation.
The process of biological deodorization is mainly divided into the following stages:
(1) Gas-liquid diffusion stage: the chemicals in the odor are first transferred from gas phase to liquid phase through the gas/liquid interface of the filler;
(2) liquid-solid diffusion stage: the odor chemicals in the waste gas diffuse from the liquid phase to the biofilm of biological filler;
(3) biological oxidation stage: microorganisms in the biofilm formed on the surface of the biological filler oxidize the odor gas molecules, and at the same time, the biofilm will cause the diffusion and absorption of nutrients such as nitrogen or phosphorus and oxygen.
through the above three stages, biofiltration converts pollutants in waste gas into carbon dioxide, water, inorganic salts and minerals, so as to achieve the purpose of odor purification.
process characteristics:
1) wide application range, high removal rate
2) convenient operation and management, less maintenance
3) no need to use harmful chemicals, no secondary pollution after treatment
4) low operation cost and long service life
1.3 Deodorization of plant liquid
Deodorization of plant liquid is to extract juice from natural plants. These tiny droplets spread in space have large specific surface area and surface energy, and the liquid surface can effectively adsorb odorous molecules, and also change the structure of odorous molecules, weaken the chemical bonds in odorous molecules, increase their reactivity, and easily react with other molecules to generate non-toxic and odorless organic salts. For example, H2S can generate SO42- and H2O, and NH3 can generate N2 and H2O. Decompose and eliminate these volatile odors before they are emitted to the surrounding area.
after being diluted by the automatic proportional diluter, the plant liquid is transported to the nozzles arranged in the odor control area through the atomization control equipment and pipeline system, and atomized into fine mist with the particle size of 11-41 microns, which is uniformly dispersed in the field space of the control area. After the fine mist of the plant liquid contacts with odor molecules in the air, the odor is removed through a series of reactions such as absorption, nucleophilic addition, catalytic oxidation and combination.
Process features
1) Low power and low energy consumption.
2) complete equipment, with small floor space, small pipeline diameter and flexible pipeline arrangement, does not affect the operation of other facilities on site.
3) It can be applied to various areas such as open, closed and semi-closed.
4) High degree of automation, fully automatic operation, no need for special personnel to be on duty.
1.4 principle of high-energy ion deodorization
: the energy generated by ion tube discharge is absorbed by oxygen molecules in the air to generate "enhanced active oxygen", forming gaseous oxide mixtures such as oxygen free radicals, hydrogen free radicals, positive and negative oxygen ions (bipolar ions) and ozone. The oxide mixture has a very high chemical reaction ability and is easy to combine with oxidizable substances because it absorbs high electric energy and load, and can convert pollutants such as hydrocarbons and alcohols into odorless components such as CO2 and H2O. At the same time, reactive oxygen species can also destroy the internal cell structure of microorganisms (viruses, molds, yeasts and bacteria) and achieve the purpose of inactivation.
Process features:
1) Simple maintenance, which can treat pollutants and inactivate microorganisms at the same time;
2) The polluted air is not in direct contact with the oxygen ion generator, which avoids the danger of fire or even explosion caused by the contact of flammable and explosive components in the polluted air with electric sparks generated by high-voltage ionization components, and objectively ensures the long service life of the oxygen ion tube, a key component in the oxygen ion generator;
3) The mixed reaction zone of waste gas and ion air is specially designed, so that high-energy oxygen ion air can uniformly react with polluted air, thus achieving stable and optimal treatment effect.
1.5 several deodorization methods are as follows:
comparison project: deodorizing plant liquid with activated carbon biofilter; deodorizing with high-energy ion;
large investment and small investment;
high operating cost and high and low;
high system noise-low
low odor concentration-medium and low-high
little secondary pollution
. P > low maintenance rate, high and low
simple installation and debugging, complex and simple
simple operation, simple and simple
water treatment industry is the first media.