Method and principle of sewage treatment

Method Principle Edit broadcast

Common water treatment methods are:

(1) Sediment filtration method

(2) hard water softening method

(3) activated carbon adsorption method

(4) Deion method

(5) Reverse osmosis method

(6) ultrafiltration method

(7) distillation method

(8) ultraviolet disinfection method

(9) Biochemical law.

(10) Mixed ion exchange method

Catalytic electrolysis

The technology uses the micro-electrolytic filler filled in the micro-electrolytic equipment to produce "galvanic" effect to treat the wastewater without power. When the water is passed through, numerous "galvanic cells" with potential differences of up to 1.2V are formed in the device. The "galvanic cell" uses waste water as electrolyte, and electrolytic oxidation and reduction treatment of waste water is carried out by discharging current to achieve the purpose of degrading organic pollutants. The new ecology produced in the treatment process [.O], [H], [O], Fe2+, Fe3+, etc., can REDOX reactions with many components in the wastewater, such as destroying the chromophores or chromophores of the colored substances in the colored wastewater, and even breaking the chain to achieve degradation and decolorization; The generated Fe2+ is further oxidized to Fe3 +, and their hydrates have strong adsorbation-flocculation activity, especially after adding alkali to adjust the pH value, ferrous hydroxide and ferric hydroxide colloidal flocculants are formed, and their flocculation ability is much higher than that of ferric hydroxide colloidal hydrolyzed by general reagents. It can flocculate a large number of small particles, metal particles and organic macromolecules dispersed in the water. The process has the advantages of wide application range, good treatment effect, low cost, short treatment time, convenient operation and maintenance, low power consumption, and can be widely used in the pretreatment and advanced treatment of industrial wastewater. Application wastewater types: dye wastewater, coking wastewater, pharmaceutical wastewater, pesticide wastewater, resin wastewater, auxiliary wastewater, tannery wastewater, electroplating wastewater, papermaking wastewater, starch wastewater, garlic wastewater, landfill leachate and other industrial wastewater.

Anode: FE-2E →Fe2+ E (Fe/Fe2+) =0.44V

Cathode: 2H+ + 2e →H2 E(H+/ H2)=0.00V

When oxygen is present, the cathode reaction is as follows:

O2 + 4H+ + 4e → 2H2O E (O2)=1.23V

O2 + 2H2O + 4e → 4OH-E (O2/OH-) =0.41V

It is produced by multi-metal alloy fusion catalyst and high temperature microporous activation technology, which is a new type of non-plate micro-electrolytic filler. Acting on electroplating wastewater, COD can be effectively removed, chroma can be reduced, biodegradability can be improved, the treatment effect is stable and durable, and the phenomenon of filler passivation and hardening can be avoided during operation. The filler is an important guarantee for the continuous action of micro-electrolysis reaction, and brings new vitality to the current treatment of electroplating wastewater.

Mechanical treatment

Mechanical (level 1) treatment section includes grille, sand settling tank, initial settling tank and other structures, to remove coarse particles and suspended matter for the purpose of treatment, there are two methods, generally through the physical method to achieve solid-liquid separation, the separation of pollutants from the sewage, which is the universal sewage treatment method. Mechanical (primary) treatment is essential for all wastewater treatment processes (although some processes sometimes omit the primary sedimentation tank), and the typical removal rates of BOD5 and SS for municipal wastewater primary treatment are 25% and 50%, respectively. In biological phosphorus and nitrogen removal wastewater treatment plants, aerated sand sedimentation tanks are generally not recommended to avoid the removal of rapidly degrading organic matter. In the case that the water quality characteristics of the original sewage are not conducive to phosphorus and nitrogen removal, the setting of the initial sedimentation and the setting method should be carefully analyzed and considered according to the subsequent process of the water quality special injection, so as to ensure and improve the influent water quality of the subsequent process such as phosphorus and nitrogen removal. Another method is the application of chemical treatment, the application of flocculant will be used to flocculate the damaged metal precipitation.

Sewage biochemistry

Sewage biochemical treatment is A secondary treatment, to remove non-sinkable suspended matter and soluble biodegradable organic matter as the main purpose, its process composition is diverse, can be divided into activated sludge method, AB method, A/O method, A2/O method, SBR method, oxidation ditch method, stabilization pond method, land treatment method and other treatment methods. Most municipal sewage treatment plants have adopted the activated sludge process. The principle of biological treatment is to complete the decomposition of organic matter and the synthesis of biological organisms through biological action, especially the role of microorganisms, and transform organic pollutants into harmless gas products (CO2), liquid products (water) and solid products rich in organic matter (microbial communities or biological sludge); The excess biological sludge is separated by solid and liquid in the sedimentation tank and removed from the purified sewage.

In the process of sewage biochemical treatment, the factors affecting microbial activity can be divided into two categories: substrate and environment:

The matrix includes nutrients, such as organic compounds dominated by carbon, namely nutrients such as carbon source material, nitrogen source and phosphorus source, and trace elements such as iron, zinc and manganese; In addition, it also includes some toxic and harmful chemicals such as phenols, benzene and other compounds, as well as some heavy metal ions such as copper, cadmium, lead ions and so on.

Environmental factors mainly include:

(1) Temperature. The influence of temperature on microorganisms is very extensive, although some types of bacteria are also active in high temperature environments (50 ° C ~ 70 ° C) and low temperature environments (-5 ~ 0 ° C), the most suitable temperature range for the growth of most microorganisms in sewage treatment is 20-30 ° C. In the appropriate temperature range, the physiological activity of the microorganism is vigorous, and its activity is enhanced with the increase of temperature, and the treatment effect is better. Beyond this range, the activity of microorganisms becomes worse, and the biological reaction process will be affected. In general, the maximum and minimum limits for controlling the reaction process are 35 ° C and 10 ° C respectively.

(2) The bacterial micelle disintegrated, and the treatment effect deteriorated sharply.

(3) Dissolved oxygen. For aerobic biological reactions, it is important to maintain a certain concentration of dissolved oxygen in the mixture. When the dissolved oxygen in the environment is higher than 0.3mg/l, both facultative and aerobic bacteria perform aerobic respiration. When the dissolved oxygen is less than 0.2-0.3mg/l and close to zero, the facultative bacteria are transferred to anaerobic respiration, most of the aerobic bacteria basically stop breathing, and some aerobic bacteria (most of them are filamentous bacteria) may also grow well, which often leads to sludge swelling after dominating the system. In general, the dissolved oxygen at the outlet of the aeration tank is appropriate to maintain about 2mg/l, and too high will increase energy consumption, which is economically uneconomical.

Among all the influencing factors, matrix factors and PH value are determined by the influent water quality, and the control of these factors mainly depends on daily monitoring and the strict implementation of relevant regulations and regulations. For the general municipal sewage, most of these factors will not constitute too much impact, and the parameters can be basically maintained within the appropriate range. The change of temperature is related to the climate, and it is difficult to control the temperature for the 10,000-ton municipal sewage treatment plant, especially when the activated sludge process is used, and it is not very feasible economically and engineering. Therefore, it is generally through the appropriate selection of design parameters to meet the processing requirements of different temperature changes in order to achieve the processing target. Therefore, the main goal of process control falls on the activated sludge itself and the environmental factors that can be changed by regulatory means, and the main task of control is to take appropriate measures to overcome the influence of external factors on the activated sludge system, so that it can continue to play a stable role.

The key to the process control of biological reaction system is the selection of control objects or control parameters, which is closely related to the processing technology or processing target.

As mentioned above, dissolved oxygen is a very important indicator parameter in the type and process of biological reaction, which can intuitively and quickly reflect the operation of the entire system, convenient operation and management, and simple installation and maintenance of instruments and meters, which is also the reason why the newly built sewage treatment plants in China have basically realized on-site and online monitoring of dissolved oxygen in the past decade.

Precipitation filtration

The purpose of sediment filtration is to remove suspended particulate matter or colloidal matter from the water source. These particulate matter, if not removed, can cause damage to other sophisticated filtration membranes used in dialysis water or even block waterways. This is the oldest and simplest water purification method, so this step is commonly used in the preliminary treatment of water purification, or if necessary, several more filters will be added to the pipeline to remove larger impurities. There are many types of filters used to filter suspended particulate matter, such as mesh filters, sand filters (such as quartz sand, etc.) or membrane filters. As long as the particle size is larger than the size of these holes, it will be blocked down. For ions dissolved in water, there's no stopping them. If the filter is not replaced or cleaned for too long, more and more particulate matter will accumulate on the filter, and the water flow and pressure will gradually decrease. People use the difference between the inlet water pressure and the outlet water pressure to determine the degree of blockage of the filter. Therefore, the filter should be timed to reverse to eliminate impurities accumulated on it, and the filter should be replaced within a fixed time.

Sediment filtration method also has a problem worth noting, because the particulate matter is constantly blocked and accumulated, these substances may have bacteria multiply here, and release toxic substances through the filter, causing pyrogen reaction, so it is necessary to replace the filter frequently, in principle, when the pressure difference between the water and the water rises to five times the original, it is necessary to replace the filter.

Hard water softening

Softening of hard water requires the use of ion exchange method, its purpose is to use cation exchange resin to exchange sodium ions in hard water calcium and magnesium ions, in order to reduce the concentration of calcium and magnesium ions in the water source. The softening reaction is as follows:

Ca2++2Na-EX→Ca-EX2+2Na+1

Mg2++2Na-EX→Mg-EX2+2Na+1

EX represents ion exchange resins that bind Ca2+ and Mg2+ to release the Na+ ions originally contained in them.

resin matrix contains sodium chloride. In the process of hard water softening, sodium ions will gradually be used up, and the softening effect of exchange resin will gradually decrease. At this time, it is necessary to make regeneration work, that is, adding a specific concentration of saline at a fixed time, usually 10%. The reaction is as follows:

Ca-EX2+2Na+ (concentrated brine) → 2NA-EX +Ca2+

Mg-EX2+2Na+ (concentrated brine) → 2NA-EX +Mg2+

If there is no cation softening in the process of water treatment, not only the reverse osmosis membrane will have calcium and magnesium deposits, which will reduce the efficacy and even destroy the reverse osmosis membrane, and the patient is also easy to get hard water syndrome. The hard water softener can also cause bacterial reproduction problems, so the device needs to have the function of backflushing, and after a period of time it is necessary to backflush once to prevent too many impurities from adsorbed on it. Another noteworthy problem is hypernatremia, because the softening and rereduction process of dialysis water is controlled by a timer, the normal reduction occurs mostly in the middle of the night, which is controlled by the valve, if there is a failure, a large amount of salt water will flood into the water source, resulting in the patient's hypernatremia. The automatic sodium ion exchanger uses the principle of ion exchange to remove calcium, magnesium and other scale ions from water. When the raw water containing hardness ions passes through the resin layer in the exchanger, the calcium and magnesium ions in the water are replaced with the sodium ions adsorbed by the resin, and the calcium and magnesium ions are adsorbed by the resin and the sodium ions enter the water, so that the water flowing from the exchanger is the softened water with the hardness removed.

Activated carbon

Activated carbon is made of wood, wood scraps, fruit cores, coconut shells, coal or petroleum residue and other substances at high temperatures, and needs to be activated by hot air or water vapor after being made. Its main function is to remove chlorine and chloramines and other dissolved organic substances with molecular weights between 60 and 300 daltons. The surface of the activated carbon is granular, the interior is porous, and there are many capillaries of about 1Onm~lA size in the pores, and the internal surface area of the activated carbon of 1g is as high as 700-1400m2, and the internal surface of these capillaries and the particle surface are where the adsorption is. The factors that affect the ability of activated carbon to remove organic matter are the area of activated carbon itself, the size of the hole and the molecular weight and Polarity of the organic matter to be removed. It mainly has the physical adsorption capacity to remove debris. When the adsorption capacity reaches saturation, excessive impurities will fall down and pollute the downstream water quality. Therefore, it is necessary to periodically use the way of thrust to remove the impurities on the adsorption.

If the adsorption capacity of this activated carbon filter is significantly reduced, it must be updated. Measuring the difference in TOC concentration (or the difference in the number of bacteria) between inlet and outlet is one of the bases for considering the replacement of activated carbon. Some reverse osmosis membranes have poor tolerance to chlorine, so activated carbon should be treated before reverse osmosis, so that chlorine can be effectively adsorbed by activated carbon, but the bacteria adsorbed by the holes on activated carbon are easy to multiply and grow, and the efficacy of activated carbon is limited for the removal of organic matter with large molecules, so the reverse osmosis membrane must be reinforced in the back.

Deion process

The purpose of the deion method is to remove inorganic ions dissolved in water, and the same as the hard water softener, also uses the principle of ion exchange resin. Two resins are used here - cation exchange resins and anion exchange resins. Cation exchange resin uses hydrogen ions (H+) to exchange cations; The anion exchange resin uses hydroxide ions (OH-) to exchange anions, and hydrogen ions and hydroxide ions combine to form neutral water, the reaction equation is as follows:

M+x+xH-Re→M-M-Rex+xH+1

A-z+zOH-Re→A-Rez+zOH-1

The M+x cations in the above formula, the electric price number of x, the hydrogen ion exchange of H-Re on the cation resin of M+x cations, the anion of A-z, the electric price number of z, the OH- ions are released after the combination of A-z and anion exchange resin. H+ ions combine with OH- ions to form neutral water.

After the adsorption capacity of these resins is exhausted, they also need to be reduced, and cation exchange resins need strong acids to reduce; Anions, on the other hand, require a strong base to reduce. The adsorption capacity of cation exchange resin for various cations is different, and their strength and relative relationship are as follows:

Ba2+>Pb2+>Sr2+>Ca2+>Ni2+>Cd2+>CU2+>Co2+>Zn2+>Mg2+>Ag1+>Cs1+>K1+>NH41+>Na1+>H1+

The affinity strength of anion exchange resin with each anion is as follows:

S02-4+>I->NO3->NO2->Cl->HCO3->OH->F-

If the anion exchange resin is exhausted and not reduced, the weakest fluorine will gradually appear in the dialysis water, causing chondrosis, osteoporosis and other bone diseases. If the cation exchange resin is exhausted, hydrogen ions will also appear in the dialysis water, resulting in an increase in the acidity of the water, so whether the deion function is effective needs to be monitored from time to time. It is generally judged by the resistivity or conductivity of the water. The ion exchange resins used in deionization can also cause bacteria to multiply and cause bacteremia, which is worth noting.

Reverse osmosis

Reverse osmosis method can effectively remove inorganic matter, organic matter, bacteria, pyrogen and other particles dissolved in water, is the most important part of the treatment of dialysis water. To understand the principle of "reverse osmosis", we must first explain the concept of "osmosis". The so-called penetration refers to the separation of two different concentrations of solution with a semi-permeable membrane, in which the solute can not penetrate the semi-permeable membrane, then the water molecule with a lower concentration will pass through the semi-permeable membrane to reach the other side with a higher concentration, until the concentration on both sides is equal. Before the balance is reached, you can gradually apply pressure on the higher concentration side, then the aforementioned water molecule movement state will temporarily stop, at this time the required pressure is called "osmotic pressure", if the applied force is greater than osmotic pressure, then the water movement will go in the opposite direction. That is, from the high concentration side to the low concentration side, this phenomenon is called "reverse osmosis". The purification effect of reverse osmosis can reach the level of ions, and the exclusion rate of monovalentions can reach 90%-98%. divalent ions (divalent ions) can reach about 95% to 99% (to prevent the passage of substances with molecular weight greater than 200 Dalton).

The semi-permeable membrane materials commonly used in reverse osmosis water treatment are cellulosic, aromatic polyamides, polyimide or polyfuranes, etc., and its structural shape is spiral wound. hollow fiber type and tubular type, etc. The advantage of cellulose film in these materials is high chlorine resistance, but under alkaline conditions (pH ≥8.0) or in the presence of bacteria, the service life will be shortened. The disadvantage of polyamide is its poor tolerance to chlorine and chloramines.

If there is no pre-treatment before reverse osmosis, there is easy to accumulate dirt on the osmosis membrane, such as calcium, magnesium, iron plasma, resulting in the decline of reverse osmosis function; Some membranes (such as polyamide) are easily destroyed by chlorine and chloramines, so pre-treatment such as activated carbon and softener should be used before reverse osmosis membranes. Reverse osmosis although the price is higher, because the aperture of the general reverse osmosis membrane is about l0A below, it can exclude bacteria, viruses and pyrogen and even various dissolved ions, so it is best to prepare this step in the preparation of hemodialysis release water.

The debugging of reverse osmosis system is very important. We can grasp it from the following aspects:

Operating condition

Pre-operation preparation

Trial run

Separation process

The common processes in reverse osmosis membrane separation process design are as follows:

This method is that after the material liquid enters the membrane component, the concentrated liquid and the produced water are continuously drawn out, and the recovery rate of water in this way is not high, and the industrial application is less. The other form is a one-stage circulating process, which is to return a part of the concentrated water to the feed liquid tank, so that the concentration of the concentrated solution continues to increase, so the water production is large, but the water quality is reduced.

When reverse osmosis is used as a concentration process, when a concentration does not meet the requirements, this multi-step method can be used, which can reduce the volume of concentrated liquid and increase the concentration, and increase the water production accordingly.

When the salt removal rate of seawater requires the reduction of NaCl from 35,000 mg/L to 500mg/L, the salt removal rate is required to be as high as 98.6%. If the first level is not reached, it can be divided into two steps. That is, 90% of NaCl is removed in the first step, and 89% of NaCl is removed from the water in the second step, which can meet the requirements. If the salt removal rate of the membrane is low, and the water permeability is high, the two-step method is more economical, and the service life of the membrane can be improved when it is operated under low pressure and low concentration.

In this process, the first level of concentrated liquid is used as the feed liquid of the second level, and the second level of concentrated liquid is used as the feed liquid of the next level, at this time, because all levels of water are directly discharged to the body, so with the increase of the water recovery rate, the volume of concentrated liquid is reduced and the concentration is increased. In order to ensure a certain flow rate of the liquid and control the concentration polarization, the number of membrane components should be gradually reduced.

ultrafiltration

Ultrafiltration is similar to reverse osmosis in that it also uses a semi-permeable membrane, but it cannot control the removal of ions due to the large pore size of the membrane, about 10-200A. Only bacteria, viruses, pyrogen and particles can be excluded, and water-soluble ions cannot be filtered. The main function of the ultrafiltration process is to act as a pre-treatment of the reverse osmosis process to prevent the reverse osmosis membrane from being contaminated by bacteria. It can also be used in the final step of water treatment to prevent upstream water from being contaminated by bacteria in the pipeline. Generally, the difference between the inlet water pressure and the outlet water pressure is used to determine whether the ultrafiltration membrane is effective, similar to activated carbon, usually the backwash method is used to remove impurities attached to it.

Distillation method

Distillation is an ancient but also effective water treatment method, it can remove any non-volatile impurities, but can not exclude volatile pollutants, it requires a large storage tank to store, the storage tank and the transmission pipe is an important cause of pollution, hemodialysis water does not need to be treated in this way.

Ultraviolet disinfection

Its bactericidal mechanism is to destroy the life genetic material of bacterial nucleic acid, so that it cannot reproduce, and the most important reaction is that the pyrimidine base within the nucleic acid molecule becomes dimer. It is generally the use of low pressure mercury discharge lamps (germicidal lamps) artificial 253.7nm wavelength of ultraviolet energy. The principle of the ultraviolet germicidal lamp is the same as that of the fluorescent lamp, but the lamp tube is not coated with fluorescent substances, and the material of the lamp tube is quartz glass with high ultraviolet penetration. The general ultraviolet device is divided into irradiation type, soaking type and running type according to the use.

The ultraviolet light used in hemodialysis dilution water is placed on the pipe between the storage tank and the dialysis machine, that is, all dialysis water must be irradiated with ultraviolet light before use to achieve complete sterilization. Pyo and coliform bacteria were the most sensitive to ultraviolet light. In contrast, subtilis spores were more tolerant. Because UV disinfection is safe, economical, less selective to strains, and the water quality does not change, this method has been widely used, such as drinking water on ships. The Igora bacteria in the water, Basra bacteria, Salmonella and so on all killed, can dive into the center of the water 360 degrees sterilization, the effect is equal to three times the surface sterilization lamp. It can eliminate the algae in the water, the effect is remarkable, easy to use, ultraviolet bactericidal lamp is suitable for: filtration of various sizes of fishing grounds, water treatment, large and small pools, swimming pools, hot springs. The bactericidal efficiency can reach 99%-99.99%.

Ultraviolet water treatment technology - sterilization

Ultraviolet sterilization is mainly the use of 254 nanometer wavelength ultraviolet light. This wavelength of ultraviolet light, even at a tiny dose of ultraviolet radiation, can destroy the core of a cell's life-DNA, thus preventing cell regeneration, loss of regenerative ability to render bacteria harmless, thus achieving sterilization effect. Like all other UV application technologies, the size of the system depends on the intensity of the UV (the intensity and power of the irradiator) and the exposure time (the length of time that water, liquid, or air is exposed to the UV).

Ultraviolet water treatment technology - ozone elimination

In industrial production, ozone is often used to disinfect and purify water bodies. However, due to the strong oxidation capacity of ozone, the remaining ozone in the water may affect the next process if it is not removed, so the remaining ozone in the water must be removed before the ozonated water enters the main process. Ultraviolet light at a wavelength of 254 nanometers is very effective at destroying the remaining ozone, which can be broken down into oxygen. Although the scale required varies from system to system, a typical ozone elimination system typically requires about three times as much UV radiation as a traditional sterilization system.

Uv water treatment technology - reducing total organic carbon

In many high-tech and laboratory installations, organic matter can hinder the production of high purity water. There are many ways to remove organic matter from water, the more common methods include the use of activated carbon and reverse osmosis. Shorter wavelengths of ultraviolet light (185 nm) can also effectively reduce total organic carbon. Shorter wavelengths of ultraviolet light have more energy and are therefore able to break down organic matter. Although the reaction process of ultraviolet oxidation of organic is very complex, the main principle of ultraviolet water treatment technology is to oxidize organic matter into water and carbon dioxide by producing free hydrogen and oxygen with strong oxidation capacity. Like ozone removal systems, this organic carbon-degrading UV system emits three to four times as much UV radiation as conventional disinfection systems.

Ultraviolet water treatment technology - Degradation of residual chlorine in municipal water treatment and water supply systems, chlorination disinfection is very necessary. However, in the industrial production process, in order to avoid adverse effects on the product, the removal of residual chlorine in the water is often necessary for pre-treatment. The method of eliminating residual chlorine is based on activated carbon bed and chemical treatment. The disadvantage of activated carbon water treatment is that it requires continuous regeneration and often encounters the problem of bacterial growth. Both 185nm and 254nm wavelengths of ultraviolet light have been shown to effectively break the chemical bonds of residual chlorine and chloramines. Although it requires huge ultraviolet energy to play a role, the advantage of ultraviolet water treatment technology is that this method does not need to add any drugs to the water, does not need to store chemicals, is easy to maintain, and at the same time has the role of sterilization and removal of organic matter.

Features:

1, pulsed ultraviolet sterilization method, wide spectrum energy, eliminate the phenomenon of microbial light resurrection

2, the use of stainless steel shell, long service life

3, the lamp can be manually cleaned or automatic mechanical cleaning

4, automatic control system, intelligent operation

Acoustic processing

Ultraviolet light with wavelengths from 200 to 300nm has bactericidal effects. UVC radiation has a strong bactericidal power. It is absorbed by DNA and destroys its structure, thereby removing the activity of living cells. Microorganisms such as viruses, bacteria, yeasts, and fungi are rendered harmless within seconds by UV lamps. As long as the radiation intensity is high enough, UV sterilization is a reliable and environmentally friendly method, as no chemical additives are required. In addition, microbes cannot produce antibodies to ultraviolet light.

For UV sterilization, a low-pressure mercury lamp with a single chromatographic emission wavelength of 254 nm can be used, or a medium-pressure mercury lamp with a broadband spectrum covering the entire range from 200 to 300 nm can be used, or an excimer lamp with only a wavelength of 222 nm can be used.

The advantages of century source UV lamp for water treatment:

It has no effect on taste or smell;

No need to add chemicals;

No environmental pollution;

Short radiation time;

Effective against chlorine-resistant pathogens;

Easy to operate;

The maintenance requirement of the process is small;

Extremely low operating costs.

Biochemical process

Biochemical water treatment method uses various bacteria and microorganisms existing in nature to decompose organic matter in wastewater into harmless substances, so that wastewater can be purified. Biochemical water treatment methods can be divided into activated sludge method, biological membrane method, biological oxidation tower, land treatment system, anaerobic biological water treatment method.

Biochemical water treatment process:

Raw water → grid → regulating tank → contact oxidation tank → precipitation site → filtration → disinfection → effluent.

1, activated sludge water treatment method

(1) Pure oxygen aeration method. The first pure oxygen aerated sewage treatment plant was built in the United States in 1968. Due to the decreasing cost of producing oxygen, pure oxygen aeration method is widely used.

(2) Deep-water aeration method. Increasing the depth of the aeration pool can increase the pressure of the pool water, thus improving the solubility of oxygen in the water, and the dissolution rate of oxygen should also be increased. Therefore, the dissolved oxygen in the deep-water aeration pool is higher than that in the ordinary aeration pool, and the depth of the pool is generally increased from the original 4 m to about 10 m.

(3) Jet aeration method. The mixed liquid composed of sewage and sludge passes through the jet machine, and the negative pressure is generated due to the high-speed jet, so that a large amount of air is inhaled, and the air is fully in contact with the mixed liquid, which improves the oxygen absorption rate of the sewage, so that the sewage treatment efficiency is improved.

(4) Adding chemical coagulant and activated carbon method. Adding chemical coagulant and activated carbon to the aeration tank of activated sludge process is equivalent to carrying out physical and chemical treatment at the same time of biochemical treatment. Activated carbon can also be used as a carrier of microorganisms and has the role of assisting solid settlement, the removal rate of BOD and COD is increased, and the water quality is purified.

(5) Biological contact oxidation method. This is a new sewage treatment method with the characteristics of activated sludge method and biological filtration method, which replaces the general aeration tank with contact oxidation tank and the common sedimentation tank with contact sedimentation tank.

(6) Pipeline aeration. This method is to aerate the activated sludge in the pressure pipeline and transport it over a longer distance. With less equipment, investment costs and operating costs can be reduced.

Aeration: that is, exhaust flow aeration, the use of aeration fans to continuously pump compressed air into the wastewater to ensure that there is a certain amount of dissolved oxygen in the water to maintain the life activities of microorganisms, decompose organic matter in the water, and achieve the purification effect of water treatment.

2, biofilm water treatment method

(1) Biological filter: The wastewater flows through the biofilm growing on the surface of the filter material, through the exchange of materials and biochemical effects between the two sides, so that the organic matter in the wastewater degradation, to achieve the purpose of water treatment purification.

(2) Biological turntable: composed of a number of closely spaced disks fixed on a horizontal axis, and a layer of biofilm is grown on the surface of the rotating disk to achieve the effect of water treatment and purification.

Biological contact oxidation: All the fillers for microbial colonization are immersed in the wastewater, and mechanical equipment is used to fill the air into the wastewater, so that the organic matter in the wastewater is degraded to purify the wastewater.

3, land treatment system (1) Land perfiltration: the use of microorganisms in the soil membrane and plant roots to purify pollutants for domestic sewage treatment, while the use of sewage water, fertilizer to promote the growth of crops, grass, trees.

(2) Sewage irrigation: The main purpose of this water treatment method is irrigation to make full use of the purified sewage.

4, anaerobic biological water treatment method: the use of anaerobic microorganisms to decompose organic matter in sewage to achieve the purpose of water treatment and purification, while producing methane gas, CO2 and other gases.

Ion exchange

Mixed bed is short for mixed ion exchange column, which is designed for ion exchange technology. The so-called mixed bed is to mix a certain proportion of positive and anion exchange resin into the same exchange device to exchange and remove ions in the fluid. Because the specific gravity of the Yang resin is larger than that of the Yin resin, the Yin resin is on the top of the Yang resin in the mixed bed. A prajna, Yin resin filling ratio of 1:2, there are also filling ratio of 1:1.5, can be considered according to different resin choices. Mixed bed is also divided into in vivo synchronous regeneration mixed bed and in vitro regeneration mixed bed. The synchronous regenerative mixed bed is carried out in the operation and the whole regeneration process in the mixed bed, and the resin does not move out of the equipment during regeneration, and the positive and negative resin are regenerated at the same time, so the auxiliary equipment is less and the operation is simple.

The equipment of mixed bed treatment process includes mixed ion exchanger and in vitro regeneration equipment. In vitro regeneration equipment mainly includes resin separator, Yin (Yang) resin regenerator, resin storage tower, hybrid resin tower and acid base regeneration equipment.

Equipment advantage

1. The effluent water quality is excellent, and the effluent pH value is close to neutral.

2, the effluent water quality is stable, and the change of short-term operating conditions (such as influent water quality or composition, running velocity, etc.) has little impact on the effluent water quality of the mixed bed.