GB18918-2002 is the "Pollutant Discharge Standard for Urban Sewage Treatment Plants", while GB8978-1996 is the "Integrated Wastewater Discharge Standard". The two are different concepts, and both have their own targets. The two cannot be mixed.
The latest standard of the "Comprehensive Wastewater Discharge Standard" has not been released by the country yet. The national comprehensive wastewater discharge standard still uses GB8978-1996.
Nanocrystal technology is the unique water softening technology of Pais water softener. According to neutral laboratory testing, the scale removal rate reaches 99.6, achieving a perfect water softening effect, which is better than anything previously known. All types of water softeners have excellent results. It is also a water softener that has been proven to be very effective without the addition of chemical ingredients. The technical principle of nanocrystals is TAC (Template Assisted Crys-tallization) technology, which is ion crystallization. It uses the high energy generated by the crystal nuclei on the surface of nanocrystal polymer spheres to package calcium, magnesium, and bicarbonate plasma in the water into nanoscale crystals. , when this kind of crystal grows to about 2 nanometers, it will automatically fall off into the water. Without calcium, magnesium, and bicarbonate ions in the water, there will be no scale. The purpose of sediment filtration is to remove suspended particulate matter or colloidal matter from the water source. If these particulate matter is not removed, it will cause damage to other precision filter membranes of dialysis water or even block the waterway. This is the oldest and simplest water purification method, so this step is often used in the preliminary treatment of water purification. 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. For ions dissolved in water, it cannot be blocked. If the filter has not been replaced or cleaned for a long time, more and more particulate matter will accumulate on the filter, and the water flow and water pressure will gradually decrease. People use the difference between the inlet water pressure and the outlet water pressure to judge the degree of blockage of the filter. Therefore, the filter must be backflushed regularly to remove impurities accumulated on it, and the filter must also be replaced within a fixed period of time.
There is another problem worth noting with the sediment filtration method. Because particulate matter is constantly blocked and accumulated, bacteria may breed on these materials and release toxic substances through the filter, causing a pyrogenic reaction. Therefore, the filter must be replaced frequently. In principle, when the pressure difference between the inlet and outlet water increases to five times the original value, the filter needs to be replaced. The softening of hard water requires the use of ion exchange. Its purpose is to use cation exchange resin to exchange calcium and magnesium ions in hard water with sodium ions, thereby reducing the concentration of calcium and magnesium ions in the water source. The softening reaction formula is as follows:
Ca2 2Na-EX→Ca-EX2 2Na 1
Mg2 2Na-EX→Mg-EX2 2Na 1
Where The EX represents ion exchange resin. These ion exchange resins combine Ca2 and Mg2 and release the Na ions originally contained in them.
The resin matrix contains sodium chloride. During the process of softening hard water, sodium ions will be gradually used up, and the softening effect of the exchange resin will gradually decrease. At this time, it is necessary to The work of reduction (regeneration) is to add a specific concentration of salt water at fixed intervals, usually 10. The reaction method is as follows:
Ca-EX2 2Na (concentrated salt water) → 2Na-EX Ca2
p>
Mg-EX2 2Na (concentrated salt water) → 2Na-EX Mg2
If there is no softening of cations during the water treatment process, there will be calcium and magnesium deposits not only on the reverse osmosis membrane, but also on the reverse osmosis membrane. Reduce efficacy or even damage the reverse osmosis membrane, and patients are also prone to hard water syndrome. Hard water softeners can also cause bacterial growth problems, so the equipment needs to have a backflush function. It must be backflushed after a period of time to prevent too many impurities from adsorbing on it.
Another issue worth noting is hypernatremia, because the softening and re-reduction process of dialysis water is controlled by a timer. Under normal circumstances, the reduction occurs mostly in the middle of the night. This is controlled by the *valve. If a failure occurs, a large amount of saline water will be released. Water will flow into the water source, causing the patient's hypernatremia. The fully automatic sodium ion exchanger uses the ion exchange principle to remove calcium, magnesium and other scaling ions in the 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. The resin adsorbs the calcium and magnesium ions and the sodium ions enter the water, so that the water flowing out of the exchanger Water is softened water with the hardness removed.
Activated carbon is made from wood, residual sawdust, fruit cores, coconut shells, coal or petroleum residues and other materials that are carbonized by carbonization at high temperatures. After being made, it needs to be activated with hot air or water vapor. . Its main function is to remove chlorine, chloramine and other dissolved organic substances with a molecular weight of 60 to 300 daltons. The surface of activated carbon is granular, and the interior is porous. There are many capillaries in the pores with a size of about 1Onm~1A. The internal surface area of ??1g of activated carbon is as high as 700-1400m2, and the inner surface of these capillaries and the surface of the particles are where the adsorption occurs. Factors that affect the ability of activated carbon to remove organic matter include the area of ??the activated carbon itself, the size of the pores, the molecular weight of the organic matter to be removed and its polarity (Polarity). It mainly relies on physical adsorption capacity to remove impurities. When the adsorption capacity reaches saturation, the adsorption Excessive impurities will fall down and pollute the water quality downstream, so backflushing must be used regularly to remove adsorbed impurities.
If the adsorption capacity of this activated carbon filter decreases significantly, it must be replaced. Measuring the TOC concentration difference (or bacterial count difference) between the incoming water and the outgoing water is one of the basis for considering the replacement of activated carbon. Some reverse osmosis membranes have poor tolerance to chlorine, so they must be treated with activated carbon before reverse osmosis so that chlorine can be effectively adsorbed by the activated carbon. However, bacteria adsorbed by the holes on the activated carbon are easy to multiply and grow. At the same time, for For the removal of organic matter with larger molecules, activated carbon has limited effectiveness, so a reverse osmosis membrane must be used to reinforce it behind. The purpose of the deionization method is to remove inorganic ions dissolved in the water. Like the hard water softener, it also uses the principle of ion exchange resin. Two types of resins are used here - cation exchange resin and anion exchange resin. Cation exchange resin uses hydrogen ions (H) to exchange cations; while anion exchange resin uses hydroxide ions (OH-) to exchange anions. Hydrogen ions and hydroxyl ions combine with each other 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
M x in the above formula It represents cations, x represents the electricity valence, M x cations exchange hydrogen ions with H-Re on the cation resin, A-z represents anions, and z represents the electricity valence. After A-z combines with the anion exchange resin, OH- ions are released. H ions combine with OH- ions to form neutral water.
These resins also need to be reduced after their adsorption capacity is exhausted. Cation exchange resins require strong acids to reduce; conversely, anions require strong bases to reduce.
Cation exchange resins have different adsorption capacities for various cations. Their strengths and relative relationships are as follows:
Ba2 gt; Pb2 gt; Sr2 gt; Ca2 gt; Ni2 gt; Cd2 gt; CU2 gt; Co2 gt; Zn2 gt; Mg2 gt; Ag1 gt; Cs1 gt; K1 gt; NH41 gt; Na1 gt; H1
The affinity strength between anion exchange resin and each anion is as follows:
S02-4 gt; I-gt; NO3-gt; NO2-gt; Cl-gt; HCO3-gt; OH-gt; F-
If the anion exchange resin is exhausted and no reduction, the fluorine with the weakest adsorption force will gradually appear in the dialysis water, causing rickets, osteoporosis and other bone diseases; if the cation exchange resin is exhausted, hydrogen ions will also appear in the dialysis water, This causes an increase in water acidity, so whether the deionization function is effective requires constant monitoring. Generally, it is judged by the resistivity or conductivity of water quality. The ion exchange resin used in the deionization method can also cause bacterial reproduction and cause bacteremia, which is worth noting. The reverse osmosis method can effectively remove inorganic substances, organic substances, bacteria, pyrogens and other particles dissolved in the water. It is the most important part of the treatment of dialysis water. Before understanding the principle of reverse osmosis, we must first explain the concept of osmosis. The so-called osmosis refers to the separation of two solutions of different concentrations by a semipermeable membrane. The solute cannot pass through the semipermeable membrane, so the water molecules on the side with a lower concentration will pass through the semipermeable membrane to the other side with a higher concentration. until the concentrations are equal. Before equilibrium is reached, pressure can be gradually applied to the side with higher concentration, and the aforementioned movement of water molecules will temporarily stop. The pressure required at this time is called osmotic pressure. If the applied force is greater than the osmotic pressure, When the pressure is high, the water moves 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 ion level. The rejection rate of monovalent ions can reach 90-98, while the rejection rate of divalent ions can reach about 95-99 (which can prevent molecular weight Materials larger than 200 Daltons pass through).
The commonly used semipermeable membrane materials for reverse osmosis water treatment include cellulosic membrane, aromatic polyamides, polyimide or polyfuranes, etc. As for its structural shape, there are spiral types ( spiral wound), hollow fiber type (hollow fiber) and tubular type (tubular), etc. As for the advantage of cellulose membrane among these materials, it has 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 chloramine.
If no pre-treatment is done before reverse osmosis, dirt will easily accumulate on the permeable membrane, such as calcium, magnesium, iron and other ions, resulting in a decline in reverse osmosis function; some membranes (such as polyamide) are easily It is destroyed by chlorine and chlorine ammonia, so there must be pre-treatment such as activated carbon and softener before the reverse osmosis membrane. Although reverse osmosis is more expensive, because the pore size of the general reverse osmosis membrane is about 10A or less, it can eliminate bacteria, viruses, pyrogens and even various dissolved ions, so it is best to prepare this step when preparing hemodialysis water. .
The debugging of the reverse osmosis system is particularly important.
We can master it from the following aspects: Operating conditions Preparation for test run before operation Separation process
The common processes in reverse osmosis membrane separation process design are as follows:
① 1 The stage-stage method is that after the feed liquid enters the membrane module, the concentrate and product water are continuously drawn out. This method has a low water recovery rate and has few industrial applications. Another form is the one-stage and one-stage circulation process, which returns part of the concentrated water to the feed tank. In this way, the concentration of the concentrated solution continues to increase, so the water production volume is large, but the water quality decreases.
② One-stage multi-stage method When reverse osmosis is used as the concentration process and one-time concentration cannot meet the requirements, this multi-step method can be used. In this way, the volume of concentrated liquid can be reduced and the concentration can be increased. Water production increases accordingly.
③Two-stage and one-stage method. When the salt removal rate of seawater is required to reduce NaCl from 35000 mg/L to 500mg/L, the salt removal rate is required to be as high as 98.6. If the first level cannot be reached, it can be divided into two stages. proceed step by step. That is, the first step is to remove NaCl 90, and the second step is to remove NaCl 89 from the effluent of the first step to meet the requirements. If the salt removal rate of the membrane is low and the water permeability is high, it is more economical to use the two-step method. At the same time, when operating at low pressure and low concentration, the service life of the membrane can be increased.
④Multi-stage reverse osmosis process In this process, the first-level concentrated liquid is used as the feed liquid for the second level, and the second-level concentrated liquid is used as the feed liquid for the next level. This Since the permeated water at each stage is directly discharged outside the body, the water recovery rate increases as the number of stages increases, and the volume of the concentrated liquid decreases and the concentration increases. In order to ensure a certain flow rate of the liquid and control concentration polarization at the same time, the number of membrane modules should be gradually reduced. Its bactericidal mechanism is to destroy the biological genetic material of bacterial nucleic acid, making it impossible to reproduce. The most important reaction is that the pyrimidine base in the nucleic acid molecule turns into a dimer. Generally, artificial 253.7nm wavelength ultraviolet energy is used using a low-pressure mercury discharge lamp (germicidal lamp). The principle of ultraviolet germicidal lamps is the same as that of fluorescent lamps, except that the inside of the lamp tube is not coated with fluorescent substances. The material of the lamp tube is quartz glass with high ultraviolet transmittance. Generally, UV devices are divided into irradiation type, immersion type and flow type according to their uses.
The ultraviolet rays used in hemodialysis dilution water are placed on the pipeline between the water storage tank and the dialysis machine. That is to say, all dialysis water must be irradiated with ultraviolet rays before use to achieve thorough Bactericidal effect. The most sensitive ones to ultraviolet rays are Pseudomonas aeruginosa and Escherichia coli; on the contrary, the ones that are more tolerant are Bacillus subtilis spores. Because the ultraviolet disinfection method is safe, economical, less selective for bacterial species, and the water quality will not change, this method has been widely used. For example, this disinfection method is often used for drinking water on ships. It can kill all Egola, Basella, Salmonella, etc. in the water. It can sneak into the center of the water for 360-degree sterilization. Its efficacy is three times that of the surface germicidal lamp. It can eliminate algae in water, has significant effect, and is easy to use. Ultraviolet germicidal lamp is suitable for: filtration of various sizes of fishing grounds, water treatment, large and small pools, swimming pools, and hot springs. The sterilization efficiency can reach 99-99.99.
Ultraviolet water treatment technology - sterilization
Ultraviolet sterilization mainly uses ultraviolet light with a wavelength of 254 nanometers. Ultraviolet light of this wavelength, even at a trace dose of ultraviolet radiation, can destroy the core of life of a cell - DNA, thereby preventing cell regeneration and losing the ability to regenerate, making bacteria harmless, thereby achieving a sterilization effect. Like all other UV application technologies, the size of this system depends on the intensity of the UV light (the strength and power of the irradiator) and the exposure time (the length of time the water, liquid, or air is exposed to UV light).
Ultraviolet water treatment technology--elimination of ozone
In industrial production, ozone is often used to disinfect and purify water bodies. However, because ozone has a strong oxidizing ability, the remaining ozone in the water may have an impact on the next process if it is not removed. Therefore, usually the ozone-treated water must be removed before entering the main process flow. Remove.
Ultraviolet light with a wavelength of 254 nanometers is very effective at destroying remaining ozone, breaking it down into oxygen. Although different systems require different sizes, generally speaking, a typical ozone elimination system requires about three times the amount of UV radiation as a traditional sterilization and disinfection system.
Ultraviolet 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 wavelength UV light (185 nanometers) is also effective in reducing total organic carbon. UV rays with shorter wavelengths have more energy and are therefore able to break down organic matter. Although the reaction process of ultraviolet oxidation of organic matter is very complicated, the main principle of ultraviolet water treatment technology is to oxidize organic matter into water and carbon dioxide by generating free hydrogen and oxygen with strong oxidizing ability. Like ozone scavenging systems, this UV system that degrades organic carbon emits three to four times more UV radiation than traditional disinfection systems.
Ultraviolet water treatment technology - degradation of residual chlorine In municipal water treatment and water supply systems, chlorine disinfection is very necessary. However, in the industrial production process, in order to avoid adverse effects on the product, removing residual chlorine from the water is often a necessary pre-treatment. The basic method for eliminating residual chlorine is activated carbon bed and chemical treatment. The disadvantages of activated carbon water treatment are that it requires constant regeneration and often encounters problems with bacterial growth. Both 185 nanometer and 254 nanometer wavelength ultraviolet rays have been proven to be effective in destroying the chemical bonds between residual chlorine and chlorine and ammonia. Although it requires a huge amount of ultraviolet energy to work, the advantage of ultraviolet water treatment technology is that this method does not require adding any drugs to the water, does not require the storage of chemicals, is easy to maintain, and also has the functions of sterilization and removal of organic matter.
Features:
1. Pulse ultraviolet sterilization method, wide spectrum and strong energy, eliminating the photoreactivation of microorganisms
2. Using all stainless steel shell, long service life Long
3. The lamp can be cleaned manually or automatically mechanically
4. Fully automatic control system and intelligent operation. Ultraviolet light with a wavelength from 200 to 300nm has a sterilizing effect. UVC radiation is highly germicidal. It is taken up by DNA and destroys its structure, deactivating living cells. Microorganisms such as viruses, bacteria, yeasts, and fungi are rendered harmless within seconds by UV light. As long as the radiation intensity is high enough, UV sterilization is a reliable and environmentally friendly method because no chemical additives are required. In addition, microorganisms cannot produce antibodies to UV rays.
When using ultraviolet sterilization, you can use a monochromatic low-pressure mercury lamp with an emission wavelength of 254 nm, or a medium-pressure mercury lamp with a broadband spectrum covering the entire range from 200 to 300 nm. You can also use Excimer lamps emit only a wavelength of 222 nm.
Advantages of Century Source UV lamps for water treatment:
No impact on taste and odor;
No need to add chemicals;
No environmental pollution;
Short irradiation time;
Effective against chlorine-resistant pathogens;
Easy to operate;
Maintenance requirements for the process Small;
Extremely low running costs. Biochemical water treatment methods use various bacterial microorganisms existing in nature to decompose and convert organic matter in wastewater into harmless substances, so that wastewater can be purified. Biochemical water treatment methods can be divided into activated sludge methods, biofilm methods, biological oxidation towers, land treatment systems, and anaerobic biological water treatment methods.
The process of biochemical water treatment method:
Raw water→grill→regulating tank→contact oxidation tank→sedimentation ground→filtration→disinfection→effluent.
1. Activated sludge water treatment method
(1) Pure oxygen aeration method. The first pure oxygen aeration sewage treatment plant was built in the United States in 1968. As the cost of producing oxygen continues to decrease, pure oxygen aeration methods are widely used.
(2) Deep water aeration method.
Increasing the depth of the aeration tank can increase the pressure of the water, thereby increasing the solubility of oxygen in the water and the dissolution rate of oxygen. Therefore, the dissolved oxygen in the water of a deep-water aeration tank is higher than that of an ordinary aeration tank. Generally, it is Increase the depth of the pool from the original 4 m to about 10 m.
(3) Jet aeration method. The mixed liquid composed of sewage and sludge passes through the ejector, and a negative pressure is generated due to the high-speed jet flow, so that a large amount of air is inhaled. The air fully contacts the mixed liquid, which increases the oxygen absorption rate of the sewage, thereby increasing the efficiency of the sewage treatment. improve.
(4) Add chemical coagulant and activated carbon method. Adding chemical coagulant and activated carbon to the aeration tank of the activated sludge method is equivalent to performing physical and chemical treatment at the same time as biochemical treatment. Activated carbon can also serve as a carrier of microorganisms and assist in solid sedimentation. It improves the removal rate of BOD and COD and purifies water quality. (5) Biological contact oxidation method. This is a new sewage treatment method that combines the characteristics of activated sludge method and biological filtration method. The contact oxidation tank replaces the general aeration tank, and the contact sedimentation tank replaces the commonly used sedimentation tank.
(6) Pipeline aeration. This method is to aerate the sewage with activated sludge in the pressure pipe and transport it over a long distance at the same time. With less equipment, both investment costs and operating costs can be reduced.
Aeration: that is, drainage aeration, using an aeration fan to continuously blow 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 and decompose organic matter in the water. To achieve the purification effect of water treatment.
2. Biofilm water treatment method
(1) Biological filter: Let the wastewater flow through the biofilm growing on the surface of the filter material, through material exchange and biochemical effects between the two sides , to degrade organic matter in wastewater and achieve the purpose of water treatment purification.
(2) Biological turntable: It consists of several closely spaced disks fixed on a horizontal axis. A layer of biofilm grows on the surface of the constantly rotating disks to achieve the effect of water treatment and purification. Biological contact oxidation: All fillers for microorganisms to inhabit are immersed in wastewater, and mechanical equipment is used to fill air into the wastewater to degrade organic matter in the wastewater to purify the wastewater. 3. Land treatment system (1) Land infiltration: Utilize the ability of microorganisms and plant roots in the soil film to purify pollutants to treat domestic sewage. At the same time, the water and fertilizer in the sewage are used to promote the growth of crops, pastures, and 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: Use anaerobic microorganisms to decompose organic matter in sewage to achieve the purpose of water treatment and purification, and at the same time produce methane, CO2 and other gases. If there are many particulate impurities in the water sample taken, after carbon tetrachloride extraction, there will be no obvious liquid separation layer between the water and the organic solvent, but it can still be filtered with dry filter paper because the dry filter paper It will quickly absorb the water droplets in the mixed layer, and will not affect the test results when carbon tetrachloride passes through the filter paper. Carbon tetrachloride vapor is poisonous to the human body. Inhalation should be avoided as much as possible during operation. Evaporation and drying must be performed in a fume hood.