Water is not only the source of life, it is extremely important for human beings, and pollution is so powerful. Poor water quality for long-term drinking, light can lead to poor physical fitness and natural weakening of resistance, and heavy cause cancer. Therefore, we should prevent and protect water resources, rationally and make good use of water.
Today, Xiaoqi has done some summary of water treatment knowledge for everyone.
Mom said that those who love to learn are good children.
Water treatment knowledge Q&A summary
1. What is water self-purification?
Self-purification of water bodies: Polluted rivers through physical, chemical, biological and other aspects of the action, so that the concentration of pollutants reduced or transformed, the water body returned to its original state, or from the initial exceeding the water quality standards to equal the water quality standards.
2. What are the basic methods of sewage treatment?
The basic method of sewage treatment: it is to use various means and technologies to separate and remove the polluting substances in the sewage, recycle them, or convert them into harmless substances to purify the sewage. It is generally divided into water treatment and sewage treatment.
3. What are the current sewage treatment technologies?
Modern sewage treatment technology, according to the principle of action, can be divided into physical treatment, chemical treatment, biological treatment.
4. Five water measurement indicators
Biochemical oxygen demand (BOD): refers to the amount of oxygen required to degrade organic matter due to the action of microorganisms under aerobic conditions. It is a comprehensive indicator that sewage is polluted by organic matter.
Theoretical Oxygen Demand (thOD): The theoretical oxygen demand of an organic substance in water. It usually refers to the theoretical value of the complete oxidation of carbon and hydrogen in organic matter to the oxygen required for carbon dioxide and water (that is, the oxygen demand calculated according to the complete oxidation reaction formula).
Total oxygen demand (TOD): refers to the amount of oxygen required by the substances in water that can be oxidized, mainly organic matter becomes a stable oxide during combustion, and the result is expressed as mg/L of O2.
Chemical Oxygen Demand (COD): Is a chemical measure of the amount of reducing substances in a water sample that need to be oxidized. The oxygen equivalent of wastewater, wastewater treatment plant effluent and contaminated water that can be oxidized by strong oxidants (generally organic matter).
Total organic carbon (TOC): Refers to the total amount of carbon contained in dissolved and suspended organic matter in a water body.
5. What is the use of biochemical treatment?
It is generally believed that sewage with a BOD/COD value greater than 0.3 is suitable for biochemical treatment.
6. What are the sanitary standards for drinking water?
Physical indicators of drinking water hygiene standards: color, turbidity, odor and taste.
7. What is eutrophication of water bodies?
Water eutrophication is a natural phenomenon that occurs in fresh water and causes the sudden overproliferation of algae due to the excessive content of nitrogen, phosphorus and potassium in the water body.
The main reason for the formation of eutrophication of water bodies is that nitrogen, phosphorus, potassium and other elements are discharged into surface water bodies with slow flow rates and long renewal cycles, so that aquatic organisms such as algae grow and multiply in large quantities, so that the speed of organic matter production far exceeds the rate of consumption, and the accumulation of organic matter in water bodies destroys the process of aquatic ecological balance.
8. What is dissolved oxygen?
Oxygen dissolved in water is called dissolved oxygen. The organisms and aerobic microorganisms in water bodies, the oxygen on which they depend for their survival is dissolved oxygen. Different microbiotics have different requirements for dissolved oxygen.
9. What is the basic method of modern sewage treatment?
10. What is the stability of colloids?
Stability of colloidal: refers to the characteristics of colloidal particles in water for a long time to maintain dispersion and suspension.
11. What is an electric bit?
Dynamic potential: The potential on the sliding surface of the colloid is the ζ potential.
12. How does the hydrophobic colloid form large particles?
For hydrophobic colloids, in order for colloids to form large particles through Brownian motion colliding with each other, it is necessary to reduce or eliminate the repulsive energy peak, and the way to reduce the repulsive energy peak is to reduce or eliminate the ζ potential of the particles.
13. What is the role of adsorption bridge?
Adsorption bridging refers to the adsorption and bridging of polymer substances and rubber particles.
14. What is the function of the grille?
The role of the grille: to intercept coarse suspended solids or floating impurities.
15. What are the main factors affecting the coagulation effect?
The main factors affecting the coagulation effect: water temperature, pH and alkalinity of water, concentration of suspended solids in water, and hydraulic conditions.
16. How many types of precipitation are there? What are the differences?
There are four types of sedimentation, which are:
Free precipitation: Particles are in a discrete state during the precipitation process, their shape, size, and quality are not changed, and the sinking speed is not disturbed, and they independently complete the precipitation process.
Disorderly sedimentation: During the precipitation process, the size, mass and sedimentation rate of particles increase with the increase of depth.
Crowded precipitation: The concentration of particles in the water is large, interfering with each other in the process of sinking, forming a clear interface between clear water and muddy water, and gradually moving downward.
Compressive precipitation: the concentration of particles in water is very high, during the precipitation process, the particles come into contact with each other and are mostly supported by the compress, and the gap between the lower particles is extruded.
17. According to the direction of water flow in the pool, what kinds of sedimentation tanks can be divided?
According to the different directions of water flow in the pool, the sedimentation tank can be divided into advection type, oblique flow type, spoke flow type and vertical flow type.
18. What is the law of impurity distribution in the filter layer?
Impurity distribution law in the filter layer: At the beginning stage of filtration, the filter material is relatively clean, the pores are also larger, the shear force of the water flow is small, the adhesion effect is stronger, at this time, the particles in the water are first intercepted by the surface filter material, with the prolongation of the filtration time, the impurities in the filter layer increase, the porosity gradually decreases, especially the surface fine filter material, the shear force of the water flow increases, the shedding effect is enhanced, and finally the particles on the adhesion are first shedding and moved to the lower layer and intercepted by the lower layer filter material.
The result is: under a certain filter head, the filtration speed will be sharply reduced, or the loss of the water head will reach the limit value at a certain filter speed, or when the mud film is cracked due to the uneven force on the surface of the filter layer, a large amount of water flows out of the crack, causing the impurity particles in the water to penetrate the filter layer and deteriorate the quality of the effluent.
19. What are the ways to improve filtration efficiency?
Ways to improve filtration efficiency: In order to change this situation and improve the fouling capacity of the filter layer, there is "anti-particle size" filtration, that is, along the direction of water flow, the particle size of the filter material is from large to small, due to the complex structure of the upstream flow and two-way flow filter, it is inconvenient to rinse and other reasons.
20. What is the composition of homogeneous filter media?
Homogeneous filter media composition: Homogeneous filter media refers to any cross-section in the depth direction of the entire filter layer, and the composition of the filter material and the average particle size are uniformly consistent, not that the particle size of the filter material is exactly the same.
21. What is the negative head phenomenon? What are the ways to avoid it?
Negative head phenomenon: During the filtration process, when the filter layer retains a large number of impurities, so that the loss of water head at a certain depth below the sand surface exceeds the water depth at that place.
The way to avoid negative water heads is to increase the water depth on the sand surface, or the outlet water of the filter is equal to or higher than the surface of the filter layer. This is the reason why siphon and valveless filters do not have a negative head.
22. How many ways is there for the backwashing water supply of ordinary fast filters?
There are two ways to supply backwash water in ordinary fast filters: flushing pumps and towers.
23. What is this chlorination?
When the organic matter in the water is mainly ammonia and nitride, after its actual chlorine demand is satisfied, the amount of chlorine is increased, the amount of residual chlorine is increased, but the latter grows slowly, after a period of time, the amount of chlorine is increased, the amount of residual chlorine decreases, and then the amount of chlorination increases, and the amount of residual chlorine rises, after this vertex, the free residual chlorine appears, and the effect of continuing chlorination disinfection is the best, that is, the vertex chlorination.
24. What are the systems of the activated sludge method?
The activated sludge method is composed of an aeration tank, a sedimentation tank, a sludge reflux, and a residual sludge removal system.
25. What is the sludge settlement ratio?
Sludge sedimentation ratio (SV%): refers to the aeration tank mixture, in a 1000ml cylinder to stand precipitation for 30min, the volume ratio of sedimented sludge to the mixed liquid (%).
26. What is the sludge index?
Sludge index (SVI): refers to the volume of each gram of dry sludge after the mixture at the outlet of the aeration tank has been settled for 30 minutes, measured in mL.
SVI value is too low, indicating that the mud particles are small and tight, inorganic substances, lack of activity and adsorption capacity; SVI value is too high, indicating that the sludge is difficult to settle and separate, that is, it is expanding or has expanded, the cause must be identified, and measures must be taken.
27. What is sludge expansion, disintegration, decay, floating and foam?
Sludge expansion: When the sludge deteriorates, the sludge is not easy to precipitate, the SVI value increases, the structure of the sludge is loose, the volume expands, the moisture content rises, the clarification liquid is less, and the color is also abnormal.
Sludge disintegration: the treatment of water quality is turbid, sludge turbidity, sludge coagulation is fine, the treatment effect becomes bad, etc. is the phenomenon of sludge disintegration.
Sludge corruption: In the secondary sedimentation tank, it is possible to produce anaerobic fermentation due to long-term retention of sludge, generating gas, resulting in the phenomenon of large sludge floating.
Sludge floating: the phenomenon of sludge floating in a block shape in the secondary sedimentation tank.
Foam problem: Foam is generated in the aeration tank, mainly due to the presence of a large number of synthetic washing or other foaming substances in the sewage.
28. What is the growth curve of activated sludge?
Activated sludge microorganisms are multi-species mixed populations, and their growth rules are more complex, but they can also be expressed by their growth curves. This curve expresses that when the environmental conditions such as temperature and dissolved oxygen meet the growth requirements of microorganisms, and there is a certain amount of initial microbial inoculation, the number of microorganisms proliferates and decays over time after a full dose of nutrients.
The change in the growth rate of activated sludge is mainly caused by the ratio of nutrients or organic matter to microorganisms (usually expressed in F/M), and the F/M value is also an important influencing factor of the degradation rate of organic substrates, oxygen utilization rate, agglomeration and adsorption performance of activated sludge.
There are four stages of the growth curve of activated sludge: the adaptation period, the logarithmic growth period, the deceleration growth period (the most biomass), and the endogenous respiration period (the best effect of treating water quality).
29. How many processes is the purification of activated sludge divided into?
Activated sludge purification wastewater is completed in three stages:
In the first stage, the wastewater is mainly purified by the adsorption of activated sludge. The adsorption is carried out very quickly, generally within 30 minutes, and the BOD5 removal rate can be as high as 70%. At the same time, it also has the effect of partial oxidation, but adsorption is the main role.
The second stage, also known as the oxidation stage. It is mainly to continue to decompose the organic matter that was adsorbed and absorbed in the pre-oxidation stage, while continuing to adsorb some residual dissolved substances.
The third stage is the slurry-water separation phase. In this phase, the activated sludge is separated by sedimentation in the second sedimentation tank. Both anabolic and catabolic microbials can remove organic contaminants from sewage, but the products are different.
30. What are the characteristics of the secondary sedimentation tank?
Characteristics of the secondary sedimentation tank: In terms of function, in addition to the separation of sludge water, it also carries out sludge concentration, and due to changes in water quality and water quantity, it is also necessary to temporarily store sludge.
31. What is a sewage slow infiltration system?
Slow infiltration of sewage is the function of purifying sewage by allowing sewage to slowly pass through the land due to natural infiltration filtration. It is suitable for soil with good water permeability and small evaporation and humid climate.
32. What is a sewage fast infiltration system?
Suitable for soils with very good permeability. Such as sandy soil, gravel sandy soil and so on. The sewage tank penetrates into the ground quickly after reaching the surface of the rapid infiltration field and eventually into the aquifer.
33. How many stages of anaerobic reaction? What are the differences?
The anaerobic reaction is divided into three stages:
The first stage is the decomposition of organic matter into fatty acid machine products under the action of hydrolysis and fermentation bacteria.
The second stage is the hydrogen-producing acetic acid, which is further converted into hydrogen, carbon dioxide and acetic acid under the action of bacteria.
The third stage is the methane fermentation stage (alkaline fermentation stage) through the action of two different groups of methanogens, one group converts hydrogen and carbon dioxide into methane, and the other group is acetic acid deactivation to produce methane.
34. What is two-phase digestion?
Two-phase digestion is to separate the acid-producing stage and methanogenic stage of anaerobic digestion of organic substrates.
35. What are the material components of the sludge?
The composition of the substances in the sludge can be divided into organic sludge and inorganic sludge.
According to the source of the sludge, it can be divided into primary sedimentation sludge, residual activated sludge, humus sludge, cooked sludge and chemical sludge.
36. What moisture does the sludge contain?
The water contained in the sludge is divided into 4 categories: pore water between particles, capillary water, sludge particle adsorption water and particle internal water.
Removal method: gravity, air flotation, centrifugation.
37. What is included in mechanical dehydration?
Mechanical dewatering: vacuum filtration dewatering, press filtration dewatering, rolling dewatering, centrifugal dewatering of sludge.
38. What is the purpose of sludge stabilization?
The purpose of sludge stabilization is to eliminate the odor emitted from the sludge and kill pathogenic microorganisms in the sludge.
39. What is adsorption?
The use of porous solids (such as activated carbon) or floc materials (such as polyferros) to adsorb toxic and harmful substances in wastewater on the surface of solids or flocs or micropores to achieve the purpose of purifying water quality, this treatment method is called adsorption treatment. The object of adsorption may be an insoluble solid substance or a dissolved substance.
40. What are the characteristics of physical adsorption and chemical adsorption?
Physical adsorption characteristics: adsorption heat is small, low temperature can be carried out, adsorption is reversible, adsorption is basically not selective.
Chemical adsorption characteristics: adsorption heat is larger, adsorption is irreversible, adsorption is selective.
41. What is resin density?
Resin density: Generally refers to the wet true density and wet apparent density two ways to express. Wet true density is related to the backwash strength of the resin layer, the rate of expansion, and the resin layering of the mixed and bunk beds, while the wet apparent density is used to calculate the amount of wet resin required for the ion exchanger.
42. What is the role of water filler?
The role of the water filler: it is the water droplets splashed off the water distribution system, which are splashed into tiny water droplets or water films after multiple splashes, increasing the contact area between water and air, prolonging the contact time, so as to ensure the good heat and quality exchange of air and water.
43. What is a volatile suspended solid of the mixture?
Mixed liquid volatile suspended solids (MLVSS) refers to the weight of volatile substances in the dry sludge contained in the biochemical tank mixture per volume, the unit is also mg/L, because it does not include inorganic substances in the activated sludge, so it can more accurately represent the number of microorganisms in the activated sludge.
44. Why is there residual sludge?
In the biochemical treatment process, microorganisms in the activated sludge continuously consume the organic matter in the wastewater.
Of the consumed organic matter, part of the organic matter is oxidized to provide the energy required for the life activities of microorganisms, and the other part of the organic matter is used by microorganisms to synthesize new cytoplasm, so that microorganisms reproduce and reproduce, and at the same time as microorganisms metabolize, some old microorganisms die, so the remaining sludge is produced.
45. What is needle charcoal technology?
Iron carbon treatment method, also known as iron carbon microelectrolysis method or iron carbon internal electrolysis method, it is an application form of metal iron treatment wastewater technology, using iron carbon method as a pretreatment technology to treat toxic and harmful, high-concentration COD wastewater has a unique effect.
46. Why should the effluent ph of the neutralizing sedimentation tank be adjusted to more than 9?
Iron charcoal effluent contains a large amount of ferrous sulfate, if not removed, will affect the growth and reproduction of microorganisms in the subsequent biochemical pool.
Therefore, we must use lime to raise the pH of wastewater from 5-6 to more than 9, so that the water-soluble ferrous sulfate is converted into insoluble ferrous hydroxide and calcium sulfate, and then precipitated by the method of coagulation and sedimentation to ensure that the wastewater entering the biochemical tank does not contain ferrous sulfate.
47. What are the types of air flotation?
Air flotation is divided into: dissolved air flotation method (divided into vacuum dissolved air flotation and pressurized dissolved air flotation), dissipation air flotation method, electrolytic air flotation method.
48. What is flocculation?
Flocculation is the addition of polymer coagulants to wastewater, and after the polymer coagulants are dissolved, polymers are formed. The structure of this polymer is a linear structure, one end of the line pulls a tiny particle, the other end pulls another tiny particle, in the distance between the two particles play a role in bonding bridge, so that the particles gradually become larger, and eventually form a large particle floc (commonly known as alum), accelerating particle settlement.
49. Why should wastewater be flocculated and adsorbed with poly-iron?
Polyferroic iron hydroxide flocs formed in the coagulation process has a good ability to adsorb organic matter in wastewater, experimental data show that after the polyferroferric flocculation adsorption of wastewater, it can remove about 10%-20% of the COD in the wastewater, which can greatly reduce the operating burden of the biochemical tank, which is conducive to the treatment of wastewater up to standard discharge.
In addition, the coagulation pretreatment with poly-iron can remove the trace substances that are toxic to microorganisms and inhibit the wastewater to ensure the normal operation of microorganisms in the biochemical tank. In many coagulants, the price of polyferroidal is relatively cheap (25-300 yuan / ton), so the treatment cost is relatively low, more suitable for the pretreatment of process wastewater.
50. Why are colloidal particles in wastewater not easy to precipitate naturally?
Many impurity suspensions with a specific gravity greater than 1 in wastewater, large particles, and suspended solids that are easy to settle can be removed by natural sedimentation, centrifugation and other methods.
However, the specific gravity of less than 1, tiny and even invisible suspended solid particles that cannot be seen by the naked eye are difficult to settle naturally, such as colloidal particles are 10-4-10-6mm size particles, which are very stable in water, and its sedimentation rate is extremely slow, and the settlement of 1m requires 200 years of cultivation.