50 water treatment knowledge summary

1, what is water from the net?

Self-purification of water bodies: The contaminated rivers, through their physical, chemical and biological functions, reduce or convert the concentration of pollutants and return the water bodies to the original state or from the initial water quality standards to water quality standards.

2, the basic methods of sewage treatment What?

Sewage treatment is the basic method: that is, using a variety of means and techniques to separate the sewage pollutants removed, recycled, or converted into harmless substances, so that the sewage purification. Generally divided into water treatment and sewage treatment.

3, what are the sewage treatment technology now?

Modern sewage treatment technology, according to the principle of action can be divided into physical treatment, chemical treatment, biological treatment.

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4, five water measurement

Biochemical oxygen demand (BOD): refers to under aerobic conditions, due to the role of microorganisms, the amount of oxygen required to degrade organic matter. Is a comprehensive indicator of sewage pollution by organic matter.

Theoretical oxygen demand (thOD): the theoretical oxygen demand of a certain organic matter in water. It usually refers to the theoretical value of the amount of oxygen required to completely oxidize carbon and hydrogen elements in an organic substance to carbon dioxide and water (ie, the oxygen demand calculated as the complete oxidation reaction).

Total Oxygen Demand (TOD): The amount of oxygen that can be oxidized in water. It is mainly the amount of oxygen required for organic matter to become a stable oxide upon combustion. The results are expressed in mg / L of O2.

Chemical Oxygen Demand (COD): The chemical measure of the amount of reducing material in a water sample that needs to be oxidized. Wastewater, the effluent from wastewater treatment plants, and the oxygen equivalent of substances (usually organic) that are oxidized by strong oxidants in contaminated water.

Total Organic Carbon (TOC): The total amount of dissolved and suspended organic carbon in water.

5, what situation using biochemical treatment?

It is generally accepted that sewage with a BOD / COD greater than 0.3 is suitable for biochemical treatment.

6, drinking water health standards is what?

Physical drinking water health standards of physical indicators: color, turbidity, smell and taste.

7, what is the water eutrophication?

Eutrophication is a natural phenomenon that occurs in freshwater and causes sudden algal hyperproliferation caused by the excessive content of nitrogen, phosphorus and potassium in water.

The eutrophication of water bodies is mainly caused by the discharge of nitrogen, phosphorus, potassium and other elements into the surface water bodies with slow flow rate and long renewal cycle, which make the algae and other aquatic organisms grow and multiply in a large amount, resulting in the organic matter far exceeding the consumption rate. In the accumulation of organic matter, undermining the process of aquatic ecological balance.

8, what is dissolved oxygen?

Oxygen dissolved in water is called dissolved oxygen. Water organisms and aerobic microorganisms, they depend on the survival of oxygen is dissolved oxygen. Different microorganisms on the dissolved oxygen requirements are not the same.

9, the basic method of modern sewage treatment is what?

Modern sewage treatment technology, according to the principle of action can be divided into physical treatment, chemical treatment, biological treatment.

10, what is colloidal stability?

Colloidal stability: refers to the colloidal particles in the water to maintain the characteristics of long-term dispersion of suspended state.

11, what is the electric bit?

Potential: the potential of the gel sliding surface is the zeta potential.

12, hydrophobic colloid how to form large particles?

For hydrophobic colloids, to make colloids collide with each other through Brownian motion to form large particles, the repulsive energy peak must be reduced or eliminated. The way to reduce the repulsive energy peak is to reduce or eliminate the zeta potential of colloidal particles.

13, adsorption bridge What is the role?

Adsorption bridging refers to the adsorption and bridging of macromolecular substances and micelles.

14, What is the role of grille?

The role of grille: to intercept coarser suspended matter or floating impurities.

15, the main factor affecting the coagulation effect is what?

The main factors affecting the coagulation effect: water temperature, water pH and alkalinity, water suspended solids concentration and hydraulic conditions.

16, there are several types of precipitation? What are

There are four types of sedimentation, they are:

Free settling: particles in the precipitation process was discrete state, its shape, size, quality are not changed, the speed of subsidence without interference, the completion of the precipitation process independently.

Turbulent sedimentation: particles in the precipitation process, its size, quality and sinking rate increases with depth increases.

Crowded precipitation: particles in the water in a larger concentration in the process of sinking interfere with each other in clear water and muddy water to form a clear interface between, and gradually move down.

Compressed Precipitation: The concentration of particles in water is high. During precipitation, the particles contact each other and are mostly supported by the compressive material. The gaps between the lower particles are squeezed out.

17, according to the direction of the pool water, sedimentation tanks can be divided into several?

According to the different direction of flow in the pool, sedimentation tanks can be divided into advection, oblique flow, radial flow, vertical flow.

18, the filter layer impurity distribution What is the law?

In the initial stage of filtration, the filter material is relatively clean, the pores are larger, the shear force of the water flow is smaller and the adhesion is stronger. At this time, the particles in the water are first intercepted by the surface filter material, When the filtration time is prolonged, the impurities in the filter layer increase and the porosity decreases. Especially for the fine filter material in the surface, the shear force of the water flow increases and the shedding effect increases. Finally, the adhered particles first fall off to the lower layer and are filtered by the lower layer Material interception.

The result is that under a certain filtration head, the filtration rate will decrease drastically or the loss of the head reaches a certain limit under a certain filtration rate, or when the mud membrane cracks due to uneven force on the surface of the filtration layer, a large amount of Flow from the cracks in the outflow, resulting in impurities in the water particles through the filter so that the water quality deterioration.

19, ways to improve the efficiency of filtration What?

In order to change this situation to improve the capacity of the filter layer has fouled, there has been “anti-particle size” filter, that is, along the flow direction, the filter size from big to small, due to the upstream and bi-directional flow filter Complex structure, inconvenience to flush and other reasons.

20, what is the composition of homogeneous filter?

Homogeneous filter composition: Homogeneous filter refers to the depth of the entire filter layer of any cross-section, filter media composition and average particle size uniformity, but not the same filter media particle size.

21, what is the negative head phenomenon? What are the ways to avoid?

Negative head phenomenon: During the filtration process, when the filter layer intercepts a large amount of impurities, the water head loss at a certain depth below the sand surface exceeds the water depth at the place.

Avoid negative head method is to increase the sand surface depth, or the filter outlet position equal to or higher than the filter surface. This is why siphon filters and valveless filters do not suffer from a negative head.

22, the general fast filter backwash water supply several ways?

Common fast filter backwash water supply there are two ways: flushing pumps and water towers.

23, what is this point of chlorination?

When the main organic matter in water is ammonia and nitrides, the actual amount of chlorine is satisfied, the amount of chlorination increases and the amount of residual chlorine increases, but the latter increases slowly. After a period of time, the amount of chlorination increases but the amount of residual chlorine decreases. The amount of chlorination increased, the amount of residual chlorine increased, the free chlorine after the turning point appears to continue the best chlorination disinfection, the turning point chlorination.

24, Activated Sludge Act which system?

Activated sludge method is aeration tank, sedimentation tank, sludge return, the remaining sludge removal system.

25, what is the sludge settlement ratio?

Sludge sedimentation ratio (SV%): refers to the mixture of aeration tank, standing precipitation in a 1000ml cylinder 30min, precipitated sludge and the volume ratio of the mixture (%).

26, what is the sludge index?

Sludge index (SVI): refers to the outlet of the aeration tank after standing precipitation 30min, the volume per gram of dry sludge in ml.

The value of SVI is too low, indicating that the mud is small and close, with many inorganic substances, lack of activity and adsorption capacity. If the SVI value is too high, the sludge is difficult to settle and is about to expand or expanded. Therefore, we must identify the cause and take measures.

27, what is the sludge expansion, disintegration, corrosion, floating and foam?

Sludge expansion: When the sludge degenerates, the sludge is not easy to precipitate, the SVI value is increased, the structure of the sludge is loose, the volume is expanded, the water content is increased, the clear liquid is less and the color is also changed.

Sludge disintegration: the quality of treated water is turbid, sludge densification is finer, the treatment effect is worse, and so is the phenomenon of sludge disintegration.

Sludge sludge: in the secondary sedimentation tank may be due to long-term sludge stagnation and produce anaerobic fermentation, the formation of gas, which appeared floating on the phenomenon of bulk sludge.

Sludge floating: sludge in the secondary sedimentation tank was lumpy phenomenon.

Foam Problem: Foam in the aeration tank is mainly due to the large amount of synthetic washes or other foaming substances present in the effluent.

28, what is the growth curve of activated sludge?

Activated sludge microorganisms are multi-species mixed population, the growth of more complex rules, but also can use its growth curve that certain laws. The curve is expressed in the temperature and dissolved oxygen and other environmental conditions to meet the growth requirements of microorganisms, and a certain amount of initial microbe inoculation, a full dosing of nutrients, the number of microbial proliferation and decay with time.

Activated sludge growth rate changes are mainly nutrients or organic matter and the ratio of microorganisms (usually F / M said) caused by the F / M value is the organic substrate degradation rate, oxygen utilization rate, the agglomeration of activated sludge, adsorption properties The important influence factor.

Activated sludge growth curve of the four stages: adaptation, logarithmic growth phase, slow growth phase (biomass), endogenous respiratory phase (the best treatment of water quality).

29, Activated sludge purification is divided into several processes?

Activated sludge purification wastewater through three stages to complete:

In the first stage, the waste water is mainly purified by the adsorption of activated sludge. Adsorption is very rapid, generally completed within 30min, BOD5 removal rate can be as high as 70%. At the same time also has the role of partial oxidation, but adsorption is the main role.

The second stage, also known as oxidation stage. Mainly to continue to decompose the pre-oxidation phase adsorption and absorption of organic matter, while continuing to absorb some of the remaining dissolved substances.

The third stage is mud-water separation stage. In this stage, the activated sludge is separated by precipitation in a secondary settling tank. Microbial metabolism and catabolism can remove organic pollutants in wastewater, but the product is different.

30, secondary sedimentation tank What are the characteristics?

Secondary sedimentation tank features: In the role of the characteristics, in addition to sludge separation, but also for sludge concentration, and due to changes in water quality, water, but also temporary storage of sludge.

31, what is the slow water filtration system?

Slow water percolation sewage is slowly passing through the land, as a result of natural infiltration and sewage purification role. Suitable for soil seeps and evaporation is small, humid areas.

32, what is fast sewage filtration system?

Suitable for very permeable soil. Such as sand, gravel sand and so on. Sewage trough quickly percolate Tian surface soon infiltration into the ground, eventually into the groundwater layer.

33, several stages of anaerobic reaction? What are

Anaerobic response is divided into three stages:

The first stage is the decomposition of organic matter into fatty acid products by hydrolysis and fermentation of bacteria.

The second stage is the hydrogen production of acetic acid further transformed 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 role of two different methanogenic bacteria, one of the hydrogen and carbon dioxide into methane, the other is acetic acid off methane.

34, what is the two-phase digestion?

Two-phase digestion is the anaerobic digestion of organic substrate acid-producing phase and methanogenic phase separately.

35, what is the material composition of sludge?

Sludge material composition can be divided into organic sludge and inorganic sludge.

According to the source of sludge, it can be divided into primary sedimentation sludge, remaining activated sludge, humus sludge, cooked sludge and chemical sludge.

36, what kind of moisture in the sludge?

Sludge contains water divided into four categories: interstitial water between particles, capillary water, sludge particles adsorbed water and particles within the water.

Removal methods: gravity, air flotation, centrifugation.

37, mechanical dehydration include?

Mechanical dehydration: vacuum filtration dehydration, filter press dehydration, rolling dehydration, sludge dewatering.

38, the purpose of the stability of sludge is what?

Sludge stabilization purposes: to eliminate the smell emitted in the sludge and kill pathogenic microorganisms in the sludge.

39, what is adsorption?

The use of porous solids (such as activated carbon) or floc substances (such as poly-iron) will be toxic and harmful substances in the waste water adsorption on the surface of solids or flocs or pores, to purify the water, this approach is called Adsorption treatment. The object of adsorption may be insoluble solid matter, it may be dissolved matter.

40, physical adsorption and chemical adsorption What are the characteristics?

Physical adsorption characteristics: adsorption heat is small, low temperature can be carried out, the adsorption is reversible, the adsorption is basically no selectivity.

Chemical adsorption characteristics: adsorption heat is large, adsorption is irreversible, selective adsorption.

41, what is the resin density?

Resin density: Generally refers to wet density and wet density as two methods of expression. The wet true density is related to the backflush strength of the resin layer, the expansion rate, and the delamination of the resin in the mixed bed and the bunk bed, and the wet visual density is used to calculate the amount of wet resin to be packed in the ion exchanger.

42, watering filler What is the role?

The role of water filler: water distribution system splashed droplets, after repeated splashing into tiny droplets or water film, increasing the contact area of ​​water and air to extend the contact time, so as to ensure the air and water good heat, quality Exchange effect.

43, what is the mixture of volatile suspended solids?

Volatile Suspended Solids (MLVSS) refers to the weight of volatile substances contained in the dry sludge per unit volume of biochemical tank mixture in mg / L. Since it does not include inorganic substances in activated sludge, More accurately represent the amount of microorganisms in the activated sludge.

44, why there is excess sludge generated?

In biochemical processes, microorganisms in activated sludge are constantly depleting the organic matter in the waste water.

Some of the organic substances consumed are oxidized to provide the energy required for the life of the microorganisms. Some of the other organic substances are utilized by the microorganisms to synthesize new cytoplasm so that the microorganisms can multiply and reproduce. At the same time that the microorganisms are metabolized, Some of the old microbes died, so excess sludge was produced.

45, what is charcoal technology?

Ferrocarbon treatment method, also known as ferric-carbon micro-electrolysis or iron-carbon electrolysis method, which is a form of application of metal iron wastewater treatment technology, using iron-carbon as a pretreatment technology to deal with toxic and harmful, high-concentration COD wastewater has a A unique effect.

46, and in the sedimentation tank effluent ph why transferred to 9 or more?

Iron effluent contains large amounts of ferrous sulfate, if not removed, it will affect the subsequent biochemical pool of microbial growth and reproduction.

Therefore, we must use lime to re-adjust the pH value of the wastewater from 5 to 6 to above 9 to convert the water-soluble ferrous sulfate into insoluble ferrous hydroxide and calcium sulfate and then coagulate them by coagulation Precipitate down to ensure that the biochemical pool of wastewater does not contain ferrous sulfate.

47, several types of flotation?

Flotation is divided into: dissolved air flotation (sub-dissolved air flotation and dissolved dissolved air flotation), air flotation, electrolysis flotation.

48, what is flocculation?

Flocculation is the polymer coagulant added to the wastewater, polymer coagulant dissolved, will form a polymer. The structure of this polymer is a linear structure with one tiny particle pulled at one end of the wire and another tiny particle pulled at the other end to act as a bridge between the two particles that are far apart so that the particles Gradually larger, the final formation of large particles of flocs (commonly known as alum flower), accelerate particle settlement.

49, Why use poly-iron wastewater flocculation adsorption treatment?

The formation of ferric hydroxide flocs during the coagulation process of polyferricum has a good ability of adsorbing organic substances in the wastewater. Experimental data show that after the wastewater is adsorbed by the polyferric flocculation, about 10-20% of the COD in the wastewater can be removed, This can greatly reduce the operational burden on the biochemical pool, is conducive to the discharge of wastewater standards.

In addition, coagulation pretreatment with polyferric acid can remove trace substances that are toxic and inhibitory to microorganisms in wastewater to ensure the normal operation of microorganisms in the biochemical pool. In many coagulants, the price of polyferricum is relatively cheap (25-300 yuan / ton), so the processing cost is relatively low, more suitable for process wastewater pretreatment.

50, why the colloidal particles in the wastewater is not easy to naturally precipitate?

Waste water, many of the proportion of suspended solids greater than 1 impurities, large particles, easily suspended sediment can be used by natural sedimentation, centrifugation and other methods to remove.

However, the proportion of less than 1, the tiny or even naked eye can not see the suspended particles is difficult to naturally sediment, such as colloidal particles is 10-4-10-6mm size of the particles, very stable in water, it settles very slowly, Subsidence 1m need to cultivate 200 years.


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