水污染控制工程下冊答案（Water pollution control engineering.）

1、水污染控制工程下冊答案（Water pollution control engineering.）1, try to explain what types of precipitation? What are the characteristics of each? Discuss types of connections and differences.Answer: free precipitation: the concentration of suspended particles is not high; in the precipitation process, suspended

2、 solids do not interfere with each other, particles separate precipitation, particle precipitation trajectory in a straight line. The physical properties of the particles remain unchanged during precipitation. Occurs in grit chamber.Flocculation precipitation: the concentration of suspended particle

3、s is not high; in the process of precipitation, the suspended particles have flocculation with each other; the particles accelerate the settlement due to the accumulation of each other, and the precipitation trajectory shows a curve. During precipitation, the mass, shape and settling velocity of par

4、ticles change. Chemical flocculation precipitation belongs to this type.Regional precipitation or precipitation layer: concentration of suspended particles is higher (more than 5000mg/L); settlement affected around other particles, maintain the relative position between the particles unchanged, form

5、ing a whole sink together, with a clear mud interface between clear water. The two clarifier occurred in the sludge thickening tank.Compression sedimentation: high concentration of suspended particles; among particles have been squeezed into a group like structure, contact with each other, to suppor

6、t each other, being squeezed out of the gravity water between particles in the upper layer of particles, the sludge concentration. Two the accumulation of sludge in the sludge tank and concentration tank is compressed and precipitated.Contact and difference: free precipitation, flocculation precipit

7、ation, regional precipitation or stratified precipitation, the concentration of suspended particles in compression and precipitation increases in turn, and the interaction between particles is strengthened in turn.2, what is the purpose and function of the grit chamber? What is the difference betwee

8、n an aerated sand settling tank and a flow sand sinking tank?Answer: the purpose and function of setting sand pool by gravity or centrifugal force separation as the foundation, is about to enter the control that the inorganic particles are large relative density in the only sink sand pool of sewage

9、flow, and the suspended particles with water away, which can get rid of the inorganic particles of sand, coal slag from high density sewage in normal operation, in order to avoid the influence of impurities for subsequent processing structures.Flat flow sand pool is one of the most traditional sand

10、pool, it has the advantages of simple structure, stable work, will enter the sand pool of sewage flow control so that the relative density of the inorganic particles in the suspended particles and can only sink with water away, so as to remove inorganic particles of sand, coal slag density from wast

11、ewater. The working principle of aerated grit chamber by aeration and water spiral effect of sewage in the suspended particle collision and friction, and by the erosion of rising bubbles, the adhesion of organic pollutants in the sand can be removed. Containing organic aerated grit in less than 5%;

12、the aeration device is provided with a pool, it also has pre aeration, deodorization, prevent sewage anaerobic decomposition, in the role of global and accelerate the separation of oil in sewage.3. What is the basic principle of the treatment of water by precipitation? The basic law of static free s

13、edimentation (or floating) of spherical particles is analyzed. What are the factors that affect settlement or buoyancy?Answer: the basic principle: precipitation method is the use of suspended particles of water in the settlement performance, in gravityA process that produces a sinking action to ach

14、ieve solid-liquid separation.Basic Law: when the suspended particles begin to settle (or float) in the static water, they will be affected by gravity, buoyancy and friction. At the beginning of settling (or floating), the acceleration is caused by the gravitational force. After a short period of tim

15、e, when the gravity of the particles balances with the resistance produced by the water, the particles will sink at constant velocity.The influencing factors are particle density, flow velocity, and surface area of the pool.5, the known design of sewage treatment plant in the average flow of Q=20000

16、M3/D, serving a population of 100000 people, according to 25G, the amount of primary sludge (day), the sludge moisture content of 97%, please design aeration grit settling tank of peace.Solution: Qmax=20000/ (24*3600) =0.23M3/S=833.3M3/HAeration type grit chamber: total effective volume: V=60*Qmax*t

17、=60*0.23*2=27.6m3Pool section area: A=Qmax/Vmin=0.23/0.08=2.88m2Pool total width: B=A/Hmin= pool length L=V/A=27.6/2.88=9.58mRequired aeration: q=60D*Qmax=60*0.23*0.2=2.76m3/minAdvection sedimentation tank:Precipitation area surface: A=Q (max) /q=833.3/2.5=333.3m2Effective depth of precipitation zon

18、e: h2=q*t=2.5*1=2.5mEffective volume of precipitation zone: V=A*h2=333.3/3=111.1m3Length of sedimentation tank: L=3.6*v*t=3.6*0.0005*3600=6.48mTotal width of precipitation zone: B=A/L=333.3/6.48=51.44mNumber of settling tanks: n=B/b=51.44/401, take 2Sludge volume: V= (S*N*T) /1000= (20000*1000*4*3%)

19、 /24*1000=100m2Total height of sedimentation tank: H=h1+h2+h3+h4=0.3+2.5+0.3+2.1=5.2m(S1=25m2, S2=1m2, H4, =0.35m, H4, L2=0.3m, =1.75m, L1=1.5m, etc.)Storage tank volume: V=1/3*h4 (S1+S2+) =3.61m3The volume of sludge in the trapezoidal part above the storage tank is V= (L1/2+L2/2) *h4 *b=63m36, what

20、 is the basic principle of pressurized dissolved air flotation? What are the basic processes and ways of dissolving gas? What are their respective characteristics?Answer: the basic principle of pressurized dissolved air flotation: the air is dissolved under pressure, and the supersaturated air is re

21、leased in the form of tiny bubbles under normal pressure.Basic process and characteristics: full pressure dissolved air flow, characterized by the entire inflow wastewater pressure dissolved gas, and then released into the air flotation tank through decompression release device for solid-liquid sepa

22、ration. Part of the pressurized gas dissolved process: the partial inflow wastewater pressurized dissolved gas, and then released into the air flotation tank through the pressure release device, the other parts directly into the air flotation tank for solid-liquid separation. Partial recirculation p

23、ressurized dissolved air flow: part of liquid reflux pressure into the water directly into the flotation tank, solid-liquid separation.9 、 What are the advantages and disadvantages of flotation and sedimentation in wastewater treatment?Answer: the air flotation method: to separate those particle den

24、sity close to or less than the water particles, suitable for activated sludge floc precipitation is not easy or prone to expansion, but the micro bubble requires energy, high economic cost.Precipitation method: it can separate the particles whose density is larger than that of water energy, and the

25、separation of solid and liquid does not require energy, but the area of sedimentation tank is larger.Eleventh chapters1. The principle and application condition of aerobic and anaerobic biological treatment of organic wastewater are briefly described.Answer: aerobic biological treatment: in the pres

26、ence of free oxygen (molecular oxygen), aerobic microorganisms degrade organic matter, so that it is stable and harmless treatment methods. Microorganisms use organic pollutants (dissolved and colloidal) as the source of nutrients for aerobic metabolism. These high energy level organic matter throug

27、h a series of biochemical reactions, gradually release energy, and ultimately to stabilize the lower level of inorganic substances, the harmless requirements, in order to return to the natural environment or further disposal. Suitable for medium and low concentration organic wastewater, or organic w

28、astewater with BOD5 concentration of less than 500mg/L.Anaerobic biological treatment: biological treatment of facultative bacteria and anaerobic bacteria to degrade and stabilize organic matter without the presence of free oxygen. In anaerobic biological treatment, complex organic compounds are deg

29、raded into simple compounds that release energy at the same time. Suitable for organic sludge and high concentration organic wastewater (BOD5 = 2000mg/L).2, a sewage treatment reactor in a continuous flow and complete mixing in the reaction is not reversible, with the first-order reaction, V=KSA, K=

30、0.15D-1, and when the reaction tank volume is 20M3, the reaction efficiency is 98%, the sewage flow reaction pool can handle as much?Solution: Q is the sewage flow, S is the substrate concentration: Q*S=20*v=k*S*20Then: Q=20k=0.15*20=3m3/d Q (real) =Q/98%=3.06m3/d3 the basic steps of biological nitr

31、ogen removal in municipal wastewater are briefly described.Answer: the microbial decomposition of organic nitrogen ammonification reaction to generate NH3, then in the nitrite bacteria and nitrifying bacteria under the action of the nitrification reaction (sub) nitrate, the denitrification reaction

32、(sub) reduction of nitrate to nitrogen. When the influent ammonia nitrogen concentration is low, assimilation may become the main way of nitrogen removal.4. Briefly describe the principle of biological phosphorus removal.Answer: in the anaerobic aerobic alternating operation system, it has the chara

33、cteristics of anaerobic phosphorus by Microbial Phosphorus Release and aerobic excess phosphorus uptake, so that a large number of mixed liquid to reduce the concentration of phosphorus in the aerobic stage, finally through the discharge containing a large amount of phosphorus rich sludge and phosph

34、orus removal from wastewater to achieve.Http:/1. briefly describe the principles and conditions of aerobic and anaerobic treatment of organic wastewater.Answer: sewage biological treatment is the treatment of sewage by means of the metabolism of microorganisms, which are widely distributed in nature

35、, such as individual micro, metabolic, trophic types, and adaptable.Aerobic biological treatment involves the presence of dissolved oxygen in water (i.e., the presence of molecular oxygen in water). The aerobic biodegradation of organic matter, making it stable and harmless treatment; anaerobic biol

36、ogical treatment is neither in the water and there is no molecular oxygen combined oxygen conditions, biological treatment method of facultative bacteria and anaerobic bacteria degradation and stabilization of organic matter.2. some sewage is treated in a continuous influent and fully homogeneous re

37、actor,Assuming that the reaction is irreversible, and in accordance with the first order reaction (v=kSA), the reaction rate constant k is 0.5d-1, for when the reaction tank volume is 20 m3, the reaction efficiency was 98%, sewage flow in the reactor can be treated as much?3. the basic steps of biol

38、ogical nitrogen removal in municipal wastewater are briefly described.Answer: the process of biological nitrogen removal mainly involves ammonification, nitrification and denitrification.(1) ammoniation: the process of microbial decomposition of organic nitrogen compounds to produce ammonia is calle

39、d ammonification. Under the action of ammonification microorganisms, organic nitrogen compounds are decomposed and converted into ammonia nitrogen under aerobic or anaerobic conditions.(2) nitrification reaction: converting ammonium nitrogen into nitrite (NO2- -) and nitrate (NO3-) under the action

40、of nitrifying bacteria and nitrifying bacteria.(3) denitrification reaction: under anoxic conditions, NO2- and NO3- were reduced to nitrogen under the action of denitrifying bacteria.4. briefly describe the principle of biological phosphorus removal.Four. Activated sludge process1. what are the basi

41、c concepts and basic processes of activated sludge process?Answer: activated sludge process is the use of suspended growth of microbial floc treatment of organic waste water, a class of aerobic biological treatment.The process of activated sludge treatment includes aeration tank, sedimentation tank,

42、 sludge return system and excess sludge removal system. The graph is like book 251The wastewater after pretreatment, activated sludge mixed into mixed liquid into the aeration tank and the tank, and fully in the aeration tank, on the one hand, the activated sludge in suspension, full contact wastewa

43、ter and activated sludge; on the other hand, through the aeration, oxygen supply to the activated sludge, aerobic conditions, to ensure the normal growth of microorganisms the. The organic substance in the waste water is decomposed and absorbed by activated sludge in the aeration tank, and the mixed

44、 liquid enters the two sedimentation tank to carry out solid-liquid separation, and the purified waste water is discharged. Most of the settling sludge in the two clarifier flows back into the aeration tank and mixes with the wastewater entering the aeration tank.2. what are the basic forms of activ

45、ated sludge aeration tank?Answer: the aeration tank is essentially a reactor. Its pool type is closely related to the required hydraulic characteristics and reaction requirements. The aeration tank is mainly divided into four categories: push flow type, full mixing type, closed circulation type and

46、continuous batch type.3. what are the main operation modes of activated sludge process? What are the characteristics of each operation mode?Answer: the main operating modes are: ordinary activated sludge aeration, aeration, decreasing stage aeration method, adsorption regeneration (contact) method,

47、adsorption and biodegradation process, delay aeration and oxygen aeration and intermittent activated sludge.Characteristic：Ordinary aeration method: in the aeration tank, the concentration of organic matter and the oxygen demand of wastewater will gradually decrease along the length of the pool, whi

48、le the oxygen supply will be distributed uniformly along the length of the pool, which may lead to the shortage of oxygen supply in the anterior section and the excess oxygen supply in the posterior section. The advantages of this method is that the activated sludge aeration for long time and high t

49、reatment efficiency, average removal rate of BOD was 90% - 95%, especially suitable for the treatment of water requirement is high and relatively stable wastewater; but it exists serious defects. (other exercises after class)4. explain the concept of sludge age and explain its function in the design

50、 and operation management of sludge treatment system.Answer: sludge age is the average residence time of microorganisms in the treatment system.The age of sludge is an important parameter in the design and operation of activated sludge treatment system. It is also important in theory. The importance

51、 of sludge age as a biological treatment parameter is obvious, because the specific growth rate of microorganisms and the physiological state of microorganisms in the system can be controlled by controlling the age of sludge sludge.5. the main influence factors of oxygen transfer are analyzed from t

52、he double film theory of gas transfer.Answer: the main factors affecting the oxygen transfer rate are the oxygen partial pressure in the gas phase, the concentration gradient of oxygen in the liquid phase, the contact area between the gas-liquid and the contact time, the temperature of the water, th

53、e nature of the sewage and the degree of turbulence of the flow.(1) waste water quality: sewage contains various impurities, which will have some influence on the transfer of oxygen. Among them, dissolved organic matter, especially some surface active substances, will concentrate at the gas-liquid i

54、nterface, forming a layer of molecular membrane, increasing the resistance of oxygen transfer, and affecting the diffusion of oxygen molecules.(2) water temperature: water temperature has a great influence on oxygen transfer, water temperature rises, water hungry viscosity decreases, liquid film thi

55、ckness decreases, diffusion coefficient increases, KLa value increases; conversely, KLa value decreases. Water temperature also has an effect on dissolved oxygen saturation and Cs. With the increase of temperature, the KLa value increases, the Cs value decreases, and the concentration gradient of ox

56、ygen in the liquid phase decreases. Therefore, the water temperature has two opposite effects on the oxygen transfer, but it is not completely offset. In general, the reduction of water temperature is beneficial to the transfer of oxygen.(3) oxygen partial pressure: Cs value, besides being affected

57、by dissolved salt and temperature in sewage, is also affected by oxygen partial pressure or air pressure. The air pressure is lower, and the Cs value is decreased.6. what are the environmental conditions, requirements and major influencing factors of biological nitrogen removal and phosphorus remova

58、l? The characteristics of main biological nitrogen removal and phosphorus removal processes are described.Answer: biological nitrogen and phosphorus removal factors are: (1) environmental factors such as temperature, pH, DO; (2) the process factors such as precipitation, the effect of hydraulic reaction zone of sludge age, residence time, two sedimentation tank; (3) the composition of waste water, such as sewage easily degradable organic matter concentration BOD5, N, a