题目内容

Suppose a RH-RNa ion-exchange softening system is applied to treat raw water with salt contents shown below.Ca2+：120 mg/L Mg2+：42 mg/L Na+：69 mg/L K+：19.5 mg/LHCO3-：427 mg/L SO42-：120 mg/L Cl-：124.25 mg/LIf the effluent basicity demand is 0.5 mmol/L, the proportion of water flowing into RH exchanger should be ______ _% of the total water flow.Please fill in an integer.

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Suppose raw water is treated in a siphon filter. The water flow rate is Q=25000 m3/d. If the filtration velocity should be 10 m/h, the number of filter cells should be more than _ ;(Washing intensity is 15 L/(m2·s))and the corresponding area of each cell should be _ m2. Please fill in integers into the blanks.

Suppose a sedimentation experiment is conducted using a certain wastewater with suspended matter (SS) concentration of C0. The height of the settling column is 3 m. Take samples from the middle and bottom to determine SS as C, as shown below. Settling time (min) 30 45 60 90 120C/C0 In the middle (%) 30 20 15 10 7.5C/C0 In the bottom (%) 60 40 30 20 15 (1) The sedimentation type in the settling column is _ settling.(2) Assume water flow rate is 2000 m3/h. SS removal rate should be more than 85%. By the data above, the surface load of the settling tank should be _ m3/(m2h). The answer is an integral number. (Magnification coefficient is 1.5)(3) The settling area is approximately ________ _*1000 m2. (Please fill in an integer)

Water temperature is a factor of coagulation and flocculation. The coagulation efficiency decreases at low water temperature, because:(1) hydrolysis of inorganic salt coagulants is an _ (choose endothermic/exothermic) process;(2) strength of Brownian motion of impurities (choose increases/decreases);(3) hydration of colloids ___ (choose increases/decreases).

慢性支气管炎急性发作的最常见原因是( )

A. 吸烟
B. 大气污染
C. 感染
D. 体温下降
E. 过敏