水的生物处理Water Biological Treatment-孙WWT1-EXAM-2011-12-23-A4

- 1 - 哈尔滨工业大学深圳研究生院 2012 年 秋 季学期期末考试试卷 HIT Shenzhen Graduate School Examination Paper Course Name: Water biological treatment I Lecturer: SUN Fei-yun Question OneTwo Three Four FiveSixSeven Eight NineTenTotal Mark Answer any FOUR questions. All questions carry equal marks (25 marks). Candidates are permitted to bring FOUR A4 size fact sheets into the examination hall. Use of Electronic Calculators: Candidates taking examination that permits the use of calculators may use any calculator which fulfills the following criteria: (a) it should be self-contained, silent, battery-operated and pocket-sized; and (b) it should have numeral-display facilities only and should be used only for the purpose of calculation. It is the candidate's responsibility to ensure that the calculator operates satisfactorily. 1. a) In the Buji District of Luohu, sewage discharge into Shenzhen Harbor frequently occurs in recent years. You are asked to propose a programme for a sewerage collection and treatment process study in the troubled district. Please outline briefly the programme with contents such as the, major tasks, approach and tools to be used, treatment system prefer to be selected (15 marks). Student Name: Student ID: Major: 答题内容写在边线外视为无效 - 2 - 2. (a) A bio-tower, which is a modified trickling filter, will be used to treat a municipal wastewater at a flow-rate of 10,000 m3 /d for BOD5 reduction from 150 mg/L to 20 mg/L. The bio-tower is filled with plastic media 8 m in depth. Assume that the kinetic coefficients are k=4.0 (md)-0.5 and n=0.5 for the design equation below, determine the inner diameter of the bio-tower if no recirculation is used. (10 marks) R q kH R S S n A )exp()1 ( 0 (b) Compare and discuss the different characteristics of microorganisms in the suspended growth process (activated sludge process) and attached growth process (biofilm process), and brief the function of biomass extracellular polymeric substances (EPS) in these two processes. (15 marks) - 3 - 3. A new private housing development for 1,000 people without access to public sewerage is required to provide its own treatment facility to treat the sewage to acceptable standards for near-shore discharge. An activated sludge treatment plant of the extended aeration modification, not preceded by primary sedimentation, is selected. The following design parameters are recommended by EPD in “Guidelines for the design of small treatment plants“: Influent: 380 L/person-d 57 g BOD/person-d 57 g SS/person-d peak flow = 3 ADWF (average dry weather flow) Extended aeration: F/M 0.07 kg BOD/kg MLSS-d MLSS = 2500-3500 mg/L average HRT = 24 hrs BOD concentration in effluent =20 mg/I sludge yield = 1 kg SS/kg BOD removed solid content in sludge from sedimentation tank = 1% (10 g SS/L) SS concentration in effluent = 20 mg/I (a) Find the average BOD and SS concentrations (mg/L) in the wastewater influent. (5 marks) (b) Determine the volume of the aeration tank (m3). (7 marks) (d) Select the actual F/M and MLSS values that agree with each other. (5 marks) (e) Estimate the sludge age (d) and the rate of wet sludge to be discharged (m3/d). (8 marks) - 4 - 4. A domestic wastewater is biologically treated in an aerobic lagoon, which is an activated sludge modification: complete-mix extended aeration WITHOUT recycle. The system is at steady-state and Monod growth function is applicable. If the wastewater flow-rate remains the same but the influent BOD concentration doubles, predicate and explain its impact on the new steady-state values (such as increased, decreased, or kept the same) of: the decay coefficient (kd), biomass concentration (X), the specific substrate utilization rate (U), the mean cell residence time (c), the effluent BOD concentration (Se) and BOD removal efficiency (). (some schematic and mathematic description would be helpful) - 5 - 5. Describe the classification of membrane filtration based on their materials, pore size and driving force, and brief the main benefits and disadvantages of using membrane bioreactor (MBR) other than the conventional activated sludge process in biological wastewater treatment. Demonstrate the detail about membrane fouling, and accordingly, give some potential methods for membrane fouling mitigation or minimization. (25 marks) 6. a) In a biological wastewater treatment system, a loading increase in the F/M ratio would usually result in an increase in the BOD removal rate (kgBOD/d), but a decrease in the BOD removal percentage (%). Explain the main reasons. (8 points) b) Sludge retention time (SRT) is an important operational parameter for the activated sludge process. Explain its (SRTs) importance in regulating the performance of the activated sludge process, such as the effluent quality, waste sludge production and related cost implications. (some mathematical descriptions are required). (8 points) c) Compare the advantages and disadvantages of the two typical activated slu