Corrections to the Comprehensive Guide to Answers from Experts on the National Examination for Licensed Environmental Engineers
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Correction to the \"Compendium of Answers from Experts for the National Qualification Examination for Registered Environmental Engineers\" This article is from: Water World Network; Author: mingqian. In the book \"Compendium of Answers from Experts for the National Qualification Examination for Registered Environmental Engineers – Focus on Water Pollution Control\" published in 2008, I would like to make corrections and ask a few questions: 1. The correct answer to question 3 in the multiple-choice question on page 91 should be C, not B. Because DO increases and CO2 decreases during the day, the pH value should rise. 【Answer】: According to the explanation in question 12 on page 88 of this book, the correct answer to question 3 should be C. There is a mistake here in the book. 2. On line 4 of P127, “ dirty should be replaced with “ Rain”” ； On the second-to-last line of P128, “dry flow wastewater volume” should be replaced with “rainfall volume”” ； On line 5 of P129, the character “ Rain” should be replaced with “ Dirt”. 【Reply】: (1) On page 127, line 4, question 36: if calculated based on full flow, the term “sewage” in the question should be changed to “rainwater”. There is a mistake here in the book. (2) On the second-to-last line of page 128, it is a typo; “volume of wastewater from dry flows” should be changed to “rainfall volume”. (3) The word “rainwater” on line 5 of page 129 should be removed, i.e., it should be the design flow rate Q3‑4. 3. In which book is the formula for hf mentioned on the 9th line from the bottom of P142 described in detail? 【Answer】: The Hasson-Williams turbulence formula on page 336 of \"Drainage Engineering (Part 2)\". 4. In line 19 of P144, “wherein S is the gap between the grating bars of the selected grid scrubber” should be replaced with “wherein S is the width of the grating bars of the selected grid scrubber”. 【Reply】: S is the width of the grating bars of the selected grid cleaner; there is an error in this part of the book. 5. On the second-to-last line of P147: The unit for S should be L/(person•day), rather than g/(person•day). 【Response】: The unit of S should be L/(person•day); there is an error in the book here. 6. Pages P152-153 present the formulas for calculating oxygen demand in the \"Specifications\" and the \"Manual\". Which formula should be preferred in actual exams? 【Reply】: Indeed, there are different calculation methods for oxygen demand specified in the \"Standards\" and the \"Manuals\". We have reviewed relevant materials, but opinions vary. Therefore, this book presents two authoritative approaches here, in the hope of drawing attention to this issue and fostering further discussion. I initially plan to conduct in-depth research on this issue as soon as possible, and will reach out to you once there is progress. It is recommended that during the exam, decisions should be made based on the parameters of the given conditions. 7. On line 14 from the bottom of P153, the unit for R should be kg/d, rather than mg/L. 【Reply】: The unit for R should be kgO2/d; there is an error in the book here. 8. On pages P154-155, when determining the amount of excess sludge, Formula Method (1) from the \"Specifications\" and Formula Method (2) from the \"Manual\" are introduced. Which formula should be given priority when taking the exam? Is it determined by the parameters of the known conditions? 【Answer】: Same as question 6 above. 9. On the 8th line from the bottom of P155, the numerator of the fraction “21600×(200-20)” should be changed to “21600×0.6×10×(200-20)”, and the denominator of the fraction “0.20×3000” should be changed to “0.7×3000×(1+0.07×10)”. 【Reply】: The formulas for algorithms a and b in the book are different, but the calculation processes are the same; it is a typo. The 8th line from the bottom should be: , there is an error in the book here. 10. In the third last row of P155, “W” should be replaced with “Wv”, and the second last row should be swapped with the third last row. Because Wv is the amount of dry sludge. 【Reply】: On line 5 from the bottom of page 155, in item (3) for calculating the amount of excess sludge to be removed per day, the calculation order should be WV → W → Qs. Therefore, the “W” in the third-to-last row should be “Wv”, and the second-to-last row should be swapped with the third-to-last row. There is a mistake here in the book. 11. On line 6 of P157, 2500×200/(160×3846+400×7000) = 0.24; there is an issue with the denominator values. Using the original values, the result cannot be 0.24. 【Response】: It should be , the answer is correct; an error occurred during entry in the public display. 12. In the 8th line from the bottom of P162, “t2” should be changed to “t1”, and ln(100/60) that follows it should be changed to ln(200/100). 【Reply】: There was an error in entering this question; it should be: . 13. Question 46 on P173: How is the oxygen requirement of 10 kg, which is 7–12 kg, calculated? 【Answer】: The question is not precise and should be removed; the reason is the same as for Question 6. 14. On the second-to-last line of P173, “1.0—3.0m” should be changed to “3.5—4.5m” (since the correct answer is D, the statement in option A must be correct; otherwise, both A and D would be incorrect answers for this question). 【Reply】: On the second last line of page 173, “1.0～3.0m” should be changed to “3.5～4.5m”; there is an error in this part of the book. 15. For question 8 on P177, the answer key in the book lists ABC as the correct answers, but I believe the correct answers are AB. 【Answer】: This question is from page 148 of the \"Specifications\"; the answers are ABC, but the question is incorrect – it should refer to the denitrification reaction. 16. Are options B and D in question 5 of P254 exactly the same? 【Answer】: The “mixing solution reflux” step should be removed from option D; therefore, the correct answer is B. 17. On line 7 of P270, the unit in the numerator is “kg”, while the unit in the denominator is “g”; the units are not consistent. 【Response】: When calculating, the units on the numerator and denominator are inconsistent; conversion is required. 18. For question 7 in P272, the conditions given are insufficient; the number of hours per daily production shift, T, must be provided in order to use the formula Q = (m•M•kd•kh) / 3600T for calculation. If option B is chosen according to the answer key for this question, it can be inferred that T=42 hours, which clearly does not correspond to reality – no matter how many shifts there are in a day, it is impossible to work 42 hours. 【Answer】: A condition of \"hours per daily production shift T\" was added to the question, and the options were changed to: A. 23.1 B. 26.3 C. 46.3 D. 138.9 The correct answer is C. 19. Question 20 on P274: How is the equivalent concentration of the wastewater after mixing calculated? Is this equivalent concentration the concentration of the remaining NaOH in the reaction, or the concentration of the generated NaCl? 【Answer】: This question deals with the neutralization of strong acids and strong bases; it should clearly state that the goal is to determine the equivalent concentration of the acid and base. After accounting for errors in the values of equivalents, answer C should be chosen. 20. How is the answer B=4.57 calculated for question 28 in P274? And my calculated total is 5.47. 【Reply】: There is an error in this part of the book; the correct answer, option B, should be 5.47. 21. Question 1 of the comprehensive question on P276: Calculate the sludge concentration in the aeration tank mixture. I have two different views on this question. First, there are too many assumptions (such as SVI, r, and R all need to be set), and moreover, the range of possible values for SVI is wide, so the answers could vary greatly. Second, since this is a conventional activated sludge process, the r (internal recirculation ratio) is not required; is it feasible to use only X = R•Xr/(1+R)? 【Response】: The problem is missing the conditions “SVI set to 120, r set to 1.2, R set to 50%”. Furthermore, in the formula, r is a correlation coefficient that takes into account factors such as the residence time of the sludge in the secondary sedimentation tank, the depth of the tank, and the thickness of the sludge; its value is generally around 1.2, and it does not represent the internal circulation ratio. 22. On line 18 from the bottom of P276, it states that \"the relationship with the total height of the filter media layer is shown in Figure 9-24\", but Figure 9-24 cannot be found anywhere in this book; however, Figure 7-13 can be found on page P408 of the \"Water Supply and Drainage Design Manual\" (Volume 5). 【Answer】: It should be Figure 9-19, sourced from page 219 of \"Drainage Engineering (Part 2)\" and page 408 of the \"Water Supply and Drainage Design Manual\" (Volume 5). There is a mistake here in the book. 23. The water level elevation shown in the diagram of the P277 grit chamber should be changed to 9.00m, rather than 4.00m. 【Reply】: There is an error here in the book. 24. On the second-to-last line of P277, to find the total head of the pump, option D is chosen according to the answer key in the book; therefore, the safety head is taken as 0.5 – 1.0 m. However, the standard specifies a safety head of 0.3 – 0.5 m. Why isn’t the question formulated in accordance with the standards? 【Answer】: This question is a sample question published by the Environmental Protection Specialty Management Committee of the National Registered Engineers in Survey and Design. The specification regarding the safety head (0.5 – 1.0 m) conflicts with the requirements set out in the Standards (0.3 – 0.5 m); among the alternative answers, this one is the closest to the correct value. (Note: 0.5m is used in the calculations of the Design Manual. ) 25. Is there no option for question 4 on P278? 【Response】: The mercury concentration must not exceed 0.00005 mg/L; there is an error in this part of the book. 26. Question 5 on P278: Both A and B are Category 1 pollutants; can only A be selected? 【Answer】: The answer should be A. The “Comprehensive Wastewater Discharge Standards” refer to total arsenic; therefore, option B is inaccurate. 27. In question 15 of P279, the value 200000 in option D should be changed to 20000. 【Answer】: Option D should be changed to 20,000; there is an error in the book at this point. 28. The answer to question 17 on P279 should be D, not B. 【Answer】: The answer should be D; there is an error in the book here. 29. The answer to question 28 in P280 should be C, not B. 【Answer】: The answer should be C; there is an error in the book here. 30. The answers to question 29 in P280 should be 4.19 and 6.06; none of the given options are correct. 【Answer】: See Question 5 on page 268 of this book. Solve for the hydraulic load rate q: Solve for the wetland area A: The correct value for A is incorrect. 31. The answer to question 11 in P281 should be ACD. 【Answer】: The correct answers should be ACD. There is a mistake here in the book. 32. For Question 1 of the P281 comprehensive question, the necessary information is missing; MLS and the time-varying coefficient Kh should be provided. Otherwise, where do X and Kh in the solution explanation come from? 【Answer】: The given information for this question is insufficient; it will be added in the revised version. The solution process can be found in the explanation on page 285. Two exam questions from 2007: 1. Regarding water balance, the water inflow is 20,000 m3/d and is used for reclamation; 1% of this water is used for coagulation and chemical dosing, 2% is used for backwashing the filters, and 5% is lost during the processing. How much reclaimed water can be obtained? A、18385 B、18535 C、1900 D、2000 【Answer】: Two of our colleagues have different opinions on this question; we will get back to you once a decision is made. 2. There is a question related to filtration processes. Given that the designed water flow rate is 12,000 m3/d, the proportion of water used for internal purposes is 5%, the filtration cycle lasts 12 hours, each cleaning session takes 6 minutes, and the filtration velocity is 5 meters per hour, determine the area of the filter tank. 【Solution】: (1) The designed water flow rate Q = 12000 × 1.05 = 12600 m3/d. (2) The actual daily operating time T of the filter tank: where – is the daily operating time. Based on the question, the filtering cycle is 12 hours, with 24 hours per day. – Number of times per day for rinsing. =2. – Time to stop using and discharge the primary filtered water after daily rinsing. For this question, 0 is taken. －Time per rinse. =6min. = h, then the filter area: m2
Corrections and Additional Questions to the \"Compendium of Answers from Experts on the National Qualification Examination for Registered Environmental Engineers\" In the book published in 2008, titled \"Compendium of Answers from Experts on the National Qualification Examination for Registered Environmental Engineers – Water Pollution Control Specialization\", I would like to make further corrections and ask the following questions: First, on page 56, line 11, there is… Why is X used in the formula on the 10th line from the bottom of page 60, instead of XV? In this formula, should “X” or “XV” be used during the exam? Answer to Question 1: Both X (MLSS) and Xv (MLVSS) are indicators used to approximate the amount of microorganisms in a activated sludge system; Xv is more accurate than X. The relationship between the two is: . Since both are used to indicate the sludge concentration, they can be used interchangeably in many cases. However, it is essential to maintain consistency; that is, if Xv (or X) is used in a certain expression, it must be used consistently throughout. In particular, if Xv (or X) is used in the numerator, then any quantity representing sludge concentration in that numerator must also be expressed as Xv (or X) in order to preserve consistency. For example, it can be = (note: the value in the denominator here must be the increment of Xv), or it can also be = (note: the value in the denominator here must be the increment of X, more precisely, it should be ). With this understanding, it becomes easy to answer the question of why X is used instead of Xv in the formula on the 10th last line of p60: since the given value in the problem is MLSS=4000 mg/L, which means X=4000 mg/L, it is sufficient to use X to calculate the sludge age. When taking the exam, decide whether to use X or Xv based on the question requirements, as long as consistency is maintained. II. On page P60, the 4th line from the bottom, under “Calculate the sludge load rate”, this example is for calculating Nrs, which represents the BOD degradation load. Would it be correct if a candidate calculated Ns, which is the BOD load of the influent water? Answer to Question 2: The new version of the \"Code for Design of Outdoor Sewerage Systems GB 50014‑2006\" states that: \"In the formula for calculating the sludge load, it was previously based on the five-day biochemical oxygen demand of the incoming water; now it is calculated based on the five-day biochemical oxygen demand that has been removed.\" ”Therefore, calculating the sludge load rate based on the removed five-day biochemical oxygen demand is a method that meets the regulatory requirements. Of course, some reference materials, including textbooks such as \"Drainage Engineering, Volume 2,\" define the sludge load based on the five-day biochemical oxygen demand of the influent, which is due to the use of older standards. III. On page P61, line 6, to find the dry weight of excess sludge, △X, use the formula △X = aQ•Sr – b•V•XV. Why is △X/f used? Answer to Question 3: This question is similar to the first one; it also involves the relationship between Xv and X. Since Xv is used in the calculations (note: =a•Q•Sr-b•V•Xv), in order to calculate the dry weight of the sludge, MLVSS needs to be converted into MLSS, and therefore /f is used. IV. Where does the “10000” in line 7 on page P61 come from? If it is a typo (i.e., 1000), then according to the calculations in the original book, the result should be negative Answer to Question 4: On line 7 of page 61, the value “10000” should represent the daily amount of wastewater to be treated as specified in the question. There is a missing digit “0” in that value; it should be “10000 m3/d”. We apologize deeply for this mistake! V. On page P61, line 16, QwXr essentially represents the dry weight of sludge, △X; why not simply use the value of △X instead? Answer to Question 5: The statement that “QWXr is essentially the dry weight of sludge” is inaccurate; it should be “QWXr actually represents the dry weight of sludge”. Since QWXr is essentially the dry weight of the sludge, it is of course possible to calculate the sludge age using the = symbol. The example provided is just another method for calculating the sludge age; it’s acceptable to use either method for the calculation, although the results will differ. Furthermore, the reason for the difference in sludge age values obtained by the two methods is that the return sludge concentration Xr is estimated using an empirical formula, which is not precise enough. In fact, for general problems, the given conditions allow for only one method to calculate the sludge age; whereas in the example problems, the given conditions enable two methods to be used for calculation. VI. On page P61, the third line from the bottom, I believe that (Sa-Se) can only be replaced by Sa, because the known Ns represents the BOD load of the incoming water, rather than the BOD load resulting from degradation, right? Answer to Question 6: This question is similar to the second one. The sludge load used for calculating the volume of aeration tanks in the \"Code for Design of Outdoor Drainage Systems GB 50014–2006\" is based on the biochemical oxygen demand to be removed over a period of five days. The \"Code for Design of Outdoor Drainage GB 50014－2006\" must be followed when designing water treatment projects. VII. The 8th line from the bottom on page P61 is meant to calculate the amount of dry mud (kg/d), that is, △X; then why is the amount of wet mud calculated in the solution? Answer to Question 7: If the question asks for the amount of dry sludge, it should be the value of , not . As for the value of \"amount of excess sludge to be removed per day (kg/d)\) that is requested in the question, it should actually be \"amount of excess sludge to be removed per day (m3/d)\\"; this was our mistake. Please forgive us, and thank you for bringing this issue to our attention! VIII. On page P62, line 16, in the expression “0.15×48000×2250”, 48000 represents flow rate rather than volume; should it be changed to 5669? Answer to Question 8: As you mentioned, the value 48000 in \"0.15×48000×2250\" should be replaced with 5669. Thank you for raising this question. IX. On page P62, the last page, R•Cs(20) in the numerator should be R•Csb(20). Cs(20) and Csb(20) are two completely different concepts; the former refers to the oxygen saturation concentration in fresh water at 20°C, while the latter refers to the average oxygen concentration in wastewater in an aeration tank at 20°C. Their values are also entirely different, right? Answer to Question 9: On line 6 from the bottom of page p62, there is no error in the value R•Cs(20) in the numerator. Cs(20) and Csb(20) are indeed two different concepts; Cs(20) represents the saturation level of oxygen in pure water at 20°C under atmospheric pressure, while Csb(20) refers to the average saturation level of dissolved oxygen in the mixture in an aeration tank at 20°C.