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CWEA GRADE 1 LAB ANALYST PRACTICE TEST 3 QUESTIONS WITH CORRECT ANSWERS, Exams of Water Resources Planning and Management

California Institute of Technology (Caltech)Water Resources Planning and Management

CWEA GRADE 1 LAB ANALYST PRACTICE TEST 3 QUESTIONS WITH CORRECT ANSWERS

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2024/2025

Available from 07/13/2025

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CWEA GRADE 1 LAB ANALYST PRACTICE TEST 3
QUESTIONS WITH CORRECT ANSWERS
1) The hardness determination by EDTA titration measures: -- Answer โœ”โœ” Calcium
and magnesium
2) The indicator for the hardness determination is: -- Answer โœ”โœ” Eriochrome Black T
3) EPA-acceptable primary standards for turbidity determination: -- Answer โœ”โœ”
Formazin
4) BOD determination is an empirical test in which standardized lab procedures are
used to: -- Answer โœ”โœ” determine the relative oxygen requirements of waste waters,
effluents, and polluted waters
5) What's the protocol for sample pretreatment for BOD? -- Answer โœ”โœ” Assuring that
the samples are neutralized to a pH range between 6.5 and 7.5 and any residual
chlorine has been dechlorinated
6) What is disinfection? -- Answer โœ”โœ” Process designed to kill most microorganisms in
wastewater, including all essentially pathogenic bacteria
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CWEA GRADE 1 LAB ANALYST PRACTICE TEST 3

QUESTIONS WITH CORRECT ANSWERS

  1. The hardness determination by EDTA titration measures: -- Answer โœ”โœ” Calcium and magnesium
  2. The indicator for the hardness determination is: -- Answer โœ”โœ” Eriochrome Black T
  3. EPA-acceptable primary standards for turbidity determination: -- Answer โœ”โœ” Formazin
  4. BOD determination is an empirical test in which standardized lab procedures are used to: -- Answer โœ”โœ” determine the relative oxygen requirements of waste waters, effluents, and polluted waters
  5. What's the protocol for sample pretreatment for BOD? -- Answer โœ”โœ” Assuring that the samples are neutralized to a pH range between 6.5 and 7.5 and any residual chlorine has been dechlorinated
  6. What is disinfection? -- Answer โœ”โœ” Process designed to kill most microorganisms in wastewater, including all essentially pathogenic bacteria
  1. What is fecal coliform bacteria? -- Answer โœ”โœ” Bacteria found in the feces of warm- blooded animals
  2. What is the Total coliform group? -- Answer โœ”โœ” All the aerobic and facultative anaerobic, gram-negative, non-spore-forming, rod-shaped bacteria that ferment the lactose in 24-48 hours at 35 degrees C
  3. Lab test results for an individual environmental sample within an analytical batch may be rejected when: -- Answer โœ”โœ” A known error has occurred
  4. How is precision measured? -- Answer โœ”โœ” Analyzing replicate samples
  5. What is Accuracy? -- Answer โœ”โœ” The combination of bias and precision of an analytical procedure, which reflects the closeness of a measured value to a true value
  6. What is Bias? -- Answer โœ”โœ” Consistent deviation of measured values from the true value, caused by systematic errors in a procedure
  7. What is Precision? -- Answer โœ”โœ” Measures the degree of agreement among replicate analyses of a sample, usually expressed as the standard deviation
  8. What is Random Error? -- Answer โœ”โœ” Consistent deviation of measured values from the true value, caused by systematic errors in a procedure

reagent-grade water, Step 3. Suction for 3 minutes after filtration is complete, Step 4. Transfer the total filtrate to a weighed evaporating dish and evaporate to dryness, Step 5. Dry evaporated sample for 1 hour at 180 +/- 2 degrees C Step 6. Cool and weigh to a constant weight

  1. What are Total Suspended Solids? -- Answer โœ”โœ” A well-mixed sample is filtered through a weighed standard glass fiber filter and the residue retained is dried to constant weight at 103-105 degrees C
  2. What is the Analysis procedure for total suspended solids? -- Answer โœ”โœ” Step 1. Wet the filter to seat it, Step 2. Pipet measured volume to filter, Step 3. Wash the filter with 3 successive 10 mL washes of reagent-grade water and continue suction for 3 minutes, Step 4. Dry for 1 hour in a 103-105 degree C oven, Step 5. Cool in a desiccator and weigh until constant weight
  3. Coliform density using fermentation techniques can be estimated using: -- Answer โœ”โœ” A probable number table
  4. How do you make a drinking water setup? -- Answer โœ”โœ” 10 replicate tubes, each containing 10 mL or 5 replicate tubes containing 20 mL
  5. What is the objective of a total coliform test? -- Answer โœ”โœ” Determine the efficiency of treatment plant operations and integrity of the distribution system
  6. How do you use Non-potable water for multiple-tube fermentation? -- Answer โœ”โœ” Inoculate a series of tubes with appropriate decimal dilutions of water (multiples of 10 mL)
  1. Which of the following is the presumptive phase of the Standard total coliform fermentation technique? -- Answer โœ”โœ” Use lauryl tryptose broth. Add dehydrated ingredients, mix, and heat to dissolve. Before sterilization, dispense Durham tube in fermentation tubes, sufficient medium to cover Durham 1/2 to 2/3 after sterilization, close tubes with metal or heat-resistant plastic caps
  2. Which of the following describes the procedure for the presumptive phase of the standard coliform fermentation technique? -- Answer โœ”โœ” Step 1. Shake samples vigorously 25 times, Step 2. Inoculate each tube in the set of five with replicate sample volumes, Step 3. Incubate inoculated tubes or bottles at 35 +/- 0.5 C. After 24 +/- 2 hours swirl gently and examine for growth, gas, or acidic reaction, reincubate and reexamine at the end of 48 +/- 3 hours
  3. Interpretation of the presumptive phase of the standard coliform fermentation technique can be described as: -- Answer โœ”โœ” A gas or acidic reaction within 48 +/- 3 hours constitutes a negative presumptive reaction. The absence of acid or gas is negative.
  4. Which of the following describes the procedure for the Confirmed phase for standard coliform fermentation? -- Answer โœ”โœ” Use brilliant green lactose bile broth, Add dehydrated ingredients, mix, and heat to dissolve, Before sterilization, dispense Durham tube in fermentation tubes, sufficient medium to cover Durham 1/2 to 2/ after sterilization, close tubes with metal or heat-resistant plastic caps, Autoclave at 121 C for 12 to 15 minutes, pH should be 7.2 +/- 0.2 after sterilization
  5. What is the Procedure for the confirmed phase of the standard coliform fermentation technique? -- Answer โœ”โœ” Step 1. Inoculate positive presumptive into BGB by resuspended organisms and transferring with sterile loop 3.0 to 3.5 mm in diameter, Step 2. Incubate at 35 +/- 0.5 C Step 3. Any gas formation in Durham tubes is a positive-confirmed phase
  1. What is the formula for bacterial count per milliliter? -- Answer โœ”โœ” CFU= colonies counted/ actual volume of sample plated, mL
  2. Enzyme Substrate Coliform Test utilizes what to detect total coliform bacteria and E Coli -- Answer โœ”โœ” Hydrolyzable substrates
  3. What is the purpose of the enzyme test of total coliform bacteria? -- Answer โœ”โœ” To detect all bacteria possessing the enzyme B-D- galactosidase, cleaves chromogenic substrate, releasing chromogen
  4. What is the purpose of the Enzyme test for E Coli? -- Answer โœ”โœ” To detect any bacteria giving positive total coliform response and possessing enzyme B- glucuronidase, cleaves fluorogenic substrate, releasing fluorogenic substrate
  5. What is the Principle of total coliform bacteria for the enzyme-substrate test? -- Answer โœ”โœ” Chromogenic substrates are used to detect the enzyme BD galactosidase, this enzyme hydrolyzes the substrate and produces a color change. Color change indicates a positive test for total coliforms at 18 and 24 h (ONPG) or 24 h (CPRG).
  6. What is the Principle of E Coli bacteria for enzyme-substrate tests? -- Answer โœ”โœ” Fluorogenic substrate is used to detect enzyme B glucuronidase, this enzyme hydrolyzes the substrate and produces a fluorescent product when viewed under long wavelength UV light, this is a positive test.
  7. Which of the following best describes the multiple tube procedure for enzyme- substrate test? -- Answer โœ”โœ” Step 1. Select the number of tubes per sample, Step 2.

Aseptically add 10 mL sample to each tube, and cap, and mix vigorously to dissolve, Step 3. Incubate at 35 +/- 0.5 degree C Note: can also be performed where substrate media is added to the sample and dispensed into 5 20 mL or ten 10 mL sterile tubes

  1. What is the Multi-well procedure for enzyme-substrate test? -- Answer โœ”โœ” Step 1. Add enzyme substrate to a 100 mL sample in a container, Step 2. Shake vigorously, Step 3. Pour into tray, Step 4. Seal the package, Step 5. Incubate at 35 +/- 0.5 degrees C for the period specified by the manufacturer, Step 6. Obtain MPN
  2. Describe the Presence-absence procedure for enzyme-substrate test: -- Answer โœ”โœ” Step 1. Aseptically add pre-weighed enzyme medium to 100 mL sample in sterile, transparent, nonfluorescent borosilicate glass. Step 2. Cap and mix to dissolve. Step
  1. Incubate as specified