CWEA grade 1 lab analyst practice test part 3

The hardness determination by EDTA titration measures:

Calcium and magnesium

The indicator for the hardness determination is:

Eriochrome Black T

EPA-acceptable primary standards for turbidity determination:

Formazin

BOD determination is an empirical test in which standardized lab procedures are used to:

determine the relative oxygen requirements of waste waters, effluents, and polluted waters

What's the protocol for sample pretreatment for BOD?

Assuring that the samples are neutralized to a pH range between 6.5 and 7.5 and any residual chlorine has been dechlorinated

What is disinfection?

Process designed to kill most microorganisms in wastewater, including all essentially pathogenic bacteria

What is fecal coliform bacteria?

Bacteria found in the feces of warm-blooded animals

What is the Total coliform group?

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

Lab test results for an individual environmental sample within an analytical batch may be rejected when:

A known error has occurred

How is precision measured?

Analyzing replicate samples

What is Accuracy?

The combination of bias and precision of an analytical procedure, which reflects the closeness of a measured value to a true value

What is Bias?

Consistent deviation of measured values from the true value, caused by systematic errors in a procedure

What is Precision?

Measures the degree of agreement among replicate analyses of a sample, usually expressed as the standard deviation

What is Random Error?

Consistent deviation of measured values from the true value, caused by systematic errors in a procedure

What are Total Solids?

Well mixed sample is evaporated in a weighed dish and dried to constant weight in an oven at 103-105 degrees C

Preparing Total solids evaporating dish:

Ignite clean evaporating dish at 550 furnace for 1 hour and store and cool in desicator

What is the Analysis procedure for total solids?

Step 1. Choose a sample volume that will yield residue between 2.5 and 200 mg, Step 2. Dry evaporated sample for 1 hour in 103-105 degrees C oven, Step 3. Cool in a desiccator and weigh to constant weight

What should the constant weight for total solids be?

Weight change is less than 4% of previous weight or 0.5 mg

What are Total Dissolved Solids?

A well-mixed sample is filtered through a standard glass fiber filter and the filtrate is evaporated to dryness in a weighed dish and dried to constant weight at 180 degrees C

How do you prepare a glass fiber filter disk?

Apply vacuum and wash disk with 3 successive 20 mL volumes of reagent-grade water (Deionized Water)

How do you prepare an evaporating dish for TDS and Volatile solids?

For volatile solids, Ignite the cleaned evaporating dish at 550 for 1 hour in a furnace. For TDS, heat the cleaned dish to 180 for 1 hour

What is the Analysis procedure for total dissolved solids?

Step 1. Stir the sample with a magnetic stirrer and pipet the measured volume onto a glass fiber filter with an applied vacuum, Step 2. Wash with 3 successive 10 ml volumes of 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

What are Total Suspended Solids?

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

What is the Analysis procedure for total suspended solids?

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

Coliform density using fermentation techniques can be estimated using:

A probable number table

How do you make a drinking water setup?

10 replicate tubes, each containing 10 mL or 5 replicate tubes containing 20 mL

What is the objective of a total coliform test?

Determine the efficiency of treatment plant operations and integrity of the distribution system

How do you use Non-potable water for multiple-tube fermentation?

Inoculate a series of tubes with appropriate decimal dilutions of water (multiples of 10 mL)

Which of the following is the presumptive phase of the Standard total coliform fermentation technique?

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

Which of the following describes the procedure for the presumptive phase of the standard coliform fermentation technique?

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

Interpretation of the presumptive phase of the standard coliform fermentation technique can be described as:

A gas or acidic reaction within 48 +/- 3 hours constitutes a negative presumptive reaction. The absence of acid or gas is negative.

Which of the following describes the procedure for the Confirmed phase for standard coliform fermentation?

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 2/3 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

What is the Procedure for the confirmed phase of the standard coliform fermentation technique?

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

Fecal coliform is also known as:

Thermotolerant coliforms - testing for ECOLI

Which of the following best describes a work area for Heterotrophic plate count?

Level table or bench top with ample area in a clean, draft-free, well-lighted room or within horizontal flow laminar hood. The table should have a nonporous surface and disinfected before analysis.

What is the procedure for Sample Preparation for Heterotrophic Plate Count?

Step 1. Mark the plate with the sample number, dilution, date, etc. Step 2. Prepare two replicate plates for each volume of sample or dilution examined. Step 3. Mix all samples by rapidly making 25 complete up and down movements

What is Plate count agar used for?

Pour and spread plate methods, high nutrient - pH should be 7.0 +/- 0.2 after autoclaving

What is m-Heterotrophic Plate Count agar used for?

Membrane filter method, high nutrient

What is the procedure for R2A agar?

Pour agar onto the plate, spread the plate, and use the membrane filter method, low nutrient gives higher counts

How do you sterilize agar?

At 121 C for 15 min

How do you Incubate a Heterotrophic Plate Count?

Incubate pour plates at 35 C for 48 hours - Humidity needs to be maintained so that agar plates will have no moisture weight loss greater than 15%

What is the formula for bacterial count per milliliter?

CFU= colonies counted/ actual volume of sample plated, mL

Enzyme Substrate Coliform Test utilizes what to detect total coliform bacteria and E Coli

Hydrolyzable substrates

What is the purpose of the enzyme test of total coliform bacteria?

To detect all bacteria possessing the enzyme B-D- galactosidase, cleaves chromogenic substrate, releasing chromogen

What is the purpose of the Enzyme test for E Coli?

To detect any bacteria giving positive total coliform response and possessing enzyme B-glucuronidase, cleaves fluorogenic substrate, releasing fluorogenic substrate

What is the Principle of total coliform bacteria for the enzyme-substrate test?

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).

What is the Principle of E Coli bacteria for enzyme-substrate tests?

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.

Which of the following best describes the multiple tube procedure for enzyme-substrate test?

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

What is the Multi-well procedure for enzyme-substrate test?

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

Describe the Presence-absence procedure for enzyme-substrate test:

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 3. Incubate as specified