Download Laboratory Procedure for Water Analysis: Bacterial Count, Enzyme Substrate Test, and BOD and more Exams Nursing in PDF only on Docsity!
CWEA GRADE 1 LABARATORY ANALYST
EXAMS |CURRENTLY TESTING VERSION
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Disinfection Process designed to kill most microorganisms in wastewater, including all essentially pathogenic bacteria Fecal coliform bacteria Bacteria found in feces of warm blooded animals Total coliform group All of the aerobic and faculative anaerobic, gram negative, nonspore-forming, rod shaped bacteria that ferment 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 occured Precision is measured by Analyzing replicate samples Accuracy The combination of bias and precision of an analytical procedure, which reflects the closeness of a measured value to a true value Bias Consistent deviation of measured values from the true value, caused by systematic errors in a procedure Precision Measures the degree of agreement among replicate analyses of a sample, usually expressed as the standard deviation Random Error Consistent deviation of measured values from the true value, caused by systematic errors in a procedure Total Solids
Well mixed sample is evaporated in a weighed dish and dried to constant weight in an oven at 103- degrees C Preparing Total solids evaporating dish Ignite clean evaporating dish at 550 furnace for 1 hour and store and cool in desicator Analysis procedure of total solids
- Choose sample volume that will yield residue between 2.5 and 200 mg
- Dry evaporated sample for 1 hour in 103-105 degree C oven
- Cool in desicator and weigh to constant weight Constant weight for total solids Weight change is less than 4% of previous weight or 0.5 mg Total Dissolved Solids A well mixed sample is filtered through standard glass fiber filter and filtrate is evaporated to dryness in weighed dish and dried to constant weight at 180 degrees C Preparing glass fiber filter disk Apply vacuum and wash disk with 3 successive 20 mL volumes of reagent grade water Preparing evaporating dish for TDS If volatile solids, Ignite cleaned evaporating dish at 550 for 1 hour in furnace
If only TDS, heat cleaned dish to 180 for 1 hour Analysis procedure of total dissolved solids
- Stir sample with magnetic stirrer and pipet measured volume onto glass fiber filter with applied vacuum
- Wash with 3 successive 10 ml volumes of reagent grade water
- Suction for 3 minutes after filtration is complete
- Transfer total filtrate to weighed evaporating dish and evaporate to dryness
- Dry evaporated sample for 1 hour in 180 +/- 2 degree C
- Cool and weigh to constant weight Total Suspended Solids A well mixed sample filtered through weighed standard glass fiber filter and residue retained is dried to constant weight at 103-105 degrees C Analysis procedure of total suspended solids
- Wet filter to seat it
- Pipet measured volume to filter
- Wash filter with 3 successive 10 mL wash of reagent grade water and continue suction for 3 minutes
- Incubate at 35 +/- 0.5 C
- Any gas formation in durham tubes is positive confirmed phase Fecal coliform is aka thermotolerant coliforms
- TESTING FOR ECOLI Work area for Heterotrophic plate count Level table or bench top wih ample area in a clean, draft free, well lighted room or within horizontal flow laminar hood. Table should have nonporous surface and disinfected before analysis. Sample preparation for HPC
- Mark plate with sample number, dilution, date, etc
- Prepare two replicate plates for each volume of sample or dilution examined
- Mix all samples by rapidly making 25 complete up and down movements Plate count agar is used for Pour and spread plate methods, high nutrient
- pH should be 7.0 +/- 0.2 after autoclaving m-HPC agar is used for membrane filter method, high nutrient R2A agar Pour plate, spread plate, and membrane filter method, low nutrient gives higher counts Sterilization of agar 121 C for 15 min Incubation of HPC Incubate pour plates at 35 C for 48 hours
- Humidity needs to be be maintained so that agar plates will have no moisture weight loss greater than 15% 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 subtrates Enzyme test of total coliform bacteria All bacteria possessing the enzyme B-D- galactosidase, cleaves chromogenic substrate, releasing chromogen
Enzyme test of E Coli Bacteria giving positive total coliform response and possessing enzyme B-glucuronidase, cleaves fluorogenic substrate, releasing fluorogen Principle of total coliform bacteria for enzyme substrate test Chromogenic substrate (ei. ortho-nitrophenyl B D galactopyranoside (ONPG) or chlorophenol red B D galactopyranoside (CPRG) are used to detect enzyme BD galactosidase, this enzyme hydolyzes substrate and produces color change. Color change indicates positive test for total coliforms at 18 and 24 h (ONPG) or 24 h (CPRG). Principle of E Coli bacteria for enzyme substrate test Fluorogenic substrate is used to detect enzyme B glucuronidase, this enzyme hydrolyzes the substrate and produces fluorescent product when viewed under long wavelength UV light, this is a positive test. Multiple tube procedure for enzyme substrate test
- Select number of tubes per sample
- Aseptically add 10 mL sample to each tube, cap, and mix vigorously to dissolve
- Incubate at 35 +/- 0.5 degree C Note: can also be performed where substrate media is added to the sample and dispensing into 5 20 mL or ten 10 mL sterile tubes Multi well procedure for enzyme substrate test
- Add enzyme substrate to a 100 mL sample in a container
- shake vigorously
- Pour into tray
- Seal package
- Incubate at 35 +/- 0.5 degree C for period specified by manufacturer
- Obtain MPN Presence absence procedure for enzyme substrate test
- Aseptically add pre weighed enzyme medium to 100 mL sample in sterile, transparent, nonfluorescent borosilicate glass.
- Cap and mix to dissolve
- Incubate as specified Interpretation for total coliform and E coli for enzyme substrate test Grab samples Single samples collected at a specific spot at a site over a short period of time (not to exceed 15 min) Sample is in a persons custody if In the individual's physical possession, sight, secured and tampered proof by that individual, or secured in an area restricted to authorized personnel
Sampling protocol for chlorine residual Plastic, glass, fluoropolymer, analyze immediately (no preservative since chlorine changes rapidly) Sampling protocol for Color Plastic, glass, cool </= 6 C Sample protocol for hardness Plastic, glass, fluoropolymer, no preservative required Sample protocol for dissolved oxygen (electrode) Glass, BOD bottle, analyze immediately Sample protocol for pH Plastic, glass, analyze immediately Sample protocol for solids Plastic, glass, cool </= 6 C Concentration units for chemical and physical results (mass units)/L Grab sample preparation for BOD
- Cold storage is unnecessary if analysis is within 2 hrs, if not keep at </= 4 C
- Begin analysis within 6 hrs
- No analysis after 24 hr of grab collection Composite sample preparation for BOD
- Keep samples </= 4 C during compositing
- Limit compositing period to 24 hr pH sample prep for BOD If not between 6.0 and 8.0 adjust sample temp to 20+/-3 C, then adjust pH to 7.0 to 7.2 using sulfuric acid (h2SO4) or sodium hydroxide (NaOH) Residual Chlorine in samples for BOD Dechlorinate sample using Na2SO3 solution BOD samples supersaturated with DO Samples with Hydrogen peroxide with DO Mix samples vigorously in open containers for sufficient time to allow hydrogen peroxide levels to dissipate
Seed suspension for BOD analysis Preferred seeds include supernatant from settled domestic wastewater, effluent from primary clarifiers, diluted mixed liquor from an aeration basin, disinfected effluent, or receiving water from below the point of discharge Dilution water preparation for BOD
- DO concentration is 7.5 mg/L
- Add 1 mL each of phosphate buffer, MgSO4, CaCl2, and FeCl3 solution/L to prepared source water Sample temperature adjustment for BOD Bring samples to 20 +/-3 C Samples that require nitrification inhibition Biologically treated effluents, samples seeded with biologically treated effluents, and river water Sealing BOD bottles Fill each bottle enough to where insertion of stopper leaves no bubbles in bottle. Mix sample by turning bottle manually several times Initial DO measurement Measure initial DO within 30 minutes after preparing dilution Incubation of BOD Incubate at 20 +/- 1 C without light for 5 days +/- 6 hours Valid data of BOD analysis
- Minimum depletion of 2.0 mg/L DO
- Residual DO of 1.0 mg/L Primary basis of precision and accuracy in BOD analysis Glucose-glutamic acid check Definition of pH The negative logarithm of the hydrogen ion concentration in moles per liter One unit change in pH represents what A ten fold change in the concentration of the hydrogen ion Ex. pH change from 6 to 5 means a 10 fold increase in hydrogen ion concentration has occurred Calibration of pH instrument Use two buffers which bracket the expected pH value for greatest accuracy Temperature instruments
Holding time for alkalinity 14 days Holding time for BOD 48 hours Holding time for COD 28 days Holding time for chloride 28 days Holding time for chlorine, total, residual 0.25 hours Holding time for color 48 hours Holding time for odor 24 hours Holding time for pH 0.25 hours Holding time for solids 7 days Holding time for temperature 0.25 hours Holding time for turbidity 48 hours Interference of turbidity analysis Dirty bottles pH meter ranges Should be reproducible to 0.1 pH unit and range of 0- Short term storage of pH electrodes pH 4 buffer pH meter calibration
- Place in initial buffer solution and set isopotential point
- Select second buffer within 2 pH units Chloride
- Major anion found in many natural waters
- Can impart salty taste in H2O What increases concentration of chloride in wastewater Chloride in human diet and softeners flushed into sanitary sewer system 2 most prevalent methods of measuring chloride argentometric and mercuric nitrate Argentometric Titration of sample with standard solution of silver nitrate (AgNO3)
- Indicator: Chromate ions (CrO4)
- End point: reddish silver chromate Mercuric Nitrate Titration with standard mercuric nitrate solution -pH must be adjusted between 2.3 and 2.
- Indicator: Diphenyl carbazone
- End point: Change from blue to purple in presence of mercury Interference of Mercuric Nitrate Method Sulfide, bromide, orthophosphate (over 30 ppm), and iodide Why does color change in water Presence of decaying vegetable matter, metal ions (ie. iron) or industrial and domestic pollution How is color measured Measured using visual comparison method Visual comparison method Sample compared to standards using matched nessler tubes
- Standards prepared with solution containing cholorplatinate and cobaltous chloride Standard units for color One unit= color resulting from 1 mg of platinum/L 2 color reporting True and Apparent True color
The pH is greater than 8. Atomic Weight: The sum of the number of protons and the number of neutrons in the nucleus of an atom. Atomic weights of elements are found on periodic tables. Base: A compound which liberates hydroxide ions and has a pH above 7. Biochemical Oxygen Demand (BOD): The quantity of oxygen utilized in the biochemical oxidation of organic matter under standard laboratory procedures for five days at 20° Centigrade, usually expressed as a concentration (e.g., mg/L). BOD measurements are used to indicate the organic "strength" of wastewater. Chain-of-Custody: A legal record (which may be a series of records) of each person who had possession of an environmental sample, from the person releasing the sample, to the person who collected the sample, to the person who analyzed the sample in the laboratory, to the person who witnessed the disposal of the sample. Chemical Oxygen Demand (COD): The amount of oxygen (expressed in mg/L) consumed from the oxidation of pollutants during a specific test. As such, COD is a measure of the oxygen-consuming capacity of the pollutants present in wastewater. The results of the COD test are not necessarily related to the BOD, because the chemical oxidant responsible for utilizing the oxygen may react with substances which bacteria do not stabilize. Composite Sample: A collection of individual samples obtained at regular intervals, based either on flow or time. The individual samples are combined proportionally. .If you have been given instructions you dont understand Ask the author Mercuric nitrate titration technique for measureing chloride is falling into disuse in the lab because Mercury creates a hazardous waste problem Standard phenylarsine oxide solution (PAO) Should be handled with caution because its is a severe poison
Sampling protocol for chloride includes Glass or plastic container with no preservative Incubator temperature for BOD 20 +/- 1 degrees C Laboratory mistakes may be corrected by Lining out the mistake with pen and writing the correct answer to the side of the first, with analysts initials and date The sample receiving log must record time and date sampled Sample collector, nature of sample, analyses to be performed, preservatives, condition of sample and sample recipient Hood flow should be monitored and documented at 100 linear feet per minute Normality equation (N1)(V1)=(N2)(V2) Lauryl Sulfate Broth is sterilized before use for 15 minutes at 121 degrees C Agar medium is used for Heterotrophic plate count During acid base titration, titrant is added to the sample with Buret When preparing diluted calibration standards from a stock standard, use combination of the following to get the most precise standard Class A volumetric flask and class A volumetric pipet At a given temperature, the intensity of the acidic or basic character of a solution is indicated by pH or hydrogen ion activity pH measurement requires the following voltmeter, glass pH electrode, reference electrode, and a temperature compensating device Conductance measurements are temperature compensated to 25 degrees C Conductivity meter is calibrated with
maintain overall saftey of permited confied space operations What should be the alarm set point for oxygen in an atmospheric monitoring/testing device? 19.5% Warning,caution,danger,on a label means Hazardous MSDS means Material Data Safety Sheet What is the purpose of the OSHA Hazard Communication SHeet To make sure employees know about any hazardous chemicals they may contact How can traffic be warned of your presence in the street? Signs,Cones,Flagman What check should be preformed before driving a vehicle? Mechanical/Safety Where will collection system operators most likely find black windows Spiders and scorpions. Manholes Typical safety hazards in collections system operations include Oxygen defiency You have an air compressor and you have been instructed to compact the backfill in a trench. Which of the following is the best tool to use? Tamper Which type of shovel do collection system technologist use Grit Shovel What type of saw is used to cut asphalt? Diamond bladed or toothed power saw Googles, earplugs, and glove are needed when using a Power Grinder What type of equipment should be used to excavate a broken sewer pipe? Backhoe What is a mechanical means to dislodge material from a sewer?
Scraping The formula for calculating the volume of a wet well is V=W L H Tasks preformed by a collection system operator includes: Maintaining collection system equipment One cubic food per second flow is equal to 26,928 Gallons To properly operate a power rodder Make sure all the torque is out of it before handling. The diameter of a wet well is 10 feet. If filled to a depth of 10 feet, it will contain approximately Show Work = 5,872 Gallons What is an orifice plate? A plate with a small hole in it to restrict the flow.
