Basic Laboratory Study Guide

Laboratory control sample

"LCS" means a sample of an inert matrix or a matrix with a consistent concentration of the analytes of interest, fortified with a verified known amount of the analytes of interest. The purpose of an LCS is to determine whether the methodology is in control and whether the laboratory is capable of making accurate and precise measurements.

What is a Laboratory Control Standard (LCS)?

"Laboratory Control Standard" or "LCS" means a sample prepared by the laboratory, using reagent water, to which a known amount of the analyte of interest is added.. The purpose of an LCS is to determine whether the methodology is in control and whether the laboratory is capable of making accurate and precise measurements.

The significance of the ammonia test in wastewater testing

- Ammonia is a major excretory product of animals and is toxic to organisms at high pH levels. - Approximately 60% of the nitrogen entering a wastewater plant is ammonia. - Ammonia toxicity is based on pH and temperature. - Ammonia affects wastewater plants differently based on type or design. - High levels of ammonia and the presence of nitrifying organisms will result in increased BOD values

What is a "second source" standard

- LFP (laboratory fortified blank)

Documentation required for corrective action.

- WHEN did you become aware of the problem? - HOW did you become aware of the problem? - WHO initiated corrective action to resolve the problem? - WHAT action did you take to fix the problem? WHAT data was affected? - WHY do feel the action was appropriate (how do you know the problem has been resolved)?

Split samples are used to:

1. Assess the variability from sample processing and preservation. 2. Assess the precision of laboratory analysis by allowing a comparison of analytical results from two parts of the same sample from the same location. 3. Verify compliance with discharge permits when "split" with Wisconsin Department of Natural Resource staff during compliance inspections

The requirement for the glucose-glutamic acid (GGA) check is a BOD result of

198 ± 30.5 mg/L

Incubation time and temperature requirements for BOD samples.

20 + or - 1 degrees Celsius, 5 day incubation

holding Time & Preservation: Ammonia

28 Days Add sulfuric acid (H2SO4) to pH <2 and cool to 6 degrees Celsius or less, without freezing

holding Time & Preservation: Total P

28 Days Add sulfuric acid (H2SO4) to pH <2 and cool to 6 degrees Celsius or less, without freezing

holding Time & Preservation: BOD

48 hours after compositing cool to 6 degrees Celsius or less, without freezing

holding Time & Preservation: Fecal Coliform

6 hours Add sodium thiosulfate if sample was chlorinated and cool to 6 degrees Celsius or less, without freezing

holding Time & Preservation: TSS

7 Days cool to 6 degrees Celsius or less, without freezing

Under typical conditions, at saturation in Wisconsin, initial DO should be about

8.2 - 8.5 mg/L Final DO cannot be less then 1 mg/L - working range of DOs for any dilution is about 7.5

Equipment required to calibrate a DO meter.

A barometer, or pressure obtained from a local source and adjusted for elevation, is required to obtain an accurate pressure reading that is corrected for altitude. All modern DO meters are equipped with on-board barometers. On-board barometers are more than satisfactory so an external should not be used. A thermometer is required to determine the temperatures of the dilution water used to calibrate the DO meter. 5.3.1 Equipment required to calibrate a DO meter. Basic Laboratory Study Guide - August 2015 Page 18 of 49 Printed on 08/28/15 A DO saturation table, chart (or properly vetted algorithm) is required to determine the saturation point based on calibration solution temperature and barometric pressure.

Flow proportional composite samples

A composite sample represents a longer period in time. It is far more likely to represent the average quality of the water being received or discharged, especially if waste characteristics change with time. Flow proportional composite samples are required for most wastewater plants. The exception is pond effluent, which is thought to have such a long detention time that the variations of loading do not affect it

Desiccator function

A desiccator is used to maintain a humidity-free environment. Oven-dried samples, glassware, and some chemicals should be stored in a desiccator before weighing to prevent moisture absorption. In the wastewater laboratory, a desiccator is used to cool TSS samples filters after drying. Absorbed moisture adds weight to the samples, causing incorrect weight measurements. In order for a desiccator to work properly, it must contain color indicating desicant and the lid must have a silicone based grease seal or a rubber gasket seal. The color of indicating desiccant changes from blue to pink as it absorbs moisture. Blue silica gel changes from deep blue to pale pink as it absorbs moisture. Once the material turns pink, the desiccant must be re-generated by heating in a drying oven at the manufacturer-specified temperature to drive off absorbed moisture or be replaced.

Proper preparation of calibration standards

A good calibration curve is dependent on many factors. The first thing you need is a very accurate measuring device for making your calibration standards. When preparing a standard solution, be sure to use a volumetric pipet or mechanical pipet for accurate volumetric measurement. If volumetric pipets are inaccurate then your curve is most likely going to show it. The main thing you need to be careful with is how you handle your standards before you measure them; any errors you make will show in your curve. Calibration standards are made by diluting a stock analyte solution in volumetric flasks.

Grab samples

A grab sample represents a single instant in time. It is subject to much more fluctuation than a composite sample. Generally, a grab sample is only used if the sample holding time would significantly change the parameter being tested, or if measurement of a slug loading is desired

Preferred reagent used to prepare standards in the ISE determination of total residual chlorine

A potassium iodate (KIO3) solution is used as a chlorine equivalent. A solution containing 0.1005 g/L of potassium iodate has a chlorine equivalent of 100 mg/L. Chlorine standards can be prepared using household bleach formulations, but standards prepared from bleach are unstable. The iodate standards are much more stable.

TSS requirements for solids capture on filters.

A residue of at least 1 mg, and not more than 200 mg, must be captured on the filter. If at least 500 mL of sample volume is filtered and 1 mg of residue is not obtained, the analyst is not required to repeat the analysis using more sample volume. A minimum capture weight of 1 mg and 500 mL of sample filtered is required to report an LOD of 2 mg/L, the required LOD for Discharge Monitoring Report (DMR) reporting for effluent samples.

How are BOD samples "seeded"?

A small volume of concentrated seed material can be added to individual sample dilutions. Alternatively, you can seed dilution water and then all samples that are diluted to any extent are provided with a population of microorganisms. Either practice is acceptable Seeding dilution water ensures all samples are seeded, but seeding individual samples makes calculating seed correction factors a much easier task. Seeding individual samples works best.

What is a standard?

A standard is a solution which consists of a known and documented concentration of a target analyte (e.g., 100 ppm phosphorus solution). Standards are used as reference material to determine the concentration of a target analyte in an unknown sample. The instrument response relative to the concentration of standards is compared to that of the unknown samples to determine the concentration. Standards should be prepared in a solution similar to the samples being tested. For example, if you are measuring phosphorus in wastewater, you should prepare the standards in water.

Pipet accuracy

All pipets are associated with a degree of accuracy. Generally, the error (inaccuracy) increases as the volume of the pipet decreases. For example, a 1 mL Class A volumetric pipet may have an associated error of 0.6%, while the error for a 10 mL Class A volumetric pipet is 0.2%. A single larger volume pipet, therefore, is more appropriate for measuring volumes than two smaller volume pipets. That is because error is additive. One could use a single 10 mL volumetric pipet to dispense a standard with 0.2% error, or use a 1 mL pipe ten times for a combined error of 6.0%. In addition, using a small pipet multiple times instead of a larger pipet a single time only increases your risk of introducing contamination.

The relationship between ammonia concentration and electrode response time.

As ammonia concentration decreases electrode response time increases. The lower the concentration of ammonia in the sample, the fewer the number of ammonia molecules as gas that pass across the membrane to react with water and trigger a pH change observed as a millivolt increase on the meter.

Define BOD.

BOD = Biochemical Oxygen Demand BOD is a test used to measure the amount of oxygen consumed by bacteria as they decompose organic matter in a sample of water. It can be used to infer the general quality of the water and its degree of pollution by biodegradable organic matter. It is used in water quality management and assessment, ecology and environmental science. In a nutshell, BOD gives a measure on the impact of a waste(water) on the oxygen content of a receiving system(stream/river/lake). Wastes are broken down by microbial organisms (frequently referred to as "bugs"), and the bugs, in turn, require oxygen. Thus, in order for this 5.1.1 Define BOD. Basic Laboratory Study Guide - August 2015 Page 14 of 49 Printed on 08/28/15 test to "work", you need (1) a food source, (2) a population of bugs, (3) available oxygen fuel, and (4) a system which provides a hospitable environment for the bugs.

The significance of BOD in wastewater testing

BOD is used to assess the relative strength of a waste. It measures the amount of oxygen required to stabilize a waste if it is discharged to a surface water. BOD is the most commonly required test on WPDES and NPDES discharge permits. It is widely used in facility design planning and is used to gauge the effectiveness of wastewater treatment plants once in operation. The critical function of the BOD test is to provide a means to assess waste loading on surface waters. By looking at the potential for a waste to utilize oxygen, we can evaluate the potential impacts downstream, including those on fish.

Define Bias (accuracy)

Bias (Accuracy) is the systematic or persistent error in an analysis which results in the expected sample measurement being consistently different than the sample's true value. A systematic bias is a bias resulting from a flaw integral to the system within which the bias arises (for example, an incorrectly calibrated thermostat may consistently read - that is 'biased' - several degrees hotter or colder than actual temperature). As a consequence, systematic bias commonly leads to systematic errors, as opposed to random errors, which tend to cancel one another out.

Define carbonaceous BOD (cBOD)

Carbonaceous BOD (cBOD) is a specific part of "total" BOD which represents the amount of oxygen demand required to break down carbon sources only. Total BOD measures the oxygen consumption associated with microbial breakdown of a waste, including both carbonaceous and nitrogenous sources. cBOD is measured by adding a pyridine-based inhibiting agent to the sample prior to incubation during the BOD test. This chemical inhibits the ability of the bacteria, Nitrosomonas sp., to convert ammonia to nitrite, which is the first phase of the nitrification process. By inhibiting this activity, the test measures only the oxygen utilized by microorganisms to breakdown carbonaceous waste.

What does "corrective action" mean

Corrective action means any measure taken to correct and prevent the recurrence of the causes of any exceedance of expected analytical operating conditions or quality control acceptance criteria. Corrective action must be documented. Corrective action must be designed to identify the reason for the failure, and then correct it. There should also be a plan to quickly verify that the action taken has the desired effect.

Define dissolved oxygen

Dissolved oxygen (DO) is defined as oxygen (O2) molecules dissolved in water. Dissolved oxygen cannot be seen, so small bubbles are not actually considered to be "dissolved" oxygen. Oxygen becomes dissolved in water in one of two ways: it either dissolves into water from contact (diffusion) with the atmosphere or is produced by plants as a byproduct of photosynthesis. Dissolved oxygen concentration is related to the following: 1) temperature (as water temperature increases, it is able to hold LESS oxygen) 2) atmospheric pressure (as air pressure increases, water is able to hold MORE oxygen)

Critical requirements for a TSS drying oven.

Drying ovens used for TSS determinations must be able to consistently maintain a temperature of 103-105°C (104 ± 1°C). The purpose of the method temperature is to drive off water but not lose volatile solids. Drying ovens should be vented properly as a health and safety precaution. Do not position a drying oven directly beneath an HVAC blower vent because drafts can be forced through the top of the oven. Direct contact with blowing cold air prevents the ability of the oven to maintain constant temperature. Ovens can be vented, but should not be placed directly inside any hood. Placing the oven in a hood will disrupt air flow and the hood will not work properly. Preferably, ovens should be vented using a snorkel or canopy type vent. Can be vented too, but should not be placed inside any hood.

How is a seed correction factor (SCF) calculated?

EXAMPLE: Seed Control 1 Volume = 10 mL Initial DO = 8.50 mg/L Final DO = 5.50 mg/L Seed Control 2 Volume = 20 mL Initial DO = 8.50 mg/L Final DO = 2.70 mg/L average both seed factors

Using BOD:TSS ratios as a tool to identify nitrification

Generally speaking there should be a 1:1 relationship between BOD and TSS results for domestic municipal wastewater effluent. This relationship only applies to domestic wastewater effluents. This is because the majority of the BOD comes directly from the material that makes up the TSS. Industrial wastes, such as dairy and food processing wastes, contain a high dissolved BOD component. Milks and sugars from food wastes will pass through the TSS filters causing the BOD to be significantly higher than the TSS values. If BOD is always significantly higher than TSS (e.g., TSS 10, BOD 25), nitrification is likely occurring. Confirm by performing side-by-side BOD tests with and without nitrification inhibitors (e.g, determine both BOD and carbonaceous BOD (cBOD). If the inhibited (carbonaceous) BOD results are significantly lower and closer to the TSS results, nitrification is occurring. Repeat side-by-side tests to confirm your findings.

Normality

Gram equivalent weight of solute per liter of solution, often denoted by N.

DO depletion requirements for BOD testing.

In order to be used to calculate sample results without qualification, dilutions must deplete at least 2 mg/L of DO, and the final (or residual ) DO must be at least 1.0 mg/L.

Define LOD and LOQ

Limit of detection (LOD) means the lowest concentration or amount of analyte that can be identified, measured, and reported with confidence that the concentration is statistically different from a blank (or, not a false positive value). For department purposes, the LOD approximates the "method detection limit" (MDL, the term used by the EPA and in many methods). The LOD is determined using the procedure in 40 CFR Part 136 Appendix B, Revision 1.11. Limit of quantitation or (LOQ) means the lowest concentration or amount of an analyte for which quantitative results can be obtained with a specified degree of confidence. The limit of quantitation is typically considered to be a value 10/3 or 3.333 times the limit of detection (LOD).

What is nitrogenous oxygen demand?

Nitrogenous oxygen demand is the amount of oxygen consumed during the biochemical conversion of organic nitrogen and ammonia to nitrate nitrogen. This process is called nitrification. We are primarily concerned with the inorganic forms, and specifically, ammonia nitrogen. This means that if the wastewater contains ammonia (and most do, particularly lagoons) AND the nitrifying bacteria are present, then oxygen can be consumed in the conversion of nitrogen forms. The oxygen consumed is measured as BOD, leading to BOD results biased high. Ammonia + Oxygen -> Nitrite -> Nitrate

Proper pipets to be used for BOD and TSS tests

Only wide-bore volumetric pipets are to be used for the BOD and TSS tests when less than 100 mL of sample is needed. These pipets have a wide-bore opening which are useful when transferring samples that contain particulates such as raw wastewater. When pipetting samples with visible suspended solids, wide-bore pipets are more accurate because narrow-bore can serve to block or strain solids particles from the sample.

The significance of total phosphorus in wastewater testing

Phosphorus is a vital nutrient for plant growth and for metabolic reactions of all other life forms. Phosphorus is often a limiting factor for algal growth. Consequently, the more phosphorus that is discharged to receiving stream systems, the greater the likelihood of algae and aquatic weed growth downstream. Phosphorus in wastewater is usually present in the form of organic compounds and phosphates that can easily be removed by chemical precipitation. This process, however, increases the volume and weight of sludge. It has been estimated that the human body releases about a pound of phosphorus per year.

AIR-SATURATED WATER (ASW)

Place the probe in a BOD bottle filled with air-saturated (well-shaken) water. • Leave probe in the water w/ stirrer operating long enough for the probe temperature to equalize with the water temperature; generally about 5 minutes. • Determine barometric pressure from the on-board barometer if so equipped. • Check the temperature of source water to be sure the probe thermistor is working correctly. This is also determined using the thermometer on-board the DO meter. • Use a detailed DO saturation table to determine the theoretical DO concentration. • Manually adjust the meter to read the DO concentration determined from the saturation table

Define precision

Precision is a measure of how closely multiple determinations performed on the same sample will agree with each other. Accuracy is the degree of closeness to the actual value while precision is the degree of reproducibility. Using the typical "target" analogy, if a large number of arrows are fired at the target, the size of the arrow cluster on the target represents the shooter's precision. When all arrows are grouped tightly together, the cluster is considered precise since they all struck close to the same spot. Note that the cluster may be very precise, by virtue of a tight grouping, but if the cluster is nowhere near the bullseye, then the shooter is precise but not accurate.

Define Quality Control Standard (QCS).

Quality Control Standard or "QCS" means an externally obtained solution or sample containing method analyte of known concentration, accompanied by specified analytical acceptance limits, and different from the source of calibration standards. These samples are distinguished from proficiency test samples in that the acceptance limits are provided with the sample, rather than after analysis. Quality control standards are used to check either laboratory or instrument performance. These types of samples are important indicators of quality because instantaneous feedback on performance is provided. This offers the analyst an opportunity to correct any analytical problems in a timely manner. Quality Control Standards are analyzed every four months as a check on analytical performance. Appropriate measures are taken to investigate problems when the result of a QCS analysis is inconsistent with past results.

What is reagent water

Reagent water is water which has been treated to remove any impurities that may affect the quality of sample analysis. You may see this referred to as laboratory reagent water, laboratory pure water, distilled water, or deionized water. Reagent water used for analyses is typically classified as either ASTM Type I or Type II.

Important considerations for seed controls

Seed material itself causes a DO depletion. Therefore depletion due to seed material must be subtracted from the total DO depletion of each seeded sample dilution prior to calculating BOD for the original sample. When samples are seeded, an accurate BOD determination depends on the ability to account for the DO depletion due to the seed material in each sample dilution. This is accomplished by determining a seed correction factor. Seed controls must be treated just like any other sample, since we are really trying to accurately determine the BOD of the seed material. Therefore at least two dilutions of seed material are required, and the method specified DO depletion criteria must be met. Seed controls are required on each day that any samples/QC are seeded.

When is seeding required for wastewater samples?

Seeding is required whenever any sample is collected downstream of any disinfection, whenever sample pH requires adjustment, and also when inhibitor is added for cBOD determination. Sample pH extremes will severely shock or kill microorganisms. Therefore, when sample pH adjustment is required, subsequent sample dilutions must be seeded.

serological pipette/ Mohr

Serological or Mohr pipets which should be "drained out" typically have their graduated markings stop prior to the tip. Volume should not be drained below the last marking. These pipets are usually identified by the presence of a color-coded rectangle or square (but no frosted or colored rings) at the top of the pipet.

What are SOPs (Standard Operating Procedures).

Standard operating procedures (SOP) are used to describe a procedure or set of procedures to perform a given task, analysis, or in response to a specific event or situation. SOPs often offer guidance where official methods are lacking, or are extremely broad. SOPs typically provide practical detail to the sometimes generic language provided in methods or to identify specific situations where choices are available. Every good quality system is based on its standard operating procedures (SOPs).

Define super-saturation.

Supersaturation means that the water contains more DO than it SHOULD contain according to physical tables The method suggests that super-saturation is anything above 9.0 mg/L. However, in reality saturation will vary with temperature and pressure. Consult a DO saturation table. CONDITIONS THAT FAVOR SO SUPER-SATURATION IN SAMPLES • Super-saturation can occur during winter months (the colder the water, the more oxygen it can hold). • Super-saturation can also be a problem in localities where algae are actively growing (e.g., lagoons).

How atmospheric pressure and temperature affect DO calibration

The concentration of dissolved oxygen (DO) in water is dependent on both temperature and atmospheric pressure. As the temperature of water increases, its ability to hold oxygen (DO saturation point) decreases. Conversely, as temperature decreases, the water can hold more DO. This explains why fish in an aquarium become stressed and may die if the water temperature is too high. The water can simply no longer hold enough oxygen for the fish to survive. In natural systems, this can result in a "fish kill"

What options are available for use as BOD seed material.

The first is to utilize a sample from some aspect of the treatment process. Settled primary wastewater or mixed liquor are generally the best sources. Alternatively, there are several commercially available synthetic

Identifying sample toxicity affecting BOD results

The first symptom of sample toxicity is evidenced by a decrease in BOD concentration as sample volume increases. What this really means is that we're looking for a trend, and a trend realistically requires more than two data points. If only two dilutions are used, and the dilution with greater sample volume yields a lower BOD result, it COULD merely be a function of sample homogeneity. Having an additional dilution which confirms the initial two dilutions serves as a referee. Therefore, at least three (3) dilutions are necessary to effectively detect sample toxicity

Testing differences between BOD and cBOD

The only difference between samples analyzed for BOD and those analyzed for cBOD is NOT the letter "c". The key difference between samples analyzed for BOD and those analyzed for cBOD is more precisely the addition of a chemical inhibitor to all samples for which cBOD is determined. If nitrification was occurring in the original sample, the cBOD result is expected to be lower than the BOD result. The difference between the results represents the amount of oxygen which is consumed during the nitrification process. Since the BOD test only measures oxygen consumed, performing both BOD and cBOD is the only way to distinguish the amount of oxygen consumed during decomposition of organic waste from that which is consumed during nitrification

Sources and control of contamination in phosphorus analysis.

The phosphorus test is extremely sensitive at even trace levels. Phosphorus is all around us, so it is a very easy test to contaminate. Common sources of contamination include: treated (for sequestration of iron and manganese) tap water, oils on fingers, tobacco residue, soap and some detergents, and laboratory buffers buffers (including solutions used to calibrate pH meters) or other reagents. Be sure to clean glassware thoroughly, and maintain laboratory cleanliness. Blanks and standards are critical in monitoring for phosphorus contamination. Keeping records of the absorbance of blanks and standards over time will help detect changes in reagent water quality or reagents.

What is the purpose of "seeding" BOD samples

The purpose of seeding is to ensure that an adequate population of viable microorganisms is available to breakdown any waste material, utilizing oxygen during the process. Microorganisms are a critical component of the BOD test, as it is the oxygen they utilize during the breakdown of organic matter which is measured by the BOD test. Consequently, whenever there is suspicion that a sample may not contain an adequate population of microorganisms, sample dilutions must be "seeded" with microorganisms obtained as either commercially purchased synthetic seed, or preferably as a portion of process water, such as settled primary or mixed liquor, from a treatment plant.

BOD incubators specifications

Thermostatically controlled at 20 ± 1°C. All light must be excluded to prevent photosynthesis during the 5-day incubation period. The temperature of the incubator must be documented daily when samples are being incubated.

What is the significance of the TSS test in wastewater testing?

Total suspended solids (TSS) are those which are visible and in suspension in the water. They are the solids which can be removed from wastewater by physical or mechanical means such as sedimentation, flocculation, or filtration. TSS will include the larger floating particles and consist of silt, grit, clay, fecal solids, paper, fibers, particles of food, garbage, and similar materials. Suspended solids are approximately 70% organic and 30% inorganic. TSS determinations may be used to assess wastewater strength, process efficiency, and loadings. By reducing the TSS in your effluent discharge, you are going to get better disinfection, which will reduce your fecal coliform and/or E. coli counts, allowing you to maintain compliance.

What is Total Suspended Solids (TSS)?

Total suspended solids (TSS) is a water quality measurement, generally required for wastewater treatment plant outfalls. This test can also be called non-filterable residue (NFR), a term that refers to the identical measurement: the dry-weight of particles trapped by a filter, typically of a specified pore size. TSS of a water sample is determined by pouring a measured volume of water through a pre-weighed filter of a specified pore size, then weighing the filter again after drying to remove all water. The gain in weight is a dry weight measure of the particulates present in the water sample expressed in mg/L calculated from the volume of water filtered.

BEAKERS & ERLENMEYER FLASKS

Used for digestions. NOT for standard preparation or anything requiring volumetric measurements.

WATER-SATURATED AIR (WSA)

WATER-SATURATED AIR (WSA) • Place the probe in a BOD bottle containing about 1 inch of water. • Shake BOD bottle prior to inserting probe to assure saturation. We recommend turning the stirrer OFF to avoid heating the thermistor during calibration. • The probe may need to sit in the bottle for 30-35 minutes in order to match the temperature of the air. • Determine barometric pressure from the on-board barometer if so equipped. • Check the temperature of the air (in the bottle) to be sure the probe thermistor is working correctly. This is also determined using the thermometer on-board the DO meter. • Use the meter's auto-calibration function to calibrate the probe and meter. • The WSA and auto-calibration function on modern DO meters is the most common DO calibration technique used by wastewater laboratories.

BOD samples that require additional nutrients.

When larger sample volumes are used to prepare BOD dilutions (> 200 mL), it will be necessary to add extra nutrients. Additional nutrients are required to ensure sufficient nutrients are available for bacterial growth and to stabilize pH. Use the following guidance to determine the amount of supplemental nutrients to add:

Certified weights

are used to verify the calibration status of laboratory balances. These weights must be certified to be ASTM Type 1 (formerly Class "S") specifications. Type 1 weights are made from high grade stainless steel. Type 2 (formerly Class "P") are typically made of brass. Type 2 (non-stainless steel) weights should not be used for analytical balance calibration verification, as brass is a soft metal alloy that is subject to oxidative pitting, tarnishing, and scratching. These conditions will result in significant changes to the standard's certified weight

Grab samples are used for determining...

instantaneous values and to identify extreme conditions. Municipal wastewater tests requiring grab samples include: pH, chlorine residual, dissolved oxygen, and, fecal coliform bacteria. Other tests (for industrial wastewater or under toxics regulations) requiring grab samples are: oil and grease, volatile organics, and cyanide.

Molarity

moles of solute/liters of solution

The importance of pH in process control.

pH of the biological mass in treatment facilities must be monitored to determine if the levels are too acidic or caustic for the microbes in the plant or the receiving water. Most wastewater plants in Wisconsin have an effluent discharge limit of 6.0 to 9.0 standard units (s.u.) in their permit, but pH levels of 6.8 to 7.2 are optimum for biological activity of most aerobic organisms. Laboratories may use bench-top pH meters for the analysis, using two or more calibration pH buffers that bracket the pH levels measured. The pH meter should be calibrated daily using fresh buffers. So, if samples are expected to pH values between 7.0 and 7.5, calibration of the pH meter should be performed using buffers of pH 7 and pH 10

Preferred reagent used to prepare standards in the DPD (colorimetric) determination of total residual chlorine.

potassium permanganate (KMnO4) solution is used as a chlorine equivalent. A solution containing 0.891 g/L of potassium permanganate has a chlorine equivalent of 1000 mg/L. Permanganate standards have a bright pink-red color.

When using flow proportional composite sampling...

the automatic sampler pulls an aliquot of sample from the flow stream directly proportional to the flow rate. Plant flow meters send an electronic "pulse" to the sampler to indicate a set amount of flow, such as a pulse for every 1,000 gallons. Then the sampler is programmed to pull a set amount of sample at a certain flow pulse interval such as 100 mL every 10 pulses or every 10,000 gallons

Flow proportional compositing is..

the most representative way to sample and is required by the Wisconsin DNR. Composite samples are generally appropriate for the calculation of loading rates. Normally, in municipal wastewater, the tests in this category include BOD, suspended solids, phosphorus, and ammonia

volumetric pipet (micro-bore)

used for standard preparation

Collect grab samples and locate the inlet tube for a composite sampler

• In a well-mixed area • In the center of the waste stream (away from channel sides) • Off of the floor of the flume/channel

For each sample or sample container the following information must be recorded:

• The sample type (flow proportional composite, time proportional composite, grab, etc) • The sample point (where taken) • Unique sample identification • The time and date of the sampling (grab) -or- time and date of the first and last subsamples for a composite sample • Any preservation during sampling - chemical added, refrigerated, etc. • The initials of person sampling It is also recommended that the operator record sample description (color, odor, turbidity, or other unusual observations). The information recorded on sample containers must be sufficient to trace it back to the sampling information.