APPENDIX A

LABORATORY EXERCISES

 

 

A. GUIDELINES FOR THE PREPARATION OF LABORATORY REPORTS

 

               I would like to see the reports resemble an engineering report or a small-scale version of a thesis.  You should concern yourself mostly with the Analytical Theory, Data Analysis and Discussion sections.  Please prepare one lab report per group.  What follows is the recommended format:

 

               ABSTRACT

This should be a short summary of the objectives, methodology used, results obtained, and the interpretation of those results.  It should give the reader a clear view of the scope of your work, as well as an understanding of the final results or conclusions.  The abstract should be no longer that 1 page.

 

               OBJECTIVES

What is the reason for making the types of measurements, or conducting the types of process test that you propose to do?  Half a page is usually more than enough.

 

               BACKGROUND or INTRODUCTION

This should include some background information on the environmental significance of the processes or phenomena being studied (e.g., coagulation, softening, use of TSS and VSS in assessing WWTP performance).  In particular, you should explain why the analytical data are needed and/or how they are used.  Data manipulation may be discussed in a general way.  Important mathematical relationships and models may be presented if they are relevant to the exercise.  Do not take passages from this set of course notes (i.e., Analytical Chemistry for Environmental Engineers) and reproduce them verbatim.  Instead, I want you to summarize or synthesize the various references at your disposal and present them here in your own words.  This type of an introduction is what one usually prepares for a formal engineering report submitted to a client.  Generally speaking you should be able to condense the necessary material into less than 3 pages, double-spaced.

 

               ANALYTICAL THEORY

Here is where you should present the underlying chemistry or physics of the analytical methods used.  With nearly each new lab you will be using new types of analytical equipment (e.g. analytical balances, pH meters, electrodes, turbidimeters, spectrophotometers, TOC analyzers, etc.).  As you use each of these for the first time, you should discuss their operating principles and theory in some detail.  As stated above (in paragraph on Background or Introduction), do not simply reproduce passages from the course notes for this section.  You need to synthesize, summarize and use your own words.  Such a discussion on analytical theory is not usually included in engineering reports; however, it is required here for pedagogical reasons.  This section will generally be one of the three longest (along with “Results” and “Discussion”) in the CEE 572 lab write-ups.

 

               SPECIFIC PROCEDURES or MATERIALS & METHODS

Do not list the analytical procedures or steps followed in lab, instead you should refer the reader to appropriate sections in the class notes or to Standard Methods for details.  Any significant modifications of the referenced procedures should be noted, however.  When using instruments, record the type, manufacturer and model number.  It is also useful to attach a photocopy of the methods used (either from the class notes or a reference book) as an appendix to the lab write-up.  This section will generally be no more than ½ to 1 page.

 

               RESULTS and DATA ANALYSIS

Results for each group will be compiled by the respective group captains.  A designated lab assistant (chosen from among the group captains) will then collect raw data from all groups, summarize it in a clear and logical fashion (often a series of tables is best), make copies of the summary, and distribute one to each student.  Each person should include this summary in the lab handout.  With some labs there will be group-specific data that are not shared with the entire class.  These data should also be presented in an efficient and logical manner.  Data tables are often the best choice.  Make sure that you present the final set of results in as concise a tabular or graphical form as possible.  While you may wish to present final concentrations in a table with raw data or intermediate calculations, you must always present the final data in a separate table that is easy for the casual reader to spot.  Often this is placed first in the results section.  A small amount of text must accompany the presentation of all results to aid the reader.  You should never have a table or figure that is not cited by number in the text.  Calculations and data manipulations should be included in this section.  These should follow the presentation of raw data.  Respond here to any requests at the end of the lab description for data manipulation.  Always show at least one full example for each type of calculation performed.  If you wish to show calculations for all samples, place this in an appendix.  You still, however, need to show one set of example calculations in the "Results" section.  If you have more than one determination of an analyte from any single sample (i.e., a replicate, either with or between groups), you should address the uncertainty of this (these) replicates.  This may involve (gasp) some form of statistics.

 

               DISCUSSION

This section should be prepared in the form of an engineering or commercial laboratory report to a client.  In most cases you will want to open with a paragraph on the specific samples collected and analyzed.  This may include reference to any process tests used (e.g., coagulation, softening).  You may then want to continue by referring to the final table(s) of data.  At this point, you should explain the significance of the results within the environmental engineering context of this lab (e.g., solids balance, suitability as a drinking water, doses required for optimal treatment).  With some labs you will be able to check your results based on the known composition of your samples.  This may involve some theoretical calculations.  Finally, you should compare your results whenever possible with values expected for similar types of samples or with environmental standards set by health or regulatory agencies for such samples.  Explain the significance of these comparisons.

 

In addition to the conventional discussion of lab results (above), you need to discuss certain issues that are germane to CEE 572, but would not usually be presented in an engineering or commercial laboratory report.  These include, but are not limited to explanations of possible sources of error.  Be careful not to over-emphasize analytical inaccuracies, failures, or unexpected results.  These are to be expected whenever performing an experiment for the first time.  Just do your best to explain how any obvious errors could arise.  Also in this section, you should address each of those questions appearing at the end of the lab description that pertain to errors, methodology and other issues not already covered in the previous sections.  You should make it clear when you are addressing a question (i.e., number the paragraphs according to the question numbers).  Other thoughts you have regarding this lab may also be included here. 

 

               CONCLUSIONS

Do your best to summarize the relevant findings and state the certainty with which you hold these findings.  You should not present any new thoughts here, nor should you use this section to further your discussion.  This should be just a distillation of the conclusion-type statements that you had already made in the discussion section (1/2 page max.).  Avoid making general pronouncements on the overall success of the lab (.e.g., “this lab worked well”).  Such statements are too vague to be of any use.

 

 

               REFERENCES

List any cited literature in this section.  Give the full citation in the references section.  Use some type of abbreviated citation at the point in the text where you wish the reference to appear.  The preferred in-text citation is the “author, date” format.  In this case you place the authors last names before a comma and the year of publication (e.g., (Switzenbaum & Hickey, 1993)).  When there are more than two authors, you list only the first author’s name and “et al.” For the others (e.g., (Switzenbaum et al., 1995)).  If there is more than one reference with the same authors and date, you should use a lower case letter after the year to distinguish them (e.g., (Tobiason & Edzwald, 1998a)).  The full citations (Journal or Book titles, volume #, issue #, page numbers, etc.) then appear in alphabetical order by authors’ last names in the References section.

 

               APPENDIX

                           Include here all of your raw data (photocopies are OK), and a photocopy of the detailed procedures.  You may also include photocopies of relevant pictures or graphs from the available literature.  However, there is no need to reproduce verbatim or photocopy passages from the course text or class notes.

 

 

Due Dates:

                           Lab reports will be due one week after the end of the lab.   Most of the labs will probably be stretched out over several days to a week or more.  In these cases, final lab reports will not be due until one week after the last day of the data collection period.

 

 

 

B. LABORATORY ORGANIZATION AND STUDENT OBLIGATIONS

 

               All students participating in a laboratory exercise must do the following:

 

1. Read and understand the lab procedure before the lab period.  Without this type of preparation, lab periods can become unnecessarily long as you struggle to learn the lab just as you are doing it.  This is not fair to the other students.  Furthermore, errors are more likely, and experiments may have to be repeated.  To help encourage students to prepare for labs, a few labs will be preceded by a “surprise” 5-minute quizz on the lab procedures for that period.

 

2. Be an active and helpful participant in your group’s work.

 

               Students will be assigned to groups with one member serving as "group captain".  This is a rotating position and one that requires some advance planning.  The "group captain" is responsible for:

 

1. Taking special care to review the lab procedure prior to the lab period, and discussing any uncertainties with the TA or instructor.

 

2. Dividing up the tasks among the group members, and directing the successful completion of these tasks.

 

3. Preparation of data blanks prior to the lab period, and assembling of data for his/her group during the lab (these data are then to be passed on to the "lab manager").

 

4. Cleaning glassware and returning materials used by the group after completion of the lab (under the direction of the TA).

 

 

               For each laboratory, one of the "group captains will be designated as the "laboratory manager".  This person will have the following additional duties:

 

5. Assist the TA in preparation for the laboratory exercise.  This may involve several hours of work during the week preceeding the lab period.

 

6. Collect data from all "group captains", and present it in a clear and logical fashion.  In order to avoid re-copying all of the data, the "laboratory manager" may prefer to provide each "group captain" with a standard blank data form.

 

 

C. GENERAL NOTES ON PRESENTATION OF SCIENTIFIC STUDIES

 

1. Scientific Writing

 

               Organize you paragraphs or sections in a logical fashion.  It is sometimes helpful to insert short heading for each paragraph as a means of focusing one’s thoughts.  These headings can be removed as a final step, just before submitting the lab report.  Think about the objective of each paragraph.  Compare what you have written with the paragraph-level heading.  Is there a consistent and coherent theme?  Be sure that the sentences in a given paragraph work toward achieving its objective.  Paragraphs containing fewer than 3 sentences generally represent incomplete thoughts.  They should either be developed more fully or merged with other paragraphs. Direct your writing to the level of a colleague familiar with environmental engineering, but not familiar with the specific technique or process you are discussing.  Be precise in your choice of words.  Be efficient in your writing, and don’t include extraneous material that is unnecessary for the intended purpose.  Be careful about making subjective statements or using ambiguous adjectives and adverbs (e.g., good, poor, fair, well).  Do not begin a sentence with a numeral or abbreviation.  If you must start a sentence with a number, spell it out (e.g., “Five milliliters were added to the ……”).

               Avoid using the active voice with an inanimate object as the subject.  For example, don’t write, pH electrodes monitored hydrogen ion activity.  In fact, pH electrodes cannot “do” anything by themselves.  You write, pH electrodes were used [by you] to monitor hydrogen ion activity.  This latter phrase uses the passive voice and has “you” as the implied subject.

 

 

 

2. Data Presentation

 

               Use graphs to present data, unless the precise values of the data are important.  In general, data from which graphs are prepared need not be presented.  However, to facilitate grading of these laboratory exercises, you should include all data in a series of tables.

               Standard, "xy" graphs should be used whenever possible.  The choice of linear, semi-log or full-log will depend on the nature of the data.  If prepared by hand, use graph paper, not engineering paper.  All linear graphs showing concentrations or doses should start at zero in both "x" and "y".  Do not succumb to the temptation of spreading out the data across an entire page, and in doing so set the origin by the lowest concentration or dose (although some graphics software will "want" you to do it this way).  You may connect individual points in an “xy” graph in order to help the reader see data trends.  You may also draw straight lines through the data, if you have reason to believe that variability in “y” is some simple function of “x”.  However, you should not draw smooth curved lines through all data points, nor should you allow your graphics software to do this.  The plotting of curve fits (e.g., cubic splines) implies that you have some special knowledge of the underlying relationship between “x” and “y”, and that your curve displays this relationship.  If one of the variables or treatments is not a continuous numerical variable or if in some other way does not lend itself to numerical representation (e.g., a sampling location in a treatment plant), you may use a bar graph to present the data.  Be sure to include all important conditions in the legend or on the face of the graph.  Also, remember that the independent variable is usually plotted on the x-axis, and the dependent variable falls on the y-axis.

               Be certain that graphics can be fully understood by the reader.  For example, graphs with multiple lines need to be designed in a way that the meaning of each line is clear.  Often this is done though the use of arrows and captions or unique line styles (e.g., dotted, dashed, colors) and a legend.  It is not permissible to blame your graphics software/printer if your graphics are ambiguous.  Even the most uncooperative computer can be simply turned off in favor of graph paper, a pencil and a ruler.  You should also number all figures and tables so that they can be cited unambiguously in the text.

               The number of significant figures displayed should always reflect the appropriate level of uncertainty.  For example, you should not increase the number of significant figures when you take a raw laboratory measurement and subject it to some form of mathematical data manipulation.  On possible exception to this rule is generally-accepted practice of retaining one or more extra figures during intermediate calculations.  These must be dropped when presenting the final answer.

 


D. LABORATORY PROCEDURES

 

Laboratory #1a

PREPARATION OF STANDARD SOLUTIONS

 

 

REFERENCES[1]

 

Sawyer & McCarty:    

3rd ed.

pp. 279 to 290.

 

Sawyer, McCarty & Parkin

4th ed

pp. 449 to 457

 

Sawyer, McCarty & Parkin

5th ed

pp. 528 to 535

 

Standard Methods:

  (14th ed)

pp. 4 to 9.

 

 

  (16th ed)

pp. 3 to 7.

 

 

  (17th –20th ed)

sect 1070, 1080 and 1090

 

EXPERIMENTAL PLAN

 

               Basic laboratory glassware and apparatus will be introduced and their proper use will be demonstrated.  Students will then be asked to prepare standard solutions of two inorganic salts.

 

 

PROCEDURES

 

1. Labware demonstration and discussion.

 

2. Prepare the following standard solutions.  Suggested volumes are 1 L for #1, and 100 mL for #2-4.

              (remember to save all calculations and make a record of all steps that are performed)

A. Potassium Chloride Standards (for Conductivity Lab)

1. 0.040 N KCl

                           2. 0.010 N KCl

                           3. 0.002 N KCl

                           4. 0.0008 N KCl

               B. Calcium Chloride Standard Solutions

1. 0.040 N CaCl2

                           2. 0.010 N CaCl2

                           3. 0.002 N CaCl2

                           4. 0.0008 N CaCl2

 


APPARATUS

 

               A. One set for each Group

1. One 1-liter volumetric flask

2. Three 100 ml volumetric flasks

                           3. An assortment of pipets (2mL, 5mL, 25mL)

                           4. Weighing paper

                           5. Forceps

                           6. Wash Bottle

                           7. Eight Reagent Bottles

                           8. One Funnel

                           9. One Pipet Holder

 

               B. One set for entire Class

                           1. Analytical Balance

                           2. Two Stainless Steel Spatulas

                           3. Potassium Chloride

                           4. Calcium Chloride (Dihydrate)

                           5. Distilled Water

 

 

LAB REPORT

 

               Lab Report not required.  Instead, you should include any notes and calculations used for the preparation of standard solutions in your lab report for lab #1b (Solids & Conductivity).

 

 


Laboratory #1b

SOLIDS & CONDUCTIVITY

 

 

PURPOSE

               To gain an understanding of the methods used to measure Total Solids (Total Residue), Total Dissolved Solids (TDS or Total Filtrable Residue), Suspended Solids (TSS or Total Nonfiltrable Residue), Volatile Suspended Solids (VSS or Volatile Nonfiltrable Residue) and Conductivity.  Also, to understand how these parameters are used in Environmental Engineering, and to understand the fundamental principles involved in the conductivity determination.

 

GENERAL REFERENCES

 

Sawyer & McCarty:    

3rd ed.

pp. 65-69, 284-285, 454-462.

 

Sawyer, McCarty & Parkin

4th ed

pp. 73-77, 379-380, 567-575.

 

Sawyer, McCarty & Parkin

5th ed

pp. 76-80, 457-458, 649-657

 

Snoeyink & Jenkins

 

pp. 74-82.

 

Standard Methods:

  (14th ed)

pp. 34-36, 71-75, 89-98.

 

 

  (15th ed)

pp. 30-32, 70-73, 90-98.

 

 

  (16th ed)

pp. 32-34, 76-80, 92-100.

 

 

  (17th –20th ed)

sect 1030F, 2510 and 2540

 

Rubinson

 

pp. 178-179, 243-245.

 

Hem, J.D.,

 

Chapt. 4 in Water Analysis, Volume 1, Minear & Keith eds

 

EXPERIMENTAL PLAN

               Appropriate solids analyses will be conducted on a variety of samples commonly encountered in environmental engineering.  These results will be compared to typical values reported in the literature. The conductivity of a drinking water, a brackish water, and one surface water will be measured as an alternative means of estimating the total dissolved solids concentration.  Finally the effect of concentration on the equivalent conductance of KCl and CaCl2 will be investigated.  In the interest of saving time, the iterative procedure for reaching a constant weight as discussed in Chapter XV will not be used with this laboratory exercise.  Instead, the samples will only be cooled and weighed once.

 

 

PROCEDURES

A. Preparation for Total Solids and Total Dissolved Solids (Filtrable Solids) Determinations on Clean Water Samples (River Water, Brackish Water and Drinking Water).

1. Clean a glass fiber filter by passing 200 mL of distilled water through it. Empty the rinse water.

2. Pour about 100 mL of your sample (see below) into the filtration reservoir while applying a vacuum.  Label (with a pencil on the etched circle) and weigh one of the pre-dried evaporating dishes. Using a 100 mL graduated cylinder, place precisely 50 mL of the filtrate into this vessel and transfer to the 180°C oven for 1 hour or until dry whichever is longer (Note: the standard procedure is to use a steam bath, but this is not practical in Marston 24).

3. Measure 50 ml of your sample (un-filtered), tare another pre-dried evaporating dish, add the sample and transfer to 180°C oven.

 

 

Group #

Samples

 

 1 & 2

   D

 

 3 & 4

   F

 

     5

   E

 

B. Preparation for Wastewater Total Suspended Solids and Volatile Suspended Solids Determinations.

1. Remove 2 pre-dried filters and aluminum pans from the desiccator, label the pans by etching a number in the aluminum lip (don't use a paper label), weigh each filter and pan together as a unit

2. Using forceps, place one of the filters in the filtration apparatus, measure out the requisite volume of your sample (see below), and pour this slowly into the filtration reservoir while applying a vacuum.  If the filter begins to clog, stop adding sample to the filtration reservoir, record the remaining sample volume in the graduated cylinder, and wait for the excess sample in the reservoir to pass through the filter.  Otherwise, filter the entire volume of sample.  Rinse down the sides of the reservoir with a few mLs of distilled water. Remove the filter, place it in the aluminum pan, and introduce the pan into the 103°C oven for a 1 hour drying period

 

 

Group #

Sample

Volume

 

 1 & 2

   A

 1000 mL

 

 3 & 4

   B

    20 mL

 

     5

   C

      5 mL (use only a single 5-mL distilled water rinse)

               C. Conductivity Measurements

1. Following the directions on conductivity measurements in the lecture and course notes, determine the conductivity of the four KCl standards, the four CaCl2 standards,  and the samples used above in part "A".

 

               D. Determination of Wastewater Suspended Solids

1. Following one hour of drying remove all filters and pans from the 103oC oven and place in desiccator to cool.

2. Weigh each filter/pan unit after it has returned to room temperature (about 15 min).

                           3. Place each pan and filter in the 550oC furnace for 15 min.

4. Following the 15 min ignition period transfer each pan and filter to the desiccator.

5. Weigh each filter/pan unit after it has returned to room temperature (about 20 min).

               E. Determination of Clean Water Total Solids Contents

1. Remove evaporating dishes from the 180oC oven and place them in desiccator to cool (about 30 min).

                           2. Weigh each upon return to room temperature.

 

 

APPARATUS

 

               A. One set for each Group

1. Two or three (depending on # samples to be analyzeD) pre-dried glass fiber filters (prepared in advance by the TA according to the following procedure: wash each disk by filtering 200 mL of distilled water, transfer to an aluminum pan and dry at 103oC for 1 hour, transfer disc to 550oC furnace for 15 minutes, place in desiccator.)

2. Three pre-dried Vycor evaporating dishes (prepared in advance by the TA according to the following procedure: place the clean evaporating dishes in the 550oC oven for 1 hour, cool in drying oven (103oC) for 15-20 min and store in desiccator).

                           3. Filtration Apparatus consisting of:

                                       a. membrane filter holder

                                       b. sample funnel/reservoir

                                       c. two vacuum flasks with vacuum tubing

                                       d. vacuum pump

                           4. Forceps

                           5. One 1000 ml graduated cylinder

                           6. One 100 ml graduated cylinder

               B. One set for entire Class

                           1. Two 150 ml beakers

                           2. Drying Oven at 103oC

                           3. Drying Oven at 180oC

                           4. Muffle Furnace at 550oC

                           5. Desiccator

                           6. Analytical Balance

                           7. Conductivity Meter and Electrodes

                           8. Two magnetic stirrers with bars and magnetic retriever

                           9. One 25 mL graduated wide-mouth pipet for "B"

                           10. One 5 mL graduated wide-mouth pipet for "C"

                           11. Distilled water (~5 liters)

                           12. One set of four 100-mL beakers for holding conductivity samples.

 

REAGENTS      (prepared for Lab #1a)

A. Potassium Chloride Conductivity Standards

1. 0.040 N KCl

                           2. 0.010 N KCl

                           3. 0.002 N KCl

                           4. 0.0008 N KCl

               B. Calcium Chloride Standard Solutions

1. 0.040 N CaCl2

                           2. 0.010 N CaCl2

                           3. 0.002 N CaCl2

                           4. 0.0008 M CaCl2

 

SAMPLES

               Wastewater  (from Amherst WWTP)

                           A - Secondary Effluent (5 liters)

                           B - Activated Sludge Mixed Liquor (500 ml)

                           C - Waste Activated Sludge (Secondary Sludge) (500 ml)

               Clean Water

                           D - Connecticut River Water (5 liters)

                           E - Ocean Water (1 liter)

                           F - Amherst Drinking Water (2 liters)

 

LAB REPORT

                           Note: The lab manager will collect and distribute solids data from all groups.  These data should be summarized and presented in you lab reports.  For the measurement of conductivity, you need only present the data collected by your group.

 

1. Discuss the pro's and con's of drying residues to 103oC as opposed to 180oC.

2. What are the limitations of using a glass fiber filter to separate "dissolved" from "suspended" matter. Discuss the significance of operationally defined analytical parameters in general.

3. Tabulate the conductivity data for the KCl and CaCl2 standards.  Plot specific conductance vs concentration, then calculate the equivalent conductance of each CaCl2 solution and graph this as a function of the log equivalent concentration for the solutions.  Include the KCl data for purposes of comparison.  How would you interpret these curves?

4. Calculate the ratio of dissolved solids to conductivity for the clean water samples.  How does this ratio compare with what you would expect?  Is such a number useful?

5. Compare river, ocean and wastewater samples with expected (or historical) values.


Laboratory #2

ACID / BASE TITRATION

 

 

PURPOSE

               Primary: to gain a knowledge of the methods used to measure pH, acidity and alkalinity and to establish an understanding of the principles behind the measurements of acidity and alkalinity.   Secondary:  to gain an appreciation as to how such data can be used in environmental chemistry.

 

 

REFERENCES

 

Sawyer & McCarty:    

3rd ed.

pp. 24-29, 168-188, 343-376.

 

Sawyer, McCarty & Parkin

4th ed

 

 

Sawyer, McCarty & Parkin

5th ed

pp.

 

Snoeyink & Jenkins

 

pp. 86-145, 156-196.

 

Standard Methods:

  (14th ed)

pp. 4-9, 17-33, 273-282, 460-465.

 

 

  (15th ed)

pp. 3-7, 16-30, 249-257, 402-409.

 

 

  (16th ed)

pp. 3-7, 17-32, 265-273, 429-437.

 

 

  (17th –20th ed)

sect 1070 A, B, C, sect 1050, sect 1010, 1030, and 1030 A, B, C, and D, sect 2310 and 2320, and sect 4500-H+

 

Rubinson

 

pp. 34-38, 46-63, 87-89, 266-296, 369-379

 

 

EXPERIMENTAL PLAN

               Following standardization of the titrant, acid/base titrations will be conducted on several unknown solutions.  Data will be in the form of "volume of titrant vs pH" and pH will be determined both potentiometrically and colorimetrically.

 

 

PROCEDURES

A. Standardizations - Day 1

                           1. HCl standardization        (3 experiments)

                                       a.    tare a piece of weighing paper.

                                       b.    open the desiccator and place 1 scoop of Na2CO3 on the paper, close the desiccator and quickly re-weigh paper + primary standard (difference should be 0.1-0.2g).

 

c.    Gently pour Na2CO3 into a 250 ml erlenmeyer flask.  Using the distilled water wash bottle rinse the remaining powder into the flask. Fill the flask to approximately the 100 ml mark with distilled water, and add 5 drops of methyl orange indicator solution.

d.    Fill burette with HCl stock using 250 ml beaker for transfer and note starting point (you must first add ~100 ml of HCl stock to the transfer beaker and keep the solution covered with a watch glass during titrations).  Titrate, while stirring, until the indicator just changes from yellow to red and record the end point.  Flush contents down the sink and rinse the 250-ml flask and stirring bar several times with distilled water.

e. Repeat this procedure (steps a-d) until 3 titrations have been successfully completed. Rinse the burette and 250-ml beaker thoroughly with distilled water.

 

                           2. NaOH Standardization  (1 experiment)

 

                                       a.    tare a piece of weighing paper.

                                       b.    open the desiccator and place 1 scoop of Potassium Acid Phthalate (KHP) on the paper, close the desiccator and quickly re-weigh paper + primary standard (difference should be 0.1-0.2g).

 

c.    Gently pour KHP into the 250 ml erlenmeyer flask with stirring bar.  Using the distilled water wash bottle rinse the remaining KHP into the beaker. Fill the beaker to approximately the 100 ml mark with distilled water, and add 5 drops of phenolphthalein indicator solution.

 

d.    Fill burette with NaOH stock using 250 ml beaker and note starting point.  As before, you must first add ~50 ml of NaOH stock to the beaker and keep the solution covered with a watch glass during titrations.  Titrate, while stirring, until the indicator just changes from colorless to pink and record the end point.  Flush contents down the sink and rinse the flask and stirring bar several times with distilled water.

 

               B. Titration of Samples - Day 2

 

                           1. Standardize pH meter

 

                           2. Acid titrations (determination of Alkalinity)

a.    Prepare 0.010 M HCl titrant by adding            mls (using the 100-ml graduated cylinder) of the approx. 0.1 M HCl stock to a 1-liter volumetric flask and filling to the mark with distilled water.  Stopper and invert several times to assure adequate mixing.

b.    Place 50 mls of the solutions to be titrated in a 250-ml flask with stirring bar and pH probe.  Add 5 drops of phenolphthalein indicator solution and titrate with 0.010M HCl.  Keep soln. stirring and record the pH after each incremental addition of HCl.  Shoot for an increment that gives about 0.2 pH unit change.  Stop when the phenolphthalein becomes colorless and indicate this point (pH, titrant volume) on the data sheet.

c.    Add 5 drops of methyl orange indicator solution and continue titrating as above.  When the color turns from yellow to red, mark this point in the data, and continue titrating until pH 3.0 is reached.

d.    Repeat steps 2b & 2c with the next soln. to be acid titrated.

 

                           3. Base titrations (determination of Acidity)

a.    Re-standardize the pH meter

b.    Prepare 0.010M NaOH titrant from the                 M NaOH stock by pouring                  mls of stock into the 100-ml graduated cylinder and adding this to a 1-liter volumetric flask, then fill to the mark with distilled water, stopper and shake.

c.    Add 5 drops of methyl orange indicator solution and titrate (as in 2.b.) with the 0.010M NaOH until the color changes from red to yellow.  Mark this point in the data and continue titrating until pH 11 is reached.

d.    Repeat step 3c with the next solution to be base titrated.

 

APPARATUS

 

               A. One set for each Group

                           1. Day 1 only

                                       a. six pieces of waxed weighing paper

                           2. Both days

                                       a. 50-ml burette with stand

                                       b. magnetic stirrer with 1 bar

                                       c. one 250-ml erlenmeyer flask

                                       d. phenolphthalein soln. and dropper

                                       e. methyl orange soln. and dropper

                                       f. distilled water squeeze bottle

                                       g. 250-ml beaker with watch glass

                           3. Day 2 only

                                       a. pH meter and probe

                                       b. 1-liter volumetric flask

                                       c. 100-ml graduated cylinder

 

               B. One set for entire Class

                           1. Day 1 only

                                       a. analytical balance

                                       b. desiccator

                                       c. two chemical scoopers

                           2. Day 2 only

                                       a. pH 4.00, 7.00, and 10.00 standards

 

 

REAGENTS - prepared in advance by the TA

               A. Primary Standards (Na2CO3 & KHP)

dried at 110 degrees C overnight and allowed to cool in a desiccator charged with "Drierite".

               B. Stock Solutions

                           1. approx. 0.1M HCl stock

prepared by adding 18 mls of reagent-grade HCl (11.6 M) to a 2-liter volumetric flask and filling to the mark with distilled water.

                           2. approx. 0.1M NaOH stock

prepared by adding 11.5 mls of a commercial 50% NaOH solution (19.1 M) to a 2-liter volumetric flask and filling to the mark with distilled water.

               C. Solutions/Samples for analysis

                           1. for acid titration

                                       A - 0.00125 M Na2CO3 solution  (pH 11)

   Dissolve 0.1325 g anhydrous Na2CO3 (previously dried at 110 degrees C) in one liter distilled water, bring pH up to 11 with a small amount of 50% NaOH solution (record this volume; usually a few tenths of an mL).

                                       B - 0.005 M  NaOH solution

   Add the proper volume (probably something slightly less than 50 ml) of NaOH stock to 1 liter of distilled water.

                                       C - Marine Aquarium Water

                                       D - Amherst Tap Water

 

                           2. for Base Titration

                                       E - 0.005 M Acetic Acid Solution

   This is best prepared using a serial dilution.  Prepare a 0.500 M intermediate by diluting 28.7 ml of Glacial Acetic Acid (17.4 M) to one liter, then dilute 10 ml of this solution to 1 liter to obtain the final 0.005 M solution.

                                       F - Amherst Tap Water

 

LAB REPORT

 

               A. Following Day 1

  1.       Write a balanced equation for the neutralization of Na2CO3 by HCl; Potassium Acid Phthalate (KHP) by NaOH. Calculate and tabulate for each of the 4 standardizations: the number of moles of primary standard titrated; the volume of titrant required to reach the endpoint; and the exact molarity of the titrant.

              2.       Calculate a mean estimate of the molarity for the HCl titrant.  Determine a 95% confidence interval for this number.

 

 

 

               B. Following Day 2

  1.       Plot each set of titrant volume vs. pH data on graph paper.  pH should be on the y-axis, and mL acid or base on the x-axis (starting from 0 mL).

              2.       Calculate and summarize for each of the six solutions the mineral acidity and CO2 acidity or the hydroxide alkalinity, carbonate alkalinity and bicarbonate alkalinity, whichever being appropriate.

              3.       Do the indicators always change color at the same pH? Discuss the advantages and disadvantages of the two methods (colorimetric vs. potentiometric).

  4.       Which samples show clear inflection points at the mid-points of the titrations? Assuming these are solutions of pure compounds, can you estimate their pKa's? Do these suggest the identity of the unknown "pure compounds" (refer to handout on selected pKa values) ? How certain would you be of such an identification?

  5.       Suggest some sources of error in the determination of alkalinity and acidity.  Which of these do you consider most important and why?  Did you notice an unstable or drifting pH in between additions of titrant?  What do you think could be responsible for this phenomenon?

  6.       Discuss the significance of the alkalinities/acidities measured for samples C, D, and F.


Laboratory #3

SOFTENING

 

 

PURPOSE

               To become familiar with the EDTA titrimetric methods for the analysis of Total Hardness and Calcium, and to gain a better understanding of the chemical thermodynamic and kinetic principles of precipitative water softening.

 

REFERENCES

 

Sawyer & McCarty:    

3rd ed.

pp. 191-205, 309-313, 377-384, 514-519.

 

Sawyer, McCarty & Parkin

4th ed

pp.154-168, 404-409, 485-492, 633-638.

 

Sawyer, McCarty & Parkin

5th ed

pp.

 

Snoeyink & Jenkins

 

pp. 287-298

 

Standard Methods:

(14th ed)

pp. 185-190, 200-206.

 

 

(15th ed)

pp. 182-186, 194-199.

 

 

(16th ed)

pp. 196-200, 209-214.

 

 

(17th –20th ed)

Sect. 2330, 2340

 

Rubinson

 

pp. 315-322.

 

 

EXPERIMENTAL PLAN

               A synthetic hard water will be subjected to lime and lime-soda softening.  Treated water quality will be evaluated via the EDTA titrimetric methods for Total Hardness and Calcium, the potentiometric method for Alkalinity and Conductivity.  The results will be compared to those expected based on chemical equilibria.

 

PROCEDURES

I. First Day

               A. Precipitative Softening of Synthetic Water (if 600 mL beakers are to be used, reduce the volumes accordingly)

1. Pour 500 mL of synthetic water into each of six 600-mL beakers. Place these beakers under the jar test machine.

2. Add lime suspension (Calcium hydroxide) and soda ash (sodium carbonate) according to the following program:

 

Beaker #

Lime (mL)

Soda Ash (mL)

1

1.5

0

2

2.5

0

3

3.7

0

4

5

0

5

3.7

2.7

6

5

4.0

 

                           3. Stir at 30 rpm for 20 min, allow samples to settle for 5 min.

4. Filter 300-400 mL of the supernatant and analyze each of these six filtrates plus the raw synthetic water and Amherst tap water for pH, alkalinity, hardness, and calcium.  Each group will be assigned two samples according to the following program:

 

5 Groups/class

3 Groups/class

Group #

Samples

Group #

Samples

1

#1 & #6

1

#1, #6 & Raw Syn. Water

2

#2 & Raw Syn. Water

2

#2, #5 & Raw Syn. Water

3

#3 & Amherst Tap

3

#3, #4 & Raw Syn. Water

4

#4 & Amherst Tap

 

 

5

#5 & Raw Syn. Water

 

 

 

               B. pH and Alkalinity Determinations

                           1. Standardize pH meter with pH 7 & 4 buffers.

                           2. Pour 100 mL sample into a 250 mL beaker and measure initial pH.

3. Titrate with 0.01 M HCl to an endpoint of pH 4.5 and record titrant volume.  Record titrant volume at the equivalence point of pH 8.3 as well, if the initial sample pH was above this value.

4. Repeat steps 2-3 until all samples have been titrated.

 

II. Second Day

Analyses for Day #2 will be divided up according to the following program:

 

5 Groups/class

3 Groups/class

Group #

Samples

Group #

Samples

1

#1 & #6

1

#1, #6 & Raw Syn. Water

2

#2 & Raw Syn. Water

2

#2, #5 & Distilled Water

3

#3 & Amherst Tap

3

#3, #4 & Ca Std.

4

#4 & Distilled Water

 

 

5

#5 & Ca Std.

 

 

 

               C. Total Hardness Determination

1. Place exactly 50 mL of the sample into a 125-mL erlenmeyer flask.

                           2. Add 1-2 ml of the buffer solution

                           3. Add 5-6 drops of the EBT indicator.

4. Titrate with the EDTA solution until all reddish coloration disappears and only dark blue remains.  Maintain constant stirring during this operation.  For best results the titration should be completed within 5 minutes.

5. Repeat steps 1-4 until all of the requisite samples have been titrated.

 

               D. Calcium Determination

1. Place exactly 50 mL of the sample into a 125-mL erlenmeyer flask.

2. Add 3 mL of NaOH solution.  If the pH is still below 12, add more base.

                           3. Add 1 scoop of Eriochrome Blue Black R indicator (0.1-0.2 g)

4. Titrate with the EDTA solution until the color changes completely from red to royal blue.  Maintain continuous stirring throughout.

5. Repeat steps 1-4 until all of the requisite samples have been titrated.

 

               E. Conductivity Determination

                           1. Prepare the conductivity meter.

2. Place approximately 75 mL of solution into a 150-mL beaker with stirring bar. Turn on magnetic stirrer.

                           3. Insert probe and record conductivity reading.

4. Repeat steps 2-3 until all of the requisite samples have been analyzed (distilled water samples need not be analyzed).

 

APPARATUS

               A. One set for entire Class

                           1. One jar test apparatus.

                           2. Six large beakers (600 mL).

                           3. Three 50-mL burettes, burette stands and clamps.

                           4. Three magnetic stirrers and bars.

                           5. Two 10-ml graduated pipettes and bulbs.

                           6. One pH meter with pH standards (7 & 10).

                           7. One Conductivity Meter and Probe.

                           8. Two filtration set-ups (filter flasks, pumps, etc.)

               B. One set for each Group

                           1. Titration setup (buret, clamp, magnet stirrer)

                           2. Three 1-L glass bottles (for storing samples).

 

 

REAGENTS - Prepared in advance by the TA.

               A. Softening and Alkalinity Determination

1.  Synthetic Water: 4 mM Na+, 3 mM Ca+2, 1 mM Mg+2, 4 mM CT, 6 mM Cl-, 1 mM SO4-2.

                              To 10 liters of distilled water add the following:

                                       a. 3.33 g anhydrous CaCl2  (3 mM)

                                       b. 1.204 g MgSO4  or  2.456 g MgSO4.7H2O   (1 mM)

                                       c. 3.36 g NaHCO3   (4 mM)

2. Lime Solution (0.5 M) - Add 28.0 g CaO to 1-liter of distilled water and stir continuously.

3. Soda Ash Solution (0.5 M) - Add 53.0 g Na2CO3 to distilled water and dilute to one liter.

4. HCl Titrant (0.01 M) - Left-over titrant from the Acid/Base lab.  If more titrant is needed, add 0.88 mL reagent grade HCl (11.6 M) to a 1-liter volumetric flask and dilute to the "mark" with distilled water and standardize.

               B. Hardness and Calcium Determination

1. Buffer Solution - Dissolve 16.9 g ammonium chloride in 143 mL conc ammonium hydroxide. <caution: avoid inhalation of fumes!>  Add 1.25 g Mg-EDTA and dilute to 250 ml with distilled water.  If Mg-EDTA isn’t available, use Na-EDTA and MgSO4 or MgCl2 as directed in method 2340C of Standard Methods.

2. Hardness Indicator Solution - Dissolve 0.5 g of Eriochrome Black T (1-(1-hydroxy-2-naphthylazo)-5-nitro-2-naphthol-4-sulfonic acid) in 100 g triethanolamine (2,2',2''-nitrilotriethanol).

3. EDTA Titrant Solution (approx. 0.01M)  - dissolve 3.723 g Na-EDTA (sodium ethylenediaminetetraacetate dihydrate) in 1000 ml distilled water.

4. Standard Calcium Solution (5.00 mM) - Weigh 0.5005 g anhydrous calcium carbonate (primary standard grade) and place in a 500-ml erlenmeyer flask.  Carefully add small amounts of 6 M HCl (approx 50% of conc.) until CaCO3 just dissolves.  Add 200 ml distilled water and boil for a few minutes to expel dissolved CO2.  Cool, add a few drops of methyl red indicator and adjust to the "intermediate" orange color by adding 3N NH4OH or 6M HCl as needed.  Transfer quantitatively to a 1-liter volumetric flask and dilute to the "mark" with distilled water.

5. Sodium Hydroxide Solution (1N) - Dilute 40 g NaOH to 1 liter with distilled water.

6. Eriochrome Blue Black R indicator (or Palatine Chrome Black GBN) - Grind together in a mortar 200 mg powdered dye and 100 g solid NaCl to about 40-50 mesh.  Store in a tightly stoppered bottle.

 

LAB REPORT

1. Tabulate the concentrations of Alktot, AlkCO3, AlkHCO3, CT, Ca, Hardness, and Conductivity for all seven unknowns.  Hardness and Ca concentrations are based on a 2-point standard "curve" comprised of the mLs of EDTA for the distilled water (0 mM) and for the Calcium Standard (5 mM).

2. Plot CT, Ca, Mg (Hardness-Ca), and pH as a function of lime dose both with and without soda ash.  Try to show data for all samples on the same graph so they can be directly compared.

3. Using your results for the alkalinity, Ca, and hardness, of the raw synthetic water, estimate the necessary doses of lime and soda ash for complete softening.  Assume that the difference between the Ca and hardness concentrations is due solely to Mg.  Assume, also, that all of the alkalinity is due to carbonate, bicarbonate, and hydroxide.

4. Discuss the significance of your results in light of the above calculations. Were the removals of Ca, Mg, and alkalinity observed in each of the six treated samples as great as expected?  If not, why?

5. Calculate the Langelier Index for samples 3 and 4. How many millimoles per liter of H2SO4 or NaOH would you add to each to produce a water with an optimum LI?


 

Laboratory #4

NITRIFICATION

 

 

PURPOSE

               To become familiar with the procedures and chemical bases for the analysis of NH3-N (ammonia nitrogen), NO2-N (nitrite-nitrogen) and NO3-N (nitrate-nitrogen).  Also, to gain some experience in the collection and analysis of surface water quality data.

 

REFERENCES

 

Sawyer & McCarty:    

3rd ed.

pp. 14-20, 205-211, 295-302, 304-309, 313-314, 439-453.

 

Sawyer, McCarty & Parkin

4th ed

pp. 18-23, 168-175, 389-397, 399-404, 409-410, 552-565

 

Sawyer, McCarty & Parkin

5th ed

pp.

 

Snoeyink & Jenkins

 

 

 

Standard Methods:

(14th ed)

pp. 406-410, 416-417, Nitrite section.

 

 

(15th ed)

pp. 373-375, 382-383, 404-406

 

 

(16th ed)

 

 

 

(17th –20th ed)

sect 4500-N, 4500-NH3 A, sect 4500-NH3 D, sect 4500-NO2- A and B

 

Rubinson

 

pp. 63-66, 304-311, 615-631

 

 

EXPERIMENTAL PLAN

               Samples will be collected from the biological reactor and analyzed for ammonia, nitrite, and nitrate.  These will provide a baseline measure of the degree of bacterial nitrification in this controlled treatment system.  We will also be measuring dissolved oxygen, during a later period.  Samples will be collected and analyzed over one aeration period (several days) to monitor the progress of nitrification.

 

PROCEDURES

 

I. Initial Analysis

               A. Collection of Representative Samples from the Biological Reactor.  Then each group should analyze the reactor contents for the three nitrogen species.  Analyze D.O. on a water blank.

 

               B. Ammonia-Nitrogen Determination  (Phenate Method)

1. To 25 mL of sample in a 100 mL beaker, add 1 mL of phenol solution, 1 mL of sodium nitroprusside solution, and 2.5 mL of oxidizing solution.  Mix thoroughly after each addition.

2. Cover samples with Parafilm, and allow color to develop for at least 1 hour.

3. After no more than 24 hours, measure absorbance at 640 nm.

4. Repeat steps 1-3 for all samples assigned to your group along with three standard solutions prepared from the ammonia stock solution.  Use Super-Q water from the research lab for preparing standards.  Do not use the distilled water for this purpose.  The "laboratory manager" should coordinate the concentrations chosen by each of the groups so that they are well spaced across the recommended range of 0-0.5 mg/L.  Dilute samples when necessary.

 

               C. Nitrite-nitrogen Determination (Colorimetric Method)

1. To 50 mL of sample in a 100 mL beaker, add 2 mL of the color reagent and mix..

2. Wait 10 min after addition of the reagents, then measure the absorbance at 543 nm.  If the absorbance is greater than that measured for the 0.025 mg/L standard, dilute the original sample and repeat steps 1-2.

3. Repeat steps 1-2 for all samples assigned to your group along with three standard solutions prepared from the 250 mg/L nitrite-N solution.  The "laboratory manager" should coordinate the concentrations chosen by each of the groups so that they are well spaced across the recommended range of 0-0.025 mg/L.

 

               D. Nitrate-nitrogen Determination (ion specific electrode)

1.      Prepare a set of standards from the nitrate stock that span the concentration range up to 30 mg/L as N.  You should have a blank as well as at least 4 nitrate-containing standards.  You only need about 50 mL of each.

2.      Mix equal volumes (about 1-2 mL each) of standard and interference suppressor solution.

3.      Agitate by hand or place solution on magnetic stirrer with micro-stir bar inside, and measure the potential (mV) with the nitrate electrode.

4.      Repeat steps 2 & 3 for all standards and samples

 

               E. Winkler Method for the Determination of Dissolved Oxygen

1. To a 300 ml BOD bottle filled with sample add 1 mL manganous sulfate solution and 1 ml alkali-iodide-azide reagent, cap and mix.

2. Allow precipitate to settle to about half the height of the bottle and add 1 mL conc. sulfuric acid. Re-stopper and mix.

3. Titrate 201 mL of this sample with the 0.0021M sodium thiosulfate solution until a very pale yellow color is obtained.  Add a few drops of the starch solution and titrate until the blue color disappears.

 

 

II. Subsequent Analyses

               A. Arrange to collect and analyze samples over the remainder of the nitrification period for all three nitrogen species.

               B. Arrange to collect and analyze a sample at the ned of the nitrification period for D.O..

 

 

 

APPARATUS

 

               A. One set for each Group

                           1. Two 100-mL beakers

                           2. One magetic stirrer and stirring bars

                           3. Pipets (1 mL and others)

                           4. Burette

               B. For the entire class

                           1. Spectrophotometer (Vis).

1.   One pair of spectrophotometric cells for visible wavelengths.

2.   One nitrate electrode and mV meter

3.   DO meter and electrode

 

REAGENTS

 

               A.  Ammonia-Nitrogen Analysis

1.  Alkaline citrate:  Dissolve 40 g trisodium citrate and 2 g sodium hydroxide in deionized water.  Dilute to 200 mL.

2.  Oxidizing solution:  Mix 100 mL of alkaline citrate solution with 25 mL of the commercial 5% NaOCl stock.  Prepare fresh daily

3.  Sodium Nitroprusside solution (0.5% w/v):  Dissolve 0.5 g sodium nitroprusside in 100 ml high-purity water.  Store in amber bottle for up to 1 month.

4.  Phenol solution:  Dissolve 11.1 mL liquefied phenol (³89%) with 95% v/v ethanol to a final volume of 100 mL.  (you may also weigh out 17 g of crystalline phenol in place of the 11.1 mL of liquefied material).

5.  Ammonia Standard (100 mg/L as N) Dissolve 381.9 mg anhydrous NH4Cl in 1 liter of distilled water.

 

               B.  Nitrite-Nitrogen Analysis

1.  Color Reagent:  Place about 800 mL of distilled water to a 1-liter volumetric flask.  To this slowly add 100 mL of 85% phosphoric acid and then 10 g sulfanilamide.  Once the sulfanilamide is completely dissolved, add 1 g N-(1-naphthyl)-ethylenediamine dihydrochloride and dissolve.  Dilute to 1 liter.  This reagent must be stored in a dark bottle in a refrigerator.  It can be used for 1 month.

2.  Nitrite Standard (250 mg/L as N) Dissolve 1.232 g NaNO2 in 1 liter of distilled water.  Add 1 mL chloroform as a preservative.

 

               C. Nitrate-Nitrogen Analysis

1.      Nitrate electrode and ISE meter

2.      Interference Suppressor Solution

3.      Nitrate stock solution

 

               D. Winkler Reagents

1. Manganous sulfate solution - Dissolve 400 g MnSO4.2H2O in distilled water and dilute to 1 liter.

2. Alkali-iodide-azide reagent - Dissolve 500 g NaOH and 150 g KI  in distilled water and dilute to 1 liter.  Add 10 g NaN3 dissolved in 40 ml distilled water.

                           3. Sulfuric acid concentrated

4.      Sodium Thiosulfate titrant - Dissolve 6.205 g Na2S2O3.5H2O in distilled water.  Add 0.4 g NaOH and dilute to 1 liter.  Standardize with the primary standard Potassium Dichromate solution using starch to define the endpoint.

5.      Starch solution

 

LAB REPORT

1. For each of the samples calculate and tabulate the concentrations of nitrogen species.

2. Plot these concentrations versus time.  What pattern (change in concentrations with time) did you expect to see?  What is happening with the nitrogen species?  Why is it happening?  What is the significance to the bacterial community?

3. How is this process (nitrification) used in wastewater treatment plants?  Discuss its general importance to natural aquatic systems.


Laboratory #5

COAGULATION

 

PURPOSE

     To become familiar with the principles and practice of turbidity, iron, aluminum, color, and UV absorbance measurements and to gain an understanding of the significance of these parameters.

     To obtain some experience in conducting jar tests and manipulating and interpreting data from such studies.

 

 

REFERENCES

 

Sawyer & McCarty:

3rd ed.

pp. 29-39, 295-302, 304-309, 313-314, 331-342, 464-469.

 

Sawyer, McCarty & Parkin

4th ed

pp. 33-44, 389-397, 399-404, 409-410, 439-448, 577-582.

 

Sawyer, McCarty & Parkin

5th ed

pp.

 

Snoeyink & Jenkins

 

pp. 243-270

 

 

(14th ed)

 

 

Standard Methods:

(15th ed)

pp. 131-134, 199-206.

 

 

(16th ed)

pp. 133-136, 214-220.

 

 

(17th –20th ed)

sect 2130; sect 3500-Fe

 

Rubinson

 

pp. 645-656.

 

Skoog & Leary

(4th ed)

Chapts. 5-8 and 12 (sect. C-3).

 

Hudson, H.E. Jr.

Water Clarification Processes, Van Nostrand Reinhold Co., 1981

Chapt. 3

 

Rainwater & Thatcher

1960, US Geological Survey, Water Supply Paper 1454

pp. 97-100 (Al method)

 

 

EXPERIMENTAL PLAN

     The alum coagulation of a synthetic natural water will be investigated via the jar test method with alum dose and pH being the independent variables.  The dependent variables of interest are residual turbidity, residual iron, residual coagulant (Al) and three measures of the residual organic matter (TOC, Color and UV absorbance).  The data will be compared using two-dimensional plots and three-dimensional response surfaces.

 

 

PROCEDURES

I. Jar Tests and the measurement of turbidity, color and UV abs. (Day 1)

               A. Jar Tests  (Hudson)

1. place 500 mL of the synthetic water into two sets of six 600-mL beakers each.  Set these beakers underneath the jar test paddles, lower the paddles and begin rotation at 60 rpm.

2. Add "x" mL of the stock H2SO4 to each beaker as indicated in the program below:

 

 

 

 

Series

 x

 

  A 

 0

 

  B 

10

 

3. Increase the stirring speed to 100 rpm and quickly add by pipette the following amounts of the alum stock:

 

 

Beaker #

   Alum Vol. (mL)

 

   1

         0  (control)

 

   2

         1

 

   3

         2

 

   4

         3

 

   5

         5

 

   6

        10

 

4. Reduce the speed to 20 rpm after 120 sec has passed since the last beaker was dosed with alum.  Maintain this slow mix for 20 min.

5. Remove the six beakers from the jar test machine.  Gently measure the (final) pH of each coagulated sample and place them on a bench free of vibrations for a settling period of 30 min.

6. Siphon 300 mL of each sample into a clean reagent bottle and label.  Pour 300 ml of the untreated synthetic water into a seventh bottle as a blank.  Measure settled water turbidity in accordance with "C".

               B. Sample Pretreatment

                           1. Prefiltration and pH adjustment

a. Place a Glass Fiber filter in the filtration apparatus and rinse with 100 mL distilled water.  Discard the wash water and filter the sample (be sure that the settled water turbidity has already been measured [part C], or a sample has been saved for this).

b. Measure filtered water turbidity (part C)

c. Set aside 100 mL of this filtered sample for measurement of color & UV abs.

d. Add 3 drops of Conc. HNO3 to the remaining 150-200 mL of sample and store at 2°C until "Day 2" for Fe and Al determination.

 

               C. Measurement of Settled Water Turbidity and Filtered Water Turbidity

1. Calibrate the turbidimeter: choose a standard that is within the range to be used (e.g., 100 for 0-100, 5 for 0-10, or 0.5 for 0-1), insert this tube into the meter, replace the cover, turn range select to the appropriate range, and adjust potentiometer to calibrate.

                           2. Measure sample turbidities

a. Fill a clean, unscratched sample tube to within one-half inch from the top with the water to be measured.  Allow sufficient time before measurement for air bubbles to rise up out of the eventual light path.  Do not touch the tube near its mid-point where the scattered light is measured.  Clean off any dust that may have settled on the outside of the tube with a piece of tissue paper.

b. Place the tube inside the turbidimeter in such a way that the orientation is always the same (e.g., you might want to make a small mark on the top rim and always orient this mark towards you as you insert the tube)

c. Read the turbidity making use of the mirror-backed scale.  If the sample turbidity is off-scale, or below 10% full scale, the turbidimeter must be re-calibrated in the appropriate range.

 

               D. Color and UV absorbance measurements (filtered samples)

   General Directions for the use of single-beam spectrophotometers:  Be careful not to touch the cell windows.  Be sure that cells are scrupulously clean and un-scratched.  Fill one cell with distilled water and the other with the sample, close the sample compartment and "zero" the instrument with the water-filled cell in the light path.  Then adjust the cell positioning knob such that the sample cell is in the light path and read the absorbance.

1. Color: place selector lever at "visible", set wavelength at 400 nm, verify that the filter lever is in the proper position for a wavelength of 400 nm, and use "vis" or ordinary glass cells.

2. UV Absorbance: place selector lever at "ultraviolet", set wavelength at 254 nm, adjust filter lever to the proper position for use at 254 nm, and use "UV"  quartz glass cells.

 

II. Measurement of Fe and Al (Day 2; use filtered, acidified samples from Day 1)

               A. Total Iron and Aluminum Determinations (Rainwater & Thatcher, 1960)

                           1. Preparation of standards:

a. Pipette into separate 50 ml volumetric flasks the following volumes of the 2.00 mg/L Fe and 10.00 mg/L Al standard solutions and fill to the "mark" with distilled water.

 

Volumes of Fe and Al standard solutions respectively (3 groups)

Group#

Std A

Std B

Std C

Std D

1

0 & 0

30 & 0

30 & 5

15 & 15

2

0 & 0

5 & 0

15 & 0

30 & 0

3

0 & 0

0 & 5

0 & 15

0 & 30

 

 

 

 

 

Volumes of Fe and Al standard solutions respectively (5 groups)

Group#

Std A

Std B

Std C

Std D

1

0 & 0

30 & 0

30 & 2

15 & 15

2

0 & 0

0 & 2

0 & 5

0 & 15

3

0 & 0

0 & 10

0 & 20

10 & 10

4

0 & 0

2 & 0

5 & 0

15 & 0

5

0 & 0

0 & 5

0 & 15

0 & 30

 

                           2. Preparation of samples

a. Remove the acidified samples from the refrigerator and shake to re-suspend any sediment.

                           3. Baseline absorbance

a. Measure absorbance of the filtered samples at 370nm and 520nm.

                           4. Analysis of samples/standards:

                                       a. Transfer 50.0 mL of sample/standard into a 100-mL beaker

b. Add 4.0 mL of hydroxylamine solution and let stand for 30 min.

                                       c. Add 10.0 mL of the ferron-phenanthroline solution and mix.

d. Add 4.0 mL of the sodium acetate solution and wait at least 10 min before measuring absorbance.

e. Set wavelength at 370 nm for Al and 520 nm for Fe and measure absorbance. Note that standards known not to contain one of these metals should nevertheless be analyzed at both wavelengths as these metals interfere with each other's determination.

f. Repeat steps a-e until all standards and samples have been analyzed.

 

III. Total Organic Carbon Analysis (Day 2)

1.      Analyze a set of 4 TOC standards (KHP) spanning the range from 0-10 mg/L

2.      Analyze the TOC from each of the coagulated and filtered samples.  Dilute where appropriate to stay within the calibration range

3.      Analyze the TOC from a sample of the raw water, both filtered and unfiltered.

 

 

APPARATUS

 

I.  Day 1 only

               A. One set for each Group

                           1. four 600 ml beakers

                           2. One 10 ml graduated pipette with pipetting bulb

                           3. four glass fiber filters

                           4. Pasteur pipette or dropper with bulb

                           5. pH Meter, pH probe and pH standards

                           6. One 250 ml beaker

                           7. Two 50 ml beakers

 

               B. One set for entire Class

                           1. Two jar test machines

                           2. One turbidimeter with standards and two sample cells

                           3. Two 500 ml graduated cylinders

                           4. Two siphons

                           5. Two sets of filtration apparatus

                           6. Approx. 4 liters distilled water for rinsing filters

 

II.  Both Days

               A. One set for each Group

                           1. Four reagent bottles

               B. One set for entire Class

1. UV/Vis Spectrophotometer with two 1-cm quartz cells and two 1-cm "vis" cells

                           2. Refrigerator space for sample storage between lab periods

 

III. Day 2 only

               A. One set for each Group

                           1. Five 100 ml beakers or erlenmeyer flasks

                           2. Four 50 ml volumetric flasks

 

REAGENTS - prepared in advance by TA

I.   Day 1 only

1. Synthetic Water (250 mg/L kaolin, 5mM HCO3, 5 mg/L TOC, 500 ug/L Fe) stirr upon initial mixing, and during sampling, but do not aerate  - prepare as follows:

                                       to 20 liters of distilled water add

                                                   1. 5 g kaolin

2. 1 liter of Aldrich Humic Acid solution prepared as follows:

             Dissolve 200 mg Aldrich Humic Acid in 1 liter distilled water, raise pH to 10 with 50% NaOH solution, allow this to dissolve for several hours (overnight?) while stirring, lower pH to 3 with conc. HCl, stir 1 hour , filter with glass fiber filter

                                                   3. 8.40 g anhydrous NaHCO3

4. 0.0272 g anhydrous FeSO4, added immediately prior to lab period.

                                       titrate with conc. HCl to pH 7.5-8.0

2. Alum Stock Solution - add 5.00 g aluminum sulfate (Al2(SO4)3.18H20) to 1 liter of distilled water.

                           3. NaOH stock solution for pH adjustment, approx. 0.2 M

                           4. H2SO4 stock solution for pH adjustment, approx. 0.1 M

III.Day 2 Only

               A. Al/Fe Analysis

1. Hydroxlyamine solution: Dissolve 50 g NH2OH.HCl in distilled water, add 20 ml conc. HCl and dilute to 500 ml.

2. Sodium Acetate solution: Dissolve 175 g anhydrous NaC2H3O2 in distilled water and dilute to 500 ml.

3. Ferron-phenanthroline solution: (1.43 mM and 5.55 mM, respectively) Dissolve 0.5 g ferron and 1.0 g 1,10-phenanthroline in 1000 ml of distilled water. If after 2 hours of stirring the reagents have still not completely dissolved, allow solution to settle and decant supernatant.

4. Fe stock solution, 200 mg/L: Slowly add 10 ml conc. H2SO4 to 25 ml distilled water and dissolve 0.702 g ferrous ammonium sulfate (Fe(NH4)2(SO4)2.6H2O). Add dropwise 0.1N KMnO4 until a slight pink color persists. Dilute to 500 ml with distilled water.

5. Fe standard solution, 2.00 mg/L: Dilute 10 ml of Fe stock solution to 1000 ml.

6. Al standard solution, 10.00 mg/L: Dilute 14.5 ml of Alum stock solution to 1000 ml.

 

B. TOC Analysis

1.      Potassium hydrogen phthalate (KHP) Standard as per Standard Methods: 5220 B. 3 g. : Lightly crush and then dry potassium hydrogen phthalate (HOOCC6H4COOK) to constant weight at 120'C.  Dissolve 425 mg in distilled water and dilute to 1000 mL.


LAB REPORT

 

A. Following Day 1

 

1. Tabulate the settled turbidity, filtered turbidity, color and UV absorbance data collected by your group.  Provide a copy of this to the lab manager.  The lab manager will compile all these data and distribute graphs of these four water quality parameters versus alum dose.  What does this show?  Do they show the same trends?

 

B. Following Day 2

 

2.      Tabulate your group's data (i.e., absorbance measurements) for the analysis of the Al and Fe standards and for the coagulated water samples.  The lab manager will collect these data and provide copies for everyone.  Using calibration (standard) data from samples containing only Fe or only Al, prepare a graph of absorbance at 370 nm vs. Fe conc. and absorbance at 370 nm vs. Al conc. Prepare a similar graph using the 520 nm data.  What does this tell you about interferences between the two metals in their respective analyses?

3.      Calculate the best-fit linear regression for Fe (in mg/L) vs abs at 520 nm and report the regression equation.  Include in this analysis all of the data from standards containing only Fe.  Using the 520 nm regression equation, estimate the Fe concentrations in the samples.  Then, make any necessary corrections for Fe interference in the 370 nm data, and estimate the Al concentrations also.

4.      Calculate standard deviations for the Fe concentrations determined in #3 above, based on uncertainty in the standard curve.  Do this only for the samples your group analyzed.

5.      Graph the Al and Fe data as a function of alum dose from both sets of jar tests.

6.      How much of the added aluminum remained after coagulation, settling and filtration?  Traditionally coagulation processes have been monitored and controlled using turbidity measurements.  Does adequate turbidity removal also insure adequate removal of organics? aluminum? iron?

7.      Compare the TOC values with the UV absorbance and color values.  Prepare a correlation plot and discuss the use of UV absorbance and color as surrogates for TOC.

8.      How would you account for the differences in behavior observed between the two pH's (i.e., between series A and series B)?

 

 


Laboratory #6

CHLORINATION

 

PURPOSE

               To become familiar with the DPD titrimetric method for residual chlorine and to examine the kinetics and stoichiometry of the reaction between chlorine and ammonia.

 

REFERENCES

 

Sawyer & McCarty:    

3rd ed.

pp. 64-65, 85-90, 94-119, 324-329, 385-398.

 

Sawyer, McCarty & Parkin

4th ed

pp. 71-73, 93-98, 187-212, 423-434, 493-508.

 

Sawyer, McCarty & Parkin

5th ed

pp.

 

Snoeyink & Jenkins

 

pp. 386-399.

 

 

(14th ed)

pp. 309-315, 329-332.

 

Standard Methods:

(15th ed)

 

 

 

(16th ed)

pp. 294-297, 306-309.

 

 

(17th –20th ed)

sect 4500-Cl A; sect 4500-Cl F.

 

Rubinson

 

pp. 304-313.

 

EXPERIMENTAL PLAN

               A buffered ammonia solution will be chlorinated at different doses.  Residual chlorine and chloramine concentrations will be measured as a function of time.  The data will be plotted as a function of Cl/N mole ratio and conclusions regarding the chlorine-ammonia reaction will be drawn.  In a parallel set of experiments, a treated drinking water sample will be chlorinated at a couple of doses and the chlorine residual will be followed over a period of several days.

 

PROCEDURES

               A.  Timed Breakpoint Curve

1. Prepare a series of nine 600-mL beakers containing 400 mL of the pH 7.3-buffered NH3 solution.  Add, in turn, the indicated volumes of the 50 mg/L stock chlorine solution to the requisite number of beakers and mix well.  Record the time of each addition.  Since you are going to be sampling these beakers and measuring residual chlorine after 5 and 60 minutes, it is important that the chlorine additions be spaced so that there will be sufficient time to perform the analyses (Measurement of the chlorined residual requires about 6 minutes).  Group assignments are as follows:

 

                                                            3 Groups per Lab Period

Group #

mL chlorine

1

2, 4, 8

2

12, 16, 20

3

24, 28, 32

 

 

 

                                                            5 Groups per Lab Period

Group #

mL chlorine

1

2, 4, 8

2

12, 16, 20

3

24, 28, 32

4

6, 10, 14

5

18, 22, 30

 

2. Using a graduated cylinder, withdraw 100-mL aliquots from each of the beakers after 5 and 60 minutes of contact and analyze for free and combined residual chlorine immediately.  Rinse graduated cylinder between sampling.

3. Pipet 25-mL aliquots from each of the beakers after 50 minutes and analyze for ammonia-nitrogen immediately.  Rinse pipet between sampling.

 

 

               B. Residual Chlorine Analysis  (DPD Titrimetric Method)

1. Place 5 mL of both the buffer reagent and the DPD indicator solution in the titration flask and mix.

                           2. Add 100 mL sample and mix.

3. Free Residual Chlorine (FRC): Titrate rapidly with standard ferrous ammonium sulfate (FAS) titrant until the red color disappears (Reading A).

4. Monochloramine (MCA): Add one very small crystal of Potassium Iodide (KI) to solution from step 3 and mix.  Continue titration until the red color again disappears (Reading B).

5. Dichloramine (DCA): Add several crystals of KI (about 1 g) to the solution titrated in step 4 and mix to dissolve.  Allow to stand for 2 minutes and then continue titration until the red color is again discharged (Reading C).  For very high dichloramine concentrations, allow an additional 2 minutes standing time if color driftback indicates incomplete reaction.  When dichloramine concentrations are not expected to be high, use half the specified amount of potassium iodide.

 

                           6. CALCULATIONS

    The various forms of chlorine residual are best calculated according to the following scheme.  Note that for a 100 mL sample, 4.00 mL standard FAS titrant = 1.00 mg/L residual chlorine.

 

Species

Formula

HOCl + OCl-

A/4

NH2Cl

(B-A)/4

NHCl2

(C-B)/4

 

 

 

               C. Long-Term Chlorine Residual

                           1. Measure the chlorine residual for the finished Amherst water.

                           2. Dose the raw and finished Amherst water (approx 2 liters) with chlorine as follows:

 

                                                                           3 Groups per Lab Period

Group #

Sample

mg/L chlorine

1

Raw

2 & 5

2

Finished

2 & 5

3

Finished

10

 

                                                                           5 Groups per Lab Period

Group #

Sample

mg/L chlorine

1

Raw

2

2

Raw

5

3

Finished

2

4

Finished

5

5

Finished

10

 

                          3. Partition off the chlorinated samples into 5 BOD bottles (300 mL each).  Be certain that a good water seal exists.

                           4. Store the bottles in a cabinet and record room temperature.

                           5. Measure the residual in one bottle of each type on the day assigned to your group.

 

 

                                                            3 Groups per Lab Period

Group #

Days after Chlorination

1

1

2

3

3

6

 

                                                            5 Groups per Lab Period

Group #

Days after Chlorination

1

1

2

2

3

3

4

6

5

8

 

APPARATUS

 

               A.  One set for each Group

                           1.  Burette and stand

                           2.  Magnetic Stirrer with bar

                           3.  100 mL beaker

                           4.  100 mL graduated cylinder

                           5.  20 mL pipet

                           6.  5 clean BOD bottles

 

               B. One set for entire Class

                           1.  Thermometer

                           2.  1000 mL graduated cylinder

                           3.  miscellaneous pipets

 

REAGENTS

               A.  Timed Breakpoint and Long-term Demand

1.  Buffered Ammonia solution:  Prepare 10 liters of a 0.010 M K2HPO4 solution in distilled water.  Add 9.55 mg NH4Cl to give a concentration of 0.25 mg/L NH3-N.  Adjust pH to 7.3 with HCl or NaOH.

2.  Standard chlorine solution (50 mg/L): Dilute about 1.5 ml of the 5% HOC1 stock to 1 liter.  Titrate against the FAS the morning of the laboratory and dilute as necessary to obtain a final concentration of 50 mg/L.

               B.  Residual Chlorine Analysis

1.  Phospate buffer solution:  Dissolve 24 g anhydrous Na2HPO4, and 46 g anhydrous KH2PO4 in distilled water.  Combine this solution with 100 ml distilled water in which 800 mg Na2EDTA have been dissolved.  Dilute to 1 liter with distilled water and add 20 mg HgC12 to inhibit biological growth and to control CRC interferences in the FRC titration.

2.  DPD Solution:  Dissolve 1 g N,N-diethyl-p-phenylenediamine oxalate in distilled water containing approximately 2 ml conc. H2SO4 and 200 mg Na2EDTA dihydrate.  Make up to 1 liter, store in a brown glass-stoppered bottle.

3.  Standard ferrous ammonium sulfate (FAS) titrant:  Dissolve 1.106 g Fe(NH4)2(SO4)2 . 6H20 in distilled water containing 1/4 ml of conc. H2SO4 and make up to 4 liters with distilled water.

                           4.  Potassium Iodine Crystals

 

               C.  Ammonia-Nitrogen Analysis

1.  Alkaline citrate:  Dissolve 40 g trisodium citrate and 2 g sodium hydroxide in deionized water.  Dilute to 200 mL.

2.  Oxidizing solution:  Mix 100 mL of alkaline citrate solution with 25 mL of the commercial 5% NaOCl stock.  Prepare fresh daily

3.  Sodium Nitroprusside solution (0.5% w/v):  Dissolve 0.5 g sodium nitroprusside in 100 ml high-purity water.  Store in amber bottle for up to 1 month.

4.  Phenol solution:  Dissolve 11.1 mL liquefied phenol (³89%) with 95% v/v ethanol to a final volume of 100 mL.  (you may also weigh out 17 g of crystalline phenol in place of the 11.1 mL of liquefied material).

5.  Ammonia Standard (100 mg/L as N) Dissolve 381.9 mg anhydrous NH4Cl in 1 liter of distilled water.

 

 

LAB REPORT

 

1.  Calculate the concentrations of FRC, MCA, DCA, and TRC (total residual chlorine) at 5 and 60 minutes for each of the nine samples.  Tabulate these results.  Plot these concentrations as a function of chlorine dose to initial NH3 concentration (mole-to-mole ratio).  You may wish to combine plots (e.g., you could show each species on a separate plot, and draw three curves on each of these plots representing the 5 and 60 minute data respectively).

2.  At what chlorine/ammonia mole ratio does the breakpoint occur?  Is this expected?  Why?

3.  Does free residual chlorine exist before the breakpoint?  If so, how do you explain this?

4.  Plot the residual chlorine data for all 5 long-term demand samples versus time.  Compare the relative chlorine demands.  Why do some have greater demands than others?

 

 


Laboratory #7

OZONATION BENCH TESTING

 

 

 

Still Under Development

 

 

PURPOSE

               .

 

REFERENCES

 

Sawyer & McCarty:    

3rd ed.

 

 

Sawyer, McCarty & Parkin

4th ed

 

 

Sawyer, McCarty & Parkin

5th ed

pp.

 

Snoeyink & Jenkins

 

 

 

Standard Methods:

(16th ed)

 

 

 

(17th –20th ed)

 

 

Rubinson

 

 

 

 

EXPERIMENTAL PLAN

 

 

PROCEDURES

 

 

APPARATUS

 

               A. One set for each Group

1.       

 

               B. For the entire class

1.      spectrophotometer

2.      TOC analyzer

3.      Set of Winkler reagents with pipetters

4.      Incubator set at 20°C

 

 

 

REAGENTS

 

 

 

 

LAB REPORT

1.       

 

 

 



[1] Because there is often little change from one edition to another, appropriate pages in several editions of the course texts and supplemental texts are listed.  However, important changes are occasionally made, and for this reason, the most recent edition that is readily available should be consulted.