OC Laboratory
| Event Coordinator | Event Vice-Coordinator |
| Melodi Clark Surveillance Lab Manager Wastewater Chemist III City of Columbus | |
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2025 Laboratory Event Description *UPDATED 3/13/2025 | Laboratory Event Tutorial*NEW Tutorials should be used as an overall suggestion not 100% accurate |
| Bench Sheet and Calculations | Equipment Purchase | Tables | |
| Chlorine Bench Sheet*NEW | Discount Codes for Hach purchases (20% off) *NEW US - LABTEST | Table Layout *NEW | |
| Phosphate Bench Sheet*NEW | |||
| Calculations for the PO4 and CL2 solution/concentration | |||
| 10209 instructions | |||
**These videos are for informational purposes only and may not necessarily be a clean run.
Questions accepted up until 9/23/25. Questions can be asked at the pre-competition meeting on Monday, September 29, 2025 in Chicago, Illinois.
| Question | Answer | Date |
| Approximately when might we see the new Lab Event procedure? We know you are working hard on it, but it would be very helpful to have an ETA, just so we don't have to keep checking the site every few days. Thank you! | We should have it up by end of next week 1/24/25 | 1/14/25 |
| Can you explain/demonstrate the math formula used to calculate the PO4 and CL2 solution/concentration? | Click here for the written calculations. | 1/26/25 |
| The procedure mentions two tables, one with the spectrophotometer. Are both tables the same size, (dimensions)? Or will both analyses be performed on one table and the spectrophotometer will be a standalone on the other table? | We will using the lab tables that we have had for the past lab events. There will be 2 tables so each test can performed on its own table with the spec on 1 of the table to perform the readings. The table dimensions are 96”L x 30”W x 36”H. | 1/28/25 |
| The equipment list includes trays for glass ware and waste containers. Is this equipment located on table #2? | The trays will be on the opposite table from the where the Hach DR3900 spec is located. | 1/28/25 |
| For lab supply ordering/setup - The material list notes you need 1x 4L bottle of DI water and one 10L carboy for dispensing the DI water, but the table layout indicates 2x 4L bottles of DI water. Will the DI water be in a carboy for easier dispensation or will we need to order 2x 4L DI bottles to pour directly out of? | The 2 4L bottles will be dumped into the 10L carboy for ease of use. | 1/29/25 |
| Will there be a "OPS Challenge Kit" available for purchase through HACH? The vendor booth at WEF said there would be, but I'm not seeing anything about it posted and our sales rep hasn't heard anything either. We'd like to order ASAP so we can get practicing. | There is no kit from Hach but they have provided these discount codes that can be used every time you order it gives you 20% off. US - LABTEST Canada – LABTESTCA | 1/30/25 |
| Is there going to be a new table layout, it still shows the old layout | Yes there will be a new table layout coming soon. | 1/30/25 |
1. Will the DR3900 be turned on during setup? | 1. Yes it will be turned on 2. Yes there will be 2 carboys 1 with DI water and 1 with Tap water. They will be labeled. 3. No the tap water will go into a 250 ml beaker for use. *UPDATED* | 1/31/25 UPDATED 2/7/25 |
| 1. For the Chlorine Standard Additions, are we pulling from the chlorine ampoule standard, or the standard solution created in the first part? 2. How many 500 mL wash bottles are on the table? The instructions say 2 DI wash bottles, but the questions above say there will also be a Tap wash bottle? | 1. You are pulling form the standard solution created in the first part of the Chlorine procedure. 2. I have updated my answer. The tap water will come out of a 250 ml beaker not a 500 ml wash bottle. | 2/7/25 |
| 1. How many DI carboys will be on the table? In the layout provided in the description it shows two of them, however, questions have made it seem as though there will only be one. 2. On the phosphate analysis sheet, in the space "unknown" is this the 10, 15, 20, or 30 concentration and then the space "calculated unknown" would be the result of the first sample multiplied by 5, correct? | 1. There will be 2 carboys 2. Yes you are correct the unknow will be one of the 10, 15, 20 or 30 and the calculated unknown will be the unknown multiplied by 5. | 2/11/25 |
| 1. Will the wash bottles be filled before the run? 2. In the description and previous questions it states that in the second round of chlorine testing you add in 0.1, 0.2, 0.3 to 10mL of DI water from the standard solution you mix in the beginning. However, running this way yields no residual and in the video it shows the standard additions coming from the chlorine beaker containing the standard from the ampule. Which beaker is the correct one to be pulling for the additions, the chlorine beaker containing the ampule or the standard solution mixed at the beginning? | 1. Yes they will be filled before by the lab coordinators 2. The beaker containing the what you poured out of the ampule is where you pull for the second round of chlorine testing. | |
How close do we have to get to the nominal concentrations to get bonus time? | Within 10% of target = 60 seconds back. Within 10-20% of target = 20 seconds back. Greater than 20% of target no time back | 2/11/25 |
1. For the 2ppm phosphate standard, the procedure indicates rinsing the 100mL volumetric flask and 100mL graduated cylinder 3x with DI, then rinsing 1x with the unknown standard. Wouldn't rinsing last with this standard potentially introduce contamination and an artificially inflated dilution concentration? 2. When rinsing the Cl2 glassware, the procedure indicates rinsing 3x with tap water (from a 250mL beaker) and 3x with DI for everything used in the event. This equates to around 48 rinses per run before any dilutions can be created. Is it possible we could investigate removing the tap water rinse? 3. When rinsing the Cl2 sample cells after the first set of readings, does the sample cell need to be rinsed with tap water 3x and DI water 3x as previously stated? If not, how many times does it need to be rinsed with DI water? | 1. This is standard lab practice to rinse with the standard. It will not artificially inflate the dilution concentration. 2. The procedure as written will be followed. If after going through competitions we feel things need changed, we will do so. | 2/11/25 |
For phosphate sample with unknown concentration, do we need to rinse the STD beaker with DI water, the dilution or both? Or do we not rinse at all. | See step 1 of the Phosphate sample with unknown concentration in the procedure. *UPDATED | 2/11/25 *UPDATED 3/4/25 |
1. Labeling step 5: Does the DI beaker need to be rinsed prior to adding DI water to it? | 1. Yes rinse 3 times with DI water 2.Yes it needs rinsed with solution once before filling with the solution. 3. Yes it needs mixed 5 times inverted at a 90 degree angle. | 2/12/25 |
In one of the previous questions it is mentioned that we need to label the 100ml volumetric flask, what do they need to be labeled as? | For the phosphate 100 ml flask should be labeled 2 mg/L PO4 for the Chlorine 100 ml flask it should be labeled 1 mg/L Cl2 | 2/12/25 |
What will the volumetric flasks be labeled? | For the phosphate 100 ml flask should be labeled 2 mg/L PO4 for the Chlorine 100 ml flask it should be labeled 1 mg/L Cl2 | 2/12/25 |
1. Can we label the beakers during set up? | 1. No this can’t be done during set up 2. No this can’t be done during set up | 2/12/25 |
| 1. Are we able to place pipette tips on the pipettes themselves during set up? 2. We rinse the tap beaker with tap water then DI water then fill with tap?..... | 1. No this can’t be done during set up. 2. Yes this is normal lab practice for this test. | 2/12/25 |
| Instructions say to pipet from the chlorine standard beaker into the 3 cells. When we do this, we can not replicate the results from the tutorial video however when we use the Cl2 beaker we get the results of the video. Please explain. | This question was asked a little differently but the answer is still the same. The beaker containing the what you poured out of the ampule is where you pull for the second round of chlorine testing that go into the 3 cells. | 2/13/25 |
| Instructions for chlorine standard additions, #4 say to add powder pillows to four sample cells. Are we adding a pillow to the blank? | No, you do not add the pillow packet to the blank. *UPDATED* | 2/14/25 *UPDATED 2/17/25 |
What exactly can't we do in setup? Setup instructions are not listed in the procedure. Ex. remove powder pillows, pipette tips, test vials, etc. from their respective bags/boxes. | The procedure has been updated to include setup instructions. | 2/14/25 |
| When will we be getting a full table layout of what we’ll have on both tables? | The table layout will be available after the South Carolina event which is March 9th. | 2/18/25 |
| When will the new Table Layout be posted? | The table layout will be available after the South Carolina event which is March 9th. | 2/18/25 |
| 1. Can I use DI wash bottle to fill Volumetric flask or do I have to use the DI beaker with DI water in it to transfer into Volumetric flask? 2. Can I use the 10L carboy to fill the graduated cylinder with DI water, if not can I use the wash bottle or is the DI beaker with DI water only used for filling? 3. After phosphate unknown sample is done do I need to repeat all the rinsing instructions for the know sample or is the initial rinse from the unknown sample sufficient for the run? 4. If DI beaker is used to fill, do I need to re rinse every time after beaker is empty and refilling is needed? | 1. Yes 2. Yes 3. Yes you need to repeat the rinsing. 4. No | 2/18/25 |
1. Since there will be two carboys on the table, will the two 4L bottles of deionized water and the one 4L bottle of tap water still remain on the table? | 1. No they will be removed for the event 2. Rinse the STD beaker 3x with DI water and 1x with the unknown phosphate sample. 3. The table layout will be available after the South Carolina event which is March 9th. | 2/18/25 |
| The above questions clarify that the Chlorine Standard Additions in the second part of the Chlorine procedure must be made using the ampoule "Cl2" beaker. Under #2 of the Chlorine Standards Addition section of the rules, it still states, "...add 0.1 mL of the chlorine standard from the STD beaker to one of the cells..." These two statements are contradictory. Therefore, will you update the rules to reflect that we must pull from the "Cl2" beaker for the Chlorine Standard Additions in the second part? | The procedure will be updated in the next version to say pull from the “CL2” beaker for the standard additions. | 2/18/25 |
Question #1 - Do all glassware used for the stock solution and standard solutions need to be dried after being rinsed with D.I. water? | 1. No they don’t need dried. 2. These are on the list for future use in this event when we add more items into the event in the next few years. | 2/18/25 |
| 1. The 2 mg/L PO4 standard procedures mention using the graduated cylinder to measure and add your calculated aliquot of unknown sample to add to the volumetric. Will the pipettes not be used for this step? Or is the volume supposed to be taken from the unknown sample and added to the graduated cylinder via pipette before adding to the volumetric? Will it be allowed to pipette directly into the volumetric to ensure accuracy of the standard? 2. What type of bottle and how much volume of unknown sample will be provided? The procedure mentions mixing the standard and the table diagram shows where it starts, but I can’t find a mention of what type of bottle this is. | 1. You are measuring 20 mls of the unknown. You can pour it directly into the graduated cylinder or use a pipette to transfer the 20 mls it is up to you. 2.It will be in a volumetric flask. | 2/20/25 |
| Question #1 - Do all glassware used for the stock solution and standard solutions need to be dried after being rinsed with D.I. water? Question #2 - We know that the 2025 lab event will include two chemical analyses, Phosphate and Total residual chlorine. Both TDS and TSS analyses no longer part of this event? Can you clarify why a 50g calibration mass, and an analytical balance are on the material list? | 1. No they don’t need dried. 2. These are on the list for future use in this event when we add more items into the event in the next few years. | 2/21/25 |
| 1. Is it acceptable to let the unknown solution bottle or D.I. water beaker touch the graduated cylinder while pouring? 2. Clarification on disposal of broken ampule pieces, and dirty paper and gloves. Will there be a separate tray for used glassware, broken ampule pieces, and dirty gloves? If so, will they be placed on the floor between two tables? or will be located on each table? 3. Clarification on pipet usage during competition. Will each table have its own set of two-stage pipets or need to be shared between tables? | 1. Yes the beaker can touch the graduated cylinder. 2. There is a tray for dirty glassware and there will be trash bins on each table. 3. There will be 1 set of pipets that will need to be shared. | 2/24/25 |
| How should we count the 20 seconds while swirling sample cells during chlorine testing? Should we use a provided timer, or is there another preferred method for keeping track of time? | There will be a timer set to 20 seconds. | 2/24/25 |
1. Will the CL2 ampules be refrigerated or room temperature? | 1. They will be room temperature 2. We will have the foam containers opened for competition 3. No. It would require opening up an entire new set of TNT tubes for each team. *Updated | 2/24/25 2/27/25*Updated |
| Where can we find the written instructions from method 10209 for reactive phosphorus? | The instructions are now posted above, 10209 Instructions, on the team resource center. Please note that you are running the ortho phosphate not the total phosphate. Make sure you are following the directions for TNT843 and not the TNT845. | 2/26/25 |
| Do the graduated cylinders need to be labeled, and if so, what should each one be labeled as? | No labeling of the graduated cylinder. | 3/3/25 |
| Will the programs used on the DR3900 be stored in "Favorites" or will the need to be selected via number from the index? | The programs will not be stored in Favorites it will need to be selected via number from the index. | 3/10/25 |
| The DR3900 touchscreen is very difficult to use, especially with damp nitrile gloves. Can a stylus be used to interact with the interface? | No we will not use a stylus for the DR3900. | 3/11/25 |
| Is there an updated procedure. The procedure posted is from 2/14 but a question was answered on 2/18 stating "The procedure has been updated to say pull from the “CL2” beaker for the standard additions" | The procedure will be updated in the next week. | 3/12/25 |
| The Hach DR3900 cost in 2023 was $5966.51. I am concerned about spending money for the spectrophotometer only to have it used for one or two years. Will the Hach DR3900 be used in the lab event for many years to come? | The lab event will be with the DR3900 for at least the next 4 years. | 3/17/25 |
| 1. I wanted to clarify a point regarding the revised instructions for the chlorine standard additions. The revised instructions state that we need to add powder pillows to all four sample cells. However, your team previously answered that no pillow should be added to the blank sample cell. Could you confirm the correct procedure? 2. Regarding the phosphate testing procedure. In the tutorial video, during the 3-minute reaction time, they repeatedly removed the test tube from the rack, inverted it several times, and placed it back in the rack. I assume this is to fully dissolve the white dried contents from the DosiCap. Could you confirm if this is the correct procedure, or should the test tube remain in the rack without being touched until the timer expires? | 1. The procedure has been updated to show 3 cells. 2. There are no rules stating you can’t touch the tubes in the test tube rack after you use the dosicap. Mixing the tubes 5 times should be plenty to mix. | 3/17/25 |
| For rinsing with tap can you do it from the car boy or does it need to come from the tap beaker | Rinsing can come from either the carboy or the tap beaker. | 3/20/25 |
| Are there any restrictions on the type of calculator we can use, or are we limited to a specific model or spec? | It can’t be a scientific calculator. | 3/28/25 |
| When rinsing, do you want the glassware dumped after each rinse, or can we rinse three times and then dump? | You need to dump after each rinse. | 3/31/25 |
| If the Unknown Sample can be at a concentration of 10,15,20, or 30mg/L, using the C1*V1=C2*V2 formula, I'm calculating an expected V1 between 20.0mL and 6.67mL for 'Phosphorous Standard Solution' depending on which concentration above is used. The graduated cylinder is only graduated in 1mL increments, so it's not possible to pour an accurate volume into it without using a pipet. Is my math wrong? Also, in the example video the analyst pipets directly from the Unknown Sample Bottle to the Volumetric Flask skipping the Graduated Cylinder completely, is this something we can do? | Please refer to Phosphate Sample with unknown concentration step 1. You always measure 20 mls of the unknown into the graduated cylinder then bring to volume. The 2mls you take from the graduated cylinder and put into the tnt tubes will give you a reading that will then be multiplied by 5 to give you what the unknown true value is. You don’t use the C1V1=C2V2 for this step. | 4/3/25 |
| "Please refer to Phosphate Sample with unknown concentration step 1. You always measure 20 mls of the unknown into the graduated cylinder then bring to volume. The 2mls you take from the graduated cylinder and put into the tnt tubes will give you a reading that will then be multiplied by 5 to give you what the unknown true value is. You don’t use the C1V1=C2V2 for this step." Sorry, I don't think my question was clear enough. I'm asking about the second set of tests for Phosphate, AFTER the unknown concentration is determined as mentioned above. The way the directions are written, I'm adding the calculated volume from part 1 to a volumetric flask to make 100mL of 2 mg/L PO4 solution. Step 2 Part C states "Rinse graduated cylinder 3 X with DI water then rinse 1 X with sample, add the volume of sample that was calculated in the previous step." In the situation where the unknown concentration is 30mg/L, the volume needed (as I'm calculating) to make a 2mg/L solution is 6.67mg/L ([2mg/L*100mL]/[30mg/L]). As the directions are written, we're pouring sample into the graduated cylinder to measure out the calculated volume and then into the volumetric flask. Is this correct? | They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL). Solve for x (V1) = 6.67 mL The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs. | 4/4/25 Updated 4/7 |
| After calculating the "Phosphate Sample with Unknown Concentration", which should be either 10, 15, 20, or 30 mg/l PO4, we then begin making a 2 mg/l "Phosphate Standard Solution". Under "Phosphate Standard Solution" (Steps #1 and #2), we calculate the 2 mg/l PO4 standard using C1V1=C2V2 formula. The V1 value calculated will be either 20, 13.3, 10, or 6.67 ml, for a 10, 15, 20, or 30 mg/l PO4 respectively. It states under Step #2 to use the graduated cylinder to measure these quantities, 20, 13.3, 10, or 6.67 ml. The graduated cylinder reads in increments of 1 ml. How are we supposed to measure values such as 13.3 ml or 6.67 ml using the graduated cylinder? Or should we be using the tensette pipette to measure the V1 value? | They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL). Solve for x (V1) = 6.67 mL The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs. | 4/4/25 Updated 4/7 |
| Wouldn't the Unknown Sample Concentration calculated in part one of Phosphorous be C1, not V1? C1= Calculated Unknown (Result from Part 1 x5) V1= Solved for from other variables [(2 x100)/C1] with C1 being 10,15,20 or 30 C2= 2mg/L V2=100 mL In your example calculation you're using the calculated Unknown Sample Concentration from Part 1 (10mg/L) as C1 to find a V1 of 20mL | They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL). Solve for x (V1) = 6.67 mL The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs. | 4/7/25 |
| Weftec: Since the difficulty of the phosphate stage 2 test varies based on the unknown concentration. (Accuracy Difficulty Due To Volume) Will teams of the same division be given the same unknown concentration in competition? So as to ensure apples to apples comparison for the time reduction? | We will have all of the unknowns available at WEFTEC. It has not been decided how we will handle the tables or divisions yet. | 4/7/25 |
| Weftec: Since the difficulty of the phosphate stage 2 test varies based on the unknown concentration. (Accuracy Difficulty Due To Volume) Will teams of the same division be given the same unknown concentration in competition? So as to ensure apples to apples comparison for the time reduction?" Following up on this question: If a Team A receives a Unknown Sample with a 30mg/L concentration, the resultant V1 will be 6.67mL to pipette. ±10% error on a 6.67mL sample is 0.67mL, and ±20% is 1.33mL If a Team B receives a Unknown Sample with a 10mg/L concentration, the resultant V1 will be 20.00mL to pipette. ±10% error on a 20.00mL sample is 2.00mL, and ±20% is 4.00mL In this scenario Team B is FAR more likely to receive 20-60 seconds back than Team A is. | We are still deciding on how we will handle the unknown. Once we decide it will be fair for all teams. | 4/8/25 |
| "They determined that the unknown is 30 mg/L, to prepare a 2 mg/L standard, using C1V1 = C2V2: (30 ppm)(x) = (2 ppm)(100 mL). Solve for x (V1) = 6.67 mL C1 = 30 mg/L V1 = 6.67 mL C2 = 2 mg/L V2 = 100 mL The operator will now use the variable pipets to add 6.67 mLs of the 30 mg/L add to the volumetric flask and bring the volume to 100 mLs. So does this mean we can skip the graduated cylinder procedure that is outlined in Part 2, Step 2, Part C that states "Rinse graduated cylinder 3 X with DI water then rinse 1 X with sample, add the volume of sample that was calculated in the previous step." and Pipet directly from the Unknown Sample Bottle into the Volumetric Flask? Or are we pouring sample into a freshly x3 rinsed STD Beaker and pipetting from there into the Volumetric Flask? | Yes you can use the pipette if the unknown requires you to use a smaller volume. If that is the case then you will not need to rinse the graduated cylinder. You will need to ensure you use a fresh pipette tip. You will need to rinse the STD beaker with DI water 3X and pour some of the unknown into the beaker and pipette from the beaker into the volumetric flask. I will be updating the procedure to include this in it. | 4/10/25 |
| (On the CL2 ampules the range is 50-75 mg +/- 0.1) (The target is 1.0) For accuracy the objective is to be as close to the target as possible. With the variation of +/- 0.1 if a teams result is 0.80 to 1.20 on the std addition the plus/minus variation of the ampule could be the cause of this result even with the team hitting the exact volume needed to hit the 1.0 target and be within 10% of target. At WEFTEC will the Plus/ minus be considered when awarding the time reduction due to hitting the accuracy mark? (I.e team (A) has a result of 1.15, this result is 15% off the target. However +/- could mean the result is 1.05 or 1.25.) This can make a huge difference in final time as it is a swing of 60s. | In the procedure, the participants would check the COA standard value on the label of the box of ampules they are provided, and calculate the volume of standard from the ampule that would be needed to prepare a solution with a target concentration of 1 mg/L Cl2 using the concentration on the label. Although I agree that it would be difficult to get good results on that 1 ppm standard if you only know the concentration range of 50-75, but that isn’t the case. You will be able to know the standard concentration with a resolution of 0.1 | 4/11/25 |
| When will the updated procedure for the lab be posted? | If and when there are more significant changes I will post and updated procedure. | 4/24/25 |
| If we aren't using a beaker for the event does it still need to be labeled and filled? | If you don’t use the beaker you don’t have to label it but if someone decides to use it and it is not labeled then that will be a penalty. | 4/30/25 |