May 2019
May 7 & 9 - MRWA - Intermediate/Advanced Math Class III & IV Operators, Standish, DEP 10 TCH, BLWSO 10 TCH
May 8 - MRWA - Introduction to Technology: Your Computer & Excel, South Paris
May 14 - JETCC - Rehabilitation & Replacement of Underground Piping, Fairfield, DEP 6 TCH
May 15 - JETCC - Instrumentation, Control Networks, & SCADA Review, Farmington, DEP 6 TCH, BLWSO 6 TCH
May 15 - MRWA - Introduction to Technology: Your Computer & Excel, Dover-Foxcroft
May 21, 22, & 23 - NEIWPCC - O&M of Wastewater Collection Systems, Bangor, DEP 15 TCH
May 22 - MRWA - Introduction to Technology: Your Computer & Excel, Ellsworth
May 29 - MRWA - Introduction to Technology: Your Computer & Excel, Caribou
June 2 Thru 5, NEWEA - Spring Meeting & Exhibit, New Castle NH, Variable TCH
June 12 - JETCC - Real-World Nitrification / Denitrification Practices, Portland, DEP 6 TCH
Disinfection
1. The Wastewater disinfection process is designed to
a. Destroy (kill) all microorganisms in the wastewater. Typically this is the final stage of treatment before discharge.
b. Destroy (kill) the pathogenic (disease causing) microorganisms in the wastewater. Typically, this is the final stage of treatment before the wastewater is discharged.
c. Kill off harmful microorganisms before they enter the wastewater treatment facility. Typically this is a treatment process installed ahead of preliminary treatment units
d. Kill off dangerous microorganisms before they enter the sensitive biological treatment stage (secondary treatment). If not removed, these organisms will upset the biological secondary treatment process.
e. Sterilize wastewater entering the collection system to protect collection system workers.
2. Pathogenic Organisms are
a. Considered beneficial and are an essential part of biological treatment systems. They are removed from the effluent in a clarifier and returned to the head of the biological treatment unit.
b. Typically removed before the wastewater enters the treatment plant, primarily to protect the biological treatment process.
c. Viewed as harmful, disease causing microorganisms and are destroyed to prevent the spread of disease. Pathogenic organisms include bacteria, viruses or cysts which can cause diseases such as typhoid, cholera or dysentery.
d. Typically removed before the wastewater enters the collection system (primarily to protect workers).
e. Typically removed through chemical treatment using bisulfite
3. When using chlorine as a disinfecting agent, free chlorine combines with ammonia to form
a. Chlorine dioxide
b. Chlorine demand
c. Chloramines
d. Sodium Bisulfite
e. Sulfur dioxide
4. Which of the following are true regarding UV disinfection?
a. Regular cleaning of light bulbs is necessary to maintain optimal performance. UV light leaves no harmful residuals
b. Excess UV must be removed from wastewater. It can be measured with an Amperometric Titrator or DPD method.
c. The flow of UV light is usually adjusted with a rotometer.
d. UV systems work best when the wastewater is cloudy or turbid to allow a larger surface area for killing pathogens
5. A wastewater treatment plant fed approximately 101 Lbs. of chlorine over a 24-hour period. During that 24 hour period, the facility flow was 1.2 MGD and the measured average chlorine residual was 0.5 mg/l. What was the approximate chlorine demand (expressed in mg/l)?
a. 10.0 mg/L
b. 84.2 mg/l
c. 83.7 mg/L
d. 9.5 mg/L
6. In a series of bench tests, an operator has determined that in order to achieve permit limits (in regards to fecal coliform), a minimum chlorine residual of 0.5 mg/l must be maintained. The bench tests also revealed that the average chlorine demand is approximately 15 mg/l. How much chlorine must the operator feed (over a 24 hour period) to meet the chlorine demand and achieve the minimum residual of 0.5 mg/l with a flow of 1.5 MGD?
a. Approximately 16 Lbs.
b. Approximately 160 Lbs.
c. Approximately 194 Lbs.
d. Approximately 1940 Lbs.
Many facilities across the state will begin seasonal chlorination on May 15. Don’t wait until the last minute to prepare. It is a good idea to start early so there is time to make adjustments/repairs as necessary.
Your chlorine contact chamber (CCC) may have accumulated water/solids during the winter that needs to be cleaned-out/emptied. Do a thorough inspection of the chlorination system to ensure the integrity of the entire system. Meter accuracy can be verified by pumping into a bucket or barrel of known volume and comparing it to the meter readings. Tank(s) should be visually inspected for corrosion and physical damage. Verify treatment chemicals are stored to capture any leaks in a secondary containment area.
Start-up procedures for chlorination include:
o Check that all valves are in their proper position and tagged
o All piping should be inspected and found to be in operating condition
o Feed and safety equipment should be checked and found in operating condition
o Procedures should include a program to sequentially open valves, and start equipment
Once operating, the operator must verify that chemical feed rates are correct. Make sure your residual chlorine monitoring equipment is properly calibrated and/or verified. Test the total chlorine residual (TRC) at least twice on separate days and evaluate results to ensure target doses and residuals are being met. Make adjustments as needed.
Everyone that is enrolled in the DMR-QA program should have received emailed notification from EPA that Study 39 opened on March 22nd, 2019.
If you are required to do DMR-QA but did not receive the email, check your Spam folder, or go to the EPA website to download the Study 39 package:
https://www.epa.gov/sites/production/files/2019-04/documents/dmr-qa-39_0.pdf.
The study was delayed due to the government shutdown, with submission deadlines moved back approximately 2 weeks. Important deadlines include:
April 26 – Confirm receipt of Study (email Brett.A.Goodrich@maine.gov or Judy.K.Bruenjes@maine.gov).
March 22 to July 19 – Perform PT testing.
August 30 – Order retests for all “Not Acceptable” results and perform PT testing.
September 13 – Send completed paperwork (pp 10-12 of package and copy of PT graded test results) to DEP.
November 8 – Submit Corrective Action Reports and retest results to DEP for all failed analytes.
If you are enrolled in the DMR-QA program and have any questions or need to update your contact information, please contact Brett Goodrich at Brett.A.Goodrich@maine.gov or call 207-287-9034 or Judy Bruenjes at Judy.k.Bruenjes@maine.gov, 207-287-7806.
1. b.
2. c.
3. c.
4. a.
5. d. 9.5 mg/L
First, write down the pounds formula,
Pounds of chlorine (dosage) = Flow (MGD) X 8.34 X concentration (mg/L)
Next, rearrange to solve for concentration
Concentration (mg/L) = lbs chlorine / flow, MGD
Concentration (mg/L) = 101 Lbs / 1.2 MGD = 10 mg/L
This is your concentration of chlorine in the wastewater.
Next, use the formula: Dosage = Demand + Residual
Rearrange to solve for chlorine demand:
Demand = Dosage – Residual
Demand = 10.0 mg/L – 0.5 mg/L = 9.5 mg/L
6. c. Approximately 194 pounds
The problem is asking you to find the chlorine dosage in Lbs per day. First find the dosage in mg/L:
Dosage = Demand + Residual = 15 mg/L + 0.5 mg/L = 15.5 mg/L
Now plug the dosage into the pounds formula:
15.5 mg/L X 8.34 X 1.5 MGD = 193.9 which is approximately 194 mg/L.
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