June 2019
June 2 Thru 5 - NEWEA - Spring Meeting & Exhibit, New Castle, NH, Variable TCH
June 4 - MRWA - ABC's of Distribution Maintenance, Caribou, BLWSO 4 TCH
June 5 - MRWA - ABC's of Distribution Maintenance, Ellsworth, BLWSO 4 TCH
June 6 - MRWA - ABC's of Distribution Maintenance, York, BLWSO 4 TCH
June 7 - MRWA - ABC's of Distribution Maintenance, Richmond, BLWSO 4 TCH
June 11 - MRWA - Lead & Copper: Strategies to Control These Heavies, Calais, BLWSO 3 TCH
June 12 - JETCC - Real-World Nitrification/Denitrification Practices, Portland, DEP 6 TCH
June 13 - MWUA - June 2019 Bi-Monthly Meeting, Houlton, DEP 2 TCH, DWP 4 TCH
June 13 - MRWA - Lead & Copper: Strategies to Control These Heavies, Mexico, BLWSO 3 TCH
June 18 - MRWA - Get the Most from Your Chart of Accounts, Hampden, DEP 3.5 TCH, BLWSO 3.5 TCH
June 19 - MRWA - Lead & Copper: Strategies to Control These Heavies, North Berwick, BLWSO 3 TCH
1. What is the volume in gallons of a rectangular tank that is 10 ft by 30 ft by 16 ft?
a. 2,502 gal
b. 4,800 gal
c. 36,000 gal
d. 40,032 gal
2. How long will it take to fill the tank above if the flow entering the tank is 1.3 MGD?
a. 40 minutes
b. 42 hours
c. 4 days
d. 3.6 minutes
3. What is the volume of a tank in gallons if it is 12 feet deep and has a diameter of 30 feet?
a. 5,284 gal
b. 8,478 gal
c. 10,800 gal
d. 63,415 gal
4. How long will it take to fill the tank above if the flow entering the tank is 1.3 MGD?
a. 52 hours
b. 1.2 minutes
c. 1.2 hours
d. 5.2 hours
5. Your superintendent wants to know how efficient your primary clarifier was at removing
solids during a major rain storm a few days earlier. The lab tech tells you that the average 24-hour composite TSS of the sewage entering the primary settling tank on the day in question was 228 ppm, and the average 24-hour composite TSS of the effluent that same day was 87 ppm. What do you tell the superintendent was the approximate percent removal?
a. 86%
b. 99%
c. 52%
d. 62%
6. What is the mixed liquor suspended solids concentration given the following?
Initial weight of filter disk = 0.45 gm
Volume of filtered sample = 60 mL
Weight of filter disk and filtered residue = 0.775 gm
a. 0.005 mg/L
b. 0.5 mg/L
c. 3417 mg/L
d. 5417 mg/L
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Spring is in the air, and for some wastewater lagoons, that means foul lagoon odors are in the air, too. In this short article, we’ll talk about seasonal lagoon turnover, why the spring turnover can be the most severe, and how to prevent it.
What is lagoon turnover?
An improperly mixed wastewater lagoon will settle into layers, with denser, cooler water at the bottom and lighter, warmer water at the top. This is known as thermal stratification. In spring and fall, the change in ambient temperatures causes the layers to mix and eventually create a uniform temperature. As they begin to de-stratify and mix, the settled solids become re-suspended and the odorous gases trapped at the bottom are released to the surface. In a healthy, functional lagoon, this process should take about a week. In a well aerated and mixed lagoon, it won’t happen at all.
What makes spring lagoon turnover so severe?
Spring is usually the time of highest BOD loads in a wastewater lagoon. You’ve got the BOD that’s been stored over the winter, new influent BOD, and the BOD demands of the accumulated sludge at the bottom of the lagoon.
In the spring, increased sunlight warms the top layer of the lagoon, melting the surface ice and allowing sunlight to penetrate, creating convection currents. Gradually, with the sun’s warmth and wind, the entire lagoon reaches a uniform temperature and circulation increases.
This increased circulation disturbs the accumulated sludge and solids that have been lurking at the bottom of the lagoon. They get pushed to the surface, releasing hydrogen sulfide (H2S), the stinky gas that is generated by anaerobic digestion. The dislodging of the settled sludge and solids also results in benthal feedback or benthal release, which is when nutrients like nitrogen and inorganic materials like metals that have been trapped in the sludge get released back into the lagoon. Benthal feedback can cause ammonia levels in the lagoon to be higher than in the influent.
As water warms in spring, sludge and accompanying odors can rise to the surface
Once the temperature hits 50°F or so, bacterial action begins in earnest and starts to consume all of the BOD that’s been stored up over the winter. The problem is, BOD-eating bacteria need dissolved oxygen to work, and there just isn’t enough. In the spring, a wastewater lagoon can need as much as triple the usual amount of DO—as much as 5–6 lbs. of O2 per pound of influent BOD—to handle the increased load.
Problems Caused by Lagoon Turnover
Without sufficient DO, the bacteria resort to anaerobic digestion, which is a slow and smelly process. Sludge accumulates, odors linger, and effluent violations from under-treatment are likely. Symptoms of anaerobic digestion include:
1. Floating sludge: As the increasing sunlight and wind circulate the water, the solids settled at the bottom, which have been quietly anaerobically digesting, are churned up. The anaerobic digestion process releases gas as a byproduct, which becomes entrained in the sludge. Once dislodged, the gas trapped in the sludge causes it to rise from the bottom of the lagoon and float.
2. Intense Odors: With the rising gas byproduct of anaerobic digestion, unpleasant lagoon odors are released into the atmosphere all at once. These odors, coupled with those of the floating sludge mat, are strong during lagoon turnover. If picked up by the wind, these odors will make your neighbors complain.
3. Lagoon Treatment Suffers: Lagoon turnover can be a sign that your lagoon is septic and is breaking down nutrients via anaerobic digestion. Expect a spike in effluent BOD, TSS, and other treatment parameters at some point in the near future if corrective action is not taken.
How to Prevent Spring Lagoon Turnover
To prevent lagoon turnover you need to combat the causes of the problem itself:
1. Increase circulation to prevent stratification: By continually circulating the water, the lagoon layers will never be able to fully stratify. With both a homogeneous lagoon water temperature and environment, no spring lagoon turnover will occur.
2. Increase dissolved oxygen levels to combat low DO: One of the easiest ways to do this is to add aeration to your lagoon. By maintaining an aerobic environment, you will limit the production of noxious H2S gases.
3. Increase mixing to prevent sludge buildup on the bottom: Proper lagoon mixing limits sludge accumulation by keeping it up into the water column where it can break down aerobically and odor-free.
DMR-QA Study 39 opened on March 22, 2019 and closes on July 19, 2019. Information about the study can be found at https://www.epa.gov/compliance/2019-discharge-monitoring-report-quality-assurance-dmr-qa-study-39.
Recently some questions about the study have been sent to the National DMR-QA Coordinator at EPA Headquarters. If you have any questions about the study please contact the DMR Coordinator for the Maine DEP at Brett.A.Goodrich@maine.gov or 207-287-9034. This will help ensure the fasted response to your inquiry.
Did you know that DEP accepts online training and webinars for continuing education TCH credit? Courses must be at least 1 hour in length and relevant to wastewater treatment or wastewater safety. In addition, you must submit a Certificate of Completion to show you attended the entire course.
If the webinar or online training is not already approved by DEP, you can request approval by submitting course information to NEIWPCC at certification@neiwpcc-jetcc.org and they will forward the request to DEP for review and approval. Submittals must list course and instructor information, including a syllabus or agenda that details the training hours and topics.
It is always a good idea to submit the required documentation before attending a course to make sure it is approved by DEP, but training can also be submitted for approval after the course is completed.
For more information about certification, contact judy.k.bruenje@maine.gov. For information about certification administration, call NEWIPCC at 207-253-8020, or email certification@neiwpcc-jetcc.org.
1. c. 36,000 gal
Tank dimensions: 10 feet by 30 feet by 16 feet.
First, find Vol in FT3 = (10’)(30’)(16’) 30’ = 4,800 FT3
How many gallons can fit in 4,800 FT3 ?
Vol in gallons = 4,800 FT3 (7.48 gal/ FT3 )
Vol in gallons = 35,904 gal which is rounded up to 36,000 gal.
2. a. 40 minutes
Vol = 36,000 gallons
Flow = 1.3 MGD = 1,300,000 gals/day
Time to fill tank = Volume/Flow
36,000 gal/ 1,300,000 gal/day = 0.028 days.
Time in hours: 0.028 days X 1440 min/day = 39.7 minutes. Round up to 40 minutes.
3. d. 63,415 gal
Tank dimensions: Depth (or Height) = 12’, Diameter = 30’
Vol in FT3 = 0.785 X 30’ X 30’X 12’
Vol in FT3 = 8,482 FT3
How many gallons can fit in 8,482 FT3?
Vol in gallons = 8,482 FT3 X 7.48 gal/FT3
Vol in gallons = 63,415 gal
4. c. 1.2 hours
Vol = 63,415 gallons
Flow = 1.3MGD = 1,300,000 gals/day
63,415 gallons / 1,300,000 gal/day = 0.0488days
0.0488days X 24 hr/day = 1.2 hours
5. d. 62%
Efficiency = (Value In – Value Out)/ Value In X 100
TSS entering the primary clarifier = 228 mg/L
TSS leaving the primary clarifier = 87 mg/L
Plugging in the numbers:
Efficiency = (228 mg/L – 87 mg/L) / 228 mg/L X 100 = 61.8% round up to 62%
6. d. 5,417 mg/L
MLSS is the suspended solids of the mixed liquor in the aeration basin.
First, subtract the weight of the filter disk to find weight of solids, and divide by 1 million to find weight in mg.
Suspended Solids = (Wt2 – Wt1)(1,000,000)
Suspended Solids = (0.775gms – 0.45gms)(1,000,000) = 0.325 mg
Next, divide the mass by the sample size in liters:
Sample size in liters: 60 mL
Suspended Solids = 0.325 mg / 60 mL = 0.005417 mg/mL = 5,417 mg/L
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