Water Environment Federation (WEF) Discussion Forums / WEF Discussion Forums / Biological Nutrient Removal

RE: Online Education

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Online Education

expert_engineer42 — Tue, 29 Apr 2008 02:39:07 GMT

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RE: VFA levels in Raw Wastewater

Rob Baur — Wed, 07 May 2008 10:58:43 GMT

There will be a rough correlation, but not enough to predict Bio-P success. Sewage with very little H2S will probably have very little VFA and sewage with a lot of H2S will have more VFA, but no way of knowing if it is enough for Bio-P.

We did not have good results sending VFA samples out to labs at $100 per sample, the test is apparently very hard on GC columns and the data was highly variable. We test for VFA on an ion chromatograph using a modification of a method for VFA in wine. It is automated and can run over night. The lab doesn't even whine when I send them 24 samples from a diurnal test.

We tested Bio-P in the winter when we were off our 0.070 T-P permit to see if we could do it. It worked and gave us confidence in Bio-P. It did not work on the train we kept nitrifying. We needed more VFA to denitrify the RAS. We converted gravity thickeners to series fermentation (UFAT) and made enough VFA for Bio-P and eliminated our 30 mg/l primary alum dose.

VFA levels in Raw Wastewater

KW — Tue, 06 May 2008 16:51:03 GMT

Does anyone know of a reliable correlation between Sulfide levels and VFA's?

A consultant has reassured me that if we have have reliable sulfide levels, the VFA's will be there.

We are looking at BNR in the near future and want to find a reliable way to track VFA's without the expense and effort of the VFA testing.

Our influent dissolved sulfides are consistantly 3-5 mg/l.

Thanks

Kurt W.

RE: VFA levels in Raw Wastewater

TerryF — Wed, 07 May 2008 07:19:09 GMT

Kurt,

Others may disagree but i am not convinced that there would be a reliable correlation between level of sulfide and VFA.

Regards

TerryF

RE: Pre Filter Application of Alum for Phosphorous Removal

TerryF — Wed, 07 May 2008 07:16:33 GMT

I agree with Wiff's comments.

However as you asked specifically about alum, typically a ratio of Al to P (to be removed) of about 3:1 is okay. Note that this is not Alum but aluminium. The actual alum dose rate will depend on the concentration of Al in the alum form you use.

Regards

TerryF

Pre Filter Application of Alum for Phosphorous Removal

01813603 — Tue, 06 May 2008 11:39:25 GMT

We desire to reduce TP from about 1 mg/l after secondary clarification and through the use of an enhanced biological TP removal system to .3 mg/l TP.

It is expected TSS post clarification will be about 10 mg/l to 15 mg/l.

We plan to use a filter and are considering the option of applying alum pre filter to reduce the TP from 1 mg/l to .3 mg/l.

Given the 15 mg/l TSS and the objective of .3 mg/l TP, can someone help in regards to (1) the amount of alum required to be added and (2) the resulting combined TSS load on the filter.

Thanks

RE: Pre Filter Application of Alum for Phosphorous Removal

Wiff P — Tue, 06 May 2008 14:19:11 GMT

If the TSS is 10-15 mg/L and assuming typical suspended solids P content of 3%, your total P will be between .3 and .45 even if ortho (dissolved) P is zero. So if you're working to a total P of 0.3 mg/L may be a challenge. If you do BIO-P removal content of P in TSS will likely be even higher. Nonetheless, I assume you're using something like a cloth filter given the TSS you're shooting for and I've seen SBR's with cloth filters do this either with two point metal salt addition or blend of bio-P and trim with metal salt. You might do better with PAC (PolyAluminumChloride) for your trim dose, but some plants can achieve fairly low levels with ferric salts and poly combinations, ultimate choice depending on cost and on sludge disposal methods (in latter case some sludge options may not like to see higher levels of aluminum in sludge). Realize that the effectiveness of these coagulants is to drive soluble P quite low and at the same time help you achieve single digit TSS concentrations.

By the way some activated sludge plants are doing so well with their activated sludge fine tuning that they can get to 0.3 mg/l without a filter, at least in warmer weather. The more fine tuned the activated sludge plant and the more fine tuned the coagulant(s) dosage(s) the easier it is to get below 0.3 mg/L. Good operators routinely achieve miracles!

RE: Online Education

Rob Baur — Mon, 05 May 2008 16:32:44 GMT

Try Sacremento State Training at

http://www.owp.csus.edu/training/courses/index.php

RE: Online Education

steemrose — Fri, 02 May 2008 20:54:05 GMT

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RE: BNR nitrate reduction

g. — Thu, 01 May 2008 14:15:55 GMT

I concur with reducing air and would go with lowering D.O. to 2.0 mg/l or less in the oxic zones to force utilization of nitrate for respiration, or extend the second anoxic zone?

BNR nitrate reduction

rob — Mon, 28 Jan 2008 17:54:33 GMT

I work at a 2.0 mgd treatment plant with a 5 stage BNR. The BNR effluent NO3 averages around 8-10 mg/l and I am trying to get down to 5 mg/l. I have tried changing the return and internal recycle rates with little change. The ammonia is completely nitrified in the first oxic zone. Any suggestions to help get the nitrates lower. The BNR is being fed by primary sedimentation basins.

RE: Online Education

pighepoll — Tue, 29 Apr 2008 16:56:18 GMT

hi frnd,
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RE: Rain and ammonia removal

operador — Sun, 27 Apr 2008 04:05:08 GMT

TN increases due to higher ammonia levels, nitrite and nitrate remain constant. I´m looking at different models to simulate plant conditions.

Thanks

Rain and ammonia removal

operador — Wed, 23 Apr 2008 11:42:03 GMT

Can anyone find an explication for the following:

BNR removal plant, 800cu m anaerobic reactor, 3.000 cu m anoxic reactor, 7.000 cu m oxic reactor. Flow 20.000 cu m /day, COD 400 ppm, BOD 180 ppm, SS 125 ppm, TKN 70 ppmN, NH4 53 ppmN, P 6ppm settled sewage mainly domestic ww. MLSS 3.000 - 4.000 ppm, BOD loading <0,1 Kg / KgMLSS. Internal recycle 200%, external 80%.

Plant complies to discharge limit of 10 ppm TN, except during wet spells. The plant is in a normally dry climate, when it rains the temperature in the reactor drops 2 - 3ºC, last episode from 22 to 19ºC. The hydraulic load is kept constant, excess flow is diverted after primary sed. and plant loading is reduced by approx. 40%, but ammonia levels in the effluent increase. nitrite and nitrate remain constant. When rain ceases results return to normal after about 5 days.

RE: Rain and ammonia removal

TerryF — Sat, 26 Apr 2008 18:33:40 GMT

A drop of that magnitude will only slow the process down , but won't be too drastic. I would be concerned about all the other things that will be happening when you get a large amount of infiltration , flow diversions etc. Even though your numbers look okay at face value there will be things happening with pH , alkalinity , and conductivity as well as interactions between hetertrophic and nitrifying bacteria that change because the loading is totally different. A biomass in any treatment plant tends to become acclimatised and the population dynamics adjusted to the unique load charateristics of that plant. A major rain event changes those characteristics by dilution of the sewerage with water that is clean low pH and low condictivity and sometimes carrying substantial amounts of nitrogen. Addittionally infiltration often brings with it silt , pollutants and nutrients as run off from urban areas which will again change the whole dynamics of the load.

Only closer monitoring of plant conditions during such events would a definitive answer be able to be given.

REgards

TerryF

RE: Rain and ammonia removal

d jenkins — Sat, 26 Apr 2008 18:31:40 GMT

Several things could be happening:eg the lower temp will slow down the rate of nitrification; the rainwater could be introducing DO into the anoxic zone, decreasing denitrification...is the increase in effleunt TN due to increases in ammonia or nitrate or both? The measurement of these should give you a clue to what is happening. To understand problems like these you really need to meodel your system on a model such as Biowin.

David

RE: Rain and ammonia removal

operador — Fri, 25 Apr 2008 12:33:07 GMT

TerryF

Thanks for your reply. We dont have separate sewerage systems, so the temperature drop is due to the colder rain water.

Do you think a 2 - 3ºC drop could affect the nitrifiers?

RE: Rain and ammonia removal

operador — Fri, 25 Apr 2008 12:29:01 GMT

Thanks for your posting

We only measure pH in the settled sewage and effluent. Normal levels are between 7,4 - 7,9, and we dont observe drastic changes during wet spells. Our ww is very well buffered, conductivity 3.500 micro siemens (reduced during wet spells). Would you recommend registering pH in the aeration basins or perhaps alkalinity in the effluent?

DO is automatically controlled and possibly is higher during wet spells.

We keep MLSS relativley stable, and reduce sludge wasting during wet spells. Our wet spells could last, at most, two days.

RE: Rain and ammonia removal

TerryF — Fri, 25 Apr 2008 05:42:58 GMT

There is a chance that the pH lowers substantially with infiltration as rain water is pH 5.7 or thereabouts. Nitrifiers generally don't like rapid changes in pH. The temperature drop probably is related to infiltration as well.

Regards

TerryF

RE: Rain and ammonia removal

Wiff P — Thu, 24 Apr 2008 11:11:31 GMT

What happens to mixed liquor pH and DO levels before and during rain events? Are your mixed liquor concentations relatively stable during these events?

RE: Carbon Source for Denitrification

WaterPlanet — Fri, 18 Apr 2008 16:18:15 GMT

We use sugar to provide synthetic influent to a seasonally under loaded SBR. It is a small plant and we only add 25-30 pounds per week. Each pound of sugar is approximately equal to 500 gallons of 250 mg/l BOD influent. Pros: cheap, readily available 24/7 at Wal-Marts everywhere. Cons: a drag to buy and mix, slime grows in mixing tank and piping, will ferment. (Will also freeze.) Cannot speak to sludge production...

We use Micro-C for denite at four small treatment plants. Is more costly and can get sticky if you are sloppy, but otherwise is a good product.

I've been told that sodium acetate can be used, but know little about it.

Carbon Source for Denitrification

yoyoyuri — Mon, 03 Mar 2008 15:34:21 GMT

Where can I access a comprehensive evaluation (relative strengths, cost, dosage rates, COD value, dis/advantages, etc) of Carbon Sources (methanol, ethanol, MicroC, glycerin, etc.) for denitrification? If there isn't such a source, I'd appreciate if some members could summarize what they know about each.

Thank you.

RE: Low level chlorine measurement.

Dvant — Thu, 17 Apr 2008 17:04:49 GMT

Hach has an ultra low method that is EPA approved and is easy to use, Hach method 10014.

We figured there would be less error between operators with this method.

Mark

Low level chlorine measurement.

01630545 — Thu, 17 Apr 2008 15:44:38 GMT

We chlorinate (Cl2 gas) and dechlorinate (SO2) seasonally for fecal control and we have a discharge permit limit of no more than 0.05 mg/L chlorine. Currently we measure the chlorine with an ORION residual chlorine ISE probe (replaced yearly) that always gives us calibration fits. The calibration is per CFR40 part136 with 0.2, 1.0, and 5.0 mg/L chlorine standards. The calibration takes forever, slope is nearly always 30 or above. The permit limit is way outside the calibration standards. Is there a better way to measure a next-to-nothing chlorine residual in dechlorinated effluent?

Thanks,

Gregg

RE: Carbon Source for Denitrification

fixedfilmenr — Thu, 17 Apr 2008 16:25:15 GMT

See January 2008 issue of WEF WE&T article : Got Carbon? - Widespread biological nutrient removal is increasing the demand for supplemental sources for comparisons.

RE: Carbon Source for Denitrification

fixedfilmenr — Thu, 17 Apr 2008 16:20:52 GMT

Does anyone have experience with the use of sugar water as a carbon source? Also I am looking for relative sludge production rates from various carbon sources. I am being told sugar water will produce more sludge than methanol (avoiding due to flammability).

Thanks

RE: Low level chlorine measurement.

rwhitworth52 — Thu, 17 Apr 2008 16:01:53 GMT

Amperometric titration (foreward or backward). Hach has an auto-cad 9000 that's nice but expensive (5K). Gives good repeatable results.

RE: Seeking career opportunity -

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Seeking career opportunity -

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RE: Seeking career opportunity -

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RE: Seeking career opportunity -

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RE: List of BNR Plants

TJlrbchevy — Tue, 15 Apr 2008 11:44:24 GMT

This would be interesting from an analytical point of view...would this be a litmus test of progressiveness?

I hope someone can share...

List of BNR Plants

dmiles1 — Mon, 14 Apr 2008 20:37:50 GMT

I am public policy Ph.D. student and my dissertation research is in the area of the economics of biological nutrient removal. I am in the process of compiling a list of plants across the country that have been upgraded to BNR and also a list of new plants that were built with BNR as part of their initial design.

Does anybody have any suggestions if such a list exists and where I might find it?

Or if a list does not exist, what states have a large number of BNR plants?

Thank you!

RE: Carbon Source for Denitrification

WaterPlanet — Mon, 14 Apr 2008 18:33:53 GMT

The January 2008 WE&T had an article on this very subject: pages 9-53. I reworked the numbers and checked them with my Micro-C distributor.

If you need, for example, 100 gallons of Micro-C to get the carbon you need, you will need the following amount of various other products to feed the same amount of carbon...

Methanol: 53, Ethanol: 38, Acetic Acid (100%): 50, Acetic Acid (20%): 288, Sugar: 92, UnicarbDN: 84, Sludge supernate: 105,000.

Having said this, I am against using alcohols (methanol or ethanol). They are flammable, potentially explosive. Not worth the risk in the plants my company operates.

RE: What is the reason for ammonia increase after activated sludge treatment?

Milos — Mon, 31 Mar 2008 07:16:15 GMT

Too little data for answer. Key data are in the mass balance of the total nitrogen; inflow (before and after primary clarifier) - in kg/d. Also the external flows - externa substrate in the digestion, dosing of nutrients into biological stage.

What is the reason for ammonia increase after activated sludge treatment?

ahawater — Sun, 07 Oct 2007 08:46:37 GMT

In a activated sludge process, BOD influent concentration is from 3600-10000 mg/l, average is 6000 mg/l. BOD and COD ratio is 0.43-0.7. F/M in the aeration tank is from 0.5 to 1.3. Average F/M is 0.7. BOD and COD removal percentage in the activated sludge process is very high, over 95%. The performance of aeration tank seems good. Ammonia concentration in the influent is from 0.8-7.9 mg/l, average concentration is 4.6 mg/l. But effluent of clarifier ammonia concentration is much higher than the influent. The range is from 8.6-42.1 mg/l, average is 24.4 mg/l.

Why does the ammonia concentration increase? Is the F/M ratio too high? Please help me identify the reasons.

Thanks.

RE: What is the reason for ammonia increase after activated sludge treatment?

Jerry — Sat, 29 Mar 2008 19:53:19 GMT

It may be spending to much time in the clarifier and getting anaerobic. Try increasing the return rate. The usual number is 100 % return rate of the influent flow.

RE: What is the reason for ammonia increase after activated sludge treatment?

Wiff P — Sat, 29 Mar 2008 11:09:58 GMT

I would agree with Woody's suggestion. The organic N component of influent BOD is being converted to ammonia as BOD is broken down. Running influent and effluent TKN (which will give you ammonia N and organic N which combined equal TKN) will likely confirm the conversion of organic N in the influent to ammonia N in the effluent. At these F/M's you'd expect that!

Wiff Peterson

RE: What is the reason for ammonia increase after activated sludge treatment?

Cocodrie — Wed, 26 Mar 2008 21:04:36 GMT

I would add to the list of things to watch:

Alkalinity - well known culprit when lacking;

Nutrients, especially phosphate.

Industrial wastes will often be out of balance when compared to domestic in which bacteria thrive.