The citys H2O plant is surface water, I used SM 2320 B titration method for the testing.

Thanks, Laurie

Are those the end-point pH's or the Alkalinity in mg/l ?

Bob Whitworth

Laurie,

Don't try to keep the MLSS the same in the two basins what i was trying to gauge was whether they were equally loaded or not and it sounds like they may not be. Does your cycle step duration change with the volume of inflow , or is it preset. If you are able to preset i would move some time out of anoxic fill to aerated fill so that at a minimum you always get 140 minutes of aeration time (aerated fill plus react). I assume you are running four , six hour cycles a day. If they are based on volume it would appear that #2 maybe getting more load at least at times. It is also possible that even if it does not get more volume it may be getting a higher ammonia load.

Whilst you can convert ammonia to nitrate at low levels of DO , levels above about 1.5mg/l is best. Without knowing your loading or aeration details i would suggest that by the end of the aerated fill you should have DO somewhere about 0.5-1.0 mg/l and by the mid point of the react you should be getting close to 2 mg/l and be holding that through to the end of the aerated period. With those really short react periods you may have trouble unless you are getting up 1+ by the end of the aerated fill. These DOs will alter depending on your loading. One sbr plant i was involved ended up being so heavily loaded that unless the DOs were 4mg/l at the end of react ammonia removal was always poor.

Take a sample off the top of the basin soon after is finished aerating and you have a small amount of clear water on top to sample from and then compare the ammonia levels with the sample during decant. If the first is good and the second is a lot worse it will either point to ammonia(raw sewage) bleeding through from the inlet or other problems.

If you can also compare the volume of air supplied to the two basins. If no other means exist read the electrical meters when each basin starts and stops aerating. Over a few cycles it should give a comparison on the amount of energy being used to aerate each basin. More energy should mean more air unless you have a major defect somewhere.

Regards

TerryF

 your right, I was looking at the beginning ph. My Influent alkalinity is about 300mg/l, and effluent is 200mg/l. Are those sufficient levels?

Thanks,

Laurie

My cycle durations are flow dependent. I have minimum aeration set on 140mins, full batch aeration on 165mins, max anoxic at 90mins., settle time at 70min. I did notice that I'm getting 50-60min in idle, I spoke with the sysyem programmer this morning, and he had me up the anoxic fill from 250min to 275min. he said that would force 25mins into react. My mlss for today is #1 2700 and #2 3100. But #2's micro-count looks low. I lowered my waste time to mins. on #2. #1 is at 4mins. I dont have a way to measure D.O. air volume, but I will try your suggestion. I'm not very good with electrical operations. I did measure my D.O. readings in each basin during react yesterday, #1 is great, .6 starting out and 4.5 at the end. #2 is not so good, .3 starting out and 1.5 at the end. I'm thinking about having someone check the blower on #2 for performance. Also I ran ammonia's this morning, and #2 has risen up 20.7 to 22.5 overnight. I dont know what I'm doing wrong, every book tells me to increase react time, but I dont get why #1 is ok, but #2 is so bad and not getting any better. I sure appreciate all the helpful info and suggestions though.

Thanks,  Laurie

You have enought alkanility. It looks, as Terry suggested, either the #2 SBR gets more organic matter or it gets less oxygen. If you read the electrical meter, read the numbers from right to left, so you know if it is pass or before the next digit (hard to explain), this will tell you the # of hours the blower ran. It will not tell you how many cubic feet of air was discharged.

Check the discharge and suction pressure on the blowers under same working conditions. Check the air filters on the blowers. You may want to have someone check the amp. draw on both blower under the same working conditions (same water depth in both SBR's). I would also drop the MLSS in #2, see if the oxygen level increases, and increase the aeration period, as long as possible.

Wastewater treatment is often diffucult to explain (art/science), so don't worry why one reactor works better than the other.

Good Luck

Bob

Bob Whitworth

I will try your suggestions, with some help from the maintenance operator. I did raise the waste on #2, I was talking to another SBR operator from another town, she told me not to worry about wasting "out" the bugs, that they will come back around after adapting to the new conditions. I am happy to say that the changes I made to the cycles today have produced a longer react time, (50-60mins), and averaging about 100 to 115mins on aeration fill time. I hope this will raise my D.O. level up to a 2.0 by the end of the react cycle. If this doesnt work over the week-end, I may have to take the basin down to check my diffusers. If you have any more suggestions, please let me know, I feel real lost right now!

Thanks so Much,

Laurie

I agree with Bob. Check the blower inlet and discharge pressures. But also record the depth of the basins at the particular time because the discharge pressure will vary with depth. Try to compare the discharge pressures between the two basins at the same depth. If you have fine bubble diffussers (in particular) you could have fouling which is affectting the efficiency. Other diffussers could be affectted as well but fine bubbles are particularly bad.

From your description i am assumming that you have a blower for each basin with no DO control on the blowers and your "control" DO by time only or do you have a number of blowers with more blowers bought online at different parts of the cycle?

Do you operate on 4 , six hourly cycles per day per basin , with a fixed start time for each cycle or does the start time float based on volume , because this will have a bearing on what the loading is doing between the two basins?

I assume that when you say your micro looks bad you are saying there is little free swimming activity , no stalked cilitiates , amoebas etc. SBRs tend to favour certain types of protozoa but if you are seeing no activity this is likely to be a sign of low or poor DO. The type of protozoa you see will also depend on your SRT.

If you can do the following:

1) Increase your aerated times to increase the amount of oxygen supplied.

2) Increase your SRT a little at least.

3) Check your blowers etc as Bob and i have suggested.

4) Monitor the end of aeration ammonias with the decants.

It may take a week or two or more to fully recover but i would suspect that if you can the get on top of these items you will see some improvement relatively quickly.

Let me know about your blower and cycle configuration as above.

Regards

TerryF

I do only have one blower per basin and no way to increase the blowers output, (on & off only), the other problem I have is that both blowers share a common air line, therefore I find that if I increase my Aeration fill time, I will have one basin in Aer fill while the other basin is in react, and the basin that is in react is doing nothing (sitting still) because the basin that is in aer fill is taking all the air because it is at a lower level. So, I have had to increase my anoxic time to leave enough time for the react cycle to finish and go into settle. If that makes any sense. So I am basically confined to giving the basins the air they need in the react cycle. As for the the other question, I do operate on 4, 6hr cycles. My system is toltally flow proportional, with no controls to operate at a specific time, therefore the basins are constantly switching from peak flows to low flows. Also, I only have a psi guage on the discharge side of the blower, none on the intake side.

I also have a dumb question, the NH3 is produced by the microbes in the sludge blanket, therefore if I increase my waste time in that basin, shouldnt I be decreasing the ammonia levels just by decreasing the sludge(mlss) ? Or is it the other way around? I am totally new to a SBR plant, I'm more of a lab tech than an operator, but because I hold a WW liscense, I got thrown into this position, when the previous operator left.

Thanks, Laurie

Don't sweat it too much if things are not going well for you. I have seen some really good operators get into trouble with SBRs. They are not necessarily that difficult(although some are) but they sometimes challenge the conventional thought. But if they are not designed properly they will give you untold grief. Unfortunately many are not designed correctly and so you have to try to do the best you can with what you have.

With regards to the NH4 and the sludge blanket you need to waste less to have more nitrifiers to convert the ammonia to nitrate. If you waste too much it is possible to end up with no ammonia treatment capacity at all because the nitrifying bacteria are slow growing. If wasting at a rate where you turn over all the sludge in less than the time it takes for the nitrifiers to grow than you end up with no nitrifiers. You probably need to have an SRT , (solids retention time) of at least 15 days given your set up but probably longer and depending on the water temperature.

With regards to the pressure gauges we will have to make do with what you have. Try to get a reading on them when the blower is  running and the basin are at the same level. For example when #1 is aerating during react and the water level is say 10 foot or 3.3 metres read the pressure gauge on the # 1 blower. Next time #2 basin is aerating try to get a reading when it is approximately the same level. If both blowers are performing the same and the aeration is performing the same the pressure will be about the same. As a rough rule of thumb for every 3 foot of water over your diffussers you should have about 1.4 psi blower pressure (or 1 metre for 10kpa if you prefer metric). If your numbers are well outside of this you have a problem , somewhere between a broken gauge , fouled diffussers or a worn out blower.

I understand the issue with the anoxic stage and the problem with timing for settle etc but I don't understand the blower configuration that has a blower for each basin yet they share a common air line. Normally you either have completely independant blowers for each basin or you have a common bank and you direct air to different basins with air valves.Is it possible to run two blowers together into basin 2 for a while to see what it does to the DO provided this does not exceed the maximum airflow rate for your aeration system?

Are you able to tell me the following info?

Average BOD or COD.

Average NH4 levels.

Quantity treated per day.

The depth of your tanks.

The type of diffussers. Coarse bubble or fine bubble.

What the capacity of you blower is ? What is on the name plate of the blowers and the motor driving them.

I can do some rough calculations for you to see how it all should work. Send me an email if you prefer.

Regards

TerryF