Hi, I just came on site at a waste water plant, they have had high TSS for almost a year in their effluent.

The plant is in northern Alberta, it takes care of waste-water exclusively for dorms and kitchens.

The operator before claims the problem started when the camp changed detergents. but the camp has gone almost detergent free for quite a while now.

The limits are 25mg/L for both BOD and TSS, this is our only limit other than flow

Some figures for the month of July
            Mean        Min         Max
Influent   61m3       35m3      61m3
BOD       489mg/L   323mg/L  772mg/L
TSS        404mg/L   184mg/L 1000mg/L

Influent pH 7.3
Aeration pH 5.1
Effluent pH 6.5

We have been adding some soda ash, but we don't have that much left, my manager, (less experience than I do) feels that soda ash adds TSS.

Settling 10%
MLSS 2600mg/L

About two weeks ago, it was working fairly well, my manager wasted quite a bit, he brought the MLSS down quite a bit, because of the foam on the aeration tank. He feels we need to waste the "old bad" bacteria.

Well now he's gone, and we haven't wasted in over a week now. But it doesn't seem to be getting better. Our field TSS for today was as high as 60mg/L though the only way to test it here is using the Hach DR-890. and that is usually about twice as high as the lab results. So we are about 30mg/L.

Any suggestions would help

mrbouf,
A few quick observations:

• aeration pH (5.1) indicates a lack of alkalinity -such a low pH will kill many of the viable bacteria.  I assume you are trying to nitrify?
• soda ash doesn't add to TSS - its job is to maintain an environment for the bacteria to sustain growth.
• you only get rid of "bad bacteria" by slowly increasing wasting and being patient
• you need to keep the aeration pH ideally above 7.0 - best way to see if you are doing OK is to measure effluent alkalinity - it should be above 50mg/L.  Above 70mg/L is even better.
• You need to calculate your sludge age.

One issue you will want to address is consistency. I assume you are working some sort of rotation as you are in the Ft. Mac area. Wasting quite a bit for 2 weeks and not wasting anything for another week is just going to set the plant back.

Judging by the pictures, your sludge age is fairly high. Your system needs time to stabilize and adjust to the change in wasting, which needs to be consistent. Get your manager on the same page, try one adjustment and give it time to stabilize.

In the meantime, do you have any sort of polishing unit post-clarifier you can remove TSS with? Have you checked all the mechanical components (RAS pumps come to mind) to ensure they are all functioning properly?

BTW, are those BOD/TSS figures of the final effluent?

ParadoxWater wrote on Aug 4^th, 2011, 1:45pm:


Those are influent

Effluent yo-yo's between around 25 to as high as 100 sometimes, (though the really high peaks don't seem too long)

You state that nitrification is not required, so take process control steps to eliminate it from happening.  Do not allow your MLSS to become too high and do not run a high SRT for these will stimulate nitrification.  

Slowly increase your wasting rate to lower your MLSS concentration down to around 2000 mg/l.  Allow it to remain at that level for a few days to see if effluent numbers begin to improve.  If necessary, reduce the MLSS through wasting an increased amount of no more than 10% more than before.  Get your MLSS down to around 1500 mg/l and check to see if your effluent numbers have improved isgnificantly.  You simply need to systematically search for your ideal operating parameters.  Short term remedy for the low pH in aeration is chemical addition to raise it up close to 7.0 and to increase alkalinity for it most likely is too low.  

Do you measure sludge blanket depths in your clarifier/s?  Holding too much sludge there can allow solids to hydraulically leave over its weirs which can be your source of BOD and TSS.  Hope any of this helps direct you in the right direction to solve your problems.

~Eric

Looks like you are operating with a F:M around 0.13 and a solids inventory of 226 kg.

Assuming your RAS concentration is 2x the MLSS concentration (based on your flows and MLSS), wasting 2.5 m3/d should hold you steady. As Raj said, your desired MLSS may be in the 1500-2000 mg/L range, wasting 4.0 m3/d over two weeks should get you down there.

As mentioned by others, you are "flying blind" in certain aspects of the system and should make any changes gradually. Let us know how it goes.

Red worms and rotifers with no free swimmers indicates an old sludge.  It is going towards past prime condition.  As mentioned previously, you ought to get the MLSS down below 2000 mg/l in order to return the bugs into their optimum growth zone.

~Eric

mrbouf:

Your low pH is probably the cause for the long-term high effluent TSS. You really need to keep the pH at 7.0 or above. It is a common obervation that removing detergents reduces alkalinity and can cause this problem. Part of "pollution" prevention...

The red worms are tubiflex worms. These indicate old, septic sludge deposits. You may need to increase mixing and also check the final clarifier for sludge deposits.

Hope that this helps.

increasing the MLSS when the loading rate increases is a good idea. If you know when this is coming you can gradually bring it up before the event.

Glad everything is working good, but be cautious of relying on protozoa/ metazoa under the microscope for process control. These change quickly depending on the amount of dispersed bacteria (which most of them eat) and only make up roughly 5% of the biomass. Identifying filaments present, floc size, floc characteristics, other bacteria present gives you a much better idea of what's going on. These take much longer to change.

As for the membrane plant (MBR?) these are a bit of a different animal since the MLSS is typically run so high. The foam needs to be analyzed under the scope to see what it is (filaments, polyscharide, surfactant etc?). I help consult one that runs best on an unbelieveably long sludge age. We promote a high degree of endogeny so we don't have to waste as much. We need to know the cause of the foaming before a control strategy can be offered.

mrbouf:

You really need to have the foam looked at microscopically and diagnosed properly. It could be grease and oil or other surfactabt; or it could be a filament foam like M. parvicella or Nocardia.

Hope that this helps.

mrbouf:

It takes some experience and practice to do this. I suggest that you have someone with this expertise do it for you now (you need this analysis now).  You can learn how to do this by taking a class or getting the book: Manual on the Causes and Control of Activated Sludge Bulking, Foaming and Other Solids Separation Problems, D. Jenkins, M. Richard and G. Daigger, 3rd ed.

Hope that this helps.