Hi everybody
Our ETP is treating  effluent from 2 macines manufacturing coated paper. Other details are follows.
1)Daily flow-9600 M3
2)MLSS-6700 PPM
3)Aeration tank-2 compartments (vol. of each is 11200 M3)
4)BOD to aeration tank-200 PPM
Here I have one question-For the purpose of energy conservation we have kept only one tank in service,but then treated effluent quality affected badly. We have tertiary clarifier too.The aeration tank which was in service was running with 2 bubble technology aerators,while 6 were surface aerators.Still we are not getting good quality of treated effluent. When 2 aeration tanks were in service the quality was very fine.
Do somebody suggest me -What we should do to get fine treated effluent quality with only one aeration tank in service.

Regards

A.V.Bhide

Mr. Grunn
D.O. of the aeration tank is  around 1.7 PPM



Regards

A.V.Bhide

Hi
If your plant was operating satisfactorily with two aeration tanks in service, and you wish to change to one tank operation then you need to maintain the dissolved oxygen level as before and double the MLSS concentration in the one tank so that the sludge mass in the aeration system is effectively maintained at a constant value.

This will only work if the MLSS in both tanks was the same, but can be made effective so long as the sludge mass in the one operating tank is the same as the sludge mass in the two tanks when they were operating.

I agree with all the above posts, but if mixing is the problem (which it probably isn't, it's probably Grruns assumption) but surface conventional surface aerators sometimes have trouble properly mixing.

Have you seen or heard of the Aeromix Tornado aerator?
http://www.aeromix.com/tornado.php
We've used them before in the past and they worked very well for our pond mixing & aeration. The one issue they have is a submerged bearing that had gone out once or twice but that issue was fixed by getting the Fuchs Oxystar
http://www.fuchs-germany.com/en/wastewater/products/aerators/oxystar-aerator/

Both spiral aerators are good, the fuchs is a little bit better designed though.

PS. I am not affiliated with either company

Advait,

The timeline is not clear...For example did you use 2 tanks successfully, then 1 tank successfully for some time then things changed for the worse, or did you instantly notice a decline in effluent quality upon shutting down the other tank?

We have no idea what kind of diffusers you have or whether the system is properly sized, so others have already asked you about D.O.   Your system may be designed with an aeration system in one tank capable of providing oxygen mass transfer for only half of your daily flow if it was designed to run with 2 tanks.

Even if it was designed to run in a single tank, you may have experienced some diffuser fouling. Coated paper wastewater is known to leave calcium residue on diffuser membranes and in the slits, so your mass transfer efficiency may be severely compromised, even if you have an excellent quality diffuser, which may or may not be the case.
Perhaps your aeration piping system cannot handle the extra airflow and is distributing unevenly.  

Good luck.

-Tom

All of these comments could be accurate, or else it simply is that in order for your plant to actually be "extended" aeration treatment of the wasteload you must have two tanks in service.  If you are not providing long enough retention time in your system, then treatemtn does not get completed to the extent that it did with two tanks online.

~Eric