Hi Experts
Could you help me Please?
I want to start up a conventional activated sludge treatment plant for municipal wastewater and have some problems as followings:
1- I filled tanks with water but I don`t know how much activated or return sludge (from another plant) I should add to it. then, is it ok if I fill whole the aeration tank or just part of it to add the active sludge?
2- How much flow should enter to system for the first day? should I divide it into portions?(for example at first 40% after some days 70% and then 100%) what portions you suggest?After how many days?
Q design=55000 m3/d , Mlss design=3750 mg/l, BOD5 inlet = 220 mg/l, COD5 inlet=440 mg/l, SS inlet= 270 mg/l
there is 3 aeration Tank 44*22*4.5 m,
I would be so thankful
Best Regards
Ashoori

You ask some simple questions but the answers are just a wee bit long but here goes.......

Some maths; here each lane is 44*22*4.5 m and target MLSS is 3750mg/l.

So at full design the mass of MLSS in the aeration is

44000*22000*4500 x .003750 = 16.335t solids with 3 lanes you'll have 49t

Say you have a tanker 25m3 and the seed sludge has 7000mg/l (taken from the RAS or SAS line from another plant) then it will have 25000 x .007 = 1.750t, so you would need 28 tankers.

Now that would be the ultimate delivery, and may be untenable from other plants due them being smaller and you would in effect "suck" the life out of them.  

The seed sludge should come from a similar type of plant, and prior to any uplift you should check the biology of that plant to ensure you don't bring any thing undesirable into your plant, e.g. a plant with loads of filament problems would be best avoided.

Also seed sludge soon dies once you start transporting it as it needs air to survive.  I would heitate if the transportation was over 2 hours.  No point bringing in dead sludge to your new plant!  Introduce the seed directly into the aeration lane.  If you put it into the front end of the plant then expect to lose some as it settles in the primary tanks, which is not good!

Other things to think at start up is that when using seed sludge it does take time to acclimatise to the new "feeding" regime.  The bugs have had a happy life feeding in the donor plant.  When they go into the new plant they need time as the incoming effluent will be somewhat different and the bugs will need some time to acclimatize and the biology might change a wee bit over the resulting days.

What would I do?  Self seeding is one route and one I have used but only when there has been no seed readily available.  In my area transportation can be a problem.  If you go down this route, temperature will play its part with a slower biomass build up if it is cool/cold autumn/winter time.  Summer time is best as the bugs will multiply quicker due to the higher influent temperatures.  Times to build up the biomass will be measured in weeks.

If you are like the rest of us and have tight time deadlines to meet then seed sludge is what you want.  What I would suggest is work on one lane at a time.  Isolate the other two and bring in seed to just one.  Get the flows from the plant going through this lane.  Build the biomass in here and go for say 5000mg/l, then bring the second lane on line.  Use the biomass from this as your seed and you will have perfectly acclimatized bugs to your plant, so no issues here with bringing in undesirable biology from outside plants.

I would bring in some tanker loads (though not all the required amount) and monitor the MLSS over the coming days as it builds up.  If it isn't going as fast as you want bring in some more.  No rules here just suck it and see!

Start up is always exciting and worrying at the same time.  I will take it as granted that all structures, plant, control systems have been fully tested and fully operational.  

When introducing the effluent for the first time I always ensure the tanks are full of water.  I will have the RAS pumps on.  You may minimise introducing the effluent over the day light hours (8am - 4pm) so you can monitor the plant.  There are no rules here but in general most folk are on site during the day, so if something goes wrong you'll have the right folk to deal with it.

Monitor the primary tanks for sludge build up and when there is sufficient sludge in the bottom switch the desludge pumps/control system on.

DO NOT SWITCH ON THE SAS PUMPS UNTIL YOU HAVE BUILT UP SUFFICIENT BIOMASS TO MAINTAIN THE PLANT.  Before this read up on sludge age and start working to maintain the plant at the idea age.

Commissioning Guy has outlined some of the possible problems and solutions for your start-up. An operation of this size should have a laboratory to support operational decisions.

Do not be alarmed if a white billowy foam appears on the surface of the aeration tanks as this is due to the growth of "young"(new bacteria) sludge. This should disappear in a few days as the sludge grows older and the F/M ratio begins to stabilize.

What are the effluent requirements for the start-up and how long do you have before having to comply with enforcable discharge limitations? The effluent limits will probably dictate the sludge age that you will try to control to. Read the operating manual! Engineers will provide the operating conditions basis for their design.

I would suggest wasting a little sludge as soon as possible just to check out the sludge processing facilities. Sludge age affects the population distribution of the various micro-organisns in the activated sludge while MLSSs are only the total mass of the various organisms in the sludge. Microscopic analysis can provide a qualitative analysis of the sludge age.

Good Luck,

grrun

I agree to disagree with many of the other members on the subject of wasting right away at start up. It only prolongs the process. I wouldn't waste any sludge until you are approaching your target MLSS concentration- F/M ratio.

We don't know the type of plant/ expected incoming BOD but 0.2- 0.4 seems very reasonable for a plug flow conventional system.

Follow the engineers advice, but remember there is a biology aspect involved too (something engineers tend to forget about!) That's why the microscope is critical.