andrea,
I'd like to know if the inflow is domestic sewage.  The nutrient concentrations seem very low for raw sewage.  You may have problems with a nutrient deficient  plant, this can lead to high SVI.  Typically about 2mg/L of P is used in the process to grow new cells.  Starting out with only 2.12mg/L P may mean the process is nutrient limited.  Can you provide information on the effluent N & P values? You may need to dose phosphoric acid and even oxidizable nitrogen to provide sufficient nutrients.

Can you confrm the DO for the whole 24 hour cycle too?  Are you sure the DO is around 2 mg/L through the entire body of the mixed liquor?  I believe the shorter the sludge age the higher the DO should be. Do an Oxygen Uptake Rate test to confirm that you are satisfying the needs of the bugs..  

I associate microthrix parv.  with long sludge ages, not used to seeing a plant with an SRT of 2 days so I can't comment at this stage.  I'll look up your problem in my favourite book on activated sludge when I get back to work tomorrow.

Cheers

Geoff

The Chlorine dose that you added was way too low and would have been 'mopped up' by the BOD/COD and other constituents within the wastewater.

To get an effective 'kill' on the filaments you need to dose between 5-20gCl per kg MLSS (Chlorine and not Hypo).  Yes it does seem high but this will come from trial and error.

I agree that by adding Chlorine compounds you are only treating the symptoms and you must identify the causes of your bulking.

On your plant:

MLSS of 720 mg/l is too low.  This has a number of implications:
1)  sludge age is always going to be low,
2)  settlement will be poor,
3)  low sludge age will result in not enough HRT to allow for a divese colony of bugs within plant i.e. no rotifers, etc,
5)  low sludge age means that your plant will not nitrify (this may not be a problem) but you will also be in the growth phase meaning that you will have a high sludge yield.

The first thing I would do is get a good book on wastewater process engineering - Metcalf and Eddy will provide all the basics.  At the same time do not waste sludge and try and build up your MLSS to between 2,500-3000 mg/l and get your sludge age to something normal e.g. 5-7 days - 2 days is way too low!!

I would also do a search within these pages for some excellent advice on bulking and bugs in general by Victor Santa Cruz.

I want to highlight that at SRT of 2 days, nitrifiers can not develop because they are known to be slow growing bacteria and hence effluent NH4-N conc may be same as influent. However, P removal would be very high because all the assimilated phosphorus is removed by wastage. Check also P content of sludges. It may be 2-4%.
 But all this facts contradicts poor settling, as nitrifying sludge has poor settleability which is not the case here.Try to keep SRT of 5-7 days and build up MLSS to 3000 mg/l, that may help

To ENVIROTIC:

All the flocs settle slow. I've been noticed that in the settling cylinder total flocs mass appear like wet cotton, the upper interface (very thin) beeing clear. On microscope the flocs are small, irregular and rare because they are spread by filaments bridging. Today we found flocs in effluent too. I am agree: sludge age and MLSS should be increased.

To APPY:

I know that nitrifiers and denitrifiers need 22-30 days to reduce N compounds with 100%. Nitrifiers and denitrifiers are very sensitive microorganisms. Anyway I think that for us the more acute problem now is to balance the system and with good MLSS, good sludge age and good DO we could try to do some nitrification. Sometimes P content is higher in effluent than in influent. I'll check also P content of sludge.
I'm sure it isn't a poor settling because of nitrification.

You can get quite remarkable improvements by adding an iron source (and some trace metals) to the incoming effluent.

If you can send me a sample of your biomass I can get it checked for iron levels in the bacteria. A level of 1500mg/kg dry matter is usually considered the minimum for good biomass health.

Both the sludge age and MLSS seem low also.

Contact me for the address to send samples.

Alistair

Hi

We have a similar problem, we operate on industrial wastewater, BOD fluctuates greatly (dependig on process needs) but average is 903mg/L, our difusers were not working properly so our OD was way down, 0.5 mg/L, today we have replaced them with small bubble difussers and got up to 4 mg/L, BUT we have a severe (I think so because is my first experience maybe?) problem with filamentous organisms, I dont know enough to identify them but, observing with a light microscope, we found in a single plate (I did not count them) well over a 100 and just a few other life forms, rotifers and some free swiming ciliates, mostly. No floc is observed or maybe just pinfloc.
Our seteable test shows NO sedimentation after 60 minutes (maybe 1 or 2%) and no nitrification, (we observe no bubbles)

Can you give me some recomendatios on how to proceed?
For your help, THANKS

It sounds like your plant is pretty messed up.

You mentioned you don't waste, then your solids should be growing unless your plant is essentially dead.

You may have to reseed to kickstart your plant...Rotifers and waterbears are important contributors to a stable activated sludge plant

Are your aeration basins straight lined or snaked? I'd like to see the DO's at the inlets and outlets for each basin.

What's your volatile solids %?

Jeff

Hello I am sorry I could not answer any sooner…

Hola Víctor, nice to hear from you again.

Thank you for your response, I will try to fill the information:

We operate an Activated sludge plant, it works like this:
Equalizer tank
Trickling filter
Activated sludge
Clarifier

We operate on industrial waters from the carbonated beverage industry.

On the “other side” we have a sludge thickening process

One of the main problems is that the plant has no means, as today we are working on it, to measure flow (between tanks) but we know the overall flow it is in average 868 m3/day, it has operated with very high changes max was 1,616 m3/Day wit a minimum of 82 m3/Day (this are real figures and the flow changes that much, some times from one day to the next.
BOD also presents variations:
BOD      Influent mg/L      Effluent mg/L
Average      865            27.81
Max      1,552            82
Min      260            6.6

SST      Influent mg/L      Efluent mg/L
Average      53.45            23.4
Max      199            113
Min      9            4

Influent pH
Average      Max      Min      Frecuent
9.77827031      13.275      6.25      9

Sludge age is not calculated, last time I check (the aeration basin) all I could see was rotifers, some ciliates and lots and lots of Filamentous (they do not look branched but I am in the process of learning) in the absence of data I can not calculate sludge age.

Regarding nutrient deficiency at the time we calculate Nitrogen and Phosphorus needs using BOD as the basic parameter and “Fertilizer” is added to adjust to 100:50:1 (I would not be so confident we do not have nutrients deficiency problem).

Unlucky for me I can not send a sample, but I will try.

Hi JeffB

Thanks for you message,

At the moment we have our filter damaged (to much work) we were extracting an average of  6 m3/day,
I am not sure the plant is not dead, we are trying to “re seed” from the sludge thickening tank, we see a much better colony there (rotifers, swimming ciliates, stalked ciliates, nematodes and of course lots filamentous)

Our aeration basin (is only one) is straight line, entering from one side and leaving from a lateral side (I am proposing to create a snake flow)
At the moment we do not perform any VS test, we are checking solids with an interferometer so the data is above as SST…?

There is no blanket in the clarifier, or should I say the blanket is as thick as the clarifier itself, our sludge (from a settleability tests, performed with a one liter sample in an Imhoff cone) presents 1% after 2 hours!!! with no nitrification (no bubbles)

Our OD meter is out of order (again) but last measurement was over 2 mg/L

For your help and comments Thank You

I am concerned with (how to get rid of filamentous), at the moment I have proposed to work based on a constant solids strategy, using averages I have come with a figure of
           DBO Kg/Dia      Kg MLVSS            1222.64            Aeration Basin
Relacion F:M      0.5            2445.28      Kg
           0.25            4890.56      Kg
(what do you guys think)

Willy

Dear Willy,

I am not sure that I could read your pH values correctly.

average 9.778... (it is nonsense to give the pH value with this 'precision' - what is the precision of your pH meter?).

max 13, min 6, frequent 9

This would mean you have to neutralize it. The high pH is obviously due to bottle cleaning. If they would install a buffer tank they would be able to discharge the high pH effluent in low amounts continously instead of discharging it periodically. Even better if the would replace the cleaner by a neutral cleaner or a less alkaline one. From the max value it seams that they drain concentrated caustic soda!

Kind regards
T. Sobisch

with no nitrification (no bubbles)


Just a little clarification, you are not going to get bubbles with nitrification, you get the bubbles with denitrification

nitrification: ammonia -> nitrite -> nitrate

denitrification: nitrate -> nitrite  ^N₂

There was also mention of cleaning products in the waste flow...

possibly took a toxic hit on the system? Maybe need to waste a lot and then reseed? (or find the source.)

If you are still getting something toxic, the plant will never come back until you stop the source. I take it your discharger does not have a source control program in place...

Estimado Arquitecto Figueroa:

If you plant is hit with a toxic load the following probable operational parameters will be a sign.  Since it is a toxic shock to the organisms, you will have a definitive effect to your BOD removal (this is difficult to ascertain as you look at the variability of the BOD loading to the plant).  If you are nitrifying, your ability to oxidize ammonia to nitrite and nitrate will be greatly affected (nitrifiers/denitrifiers are slow growing organisms and are not very tolerant of toxic substances).  Secondly, you will have increased turbidity due to the deterioration of the floc and a dramatic increase in single celled bacteria.  This increase in single celled bacteria will greatly augment the number of flagellated organisms.  Other higher level organisms will decrease in number such as stalked ciliates, rotifers and water bears since they are more susceptible to toxic compounds.  Thirdly, and this is from numerous cases I've seen, solids drop like a rock but you are left with a very turbid supernatant and this is due to the increase in singled celled bacteria and breakdown of the floc to almost pin-floccing.  From your previous posts, it appears that the majority of these traits are not present and therefore are not suffering from a toxic shock to the system.  Your equalization basin is not doing what it was built for or at least you are not taking advantage of equalizing flow and concentration of BOD as well as minimizing the effects of pH variability.  It is very difficult to determine the nature of your system's stability and this is mostly due to the nature of your plant and inability to equalize the flow.  

As far a nitrification, denitrification, what are your permit allowances as far as what the plant discharges?  Do you have Nitrogen limitations (NH3-N, NO2-N, NO3-N)?

I'll comment some more later.

Estimado Arquitecto Figueroa:

I hope I understand fully about your comment "our equalization tank was used at its lowest possible level."  Are you saying that the equalizatio tank is not being completely utilized? If it is not, is it because you have no control of flow or have no control from a production point?

Hi Victor

We have not control from a production point of view, the plant will manufacture what the market demands, and if they need to wash a lot of bottles, They will!!! But I think we can manage the amount of effluent pumped to the aeration tank, as two weeks ago we started using it at its full capacity (minus average production and allowing for peak discharges-it can hold 2,174 m3) and are pumping around 900 m3/day to our aeration tank, our flow control is kind of crude (pumps do not allow for changes in speed or capacity and we do not have smaller pumps or alternative ones) so its on-off.

Hi Sobich

We are implementing a pH control in a pumping station, before the equalization tank, I will check if we can change the cleansing agent but it may not be possible based on cost considerations (nothing new here). Could you recommend one we could check for price and cleasing operations??


Thank you both for your valuable time and interest in our problem, we are making progress, slowly but.....

Best regards
Willy

Dear Willy,

I can only recommend to search the local or nearby suppliers or manufacturers of industrial (glas) cleaners.

Wishing success.

Kind regards
T. Sobisch

Has anyone worked with AQ 9400 or AQ 9450 from Jenfitch.  We (Jenchem) ran this product at Stallion Spring CSD (near Bakersfield, CA).  They were experiencing floc carryover in their secondary clarifers.  The sludge blanket was over 8 ft and the chlorine contact basin had a floc build up.  The DO was 0.5 mg/l and the daily average flow rate was 90,000 gpd.  The plant manager was preparing to go off line vs violate.  The effluent turbidity was going over 4.0 NTU.  In the past, when these conditions occurred, the plant manager would add 300 gallons per day of sodium hypochlorite for 3-5 days and get a load of solids from the nearby wastewater plant.

This time they tried 2 gallons of AQ 9450 into the RAS line (25 mg/l) for 12 hours.  Next day, the sludge blanket was less than 4 ft.  The chlorine contact basin starting clearing up and the effluent turbidity was less than 2 NTU. The DO was now up to 2.5 mg/l. On the second, they fed 1 gal or 12 mg/l of AQ 9450.  Under the microscope, life was returning to the clarifier.  

Two weeks later, they added another gallon of AQ 9450 (12.5 mg/l) when the sludge blanket started to go pass 5ft.

Interesting technology?  Has anyone else used this product made by Jenfitch (925-305-7880) based out of San Francisco, CA?  

We did try hydrogen peroxide but that was a little too hazardous for the plant manager. We also tried to increase run time for the blowers but that only made settling in the clarifier worst.