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Anonymous Poster #1

Activated Sludge Process

06/23/2013 3:11 PM

any one help me for in actvated sludge process will afffect the higher TDS .presently the following parameters affcted in process li DISSOLVED OXYGEN always lessthan 1 mg/l,cod & bod reduction is very less tss in secondry outlet is very in aeration tank present inlet tds is 20000ppm,cod 1800ppm,tss 700ppm after secodry cod 550ppm,tss 600ppm, what are pollution will affect the activated sludge process

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#2

Re: Activated Sludge Process

06/23/2013 5:54 PM

Different polutions can affect the process in different ways.

We've had a plant "killed" three times in the last seven years.

First time was a bulk spill of "anti bacterial hand wash" in a workshop where the spill material was dumped into the sewer.

Second time was a food processor dumped 20,000L of concentrated juice (pineapple) into the sewer and overloaded the ability of the system. (They were batter coating the pineapple rings and the juice was only a transport media in their case.)

The third one is still a mystery, but is suspected to be some illegal dumping of solvents, either by a local painter of car workshop.

We've also heard of issues with petrochemical waste (oils) and pesticides casuing problems but so far it seems that our systems have been large enough to cope with those.

If your tss is still high after the clarifier, then it sounds like the upflow velocity is too high for the floc settling rate, or there is turbulence in the tanks.

You might have a capacity problem, where the system is just unable to cope witht he total materials to be processed.

Also, I know that we "imported" some bugs from another system with a higher metabolic rate to improve the output from one of our plants that was underperforming.

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#3

Re: Activated Sludge Process

06/23/2013 8:18 PM

years ago I did a fair amount of work in water and sewage treatment plants so I will throw in my 2 cents. it sounds as if you're performing some of the right tests but I question the frequency as you're moving through your system. you should never get to point where you're moving sludge or water to another tank or processing area without knowing if by adding it you'll damage the condition of the current contents of your tank. it really doesn't matter pollutant (to use your term) is present . as Just an Engineer points out several things will kill off your bugs. if you're doing adequate testing as you move through your system you should never introduce a batch of "polluted stuff" and kill off your good bugs. I'd confirm your testing procedures and their frequency. any of a million type of spills has the potential to be toxic to your good bugs.

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#4

Re: Activated Sludge Process

06/23/2013 8:29 PM

Well,

I guess I don't know crap.

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#5

Re: Activated Sludge Process

06/24/2013 11:28 AM

Values out of secondary are 3x values normally going into normal secondary of activated plant. Values going into system is pure energy and should be evaluated as such and not burned/oxidized off (recycled?). [assume the tds does not represent salt as such high value would kill organisims and that no matter how much O2, it appears to be used up]

This is not normal collected sewage and is from one source. If it can't be recycled, try adding 30% more O2. This may require changing all difussers to fine bubbling system depending on existing system perameters such as hydralic retention and peak flows.

It would be nice to know N values and if nitrification is desired [more O2 needed and anaerobic stage?]

What are you doing with primary and secondary sludge?

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#6

Re: Activated Sludge Process

06/24/2013 7:33 PM

First of all you need 1.5 pounds of oxygen per pound of BOD. BOD is about half of COD. Secondly you need 4.6 pounds of oxygen per pound of NH3-N, ammonia nitrogen. A good primary settling tank should be able to reduce your TSS by 50%. A good final settling tank should be able to reduce your TSS by 45%. By the way TDS, total dissolved solids are not the same as TSS, total suspended solids. If you are only achieving 1 mg/l in the aeration tank you don't have enough air. Minimum aeration in the bioreactor is 2 mg/l. If you truely have high TDS there isn't anything you can do about it unless it is something organic. TDS will not settle out in the clarifiers. You can also increase the recirculation rate of the activated sludge from the final clarifiers to the bioreactor. Turn up the air supply.

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#7

Re: Activated Sludge Process

06/24/2013 8:09 PM

I gave GAs to Just an engineer, Frediski, and JME761. I would have given one to Lyn but he doesn't know crap. There are lots of things to upset an aeration tank and the DO is too low to be effective in producing activation. Where is the receiving stream or discharge and what requirements must be maintained? You may want to augment the air with direct chemical injection of hydrogen peroxide at 35% until you can get the levels up and identify the sources of upsets. Does the tank actually smell septic, rotten eggs? Do you notice bubbles in clarifying tank, possible N2? Check for bulking and inspect with a microscope. Iron can impart a very high COD so iron bacteria may be an issue. Who are the heavy users that may be potential contributors, Dairy? Sewer use bylaws should be enforced or established.

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#8

Re: Activated Sludge Process

06/24/2013 11:28 PM

There is another small portion of the anonymous OP's question that begs a response and that is the TDS that is reported.

Since they are by definition "disolved", then the settling and agitation processes will not reduce them unless they are consumed by the bugs in the system.

The other means to reduce disolved solids is to specifically precipitate them from the solution, either by pH change or by chemical addition.

If the source material for the facility is relatively consistent, then it might be beneficial to investigate a chemical solution to the issue.

If as someone has already said it is saltwater, then the system need specific on site review.

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#9

Re: Activated Sludge Process

06/26/2013 8:20 AM

IMO, there's a huge lack of valuable information presented to effectively render any answer.

First thing I'm asking is: are the test results based on "grab" samples, or "composite" samples.

We know next to nothing about the system. In the head works, is there grease and oil separation? Is there primary clarification? Is there a flow equalization tank? What is the F/M ratio in the activated sludge tanks? What type of aeration diffusers are being employed? Is the aeration rate sufficient? Complete mix or sequential or batch activated sludge? What is the sludge return rate from the secondary clarifier's? Are you employing de-foaming agents?

I could go on and on......just saying.

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#10
In reply to #9

Re: Activated Sludge Process

06/26/2013 10:54 PM

every gram of information helps solve a problem. we can tell the system is stable and not upset by the ratio of treatment taking place. grease/oil are not interfering with treatment or sand bed would be plugged. High solids will mute any foaming. To get level of existing treatment, course or intermediated bubblers whould shear bugs from food. Therefore, O2 and hydrolic time are lacking. With a batch reactor these peramiters could be ajusted. We can also tell that return rate from clairifiers is less than 15% because influent is equel to normal sludge blanket. Any greater return rate would see sludge blanket and % influent be expelled.

Yes, if there was primary settling or equilization tanks, then there exists posibility of re-piping to achieve greater active O2 treatment.

Further we can surmise that pollutent sourse is near (short flow time) as solids would go septic and interfere with treatment ratio.

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