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Operational problems with sewage treatment plant

Dear Sirs

 

                    I am working as a STP & WTP Supervisor in the British Aerospace Engineering compound (RESIDENCE) here we supply the potable usage water, After usage of potable water it return back to sewage treatment plant through several lifting stations

in this we dont have equalisation tank, from lifting station it directly pumped to distribution chamber and supply to 7 individual metal activation tanks attached with clarifiers after that clarified water goes to conduct tank from there we pumped through sand filters before sand filters we dosed sodium hypochlorite and SHMP. TOTAL SEWAGE TREATEMENT PLANT CAPACITY IS 980m3. In Activation tanks we maintained Dissolved oxygen 0.5- 2.5 mg/l, Some times in this process sudden upsets will happen like

1.Decomposing of bacterias and give bad smell overall area

2.Sludge comes up in clarifiers

Why it will happen???

Somebody give me suggestion the backwashing water from swimming pools have more chlorine so only it will happen like this they answer.

1.In raw sewage i cant check chlorine if i use the kits i cant find the result because of sewage have more turbidity.. Please give me a solution for this question?

 

The final treated water is used for Irrigation purposes.

1. In this TDS doesn't matter other feed parameters and outlet parameters please give me???

 

Then only i can check the efficiency of the plant,

Do you have any formulae, please give those in that case. 

Thanks

 

regards

 

E.M. Sheik mohamed

 

TamilNadu, India

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Comments

1.

Dear Sheikh Mohd.,

From lifting station it directly pumped to distribution chamber and supply to 7 individual metal activation tanks attached with clarifiers after that clarified water goes to conduct tank from there we pumped through sand filters before sand filters we dosed sodium hypochlorite and SHMP. TOTAL SEWAGE TREATEMENT PLANT CAPACITY IS 980m3. In Activation tanks we maintained Dissolved oxygen 0.5- 2.5 mg/l, Some times in this process sudden upsets will happen like

1.Decomposing of bacterias and give bad smell overall area
Ans: This happens owing to fluctuation in sewage residence time in the tanks. This can be overcome by adopting SBR (Sequential batch reactor) system OR MBBR (Moving bed bio-reactor) systems which are based on batch process OR fluctuating flow scheme respectively.

2.Sludge comes up in clarifiers. Why it will happen???
Ans: This happens because the sludge turns anaerobic and has not gone through sufficient digestion in the activation tanks. Since you also maintain D.O levels from 0.5 to 2.5 ppm, there is oxygen scavenging which is an ANOXIC process. Such sludges need to be properly digested or else, they turn anaerobic and float to top even when you are removing excess sludge regularly.

3.Somebody give me suggestion the backwashing water from swimming pools have more chlorine so only it will happen like this they answer.
Ans: This logic is incorrect. Chlorine kills bacteria, yes but sludge rising means anaerobic mass and BOD is related to organic matter in effluent and not bactrialconcentration.

4.In raw sewage i cant check chlorine if i use the kits i cant find the result because of sewage > have more turbidity.. Please give me a solution for this question?
Ans: To be honest, test kits have limited use for checking chlorine in raw sewage. Chlorine shall be exhausted anyway in it.

5.The final treated water is used for Irrigation purposes. In this TDS doesn't matter other feed parameters and outlet parameters???
Ans. TDS has limited potential since STP dies not reduce any TDS except marginally owing to process dynamics. For horticulture purpose, the USEPA specifies BOD <20mg/l, COD < 100mg/l, pH 6.5 to 8.0, TSS , 30mg/l and Oil and grease < 10mg/l.

6. Ten only i can check the efficiency of the plant, Are you have any formulas means give me that also???
Ans: Formulae are abstract, you may only take some thumb rules for plant operation. Since most parameters and processes are related to each other, it takes some time to calculate the same and all formulae will mean a lot of calculations.

regards

Taral Kumar
Akar Impex, New Delhi

2.

Dear E.M. Sheik Mohamed,

1.Sludge floats in Clarifier:

A.Bacteria in Sludge is getting dead because of
a. Use of Sodium hypochlorite a chemical disinfectant kills all micro organisms that are not desired.

b. You are treating sewage against nature's rule.

c. Treated water with Sodium Hypo chloride will affect fertility of soil and crops.

2. Odor:

A. Odor comes because undigested sludge which is not getting properly treated.

Generally sewage is treated with biological treatment as it is easily degradable. The sewage is digested with micro-organism either in aerobic or in anaerobic conditions. The treated sewage is used for secondary application like Gardening, Agriculture, Floor cleaning etc.

Advantages:

• The sewage thus treated is eco-friendly.
• The sewage is good for fertility of plants/crops.
• The sewage contents bacteria those are good for agriculture or Gardening.
• The sewage thus treated does not have stink smell.

You being attached with prestigious British Aerospace Engineering organisation(international standard), you should look for Bio-treatment of STP.
We can help you out for using Bio Products which can take care of your problems of bad smell and floating sludge in the clarifiers.
Our BioSol products are used in STP plants up to capacity of 2500 m3/d capacity for more than 2 years.

With Regards
Hiren Pancholi
hirpan@yahoo.com

3. Greenish colour of treated sewage water

Dear Sir

We are facing problem of greenish water in the output of sewage treatment plant. Initially when we commissioned the plant, there was no problem but, since the time we started using green colour sanitizing chemical in the washrooms, such problem has started occurring and the biomass in the MBBR reactor is also finished.

Do you know the reason for the greenish colour of the water. Can anybody advice me about the root cause and its possible remedial action.

Regards
S. Kumar

4. Greenish sanitizers must not create problem in the MBBR

Dear Mr. Kumar,

The greenish sanitizers you use may be biocidal in nature but in my opinion it must not create problem in the MBBR because the percentage of it would be very less. The biomass being affected in an STP is a common problem and I don't think it has got anything to do with the sanitisers. It is because the plant is not being run properly. Try the following:

  •     Recirculate 10-20% sludge from final clarifer to the aeration chamber always.
  •     Add molasses /sugar @ 50 PPM for a period of 3 days in the aeration chamber.

The green colour is due to algal formation due to excess nitrogen and/or phosphorus in treated water. Doing the above should recover your plant in a week's time.
Else you need to apply acclimatised bioculture.

Contact for further assistance at 9910170604 or chandan.mohanty@amrit-cwt.com

Thanks and regards,
Chandan Mohanty
Technical Advisor
Amrit Clean Water Technologies Pvt. Ltd.

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