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Activated Sludge Tank and Treatment

What is Activated Sludge Tank and Treatment ?

Activated sludge tank

We  selected 210  m3 capacity existing concrete activated sludge tank for bio cultivation process.  Maintained mlss as 3000 mg/litre 7000 mg/litre , do value maximum 4 mg/litre and minimum 1.0 mg/litre., ph  6.5 to 7.9 , sv-30 as 300  to 500 ml/litre, temperature is < 37  degree celsius and constant feed flow rate. Control of the activated sludge tank process is important to maintain a high treatment performance level under a wide range of operating conditions

Activated sludge treatment

After equalization process using acid to reduce  ph from  9.0 to 6.5. After neutralization process  the effluent   are giving constant feed flow rate 20 m3/hr into bio tank. Here 20 m3 to 24 m3/hr  is re circulated from secondary clarifier   and fed in to bio tank process .the heavy organic solids, gradually fed into biological tank ( capacity 210 m3 ) process containing millions of microorganisms that can only survive and multiply in an environment containing free oxygen that is dissolved in the water and a food source. This method for treating wastewater is referred to as the activated sludge process. Oxygen is provided by pumping and diffusing air (similar to how air is pumped and diffused in a fish aquarium) into large tanks containing the microorganisms and   raw effluent. The mixture of microorganisms, raw  effluent and dissolved oxygen is referred to as mixed liquor suspended solids (mlss). After the aeration period, the mlss is transferred to secondary clarifier, where it is allowed to settle by gravity leaving a clear liquid referred to as  electro coagulation feed effluent . BIOLOGICAL PROCESS REACTIONWhile the settled mlss is returned to the aeration tanks to maintain the appropriate population and cultures of microorganisms. Return of the mlss from secondary m clarifier  tanks to the front of the aeration tanks is referred to as return activated sludge (ras). As the microorganisms multiply, the amount of food available in the raw effluent will become insufficient and the quality of treatment can degrade. . This wasting is referred to as waste activated sludge (was) ,this excess sludge tank fed in to sludge bed and reused ( like natural fertilizer) . After biological process  input  raw  effluent cod reduces minimum50%.

Biological process reaction :

Important maintaince of process:

  • The principal factors in procedure control are the subsequent:
  • Maintenance of dissolved oxygen levels within the aeration tanks.
  • Regulation of an amount of returning activated sludge treatment
  • Control of a waste activated sludge tank

Standard turbidity solution preparation of Activated sludge treatment

 

Solution a Solution b 400ntu

 

Take 1 gm of hydrazinium sulfate in 100 ml

Volumetric flask

Take 10 gm of hexamethylein tetramine in 100 ml volumetric flask Take 5 ml solution a & 5 ml solution b in 100 ml volumetric flask
Make up to 100 ml by using dm water Make up to 100 ml by using dm water Keep 24 hrs at    25’ c
Make up to 100 ml by using dm water
100 ntu 10 ntu
Take  25 ml of 400 ntu solution in 100 ml

Volumetric flask

Take  10 ml of100 ntu solution in 100 ml

Volumetric flask

Make up to 100 ml by using dm water Make up to 100 ml by using dm water
Prepare weekly once Prepare weekly once

Operation procedure

Set zero by using distilled water

Change the range to 0-200

Place test tube of 100 ntu solution

Adjust the display to 100 by using calibrate knob

Check the meter by using 10 ntu solution

Both are correct ,then check the samples

Standardisation of edta solution-1

Burette

x n edta solution

Conical flask

20 ml 0.02n calcium carbonate solution

2-3 drops ammonia buffer solution

Pinch of erio chrome black –t indicator

Titration

0.02n calcium carbonate vs x n edta solution

Endpoint

pink color change to sky blue

Calculation

Normality of edta x =                 20 x 0.02

titrate value

Standardisation of edta solution-2

Burette

X n edta solution

Conical flask

56 mg zinc sulfate dissolved in 10-20 ml distilled water

5 ml ammonia buffer solution

Pinch of erio chrome black –t indicator

Titration

zinc sulfate vs x n edta solution

Endpoint

pink color change to sky blue

Calculation

Normality of edta x =               wt of znso4 x titrate value

287.54 x 1000

Standardisation of sulfuric acid solution

 

Titration

Burette X n sulfuric acid
Conical flask 20 ml 0.02n sodium carbonate
Indicator Methyl orange
Titration value A1
End point Golden yellow to red orange

Calculation

Normality of sulfuric acid x =                       20 x 0.02

a1

Standardisation of sodium hydroxide

 

Titration

Burette X n sulfuric acid
Conical flask 20 ml y n   sodium hydroxide
Indicator Phenolphthalein
Titration value A2
End point Disappearance of pink color

Calculation

 

Normality of sodium hydroxide y=                      a2 x x

20

Standardisation of sodium thio sulfate                                                                  solution

 

Buette

x  n   sodium thio sulfate solution

Conical flask

20ml 0.1 n potassium  dichromate solution

20ml dilute hydrochloric acid

20ml 10% potassium iodide solution

2ml starch indicator

Titration

0.1n potassium dichromate vs x n sodium thio sulfate solution

Endpoint

disappearance of dark blue

Calculation

Normality of sodium thio sulfate x =                  20×0.1

titrate value

Standardisation of ferrous ammonium sulfate                                                                  solution

 

Burette

X n ferrous ammonium sulfate solution

Conical flask

10ml 0.25 n potassium dichromate solution dilute up to 100 ml by using dm water

30ml conc. Sulfuric acid

10min cooling

2-3 drops ferrion indicator

Titration

0.n potassium dichromate vs x n ferrous ammonium sulfate

Endoint

Bluish green to reddish brown

Calculation

Normality of ferrous ammonium sulfate x =                           10×0.25

titrate value

Standardisation of silver nitrate solution

 

Burette

x  n silver nitrate solution

 

Conical flask

20ml 0.028n sodium chloride solution

4-5 drops potassium chromate indicator

Titration

0.028n sodium chloride vs x n silver nitrate solution

Endpoint

Appearance of brick red

Calculation

normality of silver nitrate x       =                         20×0.028

titrate value

Standardisation of potassium permanganate

urette

x n potassium permanganate solution

ical flask

20 ml  0.1n oxalic acid solution

20 ml dilute sulfuric acid solution

Heated to 60^c – 80^c on a wire gauze

Titration

0.1n oxalic acid vs x n potassium permanganate

Endpoint

 

appearance of pink color

Calculation

Normality of potassium permanganate x =                   20×0.1

titrate value

Advantages of Activated sludge treatment

Efficient removal of cod(50% to 60%) and bod.

Good quality of effluent is obtained.

Compact design of Activated sludge tank

About Engr. Kh. Mashiur Rahman

He is Garment Automation Technologist and Editor in Chief of Autogarment. He is certified Echotech Garment CAD Professional-China, Aptech-India, NCC-UK and B.Sc. in CIS- London Metropolitan University, M.Sc. in ICT-UITS. He is working as a Successful Digital Marketer and Search Engine Specialist in RMG sector during 2005 to till now. Contact him- apparelsoftware@gmail.com

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