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 . While 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