Effluent Treat Plant (ETP) Basic Working module

Effluent Treat Plant (ETP) Basic Working module

Effluent Treat Plant (ETP) is mainly used for treating waste water which is extracted from Dyeing or Washing factories. 

ETP is mainly divided in Three different functions:

1) Physical

2) Chemical

3) Biological

- In the above three functions, Chemical and Biological is mainly highlighted functions where water is treated in different stages/ filtration processes.

Blog Diagram of an ETP :-

[Note : Copy and Save the image & zoom in to see the texts inside the picture]

CHEMICAL ETP PLANT TREATMENT STAGES :-

1)  Screening Unit : All the visible and seen particles are filtered in this unit using Net type filter which is called Screening PIT.

2)  Equalization Tank : Here is the Homogenization Mixture is made after taking all the water from Washing Units, Dyeing Units, PP Spray Chamber Units, and also Sample sections waste water. In short, All the untreated water is collected in this tank for further procedure.

3) Chemical Dozing Tank : Here the chemicals are dozed step wise. Please see my picture above. There are PH adjustment , PAC dozing & Polymer dozing Units where this three different tasks are done. PH adjustment tank is for checking the PH of untreated water for balancing the PH to 7.0. And PAC dozing tank is used for Poly Aluminum Chlorite dozing, and Further thank is used for Polymer dozing. After this three chemical dozing thank , the water passes through the Sedimentation Tank where the Sludge are thicken and goes down.

3) Sedimentation Tank : In this tank the sludge are thicken and goes down because of previous chemical dozing. And from here the water passes through BIOLOGICAL TANK.

4) Sludge Thicker Tank : From sedimentation the deposited sludge are taken to Sludge Thicker Tank where -in portion : 60% Water and 40% Sludge comes from Sedimentation Tank. The Sludge is thicken in the downer portion of this Tank and then it is sent to Filter Press using submersible pump. The rest 60% Water is again sent to Equalization Tank for re treatment cycle wise.

5) Filter Press : All the sludge from Sludge Thicker Tank is drawn to filter press and in this press the sludge is pressed at high pressure and drained to 50-100 kg Jute / Plastic Bag and kept a certain time below sunlight or for drying the sludge for disposal.

Chemical Description:

a) PH Adjustment Tank : If the PH is higher then Acid is used to lower the PH level and if the PH is lower then Alkali is used to control the PH level. In short, the PH adjustment tank is used to control PH level- 7.0. In dyeing and washing factories , Salt, soda- caustic and other chemicals are uses which is mostly alkali and in that case most of the times PH is higher than 7.0 and acid is generally used to pull down the PH level but if the PH level is lower then alkali like caustic is used to pull up PH level.

b) PAC : Poly Aluminum Chlorite (PAC) , it is used for clearing the color of water. Generally textile waste water is - dark blue type color for washing factories, and in dyeing factories though the color varies but most of the times its dark or black. PAC - is kind of FITKARI which makes the color clear after applying in water.

c) Polymer : Polymer is used to control the sludge thickening. The waste water has many chemicals , dye stuff, micron smithereens cotton, etc. Polymer thickens those particles from the water to the downer portion of Sedimentation tank.

d) Water DE-coloring : If the water color is mostly dull and not improving then the water DE-coloring agent is used after sedimentation tank treatment. But if Polymer and De-coloring is used together then Polymer do not gives efficient work and in that case Polymer dozing needs to be increased gradually.

BIOLOGICAL ETP PLANT TREATMENT STAGES :-

1) Biological Tank 1 : Water is drawn from Chemical Sedimentation tank to Biological Tank 1 - for further treatment. Here - Air is passed through the water and the water is kept for a certain time in this tank to grow the Bacteria in the water. Here : Temperature is kept : 35-37 degree Celsius and PH is kept : 7-8 , Besides this the Air is applied to increase the DO level. DO means: Dissolved Oxygen in the water. The DO is kept- 4ppm. In the biological tank : Urea Fertilizer 60% & Phosphoric Acid/DAP 40% is applied to grow the bacteria level. (DAP- Di-Ammonium Phosphate)

2) Biological Tank 2 : BIOLOGICAL TANK-2  repeats the process of Biological tank-1.

3) Biological Sedimentation Basin : After treatment in the Biological Tank treated water is passed to Biological Sedimentation Basin where Step wise Anti-foaming agent is applied to control the extracted water foaming level. and Also in this basin some amount of sludge thicken in the downer portion of the Tank and 20% this amount of sludge is pulled up & applied to biological tanks cycle wise using pump , & rest 80% is passed through the sludge Thickener tank which is adjacent to Chemical ETP. Here, 20% of Sludge is applied in the Biological tank because those sludge is the main impactor of Bacteria rapid growth.

4)  Discharge Tank : This tank is only used to check the final stage water property. and If the coliform level is higher then 0.3ppm sodium hypochlorite is dozed to kill the bacteria to minimum the Coliform level.

 Chemical Description:

In the biological tank Urea Fertilizer and Phosphoric Acid/ DAP is applied to grow the Bacteria Level. Actually, Urea is used for - Nitrogen,  & DAP/ Phosphoric Acid is used for - Phosphorus and both are controller of Bacteria growth. Nitrogen + Phosphorus helps the Bacteria to grow rapidly.
(DAP- Di-Ammonium Phosphate)

Why Bacteria needs to grow?

 After chemical treatment, the water is 50% treated and controlled but while garments dyeing/ washing various different type chemicals are used in the washing/dyeing machines/bath which creates bonds in water and which is not properly removed from the water after chemical water treatment. That is why, in the water the Bacteria level needs to be grown which will break all the chemical bonds remaining in the water.
- Urea + DAP helps to grow the bacteria, but it does not birth Bacteria, Bacteria is automatically grown in the water due to Sludge, and other property. and Fine Bubble +  Urea + DAP helps those bacteria to grow rapidly and to break the chemical bonds and purify the water finally.

DO Level :- 
Aeration helps to increase the DO level of the Water. If the DO level is not sufficient then Bacteria or other living organ will not be able to live in the water. That is why DO level is very important to maintain.

CHEMICAL DOZING SUMMERY :-

Chemical ETP :
1) Poly Aluminium Chlorite (PAC) AL2CL(OH)5
2) Polymar (Poly electrolyte) : Sludge Coagulation
3) Water De-colorent : Water color controling
4) PH controlling: Alkali/ Acid

Biological ETP :
1) Urea Fertilizer
2) Phosphoric Acid/ Diamonium Phosphate
3) Anti-foaming agent
4) 0.3ppm sodium hypocholoraite to kill bacteria

BASIC REQUIREMENT TESTING PARAMETER SUMMERY :-

Chemical ETP:
1) Chemical Dozing Tank: BOD, COD, PH
2) Color Visual + Decolorent agent dozing if necessary

Biological ETP:
1) Biological Tank Inlet: BOD, COD
2) Biological Tank 1 : Temperature, DO, PH
3) Biological Tank 2 : Temperature, DO, PH
4) Discharge Tank : BOD, COD, COLOR, PH, DO, Foaming Visual check, Coliform check, etc.

CHEMICAL MIXING :
1) Lime : (800-1000 ppm) to correct PH up to : 7-8
2) Alum/PAC : (200-300ppm) to clear the water color.
3) Poly electrolyte (0.2ppm) : To settle the suspend matter & reduce SS/TSS.

Chemical Application & Identification Necessary quantity:
At first, 1 Liter of untreated water need to be taken, then drop wise diluted chemical need to be applied in the untreated water from the previously prepared Chemical Stock solution of 10%, 20. After then , Untreated water is kept for 5 minutes to see the result and then checked the visual impression of the water. This way required chemical quantity identified.

(Note: All the treatment process is customized as per Buyer water testing requirements. like- if buyer requirement is water TSS below 150 then less treatment is necessary elsewhere if the buyer requirement TSS is below 30 then much longer treatment is necessary in that case.

Thanks for reading,

Blog Written by,
K M Zahidur Rahman
Executive R&D - Ha-Meem Group