Water
is the most important compound for life on Earth, and drinking water is
a major concern for the 21st century. All living things need clean, safe water
as a basic need. Water covers more than 71 percent of the earth's surface, but
about 1% of it is drinkable by international standards due to various
pollutants. Industrial wastewater, agricultural pollution, municipal
wastewater, and environmental and global changes are the main sources of water pollution.
Even heavy metals, dyes, and microbes levels are dangerous to human health, the
aquatic system, and the environment. According to a 2007, Food and Agriculture
Organization assessment, perfect water shortages will affect 1.8 billion people
living in countries, and water stress could affect two-thirds of the world's
population.
Effluent treatment plant process in the textile industry as below-
A. Process operation of the effluent treatment plant
The
effluent treatment concept is an activated sludge process of the anaerobic
process in which performance is better than other conventional processes.
Effluent from the washing, floor flows by gravity through the drain line and
after passing through mechanical auto screens, where the solid particles are
removed, the effluent gravitates to the balancing or equalization tanks. Where
it undergoes mixing and storage before being pumped forward at a steady rate in
the reaction chambers. The main theme of the balancing or equalization tank is too homogeneous the effluent from the dye
floor house.
In
the reaction chambers the Acid, Coagulants, and Flocculants are used to
separate the colloidal particle which is separated from the primary settling
tank as sludge. The upper flow is passed through the aerobic tank. Nutrients (N.P) are being dosed in the aerobic
tank to maintain pH = 6.5-7.5 and N&P for bacterial survival. In the
primary settling tanks, the sediment is collected to the sludge collection pit manually and dewatered by a filter press. The biological treatment system
consists of a three-stage. The aeration tank flowed by a final settlement tank with
settled biological solids being returned to the biological tank. The MLSS of
the biological tank should be 3000-3500 RPM or SV 30% should be 15-20%. In the
biological tank, the air is being passed to live the bacteria. In the absence
of air (oxygen), aerobic bacteria will die. So, continuous aeration is
essential for the biological reactor. Excess
MLSS or SV 30% must be collected to the sludge thickening tank from the
final settling tanks to dewater by filter press. From time to time the DO of the biological
tank should be checked to ensure aerobic condition. The treated effluent
overflows from the final settling tank and passes to the final collection pit
from where it is discharged or you can use it for irrigation.
B. Units involved in the effluent treatment plant are as follows
a.
Screening pit.
b.
Auto screening unit
c.
Equalization tank
d.
Reaction chambers (pH correction, coagulation, and flocculation)
e.
Primary clarifier
f.
Aerobic biological reaction chambers
g.
Secondary clarifier
h.
Outlet tank
i.
Sludge thickening tank
j.
Filter process
C. Details of each unit
1. Screening
tank
Clean
regularly the free-floating and sediment materials due to run the wastewater feed
pump's trouble-free operation.
2. Equalization
unit
Keep
continuous air into the unit by means of an air blower as shown. This will help to
equalize the load of the effluent.
3. Reaction
unit
a. pH correction and lime (coagulation add) reaction unit: keep running during plant operation. Firstly, check the pH and make it 6 to 7 and adjust the lime to keep the pH 7.5-8.
b. Coagulation unit: keep running during the plant running period, and observe and adjust the amounts of coagulants (Alum/Ferrous sulfate) to make the complete coagulation. The amount of coagulants depends on the load of effluents and also on the pH.
c. Flocculation unit: keep dosing the polyelectrolyte during plant operation, and observe and adjust the moment of doses to complete the flock formation.
a. pH correction and lime (coagulation add) reaction unit: keep running during plant operation. Firstly, check the pH and make it 6 to 7 and adjust the lime to keep the pH 7.5-8.
b. Coagulation unit: keep running during the plant running period, and observe and adjust the amounts of coagulants (Alum/Ferrous sulfate) to make the complete coagulation. The amount of coagulants depends on the load of effluents and also on the pH.
c. Flocculation unit: keep dosing the polyelectrolyte during plant operation, and observe and adjust the moment of doses to complete the flock formation.
4. Primary
clarifier
a. Two hours intervals take out the sludge by opening the valve to the sludge bed and visualize the sludge outlet to close the valve. It is close to 10 minutes.
b. Over the flow must be free from coagulant practices.
c. Something is very helpful for draining the sludge into the equalization tank if the color load is very high in the equalization tank.
a. Two hours intervals take out the sludge by opening the valve to the sludge bed and visualize the sludge outlet to close the valve. It is close to 10 minutes.
b. Over the flow must be free from coagulant practices.
c. Something is very helpful for draining the sludge into the equalization tank if the color load is very high in the equalization tank.
5. Biological
reaction unit
a. Take overflow from the primary clarifier.
b. Air must be passed through the water body to maintain the D.O. level of 1-4 ppm.
c. Maintain the N&P level by adding Urea and phosphoric acid.
d. It possibly checks the bacteria with an electronic microscope.
e. Fresh cow dung (must be free from weeds) must be added at overhauling and starting period.
f. Maintain the SSV 30% at the biological reaction chambers by recycling the matured sludge period.
g. Not stop the blower at stress for more than 2.5 hours.
a. Take overflow from the primary clarifier.
b. Air must be passed through the water body to maintain the D.O. level of 1-4 ppm.
c. Maintain the N&P level by adding Urea and phosphoric acid.
d. It possibly checks the bacteria with an electronic microscope.
e. Fresh cow dung (must be free from weeds) must be added at overhauling and starting period.
f. Maintain the SSV 30% at the biological reaction chambers by recycling the matured sludge period.
g. Not stop the blower at stress for more than 2.5 hours.
6. Secondary
clarifier
a.
Continuously run the motor-driven scraper.
b.
Continuously ore one-hour interval takes out the sludge and recycles it to a
biological reaction tank.
c.
Overflow will be connected to the intermediate tank.
7. Intermediate
and effluent tank
a. Overflow
from the secondary clarifier will be connected as a feed tank for dual media.
b.
The overflow from the intermediate tank or from dual media will be connected to
the effluent tank as a discharge tank.
8. Dual
media
It is to reduce the suspended solids
and also the biological load 5-6 hours intervals should be backwash.
9. Filter
process
Plate and plate
type filter press. Its capacity = is 2000 M3 per day. Regularly the cake
should be out from the filter press.
10. Sludge
drying bed
a.
Sludge from the primary clarifier will be connected to the sludge thickening
tank.
b. The filtrate will be recycled into the equalization tank.
c.
Upper thicker sludge will be taken out to dump it to avoid the clog of the filter.
d.
Periodical and skilled operation is required to get optimum performance.
It is recommended that a daily operational log sheet be completed by the plant operator as a record of the performance of the plant as follows:
a.
pH and the temperature of the equalization tank.
b.
Daily flow measurement of effluent in the ETP
c. The pH of the aerobic biological tank and final output.
d.
MLSS 3 or SV 30% of the aerobic biological tank.
e.
Dissolved Oxygen (DO) of the biological and output
f.
BOD and COD of the inlet and outlet of anaerobic reaction chambers.
g.
BOD and COD of the inlet and outlet of Anaerobic
h.
TDS and TSS of the outlet tank
D. General information on ETP
Type
of effluent
|
Mainly
washing effluent.
|
Quality
of effluent
|
7200M/Day
(300 KL/Hr.)
|
Treatment
hours
|
24
Hrs. /Day.
|
Treatment
concept
|
Activated
sludge process followed by chemical and aerobic treatment.
|
E. Inlet & outlet characteristics
Parameters
|
Inlet
|
outlet
|
PH
|
3-14
|
6-9
|
BOD,
mg/liter
|
150-200
|
<50
|
COD,
mg/liter
|
200-350
|
<200
|
Total
suspended solids, mg/liter.
|
250-350
|
175
|
Oil
and grease, mg/liter.
|
15-20
|
5
|
Temperature,
c
|
30-35
|
Ambient
|
F. Routine maintenance of ETP
The following
actions should be taken to ensure optimum performance of equipment and when
malfunction does occur, actions initiated to repair/replace faulty items put back
in service with the minimum delay. It is recommended that a logbook sheet
be completed by the plant operator as a record of equipment. Routine
lubrication of equipment should also be included on the log sheet daily.
G. Check and change over where applicable
a.
Screening unit
b.
Effluent feet
c.
Nutrient dosing
d.
Sludge return
e.
Spray pump
f.
Roots blowers
g.
Check the oil and grease of all related equipment. Change the same whenever
required
h.
At the start of all machines the gear oil is within one month.
i.
For blower must maintain the clear and dust-free air surrounding the machine.
j. Regularly clean the filter to avoid the air an obstacle in the blower (weekly once),
k.
Change the standby units every 8 hours interval
l.
Check all the pumps to avoid dry runs which could be the cause of motor failure
m.
Regularly check the spray nozzle to avoid clogging or jamming
n.
Always check the voltmeter reading in the control board. If it is less than
399V, shut down the plant to avoid the burnout of the motors.
o.
Clean the obstacle of the diffuser – yearly once.
p.
Overhauling once a year.
H. Chemical preparation and operation
Name of
chemicals that may be used in ETP as below-
a.
Lime.
b.
Aluminum sulfate
c.
Acid
d.
Ferrous sulfate
e.
Decoloring agent
f.
Polyelectrolyte
g.
Urea
h.
Phosphoric acid
i.
Bleaching
I. Details of chemical preparation and dosing
1. Lime
preparation and dosing.
a.
Prepare a 10% solution in the mixing tank.
b.
Transfer it to dosing to maintain the pH
c.
Adjust dosing to maintain the pH 7-8
d.
Clean the tank every week to remove the sludge impurities (stone pieces) from
its bottom to avoid pump damage and choking problems
e.
Keep continuous mixing by means of mixing motor and air passing.
2. Ferrous
sulfate solution preparation and dosing
a.
Prepare a 10% solution of ferrous sulfate
b.
Transfer it to the dosing tank
c.
Adjust the dosing by observing the coagulation
d.
Keep continuous mixing by means of mixing motor and air diffuser
e.
Clean the tank every week to remove the sludge impurities from its bottom to
avoid pump damage and coking problems.
3. Polyelectrolyte solution preparation and dosing
a.
750gm PE per 2000L of water
b.
Mixing it vigorously
c.
Transfer it to the dosing tank
d.
Adjust the dosing by observing the flocculation condition
4. Urea
phosphoric acid
a.
Add 3Kg urea and 2 Kg phosphoric acid in water
b.
Mixed it vigorously by air
c.
Dose it to 1st tank of the biological tank slowly by one day
5. De-coloring
agent
If
color is not removed by coagulation and flocculation please add the de-coloring agent with Acid alum ferrous solution.
6. sulfuric
or hydrochloric acid
a.
Prepare 2.5% solution in a PVC tank
b.
Adjust dosing to maintain the pH 6.5-7.5
J. Safety
a.
During chemical preparation and transformation please follow the respective
MSDS
b.
For mechanical maintenance, appropriate protective equipment should be used
c.
For electrical maintenance please cut out the switch
d.
Sludge handling period must use hand gloves, goggles, and musk
e.
Use appropriate sound protectors for ears in the blower room.
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