The sewage treatment plant is designed to treat wastewater generated from the processing unit. The treatment plant will have two distinct sections namely Fluidized Bed Bioreactor Biological Treatment and Electro coagulation Treatment Plant. The Effluent treatment plant is designed to treat 2,000 m3 of Textile Dyeing effluent generated from the process house. The plant will be capable of operating at the flow rate of 100 m3/hr. The operating cycle of the plant shall be 20 hours.
Sewage Treatment Plant Characteristics
The Sewage Treatment Plant is designed based on the analysis of effluent analysis report of Combined Effluent provided by you.
Characteristics
Value
PH
12
Suspended Solids
250 mg/L
BOD 5 days 20 Deg C
500 mg/L
COD
1200 mg/L
COLOUR
400 (Hazen)
Total Hardness
200 mg/L
Silica
Sodium
30-50 mg/L
2000-3000 mg/L
Chloride
1500-2500 mg/L
Sewage Treatment Plant Approach
The Sewage Treatment Plant scheme is selected based on years of experience in handling similar kind of wastewater. The biological treatment plant is designed based on the Fluidized Bed Bio-reactor & Electro coagulation system is used after the Biological treatment. The following treatment scheme is proposed for your requirement:
Combined Effluent Treatment Plant
Primary Treatment
Bar screening – 3 stages.
PH correction
BOD & COD removal by Fluidized Bed Bio-reactor
Secondary Clarifier
Secondary Treatment
Electro coagulation process
Flash mixer
HRSC Clarifier.
Sand Filter
Sludge Management
Sludge thickner
Screw pump
Filter press
Sludge storage
Treated Water Quality
The treated water quality at the outlet of the respective plant will be as follows:
After Biological treatment plant
Parameter
Value
PH
7.0 – 8.0
BOD
Less than 100 ppm
COD
Less than 200 ppm
COLOUR
300 (Hazen)
Suspended Solids
250 ppm
Total Hardness
50-100 ppm
Silica
30-50 ppm
Sodium
2000-3000 ppm
Chloride
1500-2500 ppm
After Electro coagulation and Filter Press
Parameter
Value
PH
6.5-7.0
BOD
Less than 30 ppm
COD
Less than 100 ppm
COLOUR
Less Than 10 (Hazen.) / 50 PtCo unit
Suspended Solids
Less then 5 ppm
Total Hardness
50-100 ppm
Silica
Less then 2 ppm
Sodium
2000-3000 ppm
Chloride
1500-2500 ppm
Scope of Supply
S.No
Description
quantity
COMBINED EFFLUENT TREATMENT PLANT
Primary Treatment
1.0
Acid dosing pump of PP construction
2 nos (1W + 1S)
2.0
Air blower with accessories
5 nos( 3w+2S)
3.0
Fine Bubble Vertical Diffusers.
600 nos
4.0
FBBR Random Bio-Media
8.4 Million Pcs.
5.0
Effluent Feed Pumps
2 nos. (1W + 1S)
6.0
Secondary Clarifier Mechanism
1 set
7.0
Sludge Re-Circulation Pump.
2 (1W +1S)
8.0
Motorised Rotary Bar Screen
2 SETS.
Secondary Treatment
1.0
Electro coagulation skid
3 nos (2W + 1S)
2.0
Polymer dosing pump of PP construction
2 nos (1W + 1S)
3.0
Flash mixer
1 set
4.0
Effluent Feed Pumps
4 nos (2W +2S)
5.0
HRSC Clarifier Mechanism
1 set
Sludge Management
1.0
Screw pump
2 nos.
2.0
Filter press
1 no.
INSTRUMENTS
1.0
PH indicator & controller
1 no.
2.0
Level controller
4 nos
3.0
Temperature indicator
2 nos
4.0
On-Line DO meter
1 no
5.0
Inverter for Effluent Pumps
2 nos
6.0
Inverter for Aeration tank Blowers
2 nos
7.0
Lab Accessories
1 set
8.0
Digital TDS meter
1 no
9.0
Digital Portable pH Meter
1 no
10.0
Digital Portable DO Meter
1 no
AUTOMATION PANEL
1.0
ETP panel with PLC and D.C. pulse Power controller from CROSBY Controls, UK., Inverters and control Accessories.
3 SETS.
2.0
ALARM ANNUNCIATOR PANEL
1 SET
3.0
OPTIONAL : SCADA SYSTEM WITH CENTRALISED CONTROL SYSTEM WITH COMPUTER INTERFACE AND SOFTWARE.
1 SET.
Technical Specification
Effluent treatment plant
Description
Specification
MOTORISED ROTARY Bar Screen
Qty
2 NO
Material of construction
SS
Type
Motorised
AIR BLOWER FOR EQUALISATION TANKS
No of offered
2 nos (1 w + 1s)
Capacity
1000 m3/hr @ 5000 mmwg
HP/RPM
25.0/1440
TYPE
TRI LOBE
BRAND
DRESSER ROOTS, USA.
AIR BLOWER FOR AERATION TANKS
No of offered
3 nos (2 w + 1s)
Capacity
1500 m3/hr @ 5000 mmwg
HP/RPM
40.0/1440
BRAND
TRI LOBE
BRAND
DRESSER ROOTS, USA.
Diffusers for BIOLOGICAL TANK
Type of diffusers provided
Fine bubble
No of offered
600 nos
Material of construction
EPDM
Size of diffusers
100 mm dia * 225 mm long
BRAND
IFU, GERMANY
acid DOSING SYSTEM
No of pumps offered
2 nos
Capacity
100 LPH
Material of construction
PP
BRAND
Surya
Type
Plunger
Pressure
4 bar
EFFLUENT FEED PUMPS TO aeration tank
Qty
2 NOS (1W + 1S)
Material of construction
CI
HP
10
FLOW
100m3
BRAND
JOHNSON / KIRLOSKAR
BIO SLUDGE RE-CIRCULATION PUMP
QTY
2 NOS (1W +1S)
MOC
CI
HP
3.0
FLOW
25m3
BRAND
JOHNSON / KIRLOSKAR
SECONDARY CLARIFIER MECHANISM
MOC
MS WITH EPOXY COATING
POWER
5HP
DISSOLVED OXYGEN METER
TYPE
ON-LINE
BRAND
INSTRONIX
OUTPUT TO INVERTER
4-20mA.
QTY
1 no
Secondary Treatment
electro coagulation system
No of offered
5 nos (4W + 1S)
Capacity
25 m3/hr each
EC SKID MOC
FRP
Electrodes
MS
flash mixer
No. of mixer offered
2 no
HP & RPM
2 HP / 100 RPM
BRAND
ROTOMOTIV, ITALY
HRSC CLARIFIER MECHANISM
MOC
MS WITH EPOXY COATING
POWER
5 HP
INVERTER FOR FEED PUMPS
RATING
7.5KW /10HP.
BRAND
YASKAWA, JAPAN
QTY
2 nos
INVERTER FOR AERATION TANK BLOWERS
RATING
30KW /10HP.
BRAND
YASKAWA, JAPAN
QTY
2 nos
FEED PUMPS for ec skid
No offered
2 nos (1w +1s)
Capacity
100 m3/hr each
Head
10 mwc
Motor HP
10
Material of construction
CI
FEED PUMPS for SAND FILTER
No offered
2 nos (1w +1s)
Capacity
100 m3/hr each
Head
10 mwc
Motor HP
10
Material of construction
CI
Sludge Management
SLUDGE THICKNER
No of offered
1 no.
MATERIAL OF CONSTRUCTION
M.S WITH EPOXY COATED
POWER
1 H.P
fILTER PRESS
No. of offered
1 SET
SIZE
800MM X 800MM
NO. OF PLATES
40
MOS
PP
MICRON SIZE
15
MOTOR H.P
3
SCREW PUMP
NO.O F OFFERED
2 NOS.
POWER
7.5 HP
CAPACIY
10 M3 / Hr
Type
Screw
Pressure
10 Bar
MOC
Alloy steel & EPDM
pH CONTROLLER
RANGE
1-14
BRAND
COUNTRONICS
OUTPUT
RELAY
DISPLAY
LED DISPLAY
LEVEL CONTROLLER
BRAND
MINILEC
TYPE
HIGH / LOW
QTY
4 NOS
TEMPERATURE INDICATOR CONTROLLER
RANGE
0 -200’C
DISPLAY
LED DISPLAY
OUTPUT
RELAY
BRAND
SELECTRON
DIGITAL PH CONTROLLER
RANGE
0 – 14
DISPLAY
LED DISPLAY
OUTPUT
RELAY AND 4 – 20mA.
BRAND
COUNTRONICS
ON LINE DO METER
RANGE
0 – 20
DISPLAY
LED DISPLAY
OUTPUT
RELAY
BRAND
INSTRONIX
Schedule of Exclusions
Our supplies will be restricted to the items included in the technical data. The list of exclusions from our supply is given below:
All civil works like storage tank, foundation for mechanical equipment, control room etc.
All types of electrical works like motor control center, switch gear panel, local push button starters and all kinds of power cabling to the motors, motor starters, MCC panel, earthing etc.
Piping/ drains of the plant and interconnecting and Air distribution pipelines.
All consumables like power, effluent, chemicals and lubricants required for initial start-up and normal operation of the plant.
Storage tanks for Acid, and Polymer.
Unloading, handling and safe storage of the materials at site.
Testing facility for testing raw and treated effluent.
Electrical Drives
The following are the list of electrical works required to be carried out by the client . CONFIDENT will furnish list of drives, HP ratings and layout.
RESPONSIBILITIES OF CONFIDENT ENGINEERING INDIA PVT LTD (SUPPLIER) ARE AS FOLLOWS.
SUPPLY OF THE ALL THE EQUIPMENT AND PARTS AS AGREED IN THIS CONTRACT.
DESIGN AND DRAWING OF CIVIL LAY-OUT AND PIPE LINE DRAWINGS AND CO-ORDINATE WITH THE CIVIL ENGINEER NOMINATED BY M/S.AUTO TEXTILE LIMITED.
SUPERVISION OF THE EXECUTION OF THE CIVIL AND PIPE LINES.
ERECTION AND COMMISSIONING OF THE PLANT.
TRIAL RUN AND TRAINING TO THE OPERATORS.
RESPONSIBILITIES OF CLIENT ARE AS FOLLOWS.
EXECUTION AND COMPLETION OF CIVIL WORK.
SUPPLY AND EXECUTION OF PLATFORMS, RAILS AND ACCESSORIES.
SUPPLY AND INSTALLATION OF ALL PIPE LINES AND ACCESSORIES.
SKILLED AND UNSKILLED MAN POWER FOR THE EXECUTION OF PIPELINES AND INTERCONNECTIONS.
SKILLED AND UNSKILLED MAN POWER FOR UN LOADING, INSTALLATION OF EQUIPMENTS, ELECTRICAL CABLING, PLUMBING, WELDING AND MANUAL WORK, WHENVEVER AND WHEREVER NECESSARY.
RETURN AIR TICKETS, LOCAL TRANSPORT AND BOARDING AND LODGING FACILITIES FOR THE ERECTION ENGINEERS FROM CONFIDENT.
SUPPLY OF CHEMICALS, LAB TESTING ARRANGEMENTS AND OPERATORS TO RUN THE PLANT.
SUPPLY OF PEBBLES AND GRADED SAND FOR SAND FILTER.
SUPPLY OF COW DUNG, UREA, DAP, MOLASES / SUGAR / STARCH FOR DEVELOPING BACTERIA CULTURE.
FLOW DIAGRAM
Package Sewage Treatment Plant Cost
OPERATING COST OF ETP FOR 2000M3 / DAY.
SL.NO
DESCRIPTION
CONSUMPTION
UNIT
COST
AMOUNT
1
POWER
145X 20HRS
KWH
Tk.2.5
Tk.7250
2.
ACID
200
LITRE
Tk.10
Tk.2000
3.
POLYMER
2
KG
Tk.400
Tk. 800
4.
MAN POWER
4
Tk.150
Tk. 600
5.
ELECTRODE
40
KG
TK.80
Tk.3200
TOTAL
Tk.13850
OPERATING COST FOR 2000M3 OF EFFLUENT TREATMENT IS Tk.13850/-
Package sewage treatment plant cost per m3 of effluent treatment is tk. 6.92/-
Fluidized Bed Bioreactor Treatment process. The reasons are as follows. Due to the FBBR Media, the Surface area of the Bacteria to the Effluent water is higher by 10 times. Due to attached growth of the Bacteria, the Bacteria count known as MLSS is very high compared to conventional Biological treatment plant. In the conventional process, the Bacteria count MLSS is 2500mg/L, whereas in the FBBR process the Bacteria count MLSS is 10,000 to 12,000mg/L. The FBBR process is easy to maintain and does not get collapsed due to variations in the load or temperature or SVI (Sludge Volume Index) Big civil tanks for Aeration, and Secondary Clarifier are not needed in this FBBR process. The retention time in FBBR process is 4 – 6 Hours, whereas in the Conventional Biological process, the retention time is 28 – 36 Hours.
Main use of FBBR Reactor
To Reduce the BOD and COD up to 50 to 60 percentage
To increase the Dissolved Oxygen in the outlet effluent
To remove partially color from fluidized bed bio reactor
To remove the odor in the effluent
To increase the efficiency of Electro-Coagulation system
To reduce the current and electrode consumption in EC system
To remove the ammonia and all other Hazardous gas
Fluidized Bed Bioreactor Advantages
Less Civil Area for fluidized bed bioreactor
Attached Bacteria growth.
High MLSS.
Highly Reliable Process which is less prone to Collapse.
Easy to Maintain.
Long life of the FBR Media.
No need of Secondary Clarifier.
Fluidized Bed Bioreactor Biological Treatment
pH Correction
Reduces the BOD and COD levels in the Raw Effluent.
Increases the Dissolved Oxygen Content.
Removes the odour.
2 types of process, Fluidized Bed Bio-Reactor & Activated Sludge Bio-Reactor.
Secondary Clarification
Maine use of Secondary Clarifier:
To Recirculation the Bacteria to the FBBR system
To reduce the suspended solids in the effluent
To avoided the Bacteria escape to other system
To remove the odor in the effluent
To increase the efficiency of Electro-Coagulation system
To reduce the current and electrode consumption in EC system
To increase the efficiency of FBBR system
Fluidized Bed Bioreactor Process description
Initially raw effluent is collected in collection storage tank of 1500mm *1500mm *1500mm (1.5 Hours Capacity). The Effluent is pumped to Equalization tank in which the Effluent is homogenized. The volume of equalization tank is 3000mm* 3600mm* 2400mm (12 Hours Capacity).
After equalization process the Effluent is fed to the Biological process. The pH Neutralization is done before the Biological Process.
The activated sludge process and After Filtration process, the treated water quality is as per Bangladesh Pollution Control Board Regulations ( COD < 200 mg/litre, TSS < 30 mg/litre & etc).
tank volume is 3000mm*3000mm*2400mm (12 Hours Capacity). The retention time is 12 hrs for full capacity of 40m3/Day. The Activated Sludge Process is proposed to be converted to FBBR by addition of FBBR Media in future when the ETP Flow rate will reach the full Capacity of the plant. The COD value is reduced by 40-50% from input (raw effluent). The parameters of SV-30 as 300 ml-500 ml/litre, PH as 6.5 to 7.5 and DO as 1.5 to 2.5 mg/litre and SVI value is 100 to 150 mg/litre are maintained.
After the biological process, the BOT outlet is fed into the secondary clarifier where the bio sludge is settled and Re- circulated to the BOT tank.
The superannuated liquid is fed into EC-I feed tank followed by EC process. The COD value is reduced minimum 40% and maximum 60 % from the input .
After EC process, the treated water fed into flash mixer, anionic polymer flocculent is dosed and then passed to the Sludge Settling clarifier having the volume of 3600mm* 3300mm* 2400mm. The sludge particles are settled in this Clarifier and SUPERNATED CLEAR LIQUID is fed into filter feed tank
( 3000* 3300* 2400HT).
From the filter feed tank the treated effluents are fed into MULTIGRADE SAND FILTER (Dia-1800mm * 2100mm Height).
Bio sludge and EC sludge are fed into sludge thickener having the volume of Dia- 1500 * 2400 HT.
After Filtration process, the treated water quality is as per Bangladesh Pollution Control Board Regulations ( COD < 200 mg/litre, TSS < 30 mg/litre & etc).
From the sludge thickener sludge’s are separated using FILTER PRESS and stored in sludge storage area of fluidized bed bioreactor
723gm of Disodium salt of EDTA is dissolved in 1000ml of distilled water.
0.02N CALCIUM CARBONATE SOLUTION
Take 1.0gm of Calcium carbonate in a conical flask , add 50 ml of distilled water Add 20.5 ml of 1N HCl , warm and cool and transferred to 1000ml standard flask and make up to the mark with distilled water.
BUFFER SOLUTION
9 gm of Ammonium chloride was dissolved in 143 ml of Conc. Ammonium hydroxide . This solution is A.
179 gm of Disodium salt of EDTA + 0.78 gm of MgSO4.7H2O was dissolved in 50 ml of distilled water. This solution is B.
Add these are solution and mix well. Then make up to 250ml with distilled water.
ERIOCHROME BLAKE –T INDICATOR
5gm of Eriochrome blake –T + 100 gm of Sodium chloride–AR grade.
CALCIUM HARDNESS
1N NaOH SOLUTION
40 gm of Sodium hydroxide dissolved in 1000 ml of distilled water.
MUROXIDE INDICATOR
150 gm of Muroxide dissolved in 100 gm of absolute ethylene glycol.
PHENOLPHTHALEIN ALKALINITY
.02N SULFURIC ACID SOLUTION
5ml of Sulfuric acid is dissolved in 1000ml of distilled water.
0.02N SODIUM CARBONATE SOLUTION
06gm of Sodium carbonate is dissolved in1000 ml of distilled water .
PHENOLPHTHALEIN INDICATOR
5gm of Phenolphthalein was dissolved in 95%Ethanol. 50ml of distilled water was added. 0.05N Sodium Hydroxide solution was added drop-wise until the solution turned pink
METHYL ORANGE ALKALINIT
METHYL ORANGE INDICATOR
05 gm of Methyl orange dissolved in100 ml distilled water.
ACIDITY
0.02N SODIUM HYDROXIDE SOLUTION
8 gm of sodium hydroxide dissolved in1000 ml distilled water.
FREE RESIDUAL CHLORINE
0.025N SODIUM THIO SULFATE SOLUTION
205 gm of Sodium thio sulfate is dissolved in 1000ml of distilled water
Add 0.4 gm of Sodium hydroxide
STARCH
Dissolve 1.0gm of Starch in little water .
Stir it well with a glass rod to make it as a thin paste.
This paste is mixed 100 ml distilled water .
Then boil for 2 minutes and cool to room temperature
0.1N POTASSIUM DICHROMATE
9 gm of Potassium dichromate dissolved in 1000ml of distilled water.
10% KI SOLUTION
10 gm of Potassium iodide dissolved in 100 ml distilled water.
CHLORIDE
0.028N SILVER NITRATE SOLUTION
3955 gm of Silver nitrate dissolved in 500ml of distilled water.
0.0282N SODIUM CHLORIDE SOLUTION
824gm of Sodium chloride dissolved in 500 ml of distilled water.
POTASSIUM CHROMATRE INDICATOR
25gm of Potassium chromate dissolved in 100ml of distilled water. Add Silver nitrate solution drop wise until a slight red precipitate is formed. Allow to stand for 12 hours. Filter and dilute the filtrate to 500ml.
DISSOLVED OXYGEN
0.025N SODIUM THIO SULFATE SOLUTION
205 gm of Sodium thio sulfate is dissolved in 1000ml of distilled water
Add 0.4 gm of Sodium hydroxide.
0.1N POTASSIUM DICHROMATE
9 gm of Potassium dichromate dissolved in 1000ml of distilled water.
10% KI SOLUTION
10 gm of Potassium iodide dissolved in 100 ml distilled water.
MANGANOUS SULFATE SOLUTION
Dissolve 480 gm MnSO4.4 H2O in distilled water and dilute to1000ml (Or)
Dissolve 400gm MnSO4.2H2O in distilled water and dilute to1000 ml
(Or)
Dissolve 364 gm of MnSO4 in distilled water and dilute to 1000 ml
ALKALI IODIDE-SODIUM AZIDE SOLUTION
SOLUTION –A -125 gm of NaOH dissolved 100 ml distilled water.
SOLUTION –B – 37.5 gm of KI dissolved in 37.5 ml distilled water.
High Rate Solid Content Clarifier ( HRSCC Clarifier Tank ) is used to settle the Sludge and separate from the clear treated water after Electro-Coagulation process. The Flash mixer forms an integral part of the HRSC Clarifier tank. The outlet water from the Lander of the HRSC Clarifier is clear, Colorless, and also with very low BOD and COD values. The Sludge collected at the bottom is pumped to a Sludge tank from where the sludge is handled by either centrifuge Hydro Extractor or Filter press.
Main use of HRSC Clarifier Tank
To increase the faster settlement
For sludge separation from the clear water
To reduce the suspended solids very rapid level
To improve the performance of the pressure sand filter
To get crystal clear water in outlet
To reduce the turbidity
LANGLIER SATURATION INDEX – LSI
LSI is a method of reporting the scaling or corrosive potential of low TDS brackish water based on the level of saturation of calcium carbonate.
LSI is important to boiler water and municipal plant chemists in determining whether a water is corrosive (has a negative LSI) or will tend to scale calcium carbonate (has a positive LSI).
LSI is important to RO chemists as a measurement of the scaling potential for calcium carbonate.
The LSI value is calculated by subtracting the calculated pH of saturation of calcium carbonate from the actual feed pH.
The LSI value can be lowered by reducing pH by the injection of an acid (typically sulfuric or hydrochloric) into the RO feed water.
A recommended target LSI in the RO concentrate is negative 0.2.
A polymer-based antiscalant can also be used to inhibit the precipitation of calcium carbonate.
Some antiscalant suppliers have claimed the efficacy of their product up to a positive LSI value of 2.5 in the RO concentrate (though a more conservative design LSI level is +1.8
According to Reverse Osmosis, A Practical Guide for Industrial Users LSI is estimated as the difference between the current pH of the water ( pH ) and the pH at which calcium carbonate reaches saturation ( pHLSI ) :
LANGLIER INDEX LSI = pH – pHLSI , RYZENER INDEX RI = 2 pHLSI – pH
Where
pHLSI = (9.3 + A + B) – (C + D)
where
A = (log(TDS) – 1)/10
B = -13.12 * log( Temp(K)) + 34.55
C = log[Ca as CaCO3]
D = log [Alk as CaCO3]
CONDITIONS
INDEX
NEUTRAL
TO SCALE
TO CORROSIVE
LSI
0
ABOVE 0
BELOW 0
RI
6.8
BELOW 6.8
ABOVE 6.8
SILT DENSITY INDEX – (SDI)
The SDI is a popular method for determining feed water quality in RO
applications.
It is based on the time required to filter a volume of feed water
through a 0.45 μm filter pad at a feed pressure of 30 psig.
EQUIPMENT SETUP
Assemble the test equipment per its drawing
Locate a sample tap on the feed water piping and install the test
equipment.
Adjust the pressure regulator to 30 PSI
Use a fresh filter for the actual test.
NOTE : FOR BEST RESULT
Use dull tweezers when positioning the filter to prevent puncturing
the filter.
Ensure that the O-ring is clean and in good condition, and is properly
Positioned.
Avoid touching the filter with fingers.
Flush the apparatus to remove any contaminants that may be held
With in it.
SILT DENSITY INDEX – (SDI)
TEST PROCEDURE
Take the temperature of the feed water. The temperature should not
vary more than + 1 °C between the start and end of the test.
Bleed any entrained air in the filter holder. Depending on the model
of the filter holder, either open the bleed valve, or loosen the filter
holder while cracking the ball valve. Then close the bleed valve or
filter holder.
Place a 500 ml graduated cylinder under the filter to measure the
amount of water that passes through the filter.
Open the ball valve fully, and measure the time required to collect
100 ml and 500 ml* from the time the ball valve is opened. Record
these times, leaving the valve open for 5 minutes and letting the flow continue.
After 5 minutes, repeat the time measurement required to collect 100
ml and 500 ml samples. Repeat again after 10 and 15 minutes of
elapsed time.
If the time required to obtain a 100 ml sample is greater than about
60 seconds, pluggage will be about 90%, and it is not necessary to
continue the test.
Measure the water temperature again to ensure that it did not vary
by more than 1 °C from the initial temperature.
After completing the test and disconnecting the apparatus, the filter
paper may be saved in a plastic bag for future reference.
SILT DENSITY INDEX – (SDI)
CALCULATIONS
SDI = P30 / Tt = 100 * (1 – Ti / Tf) / Tt
Where SDI = Silt Density Index
P30 = % pluggage at 30 psig feed pressure**
Tt = Total test time in minutes
Ti = initial time in seconds required to obtain sample.
Tf = time required to obtain sample after 15 minutes (or less).
NOTES
Time to collect 500 ml should be approximately 5 times greater than the time to collect 100 ml. If 500 ml collection time is much greater than 5X, SDI should be calculated using 100 ml collection times.
For accurate SDI measurements, P30 should not exceed 75%. If P30 exceeds this value, re-run test and obtain Tf at a shorter time, (T).
Effluent from the collection tank comes to the equalization tank in wastewater treatment. The main function is to act as buffer. To collect the incoming raw effluent that comes at widely fluctuating rates and position to the rest of the ETP at steady ( Average ) flow rate. During the peak hours ETP comes at high flow rate. The equalization tank stores this effluent and lets it out during the non peak time when there is no /little incoming effluent. The inlet pipe of equalization tank carries filtered effluent from cooling tower. The effluent NPSH lifting pumps move the effluent to the EC SKID.
The delivery pipe takes the effluent to the EC SKID.
The coarse bubble diffusers are short length of tubes that have holes at regular spacing .they release large bubbles in the tank to lightly aerate the effluent and also to agitate the mix continuously.
Compressed air from blower s through this air supply pipe line. This may be rigid pipe line.
inlet pipe line 2.collection tank 3.raw effluent lift sump . 4. delivery pipe 5.coarse bubble diffuser 6.air supply pipe line.
Equalization Tank Operation And Maintenance
Keep air mixing on at all times.
Ensure that the air flow /mixing is uniform over the entire floor of the tank. Adjust the placement of diffusers and the air- flow rate needed.
Keep the equalization tank in wastewater treatment nearly empty before the expected peak load hours (otherwise it will over flow)
Check and clean clogged diffusers at regular intervals.
Manually evacuate settled much/sediments at least once in a year.
Equalization Tank Trouble Shooting
S.NO
Problems
Cause
1
Insufficient mixing/aeration
Poor maintenance of diffuser cleaning and blower maintenance
2
Excessive odor
Insufficient air supply, poor maintenance and operation
3
Insufficient capacity to handle peak flows
Constant outflow pumping, do not maintained.
4
Usable capacity reduced due to solids accumulation
Poor maintenance.
Construction of coarse bubble diffusers in equalization tank.
If keeps the raw effluent aerated thereby avoiding septicity and suppressing odor generation.
If keeps said in suspension and prevents setting of said in the tank ,thereby reducing frequency
Of manual cleaning of the tank.
If membrane diffusers are used ,they will fail frequently, due to the repeated cycles expansion and contraction caused by fluctuating water levels in the equalization tank. there fore only coarse bubble diffusers must be used in the equalization tank in wastewater treatment.
