Interstoff Apparels Ltd (IAL) comprises of the latest, most technologically advanced 100% export oriented private limited company with composite knitting, dyeing, finishing and apparel manufacturing plants situated in Chandra, Kaliyakoir, Gazipur, Bangladesh. IAL installed an Effluent Treatment Plant of 75 m3/Hr capacity which is running 24 Hr in a day. By nature, our ETP is Bio-logical with Chemical namely Bio-Chemical plant. This treatment is done by four stages such as preliminary, primary, secondary and tertiary treatment. Waste water comes from mainly dyeing and washing through a trench to equalization tank so for preliminary treatment is done by screening by using net or sieve for removal of large solids such as rags, sticks, grit and grease that may result in damage to equipment or operational problems at different stages of trench.

1. Report on Effluent Treatment Plant (ETP)
Operation and Maintenance of Interstoff
Apparels Ltd. (IAL)
Submitted By:
Name: Quock San
Designation: Management Trainee
ETP (TSD), ID No.: 430033
Email: quocksan@gmail.com

2. Acronyms and Abbreviations
BOD Biological Oxygen Demand
BOD5 5-Days Biological Oxygen Demand
COD Chemical Oxygen Demand
DO Dissolve Oxygen
DoE Department of Environment
ECC Environmental Clearance Certificate
ETP Effluent Treatment Plant
IAL Interstoff Apparels Ltd.
pH Measure of Acidic or Alkaline condition of Water
SETL South East Textiles Ltd.
TDS Total Dissolved Solid
TSS Total Suspended Solid

3. Introduction
Factory Profile:
Interstoff Apparels Ltd (IAL) comprises of the latest, most technologically advanced 100% export
oriented private limited company with composite knitting, dyeing, finishing and apparel manufacturing
plants situated at Chandra, Kaliyakoir, Gazipur, Bangladesh. It’s started business in operation since
2002. Corporate office and factory are located at same location and take up an area of more than 131000
square feet and 3, 50,000 square feet for production process respectively. Interstoff Apparels Ltd are
manufacturing all type of knitted garments such as Fashion T-shirt, Polo Shirts, Knitted Shorts, Legging
Night Wear, Kid’s, Men’s , Girl’s and School wear etc. There are more than 4,000 experienced workers
are employing in the total process. The Garments unit alone has about 57 lines with a monthly
production capacity is 2.0 million pieces that is exported mostly to Europe and USA.
The main buyers include renowned brands such as, Marks & Spencer (M&S), Tesco, Kohl’s, Sainsbury,
Gap, Ralph Lauren, Debenhams, Gymboree, H&M, Zara, Mother Care, Tchibo, Cotton on, Mango etc.
IAL prides itself in meeting all international standards for good work environment that is compliant with
both national and international rules. The company is compliant with ‘Children’s wear Safety
Requirements’ and provides a ‘Completely Metal Free Environment’ for workers’ health and safety. The
factory is fully approved by several globally accepted Certification bodies like WRAP, ISO 9001:2008,
Organic, SGS and Oeko-tex Certified. IAL is also FAIRTRADE certified by the FLO-Cert Trade
Certification Committee (FLO ID: 18123).
Existing Waste Water Management at IAL:
IAL installed an Effluent Treatment Plant of 75 m3
/Hr capacity which is running 24 Hr in a day. By
nature, our ETP is Bio-logical with Chemical namely Bio-Chemical plant. This treatment is done by
four stages such as preliminary, primary, secondary and tertiary treatment. Waste water comes from
mainly dyeing and washing through a trench to equalization tank so for preliminary treatment is done by
screening by using net or sieve for removal of large solids such as rags, sticks, grit and grease that may
result in damage to equipment or operational problems at different stages of trench.
After primary filtration, the liquor passes to cooling and mixing tank in which uniform mixing of
effluents from various processes takes place. An air mixer is provided for mixing uniformly for aeration

4. and neutralization of effluent at equalization tank. The effluent is pumped to a tank in which it is
neutralized by cultural bacteria namely Bio-formula dozing. The tank has an automatic dosing controller
which at automatically control the dose of acid or alkali to maintain the required PH. Then the effluent is
pumped to the coagulation tank and to mix up different chemicals such as lime, ferrous sulfate etc.
Chemical coagulation is very effective for removal of color and suspended materials, aluminum, ferrous,
ferric chloride, chlorinate d-copper etc. To increase the efficiency of coagulation, chemical may be
added for example polyelectrolyte. Some of the soluble organic matter and light suspended solids will
form a blanket of flocculent matter with the coagulants. The blanket is skimmed off to another tank and
the remaining solution is moved to dual media filter and centrifuge hydro extractor. After filtration the
purified water sent to drain which eventually reach to the river or anywhere else.
It can be noted here that the ETP is able to deliver treated waste water within the permissible limit of the
DOE. From the outlet quality of ETP, it can be mentioned here that though the water cannot be directly
use in the dyeing, washing and finishing process. It is quite good to use in any other non-process like
cleaning of dyeing floor, toilet flashing, car washing and gardening etc.
Table-01: Characteristics of Waste and Treated Water of ETP_IAL with National Standard
Parameters
Properties of Inlet Waste
Water
Properties of Outlet
Treated Water
Discharge Water
Standard according
to ECR, 97
pH 8.3-10.8 7.2-7.7 6-9
DO (mg/l) 0.0 4.9-5.5 4.5-8
BOD (mg/l) 150-190 38-42 < 50
COD (mg/l) 260-480 135-175 < 200
TDS (mg/l) 2500-2900 1320-1940 < 2100
TSS (mg/l) 250-280 80-120 < 150
Temperature (°C) 37-45 30-32 40-45
Color (Pt. Co.) 185-245 120-150 -
Odor Light Bad Smell Slight Smell Odorless

5. Figure-01: Process Flow Diagram of ETP_IAL
Tanks Retention Time Calculation and Volume of ETP_IAL
ETP Capacity: 75 M3
/Hr
Current rate of Effluent Treatment: 55~60 M3
/Hr
Table-02: Retention Time Calculation & Volume of the ETP Tanks
Retention Time (Hr)
Sl. No. ETP Tanks Tanks Volume (M³) Rated Actual
1 Equalization - 01 165 2.20 2.90
2 Equalization - 02 238 3.17 4.18
3 Bioreactor - 01 175 2.33 3.07
4 Bioreactor - 02 215 2.87 3.77
5 Flash Mixing 19 0.25 0.33
6 Flocculation 11 0.15 0.19
7 Tube Settler - 01 45 0.60 0.79
8 Tube Settler - 02 58 0.77 1.02
9 Tube Settler - 03 58 0.77 1.02
10 Tube Settler - 04 45 0.60 0.79
Total Retention Time Hr 13.72 18.06

6. Chemical Dosing:
The dosing of coagulant solution must be prepared as the concentration of more or equal to 5% solution.
The rate of the solution is maintained by trained personnel depending on the quality of the waste water.
This dosing rate is determined by Jar test. Dosing rate of coagulant varies from 15 to 20 ml/L and dosing
rate of flocculent varies from 0.1 to 0.2 ml/L. Biological treatment process reduces TSS and BOD to a
great extent. The dosing rate of Bio-formula in our ETP is 250 g/day (a single packet) and dosing in the
equalization tank or bioreactor tank.
Maintenance of the ETP:
ETP’s goal is to treat waste water and deliver a quality product that meet the standard for environmental
discharge or reuse. Like any other facility a waste water treatment plant require continuous maintenance.
So, maintenance of ETP plant as a whole is very important. There are different types of maintenance
strategies; these are Routine maintenance, Mechanical maintenance, Breakdown maintenance and
Annual shut down maintenance. In our ETP Routine maintenance is done in every Friday and annual
shut down maintenance during Eid vacation to maintain standard quality of the discharge water. Bar
screens are cleaned about 3-4 times in everyday.
Sludge Treatment and Handling:
The sludge which is generated in the Flash mixing tank, Flocculation tank, Bio-Reactor and Tube settler
1, 2, 3 and 4 is taken to sludge sump. Here also aeration is carried out. The heavy sludge waste is then
pumped to a sludge thickener tank where the sludge is thickened at the bottom of the tank. The
thickened sludge from the thickener is pumped to centrifugal hydro extractor for dewatering the sludge.
The dewatered sludge is transformed into a cake form.
Tests Performed at the Factory:
At present simple measurement of pH, Temperature (°
C) and Temperature are performed on site using
hand held instruments and BOD tests are performed at the Fabric lab deep section through BOD sensor
meter. The advantage of these instruments does not need to be taken away and also results are obtained
immediately in field. At present we need a Multimeter to measure DO, TDS and TSS on site.

7. Table-03: Chemical Consumption in March and April, 2015 with Chemical Price/Kg at ETP_IAL
Sl. No.
Chemicals for Waste Water
Treatment
March_2015 April_2015 Price/Kg
1 Lime Powder (Kg) 14800 15020 9.25
2 Ferrous Sulfate (Kg) 17494 18000 17.5
3 Polyelectrolyte (Kg) 44.5 59 260
4 Hydrochloric Acid (L) 1392 1009 14.5
5 Bio-formula (Kg) 7.25 7.5 9950
Table-04: Chemical Cost in March and April, 2015 at ETP_IAL
Month March_2015 April_2015
Total Chemical Cost Tk. 546936.50 Tk. 558530.50
Total Flow Of Water 38678 m³ 39648 m³
Chemical Cost/M³ Tk. 14.14 Tk. 14.09
Flow of Waste Water/Hr 55.57 m³ 56.97 m³
Figure-02: Schematic Diagram of Proposed Zero Effluent Discharge Plant at IAL
Waste Water
ETP Treated
Water
Filtration
(Ultra & Nano)
Dyeing & Surface
Treatment Process
Rain water
Harvesting
Collection &
Screening
Cooling Return
(Dyeing)
Powder as
solid waste
Management
Spray
Dryer Unit
(10%)
Mechanical
Evaporation
System 20%
Softener
Process
Water Reserve Tank
(275M3
)
Toilet Flashing, Car
Washing, Floor Washing
and Gardening
Reverse Osmosis
Plant
70% Recover

8. Existing Machineries List of ETP_IAL
A. Equalization Tank Section
1. Air Compressor for Aeration and Mixing
a. Number of Units: 01
b. Type: Screw type
c. Capacity: 2.2 m3
/min
d. Max. Pressure: 10 Bar
e. Power: 18.5 kW
f. RPM: 2900
2. Effluent Transfer Pump
a. Number of Units: 02
b. Pump Flow Rate: 75 m3
/hr
c. Power: 5.5 kW
d. RPM: 2900
B. Bio-Reactor Tank Section
1. Air Blower
a. Number of Units: 01
b. Type: 3-Phase Induction type
c. Power: 3.0 kW
d. RPM: 2820
2. Effluent Transfer Pump-01
a. Number of Units: 01
b. Pump Flow Rate: 75 m3
/hr
c. Power: 5.5 kW
d. RPM: 2900
3. Effluent Transfer Pump-02
a. Number of Units: 01
b. Pump Flow Rate: 40 m3
/hr
c. Power: 4.5 kW
d. RPM: 2890

9. 4. Effluent Transfer Pump-03
a. Number of Units: 01
b. Pump Flow Rate: 30 m3
/hr
c. Power: 3.7 kW
d. RPM: 2900
C. Chemical Mixing Tank Section
1. Flash Mixture Motor for Chemical Mixing
a. Number of Units: 04
b. Type: 3-Phase Induction Type
c. Power: 0.75 kW
d. RPM: 1050
2. Flocculation Mixture Motor for Chemical Mixing
a. Number of Units: 01
b. Type: 3-Phase Induction Type
c. Power: 1.5 kW
d. RPM: 1450
D. Filter Feed Pump Section
1. Filter Feed Pump for Single and Dual Media Filter
a. Number of Units: 01
b. Type: Centrifugal Volute Type Casing
c. Pump Flow Rate: 75 m3
/hr
d. Power: 15 kW
e. RPM: 2900
E. Sludge Sump, Sludge Thickener Tank and Hydro Extractor Section
1. Sludge Transfer Pump-01
a. Number of Units: 01
b. Type: Centrifugal Type Mud Pump
c. Power: 1.5 kW
d. RPM: 2900

10. 2. Sludge Transfer Pump-02
a. Number of Units: 01
b. Type: Screw Conveyed Rotary Type Pump
c. Power: 1.5 kW
d. RPM: 1450
3. Sludge Thickener Motor
a. Number of Units: 01
b. Type: 3-Phase Induction Type
c. Power: 3.75 kW
d. RPM: 2900
4. Hydro Extractor Motor
a. Number of Units: 01
b. Type: 3-Phase Induction Type
c. Power: 3.75 kW
d. RPM: 2900
Environmental Clearance Certificate (ECC) Renewal from Department of
Environment (DoE)
Forward Application for the ECC Renewal is given to-
Deputy Director
Department of Environment
Gazipur zonal office
Gazipur
House#6, Ward#9, Noljani, Chandora, Joydebpur, Gazipur
Documents needed with the Forward Application of ECC Renewal-
1. Application for the Environmental clearance certificate (ECC) renewal
2. Sonali Bank Challan Copy of About Tk. 30000
3. Income Tax certificate
4. Trade license copy from the local govt. institute
5. Last ECC renewal copy
6. Investment board registration copy
7. Last Analysis sheet of waste water treatment of ETP outflow of DoE
a. DoE analysis sheet
b. BUET analysis sheet

11. Collection and Analysis Report of ETP Treated Water Outflow from DoE
Forward Application for the Collection and Analysis of ETP Treated Water Outflow is given to-
Director Laboratory
Department of Environment
Dhaka Division
E-16, Agargaon
Sher-E-Bangla Nogor, Dhaka-1207
Documents needed for with the Forward Application of ETP Treated Water Outflow Collection
and Analysis of -
1. Forwarding Application for ETP Treated Water Outflow Collection and Analysis
2. Sonali Bank Challan Copy of About Tk. 5600
Present Problems in Our ETP
1. Instruments for Parameter Measurement Shortage
2. Equalization and Bio-Reactor Tanks Volume
3. Civil Drain for Treated Water Discharge
4. Sludge Drainage with Treated Water
5. Centrifugal Hydro Extractor

12. Graphs from Analysis Sheets of ETP Treated Water Outflow from DoE with Relevant Date:

14. Graphs from Analysis Sheets of ETP Treated Water Outflow from A. N. M. Hamidul Kabir of the
Department of App. Chemistry and Chemical Eng. Of Dhaka University with Relevant Date:

16. Table-05: Comparison Between ETP_IAL and ETP_SETL
Sections of ETP ETP_IAL ETP_SETL
ETP Capacity of Water 75 M3
/Hr 60 M3
/Hr
Current Flow of Water 55-60 M3
/Hr 50~55 M3
/Hr
Inlet Temperature (°C) 37~45 °C 45~48 °C
Treatment Process Biological than Chemical Chemical than Biological
Equalization Tank
Separate Tank for Dyeing and
Washing Waste Water
Single Tank for Dyeing and
Washing Waste Water
Bio-Reactor Tank
Available after Equalization
Tanks
Available after Tube Settler
Tube Settler
Number of Units-04
Didn’t Overflowed
Number of Units-02
Sometime Overflowed
Chemical Dosing Minimum More than IAL
Filtering
Available and Operated
Properly
Available and but didn’t
Operated Properly
Sludge Handling
Properly Handling but
Sometimes Drained with
Treated Water
Drained into Nearest Pond
Instruments for Measuring
Parameters
pH, DO meter, BOD meter &
Temperature can be measured
Only pH & Temperature can
be measured
Discharge Water Color Colorless Slightly Brownish
Chemical Cost/M3
Tk. 14.11

17. Figure-03: ETP Drawings of IAL and SETL