Wednesday, July 26, 2017

Environmental Pollution Control in Textile Industry

Environment:
The word “environment” is most commonly used for describing “natural” environment and means the sum of all living and non-living things that surround an organism, or group of organism. Environment includes all element, factors and conditions that have some impact on growth and development of certain organism. Environment includes both biotic and abiotic factors that have influence on observed organism. Biotic factors are all living things and abiotic factors are light, temperature, water and atmospheric gases. Environment often changes after some time and therefore many organisms have ability to adapt to those changes.

Environment pollution:
Environment pollution is the introduction of contaminants into the natural environment that causes adverse change (instability, discomfort, disorder and harm) in nature or ecosystem. In order ward, pollution is the discharge of unwanted material, residue and energy into the environment. Pollution can take the form of chemical substances or energy such as noise, heat or light.
 
Environment pollution by textile waste water
Fig: Environment pollution by textile waste water
There are mainly three types of pollution such as:
  • Air
  • Water
  • Soil
  • Sound or noise
There are radioactive, thermal, visual and litter that pollute in environment.

Causes of environment pollution:
  • Burning coal and other fossil fuel, which emit CO2
  • Using radioactive energy or nuclear power.
  • Using object that emit CFC smog.
  • Disposal of organic and inorganic chemical wastes.
  • Throwing of inappropriate man-made objects in nature.
  • Different chemical waste, pesticide and fertilizer mixing to the soil and water.
  • Thermal pollution from power plants.
Pollution from textile industry:
There are mainly five types of (spinning, weaving, knitting, wet processing and apparel or garments) textile industry in Bangladesh that produce air, water, noise, or sound pollution. Generally spinning and weaving industry generate air and sound pollution but wet processing (dyeing, printing, and finishing) industry creates air and water pollution.
 
You can like also: Bangladesh Textile Industry: Present Scenario, Future Prospects and Challenges

The textile industry is a water-intensive industry. The effluent contains a variety of chemicals and dyes, which must be purified before being discharged into the drains or surface water. Depending on the type of contamination and quantity of waste water, different treatment methods offered to clean.

Air pollution:
Ambient air is a mixture of gases i.e. 78% Nitrogen, 20% Oxygen, about 1% Argon, 0.03% Carbon dioxide etc. When there is disturbance in the composition of air due to the particular matter or gases let out from the industries into atmosphere, is considered as air pollution. The particulate matter may be in the form of fine dust, aerosols, fumes and gases in significant quantities.

Causes of air pollution:
Some of the pollutions causing air pollution are sulpher dioxide, metal sulphate, and exhaust gases emitting from poly-condensation, melt spinning process and the fluff generation during spinning and weaving processes. During steam generation process carbon, carbon –dioxide, carbon-monoxide, and sulpher are produced, which cause air pollution.

In order to minimize the risk of industrial diseases among workers, Occupational Safety and Health Authority (OSHA) of USA has specified concentration limitation of dust in the air steam of production rooms for compliance by the concerned industries is bellow in table:

Table-1: Concentration limits of dust in air stream

Process
Limit (mg/m³)
Blow room to speed frame
0.5
Spinning
0.2
Twisting
0.2
Winding
0.2
Warping
0.2
Sizing
0.75
Weaving
0.75
Non-woven
0.5
Hazards of air pollution:
Air pollution is injurious to human being as well as animals. Air pollution creates irritation to eye, respiratory problem, irretation, diminishing visibility, obstruction of sunlight, persistence of fog etc.

The United States Environmental Protection Agency (EPA) uses the following Air Quality Index (AQI):

Table-2: Air Quality Index (AQI)

AQI values
Level of health concern
0 -50
Good
51 - 100
Moderate
101 - 150
Unhealthy for sensitive group
151 - 200
Unhealthy
201 - 300
Very healthy
301 -500
Hazardous

Air Quality Index (AQI)

        IHighILow
I = ------------------------------- (CCLow) + ILow
      CHigh - CLow

Where,
I = Air Quality Index
C = Pollutant Concentration
CLow = Concentration Breakpoint that is < C
CHigh = Concentration Breakpoint that is > C
ILow = Index Breakpoint Corresponding to C low
IHigh = Index Breakpoint Corresponding to C high

In Bangladesh, the air quality standard is set by the Department of Environment (VIDE CLAUSE 12) as bellow:

Table-3: Air quality of Bangladesh:

Area
SPM
S²O
CO
N²O
Industrial and mixed
500
120
5000
100
Commercial and mixed
400
100
5000
100
Residential and rural
200
80
2000
80
Sensitive
100
30
1000
30
Industrial area should not discharge or emit any pollution which may help to exceed the air quality standard in residential, rural and sensitive area.

Noise pollution:
With the progress of industrial growth, noise has become a part of our environment. Development of modern automated machines in textile industries has considerably decreased the physical burden of work and worker but one of the most undesirable and unavoidable product of these machines is noise pollution. High level noise, not only hinders communication between workers also depending upon the level, quality and exposure duration of noise have physical, physiological and psychological effects on workers. It should great concerned about the magnitude of industrial noise exposure.

The common scientific acoustic unit is decibel (db)

It is a ratio expressed as a logarithmic scale relative to a reference sound pressure level.

                                          Intensity Measured
1 decibel (dB) = 10log10 ----------------------------------
                                          Reference Intensity

Source of noise pollution:
In general, there are two type of source of noise generation, which creates noise pollution.

1. Dynamic source: These are due to air jet, international or periodic discharge of gas, fan noise, hydraulic pump noise, and combustion flow generation noise.

2. Mechanical source: These are due to impact of bearings and slide ways, tooth engagement of gears, electrically induced vibration in electric machines, atick-slip motion due to friction and impact generated as a part of machine process.

High noise levels are generally found in the textile process from fiber to fabric (spinning and weaving mill). Noise sources of any textile industrial process may be due to the following reason:
  • Propagation through air (air-bone noise)
  • Propagation through solid (structure-bone noise)
  • Diffraction at the machinery boundaries.
  • Reflection of sound from floor, wall, ceiling and machinery surface.
The noise levels of different departments of textile industry are following:

Table-4: The noise levels of different textile industry

Area
dB
Blowroom
84.8
Carding
89.9
Draw Frame
85.2
Combing
84.4
Simplex
87.2
Ring frame
100
Loom shed
102.1
Hazards of noise pollution:
Workers consistently exposed to the noise level above 85 or even 90dB may reveal permanent hearing loss. In addition to hearing loss, exposure of workers to noise levels of 90-119dB was also found to result in-
  • Cardiovascular and psycho physiologic problem
  • Sleep disorder and headache.
  • Mental fatigue
  • Annoyance, speech interference and reduced alertness.
  • Increased blood pressure, deep body temperature and pulse rate.
  • Speed of performance was impaired significantly by noise.
Control of noise pollution:
  • Noise in spinning section can be reduced by providing elastomeric spindle.
  • Replacement of parts with resilient materials like nylon can reduce the noise of loom.
  • Proper maintenance (machine alignment, gear fitting and lubrication) can reduce the generation of noise during running.
  • Complete enclosures around the room reduce the level of noise of noise from 30-60 dB.
  • Vibration isolators prevent the generation of noise.
  • Damping or foamed coating surface reduce the amplitude of noise.
In Bangladesh, the sound intensity standard is set by the department of environment (VIED RULE 12) as bellow-

Table-5: Sound intensity standard in Bangladesh

Zone class
Day (6am-9pm)
Slient zone
45 dB
Residential zone
50 dB
Mixed zone
60 dB
Commercial zone
70 dB
Industrial Zone
70 dB
Area within 100 meter of hospital, educational institutes and Govt. designated special institute/ establishments are considered as silent zone.

Water pollution:
The majority of the water consumption (72%)takes place in the chemical (wet) processing, i.e. preparing the fabric for dyeing, printing and finishing operations, intermediate washing/ rinsing operations and machine cleaning. Other major uses of water in the textile industries are following:

Water consumption area
Percentage
Wet processing (dyeing, printing, and finishing)
72%
Water treatment for specific purpose
8
Cooling (processing machines, colling tower)
6
Stem generation (boiler feed water)
5
Domestic purpose
8
The specific water consumption for cellulosic fabric processing ranges from 100 to 200 liters/kg of fabric processing, where for synthetic fiber, yarn and fabric irt ranges between 25 to 70 liters/ kg of the product processed.

Mainly two types of effluent (waste water) are generated from wet processing mill. In main dyeing process produces effluent which contains strong chemicle and intensive color, which contain high load of pollutant such as biological oxygen demand (BOD), chemical oxygen demand (COD), and suspended solids (SS). Total organic carbon (TOC) is the amount of carbon bound in an organic compound and is ofter used as a non-specific indicator of water quality or cleanliness of a textile manufacturing industry. In washing and other process produces low to maoderate load of pollutant such as BOD and COD. Absorbable organic halogens (Aox) are also mentainable effuent in textile dyeing and printing.

Effluent characteristics of various wet processing operations are following:

Effluent generation stages
Parameter
pH
COD(mg/1)
BOD(mg/1)
Desizing
5.83- 6.5
10,000 - 1500
1700 – 5200
Scouring
10- 13
1200 - 3300
260 – 400
Bleaching
8.5 -9.6
150 - 500
50 – 100
Mercerizing
8 - 10
100 - 200
20- 50
Dyeing
7 - 10
1000 - 3000
400 - 1200
Wash effluent
After bleaching
8- 7
50 - 100
10- 20
After acid rinsing
6 – 7.6
120 - 250
25 - 50
After dyeing (hot wash)
7.5 – 8.5
300 -350
100 – 200
After dyeing ( acid and soap wash)
7.5 -8.7
50- 100
25-50
After dyeing (final wash)
7 – 7.8
25 -50

Washimg after printing
8 – 9
250 - 450
115 -150
Dye class
Fiber
Degree of fixation
Loss to effluent
Acid
Polyamide
80 -95
5 – 20
Basic
Acrylic
95-100
0 - 5
Direct
Cellulose
70 - 95
5 – 30
Disperse
Polyester
90 - 100
0 -10
Matal complex
Wool
90 - 98
2 – 10
Reactive
Cellulose
50 - 90
10 -50
Sulpher
Cellulose
60- 90
10 - 40
Vat
Cellulose
80 - 95
5 - 20
Textile raw materials contain: natural impurities from cotton, wool, silk etc, Fiber solvents (when chemical fibers are produced by dry- spinning or solvent spinning processes), monomers (caprolactam ex. Polymide 6), (catalysts antimony trixide in polyesters’ fibers), sizing agents (woven textiles esp. cotton and cotton blends), and preparation agents (esp. woven and knitted textiles made of man made fibers).

Effluent in textile industries:
Effluent is an out flowing of water or gas from a natural body of water or from a human-made structure.

Effluent is defined by the United States Environmental Protection Agency as “wastewater - treated or untreated, that flows out of a treatment plant, sewer or industrial outfall. Generally refers to wastes discharged into surface waters.” The Compact Oxford English Dictionary defines effluent as “liquid waste or sewage discharged into a river or the sea.”

Textile wastewater is the prime source of organic contamination regarding pollution within the textile industry. So it is very essential effluent treatment for keep environment safe. I have also published article on effluent treatment in textile wet processing industry.


You can like also: Effluent Treatment Plant Process in Textile Industry

Quality of discharge water:
According to Environmental Conservation Rules 1997 textile industries are classified as Red category industries and therefore an ETP must be designed and constructed to effectively treat the waste water. The treated discharged water from the plant must meet the national effluent discharge quality standard. Discharge quality standard for a composite textile industry are given below:


Parameter
Limit (mg/L)
Total suspended solids
100
BOD
150
Oil and grease
10
Total dissolves solids
2100
Flow of waste water
100 L\Kg of fabric processing
pH
6.5 – 9
Total Chromium
2
Sulfides
2
Phenol compunds
5