Our biosphere is under constant threat from continuing environmental pollution. Impact on its atmosphere, hydrosphere, and lithosphere by anthropogenic activities cannot be ignored.
Man-made activities on water by domestic, industrial, agriculture, shipping, radio-active, aquaculture wastes; on air by industrial pollutants, mobile combustion, burning of fuels, agricultural activities, ionization radiation, cosmic radiation, suspended particulate matter; and on land by domestic wastes, industrial waste, agricultural chemicals, and fertilizers, acid rain, animal waste have negative influence over biotic and abiotic components on different natural eco-systems.
Some of the recent environmental issues include greenhouse effect, loss in bio-diversity, rising of sea level, abnormal climatic change, and ozone layer depletion, etc.
In recent years, different approaches have been discussed to tackle man-made environmental hazards. Clean technology, eco-mark and green chemistry are some of the most highlighted practices in preventing and or reducing the adverse effect on our surroundings.
Among many engineering disciplines – Civil Engineering, Mechanical Engineering, Electrical Engineering, etc., Textile Engineering has a direct connection with environmental aspects to be explicitly and abundantly considered. The main reason is that the textile industry plays an important role in the economy of the country like India and it accounts for around one-third of total export.
Out of various activities in the textile industry, chemical processing contributes about 70% of pollution. It is well known that cotton mills consume a large volume of water for various processes such as sizing, desizing, scouring, bleaching, mercerization, dyeing, printing, finishing and ultimately washing.
Due to the nature of various chemical processing of textiles, large volumes of wastewater with numerous pollutants are discharged. Since these streams of water affect the aquatic ecosystem in a number of ways such as depleting the dissolved oxygen content or settlement of suspended substances in anaerobic condition, special attention needs to be paid.
Thus a study on different measures which can be adapted to treat the wastewater discharged from textile chemical processing industries to protect and safeguard our surroundings from possible pollution problem has been the focal point of many recent investigations. This communication highlights such studies carried out in the area of textile effluent treatment.
Sources and Causes of Generation of Textile Effluent
The textile industry involves a wide range of raw materials, machinery and processes to engineer the required shape and properties of the final product. Waste stream generated in this industry is essentially based on water-based effluent generated in the various activities of wet processing of textiles.
The main cause of generation of this effluent is the use of a huge volume of water either in the actual chemical processing or during re-processing in preparatory, dyeing, printing and finishing. In fact, in a practical estimate, it has been found that 45% material in preparatory processing, 33% in dyeing and 22% are re-processed in finishing [1].
But where is the real problem? The fact is that the effluent generated in different steps is well beyond the standard and thus it is highly polluted and dangerous. This is demonstrated in Table 1.
| Property | Standard | Cotton | Synthetic | Wool |
|---|---|---|---|---|
| pH | 5.5 – 9.0 | 8-12 | 7-9 | 3-10 |
| BOD, mg/l, 5 days | 30-350 | 150-750 | 150-200 | 5000 – 8000 |
| COD, mg/l, day | 250 | 200-2400 | 400-650 | 10,000 – 20,000 |
| TDS, mg/l | 2100 | 2100-7700 | 1060-1080 | 10,000 – 13,000 |
| Table 1. Properties of Waste Water from Textile Chemical Processing | ||||