'Sequential Coagulation Studies for Primary Treatment of Textile Process Effluent Instead of Acid Neutralization'


By: B.V. Kulkarni, Dr. S. V. Ranade and Dr. A. I. Wasif


Abstract


Sequential coagulation studies were carried out for primary treatment of textile effluent from different processing units at Ichalkaranji by using jar test apparatus. Various combinations of Alum, Ferric chloride and Lime, were used for the studies. It has been observed that at all the pH values, maximum (65-90%) reduction in COD, (80 to 85%) in colour and TDS removal upto (30-40%) of the actual process effluent is possible to achieve. As far as heavy metal(s) removal is concerned at the said pH, it can be seen that the maximum removal of Ni and Pb upto approx. 99% was observed. Findings of other heavy metals removal, i.e. Cd (96%), Cr (total) (80-90%), Cu (90%), Zn (80 to 90%) and Fe (80%) was observed in various combinations of Alum, Ferric chlorine and Lime, for primary treatment. Such primarily treated textile effluent can be easily treated by biological means.


Key Words - textile effluent, sequential coagulation.


Introduction


With the ecology being the password of the world today, the country has to focus on environment friendly products and production processes. The textile industry is one of the oldest and second largest industry next to agriculture providing bread & butter to over 20 million people. About 700 textile mills are located mainly at Ahmedabad, Mumbai, Coimbatore, Delhi, Kanpur, Ludhiana and Ichalkaranji. It is one of the leading foreign exchange earners through export of textiles. Therefore, it has to focus its attention on production of environmental friendly textiles and effluent treatment.

Textile industry can be broadly classified in to spinning, weaving, processing and garmenting. The spinning, weaving and garmenting are the dry processes and do not contribute to water pollution. However, it is the wet processing which contributes significantly to water pollution. The pollutants generated mainly from processing of cloth, which consists of desizing, scouring, bleaching, mercerising, dyeing, printing and finishing operations.


The wool processing consists of scouring, stock-dying, carding, fulling, washing, carbonising, dyeing, bleaching, and brightening. Such processing operation involves the use of more than 8000 chemicals e.g. acid, alkali, oil, detergents,dyes,S02, H202 etc. and they generate pollutants which ultimately meet the receiving water bodies reflecting in terms of pH, colour, dissolved solids, suspended solids, acidity or alkalinity, BOD, COD, phenolics, chlorides, oil and grease, sulphate and sodium etc.

Some chemicals such as dyes, detergents, etc. need extra care for proper treatment and disposal of the textile process effluent. Recent research and surveys indicate large quantity of water for specific processes. About 230 Iitres of water are required for processing 1 Kg. of fabric. While similar other investigations indicate that the unit consumes 360 Itr. of water/kg of cloth.


With the advancement of ecofriendly processing the water requirement has been brought down to about 150 It/kg for 100% cotton fabrics and about 90 It. for 100 % polyester fabrics. Summarily, it can be seen that there is no definite figure for water consumption in the textile mills and it varies from mill to mill and one process to other.


 

However, mills having complex processes may consume more water. So an average mill producing 60,000 meter of fabrics/day is likely to discharge approximately 1.5 million It/day, of effluent and out of the total water consumed in the textile mills, around 38 % is used for bleaching, 16 % for dyeing, 8 % for printing, 14 % for boilers and 24 % for miscellaneous uses.

 

On an average an independent textile process, processing polyesters/cotton woven goods discharges about 2 to 6 lacks of liters of effluent per day depending upon the production, process employed and the type of machinery used. Thus for the processing of one kg. of 100% cotton fabrics about 125 liters of effluent is generated where as during the processing of 100% polyester fabrics about 65 to 70 liters of effluent is generated.

 

The composition of textile mill effluent is complex and fluctuating in nature. The characteristics of effluent depend on the nature of the textile products and the raw-materials used. It has normally high pH and dissolved solids and persistent chemicals such as dyes, dye - intermediates and detergents etc.

 

Conventional treatment can remove the pollution load to a considerable extent. However, such type of treatment can not ensure complete treatment of such effluents in all cases. It needs special attention for pre-treatments. One such investigation has been conducted in KIT laboratories for the treatment of alkaline textile process effluent. Coagulants such as lime, ferric chloride and alum were used for the sequential coagulation followed by biological treatment.


Materials and Methods


Samples were collected in grab, composite mode, preserved and transported to laboratory for various experiments as well as foe analysis methodology.

For coagulant system jar test apparatus study was performed for primary treatment of textile process effluent by various coagulants and for their treatment efficiencies. Freshly prepared coagulants viz. alum, ferric chloride and lime water with known dosing were used for 60 seconds mixing time. After complete mixing, one hour settling time was allowed for each set.


Results & Discussion


It has been observed that at all the pH values, maximum (65-90%) reduction in COD (80 to 85%) in colour and TDS removal upto (30-40%) of the actual process effluent is possible to achieve.


As far as heavy metal(s) removal is concerned at the said pH, it can be seen that the maximum removal of Ni and Pb upto approx. 99% was observed. Findings of other heavy metals removal, i.e. Cd (96%) Cr (total) (80-90%), Cu (90%), Zn (80 to 90%) and Fe (80%) was observed in various combinations of Alum, Ferric chloride and Lime, for primary treatment.


Conclusion

It can be concluded that sequential coagulation is helpful in removal of primary pollutants to considerable extent. Such primarily treatment textile effluent can be easily treated by biological means.


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Acknowledgement


The authors expressed their gratitude to the following persons for providing facilities and encouragement throughout the studies.


  1. The Principal, KIT's College of Engg., Kolhapur
  2. The Principal, DKTE's Textile and Engg., Institute, Ichalkaranji
  3. Head CFC, Shivaji University, Kolhapur
  4. Head, Department of Biotechnology, KIT's College of Engg. , Kolhapur


 

References


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  1. Ian L. Pepper & Charles P/ Gerba Environmental Microbiology, A Laboratory Manual Second Edition 2004.


  1. Metcalf & Eddy Wastewater Engineering Treatment & Reuse Tata McGraw-Hill Fourth Edition 2003.


  1. Nelson N. & Nemerow N. L., Theories & Practices of Industrial Waste Treatment. Addison Wesley Publishing Co. 1963.


  1. Padma Vankar Textile Effluent NCUTE Publication I.I.T. Delhi. 2002.


  1. P.B. Jhala, M.M. Vyas, K.. Subrahmanyam Water & Effluents in Textile Mills. ATIRA Publication 1981.


  1. P.K. Goel, Water Pollution, Causes, Effects and Control New Age International Publishers 1997.


  1. Rao M. N., Dutta A. K. Waste water Treatment Second Edition. Rational Methods of Design & Industrial Practices. Oxford & IBH Publishing Co. Ltd. New Delhi. 2003


  1. Textile Committee, Govt. of India, Ministry of Textiles, Best Management Practices for Pollution Prevention in Textile Industry.1997.


About the Authors:


B.V. Kulkarni is associated with Environmental Engg., KIT's College of Engg., Kolhapur, Maharashtra, India


Dr. S. V. Ranade is Retd. Prof. & Head of the Dept. of Civil Engg. Walchand College of Engg. Sangli, Maharashtra, India


Dr. A. I. Wasif is associated with DKTE's Textile & Engg. Institute, Ichalkaranji, Dist. Kolhapur 416115 - Maharashtra, India