Analysis Of WasteWater Treatment By Aerobic Process, Discharged During Pre-Treatment Operations Of Cotton Textiles .

OR

Optimized aeration time during biological treatment of cotton textile wet processing effluent by Aerobic process

Synthetic textile wastewater treatment through activate sludge process

ABSTRACT

New Eco labels for textile products and tighter restrictions on waste water discharges are forcing textile wet processors to treat process water and chemicals before being discharged to receiving waters. In this study laboratory scale activated sludge process unit was developed with an idea to analyze biological treatment of synthetic textile effluents, by aerobic process. Synthetic effluent comprises of waste, collected from pre treatment processes i.e. desizing, scouring and bleaching. Removal efficiency of pollutants was recorded before, during and after treatment in terms of COD, BOD, pH , TDS and Turbidity. These parameters were studied after every 6 hours interval up to 60 hours retention time at two aeration flow rates of 5 and 7 l/min. For all processes removal %age of BOD and COD at both flow rates ranges between 55 to 92% , which indicates the removal of almost all biodegradable organic matter for this type of treatment. Optimized aeration times at different flow rates are also establish.

KEYWORDS

Textile pre-treatment processes, synthetic waste water, Biological treatment, Aerobic process, COD, BOD.

1. INTRODUCTION

Textile wet processing units consumes large volume of water for various processes such as Sizing, Bleaching, Mercerization, dyeing, Printing, Finishing and Washing [1, 2]. Due to the nature of various chemical wet processing, large volumes of waste water with numerous pollutants are discharged through these industrial units.[3,4] Which not only affects the Aquatic Eco-system in number of ways but also give rise to many organic and inorganic toxic pollutants in environment [5]. The toxic effects of dyestuffs and other organic compounds, as well as acidic and alkaline contaminants, from industrial establishments on the general public are widely accepted. Increasing public concern about environmental issues has led to closure of several small-scale industries [6]. New Eco-labels and discharge limits of industrial waste water effluents are subjected to regulations which are getting more restricted with time. [7,8]. This

waste water must have to treat in order to reduce their biological and chemical load before being discharge to streams, rivers or oceans, as organic compounds cause deficiency of oxygen in receiving water bodies and have a direct effect on aquatic life[9,10].

Various types of high rate anaerobic-aerobic water treatment techniques are currently available including high rate bioreactors and integrated anaerobic-aerobic bioreactors [11]. Activated sludge treatment of wastes is also an effective and economic way of reducing organic pollutants from Municipals and industrial waste water [12, 4].

This study was planned to assess the effectiveness and efficiency of activated sludge reactor Simulator and to generate a systematic and reliable data that will help to design an indigenous textile waste water treatment system.

2. MATERIALS AND METHOD

2.1 Preparation of synthetic effluent:

Synthetic textile (wet processing) waste water was prepared from Pre-treatment operations i.e. (desizing, scouring, and bleaching processes), where sized cotton fabric was processed at all steps with textile auxiliaries as per standard recipes of Clariant’s textile chemicals. Two high temperature dyeing machines were used for all processes at Textile engineering department of Mehran University Jamshoro.

Effluent 1 was collected from desizing operation, where sizing material (starch) on fabric was removed by enzymes [13]. Desizing carried out with Chemicals i.e. Bactosol MTN 4g/l, Imerol PCLF 1g/l, NaCl 4g/l at 70 0C for 45 minutes.

Effluent 2 comprises of oil, waxes, dust and other hydrophobic impurities, since during scouring all natural and additive impurities were removed from the cotton fibers [14]. Scouring carried out with caustic soda2%, Imerol PCLF 0.5 g/l, Sirrix 2UD 2g/l at 100 0C for 60 minutes. Uses of high concentrations of NaOH also require neutralization of wastewater [15].

Effluent 3 comprises of waste water collected from bleaching Bath. Bleaching process removed natural pigments from substrates [16], with the help of hydrogen per oxide 3g/l, caustic soda 3g/l, Sifa 0.5g/l, Sirrex 2UD 1.5 g/l, Imerol PCLF 2g/l at 90 0C for 30 minutes.

Effluent 4 combine waste water from all process that are full define above at 1:1

2.2 Fabrication of aerobic simulator

For the treatment of textile effluent a stainless steel batch reactor Simulator was fabricated according to design specification, mentioned in figure 1.Total capacity of reactor Simulator was 10 liters with 4 liters hydraulic capacity. Fine air diffuser was used to disperse air inside the reactor Simulator.

Collected synthetic waste water from pre-treatment process’s were treated one by one and also combined at 1:1 in aerobic batch reactor Simulator at two flow rates of 5 and 7 liters/min with hydraulic retention time up to 60 hours. Grab sampling technique was used and samples were collected at the interval time of 6 hours.

To evaluate treatment efficiency, parameters mentioned in table No. 1, were analyzed by APHA (American Public Health Association) standard test methods before and after treatment.

3. RESULTS AND DISSCUSSIONS

Synthetic wastewater samples were collected and characterized. Results obtained before any treatment are mentioned in table No. 2 which shows that all parameters’ values exceeded the standards given in the National Environment Quality Standards (NEQS). Consequently imposes serious threat to the environment. The minimum and maximum values for Chemical Oxygen Demand (COD) are 2310 and 4185 mg/l and for Biochemical Oxygen Demand (BOD) are 255 and 1244 mg/l respectively. The pH of effluent varied from 7 to 12. Turbidity ranged from 9 to 49(NTU). Total Dissolve Solids (TDS) lies between 2790 and 14600 mg/l.

Results obtained with respect to treatment of desizing process effluent mentioned in Figure No. 2, shows that BOD and COD were decreased with continuous aeration at both flow rates. Optimized values for theses parameters were obtained at hydraulic retention time of 24 hours with aeration flow rate of 5 l/min and 18 hours with flow rate of 7 l/min. removal percentage of BOD and COD at flow rate of 5 l/min were 80% and 30% respectively and at flow rate of 7 l/min were 79% and 30% respectively at their optimized retention time. Removal %age of BOD is higher than COD. This is for the reason that desizing waste water contains water soluble natural sizes as starch etc, which is easily biodegradable, as compared to organic compounds that may contain slowly-biodegradable organics[17]. Values of TDS were increased with respect to continuous hydraulic retention time. This is because of pH values, as TDS increases with decreasing pH towards acidic side [18].

Outcomes observed after treatment of waste water obtained from scouring process are shown in figure No. 3. According to results obtained removal %age of BOD and COD at continuous aeration flow rate of 5 l/min and 7 l/min are 64, 55%, and 64, 58% respectively. Little lowering removal efficiency as compared to other waste treatments, refers to the lesser biodegradability of

chemicals used in the process. Optimized aeration time observed at flow rates of 5 l/min and 7 l/min were 42and 24 hours respectively. Higher pH values, due to the presence of NaOH (strong alkali) in effluent were observed.

After treatment of waste water collected from bleaching bath results obtained are shown in figure No. 4. It was observed that, removal %age of BOD and COD at aeration flow rates of 5 and 7 l/min were 55, 92% and 56, 88% respectively. Optimized aeration time at these flow rates were 42 and 30 hours respectively. Higher COD removal efficiency in less time found as compared to BOD which confirms the decomposition of bleaching agent to oxygen and acetic acid which is highly biodegradable [19].

Figure No. 5 shows the results obtained after treatment of combined waste water from all processes at same ratio. Optimized retention time experienced at aeration flow rates of 5 and 7 l/min were 48 and 36 hours. Removal %age of BOD and COD at flow rates of 5 and 7 l/min were 68, 82% and 67, 78% respectively.

4. CONCLUSION

Following conclusions were drawn after treating synthetic wastewater collected from pretreatment processes, in lab scale by activated sludge reactor Simulator.

For all processes removal %age of BOD and COD at both flow rates of 5 and 7 l/ min. ranges between 55% to 92% and optimized aeration time lies between 18 to 47 or 48 hours. After observing results of all processes and combined waste water treatment, it has been concluded that biological treatment is more effective for reducing pollution load from cotton textile combined waste water.

TABLE NO. 1. STANDARD TESTING PARAMETERS

S. No. Parameters Standard Test Methods1 pH 4500 H+ B Electronic Method2 Total Dissolved Solids (TDS) Conductivity TDS Meter HACH 446003 Biological Oxygen Demand(BOD) 5210B 5 day BOD Test

4 Chemical Oxygen Demand (COD) 5220D Closed Reflex, Calorimetric Method

5 Turbidity (NTU) Photometric Method

TABLE NO. 2 CHARACTERISTICS OF SYNTHETIC TEXTILE WASTEWATER BEFORE TREATMENT

S.# ProcessTesting Parameters

BOD(mg/l) COD(mg/l) pH TDS(mg/l) Turbidity(NTU)

1 Desizing 936 3643 7 4200 9

2 Scouring 1244 3295 12 8310 49

3 Bleaching 255 2310 12 2790 30

4 Combine 935 4185 12 14600 35

Fig:

1

Schematic Setup of Aerobic Simulators

FIGURE NO.2 RESULTS OF DESIZING PROCESS WASTE WATER TREATMENT.

FIGURE NO.3 RESULTS OF SCOURING PROCESS WASTE WATER TREATMENT.

FIGURE NO. 4 RESULTS OF BLEACHING PROCESS WASTE WATER TREATMENT.

FIGURE NO. 5 RESULTS OF COMBINED WASTE WATER TREATMENT.

REFRENCES

1. Das, S., “Textile Effluent Treatment- A Solution to the Environmental Pollution”,

Malaysian Journal of Analytical Sciences, Volume 11, No. 11, pp. 400-406, 2007.

2. Hendrickx, I. and Boardman, G. D., “Pollution Prevention Studies in the Textile Wet

Processing Industry” P.h.D. Thesis, Department of Environmental Quality, Virginia,

1995.

3. Ahmed, A., “Biological Treatment of Cotton Textile Wet Processing Effluent by Aerobic

Process”, M.E Thesis, Mehran University of Engineering and Technology, Jamshoro,

2013.

4. Vilaseca, M., Gutierrez, M. C., crimau, V. l., Mesas, M. L., Crespi, M., “Biological

Treatment of a Textile Effulant after Electrochemical Oxidation of Reactive Dyes”,

Water Environment Research, volume 82, No. 2, pp. 176-182, 2010.

5. Akram, M., Ashraf, M., Munawar H., Salam,,A. H., and Zeeshan, A.,“Impact

Assessment of Sewerage and Industrial Effluents on Water Resources, Soil, Crops and

Human Health in Faisalabad”, Pakistan Council of Research in Water Resources, 2006.

6. Babu, B. R., Parande, A. K., Raghu, S., and Kumar, T. P., “Cotton Textile Processing:

Waste Generation and Effluent Treatment”, The Journal of Cotton Science, volume 11,

No.3, pp. 141–153, 2007.

7. Mortula, M., “Removal of TDS and BOD from Synthetic Industrial Wastewater via

Adsorption”, International Proceedings of Chemical, Biological and Environmental

Engineering, volume 41, 2012.

8. Vandevivere, P. C., Bianchi, R, Verstrecte, W.,” Treatment and Reuse of Waste Water

from Textile Wet-Processing Industry”, Jjournal of Chemical Technology and

Biotechnology, Volume 72, No. 4, pp. 289-302, 1998.

9. Mahar, R. B., Yue, D., and Nie, Y., “Biodegradation of Organic Matters from Mixed

Unshraded Municipal Solid Waste Through Air Convection Before Land Filling”, Air

and Waste Management Association, Volume 57, pp. 39-46, 2007.

10. Santos, D., Madrid, A. B., Do bok, M. P., Stans, F.A.M, Van lier, A. J. M, Cervantes,

J.B, “The Contribution of Fermentative Bacteria and Methanogenic Archaea to Azo Dye

Reduction by Thermophilic Anaerobic Consortium”, Enzyme Microbial Technology,

volume 39, pp. 38-46, 2006.

11. Chan, Y. J., Law, D. G., Hassell, D. G., “A Review on Anaerobic-Aerobic Treatment of

Industrial and Municipal Waste Water”, Chemical Engineering Journal, Volume 155, pp.

1-18, 2009.

12. Growther, L. and Meenakshi, M., “Biotechnological Approaches to Combat Textile

Effluents”, The Internet Journal of Microbiology, Volume 7, No. 1, pp. 1-7, 2008.

13. Iqbal, M. K., Nadem, A. and Iqbal, T., “Biological Treatment of Textile Wastewater by

Activated Sludge Process”, Journal of the chemical Society of Pakistan, Volume 29, No.

5, pp. 397-400, 2007.

14. Punzi, M., Mattiasson, B., Jonstrup, M., “Treatment of Synthetic Textile Wastewater by

Homogeneous and Heterogeneous Photo-Fenton Oxidation”, Journal of Photochemistry

and Photobiology A: Chemistry, Volume 248, pp. 30–35, 2012.

15. Abdelgadir, A., “EMS-Case Study on Wet Processes,” MS Thesis of Cleaner Production,

Academy of Sciences Engineering Researches & Industrial Technologies Council, Sudan,

2008.

16. Chaparro, T. R., Pires, E. C., “Anaerobic Treatment of Cellulose Bleach Plant

Wastewater: Chlorinated Organics and Genotoxicity Removal” Brazilian Journal of

Chemical Engineering, volume 28, No. 4, 2011.

17. Friedler, E., Kovalio, R., and Galil, N.I., “On-Site Grey water Treatment and Reuse in

Multi-Storey Buildings”, Water Science Technology, Volume 51, No. 10, pp. 187–194,

2005.

18. Hussain, M. Z., Mostafa, M. G., “Aerobic Treatment of Pharmaceutical Wastewater in a

Biological Reactor”, International Journal of Environmental Sciences, Volume 1, No. 7,

pp. 1797-1805, 2011.

19. Rott, U., and minke, R., “Overview of Waste Water Treatment and Recycling in the

Textile Processing Industry”, Water Science Technology, volume 40, pp. 137-144. 1999

40 Minimum references are used