ISSN: 1579-4377 TEXTILE WASTEWATER CHARACTERIZATION AND REDUCTION OF ITS COD & BOD BY OXIDATION Muhammad Masud Aslam *, 1, M A Baig 2, Ishtiaq Hassan 3, Ishtiaq A Qazi 2, Murtaza Malik 4, Haroon Saeed 1 1 Post Graduate Student 2 Institute of Environmental Science & Engineering (IESE). National University of Sciences & Technology (NUST), Rawalpindi, Pakistan 3 Ph.D. Student, Department of Farm Management. Faculty of Agricultural Economics and Rural Sociology. University of Agriculture, Faisalabad, Pakistan. 4 Sub Program Manager, National Environment Action Program-Support Program, Ministry of Environment. Govt of Pakistan KEYWORDS Characterization, textile wastewater, wastewater treatment, hydrogen ABSTRACT The main goal of this study was characterization and the COD & BOD reduction of the textile industry processing wastewater. Field analysis has been carried out for the characterization of effluent from textile industry for the evaluation of treatment options. Analysis of four-textile industries effluent was carried out. For COD & BOD reduction three oxidizers were used to compare their treatment efficiency. Using three different oxidants namely Hydrogen,,, and at temperatures 25oC, oc and oc oxidation of high COD textile industry processing wastewater was done. It was found that of these three oxidants calcium proved a suitable oxidant as it reduced COD up to 69% and maximum COD removal occurred at oc and at retention time of 144min. Complete reduction of COD could not be achieved despite varying experimental conditions, i.e. temperature and oxidation duration. Investigations of wastewater after treatment showed a remarkable increase in susceptibility to COD reduction. INTRODUCTION Textile industrial sector is one of the most important and largest industrial sectors of Pakistan with regard to production source of foreign exchange and labour force employment. It alone accounts for 65% of the country export, 46% of industrial production 38% of employed industrial work force and 9% of gross national product (GNP). Textile industry could be termed as backbone of Pakistan economy. The number of industries working in this sector is estimated to be around 67. Karachi has the major share with almost industries and rests are located in Punjab. (Ara, 1999) 1. Environmental problems of the textile industry are mainly caused by discharges of wastewater. Textile processing employs a variety of chemicals, depending on the nature of the raw material and product. Some of these chemicals are different enzymes, detergents, dyes, acids, sodas and salts. Industrial processes generate wastewater containing heavy metal contaminants. Since most of heavy metals are non- * Corresponding Author: Muhammad Masud Aslam M.S. Environmental Engineering. Institute of Environmental Sciences & Engineering (IESE). National University of Sciences & Technology (NUST), Tamiz-ud-Din Road, Rawalpindi Cantt. Pakistan. E-mail: masud92pk@yahoo.com 84
degradable into non-toxic end products, their concentrations must be reduced to acceptable levels before discharging them into environment. Other wise these could pose threats to public health and/or affect the aesthetic quality of potable water. According to World Health Organization (WHO) the metals of most immediate concern are chromium, Zinc, zinc, iron, mercury and lead 2. The fate of these chemicals varies, ranging from % retention on the fabric to % discharge with the effluent. Generally, there are a number of wet processes involved with high requirements for resource inputs, generating several types of wastewater. Textile finishing industry uses large amounts of water, mainly because of washing operations. Therefore, processing wastewaters have high flow rates (SDPI, 1995) 3. Textile wastewater contains substantial pollution loads in terms of COD, BOD, TSS, TDS and heavy metals. The value of these parameters is very high as compared to the values in National Environment Quality Standards (NEQS) set by the government of Pakistan. Very little work has been done on the characterization of textile wastewater and which ever is available is not authentic. Characteristics of textile wastewater are pre requisite for the investigation of treatment options. Also increase in literacy and WTO implication has made environment an important issue in all the industrial sectors and textile sector is major exporter of Pakistan has definitely to comply with ISO 14. In Pakistan there is lack of treatment facilities for effluent treatment due to lack of implementation, shortage of resources and lack of technical facilities and personals (CPP. 1999) 4. Current practice is that effluent is being discharged into streams or canals after retention period of some hours in stabilization pond without any secondary or tertiary treatment. This wastewater has serious negative impact not only on under ground and surface water bodies and land in the surrounding area but also has an adverse effect on the aquatic ecological system. Effluents from textile mills also contain chromium, which has a cumulative effect, and higher possibilities for entering into the food chain. Due to usage of dyes and chemicals, effluents are dark in colour, which increases the turbidity of water body. This in turn hampers the photosynthesis process, causing alteration in the habitat (Pak EPA, 3) 5. Regarding the COD, at industrial wastewater treatment facilities as in tannery wastewater treatment, organic concentration is usually reduced either by adding activated powder carbon during biological treatment or by expensive tertiary treatments (Iaconi, 3) 6. Oxidants especially hydrogen has been used to reduce the COD and BOD of industrial wastewater for many years. H 2 O 2 due to its redox properties find application in bleaching paper pulp, sugar and textile (Bell, 1965) 7. One objective of this study was characterization of textile wastewater for finding treatment option because this baseline information is inevitable for proper treatment and management of waste being generated from textile sector and secondly reduction of COD of wastewater. For this purpose five different oxidizing agents i.e. Hydrogen (H 2 O 2 ), (NaOCl), [Ca (OCl) 2 ], (K 2 Cr 2 O 7 ) and (CaCr 2 O 7 ) were used to reduce COD of textile wastewater. The aim of this study was to Characterize textile wastewater to evaluate treatment options, evaluation of the efficiency of five oxidizing agent in the treatment of wastewater and optimization of the best operating conditions for oxidation process i.e. temperature. MATERIAL AND METHODS All industries were having almost same process i.e. desizing, mercerising, bleaching, dyeing, and finishing of cloth. Some of industries were using canal water and other ground water for their processes, doing alum treatment to reduce turbidity. Average daily water consumption was calculated from the pumping rate while wastewater flow rate was determined with help of weir at the main outlet of industry. Average wastewater consumption varied from m 3 /day to m 3 /day depending upon industry size and production. 85
Composite sampling was carried out after every 3 hours. Samples were collected in sampling bottles and placed in icebox to preserve the characteristics of wastewater. Samples were collected in sampling bottles and placed in icebox to preserve the characteristics of wastewater and were analysed at IESE, NUST laboratory while temperature, ph, electrical conductivity and DO were measured at spot. Textile production involves a number of wet processes that uses large quantities of water and other chemicals. Process wastewater is a major source of pollutants. It is typically alkaline and has high BOD from 7 to 2, mg/l and high (COD), at approximately 2 to 5 times the BOD level. All these processes contribute toward toxicity of the wastewater that needs to be characterized for possible treatment. Wastewater was analysed for the BOD, COD, TDS, TSS, ph, temp, oil & grease, Cu, Zn, Cr using standard methods (Eaton, 1995). The next step was reduction of COD by using three oxidizing agents namely Hydrogen (H 2 O 2 ), (NaOCl), [Ca (OCl) 2 ], (K 2 Cr 2 O 7 ) and (CaCr 2 O 7 ). The COD was determined by using open reflux method (Eaton, 1995). The sample was refluxed with a known excess of potassium for two hours. After digestion, the excess was titrated against ferrous ammonium sulphate. COD of the sample was 4mg/L and BOD was mg/l. As emphasis was also on COD reduction, the sample was then treated with three oxidants. The original Merck hydrogen, sodium, calcium ppotassium and solutions were used for textile wastewater treatment. Exact concentration was determined by standardizing them against a.1n sodium thiosulphate solution. Amount of oxidizing agents required for oxidation were calculated by using stoichiometric calculations. The amount of H 2 O 2 required for COD reduction was as follows 2 H H O + O 2O2 2 2 2 Here for oxidation requirement, 2 moles of hydrogen will produce 1 mole of oxygen. It means 2.13mg of H 2 O 2 would be required to reduce the COD by 1 mg/l. (Awan, 3). Same procedure was adopted for calculation of other oxidants. ml of wastewater sample was taken in a ml Erlenmeyer flask and measured amount of the H 2 O 2 solution was added. The flask contents were then heated for 5,9 and 144 minutes at temperature o C, o C and 25 o C respectively. Then COD of the samples was measured to compare the effects of different retention times and temperature at treatment of textile wastewater. Similarly, same procedural steps were performed for the other four oxidants. RESULTS AND DISCUSSION Table 1 represents the complete picture obtained from the textile wastewater sample analysis. The most frightening values are for COD, BOD and heavy metals (Cr, Cu & Zn) and cause a real threat to the environment (CPP, 1999). 86
Table 1. Parameters obtained from the analysis of actual textile effluent S.No Parameter Wastewater Wastewater Wastewater Wastewater NEQS (Sample A) (Sample B) (Sample C) (Sample D) (mg/l) 1 ph 5.8-1.5 5.6-11.2 5.9-11.5 5.7-1.9 6-1 2 COD 37-455 41-665 395-595 425-618 1 3 BOD 145-19 165-214 158-26 19-236 8 4 TDS 2-44 1985-3864 18-3885 1888-412 3 5 TSS 1-1 195-7 165-865 185-985 1 6 Phenol - - - - - 7 Sulfides 3-12 - - - - 8 Chloride 85 - - - - 9 Cr 2 3.5 4 3-1 Zn 4 4 3 5-11 Cu 2 2 4 3-12 Oil & Grease 15-35 2-45 18-4 15-4 - 13 Sulfate 554 - - - - 14 4 - - - - Average daily water consumption = m 3 /day Source of water = Canal water It is important that the oxidizing agent added should react completely with organic matter of the sample. In order to determine the COD and BOD reduction at a specific temperature and retention time the process was carried out at four different temperatures i.e. 25 o C, o C and o C and three different retention times i.e. 5 min, 9 min and 144 min. It is evident from the results as shown in figure 1a, that maximum COD reduction was achieved by at 25 o C i.e. COD was reduced from 4mg/L to 4 COD Concentration (mg/l) 4 3 1 Figure 1a. Effect of Retention Time on COD Removal at 25 o C 87
3 BOD concentration (mg/l) 1 Figure 1b. Effect of Retention Time on BOD Removal at 25 o C 154 mg/l as compared to H 2 O 2 where reduction was up to 237mg/L when the retention time was 144 min. In case of BOD the maximum BOD reduction was achieved by and BOD of effluent reduced to 78mg/L from mg/l at retention time of 144 min and this COD & BOD reduction rate decreased as the retention time was decreased to 5 min (Figure 1b). 4 COD Concentration (mg/l) 4 3 1 Figure 2a. Effect of Retention Time on COD Removal at o C When temperature was increased to o C, it was observed that mg/l by at retention time 144 min and 158mg/L at retention time of 5 min. While COD reduction by Hydrogen Peroxide 27mg/L at 144 min and 215mg/L at 5 min (Figure 2a). 88
3 BOD concentration (mg/l) 1 Figure 2b. Effect of Retention Time on BOD Removal at o C In case of BOD, the maximum BOD reduction was also achieved by calcium and BOD of effluent reduced to 148mg/L from mg/l at retention time of 144 min while in case of Hydrogen Peroxide the BOD reduction was 143mg/L at 144 min and 87mg/L at 5min (Figure 2b). Maximum COD & BOD reduction is observed at temperature of o C. COD reduction of textile wastewater was 98mg/L at retention time of 144min and 143mg/L as the retention time was reduced to 5min. Similarly, BOD reduction was 67mg/L from mg/l by use of hydrogen at retention time of 144min and temperature of o C (Figure 3a & b). 4 COD Concentration (mg/l) 4 3 1 Figure 3a. Effect of Retention Time on COD Removal at o C It was observed from the results shown above that maximum COD & BOD was achieved by calcium at all three temperatures. Reason for this maximum reduction was due to availability of two (OCl - ) per formula of Ca (OCl) 2 for oxidation of organic matter in textile processing wastewater. In addition, it was observed that maximum COD & BOD reduction was achieved at o C as compared to o C and 25 o C because temperature facilitates the oxidation process. 89
3 BOD concentration (mg/l) 1 Figure 3b. Effect of Retention Time on BOD Removal at o C In any case, % efficiency of the oxidants might not be achieved because the whole amount of oxidant added in wastewater may not be available for the oxidation of organic matter (Sreeram, 1998) 7. Some amount of oxidant might have been used for the oxidation of heavy metals (Cr, Cu & Zn) present in wastewater (James, ) 8. Second reason for this is that sulfides present in wastewater might be oxidized to sulfates by reaction with the oxidant added for the oxidation process. One disadvantage of using Hydrogen Peroxide is that it interferes in ultimate COD & BOD of textile wastewater after treatment (Sreeram, 1998). Because the un-reacted oxidant present in wastewater contributes toward COD, so it is necessary to add appropriate amount of the oxidant in order to avoid presence of un-reacted oxidant in wastewater prior to COD determination. It was found that is cost-effective and easy. CONCLUSIONS Results from this study show that textile effluents are high in toxicity not only for human beings of surroundings but also a serious threat to ground and surface water recourses. As Faisalabad is agricultural and canal irrigated area it is possible that wastewater might have entered in food chain. It is urgently required that industries should continuously monitor textile effluents and take necessary actions to properly treat wastewater prior their disposal to water bodies and save already depleting natural water resources. It is recommended that proper legislation should be done for all quality parameters of wastewater and should be implemented and monitored regularly. REFERENCES 1. Ara, S. (1999). Textile wastewater treatment by coagulation process. http://www.cpp.org.pk/etpirpt/textilesectorreport.pdf 2. World Health Organization, Geneva, Guidelines for drinking Water Quality, 1984. 3. SDPI (1995) Environmental examination of the textile industry in Pakistan, project on technology transfer for sustainable industrial development, Islamabad: SDPI. 81
4. Cleaner Production Program (CPP)(1999). Revised national environmental quality standards (NEQS). http://www.cpp.org.pk/legal/revisedneqs.pdf 5. Year Book 2-3, Pakistan Environment Protection Agency http://www.environment.gov.pk/organo/epayb23.pdf 6. Iaconi, C. D. (3). http://www.ensic.u-ncy.fr/costwwtp/work_group/wg4/rome/di_iaconi_abs.pdf 7. Bell, T. E. (1965). Encyclopedia of Polymer Science and Technology, Interscience, New York, P. 428. 8. Sreeram, K, J, et al. (1998) use of Hydrogen Peroxide for Tannery Wastewater Treatment. Journal of Scientific & Industrial Research; 57, 64-69. 9. James, M, G, et, al. (). Recovery of chromate from electroplating sludge. Waste Manage Res; 18, 38-385. 811