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An Investigation on Quality Characterization and Magnitude of Pollution
Implications with Textile Dyeing Industries’ Effluents using Bleaching Powder
M. A. Hannan, M. A. Rahman and M. F. Haque
Dept. of ME, Dhaka University of Engineering & Technology (DUET), Gazipur, Bangladesh ABSTRACT
This paper describes the outcomes of an investigation on the harmful effects of waste water effluents coming from
textile dying industries. A comprehensive study was accomplished through treatment of sample wastes from nine
dyeing industries around Gazipur city. Because of high molecular weight and complex chemical structures showing
low level of biodegradability, direct deposition of these effluents into sewage networks produce disturbances in
treatment processes and exert pollution loads on water bodies. Emphasis was given on the oxidation process for
removal of color and other pollution loads. The color removal efficiency was studied by adding different amount of
oxidizing agent. Specifically, bleaching powder was used as an oxidizing agent and the parameters considered in this
study was pH value, turbidity, total suspended solids (TSS), chemical oxygen demand(COD), and biochemical oxygen
demand(BOD). At an optimum level of pH 8.8, the doses of oxidizing agent were determined by batch study. Using the
dose of oxidizing agent 500 mg/l, the color removal efficiency of waste water was found to be 90%. It was also seen
that the pollution loads (BOD5, COD, and TSS etc.) were reduced to a tolerable limit by using bleaching powder in
oxidation process. The color decreased after treatment with bleaching powder consequently increases the total solid in
the final effluents. The effects of using various concentrations of bleaching powder on TSS, BOD and COD were
studied which have been presented in this paper.
The study was focused on the pollution implications of effluents from
textile industries around the city, because of the risk of human exposure and environmental degradation by these
massive discharge effluents.
KEYWARDS: Total Suspended Solid, Biochemical Oxygen Demand, Chemical Oxygen Demand, Suspended Solids,

Total Dissolved Solids.

1. INTRODUCTION

regard to dissolved solids, pH, BOD, COD, sometimes, heavy metals and color of effluent (Chen et al, 2005). Textile manufacturing sector is among the major industrial water users. A lot of chemicals are added to the process for The textile industry is distinguished by the use of raw cleaning and dyeing purposes. Obviously, the wastewater materials which determines the volume of water required effluents from textile mills contain considerable amounts of for the process as well as wastewater generated. Production hazardous pollutants, where heavy metals are very may be from raw cotton, raw wool, and synthetic materials that can be shown by a flow diagram in Fig. 1. The nine common. Most of the effluents from the textile industries major industries were selected for study which are mainly are discharged untreated into rivers, as a result, a raw cotton-based. In this type of production, slashing, considerable portion of the available water is being polluted bleaching, mercerizing, and dyeing are the major water by the textile effluents and about two thirds of diseases are consumption activities as well as waste water generation. related to water-borne diseases in Bangladesh. The textiles Oil and grease, ammonia, supplied, and color are the mill actually represents a range of industries with potential air pollution sources from these effluents. operations and processes as diverse as its products Meteorological conditions which include wind speed and (Nosheen et al, 2002). Industrial pollution is one of the annual average temperature (United States Environmental problems presently facing Bangladesh and several efforts Protection Agency, USEPA, 2002) are important factors. It are being vigorously pursued to control it in various confirms that the high temperature during the long dry industries to see that people live in a disease free season increases the potential of the discharged effluents environment. Effluent generated by the textile industries is from the textile mills to pollute air in the environment. one of the important sources of pollution increasingly When the effluents are discharged into the river, the heavy stringent effluent discharge permit limitations have been metals present are absorbed in the river’s soil and put into effect. The textile industry generally has difficulty sediments during the dry season, and water evaporation in meeting wastewater discharge limits, particularly with could expose them to the environment. High TSS and Dhaka University of Engineering & Technology, Gazipur Fig. 1: Cotton Fabric Production and Associated Water Pollutants
Dhaka University of Engineering & Technology, Gazipur TDS detected could be attributed to the high color (from processes. Industrial emission and waste effluent generated the various dyestuffs being used in the textile mills) and from factories are associated with heavy disease burden they are the major sources of heavy metals. Increased heavy (WHO, 2000 and 2002) and this could be part of the metal concentrations in river sediments increases reasons for the current shorter life expectancy, 61.4 years suspended solids concentrations. During the dry season, the both for male and female in the country (WHO, 2003) occasional dust re-suspension introduces these metals into when compared to the developed nations. Some heavy the atmosphere along with the particulates. metals contained in these effluents (either in free form in the effluents or adsorbed in the suspended solids) from the They constitute health problems in the form of air pollution industries have been found to be carcinogenic (Tamburlaine with the particulates. In addition to these, the products of et al, 2002), while other chemicals equally present are reactions these metals into the atmosphere along with the poisonous depending on the dose and exposure duration particulates. With this, they could constitute health problems in the form of air pollution. In addition to these, These chemicals are not only poisonous to humans but also the products of reactions between some of the chemicals found toxic to aquatic life (WHO, 2000 and 2002) and present in the effluents (Soldan, 2003) that may be toxic to potential sources of food contamination (Novick, 1999). the environment. Removal of the pollutants from these Ammonia is harmful to fish or other aquatic organisms at free (un-ionized) concentration of 10- 50 μg/L or higher pH effluents is the only sure way of safer environment and this value and the sulphide in the effluent are of environmental can be achieved by proper treatment of effluents to the concern (WHO, 2000 and 2002) because they can lead to poor air quality of an area if not properly taken care of thus The most important measure of water quality is the becoming threat to humans, vegetation, and materials. The
dissolved oxygen (DO) (Peirce et al, 1997). The low level same is applicable to pH that has been identified to raise of DO recorded could result in the non maintenance of health issues if water available for human use is not of the
required pH level (WHO 1993). Textile industries are
conditions favorable to the aerobic organisms. This could major sources of these effluents (Ghoreishi and Haghighi lead to anaerobic organisms taking over with the resultant 2003) due to the nature of their operations which requires creation of conditions making the water body uninhabitable high volume of water that eventually results in high wastewater generation. They are one of the largest water Hydrogen sulphide is formed under conditions of deficient oxygen in the presence of organic materials and Strong influence on the potential impacts associated with sulphate(WHO, 2000). This could be a possible reason for textile manufacturing operations due to the different characteristics associated with the effluents is shown in the high sulphide measured in the effluents analyzed. Table 1. Specific water use varies from 60-400 L/kg of Hydrogen sulphide is formed under conditions of deficient fabric, depending on the type of fabric (Bruggen et al, 2001 oxygen in the presence of organic materials and sulphate (WHO, 2000). This is the reason for high sulphide measured in the effluents under analysis. High alkalinity Table 1: Effluent Characteristics of Textile Industry
increases with wastewater strength. It shows the capacity of waste waters to neutralize acids, but it is undesirable. Pollutant
Effluent Composition
Heavy metals in the wastewaters could be of negative impact to the environment, trace heavy metal contamination of an area to industrial effluent (Sekhar et al, 2003). The negative impacts from textile mills effluents could be felt as far as all the regions covered by the River basin, the main receptor of these effluents. High heavy metal concentration has been found in these rivers Desizing
attributed this to industries. The textile industry generally faces difficulty in meeting wastewater discharge limits, Sodium Hypochlorite, Cl2, NaOH, H2O2, acids, particularly, with regard to dissolved solids, pH, BOD, COD, sometimes, heavy metals and color of effluent (Chen Bleaching
et al, 2005) Effluents from textile industries contain different types of dyes, which because of high molecular weight and complex chemical structures, that show low Mercerizing
Hence, direct deposition of these effluents into sewage Dyestuffs Urea, reducing strongly colored, networks, produce disturbances in biological treatment Dhaka University of Engineering & Technology, Gazipur acidity, oils and grease, sulphide, and coliform bacteria (EPA, 1974). Bangladesh Environmental Protection Agency also supported these and demands for their proper Printing
monitoring in the textile effluents in the country (PEPA, 2000). Textile effluents are high in BOD due to fiber residues and suspended solids (EPA, 1998). They can contaminate water with oil & grease, and waxes, while Source: (Bruggen et al, 2001 and EPA, 1998) some may contain heavy metals, such as, chromium, lead, copper, zinc and mercury (PEPA, 2000). Dyeing process 2. LITERATURE REVIEW
usually contributes chromium, lead, zinc and copper to Ever since the beginning of humankind, people have been wastewater (Benavides, 1992). Copper is toxic to aquatic using colorants for painting and dyeing of their plants at concentrations below 1.0 mg/l while surroundings, their skins and their clothes. Until the middle concentrations near this level can be toxic to some fishes of the 19th century, all colorants applied were from natural (Sawyer and McCarty, 1978 and Nergis et al, 2005). origin. Inorganic pigments such as soot, manganese oxide, There are a lot of different kinds of industries in hematite and ochre have been utilised within living Bangladesh. All these industries have different waste memory. Palaeolithic rock paintings, such as the 30,000 problems. An grading of index of the level of pollution is year old drawings that were recently discovered in the Chauvet caves in France, provide ancient testimony of their application. Organic natural colorants have also a timeless Table 2: Water pollution source and their ranking in
history of application, especially as textile dyes. These dyes are all aromatic compounds, originating usually from plants Pollution
Industry
(e.g. the red dye alizarin from madder and indigo. Pollution
Synthetic dye manufacturing was started commercially in 1856, when the English chemist W.H. Perkin, in an attempt to synthesise quinine, obtained it, instead of a bluish substance with excellent dyeing properties that later on became known as aniline purple, Tyrant purple or mauveine. Perkin, an 18-year old boy, patented his invention and set up a production line for mass production. Consequently, in the beginning of 20th century, synthetic dyestuffs almost completely supplanted the natural dyes. 2. METHODOLOGY
Key environmental issues associated with textile manufacture are use of water, its treatment and disposal of All field meters and equipment such as Visible liquid effluent. The risk factors are primarily associated Spectrophotometer, COD Digestion Reactor, BOD Track , with the wet processes, such as, desizing, scouring, Conductivity Meter, pH Meter , Conductivity Meter, bleaching, mercerizing, dyeing and finishing. Desizing, Dissolved Oxygen Meter, Electronic Balance , Digital scouring and bleaching processes produce large quantity of Titrator Incubator, Desiccators, Water De-ionizer, Atomic wastewater. Treatment for color removal can increase the Absorption Spectrometer were checked and calibrated risk of pollution. For instance, treating azo-dyes results in according to the manufacturers specifications. The pH production of amines which could be a greater meter was calibrated using buffers of pH 4.0, 7.0 and 10.0; environmental risk than the dye itself. It is reported that TDS/conductivity/salinity meter was calibrated using the textile effluent is very low in terms of LC50 and exhibit potassium chloride solution provided by the manufacturer; very high toxicity with acute toxicity unit (ATU) levels the spectrophotometers were checked for malfunctioning between 22 and 960 (Novarro et al, 2001). by passing standard solutions of all the parameters to be Dyes are contributing to overall toxicity at all processing measured; Blank samples (deionized water) were passed stages. Also, dye baths could have high level of BOD, between every three measurements of effluent samples so COD, color, toxicity, surfactants, fibers, turbidity, and as to check for any eventual contamination or abnormal contain heavy metals (EPA, 1998). They generally response of the equipment. Reproducibility of results was constitute a small fraction of total liquid effluent, but may regularly checked by carrying out periodic analysis of contribute a high proportion of total contaminants. It is to aliquots collected from one sample. Fieldwork involved be note that textile effluents are highly colored and saline taking samples; points at which effluents discharge into that contain non-biodegradable compounds, and are high in drains for laboratory analyses. Two liters of each sample Biochemical and Chemical Oxygen Demand (BOD, COD). was taken in plastic containers and one liter per sample was It is reported that the presence of metals and other dye taken in glass containers for BOD, Oil and Grease compounds inhibit microbial activity and some cases may determination. The samples were taken during the period of cause failure of biological treatment system (Wynne et al, heaviest activity corresponding to the highest volume 2001). USEPA reported that the pollution parameters in textile effluents are suspended solids, BOD, COD, nitrogen, the worst situation. There was a need for sample phosphate, temperature, toxic chemicals (phenol), preservation and for all the parameters; recommended chromium and other heavy metals, pH-value, alkalinity and methods were used (APHA. 1998 and HACH, 1997). In- Dhaka University of Engineering & Technology, Gazipur situ measurements for some of the parameters, pH and water or in which visual depth is restricted. Turbidity may temperature were carried out using portable conductivity be caused by a wide variety of suspended substance of meter. Determination of other parameters viz. TDS, TSS, various sizes ranging on size from colloidal to coarse color, ammonia, and Sulphide was carried out in the particles, depending on the degree of turbulences. For laboratory using the spectrophotometers. Heavy metals (Cr, filtration, turbid water is not suitable as it causes quick Cu, Fe, Mn, Zn) determination was carried out using clogging of filter bed which necessaries the use of pre- Atomic Absorption Spectrometer (AAS), while mercury treatment plant. Turbidity is also an important parameter in was determined by mercury hydride (vapor generation) disinfection of process. Disinfections are usually system. In determination of concentration of oil & grease, accomplished by means of chlorine, ozone, or chlorine the gravimetrical method was used after solvent extraction dioxide. To be effective, there must be contact between the with n-hexane. Chemical oxygen demand was determined agent and the organisms to be killed. However, in cases of by the dichromate digestion method while biochemical when turbidity is caused by dyeing wastewater, many of the oxygen demand was determined by the respirometric pathogenic organisms may be encased in the particles and protected from the disinfectant. Hence USEB has placed a maximum level of 0.5 to 1.0 units of turbidity, depending 3. EXPERIMENTAL INVESTIGATION
on the disinfection process used, as the maximum amount 3.1 Determination of color contents
is allowable in public water supplies. According to Bangladesh environmental preservation act (1997), Most water available to us is colored to some extent, due to drinking water standard for turbidity is NTU. The current the presence of various impurities (i.e. iron and manganese standard method for measurement of turbidity upon the in association with organic matter from decaying instruments that was employed the principles of vegetation). Impurities may be in the colloidal form in nephelometry. In this instrument a light source illuminates water or it may be in suspended state. Color caused by the sample and one or more photoelectric detectors are used dissolved and colloidal matters, is called apparent color. with a readout device to indicate light. It is customary to Dyeing waste water may show color due to the presence of use a particular formazine suspension as a standard, or organic matters. Even the water is not harmful, it is not commercially available preparations may also be used. preferred by people for aesthetic reason. Also, disinfection by chlorination of waters containing natural organics (which produces color) result in the formation of problems which is major concern in water treatment. So it is important to limit the color of water for domestic supplies. According to Bangladesh environment preservation act (1997) drinking water standard for color is 15 units. Color is usually expressed in platinum-cobalt units (Pt-Co Units) which is based on the intensity of color produced by a solution of Platinum and Cobalt salts which is approximately yellow-brown in natural color. The sample had been compared with the color discs and the color is determined. The color changes with the change in Fig. 3: Concentration of bleaching powder vs suspended
concentration of bleaching powder (Fig. 2), At a certain level of concentration of bleaching powder, the color When using formazine standard, 40 NTU are equivalent to removal rate is more or less same and is about 90 percent. 40 Jackson candle turbidity units (JTU). Turbidities, as low as 0.02 NTU, can be determined by this procedure provided that water with sufficiently low turbidity can be obtained for use in instrument calibration. Samples with turbidities grater than 30 to 40 NTU were used. The turbidity is then determined by multiplying the measured factor. The turbidity of various samples were ploted and presented in Fig. 3, which shows that suspended solids(SS) increases with the increase in concentration of bleaching powder. The variation is not linear, it is parabolic in nature, which means that the SS increases very gradually with the variation of Concentration of bleaching powder (mg/l)
3.3 Determination of Biological Oxygen Demand (BOD)
Fig. 2: Concentration of bleaching powder versus
percentage of color removal at first stage. When biodegradable organic matters are released into a 3.2 Determination of Turbidity
water body, microorganisms (esp, bacteria) feed in the wastes, breaking down to simpler organic and inorganic The term “turbid” is applied to water containing suspended substances. When this decomposition takes place in an matter that interfaces with passages of light through the aerobic environment, it produces non-objectionable, stable Dhaka University of Engineering & Technology, Gazipur end products like CO2,SO2, PO4 and NH3, when in this If the white precipitate is obtained there was no dissolved process dissolved oxygen (DO) of water is used. oxygen in the sample and there is no need to proceed Organic matter + O2 → CO2 + H2O + new cells +Stable products further. A brown precipitate shows that oxygen is present In this process, insufficient oxygen environment is and reacted with the manganous hydroxide. The brown sustained or, when oxygen is exhausted, an anaerobic precipitate is manganese basic oxide and formed as: decomposition occurs when various sets of microorganisms carry out the decomposition anaerobically producing highly Upon the addition of (sulphuric) acid, this precipitate is Organic matter + CO2 → CH4 + New cells + unstable products. This compound immediately reacts with potassium iodide The amount of oxygen required by micro-organisms to liberating in the typical iodine (blue) coloration of the oxidize organic wastes aerobically is called biochemical oxygen demand (BOD). It may have various units, but most often it is expressed in mg/l of oxygen of wastewater. The The quantity of iodine liberated by this reaction is total amount of oxygen that will be required for bio- equivalent to the quantity of oxygen present in the sample. degradation is an important measure of the impact that a The quantity of iodine is determined by titrating a portion given waste stream would have on the receiving water of the solution with a standard solution of sodium body. Dissolved oxygen is the most commonly used thiosulphate solution. 2Na2S2O4 + I2 = Na2S4O6 + 2NaI. indicator of the general health of a surface waterbody. If The experimentally obtained values of BOD were ploted DO goes below 4 to 5 mg/L due to decomposition of against the amount of bleaching powder per litre was organic wastes, the survival of water organisms begin to go plotted in Fig. 4, which depicts how it varies with respect to down, when anaerobic condition exists and when higher the variation of concentration of bleaching powder solution, life forms are killed or driven out. Then the noxious the variation is not linear, but slightly parabolic in nature. condition, including floating sludge, bubbling, odorous The figure indicates that there is an inverse relation of BOD gases, and slimy fungus growth prevails. with the concentration of bleaching powder solution, i.e., The biochemical oxygen demand (BOD) determination is the BOD decreases as the concentration of bleaching an empirical test in which standardized laboratory producer are used to determine the oxygen requirement of wastewater, effluents and polluted waters. It has become a standard practice to simply measure and report the oxygen demand over a 5-days period, realizing that the ultimate oxygen demand for complete degradation of organic matter is considerablly higher and may take a much longer time to determine in the laboratory. The 5 days BOD or BOD the amount of oxygen consumed by micro-organisms during the first 5 days of biodegradation. The simplest form of BOD test would be involved putting a sample of wastewater into a stoppard bottle, measuring the dissolve Fig. 4: Concentration of bleaching powder verses BOD.
oxygen (DO) of the sample at the beginning of the test and again at the end of five days. The difference in DO would 3.4 Determination of Chemical Oxygen Demand
5 of the wastewater. Light must be kept out of the bottle to keep algae from adding oxygen by photosynthesis and the stopper is used to keep air form The chemical oxygen demand (COD) test is widely used as replenishing DO from outside. To standardize the a means of measuring the organic strength of domestic and procedure, the test was run at a fixed temperature of 200C. industrial wastes. This test allows measurement of a waste Since the oxygen demand of typical waste is several in term of the total quantity of oxygen required for hundred milligrams per liter, and since the saturated value oxidation to carbon dioxide and water. The test is based on of DO for water at 200C is only 9.1 mg/l, it is usually the fact that all organic compounds, with a few exceptions, necessary to dilute the sample to keep the final DO above can be oxidized by the action of strong oxidizing agents zero. If during the five days of experiment, the DO drops to under acidic conditions. During the determination of COD, zero, then the test is invalid since more oxygen would have organic matter is converted to carbon dioxide and water been removed more than had been available. The five day regardless of the biological assimilability of the substance. For example, glucose and lignin are both oxidized completely. As a result, COD values are grater than BOD The relation involves the Winker Method where the values, especially when biologically resistant organic dissolveD oxygen (DO) determinations are presented. matter (e.g., lignin) is present. One of the chief limitations of BOD test is its inability to differentiate between Manganous sulphate reacts with potassium hydroxide in the biologically oxidizable and biologically inert organic alkaline potassium iodide solution to produce a white matter. In condition, it does not provide any evidence of the rate at which the biologically active martial would be stabilized under conditions that exit in nature. The Dhaka University of Engineering & Technology, Gazipur determination can be made in about 3 hours rather than the and 48.8oC, which are higher than the set limit by the 5 days required for the measurement of BOD. For this National Environmental Quality Standards (BNEQS, 2000), reason, it is used as a substitute for the BOD test in many the pH range 7.85-11.52, calls for more attention. The instances. instead of using potassium dichromate or effluents were basic in nature. The colors of all the potassium permanganate, bleaching powder was used as the oxidizing agent in the determination of COD. Potassium effluents were very high in concentration. They ranged permanganate is selective in the reaction and attacks the from 612-4637 Pt-Co with effluents from nine textile mills carbonaceous and not the nitrogenous matter. In any having values above 100 Pt-Co. With the exception of method of measuring COD an excess of oxidizing wastewater from some other textiles that have a TDS agent(bleaching powder) was used to ensure that all organic concentration of 3040 and 1056 mg/L the other effluents matter was oxidized as completely as possible within the had TDS levels higher than the acceptable limit of 3500 power of the reagent. It is therefore, necessary to measure the excess in some manner so that the actual amount can be determined. For this purpose, a solution of reducing agent (e.g. ammonium oxalate) is usually used. The experimentally obtained variation of COD is presented in Fig. 5 which indicates how it varies with the variation of concentration of bleaching powder solution. Fig. 6: Amount of suspended solid present before and after
Fig. 5: Concentration of bleaching powder vs COD.
4. SAMPLE COLLECTION AND TESTING
Waste water was collected from different nine industries effluents. The concentration of dye was 100 mg/l. Bleaching powder was used as an oxidation agent having chlorine content of about 30%. The bleaching powder was of commercial grade. 0.1 N NaOH and 0.1 N H used for increasing or decreasing the pH of waste water respectively. In the first stage pH value of waste water was kept constant (pH = 8.8) but dosages of oxidizing agent Fig. 7: Amount of BOD before and after the treatment of
(bleaching powder) was varied. The dosage was varied from 100 mg/l to 750 mg/l. 2.5 gm of bleaching powder dissolved in the 500 ml distilled water. The concentration of bleaching powder of this solution was 5000 mg/l. The first stage of the batch studies were done by jar test apparatus with 100 ml of waste water in the different beakers and then adding the stock solution of bleaching powder 10 ml, 25 ml, 50 ml and 75 ml to obtain the concentrations of bleaching powder which were 100 mg/l, 250 mg/l, 500 mg/l and 750 mg/l respectively. In the second stage bleaching powder concentration was kept constant (500 mg/l) but pH of waste water was varied. Variations of pH were done by adding the acid (0.1 N Fig. 8: Amount of COD before and after the treatment of
2SO4) or alkali (0.1 NaOH) in the waste water as required. 4. APPRAISAL OF RESULTS
Though the total suspended solid level in the effluent Generally the effluents characteristics need to be properly samples from some Textile mills could be acceptable, the monitored for better environmental protection. All the effluents from the other Textiles had TSS levels more than 2 folds of the acceptable limit. Both measured BOD and textile mills had their effluent temperatures between 34.7oC COD levels also exceeded the set limits by about 2 and 10 Dhaka University of Engineering & Technology, Gazipur folds respectively. Apart from two textiles, the sulphide kinetic energy of some molecules. These molecules with levels in the effluents were high (1.58-3.14 mg/L) as higher kinetic energy will be able to escape the against the standard limit of 1 mg/L. Except one Textile. intermolecular attractive forces in the liquids and enter the Ammonia levels were within limits in almost all effluents gas phase. Evaporation increases as the liquid temperature 6.82-34.8 mg/L. Oil and grease was detected in the effluents from five Textiles, were below the 10.0 mg/L increases due to the increased number of molecules with NEQS limit while in four Textiles has higher than the the necessary kinetic energy level to escape. This confirms limit. Heavy metals concentrations were higher than the set that high temperature of city especially during the long dry limits (Table 3) in the effluents. Effluents’ samples had season could increase the potential of the discharged copper levels range between 0.07-5.14 mg/L as against effluents from the textile mills to pollute air in the lower set (less than 1.0) limit, while chromium was ranging environment. High color associated with these effluents should be adequately treated before discharge. The impacts Two Text have high concentration of 1.57 and 1.07, set limit is 1.0 mg/L (Table 3), in six of the textile effluents. of temperature on diffusivities both in the air and water Similarly Mn, Fe, and Zn concentration are within the (USEPA, 2001) could influence emissions of both limits except in two. Mercury was not detected in all the ammonia and sulphide detected in the effluents while volatilization of oil and grease that could be induced by the same high temperature could introduce organic compounds 6. RESULTS AND DISCUSSION
into the environment thus polluting the air. High TSS and TDS detected could be attributed to the high color from the The negative impacts from textile mills effluents could be various dyestuffs being used in the textile mills and they felt as far as all the regions covered by the river basin, the may be major sources of the heavy metals. Increased heavy main receptor of these effluents. High heavy metal metals concentrations in river sediments could increase concentration has found in these rivers attributed this to suspended solids concentrations. During the dry season, the industries. The textile industries which are some of the occasional dust re-suspension could introduce these metals most active in the city could be one of the sources and this into the atmosphere along with the particulates. With this, confirms the potential dangers associated with high copper they could constitute health problems in form of air levels detected in the effluents analyzed. Detected pollution. Some of the vapors formed above have great effluents’ parameters could form gaseous emission and potential to nucleate thus becoming particulate problem to particulates the potential threat they pose to the the environment. In addition to these are the products of environment especially around Shitalakhma, Turag and reactions between some of the chemicals present in the Buriganga river basins calls for stringent control measure. effluents (Soldan, 2003) which may be toxic to the Of the five world air pollution episodes, three of them were environment. Removal of the pollutants from these 1930, 1948, and 1952, happened around riverbanks (EPA, effluents is the only sure way of safer environment and this 2008) supported by temperature inversions. The most can be achieved by treatment to required level. important measure of water quality is the dissolved oxygen (DO) (Peirce et al, 1997). The low level of DO recorded could result in the non maintenance of conditions favorable 7. CONCLUSION AND RECOMMENDATION
to the aerobic organisms. This could lead to anaerobic
The qualities of effluents studied were grossly below the set
organisms taking over with the resultant creation of limits by the Bangladesh Environmental Protection Agency conditions making the water body uninhabitable to gill- and some world bodies like the World Health breathing aquatic organisms. Hydrogen sulphide is formed Organization(Table 3 & 4) in all textile mills. The effluents under conditions of deficient oxygen in the presence of are not uniform in characteristics and this may make it organic materials and sulphate (WHO, 2000). This could be extremely difficult to use a central effluent treatment plant. a possible reason for the high sulphide measured in the Lower levels of some of these parameters in Text. 9 with effluents analyzed. The high levels of BOD are indications effluent treatment plant, when compared to the other four of the pollution strength of the wastewaters. They also Text (with no effluent treatment plant) indicate that a indicate that there could be low oxygen available for living uniform characteristics is attainable for or all the effluents organisms in the wastewater when utilizing the organic if a measure of treatment is introduced at textile mills level. matter present. High COD levels imply toxic condition and Lower levels of parameters could make the proposed the presence of biologically resistant organic substances central treatment plant cheaper to maintain even at greater (Sawyer and McCarty 1978). The settleable and suspended efficiency. The results also show that air quality of the area solids are high and this will affect the operation and sizing covered by the entire city could be negatively affected by of treatment units. Solids concentration is another both the gaseous emissions and particulates which could be important characteristic of wastewater (Lee and Lin, 1999). released from the effluents. Meteorological conditions of At any temperature, liquids can evaporate due to higher the area are strong influencing factors. Rainfall appears in Dhaka University of Engineering & Technology, Gazipur Table 3: Physico-chemical characteristics of Textile Mills’ Effluents
Analytes,
Tex.1 Tex.2 Tex.3 Tex.4 Tex.5 Tex.6 Tex.7 Tex.8 Tex.9
512.371.32 1,87.02.7 2,474.03.58 1,283.02.4 1.0761.9 9640.86 8720.95 7350.67 65.01.55 Temperature (0C) 40 487.84.8 41.73.00 43.55.2 45.77.9 44.62.7 42.81.64 46.33.4 41.92.8 34.72.2 13.610.73 11.230.52 11.041.04 11.530.95 11.441.04 12.281.76 12.760.83 11.040.6 7.750.28 58012 4079.6 78614.6 6596.4 5944.8 6185.6 73112.7 6728.3 1174.9 212018.61 65013.7 243024.6 219017.9 1586120 176423.0 21849.7 179227 2388.26 2453.7 1352.5 4714.8 4622.9 2835.2 3479.6 4094.2 3891.8 491.64 713020.6 420013.41 14808.96 384812.68 30407.6 397011 27644.6 392616 105614.8 26.01.2 28.30.97 8.90.4 7.70.84 14.272.8 8.03026 17.60.5 9.21.4 4.60.63 12.720.24 20.011.5 12.80.6 41.960.8 18.260.4 21.931.7 53.22.4 34.81.6 6.820.43 1.640.04 0.170.02 1.580.14 1.090.06 2.480.36 1.830.4 2.360.28 3.140.24 0.10.03 0.050.003 0.010.002 1.140.04 1.060.05 2.630.16 1.840.7 3.870.62 1.060.2 0.760.03 227532.6 61212.9 353723.54 63731.7 467326 116413.8 16908 201418.6 1034.6 2.51.24 2.91.03 3.081.14 1.20.8 2.640.8 1.30.24 1.50.8 2.40.2 7.01.6 Tex: Textile Mills 1 to 9, Unites in mg/l unless otherwise stated.
Table 4: Physico-chemical characteristics of Textile Mills’ Effluents
Analytes
Tex.1 Tex.2 Tex.3 Tex.4 Tex.5 Tex.6 Tex.7 Tex.8 Tex.9
Chromium 1.0 1.570.24 0.970.11 0.180.03 1.070.17 0.7250.02 0.8630.046 0.4990.04 0.9620.028 0.50.06 0.960.03 2.040.28 1.160.17 5.140.53 0.830.016 1.670.08 0.7240.02 1.190.04 0.070.004 Manganese 1.5 0.950.11 1.650.24 1.180.16 0.370.04 0.9460.02 1.3740.16 0.8490.11 0.7680.05 0.860.02 2.140.18 1.450.06 2.090.13 1.750.06 1.390.43 1.820.27 1.8960.25 1.6270.18 1.970.11 6.480.85 4.330.69 2.360.17 3.080.24 4.390.37 2.840.18 3.9720.44 4.7540.36 2.190.08 Tex: Textile Mills 1 to 9. ND: Not detected in ppm. Units in mg/ 1 unless otherwise stated. ND: Not defined
Dhaka University of Engineering & Technology, Gazipur city around July-August and retreats in September. The REFERENCES
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