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ISSN 2229-5518
1Chandan Kumar Sarkar, 2Swapan Kumar Saha, 3Suman Chowdhury, 4Mohammad Mahbubur Rahman,
5Shahidullah Miah
Abstract— Most of the textile industry discharges the polluted textile waste-water directly into the waterways as the cost of treatment process is high. To minimize the cost, an effective and advanced treatment process has been setup at Mascom Composite Textile Ltd and Dalas Fashion Ltd. at Gazipur, Dhaka. The treatment process consists of a combined process (anaerobic and bio-filtration process) which is mentioned as High Rate Biological Treatment (HRBT) process. This biological treatment process is successfully operating without chemical process. The raw textile waste-water is highly polluted with high level of alkalinity in nature. The pollution parameters were removed successfully with standard quality by using the HRBT process. The ETP treatment capacity was 50,000 Liter/hour. Case study on chemical ETP process has revealed that taka 8.984 million is required for chemical ETP whereas taka 1.784 million for HRBT ETP process. Thus HRBT ETP process has been proved to be highly economical than the Chemical ETP process.
Index Terms: Sustainability, Chemical oxygen demand, HRBT, ETP, RCL, optimizing effluent generation, COD, BOD
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MOST of urban areas in Bangladesh are facing severe long-term aquatic environmental pollution primarily caused by direct discharge of liquid of Textile wastewater in the waterways. High organic loaded wastewater creates environmental pollution. As a result most particularly in the vicinity of urban areas rivers around Dhaka city are found to be severely polluted in Dhaka city. In Bangladesh, there are very few wastewater treatment facilities; mainly due to high costs of treatment. The result is severe water pollution in the Dhaka city, even more during dry season when all rivers become severely polluted. The textile wastewater is a
serious environmental challenge faced by
Bangladesh textile sub sector. A scenario of direct
discharge of textile wastewater to the environment is shown in Figure-1.
Direct discharge of Textile wastewater in the waterways
1Chandan Kumar Sarkar, Associate Prof., Department of Economics, International Fig-1: Direct Discharge of Textile polluted
University of Business Agriculture and Technology, Dhaka-1230, Bangladesh, Email: csarkar@iubat.edu
2Swapan Kumar Saha, Senior Lecturer, Department of Business Administration, International University of Business Agriculture and Technology, Dhaka-1230, Bangladesh, Email: swapanau@yahoo.com.au
3Suman Chowdhury, Lecturer, Department of Electrical and Electronics
Engineering, International University of Business Agriculture and Technology, Dhaka-1230, Bangladesh, Email: suman.kuet@gmail.com
4Mohammad Mahbubur Rahman, Assistant Prof., Department of Physics, International University of Business Agriculture and Technology, Dhaka-1230, Bangladesh, Email: dinar_eic@yahoo.com
5Shahidullah Miah, Professor & Director, Collage of Agricultural
Sciences, Faculty, Collage of Arts and Sciences, InternationaIJlSUERn©iv2e01r4sity of
http://www.ijser.org
Business Agriculture and Technology, Dhaka-1230, Bangladesh, Email:
drshohidullah@iubat.edu
wastewater to the Environment
The textile wastewater contains organic compounds and synthetic chemicals. Certain chemicals which are used in the textile industry cause environmental or health problems. Due to presence of chemicals, it causes instance
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allergic skin reaction or even causes cancer. The major raw material for textile processing is grey
fabric and most of materials consist of cotton and blended fabric. Textile processing employs a variety of chemicals depending on the nature of raw material and products such as; enzymes, detergents, dyes, acids, soda and salt. The textile wastewater is a highly polluted in terms of organic matter and suspended matter such as fibers, grease and chemicals. The textile wastewater is usually hot and alkaline with strong offensive smell and color due to use of dyes and chemicals. Some studies showed that wastewater from textile industry are highly toxic and has inhibitory effects on an activated sludge and nitrification. In the textile wastewater situated with high values of chemical oxygen demand (COD) and biological oxygen demand (BOD).
Most of the developing countries did not maintain any treatment process for wastewater
and some of the countries just follow the
compared to conventional treatment process.
The major objectives of the study are as follows:
i). to compare the treatment efficiency of the
Chemical and HRBT ETP
ii). to verify the cost effectiveness for Chemical and HRBT ETP
iii). Find out the recommended ETP process
based on analysis
Methodology:
This paper is based on investigating selective factories equipped with different types of ETPs. Samples were collected from different sampling points of ETPs. Samples were analyzed for various physicochemical parameters like pH, total dissolved solids (TDS), total suspended solids (TSS), 5 days biochemical oxygen demand (BOD5), chemical oxygen demand (COD), Dissolved oxygen (DO) etc. This study includes test report of Environmental Engineering Laboratory (BUET), Department of Environment (DoE) and Department of Applied Chemistry & Chem. Tech. (DU). Suggestions of ETP executives, operators and designers are also
included in this paper.
traditional methodIs suchJas stabilizinSg ponds for ER
wastewater treatment without applying the
treatment process (de Sousa et al., 1996). Stabilizing pond takes very long time, extensive land area is required, spread a serious noxious smell and affects the air pollution, creates the potential breeding field for mosquitoes which affect seriously the public health and spreads diseases. The Up-flow Anaerobic Sludge Blanket
The sampling design to be used for this survey is a three stage procedure. The first stage sampling unit is industry level the second stage unit is owner, and the third stage unit workers. Sampling size to be determined using the standard formula given below. Total sample size to be around 200.
(UASB) treatment system has been developed first time in Netherlands in 1970s (Lettinga and
𝑡 2
ss =
× 𝑝(1 − 𝑝)
𝐶 2
Vinken, 1980). Thereafter, the intensive use of
UASB system has been developed for wastewater treatment over the past decades in developing countries in the tropical and subtropical regions such as Brazil, Colombia, China, India, and Mexico (Ciftci and Oztiirk 1995, Miah et al.,
2004). The high rate biological ETP is more popular, because;
i). It has high rate of anaerobic treatment capacity.
ii). Treatment efficiency well under mesophilic
temperature condition,
iii). High organic strength wastewater can be
treated,
iv). Relatively simple and low operation cost
v). High organic removal efficiency,
vi). Bio-energy benefit could be obtained through the biogas production and
vi). Excess sludge production is very low
ss = Sample size
t = t-value (e.g., 1.96 for a 95
percent confidence level)
p = Percentage of population picking a choice, expressed as decimal
C = Confidence interval,
expressed as decimal (e.g., .04 =
+/- 4 percentage points)
Data will be gathers by face to face interview using pre-tested structural questionnaire. To develop questionnaire focus group discussions will be required. The critical issues identified in the discussions will be translated into a series of questions to include in the questionnaire. This
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will take some time, with consideration of appropriate wording of questions (in Bangle). Care is also required to ensure that the questionnaire is not overlong. To ensure that the enumerations are fully familiar with the questions, and to check that the questions make sense to target group members, a pre-testing will be done.
In order to carry out descriptive analysis we will employ table, graph, ratio etc. This analysis will prepare foundation for empirical
analysis.
1.1. Why biological treatment is the best method?
1. Economic perspective.
2. Efficiency perspective.
3. Ecological perspective.
1.2. Economic perspective: Effluent treatment with
biological method is very cost-effective compared to other methods because of least operation and maintenance cost due to very low chemical consumption, low labor cost, less sludge treatment and disposal cost. It will be clearly realized by following comparative cost analysis tables.
Table 1: Tentative installation cost of ETPs : 60 m3/hour treatment capacity.
Chlorination
IJ1500 – 2500 Ssq ft 20 E- 25 lac
R45 - 60 lac
Courtesy: ETP Provider- TEXMAC (BANGLADESH) LIMITED.
Table 2: ETP recurring expenditure:
PROCESS | PEAK FLOW m3/hr | CHEMICALS | DOSING RATE kg/day | CONSUMPTION kg/m3 | PRICE tk/kg | COST tk/m3 | TOTAL tk/m3 |
Physico-Chemical 65 m3/hr | Lime | 600 - 650 | 0.38 - 0.42 | 10 - 12 | 3.86 - 5.04 | 15.5 - 22.5 | |
Physico-Chemical 65 m3/hr | 1000 - 1200 | 0.64 - 0.77 | 14 - 16 | 8.97- 12.32 | 1000 - 1200 | 15.5 - 22.5 | |
Physico-Chemical 65 m3/hr | Polyelectrolyte | 8 - 10 | 0.005 - 0.01 | 260 - 280 | 1.33 - 2.80 | 15.5 - 22.5 | |
Physico-Chemical 65 m3/hr | H2SO4 | 250 - 300 | 0.16 - 0.19 | 8 - 12 | 1.28 - 2.28 | 15.5 - 22.5 | |
Biological | 60 m3/hr | H2SO4 (98%) | 150 - 200 | 0.10 - 0.139 | 8 - 12 | 0.83 - 1.6 | 1.5 - 2.0 |
Biological | 60 m3/hr | Polyelectrolyte | 1.5 - 2 | 0.001 - 0.0013 | 260 - 300 | 0.27 - 0.36 | 1.5 - 2.0 |
Biological | 60 m3/hr | Antifoam | occasional | - | 200 - 250 | - | 1.5 - 2.0 |
Biological | 60 m3/hr | Decolorant | occasional | - | 95 - 100 | - | 1.5 - 2.0 |
Biological | 60 m3/hr | Nutrient | occasional | - | 150-300 | - | 1.5 - 2.0 |
Biological | 60 m3/hr |
by the reduction percentage of BOD, COD, TSS,
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TDS, Color and other parameters like chloride, phosphorus, nitrogen, phenolic compounds etc.
Biological effluent treatment plant is highly efficient. Table 4 exposes the comparative degree of efficiency of different active ETPs.
STANDARDIZATION:
Factory type | Composite textile industries. |
ETP treatment capacity | 55 - 150 m3/hour |
Avg. Inlet BOD5 range | 110 – 281 mg/l |
Avg. Inlet COD range | 284 – 480 mg/l |
Avg. Inlet TSS range | 62 – 276 mg/l |
Avg. Inlet TDS range | 240 – 4950 mg/l |
Avg. Coagulant dose (FeSO4) | 583 – 984 mg/l |
Avg. Coagulant dose (Lime) | 330 – 606 mg/l |
Avg. Inlet PH | 6.7 – 11.5 |
Avg. Inlet temperature | 35 – 500C |
Discharging area | Inland surface water. |
1. Biological oxygen demand (BOD5): Amount of
done at 105°C) to leave a solid residue which can be weighed.
electrodes.
- PH Meter: Calibrated pH meter probe is submerged in a sample of the effluent and after stirring gently for a few moments the pH meter should give a stable pH reading.
Filtration of the mixture of solids resulting from combining recycled sludge with influent wastewater in the bioreactor. The MLSS is the weight of the solid divided by the volume of sample.
placing a mixed-liquor sample in a 1 liter
cylinder and measuring the settled volume (SV)
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dissolved oxygen consumed by sample of effluent incubated for five days at 20°C. (Winkler’s method)
equal to the number of milligrams of oxygen that
a liter of sample will absorb from a hot, acidic solution of potassium dichromate.
(Dichromate Reflux method).
3. Total dissolved solids (TDS): -By TDS meter.
- TDS can also be measured by filtration to
remove suspended solids and then evaporation of the filtrate (remaining liquid portion, usually
after 30 minutes and dividing it by the
corresponding sample’s MLSS concentration.
10. Coagulation-flocculation: Jar test: FeSO4, Lime,
Polyelectrolyte are poured into the 1 liter volume jar containing wastewater to identify required optimum dose.
Table 4: Performance analysis of active ETPs.
FACTS | UNIT | *STANDARD | BT | AT | RE % | BT | AT | RE % | BT | AT | RE % |
BOD5 | mg/l | 50/150* | 125 | 65 | 48 | 147 | 69 | 53.1 | 115 | 56 | 51.3 |
COD | mg/l | 200 | 340 | 135 | 60.3 | 290 | 110 | 62.1 | 295 | 153 | 48.1 |
TSS | mg/l | 150 | 170 | 62.9 | 63 | 276 | 80 | 71 | 210 | 53.88 | 74.3 |
TDS | mg/l | 2100 | 1956 | 1795 | 8.2 | 1600 | 1820 | -13.8 | 3045 | 2245 | 26.2 |
DO | mg/l | 4.5 - 8 | 0 | 4.9 | 0 | 5.1 | 0 | 4.9 | DO | ||
PH | - | 6 - 9 | 11.5 | 8.6 | 11.2 | 7.3 | 10 | 7.72 | PH | ||
TEMP | 0c | 40 | 37 | 29 | 41 | 30 | 40 | 29 | TEMP | ||
BT-before treatment value, AT-after treatment value, RE(removal efficiency)= {(BT-AT)/BT}*100
*BOD limit of 150 mg/l implies only with physico-chemical processing.
*Bangladesh standard for wastewater discharge to inland surface water as per ECR 1997. It consists no standard for colour,so this parameter is not mentioned.
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Table: 5
BIOLOGICAL | |||||||||||
FACTS | UNIT | STANDARD | BT | AT | RE % | BT | AT | RE % | BT | AT | RE % |
BOD5 | mg/l | 50 | 110 | 29 | 73.6 | 145 | 19.45 | 86.6 | 281 | 23 | 91.8 |
COD | mg/l | 200 | 320 | 128 | 60 | 304 | 102 | 66.4 | 356 | 174 | 51.1 |
TSS | mg/l | 150 | 130 | 18 | 86.2 | 230 | 54 | 76.5 | 204 | 36 | 82.4 |
TDS | mg/l | 2100 | 4950 | 2010 | 59.4 | 2492 | 1135 | 54.5 | 3200 | 1580 | 50.6 |
DO | mg/l | 4.5 - 8 | 0 | 4.5 | 0 | 4.7 | 0.1 | 4.6 | |||
PH | - | 6 - 9 | 10.5 | 8.03 | 9.76 | 7.69 | 10.3 | 8.1 | |||
TEMP | 0c | 40 | 41 | 35 | 43 | 34 | 50 | 35 |
Table: 6
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Table : 7
CHLORINATION | |||||||||||
FACTS | UNIT | STANDARD | BT | AT | RE % | BT | AT | RE % | BT | AT | RE % |
BOD5 | mg/l | 50 | 230 | 98 | 57.4 | 138 | 44 | 68.1 | 230 | 36 | 84.3 |
COD | mg/l | 200 | 472 | 299 | 36.7 | 352 | 116 | 67 | 480 | 160 | 66.7 |
TSS | mg/l | 150 | 90 | 34 | 62.2 | 180 | 28 | 84.4 | 69 | 56.2 | 18.6 |
DO | mg/l | 4.5 - 8 | 0 | 6.8 | 0 | 4.4 | 0 | 8.5 | DO | ||
PH | - | 6 - 9 | 8.3 | 7.15 | 6.7 | 6.5 | 8.5 | 6.5 | PH | ||
TEMP | 0c | 40 | 43 | 28 | 37 | 28 | 39 | 32 | TEMP | ||
R CL | mg/l | - | 0 | 3 | 0 | 2.95 | 0 | 3.5 | R CL | ||
R CL- Residual chlorine. TEMP- Temperature.
A1,A2,A3-Physico-chemical ETPs. B1,B2,B3- Biological ETPs. C1,C2,C3-Combined chemical- biological ETPs.D1,D2,D3-Chlorination ETPs. Courtesy: Beximco Textile Ltd, Padma
Pollycotton Ltd, DBL Textile Ltd, Interstoff Apparel Ltd, Texurop (BD) Ltd. and rests are confidential. From the above performance analysis table 4 , we can figure out the actual
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scenario of different active ETPs. It is very clear that there are wide variations in average removal efficiency compared to typical efficiency of ETPs. Now take a look at individual efficiency discrimination of important parameters based on performance analysis table 4.
- Figure 9 shows that except chlorination based ETP D1, other COD levels at discharging points are under maximum permissible limit (MPL).
- In combined bio-chemical method the average COD removal efficiency gained the highest value(70.8%) , in biological method 59.1%.
1. Biological oxygen demand (BOD5):
- Figure 9 shows that except chlorination based ETP D1, other COD levels at discharging points are under maximum permissible limit (MPL).
- In combined bio-chemical method the
average COD removal efficiency gained the highest value(70.8%) , in biological method 59.1%.
3. Total suspended solids (TSS)
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*BOD5 limit (150 mg/l) implies only with physico-chemical method.
- From figure 8 we can see that except chlorination based ETP D1, other BOD5 levels at discharging points are under maximum permissible limit (MPL).
- In biological method the average BOD
removal efficiency gained the highest value(84%) compared to other methods.
2. Chemical oxygen demand (COD):
Figure 10 shows TSS levels at discharging points
are under maximum permissible limit in each method.
- Among all methods highest average TSS
removal efficiency (81.7%) found in biological method.
4. Total dissolved solids (TDS) :
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- From figure 11 it is found that before treatment
TDS level was under discharging standard (2100
increase TDS after treatment. Great increase in TDS and zero efficiency by oxidation method with chlorine can be realized from figure 12.
- From table 4 it is found that, DO level of treated effluent is less than discharge standard (4.5- 8 mg/l) in combined bio-chemical method (C1 & C2) and chlorination method (D2). Chlorine based etp D3 presents higher DO (8.5 mg/l) than permissible limit. Lower DO could be a threat to aquatic life. Organisms undergo stress at reduced DO concentrations that make them less competitive to sustain their species within the aquatic environment.
- In chlorination method residual chlorine is
found much higher than permissible limit (0.3
mg/l) which can react with natural organic compounds and produce dangerous disinfection byproducts (DBPs).
By physico-chemical process BOD and COD
removal efficiency was found 50% and 70%
respectively(Nicolaou and Hadjivassilis,1992),
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mg/l) in ETPs A1,A2,C1,C2,C3,D2,D3.
- Physico-chemical based etp A3 and chlorination based etp D1 can not maintain discharging standard.
- It is also found that except biological method,
TDS value increased after treatment in Physico-
chemical based etp A2, combined bio-chemical etp C3 and chlorination based etp D2,D3.
- Biological treatment reduces TDS significantly and satisfy discharging standard.
5. Average removal efficiency (RE%) :
- Figure 12 shows that among four methods, highest efficiency in BOD removal (84%) is obtained by biological treatment. - Combined physico-chemical and biological method reduce COD very efficiently. - Highest average efficiency in TSS removal (81.7%) is obtained by biological treatment. - Biological treatment can reduce TDS with high efficiency. Rest of the methods mostly
BOD and COD removal efficiency was found
90% and 75% respectively by biological treatment [9], In combined biological and physico-chemical method BOD,COD removal efficiency exceeded 90% [7]. Treatment with chlorine gained 55-85% BOD, 55-70% COD reduction efficiency [8]. But analyzing average efficiency of different active ETPs from table 4, it is realized that the actual view is quite different. Physico-chemical as well as highly efficient combined physico-chemical and biological methods can not satisfy discharging standard. Due to high chemical consumption, labor cost, huge quantity toxic sludge disposal problems owners do not run the plant regularly and efficiently. Sometimes it’s just for eye wash. It is also found that, treatment capacity of certain ETPs is lower than incoming effluent stream. So, huge quantity wastewater is discharged without any treatment. But owners are bound to run biological plant 24 hours and 365 days to ensure that the bacteria are provided with sufficient “food” (i.e. wastewater) and oxygen to keep them alive. Brief breaks (for a few hours) in operation will probably do little harm but prolonged shut down will deprive the microorganisms of their food and oxygen and will damage the process [3]. That’s why in actual practice biological plant is running so efficiently maintaining national standard.
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Biological treatment with activated sludge process (ASP) using aerobic bacteria is very eco- friendly. No hazardous chemicals are required, so probability of water contamination is nearly zero. No bad smell is produced. Possibility of reusing treated water for irrigation and fish life which is impossible in other methods. Very low non-toxic sludge is produced containing negligible amount of toxic heavy metals like lead, chromium, mercury etc. Sludge can be utilized as compost fertilizer.
Table 8: Sludge characteristics.
- Bleach and Salt bath recovery.
- Dye substitution-Use low-salt reactive dye and
metal free dyes with high fixation rate.
- Low liquor ratio dyeing machines. Ex: Thence
jet flow dyeing (HK). m:l-1:5
- Cold pad batch dyeing.
- Recycling/reuse of cooling/condensate water.
- Pulsating rinse technology.
- Use biodegradable surfactants such as linear
alcohol ethoxylate.
- Caustic scouring is responsible for 54% of total
BOD, 49% of total COD, 10-20% of total pollution
load. So replace caustic scouring with bio- scouring.
- Replace the use of chlorites and hypochlorites
with hydrogen peroxide.
- Right-first-time dyeing.
- Replace chlorinated solvents with unchlorinated alternatives.
- Organic salt so called CLR is useful to consume half amount of Gluber salt or sodium chloride.
- Use enzyme based H2O2 killer instead of salt
base H2O2 killer.
- Utilize flow segregation system to reduce
pressure on biological treatment unit.
1.7. Constraints of Biological ETP :
- Non biodegradable dye stuffs render the
biological treatment ineffective or less efficient.
- Presence of excessive toxic heavy metals
prevents microbiological growth, hence efficiency fall down.
Courtesy: TEXMAC (BANGLADESH) LIMITED.
Breathing small amount of chlorine gas can be deadly. It is toxic to mucous membrane, damage respirational systems, coughing, chest pains, fluid accumulation in lungs. Moreover, chlorination of effluents such as those from dye houses may produce cancer causing chemicals due to the reaction of chlorine with aromatic chemicals in the effluent. These chlorinated organic chemicals are part of a group of chemicals known as AOX (aromatic organic halides), and are undesirable. It is therefore recommended not to use chlorine in an ETP that treats textile dyeing wastewater.
Both toxicity and volume of textile effluent is directly related to the cost of operation of the effluent treatment plant. Following attempts can be practiced to minimize effluent generation and toxicity:
- Biological treatment is less effective in high
osmotic pressure due to high TDS content in waste water.
- Higher space required.
- Initial investment is higher than other system
due to constructing bigger civil works and
electromechanical equipments.
- High retention time (12 to 72 hours depends on
COD level, COD ≤1000 mg/l need 12 to 24 hours, COD 1500-2000 mg/l required 72 hours typically).
- Low decolorization efficiency of soluble dye
stuffs.
- DO concentration needed for aerobic system
1.5 to 4 mg/l. Generally 2 mg/l is maintained.
Higher DO will not increase biodegradation efficiency hence represent energy wastage. Noted that, aeration possesses 25% of total running cost.
- MLSS concentration should be maintained
within the range of 1500-3000 mg/l for activated sludge method. - PH should be maintained
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between 6.5-8.5 and temperature less than 400C
in biological reactor.
- Sludge settling characteristics should be checked by SVI (sludge volume index) test. Poor settling sludge will result in low concentration of solids in the return activated sludge thus the concentration of microorganisms drops and subsequently F/M (food per microorganism) ratio increases in the aeration tank which results in a reduced BOD, COD removal efficiency. For excellent sludge settling SVI value should be less than 50.
- Add adsorbents like bentonite clay or activated carbon to biological system in order to
eliminate non-biodegradable or microorganism–
toxic organic substances (Pala and Tokat, 2002).
- Higher microbial efficiency can be obtained by
adding nutrient salts like Urea,
Diammonium phosphates (DAP). Nutrients
(food) should be provided while plant shutdown.
This study revealed that textile effluent treatment with biological methods is highly efficient and cost-effective as well as eco-friendly. There are some constraints specially, extremely high initial investment and space requirements which are major obstacles for small and medium scale factories. Government can take efforts to initialize bank loan to establish effluent treatment plants with minimum interest. Further development is essential to treat inorganic compounds by biological process.
[1] Sen, S. and Demirer, G.N. Anaerobic treatment of real textile wastewater with fluidized bed reactor. Water Researce 37,2003: 1868-1878.
[2] Khan M, Knapp J, Clemett A and Chadwick M, Managing Pollution from small industries in Bangladesh, Technical report, Researce for Development, Department for international Develpoment (DFID), 2006.
[3] Mohidus Samad Khan, Knapp J, Clemett A, Chadwick M, Mahbub Mahmood, Moinul Islam Sharif, Managing and Monitoring Effluent Treatment Plants, Page-3,5,7.
[4] Thomas E. (Tom) Schultz, Biological wastewater treatment, October 2005, page 3.
[5] Tanveer Ahmed, Shafi M Tareq, Textile industries in Bangladesh-A rising environmental degradation down the drains, Bangladesh Textile Today, issue 1, January 2008, http://deletionpedia.dbatley.com/w/index.php?
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