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Changes in physicochemicalcharacteristics of wastewater carryingcanals after relocation of Calcuttatannery agglomerates within the EastCalcutta Wetland ecosystem (a Ramsarsite)Utpal Singha Roy a , Abhishek Roy Goswami b , Anulipi Aich b , B.Chattopadhyay b , S. Datta c & S. K. Mukhopadhyay da Department of Zoology , Durgapur Government College , JNAvenue, Durgapur , 713214 , West Bengal , Indiab Ecotoxicology Laboratory , Government College of Engineeringand Leather Technology , LB III, Salt Lake, Kolkata , 700 098 ,Indiac Department of Chemical Engineering , Jadavpur University ,Kolkata , 700032 , Indiad Department of Zoology , Hooghly Mohsin College , Chinsurah ,712101 , West Bengal , IndiaPublished online: 07 Mar 2013.

To cite this article: Utpal Singha Roy , Abhishek Roy Goswami , Anulipi Aich , B. Chattopadhyay ,S. Datta & S. K. Mukhopadhyay (2013) Changes in physicochemical characteristics of wastewatercarrying canals after relocation of Calcutta tannery agglomerates within the East Calcutta Wetlandecosystem (a Ramsar site), International Journal of Environmental Studies, 70:2, 203-221, DOI:10.1080/00207233.2013.774810

To link to this article: http://dx.doi.org/10.1080/00207233.2013.774810

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Changes in physicochemical characteristics ofwastewater carrying canals after relocation ofCalcutta tannery agglomerates within the EastCalcutta Wetland ecosystem (a Ramsar site)

UTPAL SINGHA ROY*†, ABHISHEK ROY GOSWAMI‡, ANULIPI AICHzB. CHATTOPADHYAY‡, S. DATTAx AND S. K. MUKHOPADHYAY{

yDepartment of Zoology, Durgapur Government College, JN Avenue, Durgapur 713214, WestBengal, India; zEcotoxicology Laboratory, Government College of Engineering and Leather

Technology, LB III, Salt Lake, Kolkata 700 098, India; xDepartment of Chemical Engineering,Jadavpur University, Kolkata 700032, India; {Department of Zoology, Hooghly Mohsin College,

Chinsurah 712101, West Bengal, India

Calcutta Leather Complex (CLC) near Bantala, Calcutta was constructed in the late 1990s. Theostensible purpose was to bring together the widely dispersed and haphazardly located tanningindustry of Calcutta in a single location and to facilitate hazardous waste management by establish-ing a Common Effluent Treatment Plant. Unfortunately, for a number of reasons, the CLC is not yetfully operational. Further, the continued operation of illegal tanneries outside CLC has worsenedmatters. This study was undertaken to assess the physicochemical conditions of wastewater carryingcanals within the East Calcutta Wetland (ECW) ecosystem (a Ramsar site) with special reference tothe relocation of tanneries. Results revealed a great change in the values for physicochemical condi-tions; most changes were statistically significant (p< 0.05) when compared with available data, pre-vious to tannery relocation. Moreover, the amelioration efficiency of ECW ecosystem was found tobe mostly disturbed both by the illegal tannery operations and shifting of tannery agglomerates.

Keywords: East Calcutta Wetland ecosystem; Tannery agglomerates; Calcutta Leather Complex

1. Introduction

The East Calcutta Wetland (ECW) ecosystem (lat 22°33′–22°40′N, long 88°25′–88°35′ E)lies in the eastern fringes of the city of Calcutta (recently renamed Kolkata), in West Ben-gal, India. Throughout the year, the ECW ecosystem, receives industrial run-off fromalmost 6000 large- and small-scale industrial establishments (including tanneries) alongwith the domestic sewage of more than 14million inhabitants of the Kolkata Metropolitanarea [1]. For almost 100 years, effluents from tanneries and leather industries have heavilycontaminated the wetland environment of Calcutta. Apart from tannery wastes, untreatedeffluents from several other small-scale industrial establishments such as pottery, electro-plating and battery, rubber and pigment manufacturing units are also mixed up with the

*Corresponding author: Email: srutpal@gmail.com

International Journal of Environmental Studies, 2013Vol. 70, No. 2, 203–221, http://dx.doi.org/10.1080/00207233.2013.774810

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run-off. The wastewater, after being mixed with municipal sewage, flows via the StormWater Flow canal (SWF) for nearly 40 km eastwards and is finally discharged into the Kul-tigong River (figure 1).

The composite wastewater (estimated ca. 50,000m3 d�1) plays an important role in theECW ecosystem as the discharges are used in pisciculture after stabilization in an informalindigenous method [2]. This wastewater is also used as irrigation water in agriculture(mainly rice and vegetables) and horticulture [3–8]. The ECW ecosystem covers around12,771 ha area that includes 286 wastewater-fed fishponds (locally known as Bheris).

Figure 1. Study sites (Sites 1–4) along major wastewater carrying canals within ECWs.

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Spread over 3832 hectare (about 30% of the total wetland area), these fishponds producenearly 10,915metric tonnes of fish annually: this is 11.4% of the total annual supply offish for India, providing a livelihood for more than 50,000 people [9–11]. This wetlandproduces also nearly 150 tonnes of fresh vegetables daily and 16,000 tonnes of paddyannually [11,12]. All these bioyields are consumed regularly by the inhabitants of Calcuttametropolitan area and previous studies have shown that both fish muscles and vegetablesare within the regulatory limits for consumption [9–19]. To the best of our knowledge,there is no reported evidence of health-related hazards spread singly by consumption offish or vegetables produced at the ECW ecosystem using wastewater [11].

Wetlands are selected for listing in relation to the Ramsar Convention according to theirinternational significance and importance because of their ecology, botany, zoology, limnol-ogy or hydrology. Although rapid urbanization has reduced the area of this wetland from81 (in 1945) to 51 km2 today, the ECW ecosystem has been declared a Ramsar site (No.1208) from 19 August 2002 [20]. Unfortunately, because of urban encroachment this Ram-sar site is facing conversion and thus losing its international status [11]. According to themost recent studies using the post-classification change detection analysis approach, con-versions at the ECW ecosystem have increased significantly (built-up area has increased by166% and open space class has decreased by 45%). This needs serious attention [21]. TheECW ecosystem, known to support rich biodiversity (table 1), can suffer from this rapidconversion and alteration of natural habitats.

Although Santragachi Lake, an urban wetland 20 km away from ECW ecosystem har-bours thousands of migratory and residential waterbirds each year [22], the birds of the

Table 1. Biodiversity profile of ECW ecosystem.

Taxon Diversity Reference

Bacteria 12 phyla [70]Phytoplankton 30 species [71–72]

55, 57, 58 and 63 species [50]Aquatic macrophytes 43 species [71]

55 species [72]Bank flora 39 species [71]Macro flora 155 species [71]Vegetables and crops 24 species [71]Fruit plants 5 species [71]Ornamental plants 10 species [71]Zooplankton 22 species [73]

17 species [72]Molluscs 18 species [74]Aquatic insects 14 species [72]

26 species [74]Butterflies 74 species [75]Amphibians 4 species [72]

6 species [74]Reptiles 19 species [72]

15 species [74]Fishes 52 species [11]

37 species [72]40 species [74]

Avifauna 125 species [75]66 species [72]162 species [23]

Mammals 16 species [72]20 species [11]

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ECW ecosystem now number 162 species, not as previously recorded 271 species, with alocal extinction of 109 bird species over the last 30 years [23]. East Kolkata Wetland Man-agement Authority (EKWMA) is the statutory body for the conservation and managementof this wetland. EKWMA and local NGOs have taken a number of steps towards the con-servation and management of the ECW ecosystem. These have improved the natural vege-tation of this wetland by 24% [21].

During the early 1990s, it was reported by various regional and national organizationsthat most of the tannery agglomerates operating in the Tangra, Tapsia and Tiljala, neigh-bourhoods of Calcutta discharged serious levels of pollution [24]. Establishment of Efflu-ent Treatment Plants within each tannery was not feasible for lack of space. After muchdebate, in December 1996, the Supreme Court of India delivered a final and summaryjudgment in M.C. Mehta v The Union of India, W.P. (C) NO. 3727 of 1985; Judgment of19.12.1996 (reported in SCALE 1996 (9): 397–415) ordering over 500 tanneries to relo-cate or close by 30 September 1997 [24,25].

The Calcutta Leather Complex (CLC) was established accordingly at Bantala, a sitewithin the ECW ecosystem, 15 km away from Calcutta city. The CLC was supposed toreceive 550 tanneries and provide a Common Effluent Treatment Plant (CETP). During theconversion process, it became apparent that most of the tannery owners were reluctant tomove, particularly since they had to bear the cost of relocation. The

CLC started operations on 30 July 2005, but by July 2007, according to the Directorateof Industries, West Bengal, only 125 tanners had started operating in the new location,although 433 of 550 tanners had been allocated land at the leather complex. The WestBengal Pollution Control Board permitted the operation of tanneries only if they werelocated within the leather complex; but this study established that unauthorized and illegaloperations were taking place.

Wetlands perform multifarious functions as the ‘kidney of nature’, having an excellentability to remove pollutants. Studies from around the globe have documented this fact.Constructed wetlands [26–29], natural wetlands [30,31] and natural restored wetlands [32]have been found to be most efficient in removing most of the organic and inorganic pollu-tants, including heavy metals and pesticides [33–47]. The natural amelioration of pollutionloads in ECW ecosystems has been studied by various researchers [48–50]. In a study byour research team prior to relocation of tanneries within the ECW ecosystem [9], it wasfound that the concentration of trace metals (Pb, Zn and Fe) in wastewater reduced by 25–45%, while total Cr was reduced by 95%, from the source point to the discharge site onthe course of the 40 km long wastewater carrying canal via stabilization ponds in ECWecosystem.

This study reports our investigation of the consequences of shifting tannery agglomer-ates within the ECW ecosystem (which is 15 km downstream from the original locationand so much nearer to the discharge point) in terms of physicochemical characteristics ofthe wastewater from the wastewater carrying canals. We also monitored the ameliorationefficiency of the ECW ecosystem after the relocation of tanneries to check if there wereany significant changes before and after the relocation.

2. Materials and methods

This study was undertaken from January 2008 to December 2010. Monthly sampling ofwastewater from wastewater carrying canals was carried out to get the representative value

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for each month (N= 36, number of total samples). Present findings were compared withprevious observations made by our research group [9] to comment on probable changes inthe physicochemical properties of the wastewater from ECW ecosystem. Statistical testswere carried out to find whether there were any significant changes between the presentobservations and the previous findings. Harmony was maintained between this study andour previous studies in regard to the selection of study sites, sampling seasons, samplingmethods and analysis of samples for physicochemical parameters.

2.1. Study sites

The first sampling site (Site 1) was about 1 km from the source point on the canal carryingraw composite tannery effluent from Tangra tannery agglomerate (China town), Calcutta.As raw untreated tannery effluents entered the ECW ecosystem from this point onwards,this was the most important site to monitor both before and after tannery agglomerate relo-cation. The second site (Site 2) was located at Chowbaga, 8 km farther from the sourcepoint, where the composite tannery effluent was siphoned into the SWF canal after mixingwith municipal sewage through the Ballygunge Drainage Pumping System which carriedthe bulk effluent load from two other tannery agglomerates namely, Tapsia and Tiljala. Themixture of municipal sewage and industrial effluents (including tanneries) is bound to pro-duce the most complex of wastewater, and hence, this was chosen as the second study site.

The third sampling site (Site 3) was on SWF canal near the newly built CLC at Karaid-anga, around 15 km away from the source point. During the previous study [9], this sitewas chosen in anticipation of the relocation of tannery agglomerates. This site is importantbecause it is located near the mid-point of the wastewater carrying canal. The fourth site(Site 4) was also on the same canal near Kultigong lock gate, about 40 km away from the

Table 2. Physicochemical parameters for wastewater carrying canal in ECW ecosystem for the period 2008–2010 (values expressed as mean ± SD).

Parameters Site 1 Site 2 Site 3 Site 4

Air Temp. (°C) 32.5 ± 2.5 (0.84)↑ 32.6 ± 3.0 (0.34)↑ 32.5 ± 3.2 (0.74)↑ 32.5 ± 3.0 (0.90)↑Water Temp.

(°C)32.2 ± 3.5 (1.29)↑ 31.1 ± 3.5 (1.23)↑ 30.8 ± 2.9 (0.16)↑ 31.0 ± 3.3 (0.42)↑

pH 7.9 ± 0.3 (1.54)↑ 7.0 ± 0.1 (7.89)⁄↓ 7.2 ± 0.3 (2.05)↓ 7.4 ± 0.3 (0.67)↓DO (mgL�1) 0.03 ± 0.01 (200.00)⁄↑ 0.23 ± 0.19 (130.00)⁄↑ 0.33 ± 0.26 (25.00)↓ 3.97 ± 1.76 (6.37)↓TDS (mgL�1) 3730 ± 420 (33.60)⁄↓ 1620 ± 125 (32.18)⁄↓ 2050± 425 (113.98)⁄↑ 2670 ± 355 (15.84)↑Conductivity

(mS/cm)7.4 ± 0.9 (37.29)⁄↓ 2.2 ± 0.2 (53.04)⁄↓ 3.1 ± 0.7 (69.19)⁄↑ 4.4 ± 0.9 (8.94)↓

TSS (mgL�1) 1175 ± 455 (12.65)↓ 460 ± 45 (33.16)⁄↑ 1240 ± 415 (148.26)⁄↑ 100 ± 35 (6.34)↑Acidity-P

(mmol L�1)0.10 ± 0.06 (90.38)⁄↓ 0.27 ± 0.13 (65.91)⁄↓ 0.23 ± 0.21 (70.51)⁄↓ 0.20 ± 0.17 (78.28)⁄↓

Alkalinity-M(mmol L�1)

20.3 ± 3.5 (35.40)⁄↓ 6.4 ± 0.9 (89.94)⁄↓ 4.6 ± 1.34 (78.70)⁄↓ 4.7 ± 0.8 (77.02)⁄↓

CO3 Hardness(mgL�1 CaCO3)

1045 ± 300 (37.35)⁄↑ 270 ± 45 (49.22)⁄↓ 185 ± 60 (54.56)⁄↓ 175 ± 50 (59.23)⁄↓

Total Hardness(mgL�1 CaCO3)

1070 ± 235 (10)↑ 290 ± 35 (58)⁄↓ 240 ± 35 (63)⁄↓ 200 ± 60 (80)⁄↓

Cl� (mgL�1) 2070 ± 635 (45.03)⁄↓ 240 ± 65 (85.32)⁄↓ 1460 ± 800 (101.41)⁄↑ 830 ± 340 (49.06)⁄↓PO4

3� (mgL�1) 0.68 ± 0.3 (115)⁄↑ 6.47 ± 3.7 (251)⁄↑ 5.54 ± 1.9 (68)⁄↑ 2.69 ± 1.8 (13)↑NO3

� (mgL�1) 41.7 ± 14.4 (5.28)↑ 84.2 ± 43.8 (105.09)⁄↑ 53.3 ± 23.1 (54.22)⁄↑ 43.3 ± 10.4 (17.49)↑

Values in parentheses indicate % increase (↑) or % reduction (↓) in physicochemical parameters after relocation oftanneries. Significant changes (p< 0.05) have been designated by asterisks (⁄).

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source point and near the confluence of the canal with the River Kulti (figure 1). Thissampling site was chosen to monitor the pollution load from Kolkata metropolitan area,which is continuously discharged to Kulti River and through it, to the River Ganga. Thissite is important for scrutinizing the amelioration efficiencies of the ECW ecosystem.

2.2. Collection of water samples

Wastewater was collected from all four selected sites. In each site, two samples were col-lected and were mixed in equal proportions. The mixed water was divided into two partsfor the analysis of physicochemical parameters. In one part, concentrated HNO3 was added(converting the wastewater pH< 2.0) for preservation of metals. Then, 500mL of acidifiedwastewater was collected from each site, brought to the laboratory in plastic bottles andrefrigerated at 4 °C before analysis. The other part (1 L of wastewater) was collected with-out adding any preservatives and kept at 4 °C using ice bags before being taken to the lab-oratory for analysis of rest of the physicochemical parameters.

2.3. Physicochemical characterization of wastewater

A Mettler Checkmate 90 Toledo was used to analyse water samples potentiometrically forwater pH, conductivity and total dissolved solids (TDS) on each study site. Wastewatersfor physicochemical parameter analysis (500mL) were passed through Whatman No. 1 fil-

Table 3. Guidelines for drinking water quality in India (BIS = Bureau of Indian Standards; CPCB = CentralPollution Control Board; WHO = World Health Organization).

Parameters BIS CPCB WHO

Desirable Permissible Drinking watersource (withdisinfection)

Drinking water source (withconventional treatment anddisinfection)

pH 6.5 – 8.5 Norelaxation

6.5 – 8.5 6.0 – 9.0 6.5 – 8.5

DO (mg L�1) 6.0 – 6.0 4.0 –TDS (mg L�1) 500 2000 500 1500 1000Alkalinity-M

(mmol L�1)200 600 – – –

CO3 Hardness(mg L�1

CaCO3)

– – 200 – 500

Total Hardness(mg L�1

CaCO3)

300 600 200 – 500

Cl-(mg L�1) 250 1000 250 600 250NO3

- (mg L�1) 45 Norelaxation

20 50 10

Cr (mg L�1) 0.05 Norelaxation

0.05 0.05 0.05

Mn (mg L�1) 0.1 0.3 0.5 – 0.1Fe (mg L�1) 0.3 1.0 0.3 0.5 0.3Cu (mg L�1) 0.05 1.5 1.5 1.5 2.0Zn (mg L�1) 5.0 15 15 15 3.0Pb (mg L�1) 0.05 No

relaxation0.1 0.1 0.01

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ter paper in the laboratory. Filter papers thus trapping the suspended solids were subjectedto gravimetric analysis of total suspended solid (TSS) by using Mettler AE 240 monopanelectronic balance. Merck, Germany, field testing Aqua-Merck reagent kits were used onthe spot for titrimetric analysis of dissolved oxygen (DO), while NO3

�, PO43�, Cl�, total

hardness, carbonate hardness, acidity and alkalinity were analysed from the filtrate in thelaboratory.

2.4. Elemental analysis

Selection of elements (Cr, Mn, Fe, Cu, Zn and Pb) was made based on previous reports ofthe study area that pointed out the major elemental contaminants of composite wastewaterin ECW [9,51]. Briefly, about 20mL of refrigerated wastewater sample was taken into a100-mL beaker and to it 5mL of concentrated nitric acid was added. The sample wasdigested into a temperature-controlled hot plate in a fume chamber until the final volumeof the sample was reduced to about 5mL. The addition of nitric acid and subsequentdigestion was repeated until a clear solution was obtained. The sample was filtered withWhatman No. 40 filter paper and diluted to 50mL final volume with distilled water andwas kept at 4 °C before trace metal analysis in an atomic absorption spectrophotometer.Analysis of concentrations of Cr, Mn, Fe, Cu, Zn and Pb was carried out by atomicabsorption spectrophotometer (Perkin-Elmer Analyst-100 with interfacing AAwinlab Soft-ware), using element-specific hollow cathode lamps in the default conditions, in flameabsorption mode following modified standard protocols [52].

Figure 2. Concentration of phosphate (mgL�1) from all the study sites before PTR (Prior to TanneryRelocation) and after ATR (After Tannery Relocation).

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2.5. Reagents used

All gravimetric analysis, reagents and standard preparation were performed using a MettlerAE 240 monopan electronic balance and all the reagents used were of analytical grade andobtained from Merck, Germany.

2.6. Statistical analysis

Data obtained were analysed for paired Student’s t-tests for possible significant differencein wastewater physicochemical properties and trace metals among present observationswith that of the previous findings [9] (p< 0.05). Statistical analysis was established usingstatistical software Statistics for Windows, Version 5.1A, for studying correlation between

Figure 3. Concentration of nitrate (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates.

Table 4. Trace metal concentration for wastewater carrying canal in ECW ecosystem for the period 2008–2010(values expressed as mean ± SD).

Metals Site 1 Site 2 Site 3 Site 4

Cr (mgL�1) 0.23 ± 0.12⁄↓ 0.19 ± 0.11↓ 0.36 ± 0.23⁄↑ 0.15 ± 0.09⁄↑Mn (mgL�1) 1.29 ± 0.31↑ 1.16 ± 0.39↑ 0.98 ± 0.28⁄↓ 1.07 ± 0.22⁄↓Fe (mgL�1) 4.67 ± 0.56⁄↑ 4.23 ± 0.89⁄↑ 4.89 ± 1.23⁄↑ 4.36 ± 1.41⁄↑Cu (mgL�1) 0.25 ± 0.09⁄↓ 0.23 ± 0.03↑ 0.25 ± 0.16⁄↓ 0.29 ± 0.12⁄↓Zn (mgL�1) 0.17 ± 0.07⁄↓ 0.15 ± 0.05⁄↓ 0.16 ± 0.08↑ 0.12 ± 0.02⁄↓Pb (mgL�1) 0.62 ± 0.09↓ 0.42 ± 0.12↑ 0.77 ± 0.26⁄↑ 0.57 ± 0.21⁄↑

Significant changes increase (↑) or reduction (↓) (p< 0.05) have been designated by asterisks (⁄).

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physicochemical parameters and trace metals from all the study sites. Graphical plots weremade by using SciDAVis release 0.2.0; 2009.

3. Results and discussion

Table 2 shows the physicochemical conditions of wastewater from all four sites of thewastewater canal. Average air and water temperature were found to have increased in allfour sites over the last 10 years, but these changes were not significant at the 5% level.The pH of water is considered as a measure of environmental suitability and a range of7.0–8.5 is considered to support higher aquatic diversity [53]. During our study, mostlyalkaline ranges of pH were observed and except at Site 1 pH was found to have beendecreased in all the other three sites in comparison with our previous study. The decreaseat Site 2 was significant (7.89%). DO in water, one of the most important parameters inassessing water quality, varies widely with the physicochemical and biological activities inthe water body. Permissible limits of DO in potable water are > 5.00mg/L [54] (table 3).During our study, mean DO values recorded for all the sites were much lower than thepermissible limit. Thus, the water is not suitable for drinking and according to the guide-lines of India’s Central Pollution Control Board (CPCB) the water is not even suitable foroutdoor bathing or propagation of wildlife and fisheries [55,56].

Figure 4. Concentration of Cr (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates, with significant increase in Cr concentration from Site 3, due to excess Cr emission fromthe CLC.

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A significant increase in total DO was observed for Site 1 (0.03 ± 0.01mgL�1) and Site2 (0.23 ± 0.19mgL�1), but for Site 3 and Site 4 a net decrease was observed. Tanneryeffluents are noxious wastewaters loaded with organic and inorganic substances most ofwhich demand molecular oxygen for oxidation [57,58]. Consequently, reduction in tanneryeffluent load at Site 1 and Site 2 resulted in an increase in DO. The opposite was observedfor Site 3 and Site 4. TDS in water constitutes a large number of inorganic salts and asmall amount of organic matter. Less than 500mg/L TDS is considered to be acceptablefor drinking water supply in India [55,56]. Our findings indicate much higher TDS concen-trations from all the sites. According to CPCB guidelines, this water could be used onlyfor irrigation, industrial cooling water and controlled waste disposal. It was interesting tonote that TDS for Site 1 (3730 ± 420mgL�1) and Site 2 (1620 ± 125mgL�1) reduced sig-nificantly, but for Site 3 (2050 ± 425mgL�1) and Site 4 (2670 ± 355mgL�1) TDSincreased. The increase at Site 3 was significant. The trend for TDS concentration for allthe sites was closely followed by water conductivity and a significant positive correlation(r = 0.87, p< 0.05) was observed between them.

TSS in our study showed an increased trend for all the sites except for Site 1. Again theincrease in TSS levels at Site 2 and Site 3 was found to be significant. It was interestingto note that acidity and alkalinity for all four sites reduced significantly over the last10 years. Total hardness and carbonate hardness also were found to be significantlyreduced for all the sites except Site 1 where a net increase was observed. Increase in

Figure 5. Concentration of Mn (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates.

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organic pollutant loads in wastewaters often results in an overall decrease in water pH.Again, pH, alkalinity and hardness are closely related and oscillate simultaneously in aqua-tic conditions under the direct influence of carbonate and bicarbonate ions [59]. Duringour study, significant positive correlations were observed between pH and alkalinity(r= 0.89, p< 0.05), pH and total hardness (r= 0.90, p< 0.05) and alkalinity and total hard-ness (r= 0.99, p < 0.05). Consequently, for Site 2, Site 3 and Site 4, the trend for fluctua-tion of pH, alkalinity and hardness was all synchronized. Site 1 was an exception in thisregard; here, pH and total hardness values were found to have increased over the last10 years but alkalinity values decreased. Site 1 was mostly devoid of DO before the tan-neries were relocated, but a 200% increase in DO has been recorded during our study.

This slow shift from anaerobic to aerobic aquatic conditions ought to encourage oxida-tion of most of the organic and inorganic pollutants. Most of these oxidation processesconsume alkalinity, lowering the overall value. For example, oxidation of 1mg of ammoni-acal nitrogen requires the consumption of 8.64mg of HCO3

� [60]. During our study, a sig-nificant decrease in chloride concentration was found in Site 1, Site 2 and Site 4, but therewas a significant increase in Site 3. Over the last 10 years, both phosphate and nitrate con-centrations were found to have increased for all the study sites. Increase in phosphate con-centration was significant for Site 1, Site 2 and Site 3. Increase in nitrate concentrationwas significant in Sites 2 and 3 (figures 2 and 3).

From these findings, it can be inferred that the physicochemical characteristics of waste-water carrying canals of ECW ecosystem have changed markedly over the last 10 years [9].

Figure 6. Concentration of Fe (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates.

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The main reasons for this are the reduction in the wetland areas and the increase in humanpopulation of the Kolkata metropolitan area, the third most populated city/urban agglomera-tion in India (after Mumbai and Delhi). The population of Kolkata has increased from13.22million in 2001 to 14.11million in 2011 [61]. The relocation and illegal operation oftannery agglomerates have worsened the situation. The closing of some of the tanneries atSite 1 had a positive effect. Increased pH and DO were observed along with reduced TDS,conductivity, salinity, alkalinity and acidity. These changes indicate attenuation of pollutionloads. Similar findings were also made for Site 2 except for phosphate and nitrate. Thismay be explained by the fact that municipal waste merged with the canal at this site.

The increased phosphate and nitrate load was found to be reduced in the downstreamsection of the canal, mostly because of wastewater-fed aquaculture; but the final dischargeconcentrations were higher. The impact of tannery relocation was most apparent from thefindings made from Site 3, this is, the newly constructed CLC. This site showed significantincrease in TDS, conductivity, TSS, salinity, phosphate and nitrate along with reduced pHand DO. This enhanced pollution load from Site 3 directly influenced the final dischargearea, Site 4, with comparable physicochemical parameter concentrations.

Consequences of relocation of tannery agglomerates within the ECW ecosystem weremore apparent from the study of trace metal concentration (table 4). Figures 4–9 show thetrend of trace metal concentrations that varied widely during our study. Chromium, a tracemetal from the tanneries, was found to vary significantly with the relocation of tanneries.

Figure 7. Concentration of Cu (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates.

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Site 1, the original site for tannery wastewater disposal from Tangra tannery agglomerates,showed a significant decrease in total Cr concentration. This trend was also found in Site2, carrying the tannery effluents from Tapsia and Tiljala tannery agglomerates. But mostsurprisingly a significant increase in Cr concentration was observed in Site 3 (CLC) andSite 4 (final disposal site). Undoubtedly, the sole source of this increased Cr was tanneryeffluents released from the newly constructed CLC at Site 3.

The situation is more alarming since all the values recorded for Cr were much higherthan the permissible limit for potable water (table 3). As for the amelioration efficiency ofthe ECW ecosystem, 35% decrease in Cr concentration was noted in our study, in compari-son with the previously reported 95% reduction [9]. Concentration of Mn was comparablefor Site 1 and Site 2 over the last 10 years, but it reduced significantly for Site 3 and Site4, leading to the overall reduction by 17% from Site 1 to Site 4. Concentration of Feincreased significantly for all the sites and only a 7% overall reduction was noted fromSite 1 to Site 4 during our study. Concentrations of Fe from all the sites were much higherthan the permissible limits (table 3).

The main source of Cu and Zn in and around Kolkata is electroplating units and batteryindustries. There was a significant reduction in Cu and Zn concentration for Site 1, Site 3and Site 4, but for Site 2 it was mostly unchanged. The reduction in Zn concentrationfrom Site 1 to Site 4 was almost 30%. Concentration of Pb, an output of battery and pig-ment manufacturing units, was notable. It was found to be reduced at Site 1, unchanged atSite 2 and significantly increased in Site 3 and Site 4 as compared to previous studies.

Figure 8. Concentration of Zn (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates.

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This finding indicates that there are sources of Pb contamination around Site 3, possiblyfrom the colorants used in preparing leather at the CLC. The overall reduction in Pb fromSite 1 to Site 4 was only 8%. Hierarchical cluster analysis of all the sites based on totaltrace metal concentration revealed that Site 2 and Site 4 were closely located with similarmetal loads (figure 10). Site 1 was nearer to this cluster in terms of metal concentrationsand Site 3 was most distantly located. This shows that Site 3 has altogether different com-positions for metal concentrations, which can be attributed to the relocation of tanneries.

These findings from Site 3 call into question the efficiency of treatment of tannery efflu-ent within the CLC. This was supposed to include a CETP Network, with construction of

Figure 9. Concentration of Pb (mgL�1) from all the study sites before (PTR) and after (ATR) relocation oftannery agglomerates.

Figure 10. Hierarchical cluster analysis of all the sites under present investigation based on overall trace metalconcentrations.

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CETP Modules 1–6, Effluent Transportation System, Common Chrome Recovery System(CCRS), Solid Waste Management System and Treated Effluent Sump and Pumping Sta-tion (TESPS). According to a report by CPCB [62] on their visit to the CLC during Octo-ber 2007 (just before this study began), the CETP had 4 modules of 5Million Litres perDay (MLD) with only a total capacity of 20MLD instead of 30MLD as directed by theSupreme Court of India. After primary treatment, effluent from individual tanning unitswas sent to CETP for secondary treatment, but only 7.5MLD treated effluent passedthrough the CETP, as this was the maximum discharged capacity of the outlet.

The rest of the treated effluents were being by-passed through a small canal (nullah) tomeet the wastewater carrying canal, near Site 3. The CPCB report [62] also revealed thatthere were no automatic monitoring devices provided to the CETP except DO meters. Atindividual level, 154 tanning units were provided with chrome recovery plants. Another25 units were found to use a common mobile chrome recovery plant and the remainingnine units were found to share chrome recovery plants. No data were available from thetannery association on the reuse of the recovered Cr. We found also that apart from Cr,tanning units at CLC did not recover other by-products like salt and other chemicals fromthe wastes. Scientific measures for disposing of hazardous waste were unavailable at CLC;consequently, wastes were stored at the operation site and later sent to distant locations fordisposal. According to the CPCB report [62], the CETP sludge showed a high concentra-tion of total Cr (32,764mg/kg).

Over the last century, the ECW ecosystem has played the role of ‘ecological subsidizer’for Calcutta that treats its wastewater in the most cost-effective manner by alternative tradi-tional method without applying any conventional sewage/effluent treatment plants [63].For tannery effluent treatment, the ECW ecosystem was found to be more effective thanEffluent Treatment plants from Bihar, India [64]. Relocation of tannery agglomerateswithin the ECW ecosystem has undoubtedly affected its amelioration efficiency, becausehigher pollution loads were observed at the final disposal point Kultigong (Site 4), whichis near to the Ganga (Ganges) estuary. Moreover, recent studies have demonstrated thatonly 30% of the wastewater flowing through canals of the ECW ecosystem is actually usedfor irrigation and aquaculture. The other 70% of the wastewater flows directly from theGanga estuary into the Bay of Bengal [65].

Silt formation is a major problem for wastewater carrying canals in the ECW ecosystemand affects adversely both pisciculture and agriculture along with the decrease in meandepth of the ECW ecosystem [66]. Significant increase in TDS and TSS at Site 3 will makematters worse by producing more silt, a potential threat to the livelihoods to the economi-cally under-privileged population of 109 villages located within the boundary of the ECWecosystem. According to the most recent information on the CLC from the Government ofWest Bengal [67], 100% CCRS already exists, but so far only 5.89% physical progress onCETP modules 5 and 6 has been accomplished. A TESPS is nearly constructed. An envi-ronmental impact assessment has been made for a Solid Waste Management System, whichis now being constructed. It is to be hoped that these steps along with the shutting down ofillegal tannery operations and protection of the remnant of the ECW ecosystem will meetthe objectives for which the CLC was established. Legal protection for the ECW ecosystemincludes the East Kolkata Wetlands (Conservation and Management) Act, 2006 [68]. Thestatute provides that anyone convicted for having altered the nature of the ECW ecosystemwill be punished with a penalty of Indian Rupees 100,000 (£1200) and 3 years’ imprison-ment. The law needs to be upheld if the wetland is to be conserved.

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4. Conclusion

The tanning industry is very profitable. Because materials are easily obtained and labourcosts are low, more than half of the tanning operations of the world are carried out in low-and middle-income countries [69]. This is the case in Calcutta and the relocation of tan-nery agglomerates was inevitable in view of increasing pollution hazards. But the selectionof the site for CLC has been controversial, especially because the boundary area of theCLC lies within the ECW ecosystem. The study’s findings indicate that the CETP of theCLC was inadequate. Recent steps to improve the CETP at the CLC and to shut downillegal tannery operations are welcome. The relevant laws must be enforced. The sustain-able development of the economically weak population depending on the wetland will inturn benefit the health and natural functioning of the ECW ecosystem.

Acknowledgments

The authors are thankful for the infrastructural support provided by the Director of PublicInstruction and the Director of Technical Education, Government of West Bengal, India.The authors also express their kindest thanks to CSIR for providing necessary funds. Theauthors would also like to thank the learned anonymous reviewers for their painstakingevaluation of the manuscript, comments and suggestions and the Editor Dr Michael Brett-Crowther for his sustained goodwill and patience.

References

[1] Roy, U.S., Chattopadhyay, B., Datta, S. and Mukhopadhyay, S.K., 2011, Metallothionein as a biomarker toassess the effects of pollution on Indian major carp species from wastewater–fed fishponds of East CalcuttaWetlands (a Ramsar site). Environmental Research Engineering and Management, 4(58), 10–17.

[2] Ghosh, S.K., 2004, Traditional and commercial practices in sustainable development and conservation ofman and wetlands, knowledge marketplace reports. The 3rd IUCN World Conservation Congress, Bangkok,Thailand, 1–6.

[3] Olah, J., Sharangi, N. and Datta, N.C., 1986, City sewage fish ponds in Hungary and India. Aquaculture, 54,129–134.

[4] Ghosh, D. and Sen, S., 1987, Ecological history of Calcutta’s wetland conversion. Environmental Conserva-tion, 14, 219–226.

[5] Ghosh, D., 1990, Wastewater-fed aquaculture in the wetlands of Calcutta – an overview. In: Proceeding ofan International Seminar on Wastewater Reclamation and Reuse for Aquaculture, Calcutta, India, December1988. Environmental Sanitation Centre, Asian Institute of Technology, Bangkok, Thailand, 49–56.

[6] Ghosh, D., 1991, Ecosystems approach to low-cost sanitation in India: where the people know better. In: C.Etnier and B. Guterstam (Eds.) Ecological Engineering for Wastewater Treatment 2nd edn (London: Lewis),pp. 51–65.

[7] Kundu, N., 1994, Planning the Metropolis, a Public Policy Perspective (Calcutta: Minerva Associates).[8] Jana, B.B., 1998, Sewage-fed aquaculture: the Calcutta model. Ecological Engineering, 11(1–4), 73–85.[9] Chattopadhyay, B., Chatterjee, A. and Mukhopadhyay, S.K., 2002, Bioaccumulation of metals in the East

Calcutta Wetland ecosystem. Aquatic Ecosystem Health & Management, 5, 191–203.[10] Aich, A., Chakraborty, A., Sudarshan, M., Chattopadhyay, B. and Mukhopadhyay, S.K., 2011, Study of trace

metals in Indian major carp species from wastewater-fed fishponds of East Calcutta Wetlands. AquacultureResearch, 1–13. doi: 10.1111/j.1365-2109.2011.02800.x.

[11] Chaudhuri, S.R., Mukherjee, I., Ghosh, D. and Thakur, A.R., 2012, East Kolkata Wetland: a multifunctionalniche of international importance. OnLine Journal of Biological Sciences, 12(2), 80–88.

[12] Ghosh, D., 2005, Ecology and traditional wetland practice: lessons from wastewater utilisation in the EastCalcutta Wetlands, 1st ed. (Kolkata: Worldview), 120.

[13] Chatterjee, S., Chattopadhyay, B. and Mukhopadhyay, S.K., 2006, Trace metal distribution in tissues of cich-lids (Oreochromis niloticus and O. mossambicus) collected from wastewater-fed fishponds in East CalcuttaWetlands. A Ramsar site. Acta Ichthyologica Piscatoria, 36, 119–125.

218 U.S. Roy et al.

Dow

nloa

ded

by [

Ein

dhov

en T

echn

ical

Uni

vers

ity]

at 2

3:52

21

Nov

embe

r 20

14

[14] Chaudhuri, S.R., Mishra, M., Salodkar, S., Sudarshan, M. and Thakur, A.R., 2008, Traditional aquaculturepractice at East Calcutta Wetland: the safety assessment. American Journal of Environmental Science, 4(2),173–177.

[15] Bhattacharyya, S. and Santra, S.C., 2003, R. Khasnabis (Ed.) Ecology, economy and society: environmentalstatus of East Calcutta Wetlands and strategies for sustainable management (Kolkata: University of Cal-cutta), pp. 65–94.

[16] Chakraborty, D., Ghosh, D. and Niyogi, S., 1987, Calcutta pollutants: part 1: appraisal of some heavy metalsin Calcutta city sewage and sludge in use for fisheries and agriculture. International Journal of Environmen-tal Analytical Chemistry, 30, 243–253.

[17] Ghosh, D., 1999, Participatory Management in Wastewater Treatment and Reuse in West Bengal. UWEPOccasional, (Nieuwehaven: WASTE).

[18] Gupta, S.K., Mitra, A. and Adhikari, S., 1990, Post irrigation effect of Calcutta sewage effluents on soil andvegetations. Proceedings of National Symposium on Protection of Environment of City Water Fronts, (PEC-WF’ 90), Central Water Commission, New Delhi, 7–13.

[19] Chaudhuri, S.R., Salodkar, S., Sudarshan, M. and Thakur, A.R., 2007, Integrated resource recovery at eastCalcutta wetland – how safe is these? American Journal of Agricultural and Biological Sciences, 2, 75–80.

[20] Aich, A. and Kundu, M., 2010, East Calcutta wetland ecosystem – nature’s own low-cost effluent treatmentplant. Journal of Indian Leather Technologists’ Association, LX(7), 539–546.

[21] Parihar, S.M., Sarkar, S., Dutta, D., Sharma, S. and Dutta, T., 2012, Characterizing wetland dynamics: apost-classification change detection analysis of the East Kolkata Wetlands using open source satellite data.Geocarto International, 1–15, http://dx.doi.org/10.1080/10106049.2012.705337.

[22] Roy, U.S., Goswami, A.R., Aich, A. and Mukhopadhyay, S.K., 2011, Changes in densities of waterbird spe-cies in Santragachi Lake, India: potential effects on limnochemical variables. Zoological Studies, 50(1), 76–84.

[23] Ghosh, A.K., 2004, Avian diversity in east Calcutta wetlands. Environ, 9(1), 8–13.[24] Dembowski, H., 2001, Taking the State to Court: Public Interest Litigation and the Public Sphere in Metro-

politan India, Asia House’s online version. Available online at: http://www.asienhaus.de/public/archiv/tak-ing_the_state_to_court.pdf.

[25] M.C. Mehta v The Union of India, W.P. (C) NO. 3727 of 1985; Judgment of 19.12.1996 (reported inSCALE 1996 (9): 397 – 415). Available online at: http://www.supremecourtcases.com/index2.php?option=com_content & itemid=5 & do_pdf=1 & id=565.

[26] Maine, M.A., Sune, N., Hadad, H., Sanchez, G. and Bonetto, C., 2006, Nutrient and metal removal in a con-structed wetland for wastewater treatment from a metallurgic industry. Ecological Engineering, 26, 341–347.

[27] Puigagut, J., Vilaseňor, J., Salas, J.J., Béceras, E. and García, J., 2007, Subsurface-flow constructed wetlandsin Spain for the sanitation of small communities: a comparative study. Ecological Engineering, 30, 312–319.

[28] Mburu, N., Thumbi, G.M. and Mayabi, A.O., 2008, Removal of bacterial pathogens from domestic wastewa-ter in a tropical subsurface horizontal flow constructed wetland. Proceedings of Taal, The 12th World LakeConference, Jaipur, 1010–1015.

[29] Vymazal, J. and Kröpfelová, L., 2008, Removal of organics in constructed wetlands with horizontal sub-sur-face flow: a review of the field experience. Science of the Total Environment, 407(13), 3911–3922.

[30] Kadlec, R.H. and Knight, R.L., 1996, Treatment Wetlands (New York: Lewis).[31] Lei, Z., Ai, Z.D., Jin, S.W., Yan, G.T. and Fang, H.H., 2008, Natural wetlands utilization for un-collected

village sewage treatment. 2nd International Conference on Bioinformatics and Biomedical Engineering,Sanghai, 382–386.

[32] Jordan, T.E., Whigham, D.F., Hofmockel, K.H. and Pittek, M.A., 2003, Nutrient and sediment removal by arestored wetland receiving agricultural runoff. Journal of Environmental Quality, 32, 1534–1547.

[33] Ammon, D.C., Huber, W.C. and Heaney, J.P., 1981, Wetland’s use for water management in Florida. Journalof the Water Resources Planning and Management Division, 107, 315–327.

[34] Bavor, H.J., Roser, D.J., Fisher, P.J. and Smalls, I.C., 1989, D.A. Hammer (Ed.) Performance of Solid-matrixWetland Systems viewed as Fixed-Film Bioreactors: Constructed Wetlands for Wastewater Treatment, Muni-cipal, Industrial, and Agricultural (Chelsea: Lewis), pp. 646–656.

[35] Gale, P.M., Reddy, K.R. and Graetz, D.A., 1993, Nitrogen removal from reclaimed water applied to con-structed and natural wetland microcosms. Water Environmental Research, 65(2), 162–168.

[36] Gosselink, J.G. and Gosselink, L., 1985, The Mississippi river delta: A natural wastewater treatment system.In: P.J. Godfrey et al. (Eds.) Ecological considerations in wetland treatment of municipal wastewaters (NewYork: Van Nostrand Reinhold), pp. 327–337.

[37] Howard, W.C., 1985, Cycling and retention of nitrogen and phosphorus in wetlands: a theoretical andapplied perspective. Freshwater Biology, 15(4), 391–421.

[38] Pardue, J.H., Masscheleyn, P.H., DeLaune, R.D. and Patrick, W.H.Jr., 1993, Assimilation of hydrophobicchlorinated organics in freshwater wetlands: sorption and sediment-water exchange. Journal of Environmen-tal Science and Technology, 27, 875–882.

[39] Reed, S.C., Middlebrooks, E.J. and Crites, R.W., 1988, Natural Systems for Waste Management and Treat-ment, (New York: McGraw-Hill).

Changes in physicochemical characteristics of wastewater 219

Dow

nloa

ded

by [

Ein

dhov

en T

echn

ical

Uni

vers

ity]

at 2

3:52

21

Nov

embe

r 20

14

[40] Kaseva, M.E., 2004, Performance of a subsurface flow constructed wetland in polishing pre-treated wastewa-ter, a tropical case study. Water Research, 38, 681–687.

[41] Konnerup, D.K. and Brix, H., 2009, Treatment of domestic water in tropical, sub-surface flow constructedwetlands planted with Canna & Heliconia. Ecological Engineering, 35(2), 248–257.

[42] Vymazal, J., 2005, Horizontal subsurface flow and hybrid constructed wetlands systems for wastewater treat-ment. Ecological Engineering, 25, 478–490.

[43] Coveney, M.F., Stites, D.L., Lowe, E.F., Battoe, L.E. and Conrow, R., 2002, Nutrient removal from eutro-phic lake water by wetland filtration. Ecological Engineering, 19(2), 141–159.

[44] Jing, S.R., Lin, Y.F., Lee, D.Y. and Wang, T.W., 2001, Nutrient removal from polluted river water by usingconstructed wetlands. Bioresource Technology, 76(2), 131–135.

[45] Jing, S.R., Lin, Y.F., Lee, D.Y. and Wang, T.W., 2002, Performance of constructed wetlands planted withvarious macrophytes and using high hydraulic loading. Journal of Environmental Quality, 31(2), 690–696.

[46] Kovacic, D.A., Twait, R.M., Wallace, M.P. and Bowling, J.M., 2006, Use of created wetlands to improvewater quality in the Midwest – Lake Bloomington case study. Ecological Engineering, 28(3), 258–270.

[47] Wiessner, A., Kappelmeyer, U., Kuschk, P. and Kästner, M., 2005, Sulphate reduction and the removal ofcarbon and ammonia in a laboratory-scale constructed wetland. Water Research, 39, 4643–4650.

[48] Jana, B.B., 1998, Sewage-fed aquaculture: the Calcutta model. Ecological Engineering, 11, 73–85.[49] Chattopadhyay, B., Chatterjee, S. and Mukhopadhyay, S.K., 2004, Seasonality of physicochemical parame-

ters of tannery wastewater passing through the East Calcutta Wetland ecosystem. Journal of the Society ofLeather Technologists and Chemists, 88, 27–36.

[50] Pradhan, A., Bhaumik, P., Das, S., Mishra, M., Khanam, S., Hoque, B.A., Mukherjee, I., Thakur, A.R. andChaudhuri, S.R., 2008, Phytoplankton diversity as indicator of water quality for fish cultivation. AmericanJournal of Environmental Sciences, 4(4), 406–411.

[51] Chatterjee, S., Chattopadhyay, B., Dutta, S. and Mukhopadhyay, S.K., 2006, Heavy metal phytoremediationat contaminated east Calcutta wetlands. Journal of Natural History, 2(1), 17–28.

[52] Welz, B. and Sperling, M., 1999, Atomic Absorption Spectrometry, (Weinheim: Wiley-VCH).[53] Bell, H.L., 1971, Effect of low pH on survival and emergence of aquatic insects. Water Resource, 5, 313.[54] WHO, 2011, Guidelines for drinking-water quality. – 4th edn. – WHO Press, World Health Organization,

Geneva 27, Switzerland.[55] Bureau of Indian Standards, 1991, Specification for Drinking Water. – 18:10500. – New Delhi.[56] Guidelines for Water Quality Monitoring, 2007, Central Pollution Control Board. Parivesh Bhawan, East

Arjun Nagar, Delhi–32.[57] Cooman, K., Gajardo, M. and Nieto, J., 2003, Tannery wastewater characterization and toxicity effect on

Daphnia spp. Environmental Toxicology, 18, 45–51.[58] Ates, E., Orhon, D. and Tunay, O., 1997, Characterization of tannery wastewater for pretreatment – selected

case studies. Water Science and Technology, 36, 217–223.[59] Southern Regional Aquaculture Center, 1992, Interactions of pH, carbon dioxide, alkalinity and hardness in

fish ponds. SRAC Publication, 464, 1–4.[60] Cooper, P.F., Job, G.D., Green, M.B. and Shutes, R.B.E., 1996, Reed beds and constructed wetlands for

wastewater treatment (Marlow: WRC).[61] Sudhira, H.S. and Gururaja, K.V., 2012, Population crunch in India: is it urban or still rural? Current Sci-

ence, 103(1), 37–40.[62] Parivesh, 2007, Central Pollution Control Board, Industrial Pollution Control: Performance Status of CETP

at Calcutta Leather Complex, Bantala, West Bengal 112–113. Available online at: http://www.cpcb.nic.in/Highlights/2007/105–122.pdf.

[63] Ghosh, D., 1997, Environmental Agenda for Calcutta: Conserving the Water Regime for an EcologicallySubsidized City (Banabithi: Environment Special Issue, Department of Environment and Forests, Governmentof West Bengal).

[64] Chattopadhyay, B., 2002, Physico-chemical and biological characterization of tannery effluents envisagingenvironmental impact assessment from ecotoxicological standpoint. PhD thesis, Jadavpur University, India.

[65] Dey, D., 2009, J. Feyen, K. Shannon and M. Neville (Eds.) Water and urban development paradigms:towards an integration of engineering, design and management approaches, sustainable development andwastewater in peri–urban wetlands: a case study on East Kolkata Wetland (London: CRC Press).

[66] Mukherjee, D.P., 2011, Stress of urban pollution on largest natural wetland ecosystem in East Kolkata –causes, consequences and improvement. Archives of Applied Science Research, 3(6), 443–461.

[67] Banglar Mukh, 2012, Status report on Calcutta leather complex for incorporation in the portal ‘BanglarMukh’. Available online at: http://www.google.co.in/url?sa=t&rct=j&q=banglar%20mukh%2C%202012%2C%20status%20report%20on%20calcutta%20leather%20complex%20for%20incorporation%20in%20the%20portal%20%E2%80%98banglar%20mukh&source=web&cd=1&cad=rja&ved=0CDIQFjAA&url=http%3A%2F%2Fwww.banglarmukh.com%2FBanglarMukh%2FDownload%3FAlfrescoPath%3DDocuments%2FWh-atsNew%26FileName%3DStatus_CLC.pdf&ei=9S4CUcjXEcXmrAfIh4HgBQ&usg=AFQjCNFtd5ccNOhAll-KEpp0MCljGVmqdqg&bvm=bv.41524429,d.bmk.

[68] East Kolkata Wetlands (Conservation and Management) Act, 2006.

220 U.S. Roy et al.

Dow

nloa

ded

by [

Ein

dhov

en T

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ical

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ity]

at 2

3:52

21

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14

[69] Azom, M.R., Mahmud, K., Yahya, S.M., Sontu, A. and Himon, S.B., 2012, Environmental impact assess-ment of tanneries: a case study of Hazaribag in Bangladesh. International Journal of Environmental Scienceand Development, 3(2), 152–156.

[70] Chaudhuri, S.R. and Thakur, A.R., 2006, Microbial genetic resource mapping of East Calcutta wetlands.Current Science, 91(2), 212–217.

[71] Institute of Wetland Management and Ecological Design (IWMED), 2004, Preliminary study on biodiversityof sewage fed fisheries of East Kolkata Wetland ecosystem. Kolkata, pp. 40.

[72] Kundu, N., Pal, M. and Saha, S., 2008, East Kolkata Wetlands: a resource recovery system through produc-tive activities. In the Proceedings of Taal 2007, The 12th world Lake Conference, Jaipur, India, 868–881.

[73] Mukhopadhyay, S.K., Chattopadhyay, B., Goswami, A.R. and Chatterjee, A., 2007, Spatial variations in zoo-plankton diversity in waters contaminated with composite effluents. Journal of Limnology, 66(2), 97–106.

[74] De, M., Bhunia, S. and Sengupta, T., 1989, A Preliminary account on major wetland fauna of Calcutta andsurroundings. Ecology, 3(9), 5–11.

[75] Chowdhury, S. and Soren, R., 2011, Butterfly (Lepidoptera: Rhopalocera) fauna of East Calcutta Wetlands,West Bengal, India. Check List, 7(6), 700–703.

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3:52

21

Nov

embe

r 20

14