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SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
Revisiting East Kolkata Wetlands – Management Options
with Holistic Approach
SOMENATH BHATTACHARYYA
Society of Integrated Coastal Management (SICOM),
Ministry of Environment, Forest & Climate Change, Government of India, New Delhi
E-mail: some.wetland@gmail.com
Abstract: East Kolkata Wetlands (EKW) are series of shallow depth sewage-fed fisheries thriving in eastern part of Kolkata
City. These water bodies, erstwhile part of Sundarbans, represent the spill basin of once mighty river “Bidyadhari”. These were
originally saline in nature, which gave rise to its name as “Salt Lake”. Traditionally “Capture Fishing” was practiced here.
Sudden changes in course of the Ganges towards east due to neo-tectonic movement transformed the spill basin into stagnant
water bodies. Some portion of this area was leased out in 1868 for solid waste dumping, renamed as “Dhapa”. Subsequently,
local fishermen tried to utilise city sewage flowing towards eastern side through canals as source of water and nutrient which
became successful in 1929-30. Altogether 7300 hectares of sewage-fed fisheries existed here in 1945. Due to population explosion
and urbanisation, indiscriminate reclamation of these wetlands was going on without considering the considerable ecosystem
services being provided by them. Subsequently, Calcutta High Court imposed injunction on further reclamation of these wetlands
in 1992, which by that time became famous as EKW, even though these wetlands are still under threat. An objective interdisciplinary
assessment of various issues of concerns in EKW and suggesting available management option towards its sustainability has
been attempted here.
Keywords: Aquaculture, Bheris, Recycling, Spill basins, Wetlands.
INTRODUCTION
East Kolkata Wetlands (EKW) are a series of shallow water
sewage-fed fisheries thriving in the eastern part of Kolkata City
and bordering Salt Lake and Rajarhat, extending over districts
of North 24-Parganas and South-24 Parganas in the State of
West Bengal, India. It is a vast wetland area beyond the eastern
edge of the city that has been transformed to use city wastewater
in fisheries, vegetable gardens and paddy fields in successive
tracts of land (Ghosh, 1999). It is located in between 20°25' N
– 20°35' N Latitudes and 88°20'E – 88°35' E Longitudes. EKW
spreads over an area of 12,500 hectares and comprises of 254
sewage fed fisheries (Kundu et al., 2008). It is a classic example
of waste recovery for the last 100 years or so through a
mechanism traditionally developed by the local people and
fishermen. This resource recovery system is the largest of its
kind in the world (Ghosh, 1999). The resource recovery system
from the waste, both city sewage and garbage is so robust that
sometimes EKW has been referred as WAR (Waste as
Resource) Field (Ghosh, 1985a) or WRR (Waste Recycling
Region) (Ghosh, 1985b). Subsequently, Calcutta High Court
also designated this area as Waste Recycling Region. Three
major economic activities are going on in EKW – Fisheries in
sewage fed ponds (locally known as bheries), Garbage farms
and paddy cultivation outside the core area.
Figure 1 describes the EKW area and its closeness to
Kolkata City. Although there are two parallel canals, namely
Dry Weather Flow (DWF) canal, which is brick lined and Storm
Weather Flow (SWF) canal which flow parallel to each other,
but only SWF has been shown in the map due to scale factor.
Raw sewage from Kolkata City directly flows into these fish
ponds and the ponds accomplishes a wide range of physical,
chemical and biological processes to grow fishes using the raw
sewage as nutrient and ultimately improving the quality of the
effluents from these fisheries which is disposed into Bidyadhari
River at a point known as Kulti Ganj, about 33 kilometres away
from Kolkata City. This wetland system is popularly referred
to in various media as the kidney of Kolkata City, since the
city has practically no Sewage Treatment Plant. It has been
declared as a ‘Wetland of International Importance’ by Ramsar
Convention in the year 2002 since EKW is ‘one of the rare
examples of environmental protection and development
management where a complex ecological process has been
SPECIAL PUBLICATION OF THE GEOLOGICAL SOCIETY OF INDIA
No.9, 2021, pp.129-138
| DOI: 10.17491/CGSI/2020/165852
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
130 SOMENATH BHATTACHARYYA
adopted by the local farmers for mastering the resource
recovery activities.’
Evolution of EKW
Evolution of EKW is organically linked to the evolution of
the coastal part of the Ganga Brahmaputra Delta (GBD) during
late Holocene period as a result of Delta Progradation. A
number of paludal basins and mangrove coastal plain were
created around 5 ka BP in the Rajmahal Garo Gap during the
formation of the Ganga Brahmaputra Delta Formation when
rate of Sea Level Rise slowed down and abandonment and
eastward migration of the active Ganga distributaries took place
leading to the formation of the Sundarbans area, of which
EKW was a part.
ECOLOGICAL HISTORY OF EKW
Ecological history of EKW is well documented (Furedy &
Ghosh, 1984; Gosh & Sen, 1987, Ghosh, 1999). The present
day EKW actually represent the spill basin of once mighty river
“Bidyadhari” and was part of Sundarbans. The tidal channels
of this region joined further down with a deltaic channel of the
Sundarbans, through which salt water flowed into the water
bodies here (Stewart, 1836). Due to tidal interplay, these water
bodies were saline in nature, which gave rise to its name as
“Salt Lake” and where traditionally “Capture Fishing” was
practiced by the local people. There were remarkable changes
in the courses of the Ganges and Brahmaputra Rivers during
the last few hundred years due to neo-tectonic movements as a
consequence of faulting and resultant tilting of blocks (Morgan
& McIntire, 1959). As a result, the River Ganges abandoned
numerous western distributaries for joining the Brahmaputra –
Meghna system to the southeast and ‘about 12,000 square miles
of former Gangetic deltaic plain in southwest Bengal (Sic) has
been abandoned’ (Morgan & McIntire, 1959). This had caused
consequent changes in the hydrological regime of this area,
especially the reduction in headwater discharge along the rivers
and tributaries. Rapid siltation along the rivers occurred starting
from the end of the 14th century and finally the River Bidyadhari
became completely defunct by the end of 19th century. With
the death of Bidyadhari River, the tidal channel that used to
deposit silt in this area became almost defunct and the process
of natural silt deposition and raising of level of the spill area
was completely stopped (Ghosh, 1999). As a result, the entire
spill basin lost the tidal subsidy leading to formation of stagnant
water bodies and major breeding areas for vector borne
Fig. 1. Map of the study area – East Kolkata Wetlands. (Source : East Kolkata Wetlands Management Authority (EKWMA) (http:/
/ekwma.in/ek/, accessed 8th June, 2017))
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
diseases, especially Malaria (DEC, 1945). Interestingly, the
then brackish water fisheries were also responsible for reducing
the spill area and compounded with the dwindling upland flow
caused the death of the tidal creek.
Kolkata city has a natural gradient towards east, although
the sewage of Kolkata city was initially discharged in the
River Hooghly on the western side of Kolkata. Incidentally,
River Hooghly was used as the source of drinking water for
the Kolkata city. Sensing health problem and in order to
utilise the natural gradient of Kolkata City, the then British Raj
started constructing a number of canals and Nalas from the
end of 18th century towards eastern side. These canals were
ultimately connected to the Bidyadhari Channel and in the
process, the Bidyadhari started carrying only the city sewage
(Ghosh, 1999).
During the beginning of 20th century, in order to meet up
the demand for water, ‘a leading fish producer of that time was
successful in growing fish in a large water area using city sewage
in the same process sequence as it is done today’ (Ghosh, 1999).
That ‘innovation’ was readily followed in case of other water
bodies. Hence, these water bodies literally turned into sewage-
fed fisheries within a very short time and thereby changing the
character of the entire area from coastal wetlands to freshwater
wetlands. That practice is still going on.
At the same time, considering the vast wetland area in the
city fringe as “wasteland”, one square mile of this area was
leased out to one private entrepreneur in 1868 for making room
for solid waste dumping (Furedy & Ghosh, 1984) which became
known as “Dhapa”, wherein solid waste of Kolkata City was
recycled through garbage farming till recent times, although
disposal of garbage over here has been stopped now during
last six years.
ECOSYSTEM SERVICES OF EKW
The ecosystem services of EKW has been described in
details in number of literatures (Furedy & Ghosh, 1984; Gosh
& Sen, 1987; Ghosh, 1999; Edwards, 2001; Bunting et al.,
2001; Nandeesha, 2002; Bunting et al, 2002; Bunting et al.,
2005; Kundu et al., 2008; Edwards, 2008; Kundu, 2010; Kumar,
2010; Bunting et al., 2010; Bhattacharya, 2012; Ghosh, 2017).
It has already been stated that EKW is well known because of
the sewage-fed fisheries over a large part of the area, which
are also described by some authors as ‘Sewage Treatment
Fisheries’ (STF) (Ghosh, 1983). In fact sewage-fed fisheries,
locally known as bheries, constitute the most important
component of natural resource recovery system here. The basic
system is that the city sewage from the south-central part of
the city is collected and discharged from higher level into the
Dry Weather Flow (DWF) canal at Topsia pumping station
which flows towards the eastern part of the City and reaches
Bantala, wherein a number of other canals from central and
northern part of the city join DWF. By operating the sluice
gates at Bantala, the sewage is diverted into the ‘Fishery
Feeding Channel’ which flows into EKW with a network of
sewage carrying canals. The city sewage enters into the
fisheries through a bamboo screen and get stored there for
about a month or so and thereafter get cleaned through
several well established steps and methodology (Sarkar et al.,
2009; Vicziany et al., 2017). Physico-chemical factors like
temperature, pH, Dissolved Oxygen etc play critical role
and have significant influence in this cleaning process to
mitigate environmental degradation due to the unutilised
nutrients available in the city sewage (Gloyna, 1971). However,
the rate of biodegradation at EKW has been found to be
very high and even higher than in vitro experimentation and
thereby unique in nature. ‘Wastewater gets stabilized (at
EKW) within 10 days of retention’ (Sarkar et al., 2009). It
has also been reported that due to adding of lime to the soil of
the fish ponds before the release of raw sewage into the
fisheries, the pathogen/ faecal coliform get reduced by 96-99%
(Ray Chaudhuri et al., 2012). It has also been argued that
‘Groups of Sulphur Reducing Bacteria’ present within city
sewage also help in amelioration of the EKW environment since
the acid rain, a product of the sulphur fallout from Kolkata’s
automobile exhaust, are getting neutralised with these group
of bacteria. Thus such sewage treatment fisheries ‘results in
fish production and purification of the waste water up to 99%
in terms of faecal coliform count and to a large extent for other
parameters’ (Pradhan et al., 2008). The metal content in the
muscles of the surface feeder and bottom feeder fishes were
comparable to that of the same variety from rain water fed
ponds, indicating safe use of the waste water (Ray Chaudhuri
et al, 2012).
The effluents from these fisheries are 99% free from
BOD and are being used for irrigating the paddy fields
downstream. It has been estimated that fisheries or bheries
constitute about 32% of EKW, while 39% of EKW area is
under agricultural practices (Dasgupta et al, 2011; Mukherjee
& Dutta, 2016). It has been estimated that EKW removes
around 237 kg of BOD per day and thereby EKW acts as a
natural kidney for the City of Kolkata (Bhattacharya et. al,
2012). Seventy four percent (74%) of the working population
of the adjoining villages are dependent on EKW for their
livelihood (Bhattacharya et al., 2012). The maximum average
yield of fishes of 6.48 MT per ha has been recorded in the
bheris (Ghosh, 1999). Apart from production of fishes, EKW
also provides many other environmental services including an
important habitat for biodiversity (Kundu, 2008; Sengupta,
2018).
REVISITING EAST KOLKATA WETLANDS – MANAGEMENT OPTIONS WITH HOLISTIC APPROACH 131
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
132 SOMENATH BHATTACHARYYA
CONSERVATION EFFORTS AND THE
PRESENT STATE OF AFFAIRS
Land reclamation for conversions of wetlands into paddy
fields and for urbanisation were going on unabated until about
1980s when protest against the conversion of the EKW started
‘to challenge the trend of real estate takeover of peri-urban
wetlands’(Ghosh, 2016). In a landmark Judgement in a Court
Case related to the construction of a World Trade Centre (WTC)
converting some wetland area, Calcutta High Court made an
injunction over the entire area of 12,500 hectares in January,
1992 disallowing any kind of changes in the existing land use
pattern without the consent of the High Court. That rule is still
in vogue and EKW area is thus blessed with the immunity
against any kind of conversion. But in spite of such injunction,
illegal construction is rampant within the EKW area and
instances of permanent dewatering of the water bodies within
EKW area for urbanisation are not rare.
OVERZEALOUS PERCEPTION ABOUT ITS ROLE
Ecosystem values of EKW have been well described in
different literature and public forum for about last 35 years or
so. ‘The agriculture and fisheries activities in the Calcutta
wetlands provide the city with two outstanding urban facilities:
treatment of the city’s sewage, and nutrient recovery from which
an abundant supply of fish and vegetables is the end product….
The integrated resource recovery system provided by the
agriculture and fisheries activities, making use of city waste,
provides a comprehensive answer to the city’s sanitation and
resource recovery needs’ (Ghosh, 1993). There cannot be any
doubt regarding the ability of this innovative process developed
traditionally by the local people for resource recovery from
the waste about one hundred years back, which may be
designated as Municipal Waste Recycling, now being
recognised and mandated in India (in recent Solid Waste
Management Rules, 2016 of Ministry of Environment & Forests
and Climate Change, Government of India). However, the
procedure being applied in EKW raised many scientific
questions and queries about safety of the consumers and
handlers from the point of public health engineering. It is always
better to seek solutions based on the scientific knowledge of
21st century.
CHANGE IN APPROACH TOWARDS
WASTEWATER AQUACULTURE
Since seventies of the last century, wastewater-fed
aquaculture has been considered to have great potential for
future since it produces low-cost fish for the urban poor, it
provides a low-cost method to treat wastewater and it reduces
environmental pollution by way of treating wastewater that is
often disposed directly into environment (Edwards, 2000).
Fishes grown out of sewage-fed fisheries are considered as
source of cheap proteins and one of the major solutions to
replenish the deficiency in dietary proteins in third world
countries. During seventies of the last century the experts all
over the world turned towards waste, especially municipal
wastes from cities as means for production of food and thereby
offering nutrition to the people belonging to lower economic
strata at an affordable price. An aspiration was developed
amongst the city planners to promote the coupling between
waste generation and food production which accord with
sound policies on food, nutrition, and environmental
protection and even it was advocated that the Asian cities,
which are third world cities can learn from the existing
practices, like EKW for such resource recovery in their own
backyard. (Furedy & Ghosh, 1984). ‘Such practice may
eventually lead to the development of alternative agricultural
systems that could surpass the contribution of the green
revolution to World Food Production’ (Newcombe and
Bowman, 1978). Even fish production of such wastewater-fed
fisheries was thought to have in the same tune with freshwater
fisheries so that the ‘Sewage Treatment Plants of rapidly
growing cities will become huge centres for Food Production’
(Borgstrom, 1978).
World Health Organisation has also advocated to use raw
sewage for fisheries and expressed the opinion that ‘Excreta
reuse in aquaculture will become an increasingly important form
of waste disposal, water pollution control and food production
in the next two decades in many parts of the world’ (IRCWD,
1985). But with advancement in knowledge in public health
and community sanitation, concept of waste recycling and the
procedures started changing from the beginning of this century.
Even the staunch advocates of wastewater-fed aquaculture
started changing their opinion and the rosy picture regarding
wastewater-fed aquaculture started fading away. ‘The current
reality is somewhat different and wastewater-fed aquaculture
is generally in decline or being actively phased out’ (Bunting
et al, 2010). The management issue of EKW needs to be looked
into in this perspective also.
ISSUES OF CONCERN
Using Untreated Wastewater in Fisheries
A number of questions have been raised regarding the
present quality of wastewater that is being used in the
wastewater-fed fisheries of EKW. ‘We are no longer speaking
about raw sewage of the kind that first entered the Wetlands
when the bheries were established in 1929-30’ (Vicziany et
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
al., 2017). The sewage that enters the fisheries at present also
contains non-biodegradable matter including heavy metals and
thus has the potentiality to contaminate the fishes. Use of
similar type of sewage for growing vegetables has resulted in
heavy metal pollution of the vegetables grown out of it
(Gupta et al, 2008).
Construction of outfall scheme of Kolkata City as proposed
by B N Dey, took place in the year 1943-1944 which increased
the availability of wastewater for these fisheries (Bunting et al,
2010), but did not even consider using raw sewage for the
fisheries. That is why the Bantala Sedimentation Tanks (Fig.2),
(which is still a classical example of resource recovery system
through different ways) were constructed even about eighty
years back for centrifuging of the raw sewage after flocculation
and making arrangements for diverting only the effluents from
the sedimentation tanks to the fisheries. Thus, the idea of
utilising raw sewage for fish production was not even accepted
by the then planners and developers and the present system of
free flow of sewage to fisheries, which is going on presently
after the sedimentation tanks (Fig.2) became inoperative, was
not a part of traditional resource recovery system, although
seldom forgotten now while describing EKW system.
Calcutta Leather Complex and Heavy Metal
Contamination
The ‘kidney’ of Kolkata City was designed in an innovative
manner during early part of last century. The first sewage-fed
fishery started and proved successful in 1930 (Ghosh and Sen,
1987). ‘The traditional fisher folk learnt either by design or by
accident, the sewage waters enhanced the productivity of
fish ponds..’ (Furedy and Ghosh, 1984). Thus, the fisheries in
EKW started using the sewage about one hundred year’s
back. It is not rational to consider same composition of
present day wastewater as that of sewage of one hundred years
back when 32 percent of the Kolkata’s wastewater is from
industrial units (Talapatra and Banerjee, 2007).
Industries like tanning, electroplating, battery manufacture,
metal handicrafts, motor servicing, dyeing, printing and
bleaching, moulded rubber factories, plastic footwear
manufacture etc are in operation in Kolkata (Dasgupta et al.,
2011). Tanneries have the most prominent presence in Kolkata
and have been regarded globally as one of the worst polluter
(Vicziany et al, 2017). Tanneries also release Lead (Pb) and
Chromium (Cr) in the effluent (Dasgupta et a.l, 2011).
‘In Calcutta, there is an unregulated discharge of effluents
from thousands of small-scale factories; also 600 tanneries
discharge 150 kg of the heavy metal Chromium daily into an
urban wastewater channel that drains into fish ponds’ (Edwadrs,
2001). Central Leather Research Institute in their report to the
Government of West Bengal has indicated a total number of
538 tanneries in Kolkata in the year 1993 in four areas of the
city namely Tangra, Tiljala, Topsia and Pagladanga (CLRI,
1993) and all these tanneries were supposed to be relocated
within Calcutta Leather Complex (CLC). Construction of the
CLC began after the Supreme Court of India ordered the
Government of West Bengal in 1992 to relocate the tanneries
that had grown in the Topsia, Tangra and Tiljala areas inside
the Kolkata municipality (Sahasranaman and Emmanuel, 2001).
Even in the year 2013, it has been reported that CLC was not
fully operational and there was still continued operation of
illegal tanneries outside CLC (Roy et al., 2013). The effluents
from the tanneries located within CLC are all not coming to
Central Effluent Treatment Plant (CETP) and the polluted
effluents may get its way into SWF canal (Vicziany et al., 2017)
since these are being discharged directly in the rainwater
channels (Bagchi and Banerjee, 2013). Even the CETP of the
CLC is inadequate to tackle the pollution load (Roy et al., 2013).
Thus, all the pollution load especially the heavy metals from
the tanneries including those located into CLC are coming to
the wastewater and contaminating the wastewater-fed produces
(Patra et al., 2001; Chatterjee et al., 2006; Talapatra and
Banerjee, 2007; Kumar and Mukherjee, 2011; Kumar et al.,
2011; Maiti and Banerjee, 2012; Nath and Bhowmick, 2013;
Saha et al., 2015; Aich et al., 2015; Dutta et al., 2017). Even
the genotoxic effects due to such heavy metal contamination
have also been indicated in several studies (Talapatra and
Banerjee, 2007; Chowdhury et al., 2008). Thus, an originally
proposed “Zero Discharge” industrial complex has been
ultimately polluting the entire region including a Ramsar Site
through pollution load. Unfortunately, there is hardly any
enforcement from the authorised agencies to safeguard the
environment.
Co-ordination Between Different Public Authorities and
Stake Holders
There is no separate canal for inflow of wastewater into
Fig.2. Bantala Sedimentation Tank
REVISITING EAST KOLKATA WETLANDS – MANAGEMENT OPTIONS WITH HOLISTIC APPROACH 133
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
134 SOMENATH BHATTACHARYYA
the fisheries and the outflow canal for effluents. Fishery Feeding
Canal (FFC) starts from the Bantala Lock gate. FFC is being
used for both the purposes of entry and exit of wastewater into
the fisheries. Due to free flow of raw wastewater containing
sludge and other suspended solids into these fisheries over a
long period, most of the suspended solids and impurities got
deposited on the beds of the fisheries and also on the canal bed
increasing the bed level. As a result, unless the wastewater is
released into the FFC from a higher level, it would not be
possible for wastewater to enter into the fisheries, having higher
bed level. The sluice gates over DWF canal at Bantala help in
maintaining the desired heights of level of wastewater. All the
sluice gates, except the North-Eastern most one, over DWF
open into the SWF canal for discharging wastewater into the
larger SWF canal while NE gate only opens into the FFC. For
the purpose of increasing the water level in DWF, all lock gates
over DWF are kept closed for a long duration. Only when the
wastewater level attains a height of more than 9.5 feet in the
graduated scale put on the wall of the lock gates, it would be
possible for wastewater to enter into the fisheries. However
long duration of keeping the lock gates over DWF closed can
lead to water stagnation and consequent water logging within
City of Kolkata. During releasing the effluents from any fishery,
the water level in the FFC needs to be lowered to a great extent
so that effluent from fishery can now moves in the opposite
direction. For this, all lock gates over DWF needs to be kept
opened to lower the water level so that effluent from fishery
can ultimately get discharged into the SWF canal through the
same canal. The entire process is having inner contradictions
since all the fisheries are privately owned. In situations, when
a fishery owner wants to have this ‘Liquid Gold’ (Mukherjee
& Dutta, 2016) in his/her fishery by keeping the Bantala lock
gates closed, the adjoining fishery may think otherwise to
discharge the effluent and thereby wants to keep open the
Bantala lock gates leading to confusion and sometimes even
chaos. Undoubtedly, Bantala lock gate is the lifeline for EKW,
since if the lock gates are kept open for a longer time, the
fisheries within EKW will starve and ultimately have their
natural deaths even with all other conservation measures.
Presence of different operators and stake holders without
having any formal coordination mechanism complicated the
situation further. Fishery Owners, labourers working in
fisheries who actually know this technique traditionally,
Citizens of Kolkata, different departments of Government of
West Bengal, such as Irrigation & Waterways, Fisheries,
Kolkata Municipal Corporation etc. and the villagers living
within EKW are all stakeholders to this system. But so far no
attempt has been made from any quarter to establish any
coordination mechanism between different stakeholders for
conflict resolution towards sustenance of this system.
Land Acquisition at EKW and its Sustenance
Land acquisition notice served in February, 1961 for
building up Salt Lake City is still in vogue, although not
enforced over the entire area for reclamation and conversion
due to public awareness and Court Order. As a consequence,
the land ceiling act could not be enforced here and the erstwhile
Zamindari system is still operative in EKW. There is no
distribution of patta, although in some areas some kind of
leasing of land on local arrangement basis is in operation. Such
unofficial leasing is usually influenced and carried out at the
whims of the local political masters. Due to impugned status
of land, no bank loan is available against land ownership
documents. As a result, even the maintenance of these fisheries
like large scale desilting and transportation of the refuse,
embankment repairs etc cannot be carried out. The desilted
refuse is dumped on the embankment leading to shrinkage of
the water area. An atmosphere of uncertainty looms over the
entire area concerning future of the system.
Loss of Carrying Capacity but Increased Dependence
In a hypothetical situation, if there is no pollution from any
source whatsoever, is it possible for EKW to take care of
‘treatment’ of the entire volume of sewage of Kolkata City? At
present, there are about 254 number of fisheries covering 3800
hectares of area (Edwards, 2008), although some different
figures have also been reported like 3900 hectares of
wastewater-fed fisheries (Bunting et al, 2010); 2,481 ha of area
under fish ponds out of which 377 ha have been rendered
redundant due to siltation (Kumar, 2010) etc. Considering the
area covered by sewage fed fisheries presently to be 3,500 ha
and each having an average depth of 1 meter, total wastewater
holding capacity of the fisheries is 35,000 million litres.
It has been estimated that total quantity of sewage generated
in Kolkata City in the year 1875 was 68 Million Litres per Day
(MLD) which was increased to 590 MLD in 1943 and in the
year 2011, total quantity became 1112 MLD (Dey & Banerjee,
2018). At present, only 55% of the City Area having about
50% of City’s Population is covered with sewerage network.
Out of 141 Municipal Wards, sewerage system is yet to be
developed in new KMC wards, i.e. from KMC Ward no. 101
onwards. Thus, amount of wastewater generation within city
area is increasing day by day. Presently, it has been estimated
to be around 1300 MLD.
With a total capacity of 35 Million Litres, it is difficult to
treat the entire wastewater of the Kolkata City by EKW when
‘these fisheries require 2 – 3 weeks to turn anaerobic wastewater
to aerobic through development of plankton & subsequent
secondary fertilization at intervals by taking 1 to 10% of pond
capacity’ (Nandeesha, 2002). ‘An estimated 30 – 50% of the
sewage from Central Kolkata only is treated and reused by
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
fish ponds of EKW’ (Edwards, 2008). Even it has been
indicated that ‘of the total flows (of sewage from Kolkata City),
more than 95% is siphoned off from the wetland to reduce
water logging within the Kolkata City’ (Kumar, 2010). It is
hardly possible for the entire quantum of wastewater from
Kolkata City to be accommodated within the wastewater-fed
fisheries of EKW for ‘bioremediation and treatment’. However,
overestimating the efficacy of this system ’Kolkata was not
provided funds for setting up conventional sewage treatment
plant under the Ganga Action Plan’ (Sengupta, 2018)
Status of Sewage Treatment Facilities in Kolkata
Kolkata City is being developed practically without any
modern treatment facility. Existing sewage treatment plants
and their capacities can be estimated from the following
Table 1.
fish farming at EKW is also not remunerative to the extent of
people’s present day expectation. One of the major reasons
behind this is that the present productions from these fisheries
are not at par with other kind of fisheries. ‘Some EKW farms
attain annual yields of 5–7 ton ha-1, but mostly farms produce
3 – 5 tons ha-1 year-1, only one third to half of sustainable
production possible from well managed semi-intensive fish
culture’ (Bunting et al, 2010). This may be due to lack of proper
depth of ponds or may be due to some other reasons. Although
the villagers of adjoining villages were dependent on this
wetland, a recent survey indicated that younger generation are
not willing to carry on this traditional practice. It has been
observed that only 19.6% of those engaged in traditional
vocations are young (Dey & Banerjee, 2018). ‘If younger
generation is more interested to acquire skills suitable for
modern vocations (and get employed in other sectors), then
that ecosystem balance would be disturbed even without any
significant change in the pattern of land use…’ (Dey &
Banerjee, 2018). A serious introspection is required to look
into this particular aspect.
RECOMMENDATIONS
EKW resource recovery system is apparently time tested
and has so far not created any perceptible epidemiological issue,
although it has been argued that such long term wastewater-
fed fisheries may contaminate the groundwater (Sikdar et al,
2001; Sahu & Sikdar, 2008; Sikdar and Sahu, 2009). Due to
presence of a thick impervious clay layer below Kolkata, such
a possibility has been mostly ruled out. This paper is not meant
for writing an obituary on EKW, rather this is meant to devise
a robust management system for sustenance of this system for
coming days. Unfortunately, till date finding solution to any
problem at EKW always depends on the ‘Traditional
Knowledge’ and ‘Peoples’ wisdom’. Seldom, it is understood
that the farmers cannot know everything traditionally. ‘…The
farmer will not know that which he cannot observe fully and
completely (for example).… the case of microscopic entities’
(Richards, 1979). Thus, it is not possible for the farmers to
understand the problem of heavy metal contamination or
microbial contamination. Traditional knowledge cannot equip
the fish farmers to understand risks associated with sewage
contaminated with heavy metals or pathogenic microbes. Fish
farmers need to be educated for taking appropriate action
against microbial contamination and surely it would be possible
for them to act as per the need as noted ‘in changes in the
habits of Indian dairy farmers in their handling of raw milk
which suggests that they can and do respond to new information,
especially if it is linked to appropriate price structures’ (Vicziany
et al., 2017).
Table 1. Number of treatment plants as available presently in Kolkata (Dey
and Banerjee, 2018)
STP Town STP Capacity STP Commissioned/ Mode of
of New Plant Not Commissioned Wastewater
(MLD) Disposal
Garden 47.5, ASP Commissioned Via Monikhali
Reach Canal to River
Hooghly
South 30, OP Not Commissioned Discharged into
suburban (E) Churial Khal
extension which
leads to River
Hooghly
Cossipore 45, ASP Commissioned Disposed to
Chitpur Bagjola Canal
(Bangur) which leads to
River Hooghly
and partly used
for irrigation
ASP = Activated Sludge Process; OP = Oxidation Pond
Altogether arrangement for treatment for 122.5 MLD of
sewage plus 2 MLD STP, as planned at Baghajatin, has been
made which is <10% of total city sewage generated per day.
As a result, most of the wastewater from Kolkata City is getting
discharged into River Bidyadhari totally in untreated condition
and polluting Sundarbans (Roy et al., 2018), another important
Ramsar wetland and a world heritage site.
Change in Vocation
Pisciculture at EKW is not so remunerative presently in
comparison to other areas. ‘The average household income of
the wetland communities (Meaning EKW) still stands
equivalent to less than 70% of the State Average’ (Kumar, 2010).
EKW is located in proximity of Kolkata City. Wastewater-fed
REVISITING EAST KOLKATA WETLANDS – MANAGEMENT OPTIONS WITH HOLISTIC APPROACH 135
SPEC.PUBL.GEOL.SOC.INDIA, NO.9, 2021
136 SOMENATH BHATTACHARYYA
The heavy metals that end up in the sewage need to be
contained at source, namely at the point at which industrial
effluent flows into the open drains and canals of Kolkata and
its environs. West Bengal Pollution Control Board (WBPCB)
and Central Pollution Control Board (CPCB) need to monitor
the CLC as well as other tanneries within the city to get rid of
heavy metal menace. At the same time, it is also high time to
explore Green Technologies for tanning of hides at CLC to get
rid of heavy metal menace altogether.
A coordination committee with representation from all the
stake holders need to be constituted under the umbrella of a
nodal department like Environment Department or Fisheries
Department to ensure and monitor the release of wastewater
into the DWF canal at Topsia pumping station and thereafter
diverting it into FFC at Bantala Lock gate from a higher level.
It is required to prepare a detail drainage map of EKW so
that the bheries can be provided with separate entry and exit
canals for proper arrangements of nutrient supply and effluent
discharges from these fisheries.
Proper initiatives need to be undertaken for developing
technologies which can enhance fish production in the fisheries
of EKW without disturbing the ecological balance. It would
be better if a sophisticated laboratory be set up within EKW
which would look into the food safety of the fishes as well as
vegetables and other food products being produced here.
An appropriate tagging and fair pricing of the fishes from
EKW may help in increasing the incomes of fish farmers here.
The tagging and marketing should be such that people will
feel proud to purchase the fish and other products from EKW
since their contribution will help in waste recycling and thereby
helping in environmental protection.
The land acquisition status needs to be reviewed. Change
in land use pattern of EKW and conversion of wetland areas
for real estate need to be stopped immediately.
Actual quantum of wastewater that can be used in these
fisheries for biological treatment needs to be ascertained and
the rest needs to be treated before discharging into the
environment.
Different kinds of management options for EKW need
to be explored with the objectives of enhancing the incomes
of the fish farmers and financial turn over from the system,
but at the same time preserving the ecological character of
EKW.
Wastewater related services need to be charged on the
residents of Kolkata so that stakeholders can understand the
value of EKW. Payments for ecosystem services (PES), such
as through introduction of a wastewater treatment charge for
city households may be introduced.
The core issue of the intervention must be what measures,
incentives or disincentives are appropriate to avoid transition
to externalising technologies and to counter the erosion of social
capital, thus promoting continued resilience of the EKW system
in a constantly evolving situation. An objective and holistic
approach can only guarantee the sustenance of EKW.
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