Waste Water Processing: A Necessity On Today’s Context
Wastewater including domestic sewage and waste from mainly agro-industrial areas can be purified step by step.
Purified sewage or agro-industrial water can be reused after proper treatment for pisciculture as nutrient and mineral contents of water are recycled.
With the help of wastewater treatment method not only we can solve our water shortage problem but also we can use this water for pisciculture.
Project Location
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PLACE: Mudialy Fishermen’s Co-operative Society Ltd.(MFCS)
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ADDRESS – Nature park, Taratala Road, Kol – 700088.
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This place is situated in the southwestern fringe of Kolkata. It is mainly a waterlogged wasteland filled with water hyacinth used by Kolkata Port Trust for dumping garbages.
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MFCS is successfully carried out this venture over several years.
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The main activity of this co- operative is to produce quality fish by using wastewater - because of these above-mentioned reasons I have chosen Nature Park as my field study
Selected Water Quality Parameters
Flora & Fauna
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FLORA: Various kinds of algae (mainly Chlorophyta- green algae), Azolla (Azollapinnata), water hyacinth (Eichhorniacrassipes).
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FAUNA: The dominant types of fish fauna identify in their ponds are 14, prawn and crat fauna are three, snail fauna is three, and snake fauna is three. Besides this more than one species of fish – namely, ‘Chanda’, ’Mourala’ and ‘Punti’ which are known to be freshwater varieties of sensitive nature.
Treatment Process
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Waste water come into the inlet pond.
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At first waste water passes through six ponds known as ‘ANAEROBIC TANKS’.
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Within anaerobic tanks water is treated with lime which serves to neutralise acids while precipitating various metals into solids that can be recovered.
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Water hyacinths are kept in the tanks. Hyacinth is a well known saprophytic plants that derive nutrition from dead and decaying matter, so these plants are used to facilitate the absorption of oil , grease and toxic materials.
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The second tank into which water moves from first through a narrow passage(culvert at the upper level).
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This place is used to rear exotic, predatory, omnivorous fishes like singi(Heteropneustes), magur (Clarias sp.),koi ( Anabas sp.) which are used as natural pollution indicators.
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After that water flows into third pond through a canal which is filled up with saprophytic water hyacinth.
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By this way the water quality is improving in each step and mineral contents of the waste water can be recycled and now water can be utilised for pisciculture.
Schemartic Diagram of Mfcs
Actual View of Waste Water Treatment In Mfcs
Pisciculture In Processed Waste Water
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Regular fishing in wetland areas plays a vital role in purifying the pollution of environment as well as maintaining ecological balance.
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Fishes like catla (Catlacatla), Rohu (Labiorohita),bata ( Labeobata ),mrigal (Cirrhinusmrigala),common carp (Cyprinuscarpio), silver carp (Hypophthalmichthyesmolitrix) etc.
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It has been observed that there is less possibility of disease occurence in fishes because this water is totally purified.
Pisciculture in Mfcs
Modern Technologies Which Should Be Adopted For Future Progress
The main part of sewage fed fish culture is pond preparation. When fish grow is slowest, in winter farmers have to prepare the pond by draining, desilting, tilling and drying in sun. The pond dikes are consolidated.Silt traps (perimeter canal along the dikes) 30-40 cm. and 2-3 meter wide deep are dug, as they get restored during normal harvesting of fishes. Aquatic weeds are grown along the pond dikes such as,water hyacinth (Eichhornia). This save the dikes from wave, give shelter to fishes against high temperature and maintain the dissolve oxygen level by photosynthesis. Then the sewage is passed into the pond from the feeder canal through the bamboo sluice after the pond preparation. There is a self-purification characteris of sewage which is takes place in presence of sunlight atmospheric oxygen. Then the pond is considered ready for stocking,when the water becomes green due to photosynthetic activity,.
All the species of Indian major carps such as, Hypophthalmichtysmolitrix, Ctenopharyngodonidella , Cyprinuscarpio are chosen to be cultured but the ratio of Mrigal is kept greater than exotic cars.Pangasiushypophthalmus is also cultured by some farmers to get rid of mollusks. The farmers keep very high stocking density as the sewage contains increased content of nutrient, i.e. After stocking, sewage is taken to the ponds throughout the culture time at a regular interval of 110% of the total water volume of the pond, water level is maintained by continuous inflow and out flow in bigger ponds. By examining the water colour, temperature, transparency, and depth, the condition of sewage is differentiated. The cultured fishes do not need any supplementary feeding, due to high contents of nutrients in sewage. Nevertheless, when the potential sewage is lacking in rainy season, they are fed with supplementary feed. The fishes are most susceptible to bacterial diseases, but surprisingly the occurrence of bacterial or any other disease is not common in sewage-fed fish farms,because the fishes are adopted by their own immune system. Fishes are cultured and harvested throughout the culture period guiding to serialized culture and traditional harvesting.
Next important part is the production of the pond that is depend upon,quantity of sewage utilized in ponds, the potentiality of sewage, depth of the ponds, fish species cultured,number of fingerlings stocked (stocking density).There is straightforward connection in between the inflow of sewage and the productivity of the pond. The dissolved oxygen content influence the productivity of the pond. Marketing of the pond is relatively important to sewage fed fish culture. For a few days for their deodorisation, the farmed fishes are kept in depuration ponds. The different sized fishes are harvested and sold based on the market demand.