POLLUTION OF OOTY LAKE AND RESTORATION

 

                                                Dr.T. Meenambal P.Hd **

                        Asst. Prof in Civil Engg, Government College of Technology,Coimbatore

 

Ms.Hemalatha M.E

Teaching Research Associate, Government College of Technology, Coimbatore

 

INTRODUCTION

  

                     The Ooty Lake is more than a one and a half centuries old. It was formed by blocking a mountain stream. The lake has a shoreline of 5 km long. It has maximum depth of 15m, but in the innermost parts of the lake the depth is about 6 to 7m. The lake is a huge and renowned tourist attraction. On a lean day it draws about 500 visitors and in peak season the number of daily visitors exceeds 2000. 45 oar boats and 10 motor boats are at the disposal of the tourists from 9.00 am to 5.00 pm on all days of the year.

 

PRELIMINARY INVESTIGATION

 

                  The lake receives its water from the surface runoff in the following areas            

-       Part of Larks Hill

-       St. Mary’s Hill

-       Missionary Hill

-       Fern Hill

-       Elk Hill.

     

                Besides the above runoff a perennial stream from upper Koddappamund Hills joins the lake. Until it reaches the Ooty municipal limits at Vannarpet, the stream water is clear and free from pollution. It is even used for domestic purpose in these areas.

                 At Ooty the stream joins the channel, which in turn joins the Ooty Lake at the south end of the lake.                 The Ooty channel is totally 2.6 km long from Vannarpet to the point where it joins the lake. It is over this 2.6 km length that the channel receives almost all the polluting material, which is passed on to the lake.

 

SOURCES OF POLLUTION

 

1.     The Nilgiri District Co-Operate Milk Producers Union Dairy (which handles 35,000 lit of milk / day and also makes by products like butter, ice-cream , cheese, etc ) discharges its wastes in to the channel.

2.     CTC workshops discharge oil & grease into the channel.

3.     CTC canteen discharges its wastes into the channel.

4.     Sullage from Railway Colony, Nazareth Convent etc., joins the channel in large quantities a few meters before its tail end.

5.     A broken sewer flowing full discharges profusely into the channel opposite to Alankar theatre.

6.     There are many unsewered establishments along the bank of channel, which discharge their wastewater into the channel.

7.     The Chairing Cross wastewater from a public conveyance joins the channel.

8.     As it passes through the bazaar the channel receives pollutants like washings from garages, street washings, garbage, etc.

 

TYPES OF ALGAE FOUND IN OOTY LAKE

 

        Chlorella

    Chrysococcus

    Scenedesmus

    Phaecus

    Navicula

    Synedra

    Coleps

    Daphnia

    Vorticella

    Coelastrum

    Melosira

    Anacystis

                Cholera and scenedesmus are the two types of algae which are most active in sewage stabilization ponds. Their presence in the lake water confirms pollution by sewage. 

          The presence of Melosira testifies the eutrophic condition of the lake since Melosira is fovoured by highly nutrient rich waters.

 

  CONTROL OF ALGAE

 

   Biological Control

   Physical Control

   Chemical Control.

 

 

Biological Control

 

          A wide variety of biological methods to control algae have been investigated. These include

 

  The use of pathogens (viruses, bacteria , fungi)

  Control through the feeding activities of grazers

  Control by the manipulation of inter - relationships among plants, animals and their environment

 

Biological Methods offer an attractive means of controlling excessive algae. To be successful biological control organisms (pathogens and grazers) must have a high rate of survival under a variety of conditions, be able to reduce the population of the problem species and be able to coexist with other native aquatic fauna.

 

 

Physical Control

 

         Physical Methods of algal control include the mechanical removal of algae (harvesting), application of dyes (light exclusion or limitation), the removal of bottom sediments (dredging) and the use of explosive charges of ultrasonic radiation.     

 

 

Chemical Control

·      The application of algaecides is the most widely used algal control technique.

·      The most popular of the chemicals are copper compounds especially copper sulphate. Potassium permanganate has been used with success in a few instances.

·      An algaecide should be species -specific, and species selective, nontoxic to other organisms in the food chain, be harmless to humans and aquatic organisms, have no adverse effect on water quality, not accumulate in lake sediments and be inexpensive and easy to apply.

 

 PARAMETERS MEASURED

      

                  In order to assess the degree of pollution quantitatively the parameters were measured.

 

1.     Bod5 @ 20c

2.     Cod

3.     Permanganate value

4.     Dissolved Oxygen

5.     Turbidity

6.     Total Solids

7.     Nitrogen and Phosphorus

8.     Oil & Grease

9.     pH

10.   Iron & Manganese

11.   Chloride

12.   Hardness

13.   Sulphate & Sulphide

14.   Bacteriological examination for Water Sample

15.   The microscopical examination to identify the types of algae present in the lake water

                        

RESTORATION METHODS

-       Total Elimination of External Loading

-       Invention in the lake ecosystem (aeration, Removal of the upper layer of sediment, etc)

 

Total elimination of external loading

 

·      It is imperative that the influent channel feeding the lake is totally free from any sewage, sullage, dairy waste etc.,

·      All unsewered establishments should be properly sewered and connected to the existing sewer system.

 

Intervention in the Lake ecosystem

 

               This can be done by the following methods

 

v Aeration of water

v Diversity of hypolimnic water

v Preparation of phosphorus in the lake

v Aeration of sediment

v Removal of sediment

v Covering of sediment

v Direct reduction of biomass concentration in the lake.

 

Aeration of Lake water

 

           Oxygen Depletion occurs in the hypolimnion due to decomposition of organic matter.

Some Aeration methods are

 

·      Destratification, where the cold hypolimnic water is pumped to the surface and mixed with the warm epilimnic water.

·      Pumping of hypolimnic water to the surface, where it is aerated by contact with the atmosphere and transported back to the hypolimnion.

·      Aeration directly into the hypolimnion.

 

Diversion of Hypolimnic Water

Hypolimnic Water is rich in nutrients and poor in oxygen.By replacing the epilimnic water with hypolominc water, the nutrient and oxygen balance should improve.

 

 

Precipitation of Phosphorous in the lake

Phosphates in the lake can be precipitated by the use of alumunium Sulphate

 

Direct reduction of the bio mass concentration in the lake

In hyper eutrophic lakes the primary production of the bio mass is significantly higher than grazing which means that the major flow of organic matter is through respiration and the cycle “primary production detritus mineralization” dominates food chain recycling.

 

Aeration of Sediments

The principles of sediment aeration are the same as described under aeration of hypolimnic water

 

Removal of Sediment

The storage of exchangeable phosphorous in the sediment may considerably delay a restoration phase, especially for shallow lakes with a long water retention time

 

Covering of Sediments

Covering of Sediment will be preventing the release of nutrients to the water body.

 

CONCLUSION

 

The hill stations in India are a legacy of British rule. We had not added to the list of hill stations after independence, but the worse part is that we have allowed the existing hill stations to deteriorate. Ooty is no exception to this.

 

The present condition of the lake is a mute testimony to the detioration of the quality of the environment in this hill station. In view of improving the environmental state of the lake and the hill station, the following considerations should be adopted

 

  The quality of the lake water should be monitored by measuring at fortnightly intervals important parameters like DO, BOD, COD, oil and grease, turbidity etc.

  Any sudden detioration in quality should be viewed seriously and measured taken to locate the source of pollution and prevent it.

  The restoration methods suggested should be implemented.

  Educating the lay public on the need to maintain a clean environment is important.

  The traffic condition of the lake should be improved.

  Entry of the materials containing nitrogen and phosphorous should be prevented. Unless eutrophication is arrested immediately, the lake may end up as a marsh.

 

A concerned effort to make the channel and the environment clean is indeed the need of the hour.

 

 

 

REFERENCES

 

 

1.     Raman.K.Raman, Controlling Algae in W/S Impoundments, Jour. AWWA, August 1985

 

2.     R.A.Ferrera and M.A.Dimino, A case study Analysis for Seasonal Nitrification: Economic Efficiency and Water Quality Preservation, Jour. WPCF, July 1985

 

 

3.     David.A.Belta, D.O.Variations in Stratified Lakes, Jour. ACCE, Env. Engg. Division, October 1970

 

4.     Eugene .P.Odum, Fundamentals of Ecology, W.B.Saunders Company

 

 

5.     John.A.Black, Water Pollution Technology, Reston Publishing Company

 

6.     P.H.Mc Gauhey, Engineering Management of Water Quality, McGraw Hill

 

 

7.     S.E.Jorgenesen, Lake Management, Pergusson Press

 

8.     Quentin.H.Pickering, Effects of Pollution on Freshwater Fish and Amphibians, Jour. WPCF, June 1983

 

 

9.     William.W.Walker Jr., Significance of Eutrophication in W/S Reservoirs, Jour. AWWA, Jan 1983