Lake Aeration Systems: Bhopal

Transcription

1 Sengupta, M. and Dalwani, R. (Editors). 8 Proceedings of Taal 7: The 1th World Lake Conference: Lake Aeration Systems: Bhopal Neelam Verma 1*, Bimlesh Kumar, Avinash Bajpai 3 and D.D. Mishra 4 1* Research scholar, Department of Chemistry, Govt. Geetanjali Girls P.G. College, Bhopal, India, Research Scholar, Department of Civil Engineering, IISc, Bangalore,561 India 3 Makhanlal Chaturvedi University, Bhopal, India, 4 Principal, Govt. College, Udaipura, Raisen, M.P., India neelamverma.chem@gmail.com, bajpai_avinash@rediffmail.com, bimk@civil.iisc.ernet.in, ddmishra.chem@yahoo.com ABSTRACT Bhopal popularly known as the city of lakes. The Upper lake was constructed in 11 th Century and mainly used for potable water supply while Lower lake was constructed in 17 th Century and mainly used for recreational purposes, together these two lakes are known as Bhoj Wetland. There are different types of aeration system had been installed in lakes of Bhopal under Bhoj Wetland Project. Aeration is the most important and indispensable operation unit for the treatment of wastewater and the main purpose is to dissolve the oxygen into the water to provide oxygen as the microorganisms decompose organic compounds as food. The present study is designed to ascertain the effectiveness of artificial aeration unit installed in Bhopal lakes for assessment of water quality. Various physico- chemical parameters like ph, DO, BOD, COD, nutrient concentration and bacteriological status were studied to assess the extent of deterioration in the quality of lake water as well as the performance system for improving water quality. Key words: Aerator, Bhoj Wetland, Dissolved oxygen, Nutrient, Physico-chemical parameters. INTRODUCTION Wetlands and lakes are a source of renewable resources, such as need for construction, fish for human consumption and pasture for grazing livestock. They are also important for leisure and recreation. Lake is characterized by a high degree of environmental variability, which is reflected in the annual resource availability. Anthropogenic impact on natural environments and especially on aquatic ecosystem is currently a topic of increasing concern. Deterioration of surface water and especially lake water quality has recently observed in many aquatories. The potential cause of such a situation are various point source pollution can be localized and well established, whereas the influence of non- point pollution is less obvious because of the inadequately defined direction and frequency of non- point source loading (Gantidis et. al., 6). With increasing industrialization, urbanization and growth of population, India s environment has become fragile and has been causing concern (Mohapatra and Singh, 1999). Availability of clean drinking water is still a dream in most parts of developing countries (Biswas, ). The requirement of water in all lives, from micro-organism to man, is a serious problem today because all water resources have been reached to a point of crisis due to unplanned urbanization and industrialization (Singh et. al., ). Bhopal is popularly known as the city of lakes. The studied lakes, Upper & Lower (designated as Bhoj Wetland) are urban water bodies. The Upper lake (Latitude 3 1' 3 16' N & Longitude 77 18' 77 3' E) has a catchment area of 361 sq. km. and water spread area of 31 sq. km. Upper lake is a main source of potable water supply for the city dwellers whereas Lower lake (Latitude 3 14' ' N, Longitude 77 4' ' E) ) has a catchment area of 9.6 sq. km and water spread area of 1.9 sq.km. It is mainly used for recreational purposes. Lower lake, Bhopal has deteriorated to a greater extent that in the (Pani et. al., ). To prevent the adverse environmental effect of development onto a lake system & its catchment area, the implication of Bhoj Wetland Project (Funded by JBIC, Japan) is considered as the most effective approach to ensure sustainable use of water resources and protection of lakes. Under the project different aeration systems have been installed in Upper and Lower lakes to restore the water quality and to increase the dissolve oxygen concentration of the lake water. Lake Aeration Systems in Bhopal Floating fountain: These are mechanical/electrical devices to facilitate pumping of the lower level

2 anoxic/low oxygenated water of the lake to expose them to the atmosphere. This type of equipment is suitable for improving oxygen level in deep water with less pollution load. The height of water jets allows water to come in contact with air and fall back in the lake (Fig.1). The continuous recycling of water and mixing helps in increasing dissolved oxygen level in the lake water. Figure.1 Aeration system in Bhopal Lake Ozonizer: In this system atmospheric oxygen is converted into ozone, which is injected in to the hypolimnion to control bacterial growth and to facilitate increase in dissolved oxygen level in water. In this process, initially ozone controls bacterial growth, subsequently ozone is converted into oxygen, which helps in increasing the dissolved oxygen level of the water. These devices are reportedly very effective in highly polluted and shallow water system. Floating fountain cum ozonizer: This is the floating fountain and ozonizer combination equipment is reportedly very efficient in deep polluted water. In this system water is being ozonized through ozonizer and after ozonation, pumps the lake water from a depth and expose them to the atmosphere. This facilitates much faster circulation of deep polluted water. Aeration is the most important and indispensable operation unit for the treatment of wastewater (Rao and Kumar, 7; Chen et. al., 3; Boyle, ; Reardon, 1995) and the main purpose is to dissolve the oxygen into the water to provide oxygen as the microorganisms decompose organic compounds as food. Plants growing in water produce oxygen by photosynthesis, and during daylight hours plants in aquaculture ponds often produce oxygen so fast that DO concentration in water rises above saturation. Water containing more DO than saturation for the existing temperature and pressure is said to be supersaturated with DO. When water is supersaturated with DO, the pressure of oxygen in water is greater than the pressure of oxygen in the atmosphere. Water also may contain less DO than expected at saturation. At night, respiration by fish, plants, and other pond organisms causes DO concentrations to decline. Thus, during warm months, night-time DO concentrations in ponds often are below saturation. In production ponds, DO may decrease by 5 1 mg at night, and in unaerated ponds, DO concentrations at sunrise may be less than mg (Boyd, 199). Such low DO concentrations can cause stress or mortality in culture species. According to er & Suttle (1987), water circulation as well as the aeration of ponds have been responsible for an increase in primary productivity, reducing stratification and causing greater soluble nutrient availability, decreases organic accumulation at the bottom and consequently, increasing fish production. Ponds without water circulation and without a supplementary aeration mechanism, show higher concentration of organic nitrogen, ammonia & nitrate (Avinimelech et.al., 199; Tavares et. al., 1999). MATERIALS AND METHODS Study Area: The study area selected was the Upper and Lower Lakes situated in Bhopal city, the State Capital of Madhya Pradesh, India. Two different sampling stations of Upper lake namely park (U1) & island (U) and both the stations possess floating fountain type of. In Lower lake, station one is Neelam park (L1) having floating fountain cum ozonizer (dual aeration system) and station two namely Khatlapura (L) having ozonizer type of. Water samples were collected from the site of aeration systems at different intervals and sampling was done six hourly i.e. pre, during and post operation of units. The water samples were collected from the surface and bottom layer in sterile jerry cans and transporting to the laboratory in an ice box to avoid unpredictable changes in physico-chemical and bacteriological characteristics. Physico-chemical and bacteriological characteristics For the assessment of water quality of two Lakes the samples were subjected to physico-chemical and bacteriological analysis following the procedure prescribed by APHA (1995) and NEERI manual (1991). The parameter namely ph, dissolved oxygen, biochemical oxygen demand, chemical oxygen 1961

3 demand, nitrate, total phosphorus and total coliform (MPN) were analyzed at regular intervals. RESULTS & DISCUSSION ph: ph ranged from , (U1) & , (U) in surface & bottom layer of Upper lake and a range from , (L1) & , (L) in surface & bottom layer of Lower lake as shown in fig.1. The value of ph was observed during the functioning period unit, which is within potable water limits. The USPH (United States Public Health Standards) limits for drinking water is (De, ). Higher ph values of surface water were explained on the basis of increased photosynthetic activity of the algal bloom, the carbonates of calcium and magnesium are precipitated from bicarbonates and water becomes more alkaline. ph controls the chemical state of many nutrients including dissolved oxygen, phosphate, nitrate etc (Goldmann & Horne, 1983). Dissolve Oxygen (DO): DO concentration of water body in the range of , (U1) & 7.-1., mg/l (U) in surface & bottom layer of Upper lake and a range from , (L1) & , mg/l (L) in surface & bottom layer of Lower lake as shown in fig. The maximum increase in the DO was recorded while the were operational. It is required for the metabolism of all aquatic organisms. In natural water resources the concentration of dissolved oxygen depends upon the physical, chemical and biological activities prevailing in the water body. Biological Oxygen Demand (BOD): According to fig 3 a range of.4-6., (U1) & , (U) in surface & bottom layer of Upper lake and a range from 1-1, 16-8 (L1) & , mg/l (L) in surface & bottom layer of Lower lake. The minimum value of BOD was recorded at the surface layer during the functioning period of the. BOD indicates the presence of microbial activities and dead organic matter on which microbes can feed. An inverse relationship was found between the dissolved oxygen concentration and biological oxygen demand values (Coscun et. al., 1987). Chemical Oxygen Demand (COD): COD indicates the pollution level of a water body as it is related to the organic matter present in the lake (WQM, Report, 1999). COD concentrations in the range of 46-76, 66-9 (U1) & 6-4, (U) in surface & bottom layer of Upper lake and a range from 6-8, 88-9 (L1) & 64-96, 8-11 mg/l (L) in surface & bottom layer of Lower lake as shown in fig 4. A significant fall in the COD was observed during the the aeration systems Changes in ph values in different stations of Upper & s during operational stages of NeelamKhatlapuraNeelamKhatlapuraNeelamKhatlapura Pre operation of Post Pre operation of Post Figure

4 Changes in Dissolved Oxygen in different stations of Upper & s during operational stages of NeelamKhatlapuraNeelamKhatlapuraNeelamKhatlapura Pre operation Post operation Pre operation Post operation Figure. Changes in Biological Oxygen Demand in different stations of Upper & s during operational stages of Tak i a Pre Tak i a Tak i a Post Neelam Khatlapura Neelam Khatlapura Neelam Khatlapura Pre Post Figure

5 Changes in Chemical Oxygen Demand in different stations of Upper & s during operational stages units Neelam Khatlapura Neelam Khatlapura Neelam Khatlapura Pre Post Pre Post Figure 4. Changes in Nitrate in different stations of Upper & s during operational stages of Neelam Khatlapura Neelam Khatlapura Neelam Khatlapura Pre Post Pre Post Figure 5 Nutrient concentration: The nitrate content of water was found in the range of , (U1) & , (U) in surface & bottom layer of Upper lake and a range from , (L1) & , mg/l (L) in surface & bottom layer of Lower lake (fig 5). The APHA standard drinking water quality guidelines for nitrate is 4 mg/lit. The lowest concentration of nitrate in water was recorded during functioning intervals of. Total Phosphorus content of water was found in the range , (U1) & , (U) in surface & bottom layer of Upper lake and a range from , (L1) & , mg/l (L) in surface & bottom layer of Lower lake (fig 6). For phosphate, United States Environmental Protection Agency (1985), suggested.8 mg/l for lakes as critical level for eutrophication. The amount of phosphate is comes out to be much higher than the acceptable limits. While comparing the three intervals of time a reduction was found in phosphate concentration during functional 1964

6 intervals. The introduction of large quantities of nutrients, mainly nitrogen and phosphorus to lake waters can cause eutrophication problems (Michelutti et al., ; Kouimtzis et al., 1994; Fytianos et al., ). Total Coliform (MPN): Most probable number was found in the range of 8-1, 1-18 (U1) & 1-14,1-14 per 1ml (U) in surface & bottom layer of Upper lake and a range from 1-, 18-4 (L1) & 14-18, 18-4 per 1 ml (L) in surface & bottom layer of Lower lake as shown in fig 7. The MPN values were found higher in Lower lake as compared to Upper lake. Changes in Total Phosphorus in different stations of Upper & s during operational stages of NeelamKhatlapuraNeelamKhatlapuraNeelamKhatlapura pre Post Pre Post Figure 6 Changes in MPN values in different stations of Upper & s during operational stages of Most Probable Number/1ml Nee lamkhatlapura NeelamKhatlapura NeelamKhatlapura Pre operation Post operation Pre operation Post operation Figure

7 CONCLUSIONS Physico-chemical parameters and nutrient concentration were found higher in Lower lake as compared to Upper lake. Aeration improves water quality of the lake as it increases Dissolved Oxygen concentration, reduces Biochemical oxygen demand and Chemical oxygen demand & it also reduces algae growth by removing it food (nutrient) nitrogen, ammonia and soluble phosphate are driven into the surface air and out of the lake and decreases bacterial population. Ozonizer is effective for controlling the growth of MPN count. However continuous inflow of sewage at Neelam park has affected the performance of floating fountain cum ozonizer but over all performance of this unit is significant. Therefore, the present study indicates the water quality of Upper & Lower lakes and impact of, which are more effective in improving the water quality of a degraded water body. REFERENCES American Public Health Association (1995). Standard methods for the examination of water & wastewater (1 th ed.). Washington D. C.: American Public Health Association. Avnimelech, Y., Mozes, N. & Weber, B., (199). Effect of aeration and mixing on nitrogen and organic matter transformations in stimulated fish ponds. Aquacultural Engineering, 11, Chen, Jyh-Herng, Hsu, Yung-Chien, Chen Y. F. & Lin, Chin Chu., (3). Application of gas-inducing reactor to obtain high oxygen dissolution in aeration process. Water Research 37, Coscun.I., Yurteri, S., Mirat,T., and Gurol, D., (1987). Removal of dissolved organic contaminants by ozonation. Env. Progress, 6(4), De, A.K. (). Environmental Chemistry (4 th ed), New Delhi, India. New Age International Publishers, EPA (1985). National Intrim Primary Drinking Water Standards as given by laws E.A. in Water Pollution & Toxicology, Environmental Protection Agency, USA Encyclopaedia of physical sciences & technology, nd ed. 17, 55. Fytianos, K., Siumka, A., Zachariadis, G., & Beltzios, S. (). Assessment of the quality chatacteristics of Pinios River, Greece. Water, Air and Soil Pollution, 136, Gantidis, N., Pervolarakis, M. & Fytianos, K., (6). Assessment of the quality characteristics of two lakes (Koronia and Volvi) of N. Greece. Environ Monit Assess, DOI 1.17/s Goldmann, C.R. and Horne, A.J. (1983) Limnology. London,UK : McGraw Hill Book Company. Khan, A.A., Bhatnagar, B. and Saxena, R. (1988). An introduction of Bhopal Lakes, Proc. Nat. Symp. Present Past and Future of Bhopal Lakes (Ed.) S.K. Kulshreshtha, pp Kouimtizs, TH., Samara, C., Voutsa, D., & Zachariadis, G. (1994). Evaluation of chemical parameters in Aliakmon river, N. Greece. Journal of Environmental Science and Health, A9 (1), Michelutti, N., Doublas, M., & Lean, D. (). Physical and chemical limnology of 34 oligoatrophie lakes in Canada. Hydrobiologia, 48, NEERI (1991): Manual of water and pollution control (Vol.1). Pani, S. and Mishra, S.M. (). Impact of hydraulic detention on water quality characteristics of a tropical wetland (). Pankaj Shrivastava, Ed. Environmental Pollution and its Management. New Delhi, India : ABS Publication. er, N.C. & Suttle, M.A., (1987). Design of air pumps for water circulation and aeration in aquaculture. Aquacultural Engineering, 6, Tavares, Sipauba, Freitas, L.H., F.M.S., A.M. & Braga (1999). The use of mechanical aeration and its effect on water mass. Rev. Brasil. Biol., 59 (1), 33-4 WQM, Report, (1999). Annual Report on Water quality monitoring of upper and lower lakes Bhopal. Vol. I and II 1966