Manonmaniam Sundaranar University, Sri Paramakalyani Centre of Excellence in Environmental Sciences, Alwarkurichi, Tirunelveli - 627 412. Tamil Nadu, India.
Received date: 30/5/2015; Accepted date: 20/6/2015 Published date: 28/6/2015
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Water samples were collected from the perennial river Tamirabarani over a distance of 125 km to assess the health status of the flow before it convergence with Bay of Bengal. Twelve sampling points were selected and the water samples were examined with physicochemical along with coliform content. Significant spatial and temporal variations were recorded; which classified the river quality in to 5 classes correspondingly “A” to “E”. Overall the quality of the river at downstream areas was poor compared with upstream locations with respect to its direct use value. Highest DO, BOD and COD levels were recorded as 10.47 mg/l, 10.02 mg/l and 17 mg/l respectively. Total and fecal coliform content were high are suburban and urban reaches as 2800 and 340 MPN/ml and 3500 and 2800 MPN/ml respectively during the study period and at different localities.
Water quality, River Tamirabarani, Oxygen demand, Domestic activities, Selfpurification, Coliform organisms
Water is an integral component of the environment, responsible for various life processes and hence persistence of life on this planet. Rapid urbanization, population explosion, and industrialization have increased the pollution stress and quality deterioration . Almost all Indian rivers act as carrier of raw or semi treated sewage, industrial effluents, domestic debris, and runoff from irrigational and urban areas [2-5]. The surface water pollution has been enlisted as one of the most serious problems in developing countries like India.
Running water is capable of purifying itself with distances through a process known as self purification. It is carried out by physical chemical and biological process which work simultaneously and purify the system as it moves downstream areas.
Rivers remain in the heart of societal development, especially, housing and other infrastructural aspects. All types of sanitization and disposal are randomly made through rivers without any second thought. River streams have been a natural source for water for all human activity. Therefore, it is important to investigate the pollution status of the rivers regularly considering the heavy disposal of garbage and pollutants.
Also, they are important in maintaining the soil fertility, forest and wildlife conservation activities. Therefore, river water quality monitoring program is necessary in order to safeguard public health as well as to safeguard the ecosystem . Water pollution due to anthropogenic activities at river Tamirabarani has been reported in earlier studies [7-15]. However, there is a need to study the self purification status and to classify the river basin, especially from the upstream area up to the convergence point. In that context, present study is planned to assess quality along with the self purification ability of the perennial river Tamirabarani and to classify the suitability of water for different uses.
Description of the Study Area
River Tamirabarani (Figure 1) is the only perennial river in southern parts of Tamil Nadu, India; one of the most important river because of its water flow throughout the year in comparison with other rivers (i.e., Chittar river, Vaigai river) in southern parts of Tamil Nadu; it supplies potable water and it is used for domestic, agricultural, industrial, and recreational purposes for two major districts (Tirunelveli and Thoothukkudi) with the population of about 42, 96, 261 (2001 census). The river originates at the eastern slops of Western Ghats at an altitude of 1725m above MSL between latitude 8°30'N and 9°18'N and between longitude 77°07'30"E and 78°15'E. The main river drains huge volume of water with its large network of springs with the catchment area of 4400 sq.km. Since all its main tributaries are arising from the Western Ghats, the river is prone to heavy flood especially during north east monsoon period. The river flows about 125 km through dense populated areas from Pabanasam region (Tirunelveli district) and convergence with the Bay of Bengal at Gulf of Mannar region. River Servalar, Manimuthar, Koraiyar, Gadana, Pachaiyar and Chittar are the principle tributaries of the river. Rapid urbanization, agricultural activities, domestic activities like bathing and washing, huge gathering for taking holy dip, open defecation, direct discharge of sewage and domestic remains increases pollution threat to the river and its tributaries.
The water samples were collected first week of every month at 12 different locations (T1-T12) of main river flow (Table 1 and Figure 1) during the period of January 2008-March 2009. Sampling, preservation, and transportation of the water samples to the laboratory were carried out as per standard methodologies.
The water temperature (T), pH and electrical conductivity (EC) were measured in situ with portable multi parameter meter (PCSTester 35 series; Eutech Instruments) and the turbidity was measured with portable turbidometer (TDY) (TN-100; Eutech Instruments). Chemical (dissolved oxygen (DO), suspended solids (SS), total hardness (TH), chemical oxygen demand (COD), biological oxygen demand (BOD), ammoniacal nitrogen (AN), nitrite nitrogen (NO2), nitrate nitrogen (NO3), phosphate (PO4), sulphate (SO4), calcium (Ca), magnesium (Mg), sodium (Na) and potassium (K)) and biological (total coliforms (TC) and fecal coliforms (FC)) analysis was carried out based on APHA (1999) methods.
According to the studied parameters, the water quality of the river is classified based on the national  and international  water quality criteria. The results obtained were statistically analyzed using MS excel (Version 2007) and SPSS (Pearson correlation) package (Version 15).
Results of the present study are presented in the form of descriptive summary in Tables 2 and 3 respectively.
Temperature of an aquatic system is an important factor and also plays a vital role in the solubility of gases and alters the saturation levels of gases. The minimum T level observed during the study was 22.6ºC (January 2009) at location T1 and the maximum T level was 36ºC (May 2008) at location T12, the overall mean level is 27.9ºC at the river Tamirabarani.
pH is considered as an index for measuring the pollution content for acidic and alkaline wastes. It remains as the critical factor for survival of aquatic plants and planktonic organisms . The minimum pH was measured as 6.98 (February 2009) at location T3, maximum was recorded as 8.39 (January 2008) at location T1 and the mean pH level recorded was 7.77.
Conductivity mostly depends on the nature of various dissolved ionized substances of an aquatic system . Electrical conductivity of the river was observed between 33.47 μS/cm (January 2009) at location T1 and 535.36 μS/cm (March 2008) at location T12, and the mean EC is 171.46 μS/cm. The pH and EC values of all months and at all sampling locations are compatible with the standard levels prescribed by CPCB and WHO.
DO is one of the most valuable indicators in the determination of water quality of a river health; most of the physical, chemical, and biological activities are directly related to the DO content in natural and wastewater .
The observed minimum DO level was 2.8 mg/l at location T10 during the month of April in 2008 and the maximum level recorded as 10.47 mg/l in the month of August 2008 at location T11. The overall mean DO level was 6.7 mg/l. Higher DO level at location T11 was due to higher photosynthetic activity at upstream sides of the check-dam and high turbulence activity within the dam premises due to high wind flow. Observation of lowest level of DO may be due to the direct discharge of organic rich sewage from urban discharges at Tirunelveli and Palayamkottai. Similar observation was found by Mohanraj et al. As DO drops below 4 or 5 mg/L, it may be lethal to the life forms. A minimum of about 2.0 mg/L of dissolved oxygen is required to maintain higher life forms.
The observed level of TDY was within the range of 0.13 -16.4 (nephelometric turbidity units) NTU at location T1 in March 2009 and at location T6 in November 2008 respectively. The overall mean TDY level was 3.31 NTU. Turbidity levels during the months of September October and November exceeded the standard value at downstream areas after location T6; due to the higher runoff from the agricultural, suburban and urban areas during the northeast monsoon period.
Ammoniacal nitrogen in samples was observed in the range of 0-0.28 mg/l during the study, higher level was recorded at location T8 during the month of July 2008 whereas absence of a content record at upstream areas especially during the northeast monsoon periods. Nitrite content of the river water was recorded between 0 - 0.03 mg/l during the period of study, the overall mean NO2 is 0.02 mg/l. highest level was recorded at location T10 during March month of the year 2008. Nitrate is the end product of aerobic decomposition of organic matter and is the most oxidized form of nitrogen commonly present in natural waters [18-19]. Nitrate level of the samples were recorded in the range of 0.013-1.18 mg/l at locations T11 and T7, T9 respectively during the months of February and October 2008, and the overall mean NO3 level is 0.45 mg/l. Phosphate is an essential plant nutrient and play as an important limiting factor and responsible for the growth of phyto-planktons in aquatic systems [20,21]. Phosphate level of the samples ranged between 0 (June 2008, at location T4) and 4.65 mg/l (November 2008 and January 2009, at location T12), and the overall mean PO4 content is 1.2 mg/l. Presence of ammonia and other nitrogenous sources may result in eutrophication and anoxic conditions . Nutrient content of the river water during the study was well within the standard levels prescribed by CPCB and WHO whereas phosphate values in many stretches exceeded the standard limit of (0.1 mg/l) US Public Health Standards . Higher agricultural practices, natural leeching of ore rocks along with higher human disturbances enrich the PO4 content .
The COD is a measure of oxygen equivalent to the organic matter content of the water susceptible to oxidation by a strong chemical oxidant and thus is an index of organic pollution in the aquatic ecosystems . The COD level of the samples was recorded between 2 and 17 mg/l (location T9), and the overall mean COD level is 7.36 mg/l. During summer the COD content of the entire river stretch exceeded the standard level (10 mg/l), and mainly downstream areas after location T2 showed exceeded levels during various months of the study. BOD is an approximate measure of the amount of biochemically degradable organic matter present in the water and it is used mainly to determine degree of pollution in water bodies and their self-purification capacity, pollution stress of wastewaters, and efficiency of waste treatment plants [18-19]. The BOD level of the samples varied between 0.2 (T7) - 10.2 (T10) mg/l during the months of April and June 2008, and the overall mean BOD level is 2.6 mg/l. Unpolluted stretches like T1 and T4 had the BOD content of less than 5 mg/l; similar results were found by Schulze et al..
Calcium and magnesium content of the river water was observed between 2-43.29 mg/l and 0.012-2.87 mg/l respectively, and the overall mean Ca and Mg levels are 14.79 and 0.59 mg/l during the study. Lowest sodium content was recorded as 1 mg/l at location T1 (August 2008), higher level recorded as 79.3 mg/l at location T12 (March 2008), and the overall mean Na is 20.28 mg/l. Potassium level of the water ranged between 0.2-6.3 mg/l at locations T1 (January 2008) and T12 (September 2008) respectively, and the overall mean K level is 1.71 mg/l.
Bacteriological assessment of the river water reveals that the TC content of the river were within 2-3500 MPN count/100 ml, and the overall mean TC level is 207.75 MPN count / 100 ml during the study. The FC content of the samples was recorded between 2-2800 MPN count / 100 ml, with the overall mean FC level of 58.87 MPN count / 100 ml. Higher coliform content of the river is mainly due to the higher human disturbances along the river and bank areas like huge gathering during festive occasions, open defecation, direct discharge of domestic and sewage wastes, discharges from farmhouses and runoff from urban and rural areas. Previous study carried out by Murugesan et al. [8,11,12] also observed similar results.
Correlation matrix observed among the physicochemical variables is given in Table 4. Positively strong correlation was observed between most of the variables and significant negative correlation is recorded between pH and total suspended solids (R2=-0.224); conductivity and dissolved oxygen (R2=-0.442); dissolved oxygen and biological oxygen demand (R2=-0.506), total hardness (R2=-0.379), calcium (R2=- 0.433), magnesium (R2=-0.236) and sodium (R2=-0.406 at the level of p<0.01.
Total hardness showing significant positive correlation with the presence of Ca, Mg and Na, similar report was provided by Mohanraj et al. .
The negative correlation between DO and NH4-N (R2=- 0.184) and NO2 (R2=- 0.189) revealed that enrichment of nutrients lead to the eutrophication in the river system and inversely affects the dissolved oxygen content of water. Bacteriological study also showed significant positive relationship between NO3, PO4 and COD.
Parameters such as Ca+, Mg+, K+, Na+, SO4,TH, pH, EC appeared to have gain more concentration at downstream probably from the riparian land use comprising mainly agricultural lands. Hence, purification efforts along the river flow can be directed to the control of these parameters due to the enrichment of organic compounds all along the river flow.
Water quality assessment of the Tamirabarani river basin area revealed potential contamination from various anthropogenic activities and results of the study shows that water quality parameters vary in both relative and absolute terms. Physicochemical characters changes according to the flow pattern and seasonality. During the northeast monsoon period most of the physicochemical characters showed significant variation in concentration due to higher water discharge level. Dilution plays a vital role during monsoon periods which reduce the concentration of pollutants, which also increase the load during earlier periods through runoff from bank and neighbouring areas.
Organic enrichment and higher bacteriological content of the river system determines the quality of the river water. During the study the quality of the river was observed between classes “A” and “E” correspondingly for various uses like (A) drinking water source without conventional treatment but after disinfection; (B) outdoor bathing; (C) drinking water source with conventional treatment followed by disinfection; (D) propagation of wildlife, fisheries and (E) irrigation, industrial cooling controlled waste disposal due to higher bacterial population and BOD content. In conclusion, water quality of the upstream areas of the river Tamirabarani was worsening mainly because of higher bacteriological population and COD levels whereas downstream areas worsening mainly due to high BOD, COD, TC and FC content when compared with the quality criteria of CPCB and WHO.