STUDIES OF HINDON RIVER SYSTEM WITH SPECIAL REFERENCE TO HEAVY METALS

Abstract

Urban settlements and growing industrial development, combined with rapidly increasing demand for water, are causing more and more water management problems. More than ninety percent of water pollution problems in India are due to indiscriminate discharge of municipal wastes. These wastes being biodegradable produce a series of directional but predictable changes in water bodies. Industrial effluents are responsible for pollution to a lesser extent but the effects produced by them may be more serious as nature is often unable to assimilate them. Agriculture is also responsible for degrading the river water quality by generating runoff from animal husbandry units, which contain predominantly organic compounds from the use of mineral fertilizers and chemical pesticides. The river Hindon is among one of the important rivers in western Uttar Pradesh (India).having a basin area of about 7000 km2, and lies between latitude 28° 30' to 30° 15'Nand longitude 77° 20' to 77° 50' E. The river originates from Upper Shivaliks (Lower Himalayas) and flows through four major districts, viz., Saharanpur, Muzaffarnagar, Meerut and Ghaziabad in western Uttar Pradesh. The climate of the region is moderate subtropical monsoon type. The average annual rainfall in the basin is about 1000 mm, major part of this is received during monsoon period. The major landuse in the basin is agriculture and there is no effective forest cover. The main sources, which create pollution in river Hindon include municipal wastes of Saharanpur, Muzaffarnagar and Ghaziabad districts and industrial effluents of sugar, pulp and paper, distilleries and other miscellaneous industries through tributaries as well as direct outfalls. On account of these outfalls of municipal and industrial wastes into the rivers, the water is subjected to varying degree of pollution. In view of these observations, detailed study on Hindon river system, covering a distance of 200 km, has been carried out with the following objectives to examine the behaviour of different pollutants in different reaches of river Hindon to provide a proper basis for the management of the basin as a whole. i) Characterization of waste effluents polluting river Hindon and their impact on river water quality, ii) To establish mass balance of water quality constituents to differentiate between point and non-point sources of pollution, iii) Metal pollution assessment through aquatic sediments, iv) Adsorption characteristics of bed sediments to demonstrate the role of coarser fraction of the sediments in controlling metal pollution and to determine mechanistic parameters associated with the adsorption process. In order to achieve the objectives of the study, 8 sampling stations in the waste effluents and 13 sampling stations in the river water were selected for water quality monitoring for a period of two years (April 1997 to February 1999) on alternate months. The main effluent discharge in the upper part of the river system is from Star Paper Mill. The partially treated effluent is usually brownish and has pungent or irritating smell with high BOD values. The effluent from the Cooperative distillery has very high BOD and COD values indicating very high pollution potential of the distillery effluent. The wastewater of Dhamola nala contains large amount of solids, moderate BOD and COD. In the mid portion of the basin, river Kali and river Krishni join the Hindon river. The discharge of both the rivers into the river Hindon is hazardous due to the high values of BOD, COD and other constituents. From the study conducted, it is found that the water of the river is subjected to varying degree of pollution, caused by numerous untreated waste outfalls of municipal and industrial effluents. The quality of river water at the upstream site is quite satisfactory, the dissolved oxygen content being 7-9 mg/L. However the quality of the river deteriorates sharply due to mixing of wastewater and effluent from Nagdev nala, Star Paper Mill and Cooperative distillery. The effluent of pulp and paper mill and distillery added high concentration of organic matter to the river, which is responsible for the decrease in dissolved oxygen and increase in BOD, COD and TDS alongwith other factors. The maximum concentration of ammonia was found after the confluence of Dhamola nala, which is carrying the municipal waste of Saharanpur town and has significant flow throughout the year. Further downstream, the quality of river improves due to reaeration and photosynthesis. In the lower stretch, degradation of water quality is observed due to the discharge of wastewater from Budhana drain, Kali river and Krishni river. However, the water quality in this stretch is mainly controlled by the release of water from Upper Ganga Canal through Khatauli and Jani escapes. There is a strong seasonal pattern for various water quality constituents in the river water with elevated concentrations during summer and lower concentrations during monsoon periods. Almost all the constituents follow the same temporal patterns except dissolved oxygen, which shows reverse pattern. The interrelationship between river discharge and hydrochemistry provides a useful means for examining hydrological processes in a river system. In general, the relationships are curvilinear and a decrease in various water quality constituents is observed with increasing discharge. The overall low value of r2 between water quality constituents and in discharge may be attributed to the discharge ofirregular industrial effluents of different kinds, climatic and physiographic controls. The river system is highly influenced due to heavy metals also, which enter the river Hindon by direct discharges of industrial and urban effluents and surface runoff. The status ofpollution of river Hindon with respect to eight heavy metals (Fe, Mn, Cu, Cr, Zn, Ni, Pb, and Cd) has been examined, quality-quantity relationships established and mass balance approach has been used to differentiate between point and non-point sources ofpollution. High concentrations of dissolved Fe, Mn, Cu, Cr, Ni and Pb in the upper portion were observed which may be attributed to the mixing of effluents from Star paper mill and Cooperative distillery. On the otherhand, higher concentrations of particulate metals in the lower portion of the river may be due to the confluence of river Kali and river Krishini, which carry municipal and industrial effluents of Muzaffarnagar region and sugar mill effluent from Shamli. The higher particulate concentrations may also be attributed to sediment transport functions. The particulate component contains highest concentration of iron and manganese as compared to other metals, which are important components for the transport of metal ions. The concentrations of all metals are lowest in winter months and highest during summer months. The concentration of dissolved metals decreased in the monsoon months due to dilution effect of rainfall. Higher percentage of almost all metals in particulate form was observed during post-monsoon months due to suspended load carried by surface runoff during monsoon season. The chemical mass balance approach has been used extensively during recent years to study in-stream reactions and sediment dynamics. Large retention of pollutants, particularly heavy metals, in stream sediments has been reported in a number of studies. In this study we have used a chemical mass balance approach for measuring the changes in the IV concentration and/or load to the river, which develops an interesting concept to discriminate between point and non-point sources of pollution to the river. Mass balance calculations conducted for various water quality constituents in this study indicated that uncharacterized sources contribute about 10-20% load of major cations and anions and 10-30% load of metals (Fe, Mn, Cu, Cr, Zn, Ni, Pb, and Cd) to the river. The approach may be used to estimate the load to the river and detect changes in the water quality characteristics within the river system. It is inferred from the results that additional inputs are needed to account for the observed difference in load along the river. The sources may include non-point sources of pollution due to agricultural activities, remobilization from or entrainment of contaminated bottom sediments, ground water contribution or a combination of these sources. The difference may also be attributed to some small point sources of pollution, which could not be identified during the course of present investigations. An additional advantage of this approach is the substantial reduction in cost involved in the analysis of a large number of individual samples. The sediments existing at the bottom of the water column also play a major role in pollution studies due to their specific adsorption capacity. They reflect the quality of the water system and can be used to detect the presence of contaminants that do not remain soluble after discharge into surface waters. Therefore, the analysis of heavy metals in sediments and their adsorption behaviour permits us to detect pollution that could escape water analysis, and also provide information about the critical sites of the water system under consideration. The sediment of river Hindon consists of rather coarse texture, composed of more than 90% sand and <10% silt and clay in the upper portion of the river. However, the content of clay and silt (0-75 urn) increases in the down stream section of the river. Most of the sediment transported and deposited by the river consists of fine to medium grained sand. The organic content of the sediment was found to be of the order of 0-1%. Keeping in view the importance of particle size and composition of sediments in metal pollution assessment, the concentrations of various metals (Fe, Mn, Cu, Cr, Ni, Zn, Pb, Cd) were determined in 0-210 |im sediment fraction of the river Hindon. In general, the metal concentrations are higher during summer months compared to that of winter months. Similar trend was observed in the case of water also. The variability in metal concentrations during different months was also lower at all the sites as against the metal concentrations in the associated water column, which is highly influenced due to variability in flow conditions. High correlation coefficients (>0.9) observed between Ni-Cr and Ni-Zn indicates common source, their mutual dependence and identical behaviour during transport. In sediments of polluted streams, the largest amounts of heavy metals are associated with organic matter, the fine grained sediment fraction and Fe/Mn hydrous oxides, or are precipitated as hydroxides, sulphites or carbonates. Metal concentrations in the bed sediments of river Hindon are positively correlated with organic mattercontent, although the correlation is not very strong. The mobility of metal ions is dependent upon their sorption by sediments and their redistribution with deposition at the sediment-water interface. The mobility of metals is also regulated by the chemically mobile fraction of the sediments. In the present study iron and aluminium have been chosen as conservative elements for the analysis because of their relative abundance in the earth's crust and thus their decreased tendency to be greatly influenced by human activities. The general trend of relative mobility is observed to be Fe>Mn>Zn>Cr>Ni>Pb>Cu>Cd in both the cases. .The ratio of heavy metals to conservative elements (Fe, Al, Si, etc.) may reveal the geochemical imbalances due to the elevated metal VI concentrations normally attributed to anthropogenic sources. The metal pair ratio has been used to assess the most polluted site of the river. Adsorption is one another important phenomena in water quality control, which may determine the fate and transport of pollutants in the aquatic environment. Heavy metals today have a great significance due to their toxicity and adsorption behaviour. The determination of the concentration levels of heavy metals in natural waters, as well as the elucidation of the chemical forms in which they appear, is a prime target in environmental research today, because of the close relation between toxicity and speciation. Various studies describing effect of operating variables, kinetics and thermodynamics of adsorption processes on low cost waste products have been documented in the literature. However, little attempt has been made to study kinetics of adsorption process on riverbed sediments in their natural state of occurrence. In the present study adsorption of lead, cadmium, zinc and chromium has been studied on the bed sediments of river Hindon. The effect of various operating variables, viz., solution pH, sediment dose, contact time, and particle size, have been studied on the adsorption of lead, cadmium, zinc and chromium ions. The optimum contact time needed to reach equilibrium was found to be of the order of 60 minutes and is independent of initial concentration of metal ions. The adsorption curves are smooth and continuous leading to saturation, suggesting the possible monolayer coverage of metal ions on the surface of the adsorbent. The extent of adsorption increases with an increase of pH. Furthermore, the adsorption of metal ions increases with increasing adsorbent doses and decreases with adsorbent particle size. The important geochemical phases, iron and manganese oxide, act as the active support material for the adsorption of metal ions. The adsorption data has been analysed with the help of Langmuir and Freundlich adsorption models to determine the mechanistic parameters VII associated with the adsorption process. An attempt has also been made to obtain thermodynamic parameters of the process, viz., free energy change, enthalpy change and entropy change. The negative values of free energy change (AG0) indicated spontaneous nature of the adsorption for these metals and positive values of enthalpy change (AH0) suggest the endothermic nature of the adsorption process. The uptake of metals is controlled by both bulk as well as intraparticle diffusion mechanisms. This study has helped in a better understanding of the fate of pollutants in Hindon river system. The findings of the study will be useful in better management of the river basin.