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Asian Journal of Biochemical and Pharmaceutical Research Issue 3(Vol. 6) 2016 ISSN: 2231-2560 CODEN (USA): AJBPAD Research Article Asian Journal of Biochemical and Pharmaceutical Research Turbidity Removal of Water-Challenging Criteria K. S. Beenakumari Department of Chemistry, All Saints College, Kerala University, Thiruvananthapuram, India Received: 08 July 2016; Revised: 14 July 2016; Accepted: 16 July 2016 Abstract: Surface water contains different kind of suspended materials which cause turbidity and colour. In drinking water, the higher the turbidity level, the higher the risk for the people to develop gastrointestinal diseases. This is especially problematic for immune- compromised people, because contaminants like bacteria can become attached to the suspended solids. Coagulation and flocculation using alum and lime are the physical and chemical processes in which small particles causing turbidity and colour change into giant particles and finally eliminated. It is very important to ensure that coagulation is optimized to prevent excessive amount of chemicals remaining in the drinking water. It is not easy to calculate the amount of chemicals required to maintain the turbidity in the standard level by simply conducting jar test in different environmental conditions like rainy falls, since the turbidity of raw water will change within seconds in the river during these times. This study determines the exact quantity of alum and lime required to maintain the quality of water at varied turbid and pH levels. This ratio will help to add lime and alum only by measuring the turbidity and pH of the raw water without conducting the jar text experiments. This ratio of lime and alum to maintain the water quality is very useful for persons working in water treatment plants. Keywords: Water quality, Turbidity, Jar test, Lime-Alum ratio INTRODUCTION: Surface water contains different kind of suspended materials which cause turbidity and colour [1,2]. One of the physical characteristics of potable water that should meet the drinking water standard is turbidity. The usual source of turbidity is clay particles resulting from the erosion of soil in the catchment area [1]. The size of the colloidal particles which causes turbidity may range from 0.001 microns to 10 microns. The time to settle down these particles in surface waters range from half an hour to 63 years [3]. Turbidity in open water may causes by growth of phytoplankton. Human activities like civil constructions and land altering can lead to high sediment levels in water. Natural calamities like storm rain etc. will also create turbidity conditions. Urbanized areas contribute large amounts of turbidity to nearby waters, through storm water pollution from paved surfaces bridges and parking lots. Certain industries such as quarrying, mining and coal recovery can generate very high level of turbidity in water. In drinking water, the higher the turbidity level, the higher the risk for the people to develop gastrointestinal diseases. This is especially problematic for immune compromised people, because contaminants like bacteria can become attached to the suspended solids. The suspended solids interfere 10 Asian Journal of Biochemical and Pharmaceutical Research Issue 3(Vol. 6) 2016 ISSN: 2231-2560 CODEN (USA): AJBPAD with water disinfection with chlorine as this particle acts as shields for bacteria against the chlorine and also protect bacteria from UV sterilization of water. Coagulation and flocculation are the physical and chemical processes in which small particles causing turbidity and colour change into giant particles and finally their elimination will be preferred by different physical methods such as sedimentation and filtration [1]. Coagulants were used many years ago and Egyptians used alum in 2000 year B. C. [1,4] onwards. The colloidal particles in the surface water carry same electrical charges and hence they cannot get together and form heavier particle for settlement [3]. The coagulants unstabilize this stable system, so that they will get enough close to each other to make heavier and bigger particles [3]. There are various techniques for turbidity removal [5]. The best management strategy for both aluminium and iron when used in treatment is to ensure that coagulation is optimized to prevent excessive amount remaining in the drinking water. It is very essential to ensure the quality of chemicals added so that the treated water does not contain unacceptable concentrations of unwanted chemicals. Conducting jar test is the common way to find out the amount of alum and lime at different pH and turbid conditions. It is not easy to calculate the amount of chemicals required for maintain the turbidity in the standard level by simply conducting jar test in different environmental conditions like rainy falls etc. since, the turbidity of raw water will change within seconds in the river during these times. It is hence very important to find out the relation between the amount of chemicals to be added to maintain pH and turbidity of water. The aim of this study was to determine the exact quantity of alum and lime required to maintain the quality of water at varied turbid and pH levels. The addition of optimum quantity of lime and alum in the water not only avoid the over dosage of chemicals usually happens in many practical situations but also reduce the quantity of aluminium in water coming out from the alum. EXPERIMENTAL METHODS: The raw water obtained from the Aruvikkara River during different seasons was selected for this study. The pH of water was monitored using a digital pH meter MK VI of Systronics. The turbidity is measured using Nephalo turbidity meter of Systronics India. All experiments were conducted at room temperature (28oC). AR grade of Hydrazinium sulphate and Hexamethylene teraammine of Qualigens were used to prepare the standard solutions of turbid water. Buffer capsules of pH 4.00, 7.00, and 9.20 are used to prepare standard solution for pH meter standardization. Flocculator of model KEMI was used to conduct the jar test. The volume of turbid water was 500 ml for all jar test experiments. The alum solution was prepared by dissolving 1g of alum having aluminium concentration above 15%, iron below 1.0% and insoluble matter below 0.5% in 1 litre of distilled water Preparation of lime solution was carried out by dissolving 1 g of lime (concentration of Ca(OH)2 above 86.0% and insoluble below 1.0%) in 1 litre distilled water. Jar test experiments were carried out in the following manner. 500 ML of water samples were taken into a beaker. Then note down its pH and turbidity. Add lime stepwise to increase the pH above 8.5, measure the lime required for increasing the pH to 8.5. Then add alum solution step wise to decrease the pH to 7.5. Note the amount of alum required to bring down the pH 7.5. Calculate the lime-alum ratio 11 Asian Journal of Biochemical and Pharmaceutical Research Issue 3(Vol. 6) 2016 ISSN: 2231-2560 CODEN (USA): AJBPAD for the above process by ratio fixation method. Take 500 ML of water samples in different jars and add lime and alum in multiplies of above ratio to each jar in the flocculator. Then rotate the flocculator at an rpm of 100 for 1 minute and at 10 rpm for next 14 minutes. Allowed to stand the water samples for 10 minutes and note down the pH and turbidity of the supernatant solution. The amount of lime and alum for which the turbidity below10 and pH between 6.5 and 8.5 was noted. A table is created for different turbidity levels showing their corresponding alum and lime amount at different pH conditions. RESULTS AND DISCUSSIONS: Jar test experiment is conducted at different pH and turbidity levels. The resulted turbidity and ph are noted. Table 1 shows the relation between the raw water turbidity and amount of alum added per 1000 L of water sample As the turbidity level increases, the amount of alum also increases. This rise in alum is noted up to the turbidity of 100 NTU in raw water. Above the turbidity limit of 100 NTU the consumption of alum was very high. This is because the alum needed to coagulate the colloidal particles is very high above the turbidity level of 100 NTU. The addition of alum not only decreases the turbidity but also decreases the pH value also. Lime is to be added to maintain the pH level for drinking water. From the table it was noted that amount of lime required was 3/4th of amount of alum if the raw water pH is below 6.5. If the raw water pH is in the range of 6.5 to 7.0, the amount of lime required was ½ of the alum used. If the raw water pH was above 7.5, the quantity of lime consumed to maintain the quality of water was found to be 1/4th of alum used. CONCLUSION: The amount of alum and lime required for maintain the quality of drinking water at different turbidity and pH conditions were optimized. The relation between alum and lime during different turbidity and pH conditions were also established. Used jar test experiments the quantity of alum required increases with increase in the turbidity of water. A very sharp increase in consumption of alum was noted to maintain the turbidity of the water to the standard value if the raw water turbidity is above 100 NTU. Irrespective of the turbidity of raw water, the amount of lime required was 3/4th of amount of alum if the raw water pH is below 6.5. If the raw water pH is in the range of 6.5 to 7.0, the amount of lime required was ½ of the alum used and the quantity of lime consumed was 1/4 th of alum if the raw water pH was above 7.5. This ratio will help to add lime and alum only by measuring the turbidity and pH of the raw water without conducting the jar text experiments. By establishing this ratio of lime and alum to maintain the water quality is very useful for persons working in water treatment plants. 12 Asian Journal of Biochemical and Pharmaceutical Research Issue 3(Vol. 6) 2016 ISSN: 2231-2560 CODEN (USA): AJBPAD Table 1: The relation between the raw water turbidity and amount of alum added Raw water Amount of Turbidity (NTU) Alum (g) Amount of lime (g) pH of raw water below 6.5 pH of raw water between 6.5 -7.5 pH of raw water above 7.5 10-20 20 15 10 5 20-30 22 16.5 11 5.5 30-40 24 18 12 6 40-50 26 19.5 13 6.5 50-60 28 21 14 7 60-70 30 22.5 15 7.5 70-80 32 24 16 8 80-90 34 25.5 17 8.5 90-100 36 27 18 9 REFERENCES: 1. 2. 3. 4. 5. G. N. Bidhendi, T. Shahriari and S. Shahriari, J. Water Res. and Protection, 2009, 2, 90-98. R. Menahem and M. Lurie, Water Science and Technology, 1993, 27(11), 1-20 A. H. Mahvi and M. Razavi, American Journal of Applied Sciences, 2005, 2(1), 397-399. A. A. Shahmansuri and A. A. Neshat, Water and Wastewater Journal, 2003, 48, 39-44. C. Y. Yin, Process Biochemistry, 2010, 45(9), 1437-1444 Corresponding Author: K. S. Beenakumari Department of Chemistry, All Saints College, Kerala University, Thiruvananthapuram, India. 13