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International Journal of Water Research Universal Research Publications. All rights reserved
Original Article Raw Water Quality Change and Cost Implication; A Case Study of Dalun Headwork’s Christian Larbi Ayisi1, Bernard Quarshie2*, Samuel Jerry Cobbina3 Key Laboratory of Freshwater Fishery Germplasm Resources, Ministry of Agriculture, Shanghai Ocean University, 999 Hucheng Huan Road, Shanghai 201306, P.R China 2 Cocoa Research Institute of Ghana, Agronomy Division, P.O. Box AN 8, New Tafo- Akim, Eastern Region, Ghana. 3 University for Deveopment Studies, Faculty of Renewable Natural Resources, P.O Box Tl 1883, Tamale Ghana. *Corresponding author. E-mail:email@example.com
Received 22 December 2013; accepted 31 December 2013 Abstract Studies were carried out to examine the trend in raw water quality changes of the White Volta used by Dalun Headwork’s, which provides daily water supplies to the Tamale Metropolis and its environs in the Northern Region of Ghana over a six month period (November – April, 2010), and the implications these changes have on chemical cost of treatment. Eight parameters (pH, conductivity, turbidity, colour, chloride content, temperature, total hardness and alkalinity) of water quality were considered in the study. The study was conducted at the Dalun Headwork’s. The results showed that turbidity and colour had the most significant influence on chemical cost of water treatment. The turbidity ranged from 88.20 NTU to 158.00 NTU with a mean of 120.40 NTU and the colour ranged from 80.00 Hz to 123.00 Hz. It was shown that the cost of treatment increases significantly with increase in these two parameters. The turbidity and colour recorded a treatment cost of GH¢/l 3.85 × 10-5 and GH¢/l 1.2 × 10-4 for alum dose and chlorine gas dose respectively in the month of rains. It was also found out that the White Volta does not undergo drastic pH changes. Turbidity and colour showed an increasing trend which indicates that the river receives increasing organic load in the rainy season and a decreasing organic load in the dry season. © 2013 Universal Research Publications. All rights reserved Key words:- raw water; cost implication; quality
Introduction There has been recorded decreasing trend in the amount of water available per person due mainly to population increase, demand for agriculture, industry and domestic purposes. This current situation makes the improvement of water usage a central concern for all. Water is essential to all forms of life on earth, from the simplest of living organisms to the most complex of human systems. Lack of fresh water to drink, for use in industry, agriculture and for the multitude of other purposes where water is essential is a limiting factor hindering development in many parts of the globe (11). The use of water is restricted by the quantity and quality available and these aspects of water are affected by different forms of pollution being it chemical, biological or physical. Therefore in order to ensure the availability of sufficient quantity of quality water, it becomes almost imperative in modern society to plan and build suitable water supply schemes which may provide potable water for various sections in accordance with their demands and requirements (5).
Good quality water available in the required quantities promotes hygiene and public health, hence societal development. This places the need for water treatment from natural sources to meet the required quality standards before consumption to avert any possible health and environmental problems that may arise. In view of this, efforts have been made all over the world with respect to provision of physical infrastructure such as treatments plants as well as reservation of entire watershed to collect and maintain good quality water for treatment. The Dalun Headworks in the northern region is one such body to serve the purpose of reserving water for treatment and consequent consumption by the people in the Tamale metropolis and its environs. However, the cost at which the treated water is made available is very critical especially in developing countries like Ghana battling with abject poverty. According to (5), water (per capital demand) consumption is affected by quality of water supplies and the cost of water. If water rates are high, lesser quantity may be consumed by people and this may compel the people to use raw surface water which will result in the incidence of water related diseases.
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Stringent measures should therefore be put in place to minimize cost of production to create positive impact on the grassroots of Ghanaians and these calls for collaborative approach from all stakeholders in the use of fresh water resources. The pollution of our water bodies has always been intractable problem throughout Ghana and these same water sources are used by our water companies. Thousands of Ghana Cedis are spent by the government to treat polluted water bodies and make them available for domestic, industrial and agricultural consumption. The increase in population contributes to human settlement close to water bodies where the activities of humans lead to pollution of the water bodies and this deduces the fact that water quality of a particular water source is not stable but changes from time to time. The Dalun Headworks derive its source of water from the White Volta in Nawuni in the TolonKumbungu of Ghana and treat it for supply but farming activities and sand winning at the White Volta affects the water quality and resources through pollution (3). Untreated water when consumed can cause health related problems such as cholera, typhoid among others to nearby communities and towns to which supplies are made, hence the need for water treatment to be looked critically The objective of this research is therefore to assess the impact of raw water quality on the cost of treatment in Dalun Headworks in the Northern Region of Ghana. Materials and methods Data Collection The study area was Dalun headworks in the Tolon Kumbungu district of the Northern Region of Ghana. The methods employed for this present work were desk study and laboratory analysis. The desk study was the collection of secondary data at Dalun Headworks. Monthly accumulated data on raw water quality and corresponding quantity and cost of treatment for the study period were taken. Personal communication with some officials of Dalun Headworks and Ghana Water Company Limited in Tamale was required for directives and relevant information on interpretation of some of the data. Samples of the White Volta in Nawuni were taken using sterile polyethylene bottles for laboratory analysis. The pH, temperature, alkalinity, turbidity, colour and other selected water parameters were determined with respective methods and equipments. The chemical cost of treatment was deduced using jar test method. Procedure for Jar Test Method Six beakers (1000ml each) were rinsed with distilled water and the water sample was shaken very well. The six beakers were rinsed with some of the water sample and each beaker was filled with water sample. One percent (1%) aluminium sulphate was poured into a 200ml beaker and was pipette in different proportions into each beaker. A flocculator was used to stir the solution (water sample + aluminium sulphate) for 10 minutes at 125 revolutions (speed) per minute and the speed was reduced to allow the dirt in water sample in each beaker to settle. The settled dirt indicated the sufficiency or insufficiency of the aluminium
sulphate. The pH and turbidity of the water sample in the each beaker were deduced with pH meter (Lovibond 2000) and Turbidimeter (LaMotte 2020) respectively. Calculated amount of hydrated lime was added to each water sample to adjust the pH and a beaker (water sample) with settled values of pH and turbidity demanding less chemical for treatment was selected. The selected beaker (sample water) was tested for the presence of bacteria and other harmful organisms and used to calculate the chemical cost of quantity of water produced. Determination Water Quality Parameters The following laboratory equipments and methods were used in determining some of the selected water quality parameters. pH-pH meter (Lovibond2000); TurbidityTurbidimeter (LaMotte 2020); Conductivity and Temperature-Conductivity meter (2100 P); Alkalinity-Titration method; Colour -Lovibond Nessleriser (2250) Statistical analysis The monthly values of the water quality parameters and their respective cost of treatment were analysed using Statistical Package for Service Solution (SPSS) Version 16, Microsoft Excel and the results presented on graphs to deduce the trend of water quality changes. Results The results of the variation trends in water quality of the White Volta are presented (Fig. 1 to 4). Our results of this present study show that pH increased from 6.40 in November to 7.36 in March (Fig 1). It then decreased to the lowest value of 6.55 in April. Conductivity exhibited a gradual decreasing trend from 79.6 uS/cm in November to 70.5 uS/cm in March. It then increased to 86.2 uS/cm in April. The turbidity registered a gradual decreased from 140 NTU in November to 88.2 NTU in March and then increased highly to 158 NTU in April (Fig 1).
FIGURE 1: Monthly variations in conductivity (uS/cm) and pH Chloride concentration decreased slightly from 8 mg/l in November to 5 mg/l in February. It increased from 6 mg/l in March to 9 mg/l in April. Total alkalinity decreased from 42 mg/l in November to 28 mg/l in February. It then increased slightly from 28.5 mg/l in March to 35 mg/l in April (Fig 2). Temperature increased from 29℃in November to 30.3℃ in January. It then decreased to 29.8℃in February, increased to 30.1℃and decreased slightly to 29.1℃ in April.
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FIGURE 2: Monthly variations in turbidity (NTU) and colour (Hz) Conductivity exhibited a gradual decreasing trend from 79.6 uS/cm in November to 70.5 uS/cm in March. It then increased to 86.2 uS/cm in April (Fig 3).
FIGURE 3: Monthly variations in alkalinity (mg/l) and chloride (mg/l) The total hardness increased from 21 mg/l in November to 30 mg/l in March and then decreased to 19 mg/l in April. Apparent colour registered a regular decrease -increase trend over the period. From 112.7 Hz in November, it decreased to 80 Hz in March and then increased to 123 Hz in April (Fig 4).
FIGURE 4: Monthly variations of temperature ( total hardness (mg/l)
The results of cost implication of raw water changes of the White Volta presented in the Table 1.Turbidity and colour shown to have very significant influence on treatment cost; and the treatment cost was generally found to be high in the month of heavy rains. The increase in treatment cost
corresponds to increased turbidity and colour. However, minor variations were observed. As illustrated in the table 1, treatment cost of raw water was lowest in March and highest in April. The hydrated lime, chlorine gas and alum were used for the treatment of turbidity and colour, pH adjustment and disinfection of the water respectively. Turbidity recorded the highest value of 158.00 NTU in April and the least was 88.20 NTU in March. Colour was highest in April (123.00 Hz) and least in March (80.00 Hz). The pH of raw water during the study ranged from 6.55 to 7.36. Discussion Some physico-chemical aspects of the limnology of the river were considered. These aspects have great influence on life forms in the aquatic environment as well as the quality of supplied water for domestic and industrial use. According (8), the pH of most raw water sources lies within the range of 6.5 â€“ 8.5. The lowest monthly pH value recorded during our study period was 6.55 in April and the highest recording being 7.36 in March and lies within the permissible range for most public water supplies (5). The difference indicates that the river does not undergo drastic changes in pH. This supports the findings of (7) who found the difference between the highest and lowest pH recordings to be 1.3. The main contributors of alkalinity to surface waters are carbonates, bicarbonates and hydroxides (1). Alkalinity of the river decreased from 42 mg/l in November to 28mg/l in February. It however increased from 28.8mg/l in March to 35 mg/l in April. The decrease could be due to the decrease in all ochthonous inputs of salts which contribute to alkalinity. These inputs may have however increased significantly in November. The implications of the relative stability of raw water pH of the White Volta possibly will be that any changes in the nutrient levels, soluble gases, and their related effects on water quality are not directly due to the river pH. Turbidity increased to 158 NTU in April. The only deviation during the period was in November to March when it decreased from 140 NTU to 88.2 NTU. The increased turbidity can be attributed to the increased nonpoint sources occurring naturally which include landderived sand, silt, clay, and organic particles dislodged by rainfall in April and carried by overhead flow (1). Organic particles via runoffs can be a major cause which may lead to increased sediment loads. Colour in water results from the presence of natural metallic ions especially iron and manganese, and humic substances originating from organic matter which contributes to turbidity. Colour decreased from 140 HZ in November to 80 HZ in March. The highest recording was made in April. It however decreased and increased sporadically. (6) reported that, colour of surfacewaters generally increases with increasing pH. This assertion could not be clearly visualised in this study. The only reason could be due to the stable nature of the raw water pH. The increase in colour during the rains in April is a natural consequence of the influx of surface runoff from the watershed along with the sediments and colloidal material. The main sources of chlorine in the river can be attributed to agricultural and domestic wastewaters which are brought in by the tributaries of the impounded
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Table 1: Monthly variations in treatment cost of raw water PARAMETER TURBIDITY COLOUR MONTHS pH (NTU) (Hz) NOV 140.00 84.5 7.1 DEC 123.00 93.0 6.58 JAN 114.00 84.5 7.1 FEB 99.2 82.0 7.21 MAR 88.2 80.0 7.36 APR 158.0 123.0 6.55 river and runoff during heavy precipitations. Chlorine content decreased from 8 mg/l in November to 5 mg/l in February. It then increased to 9 mg/l in April. The increase can be due to increased agricultural waste inputs as well as domestic sewage which find their way into the river (Hanson pers. comm.). It can be categorically stated that the river is receiving increased amounts of domestic and agricultural wastes. However, the levels are within the WHO acceptable limits for public water supplies (10). The Conductivity ranged from a minimum of 70.00 μS/cm in January to a maximum of 86.20μS/cm in April. The high conductivity recorded in April could be the discharges of domestic effluent and surface run-off from the cultivated fields which might have increased the concentration of ions. Almost all the conductivity values fell outside the “no effect” range of 0-70 μS/cm for drinking water use (WRC, 2003). The total hardness values ranged from a minimum of 19.00 mg/l in April to a maximum of 30.00 mg/l in March. The high value recorded could be due to the dry season where temperatures are high since the solubility of salts is a function of temperature. It could also due to the in increased anthropogenic activities. Looking at the WRC (2003), the river can be described as being soft to moderately soft since all the values fell within the range of 0 – 100 mg/l. The temperature (˚C) ranged from a minimum of 29.00 ˚C in February to a maximum of 30.30 ˚C in January. The higher temperature recorded could be attributed to the dry season. The temperature variations for the months could also due to the different time for the water sample collection. The major treatment processes that involve chemical consumption are sedimentation aided by coagulation/flocculation and the disinfection processes. The major chemical used at the Dalun Headworks for this process is alum (aluminium sulphate). The major raw water parameters impacting on the coagulation and flocculation process are pH, turbidity and colour (4). The influence of pH on coagulation have to do with the formation of aluminium hydroxide (floc) which attracts other fine and suspended particles, thus settling down at the bottom. (4), continued that the pH at which this process can effectively proceed ranges from 6.5 to 8.5. This means that as far as pH is concerned, the raw water from the river is not posing any significant impact on coagulation cost at the Dalun Headworks. The pH values for raw water within the study period ranged from 6.55 to 7.36. Thus the pH of the water allows coagulation process to proceed under normal conditions. Colour and turbidity have been established to be the parameters having significant influence on treatment cost (Table 2). This can be attributed
ALUM 3.5 X 10-5 3.15 X 10-5 2.8 X 10-5 2.45 X 10-5 2.1 X 10-5 3.85 X 10-5
CHEMICAL COST (GH¢/l) HYDRATED CHLORINE LIME GAS/HYPO 3.0 X 10-5 1.1 X 10-4 -5 2.7 X 10 1.0 X 10-4 -5 2.4 X 10 8.9 X 10-5 -5 2.1 X 10 7.8 X 10-5 -5 1.8 X 10 6.7 X 10-5 -5 3.3 X 10 1.2 X 10-4
to the fact that all suspended and dissolved solids 45 and impurities culminate in the occurrence of these two parameters; and these parameters are known to necessitate coagulation (4; 6). Turbidity increased from 88.2 NTU to 158.0 NTU with a mean of 120.4 NTU. Thus decline in water quality with respect to turbidity increased the cost of treatment from 2.1 × 10-5 GH¢ in March to 3.85 × 10-5 GH¢/l in April (Table 1). This was due to the high dose of alum used for turbidity treatment in April compared to low dose of alum in March. April recorded the highest treatment cost as a result of heavy rainfall which the river more turbid. Another chemical used as a coagulant at the water works was hydrated lime. This is usually used in conventional treatments for upward adjustment of pH after high alum doses have resulted in reduction of the pH (6). However, it is used as coagulant when applied in excess doses (4). Disinfection The chemicals used for disinfection at the Head works were calcium hypochlorite (5% pure), bleaching powder (35% pure) and chlorine gas (100% pure). The most frequently used chemical was the chlorine gas. This was due to its ability to provide residual disinfecting effects for long periods. This affords complete protection against future recontamination of water in the distribution system. Disinfection accounts for part of the total treatment cost. The break point chlorination is employed. Again pH, though very critical in the effectiveness and efficiency of the chlorination process, does not pose any significant influence. This is because the hypochlorous acid which is the most destructive (about 80 times more effective than hypochlorite ions, also formed) in the killing of bacteria and other microscopic organisms present in the filtered water is most stable in pH ranges slightly below 7 (4). The amount of chlorine required thus, depends mostly on organic and inorganic impurities present in it. This is because increase in these impurities increases the chlorine demand of the filtered water (2). (4), reported that the chlorine dose must generally be increased during rainy season and epidemics. The findings of this study corroborate this statement. Careful examination of the monthly treatment cost depicts a trend where the cost was generally higher in April which experienced heavy rains compared to the other months. This was the month where the highest recording in turbidity and colour were recorded. The highest treatment cost of 1.2 × 10-4 GH¢/l (Table 1) was recorded in April which corresponded to the highest colour reading of 123 HZ and a high turbidity of 158.0 NTU. The necessity to increase chlorine dose in the month of rains may be due to the possible increase in pathogenic organisms in the raw water as a result of high colloidal and
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suspended particles which serve as substrates for the microorganism. The treatment process does not include softening; hence the addition of coagulants and other chemicals increases the water hardness further. However, it falls within the WHO acceptable range of not more than 500 mg/l. Conclusion This study has shown that there is a significant correlation existing between raw water quality and the chemical cost of treating raw water at the Dalun Headworks, and that the cost is mainly incurred during the coagulation and disinfection processes. Two raw water parameters; turbidity and colour have been shown to influence the quantity of chemicals required in the treatment of water the most. Generally, water quality of the White Volta is declining with respect to turbidity and colour and with population on the rise in the catchmentâ€™s communities; water quality will deteriorate further with cost of treatment increasing the more, unless pragmatic steps are taken in educating inhabitants to reduce the levels of pollution. We therefore recommend that high budget allocation should be made for chemicals used for the treatment of raw water during the rainy season. Also the study should be conducted from the onset of the rains to the dry season to give clear variation of treatment cost of the two seasons. References 1. APHA/AWWA/WEF (1995). Standard Methods for the examination of water and wastewater. Nineteenth ed. 1294pp
Birdie G. S. and Birdie, J. S. (2002). Water Supply and Sanitary Engineering. Including Environmental and Pollution Control Actions. Khanna Publishers. 1450pp 3. Documented report, (2010). Ghana Water Company Limited Regional Head Office Tamale. 4. Garg S. K. and Garg, R. (2002). Water Supply Engineering. Thirteenth Rev. Ed. Pub. Khanna Publishers. 1256pp 5. Garg, S. K. (1996). Water Supply Engineering. Nineteenth Ed. Khanna Publishers. 996pp 6. Koram, Kwadwo A. (2001). Raw Water Quality and Water treatment at the Weija Water Works. Project Report, Institute of Renewable Natural Resource, KNUST, Kumasi. 36pp 7. Ofori, J. K. (1980). A Hydrological Study (changes) of the Barekese Lake, Kumasi-Ghana. A Thesis Report, Biological Science Department KNUST, Kumasi. 35pp. 8. Webber, W. S. and Stumm, W. (1963). Mechanism of Hydrogen ion buffering in Natural Waters. Journal of American Water Works Association 55, p1553. 9. World Health Organisation (1990). Handbook on Water Treatment. Kemira Kemi AB. Water Treatment.p95 10. World Health Organisation/United Nations Education for Scientific and Cultural Organisation report (1991). Water Resources Assessment, Progress in the implementation of the Mar del Plata Action Plan and a Strategy for the 1990s p5.
Source of support: Nil; Conflict of interest: None declared
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