Water treatment technology cove 405 pptt

Water treatment system

1. CVE 405 – WATER TREATMENT TECHNOLOGY BY Ing. Dr. FRANK OWUSU ADJEI 1

2. Overview of Water in Ghana Ghana water policy (2007) is the policy that defines water Resources Management in Ghana. Under the Ghana Water policy The Ministry of Water Resources, Works and Housing ( MWRWH ) is the lead government institution responsible for water The MWRWH’s main focus is on overall water resources management and drinking water supply, 2

3. Overview of Water in Ghana Other sector ministries deal with sector related water uses such as irrigation under Ministry of Food and Agriculture, fisheries under Ministry of Fisheries, hydro-power under Ministry of Energy and water transport under Ministry of Harbours and Railways. The key agencies of MWRWH carrying out the ministry’s water resources management and drinking water programmes are the Water Resources Commission ( WRC ), Ghana Water Company Limited ( GWCL ) and Community Water and Sanitation Agency ( CWSA ). 3

4. Water Resources Commission ( WRC ) The Water Resources Commission is responsible for the regulation and management of water resources and for the coordination of policies in relation to them, and provides a focal point in fostering coordination and collaboration among the various actors involved in the water resources sector. The responsibilities of the Commission are wide ranging and key responsibilities are set out in Water Resources Commission Act, 1996 (Act 522). 4

5. Ghana Water Company Limited ( GWCL ) The Ghana Water Company Limited ( GWCL ) is responsible for overall planning, managing and implementation of urban water supply. Their roles, responsibilities and mandates are set in the Ghana Water Company Limited ( GWCL ) Act, 1999 (Act 461). 5

6. The Community Water and Sanitation Agency ( CWSA ) The Community Water and Sanitation Agency ( CWSA ) of the MWRWH emerged from the Community Water and Sanitation Division of the Ghana Water and Sewerage Corporation ( GWSC ). CWSA is the lead facilitator of the rural water supply and sanitation sub-sector (rural communities and small towns), and is responsible for external liaison and co-ordination of the National Community Water and Sanitation Programme ( NCWSP ). The key functions of CWSA are set out in the Community Water and Sanitation Agency ( CWSA ) Act, 1998 (Act 564). 6

7. Other Bodies in Water Supply The Ghana Standards Board is responsible for developing and setting quality standards drinking water including certification and other related uses. The role of the Environmental Protection Agency (EPA) covers among others protection of water resources and regulation of activities within catchment areas including setting effluent standards. The functions of EPA are set out in the Environmental Protection Agency (EPA) Act, 1994 (Act 490) 7

8. Other Bodies in Water Supply The Water Resources Information Services ( WRIS ) institutions i.e. the Hydrological Services Department, the Water Research Institute under the Council of Scientific and Industrial Research, and the Ghana Meteorological Agency. The WRIS institutions provide data and other water resources related information and services to support planning and decision making. 8

9. Introduction to Raw Water and Types (Surface and Groundwater) Raw water is natural water found in the environment and has not been treated, nor have any minerals, ions, particles or living organisms been removed. Raw water includes rainwater, ground water, water from infiltration wells, and water from bodies like lakes rivers, and sea. The water on the Earth's surface is called surface water. Examples are water in streams, lakes, and wetlands, as well in oceans. Surface water also includes the solid forms of water which include snow and ice. The water below the surface of the Earth primarily is ground water , but it also includes soil water. 9

10. Raw water treatment System A raw water treatment system is a system made up of several individual technologies that address the facility’s specific raw water treatment needs . An efficient and well-designed raw water treatment system should be able to handle: seasonal variations in turbidity and flow variations in water chemistry needs and required chemical volumes adjustments changes in water quality requirements (such as the quality of feed water required for a new boiler) 10

11. B asic raw water treatment system Basic raw water treatment system typically includes some type of: • chemical feed to help facilitate the flocculation or coagulation of any suspended solids • clarifier to settle out the larger solids • filtration to remove the smaller particles • control panel (depending on the level of automated operation needed) 11

12. Choice of Water Treatment Process Choice of treatment process depends on: Quality of raw water: Required quality of treated water (end use) Economic resources available of Operation and Maintenance Treatment systems Single treatment plant cannot treat all the different types of raw water Water Treatment Plant is very specific to the required quality of water 12

13. Why the need to treat Raw water To protect the consumer's health (bacteriological safe) Make it acceptable by the consumers (aesthetic: sight, taste, odor and color) Economical reasons - for preventing scaling and corrosion in pipe lines & staining cloths during laundering In some cases - need to make-up deficiency in some quality in water: Adding Fluoride to municipal water for protecting child's teeth, Oxygen by aeration 13

14. Pollutants/impurities in Raw Water 14

15. Pollutants and their Associated Problems Suspended and colloidal solids: they can cause unpleasant odors in food and beverage products, foul process equipment, and create energy losses for the plant. • Silica and colloidal silica: they often foul and scale boiler equipment, reduce the efficiency of plant equipment, and cause product contamination. • Iron: coats fixtures, fouls industrial processes, causes foul tastes and odors in products. • Bacteria: can cause sickness and severe digestive issues/health problems as well as coat cooling tower components. • Hardness: coats equipment fixtures, plugs pipes, scales equipment, and causes a buildup of sludge . 15

16. Different Uses of Water Domestic Purposes: cooking, drinking ,bathing , washing Agricultural Purposes: farming, gardening, fisheries Industrial Purposes: manufacturing Recreation: swimming, rafting, boating Hydropower generation 16

17. Factors that affect Water Use Climate conditions : Warm dry regions have higher consumption rates than cooler regions Size of the city . In small cities, it was found that the per capita per day water consumption was small due to the fact that there are only limited uses of water in those cities. Characteristics of the population. Domestic use of water was found to vary widely. This is largely dependent upon the economic status of the consumers, which will differ greatly in various sections of a city. In high- value residential areas of a city the water consumption per capita will be high Religious beliefs: 17

18. Factors that affect Water Use Metering. Communities that are metered usually show a lower and more stable water use pattern. Water quality . Consumer perception of bad water quality can decrease the water usage rate Cost of water . A tendency toward water conservation occur when cost of water is high. Water pressure. Rates of water usage increase with increases in water pressure Water conservation . Public awareness and implementation of water conservation programs by utilities tend to have an impact on the water usage rate 18

19. Factors to consider in selecting source of drinking water Yield versus demand: The yield must be adequate to meet the demant Water quality: The water quality must also be acceptable and treatment methods suited to the community concerned. Technical requirements : The development of the source must be technically feasible, and the operation and maintenance requirements for the source abstraction and supply system must be appropriate to the resources available. Economic considerations: Care must be taken to ensure that funds are available for both the construction and the operation and maintenance of the system over the longer term. 19

20. Factors to consider in selecting source of drinking water Legal and management requirements: Current ownership of the land and the legal requirements of obtaining permission to abstract are also factors to consider when selecting a source. Impacts of development: The use of a particular water source will have impacts on the people who use it, on animals, and on the environment. The impacts on people may be positive or negative, and may be related, amongst other things, to health, economic status or time. 20

21. Water Quantity Estimation The quantity of water required for municipal uses for which the water supply scheme has to be designed requires following data: Water consumption rate (Per Capita Demand in litres per day per head) Population to be served.       Quantity= Per capita demand x Population 21

22. Water Consumption for Various Purposes Types of Consumption Normal Range (lit/capita/day) Average % Domestic Consumption 65-300 160 35 Industrial and Commercial Demand 45-450 135 30 Public Uses including Fire Demand 20-90 45 10 Losses and Waste 45-150 62 25 22

23. Fluctuations in Rate of Demand Average Daily Per Capita Demand               = Quantity Required in 12 Months/ (365 x Population) However if Average Daily Per Capita demand is supplied at all the times, it will not be sufficient to meet the fluctuations. 23

24. Causes of fluctuations Seasonal variation : The demand peaks during summer. Firebreak outs are generally more in summer, increasing demand. So, there is seasonal variation. Daily variation depends on the activity. People draw out more water on Sundays and Festival days, thus increasing demand on these days. Hourly variations are very important as they have a wide range. During active household working hours i.e. from six to ten in the morning and four to eight in the evening, the bulk of the daily requirement is taken. During other hours the requirement is not much. Moreover, if a fire breaks out, a huge quantity of water is required to be supplied during short duration, necessitating the need for a maximum rate of hourly supply. 24

25. Water treatment Requirement So, an adequate quantity of water must be available to meet the peak demand. To meet all the fluctuations, the supply pipes, service reservoirs and distribution pipes must be properly proportioned. The water is supplied by pumping directly and the pumps and distribution system must be designed to meet the peak demand. The effect of monthly variation influences the design of storage reservoirs and the hourly variations influences the design of pumps and service reservoirs. As the population decreases, the fluctuation rate increases 25

26. Demand Parameters Average Water consumption or Design flow: It is the amount of water consumed in a community or city for various purposes. It is generally expressed as the ” Quantity of water per person in one day on the average.” Average Daily Per Capita Demand = Quantity Required in 12 Months/ (365 x Population) 26

27. Demand Parameters Maximum daily demand : It is the maximum amount of water used in one day throughout the year. Maximum daily demand = 1.8 x average daily demand Maximum hourly demand of maximum day i.e. Peak demand: It is the maximum amount of water consumed in one hour of maximum day during any month of year.                = 1.5 x average hourly demand                = 1.5 x Maximum daily demand/24                = 1.5 x (1.8 x average daily demand)/24                = 2.7 x average daily demand/24                = 2.7 x annual average hourly demand 27

28. Design Periods and Population Forecast This quantity should be worked out with due provision for the estimated requirements of the future . The future period for which a provision is made in the water supply scheme is known as the design period . In designing a Treatment system, the water demand must be the demand at the end of the design period 28

29. Design Periods and Population Forecast Design period is estimated based on the following: Useful life of the component, considering obsolescence, wear, tear, etc. Expandability aspect. Anticipated rate of growth of population, including industrial, commercial developments & migration-immigration. Available resources. Performance of the system during initial period. 29

30. Population Forecasting Methods The various methods adopted for estimating future populations are given below. The particular method to be adopted for a particular case or for a particular city depends largely on the factors discussed in the methods, and the selection is left to the discretion and intelligence of the designer. 1. Arithmetic Increase Method , 2.Geometric Increase Method 3.Incremental Increase Method ,4.Decreasing Rate of Growth Method 5.Simple Graphical Method ,6.Comparative Graphical Method 7.Ratio Method ,8.Logistic Curve Method 30

31. Conventional Surface Water Treatment Surface water treatment can be accomplished by a variety of process trains, depending on source water quality Disinfection Only with No Filtration Conventional Treatment Conventional Treatment with Pretreatment: Some surface waters carry loads of sediment so high that water treatment plants employ a presedimentation step prior to the conventional treatment train. Processes for Source Waters of Very High Quality: For source waters having very low turbidities, low concentrations of TOC, and low concentrations of true color, some of the treatment steps employed in a conventional treatment plant may not be needed, or other filtration processes may be suitable 31

32. Conventional Surface Water Treatment 32

33. Conventional Groundwater Water Treatment Many groundwaters obtained from deep wells have very high quality with respect to turbidity and microbiological contaminants Disinfection Only, or No Treatment: Some groundwaters meet microbiological qualitystandards and have a mineral content such that disinfection may be the only required treatment, and in some states disinfection may not be required. Removal of Iron or Manganese, or Both, Plus Disinfection: If the minerals in the aquifer include iron or manganese, these inorganic constituents may be found in groundwater. For removal of iron and manganese, oxidation, precipitation, and filtration are commonly employed 33

34. Conventional Groundwater Water Treatment Ion Exchange Processes: The most common ion exchange softening resin is a sodium cation exchange (zeolite) resin that exchanges sodium for divalent ions, including calcium, magnesium, and radium Precipitative Lime Softening: Hard water contains excessive concentrations of calcium and magnesium. Both groundwater and surface water can be treated by precipitative lime softening to remove hardness 34