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Brimsu presentation


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Brimsu presentation

  2. 2. INTRODUCTION  Brimsu Head Works was constructed in the year 1927 by Brig Gen. Gordon Guggisberg in the then colonial era ,but the dam was constructed in 1928.The dam has its source from River Kakum .The main intent of this head works was to supply potable water to the Cape Coast community and its environs which has been met till date.  The dam was built to have enough volume of water to be impounded for treatment. The dam is maintained by having a spill way which allows excess amount of water to flow when the level exceeds 25 ft to prevent the dam from a breakdown. Also , the dam is designed periodically to be desilted thus when the sediments accumulate, it is removed.
  3. 3. BRIMSU DAM
  5. 5. 1. IMPONDMENT  This is where the Kakum river is dammed to store enough raw water for abstraction and treatment whiles excess raw water spilled away downstream. The dam has a maximum depth of twenty-five feet(25ft).  During impoundment the quality of the upstream water is improved through ;natural purification, sedimentation and also stratification. . The dam is stratified into three layers ; Upper layer / Epilimnium ,Middle layer / Thermokline / Methalimnium and Hypolimnium.  The upper layer faces the sun thus of a higher temperature and it is about 3 ft.. The middle layer is a mixture of both the upper and lower layers that is a mixed temperature and it is also 9 ft. The lower layer is away from the sun, highly turbid as a result of the settling of most particles and also of 13 ft.  Raw water is however mostly tapped from the middle layer.
  6. 6. SCREENING  During this stage, any floating debris and other materials are trapped by macro and micro screens placed at the entry of the raw water for abstraction. This is to prevent damage to the pump and other appurtenances  At the low lift pumps there are five pumps of which two pumps abstract and transport raw water to the old head works whilst the remaining three pumps abstract and transport raw water to the new works.
  7. 7. PRE-CHLORINATION/AERATION  Pre-chlorination is done when the iron II level in the raw water is high and also to disinfect raw water. This is done by using oxidizing agents such as potassium permanganate (KMnO 4 ) and calcium hypochloride( CaHOCl) . These oxidizing agents oxidize the soluble Fe2+ to insoluble Fe3+ for removal of the iron  During aeration, raw water flows through cascade aerator to allow air to dissolve and blow off odour in the raw water thus improving upon the colour and taste of the raw water.  The cascade aerator provides a large surface area for aeration to occur.
  9. 9. COAGULATION  Raw water is normally accompanied by impurities which require treatment before consumption hence, a coagulant like Aluminium Sulphate (Al2 (SO4)3) is used. Aluminium Sulphate when added to raw water brings all the impurities (particles) together, reducing the turbidity of raw water. This is because the particles are negatively charged thus repelling each other. However the aluminium is positively charged hence serving as a central nucleus to attract the clayey particles to aid in coagulation
  10. 10. FLOCCULATION  After Aluminium Sulphate (Al2 (SO4)3) has been added to the raw water in the coagulation process, the pulsator clarifier mixes the Aluminium Sulphate (Al2 (SO4)3) to form flocs and finally initiates it into the sedimentation process. The pulsator clarifier also receives the raw water from the aerator and has laterals to disperse the water to different chambers.
  12. 12. SEDIMENTATION  This a raw water treatment process where the flocs formed during flocculation settle at the bottom of the sedimentation tank as sludge by force of gravity.  When the sludge accumulates in the sedimentation tank, it is usually referred to as sludge blanket. When the sludge blanket level rises to a particular point, it reduces the volume of supernatant in the sedimentation tank, hence the need to disludge.
  13. 13. FILTRATION  During sedimentation process, particles with small densities are not able to settle and are therefore trapped by the filter bed. The filter bed is chemically treated to remove bacteria at a percentage of 99%. As the filtration process continues, the trapped particles accumulate within the filter medium, blocking the medium from any further filtration. As a result of this, backwashing is done to free the medium from trapped particles so that the process can continue.
  14. 14. PH ADJUSTMENT/DISINFECTION  Here, hydrated lime is added to the filtered water to neutralize the pH since the initial Aluminium Sulphate (Al2 (SO4)3) added to the raw water makes it acidic. Similarly, the addition of hydrated lime also softens the final water. Calcium hypochloride is also added alternatively in place of chlorine gas. Post-chlorination is done to disinfect or kill any pathogen in the filtered water and a residual is left to disinfect any pathogen which may arise during distribution. All these activities take place in the clear water storage.
  15. 15. DISTRIBUTION  At the clear water pump house, there are five high lift pumps which are used to pump treated water to distribution areas through trunk mains.
  16. 16. LABORATORY ACTIVITIES  At the Brimsu New Head Works, a lot of tests are carried out on the raw, settled and final water at a 2hour interval to ascertain their parameters. The various tests include colour, turbidity, pH, alkalinity, hardness, chloride ions and residual chlorine and the like. It is always important that the treated water parameters fall within the World Health Organization guidelines
  17. 17. Test for Alkalinity  Measure 50ml of the water sample into a flask.  Add two to three drops of methyl orange, the solution now turns orange.  Using a pipette, measure 20ml of hydrochloric acid (HCl) and add it drop by drop to the solution in the flask until the solution changes from orange to pink red indicating the endpoint has been reached. Record the reading from the pipette
  18. 18. Test for Hardness  Measure 50ml of the water sample into a flask.  Add two to three drops of ammonia (NH3) buffer to the sample.  Add a few portions of Erychrome black T, the solution now turns violet.  Using a pipette measure 20ml of EDTA, add it to the solution in the flask drop by drop until the violet colour changes to blue black indicating the endpoint has been reached. Record the reading from the pipette.
  19. 19. Test for Chloride ions  Measure 50ml of the water sample into a flask.  Add two to three drops of Potassium hexaoxodichromate (VI) (K2Cr2O7), the solution now turns yellow.  Using a pipette measure 20ml of Silver nitrate (AgNO3), add it to the solution in the flask drop by drop until the orange colour changes to deep brown indicating the endpoint has been reached. Record the reading from the pipette.  
  20. 20. Test for colour  When testing for the colour of raw water, 10ml of raw water is measured and diluted to50ml mark on the test tube.In colour determination for raw water, the comparator with precision from 10 is used. The test tube containing the diluted raw water is then placed into the comparator in which a clear standard solution already exists. Using the lovibond disc, the colour of the raw water is then determined by adjusting the disc to match the colour of the raw water. In  Similarly, settled water and final water colour are determined by measuring 50ml of each sample into a test tube and subsequently placing them into the comparator for onward colour determination using the lovibond disc as described above.
  21. 21. Test for Turbidity  Here few portion of the raw, settled and final water samples are placed into a standard tube which is uncalibrated. The tube is then placed into the microprocessor turbidity meter to read the turbidity of the water sample
  22. 22. Test for pH  When testing for the pH of raw water, it is placed in a test tube and methyl red indicator of about 3 to 4 drops is added and a comparator matching that indicator is used to determine the pH Also, for that of settled water, bromocrycol blue is used to determine the pH with its comparator as well that of the final water. Also a pH meter can be used to determine the pH of the water.
  23. 23. Jar Test  Measure 1litre of raw water into six beakers  Pipette 3ml, 4ml, 5ml, 6ml,7ml,8ml of Aluminium Sulphate solution which is equivalent to 30ppm/g/m3 ,40ppm/g/m3,50ppm/g/m3,60ppm/g/m3,70ppm/g/m3,80pp m/g/m3respectively into each beaker.  Place the beaker in the sedimentation jar test device, lower the stirrers and increase the stirring speed initially to 80 ms-1 for about three minutes for the Aluminium Sulphate solution to mix thoroughly with the raw water for flocs to form. Reduce the speed of the stirrers to 40 ms-1 for about seventeen minutes so that the flocs will not be destroyed. After set time, remove the stirrers from the samples and allow the flocs to settle for thirty minutes. After settling, fetch portions of each sample and perform the following test on them: pH, turbidity and colour. From the results obtained, select one of the samples which meet the standard parameters with a moderate Aluminium Sulphate solution and perform alkalinity, hardness and chloride ion test on the sample.
  25. 25. Test for Residual Chlorine  The quantity of chlorine in the final water is tested using a comparator.10ml of the final water is fetched into a test tube and one tablet of DPD is placed into it and allowed to dissolve. After dissolution the colour formed is then compared to the standard by moving the chlorine disc to match the colour in the test tube and the corresponding value is recorded.
  26. 26. RECOMMENDATIONS  Workers and Students on attachment should be provided with protective clothes and they should be forced to wear them at all times.  students on attachment should be entitled to some considerable financial emolument.  Students on attachment should be shifted every two weeks to the various units so they can acquaint themselves with the activities of the various units.
  27. 27. CONCLUSION  One can utter without misgiving that an invaluable worth of knowledge and skill has been gained from our attachment at the Brimsu New Head Works and this has brought to bear an appreciation of theoretical concepts acquired and as well as practical. We also extend our immeasurable gratitude to the station manager, his assistant, the quality control officers and the rest of the workers.