Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe
Raw water quality deterioration has affected capabilities of Conventional Water Treatment Processes (CWTP) in many countries. CWTP used at Morton Jaffray Water Treatment Works (MJWTW) in Harare have proven ineffective due to pollution. The study investigated the use of chlorine dioxide (ClO2) as an...
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| Format: | Article |
| Language: | English |
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IWA Publishing
2021-10-01
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| Series: | Water Practice and Technology |
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| Online Access: | http://wpt.iwaponline.com/content/16/4/1290 |
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| author | Zvikomborero Hoko Tariro N. Toto Clarence Farai Mapenzauswa Tamuka Nhiwatiwa Lisben Chipfunde Sylvester Hunguru |
| author_facet | Zvikomborero Hoko Tariro N. Toto Clarence Farai Mapenzauswa Tamuka Nhiwatiwa Lisben Chipfunde Sylvester Hunguru |
| author_sort | Zvikomborero Hoko |
| collection | DOAJ |
| description | Raw water quality deterioration has affected capabilities of Conventional Water Treatment Processes (CWTP) in many countries. CWTP used at Morton Jaffray Water Treatment Works (MJWTW) in Harare have proven ineffective due to pollution. The study investigated the use of chlorine dioxide (ClO2) as an alternative pre-treatment chemical. Its effectiveness was compared to that of calcium hypochlorite (Ca(CIO)2) used at MJWTW. Grab raw water samples from MJWTW were collected between January and March 2020 and pre-treated with ClO2 and Ca(CIO)2 followed by jar tests with alum to determine pre-treatment effectiveness. Parameters analyzed included electrical conductivity (EC), total dissolved solids (TDS), total solids (TS), turbidity, chemical oxygen demand (COD), pH and total algae counts (TAC). The raw water had mean TDS (264 mg/L), TS (440 mg/L), turbidity (7.1 NTU), COD (85 mg/L), pH (7.9) and TAC (28.4 × 106 cells/mL). The optimum alum dosage without pre-oxidation was 80 mg/L. Pre-oxidation with 0.075 mg/L ClO2 reduced alum dosage to 60 mg/L. This ClO2 dosage was compared to a Ca(CIO)2 dosage of the same concentration and strength at 5 and 15-minutes contact time before alum dosage at 60 mg/L. The treated water quality parameter levels proved better performance for ClO2 compared to calcium hypochlorite. HIGHLIGHTS
Raw water quality deterioration in Lake Chivero has complicated treatment and treatment costs.;
Chemicals currently used have become ineffective including calcium hypochlorite, which creates risk of formation of carcinogenic compounds.;
Chlorine dioxide was considered an an alternative as it has been used widely elsewhere, enhances coagulation compared to calcium hypochlorite, and thus is likely to be economic.; |
| first_indexed | 2024-12-18T02:08:31Z |
| format | Article |
| id | doaj.art-b6727337085c44d0927ccdf73151b015 |
| institution | Directory Open Access Journal |
| issn | 1751-231X |
| language | English |
| last_indexed | 2024-12-18T02:08:31Z |
| publishDate | 2021-10-01 |
| publisher | IWA Publishing |
| record_format | Article |
| series | Water Practice and Technology |
| spelling | doaj.art-b6727337085c44d0927ccdf73151b0152022-12-21T21:24:33ZengIWA PublishingWater Practice and Technology1751-231X2021-10-011641290130610.2166/wpt.2021.077077Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, ZimbabweZvikomborero Hoko0Tariro N. Toto1Clarence Farai Mapenzauswa2Tamuka Nhiwatiwa3Lisben Chipfunde4Sylvester Hunguru5 University of Zimbabwe, Department of Construction and Civil Engineering, Box MP 167, Mt Pleasant, Harare, Zimbabwe Boltgas, 58A Steven Drive, Box 59A, Msasa, Harare, Zimbabwe Boltgas, 58A Steven Drive, Box 59A, Msasa, Harare, Zimbabwe University of Zimbabwe, Biological Sciences Department, Box MP 167, Mt Pleasant, Harare, Zimbabwe City of Harare City Environment Management Unit, Town Clerk's Office, P. O. Box 990, Julius Nyerere Way Town House, Harare, Zimbabwe Boltgas, 58A Steven Drive, Box 59A, Msasa, Harare, Zimbabwe Raw water quality deterioration has affected capabilities of Conventional Water Treatment Processes (CWTP) in many countries. CWTP used at Morton Jaffray Water Treatment Works (MJWTW) in Harare have proven ineffective due to pollution. The study investigated the use of chlorine dioxide (ClO2) as an alternative pre-treatment chemical. Its effectiveness was compared to that of calcium hypochlorite (Ca(CIO)2) used at MJWTW. Grab raw water samples from MJWTW were collected between January and March 2020 and pre-treated with ClO2 and Ca(CIO)2 followed by jar tests with alum to determine pre-treatment effectiveness. Parameters analyzed included electrical conductivity (EC), total dissolved solids (TDS), total solids (TS), turbidity, chemical oxygen demand (COD), pH and total algae counts (TAC). The raw water had mean TDS (264 mg/L), TS (440 mg/L), turbidity (7.1 NTU), COD (85 mg/L), pH (7.9) and TAC (28.4 × 106 cells/mL). The optimum alum dosage without pre-oxidation was 80 mg/L. Pre-oxidation with 0.075 mg/L ClO2 reduced alum dosage to 60 mg/L. This ClO2 dosage was compared to a Ca(CIO)2 dosage of the same concentration and strength at 5 and 15-minutes contact time before alum dosage at 60 mg/L. The treated water quality parameter levels proved better performance for ClO2 compared to calcium hypochlorite. HIGHLIGHTS Raw water quality deterioration in Lake Chivero has complicated treatment and treatment costs.; Chemicals currently used have become ineffective including calcium hypochlorite, which creates risk of formation of carcinogenic compounds.; Chlorine dioxide was considered an an alternative as it has been used widely elsewhere, enhances coagulation compared to calcium hypochlorite, and thus is likely to be economic.;http://wpt.iwaponline.com/content/16/4/1290calcium hypochloritechlorine dioxidemorton jaffray water treatment workspre-treatmentraw waterwater quality |
| spellingShingle | Zvikomborero Hoko Tariro N. Toto Clarence Farai Mapenzauswa Tamuka Nhiwatiwa Lisben Chipfunde Sylvester Hunguru Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe Water Practice and Technology calcium hypochlorite chlorine dioxide morton jaffray water treatment works pre-treatment raw water water quality |
| title | Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe |
| title_full | Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe |
| title_fullStr | Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe |
| title_full_unstemmed | Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe |
| title_short | Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe |
| title_sort | investigating use of chlorine dioxide for pre treatment of raw water from polluted sources at morton jaffray water treatment works harare zimbabwe |
| topic | calcium hypochlorite chlorine dioxide morton jaffray water treatment works pre-treatment raw water water quality |
| url | http://wpt.iwaponline.com/content/16/4/1290 |
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