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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Autores principales:	Zvikomborero Hoko, Tariro N. Toto, Clarence Farai Mapenzauswa, Tamuka Nhiwatiwa, Lisben Chipfunde, Sylvester Hunguru
Formato:	article
Lenguaje:	EN
Publicado:	IWA Publishing 2021
Materias:	calcium hypochlorite chlorine dioxide morton jaffray water treatment works pre-treatment raw water water quality Environmental technology. Sanitary engineering TD1-1066
Acceso en línea:	https://doaj.org/article/b6727337085c44d0927ccdf73151b015
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spelling	oai:doaj.org-article:b6727337085c44d0927ccdf73151b0152021-11-05T21:17:06ZInvestigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe1751-231X10.2166/wpt.2021.077https://doaj.org/article/b6727337085c44d0927ccdf73151b0152021-10-01T00:00:00Zhttp://wpt.iwaponline.com/content/16/4/1290https://doaj.org/toc/1751-231XRaw 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.;Zvikomborero HokoTariro N. TotoClarence Farai MapenzauswaTamuka NhiwatiwaLisben ChipfundeSylvester HunguruIWA Publishingarticlecalcium hypochloritechlorine dioxidemorton jaffray water treatment workspre-treatmentraw waterwater qualityEnvironmental technology. Sanitary engineeringTD1-1066ENWater Practice and Technology, Vol 16, Iss 4, Pp 1290-1306 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	calcium hypochlorite chlorine dioxide morton jaffray water treatment works pre-treatment raw water water quality Environmental technology. Sanitary engineering TD1-1066
spellingShingle	calcium hypochlorite chlorine dioxide morton jaffray water treatment works pre-treatment raw water water quality Environmental technology. Sanitary engineering TD1-1066 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
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.;
format	article
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
title	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_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_sort	investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at morton jaffray water treatment works, harare, zimbabwe
publisher	IWA Publishing
publishDate	2021
url	https://doaj.org/article/b6727337085c44d0927ccdf73151b015
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Investigating use of chlorine dioxide for pre-treatment of raw water from polluted sources at Morton Jaffray Water Treatment Works, Harare, Zimbabwe

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