potassium-permanganate and chlorine-dioxide

Topics: Carbon; Chlorine; Chlorine Compounds; Chloroform; Disinfectants; Disinfection; Female; Flocculation; Humans; Ion Exchange Resins; Male; Neoplasms; Oxides; Ozone; Potassium Permanganate; Safety; Sterilization; Urinary Bladder Neoplasms; Water Microbiology; Water Supply

Preoxidation is manipulated to improve performance of algae and soluble manganese (Mn) removal by coagulation-sedimentation for water treatment plants (WTPs) when large amount of soluble Mn presents in algae-laden waters. This study aimed to investigate the effects of preoxidation on the performance of coagulation-sedimentation for the simultaneous removal of algae and soluble Mn, including ionic and complexed Mn. NaOCl, ClO2, and KMnO4 were used to pretreat such algae-laden and Mn containing waters. The variation of algal cell viability, residual cell counts, and concentrations of Mn species prior to and after coagulation-sedimentation step were investigated. Results show that NaOCl dosing was effective in reducing the viability of algae, but precipitated little Mn. ClO2 dosing had a strongest ability to lower algae viability and oxidize ionic and complexed soluble Mn, where KMnO4 dosing oxidized ionic and complexed Mn instead of reducing the viability of cells. Preoxidation by NaOCl only improved the algae removal by sedimentation, whereas most of soluble Mn still remained. On the other hand, ClO2 preoxidation substantially improved the performance of coagulation-sedimentation for simultaneous removal of algae and soluble Mn. Furthermore, KMnO4 preoxidation did improve the removal of algae by sedimentation, but left significant residual Mn in the supernatant. Images from FlowCAM showed changes in aspect ratio (AR) and transparency of algae-Mn flocs during oxidation-assisted coagulation, and indicates that an effective oxidation can improve the removal of most compact algae-Mn flocs by sedimentation. It suggests that an effective preoxidation for reducing algal cell viability and the concentration of soluble Mn is a crucial step for upgrading the performance of coagulation-sedimentation.

Topics: Cell Survival; Chlorine Compounds; Eukaryota; Eutrophication; Manganese; Oxidation-Reduction; Oxides; Potassium Permanganate; Sodium Hypochlorite; Water Purification

This study compared the formation of iodinated trihalomethanes (I-THMs) from iodide-containing raw waters oxidized by chlorine, chlorine dioxide (ClO₂) and potassium permanganate (KMnO₄) at different oxidant concentrations, reaction times, pHs, initial iodide concentrations and bromide to iodide mass ratios. Among the six investigated I-THMs, iodoform was the major species formed during the oxidation using chlorine, ClO₂ and KMnO₄. When oxidant concentration increased from 0.1 to 3.0 mg/L, the formation of I-THMs increased and then decreased for chlorine and ClO₂, but kept increasing for KMnO₄. As the reaction time went by, I-THM concentration increased to a plateau within 10 h (ClO₂ within only 1 h, especially) for all the three oxidants. I-THM formation gradually increased from pH 3.0 to 9.0 and remained stable at pH values higher than 7.5 for chlorine; however, for ClO₂ and KMnO₄ the highest I-THM formation showed at pH 7.0 and 7.5, respectively. As initial iodide concentration increased from 20 to 800 μg/L, the total amount and species of I-THMs increased for the three oxidants. Iodide contributed to I-THM formation much more significantly than bromide.

Topics: Bromides; Chlorine; Chlorine Compounds; Disinfection; Hydrogen-Ion Concentration; Iodine Compounds; Oxidation-Reduction; Oxides; Potassium Permanganate; Trihalomethanes; Water Pollutants, Chemical; Water Purification

Yangtze River raw water from Yangshupu Water Plant, Shanghai was studied in this paper for reduced formation potential of chlorination and chloramination disinfection by-products (DBPs) after pre-oxidation by three kinds of common pre-oxidants, whiich were potassium permanganate, chlorine and chlorine dioxide. Results of chlorination showed that removal effectiveness of all the selected oxidants on total chlorination DBPs was not significant, and the reduction percentages by ClO2, Cl2 and KMnO4 were 8.4%, 5.7% and 3.9%, respectively. The order of DBPs control effect was ClO2, > Cl2 > KMnO4. As to Yangtze River raw water in case of chlorine disinfection, using ClO2 as pre-oxidation agent showed relatively better effect on removal of DBPs. However, chloramination results demonstrated that impacts of the three preoxidants on DBPs formation potential were quite different, and the reduction percentages by ClO2 and KMnO4 were 18.1% and 4.1%, respectively, while pre-chlorination increased the potential by 12.3%. These results revealed that ClO2 had the highest removal effectiveness, meanwhile pre-chlorination should be avoided due to its notable increase in DBPs formation.

Topics: China; Chlorine; Chlorine Compounds; Disinfectants; Disinfection; Halogenation; Oxidants; Oxidation-Reduction; Oxides; Potassium Permanganate; Rivers; Water Pollutants, Chemical; Water Purification

Arsenic is widespread in soils, water and air. In natural water the main forms are arsenite (As(III)) and arsenate (As(V)). The consumption of water containing high concentration of arsenic produces serious effects on human health, like skin and lung cancer. In Italy, Legislative Decree 2001/31 reduced the limit of arsenic from 50 to 10 μg/L, in agreement with the European Directive 98/83/EC. As consequence, many drinking water treatment plant companies needed to upgrade the existing plants where arsenic was previously removed or to build up new plants for arsenic removal when this contaminant was not previously a critical parameter. Arsenic removal from water may occur through the precipitation with iron or aluminum salts, adsorption on iron hydroxide or granular activated alumina (AA), reverse osmosis and ion exchange (IE). Some of the above techniques, especially precipitation, adsorption with AA and IE, can reach good arsenic removal yields only if arsenic is oxidized. The aim of the present work is to investigate the efficiency of the oxidation of As(III) by means of four conventional oxidants (chlorine dioxide, sodium hypochlorite, potassium permanganate and monochloramine) with different test conditions: different type of water (demineralised and real water), different pH values (5.7-6-7 and 8) and different doses of chemicals. The arsenic oxidation yields were excellent with potassium permanganate, very good with hypochlorite and low with monochloramine. These results were observed both on demineralised and real water for all the tested reagents with the exception of chlorine dioxide that showed a better arsenic oxidation on real groundwater than demineralised water.

Topics: Arsenic; Chloramines; Chlorine Compounds; Hydrogen-Ion Concentration; Hypochlorous Acid; Oxidants; Oxidation-Reduction; Oxides; Potassium Permanganate; Water; Water Purification

Existing disinfectants are oxidative agents which all present negative effects on subsequent treatment processes. None of them has decisive advantages over chlorine, although chlorine-dioxide and chloramines might at times be preferable. Optimum treatment practices will improve the removal of organic precursors before final disinfection which could then consist in a light chlorine addition. A philosophy of radical change in water treatment technology encompassing physical treatment without chemicals such as membrane filtration, solid disinfectants is presented.

Topics: Animals; Chloramines; Chlorine; Chlorine Compounds; Disinfectants; Disinfection; Filtration; Mice; Oxides; Ozone; Peroxides; Potassium Permanganate; Sterilization; Time Factors; Water Pollutants, Chemical; Water Pollution; Water Pollution, Chemical