Liquid purification or separation – Processes – Treatment by living organism
Patent
1994-05-09
1995-08-22
Wyse, Thomas
Liquid purification or separation
Processes
Treatment by living organism
210617, 210688, 210912, 4352625, C02F 164, C02F 334
Patent
active
054437296
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
THIS INVENTION relates to a method and apparatus for removal of manganese from water and in particular potable or drinking water.
BACKGROUND OF THE INVENTION
The presence of manganese in drinking water constitutes a problem for many water authorities both in Australia (references 26 and 48 referred to hereinafter in the LIST OF REFERENCES) and overseas (4,62) as a cause of manganese-related "dirty-water" in urban distribution systems. Manganese entering the distribution system accumulates as a black manganese oxide biofilm on pipe surfaces and causes consumer complaints when it sloughs off (4, 26, 48, 51, 52, 53, 62). In a chlorinated drinking water system the manganese oxide may be deposited chemically or may be accumulated by viable bacterial biofilms which develop in areas with insufficient chlorination (48, 51, 52, 53).
The manganese-related "dirty water" is not associated with any known health risk but the water is aesthetically unacceptable and causes economic losses by irreversible staining of washing, equipment, manufactured goods and swimming pools.
The problem is widespread in Australia with many cities and towns along the east coast from Cairns in North Queensland to Wyong and Woolongong in New South Wales experiencing problems. Many of these coastal towns rely on tourism as their major industry and are expected to maintain high standards for their tourist image. In 1985, the most affected consumer complaints reached as high as 870 per week (48, 51, 53).
Most water authorities aim through various water treatment strategies to reduce manganese in drinking water to the WHO and NHMRC recommended level of 0.05 mg/l (41,62). The American Water Works Association goal level is 0.01 mg/l (4).
A recent extensive study (48, 51, 52, 53) of the Gold Coast water distribution system has shown that manganese-related consumer complaints occur when manganese levels reach 0.02 mg/l and approaches 80 per week when levels rise to 0.05 mg/l. These consumer complaints are only an indication of the total number of consumers affected.
Current water treatment methods for the removal of manganese and iron from raw water supplies are destratification and oxygenation of the raw water supply (46,61) and chemical oxidation at the treatment plant followed by filtration (61). The most commonly used oxidants are KMnO.sub.4, chlorine, chlorine dioxide and ozone (61).
A survey of treatment plants by Green (24) indicates that the use of sand filters as a manganese removal reactor effectively restricts the filter loading rate to about 5 mh.sup.-1. Modern rapid sand filters are designed to operate at up to 9 mh.sup.-1 (32). It is evident, therefore, that if the economic benefits of high rate filtration are to be achieved for high manganese sources, then significant manganese removal must be achieved at treatment stages preceding filtration (32).
Manganese (II) is not removed by conventional water treatment processes such as alum flocculation unless an oxidation step is included. The most common oxidant is KMnO.sup.4 which converts Mn (II) to Mn (IV) and this colloidal precipitate is subsequently removed by filtration. There are practical difficulties with this method as the rate and extent of oxidation is dependent on factors such as the speciation of manganese, the characteristics of organics present and filter efficiency. These factors are often beyond the control of the plant operator. On occasions very little manganese is removed at worst the concentration may be higher after treatment that in the raw water.
Recently, chlorine and chlorine dioxide have been used in the dual roles of disinfection and oxidation (61).
Biological oxidation of manganese offers an alternative to chemical methods and is already being used to some extent in water treatment, but not to its full potential.
At neutral pH, manganese, unlike iron, is not oxidized by oxygen alone. The oxidation of manganese in natural and destratified oxygenated water storages is due to part of the action of manganese-oxidising microorganisms (22, 5
REFERENCES:
patent: 4391887 (1983-07-01), Baumgarten et al.
patent: 4755304 (1988-07-01), Hallberg et al.
patent: 4880542 (1989-11-01), Sublette
patent: 5080793 (1992-01-01), Urlings
patent: 5240600 (1993-08-01), Wang et al.
patent: 5279745 (1994-01-01), Jeffers et al.
V. Janda, et al., "Removal of Manganese from water in fluidized bed", Chemical abstracts, vol. 110, No. 18, May 1, 1989, p. 382.
C. Czekalla, et al. "Quantitative removal of Iron and Manganese by Miroorganisms in Rapid Sand Filters", Pergamon Press Ltd. GB, vol. 3, 1965, pp. 111-123.
V. Janda, et al., "Managanese removal from water in a fluidized bed", Chemical abstracts, vol. 108, No. 14, Apr. 4, 1988, p. 408.
L. I. Sly, et al. "Effect of water velocity on the early development of manganesse depositing biofilm in a drinking-water distribution system", FEMS Microbiology Ecology, vol. 53, 1988, pp. 175-186.
L. I. Sly, et al. "Binding of Colloidal Mno2 by Edtracellular Polysaccharides of Pedamicrobium Manganicum", Appl. Environmental Microbiology 56, 1990, 2791-2794.
Arunpairojana Vullapa
Dixon David R.
Sly Lindsay I.
Commonwealth Scientific and Industrial Research Organization
The University of Queensland
Wyse Thomas
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