Liquid purification or separation – Processes – Treatment by living organism
Patent
1997-10-03
1999-11-02
Kelly, C H
Liquid purification or separation
Processes
Treatment by living organism
210602, 210617, C02F 332, C02F 300
Patent
active
059763744
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
THIS INVENTION relates to filters, particularly to self cleansing filters for aqueous media.
Aqueous media such as sewage effluent, water for consumption, swimming pool water, industrial effluent, aquaculture pond water and the like, are commonly filtered with particulate filtering materials such as sand, in order to remove suspended solids and biologically active material. Such filtering materials have the disadvantage that they are prone to clogging due to microbial growth on the surface of the filter bed where the organic matter from the raw aqueous media is retained and exposed to oxygen and endemic microbes.
Many sophisticated arrangements have been devised to address this problem of clogging, including moving bed filters, raking devices for the particulate bed surface, and other physical means which break up the filter material.
The use of relatively coarse filtering material and the expansion of the infiltration area have also been used. Unfortunately such methods generally involve high maintenance and have lower treatment performance and typically high construction costs. There is also the need to replenish the upper layers of the particulate filtering material from time to time.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to provide a filter for aqueous media which obviates or at least minimises the aforementioned disadvantages, and provides the public with a useful alternative.
SUMMARY OF THE INVENTION
According to the present invention there is provided an aqueous media treatment system which comprises a ventilated bed of discrete filtration material in which is dispersed an aggregation of living organisms which have the ability to maintain at least a surface layer of the bed in an open and aerobic state.
DETAILED DESCRIPTION OF THE INVENTION
In certain situations such as when the aqueous media is applied by a flood discharge, the surface of the filter bed may be covered with a water and air permeable barrier which excludes some of the light. Such a permeable barrier is preferably designed to also disperse the aqueous media over the surface of the filtration material in such a pattern that the zone furthest from the boundaries of the filtration material receive the highest loading without washing channels in the filtration material. However such dispersion can also be achieved by drip, seepage, sprinkler or mist irrigation over the surface of the permeable barrier; or by the use of a channelling material atop the permeable barrier.
A function of the permeable barrier is to exclude some of the light and thereby provide habitat conditions which suit the grazing organisms, while permitting the passage of the aqueous medium to be filtered. A particularly preferred permeable barrier is a synthetic fibrous matting material such as plastic fibre wadding. Such a material can also double as a dispersant for the aqueous medium.
The discrete filtration material is suitably a low bulk density material having a large surface area and amorphous structure which does not easily form stable aggregates. The material can have a wide range of physical structures from particulate through to fibrous, or combinations of these. Examples include silica particulates such as fine sand, finely ground or shredded non-oily plastics materials such as fine ground polystyrene foam, clay particulates, ground zeolite, diatomaceous earth, powdered activated carbon, short fibre carbon, fine crushed charcoal, and combinations of these materials.
A preferred criterion in the selection of the discrete filtration material mix is that it does not form water stable aggregates in the lower layer/layers. Such aggregation has the effect of preventing large pore spaces from collapsing under saturated conditions and so allows the aqueous medium to pass untreated through the channels produced by the organisms.
Small shallow pore spaces which do not penetrate through the entire bed depth are desirable in that they improve the oxygenation of the bed and infiltration rates. Thes
REFERENCES:
patent: 3635816 (1972-01-01), Golub
patent: 3785798 (1974-01-01), Horai et al.
patent: 4285719 (1981-08-01), Criss
patent: 4624786 (1986-11-01), Schlegel
patent: 5407576 (1995-04-01), Wolf et al.
patent: 5633163 (1997-05-01), Cameron
Dowmus Pty Ltd
Kelly C H
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