Liquid purification or separation – Processes – Chemical treatment
Patent
1996-01-11
1997-12-09
Lithgow, Thomas M.
Liquid purification or separation
Processes
Chemical treatment
210798, 210209, 210220, 210262, 210151, 210356, 210474, 210475, 261 4, 261 5, 261 6, B01D 35027, B01D 2927
Patent
active
056956517
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the treatment of liquid waste such as sewage, and more particularly relates to apparatus for screening raw sewage before it proceeds to biological or other treatment.
In sewage treatment plants, it is necessary to screen the inflow of raw sewage before further treatment. The screening process removes non-biodegradable solid material such as condoms, tampons, nappy liners etc. A variety of inlet screens are available on the market. Many of them, such as rake bar screens, produce screenings with a high content of faecal matter which require washing. Coarse screens let through an unacceptable amount of solid materials. Fine screens tend to block (known as "blinding") very easily.
The present invention overcomes the above problems by making use of an air system which imparts energy and agitation to a screening sack. The invention provides a method of screening of liquid waste to remove solid material therefrom, comprising passing the liquid waste in a downward stream through a suspended sack filter, and agitating the sack filter and the liquid stream by discharging a stream of bubbles upwardly through the liquid from below the sack filter.
The invention also provides an inlet screen, comprising an upright hollow column, having an opening at the top; a sack filter suspended with its open end at or near the opening of the column, the sack extending downwardly into the column; an air diffuser at the lower part of the column; and an outlet from the column, whereby in use liquid waste flows into the top of the column, through the sack filter to the outlet, the sack filter and liquid waste being agitated by discharge of air from the air diffuser.
The air diffuser produces streams of air bubbles which pass upwardly through the liquid in the column. This results in agitation both of the liquid waste itself and also of the sack filter. This agitation helps to prevent the sack filter from blinding, it breaks down faecal matter in the liquid waste, and it improves washing of the screenings.
Preferably means are provided for ensuring a level of liquid waste in the column between the lowermost and uppermost parts of the sack filter.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference is now made to the accompanying drawings, in which:
FIG. 1 is a diagrammatic side view, partly in section of an inlet screen according to one embodiment of the invention;
FIG. 2 is a diagrammatic side view of an inlet screen according to another embodiment of the invention;
FIG. 3A is a diagrammatic side view and FIG. 3B a transverse section of a further embodiment; and
FIG. 4A is a diagrammatic side view and FIG. 4B a plan view of a still further embodiment.
In FIG. 1, the column comprises a cylindrical tube 1 of plastics or other suitable material, such as UPVC. The tube is arranged generally upright. The lower end of the tube 1 has a flanged connection 2 to a lower reservoir or "bucket" 3, which may also suitably be of UPVC. The bucket 3 has a slightly greater diameter than the tube 1. The top of the tube 1 is open to receive inflow 4 of crude sewage, and an outlet 5 is provided at the base of the tube, just above the flanged connection 2.
A sack filter 6 is positioned across the top end of the tube 1 and held in place by retention clips 7 fitted to the side of the tube. The sack filter 6 extends to its lower end 6A some distance down into the tube from the top. A suitable grade of sack filter is one having 4 mm.times.2 mm holes, although filters with other size holes can be used depending on the degree of filtration which is required.
In the bucket 3, an air diffuser 8 is arranged, so as to direct a stream of air bubbles upwardly through the liquid in the tube. The air diffuser 8 is provided with an air supply pipe 9 which passes through a side wall of the bucket to external air supply means. The air diffuser is suitably of the diaphragm or membrane type. This comprises a flexible multi-perforated membrane. When air is supplied, the membrane partly inflates and streams of fine air bubbles escape from the multiple perfo
REFERENCES:
patent: 1095494 (1914-05-01), Edey
patent: 1208882 (1916-12-01), Young
patent: 1401723 (1921-12-01), Palich
patent: 1666164 (1928-04-01), Chappell
patent: 1728381 (1929-09-01), Waters
patent: 1734999 (1929-11-01), Cruickshank
patent: 1824350 (1931-09-01), Hosking
patent: 2792943 (1957-05-01), Mackintosh
patent: 3419151 (1968-12-01), Smith
patent: 3756410 (1973-09-01), Moody
patent: 3923656 (1975-12-01), Krebs
patent: 5178752 (1993-01-01), McKinnon
patent: 5234632 (1993-08-01), Schmidt
patent: 5487829 (1996-01-01), Safferman
Apoc Limited
Lithgow Thomas M.
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