Liquid purification or separation – Processes – Treatment by living organism
Patent
1995-09-11
1997-10-28
Popovics, Robert
Liquid purification or separation
Processes
Treatment by living organism
210794, 210795, 210274, 210275, 210189, 210268, 210270, B01D 2446
Patent
active
056814720
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for preventing undesired sand spoilage from a filter bed in which air or other gas is used in contact with the filter medium. The invention is particularly usable in a continuously operating nitrification reactor for biological nitrogen reduction of a suspension or liquid solution.
From the Swedish Patent Specification No. 396 552 (corresponding to U.S. Pat. No. 4,126,546) it is known to perform filtration of a suspension or an emulsion in a filter bed of particulate filter medium by allowing the suspension to flow upwards through the filter bed simultaneously as the filter medium flows downwards through a filtration tank, wherein filtration takes place. Supply of suspension takes place in a lower part of the filter bed and the filtered liquid phase is taken from a zone above the filter bed. The polluted filter medium close to the bottom of the filtration tank is taken out for conveyance to a washing apparatus above the filter bed and after washing is returned to the upper surface of the filter bed. Such conveyance of the filter medium takes place most simply using a so-called mammoth or air lift pump, using air as a conveying medium.
It is also known to use a continuously operating granular filter bed for biological nitrogen reduction of a suspension or liquid solution, i.e. nitrification and denitrification. Bacterial strains suitable for the purpose are used in this case, and these strains are established in the filter bed. In the nitrification process, primarily ammonium compounds are oxidized to nitrates with the aid of oxygen, usually coming from air. Sand of a suitable grain size is preferably used as a filter medium. When the filter is used as a nitrification reactor, a relatively large air stream is blown into the lower part of the filter bed. However, the stream must be restricted to the order of magnitude which does not cause fluidizing of the filter bed. The uppermost layer of the filter sand is even so inevitably whirled up by air bubbles, cause the filtrate above the filter bed to be contaminated by sand. This whirling sand mixed with air bubbles causes some difficulty. In the first place the sand is entrained at the outlet for the filtrate, and in the second place air and sand penetrate from below into the washing apparatus for the sand, in the case where the washing apparatus is sunken into the filtrate zone. The washing function is thus blocked.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to overcome these difficulties. In accordance with the invention, separation of air and sand from the liquid stream is achieved at the places where the difficulties are to be found, and this is done in the following manner. First of all the mixture of air and sand in the liquid is permitted to flow downwards at a rate sufficiently low for the majority of the air bubbles to be separated by rising upwards against the flow. The liquid is subsequently allowed to flow upwards at a rate sufficiently low for the sand not to be entrained in the upward flow but to separate downwards to the bed.
In the prior art apparatus illustrated in FIG. 1, similar to that of the above referred to U.S. Pat. No. 4,126,546, a particle filter medium 1 is enclosed in a tank having walls 2 and a funnel-shaped bottom 3. Sand is well adapted for use as the filter medium 1. The suspension or emulsion to be filtered is supplied, as shown by arrow A, to the tank through inlet 4 in the bottom portion of the tank as shown in FIG. 1 of the '546 patent, or alternatively as shown herein through pipe 4.sup.1. A roof 7 is arranged above the inlet, or each inlet pipe 6 as in the patent, in order to prevent the filter medium from blocking the inlet. The roofs 7 of the patent have a V-shaped cross section. The incoming suspension flows in counter-current to the filter medium. The filtrated and treated liquid phase obtained during the flow of the suspension upwards through the filter bed zone is kept in a collection zone 8 above the fil
REFERENCES:
patent: 3480542 (1969-11-01), Bucksteeg et al.
patent: 4060484 (1977-11-01), Austin et al.
patent: 4126546 (1978-11-01), Hjelmner et al.
patent: 4246102 (1981-01-01), Hjelmner et al.
patent: 4720347 (1988-01-01), Berne
patent: 4746431 (1988-05-01), Gibaud et al.
patent: 5454959 (1995-10-01), Stevens
patent: 5472610 (1995-12-01), Jonsson
patent: 5520804 (1996-05-01), Ward
patent: 5543037 (1996-08-01), Hering, Jr.
patent: 5582722 (1996-12-01), Wachinski et al.
Research Journal WPCF, vol. 62 (1990), No. 3, pp 239-245.
Hagrot Magnus
Jonsson Kurt
Lenvik Lennart
Nordic Water Products AB
Popovics Robert
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