Liquid purification or separation – Automatic control
Reexamination Certificate
1999-04-01
2001-05-08
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Automatic control
C015S001700, C210S241000, C210S251000, C210S258000, C210S270000, C210S271000
Reexamination Certificate
active
06228256
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method and an apparatus for cleaning the sand beds of slow sand filters, infiltration basins and pools of other types having sand beds in water treatment works and similar plants, while the filter is in service, by removing a few centimeters of the bed surface, cleaning the sand of the sludge, or filter film, formed on the surface, returning the cleaned sand to the bed, and discharging the separated sludge, suspended in water, to drain or to a suitable disposal site. This is achieved, while the slow sand filter or infiltration basin in question is in service, by traversing the surface of the sand with a tracked cleaning machine in a predetermined pattern which ensures that the entire surface has been traversed by the end of the cleaning operation.
BACKGROUND OF THE INVENTION
When using previously known methods of cleaning filters or basins of this type, the filter or basin in question must be removed from service and drained of water. A machine, such as a compact loader, is then used to remove the top layer of sand and transport it to a suitable location for cleaning. When the filter is refilled with water following cleaning of the bed, the filtered water must be discharged to waste for a period of time before the filter can be returned to normal service, since drying of the sand surface causes disturbance to the microbacterial activity in the bed. Every cleaning operation of this type requires the services of upto three plant workers and in some cases an outside contractor. Since two bed cleaning operations are normally carried out annually, involving the removal of a total of about 6 centimeters of sand, the filter must be refilled with sand every ten years.
SUMMARY OF THE INVENTION
The apparatus of the invention is for cleaning sand of a sand bed of a facility including a slow sand filter, infiltration basin and pools of other types having sand beds in water treatment works and similar plants. The apparatus includes: a chassis having a front end and a rear end; first and second caterpillar track assemblies mounted on respective longitudinal sides of the chassis; a motor mounted on the chassis and being operatively connected to the caterpillar track assemblies for driving the caterpillar track assemblies for propelling the apparatus over the sand bed; electromagnetic clutches interposed between the motor and the first and second caterpillar track assemblies, respectively; a submersible pump mounted at the front end and having a nozzle through which sand to be cleaned of sludge is drawn by suction from the sand bed; a hydrocyclone also mounted on the chassis and being connected to the submersible pump for receiving the sand to be cleaned and separating the sludge therefrom; the hydrocyclone having a first outlet through which the sludge is discharged from the hydrocyclone and a second outlet through which the cleaned sand is discharged; a spreader device mounted below the second outlet for spreading the cleaned sand onto the sand bed; a hose connected to the first outlet for conducting the sludge away from the hydrocyclone and the apparatus; and, a control unit for controlling the electromagnetic clutches for changing the direction of movement of the apparatus as well as controlling the submersible pump, the hydrocyclone and the motor.
The suction nozzle at the front of the machine extends the full width of the machine and is connected to the submersible pump having a capacity sufficient to remove a layer of sand and sludge approximately
3
centimeters thick, and to convey the material thus removed to a hydrocyclone in which the sand is cleaned and redeposited on the bed behind the machine, while the water-suspended sludge is discharged to waste through a hose.
The hydrocyclone operates pursuant to the same principle as a cyclone for removing dust from an air flow. The inlet of the flow is arranged tangential in the upper cylindrical part of the cyclone and all heavy particles are thrown to the periphery of the cyclone because of centrifugal force and drop down through the outlet below while the cleaned air goes out through the upper outlet in the center of the cyclone. The hydrocyclone operates in the same way but separates heavy sand particles from a liquid flow, in this case a water flow. The separated sludge suspended in water is discharged to a waste disposal location at poolside through a hose connected to the hydrocyclone.
The method of the invention employs the above apparatus, which is remote-controlled, to traverse the surface of the sand bed, while the filter is in service, in a predetermined pattern such that the entire surface has been traversed by the end of the cleaning operation.
The time required to clean a filter approximately
2
,
430
m
2
in area is approximately
8
hours, including placement of the cleaning machine in, and removal of the machine from the filter while the unit is in service, representing a very significant saving in time compared to earlier methods.
REFERENCES:
patent: 1150876 (1915-08-01), Nichols
patent: 2346216 (1944-04-01), Fraser
patent: 2389329 (1945-11-01), Streander
patent: 4378290 (1983-03-01), Kennedy
patent: 4818419 (1989-04-01), Mims
patent: 4911831 (1990-03-01), Davison et al.
patent: 5192435 (1993-03-01), Francisco
patent: 6017406 (2000-01-01), Clark et al.
patent: 6115864 (2000-09-01), Davidsson et al.
patent: 2719485 (1978-11-01), None
Ekenback Anders
Lange Klas
Hruskoci Peter A.
Ottesen Walter
Weda Poolcleaner AB
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