The present invention generally relates to methods and apparatus for separating grease from waste water.
A conventional separator device is disclosed in EP 0 974 386. The known separator device comprises a container with an upper chamber and a lower chamber separated by an inclined intermediate plate. Waste water is supplied to the upper chamber of the container so that grease floating on the surface of the waste water is arranged to be drawn together with waste water through a connecting pipe, with an inlet opening at the top of the upper chamber, down to the lower chamber. Due to the force of gravity, the grease remains on top of the cleaned water in the lower chamber and is discharged through an opening near the highest point below the intermediate plate. The cleaned water is emptied from the upper chamber through a vertical pipe with an inlet near the bottom of the lower chamber and an outlet near the top of the upper chamber. Further sludge and solids may be emptied from the upper chamber near the lowest point above the inclined plate.
The grease separation of this known device is subject to a complicated flow pattern rendering the separation unreliable and requiring a number of procedural steps. Cleaning the device, i.e. maintaining a proper function of the device, is difficult because the grease comes in contact with most parts of the device. Furthermore, although the known separator relies on a basic separation process, it lacks any means for collecting grease in an efficient manner.
As referred to herein, waste water is generally considered to comprise used or dirty process water or so-called grey water. Such grey water may come, for example, from kitchens comprising water used for cleaning, maintenance or other purposes, or from bathrooms or wash basins. This water often contains grease, which, certainly in larger amounts, causes difficulties and problems when it enters a sewage system. Grease-laden or greasy waste water mixing with sewage in mains or piping causes the grease to congeal and adhere to sludge or solids, which may cause blocking of the piping. If such a mixture reaches a (biological) sewage treatment plant, it will decrease bacterial action and compromise the operation of the sewage treatment plant. Accumulated grease is also harmful in holding tanks for waste water as it forms deposits and disagreeable odors.
Consequently, it is of great importance to prevent grease from entering sewage systems. This requires an appropriately functioning grease separator, preferably in the drain line at or near the source of the grease.
A high degree of grease separation is also advantageous in view of the subsequent handling of the grease. If the grease is stored, it lessens the storage volume, and, if the grease is incinerated, incineration of other substances, such as sludge and water is avoided.
As used herein, untreated waste water (i.e. grease-laden or greasy waste water) will be called waste water or grey water. Waste water or grey water that has been subject to grease separation will be called separated waste water or separated grey water.
Accordingly, there is a need to provide a method and apparatus for separating grease, in which the above-mentioned drawbacks are avoided and in which an efficient and high degree of grease separation and reliable operation are attained.
In accordance with the teachings of the present invention, separation by gravity force is enhanced by utilizing the normal layer formation of the materials subject to separation in a grease separator. This is realized by forming a controlled and stable separated waste water layer between the lighter grease layer on the surface and the heavier sludge layer on the bottom of waste water collected in the grease separator. This provides for effective handling of the three main layers.
In addition, means is provided for effectively removing the grease from the grease layer, regardless of the circumstances in which the grease separator is used. Accordingly, means is provided for discharging grease positioned in the grease layer, the means having a relatively large grease receiving portion and a discharge end portion that can be modified for varying discharge methods.
The separation process is advantageously controlled or monitored by a control means, e.g. an observation window provided in the separator device.
The filling degree and discharge of separated waste water is advantageously controlled by level control means.
By arranging the grease discharging means as a discharge port, grease can advantageously be removed from the grease layer by way of gravity or by a pump means.
Another advantageous way of removing grease from the grease layer is by a suction means extending into the grease layer.
Grease may be removed from the grease layer by a pipe means having a receiving portion with a substantially larger cross-section than said pipe means and opening upwards towards the surface area of the grease layer by way of gravity, by suction, or by a pump means in order to increase the efficiency of the grease removal.
By arranging the receiving portion to settle in the grease layer and to follow the movements of the grease layer and the separated waste water layer, grease removal becomes efficient even in unstable circumstances, such as in a moving or rolling vehicle.
In order to provide for efficient grease flow, at least the upper part of the receptacle is advantageously arranged to be heated by heating means.
For maintenance and efficient operational purposes, at least the upper part of the receptacle is advantageously arranged to be cleaned by cleaning means.
Other features and advantages are inherent in the embodiments claimed and disclosed, or will become apparent to those skilled in the art from the following detailed description and accompanying drawings.