Settling Tank Spray System

The invention is in the field of wastewater treatment equipment. More particularly, the invention is a spray system that can be added to a wastewater settling tank for the purpose of facilitating the removal of the top layer of floating matter contained within the tank.

Wastewater treatment plants commonly direct wastewater into a settling tank to remove, by gravitational settling, suspended particles that are heavier than water. Settling tanks are often circular in shape and have a depth of about ten feet. The diameter of a tank is from 35 to 100 feet and is dependent on the total amount of wastewater to be treated and the number of tanks used.

Settling tanks are also used to remove matter that is of less density than water and therefore can be seen floating on the surface of the water within the tank. This floating material is commonly referred to as scum and is comprised of one or a combination of the following substances: grease, oil, algae or low density waste material.

To accomplish removal of the floating material, skimmers are often employed to push the scum into a drain trough. Most skimmers are in the form of an elongated paddle that has one side in contact with the scum layer and the other side attached to a rotatable boom. The boom is connected to a motor that causes it to rotate about the center of the tank. As the blade rotates within the tank, it sweeps the floating scum layer outwardly toward the perimeter of the tank. To catch the scum and drain it from the tank, a rectangular drain trough is located within the tank proximate its periphery and acts as a drain inlet. The trough includes an angled scumboard or baffle plate that has one end submerged in the water and the other end atop a drain opening at a height even with or slightly above the water level within the tank. As the scum is pushed outwardly by the skimmer, it moves into the trough, passes over the elevated end of the scum board and falls into the drain.

Skimmers are widely used even though there are a number of problems associated with their use. They are expensive to operate since they are electrically powered and must operate continually. There is a considerable amount of maintenance that must be performed on the skimmers because they are adversely affected by both the weather and by the relatively harsh liquids contained within the tanks. A skimmer also lacks a high degree of efficiency since the scum often moves around the drain trough without going in. Finally, in areas that experience at least occasional cold temperatures, a skimmer becomes sluggish and bogged down as it moves through the increasingly viscous liquid. If the skimmer should become covered with ice or snow, it becomes either totally inoperable or almost completely ineffective.

The invention is a spray system that can functionally replace the skimmer of the prior art. The spray system can be incorporated into an existing settling tank and is capable of functioning reliably in almost any weather.

The preferred embodiment of the spray system makes use of two different spray nozzles to move the surface scum into the drain opening of the drain trough. A surface spray nozzle is used to spray liquid onto the surface of the tank and is located proximate the tank's peripheral outer wall. A trough nozzle assembly is located proximate the scumboard of the drain trough and sprays onto the scumboard in a manner that causes a suctioning (vacuum) action on the tank's surface layer. Either of the nozzles can be used alone to replace the conventional skimmer and therefore separate use of either of the nozzles can be considered an alternate embodiment of the invention.

The surface spray nozzle is mounted on a movable support that enables the nozzle to be positioned at any location on the tank's outer wall. In this manner, the nozzle can be moved to the location on the tank where it will have maximum effectiveness based on the location of the drain trough and on the ambient weather conditions (wind, rain, etc.).

The trough mounted nozzle is located on the inlet portion of the drain trough and is preferably mounted proximate the submerged end of the scumboard. The nozzle includes a plurality of liquid outlet ports that are positioned so that they spray onto the scumboard in a direction that causes the water to flow towards the drain opening.

Each of the two nozzles are designed to be connected to a pressurized liquid source by suitable piping. Preferably, the liquid to be sprayed is at least semi-clean water to thereby minimize any possible clogging of the nozzle outlet port(s).

When used singly, either of the nozzles can direct the tank's scum layer into the drain opening of the drain trough. When used together, maximum effectiveness and speed is realized since the surface spray nozzle acts to concentrate the scum in the region of the trough and the trough nozzle acts to rapidly suction the concentrated scum layer into the drain.

FIG. 1 is a plan view of a settling tank that has a drain trough spray nozzle installed.

FIG. 2 is a detailed view of the drain trough spray nozzle.

FIG. 3 is a side view of the drain trough and nozzle structure.

FIG. 4 is a plan view of a settling tank that has a surface spray nozzle installed.

FIG. 5A is a detailed view of the surface spray nozzle.

FIG. 5B is a cross-section of the nozzle taken at the location of the outlet port.

FIG. 6 is a plan view of a settling tank showing the combined use of a drain trough spray nozzle and a surface spray nozzle.

Referring now to the drawings in greater detail, wherein like reference characters refer to like parts throughout the several figures, there is shown by the numeral 1 a settling tank of the type normally found at wastewater treatment facilities.

FIG. 1 shows the tank having a peripheral wall 2 that surrounds a volume of wastewater. Located proximate the wall is a drain trough 4 that includes a drain opening 6 and an angled scumboard 8. The drain opening is a rectangular opening that connects to a pipe 10. The pipe leads to either an evaporation pool or to another separate area where the scum can be treated. The scumboard is shown as having a leading or front end 11 that is submerged slightly below the top surface 12 of the liquid.

FIGS. 2 and 3 provide a more detailed view of the combined trough and nozzle structure.

FIG. 2 is a side view of the nozzle 14 showing it mounted onto the sidewalls 16 of the trough 4. The nozzle includes an elongated hollow body portion 18 that has a plurality of linearly spaced aligned outlet ports 20. One end of the body portion includes a connector 22 that attaches the nozzle to a supply pipe 24. The pipe 24 is connected to a source of pressurized water (not shown).

Each outlet port 20 is preferably slot-shaped and measures approximately two to four inches long and one-eighth inch high. Ports that have other shapes (circular, oval, square, etc.) may also be used. The ports are spaced along the length of the nozzle body to provide an even, dispersed spray pattern of water onto the scumboard. The outer end of the nozzle body is sealed by a removable cap 26 that allows access to the interior of the nozzle body to facilitate any required cleaning thereof.

The nozzle body is adjustably attached to the drain trough by a pair of bracket structures 30. Each bracket structure includes a top mounted strap clamp 32 that functions to attach the nozzle body to the top of the bracket. Each strap clamp can be loosened to thereby allow the nozzle body to be rotated within the straps. This enables the operator to adjust the direction of the nozzle spray. Rotating the body so that the ports are angled downward causes the sprayed liquid to impinge on the scumboard closer to it leading end 11. Rotating the nozzle body in the opposite direction causes the spray to impinge on the scumboard closer to the drain opening 6. The bottom of each bracket structure includes a clamp 34 that removably engages the upper portion of the trough's sidewall. This allows the nozzle to be adjustably placed along the top of the trough thereby enabling the operator with the ability to change the impingement location and direction of the nozzle spray on the scumboard. To facilitate the adjustment process, each bracket has a top portion 36 and bottom portion 38. The two bracket portions are pivotally connected by a through-bolt 40. Loosening of all the clamps (32, 34) allows an operator to fully adjust the nozzle. By allowing the nozzle body to also slide within the strap clamps, the nozzle can even be angled relative to the longitudinal axis of the trough. For example, if the operator did not want the water spray to be aimed directly toward the drain opening, he or she could slide one of the clamps along the trough wall until the outlet ports are aimed toward a corner of the trough. In this manner, a slight amount of separation of the scum can be accomplished in the trough.

FIG. 4 provides a plan view of a settling tank 1 that incorporates a surface spray nozzle 50. The tank includes a drain trough 4 having a drain opening 6 and scumboard 8. Located adjacent the wall 2 of the tank is a spray nozzle 50 that is connected to a source of pressurized water (not shown) by a flexible hose 52. The nozzle is shown spraying water in an angled direction onto the tank's surface scum layer. This direction of spraying causes the scum layer to move in a circular fashion about the center of the tank. During this movement, centrifugal force causes the heavier elements of the scum layer to move outwardly along the circular path of travel. As the scum layer travels about the tank, its outer portion is forced into the drain trough where it is drained from the tank. This continual circular motion of the scum layer eventually results in almost complete removal of the scum layer from the tank.

FIG. 5A provides a detailed side view of the surface spray nozzle 50. The nozzle is made from an "L"-shaped hollow tubular body 51 that has one end attached to a water supply hose 52 by a connector 53. Located in a sidewall of an upwardly extending portion 54 of the nozzle body is a single slot-like outlet port 55. The upper portion 54 of the nozzle is threadedly engaged to a bottom portion 56 of the nozzle. This threaded engagement allows the operator to turn the upper portion relative to the bottom portion and thereby redirect the spraying liquid without moving the nozzle relative to the wall 2. As can be seen in FIG. 5B, the port extends for approximately 30 degrees of arc along the circumference of the nozzle body and is cut in the body in a manner that matches the body's radius of curative.

The nozzle body 51 is fixed to a bracket assembly 57 by a circular clamp 58. The bracket assembly includes a pair of depending leg portions 60 that bracket a vertical top portion of the tank wall 2. The leg portions are approximately two to five inches in height and function to fix and stabilize the nozzle on the tank wall. While sandwiching the wall 2, the leg portions are spaced from each other by a distance that allows the bracket assembly to slide along the wall's upper portion. In this manner, the nozzle can be slid along the entire circumference of the tank and thereby be capable of spraying onto the top surface of any portion of the contained wastewater within the tank. In an alternative method of moving the nozzle, the nozzle and bracket assembly can be vertically lifted and disengaged from the tank's wall. The operator can carry the nozzle to any other location on the tank's wall and then lower it onto the top portion of the tank wall in the new location.

FIG. 6 shows a sediment tank that has both types of nozzles installed. This embodiment combines the unique properties and advantages of both nozzle types to form a system that can rapidly and effectively skim the top scum layer from a sediment tank 1.

The operation of the three embodiments will now be detailed.

In the embodiment shown in FIG. 1, the nozzle 14 sprays down onto the scumboard in the direction of the trough's drain opening 6. The forced flow of water along the trough creates a suction or vacuuming effect on the tank's surface layer of scum near the trough. This causes the scum to be drawn into the drain trough and to flow into the drain along with the liquid sprayed from the nozzle's multiple ports. Continuous action of the drain trough nozzle causes the tank's top scum layer to begin a circular rotation and be drawn into the drain.

In the embodiment shown in FIG. 4, the nozzle 50 sprays water onto the tank's surface in a direction that causes a rotational movement of the tank's scum layer about the center of the tank. It should be noted that the nozzle's outlet port is only one to two feet above the level of the wastewater and the water sprayed from the nozzle is directed almost across the surface of the wastewater within the tank. In other words, the water from the nozzle is aimed so that it imparts the maximum force on the water's surface in a vector parallel to the water's surface. This produces a maximum rotational force on the scum layer while minimizing any downward mixing effect. The circular movement of the scum layer causes an outward centrifugal movement of the scum. As the scum moves outward, it pushes into the drain trough and is skimmed into the drain opening. If the wind conditions are unfavorable to the direction of the water spray (i.e.--cause the spray to be directed away from a desired path), the operator can slide or relocate the nozzle to another location on the tank's wall where it will not be adversely affected by the wind conditions.

The embodiment shown in FIG. 6 employs two nozzles that individually function in the same manner as previously described. However, the combined use of both type of nozzles provides a superior skimming of the scum layer when compared to any of the prior art skimming units or to the independent action of either of the two nozzles. As the surface spray nozzle pushes the scum layer toward the drain trough, the drain trough nozzle pulls the scum into the drain.

The embodiments disclosed herein have been discussed for the purpose of familiarizing the reader with the novel aspects of the invention. Although preferred embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of the invention.