APPARATUS FOR TREATMENT OF A LIQUID

Abstract: The invention relates to apparatus (1) for removal of scum or the like from the surface (L) of a tank (2) of liquid, the tank (2) comprising a boom device (3) to sweep over the tank (2) at or adjacent the liquid surface for providing relative movement between the apparatus (1), and in use, liquid in the tank (2) whereby to remove scum from the liquid, the apparatus comprising a well (4) supported on adjustable support means and connected to pump mounting means (6), the pump mounting means being adapted for mounting pump means by positive location alone.

Description: APPARATUS FOR TREATMENT OF A LIQUID The invention relates to apparatus for treatment of a liquid, particularly for the removal of undesired matter carried by activated sludge settling tanks, particularly at the surface thereof. Such settling tanks are often installed in sewage works, where the undesired matter can be scum at the surface, solids floating on or in the liquid, or a mixture of both scum and solids for example. Scum often develops on the liquid surface of activated sludge settling tanks as a result of desludging difficulties, denitrification, and non-degradable surfactants such as chocolate mousse present in the sewage. An outlet weir around the tank periphery generally incorporates a scum board. These scum boards are positioned in front of the weir and prevent scum from passing thereover. Facilities must be provided to allow this floating material which is retained on the tank surface by the scum boards to be removed as frequently as possible. This material is usually collected and concentrated by a surface boom connected to a travelling bridge scraper, and then removed, usually once every revolution of the scraper, by an activator and scum trumpet device. This method of scum removal has disadvantages, however, in that scum removed must be relayed from the scraper bridge to the return sludge system. This necessitates the employment of expensive and complicated pipework. In addition only a small amount of scum is removed as the travelling scraper bridge may only complete a revolution once every hour. According to one aspect of the invention there is provided apparatus for removal of scum or the like from the surface of a tank of liquid, the tank comprising a boom device to sweep over the tank and/or adjacent the liquid surface for providing relative movement between the apparatus and, in use, liquid in the tank whereby to remove scum from the liquid, the apparatus comprising a well supported on adjustable support means and connected to pump mounting means, the pump mounting means being adapted for mounting a pump means by positive location alone. This arrangement has several advantages over prior systems. In particular, the apparatus is cheaper to manufacture and quicker to fit, and one unit fits all settling tanks. Maintenance of equipment is facilitated so that pumps can be easily replaced. In addition, the reduced weight of the apparatus imposes a lower load on the auxiliary structures of the settling tank. The well may be substantially frustoconical and the support means may comprise an upstand slidable vertically in fixings adapted to attach to the boom of the tank. The support means may include pipe means for entrainment of scum from the well to the pump means. The pump mounting means may comprise a flange of the pipe means. The flange may include a mounting surface for mounting the pump means and the mounting surface will preferably be disposed substantially normal to the horizontal, in use. It is preferred that the mounting surface comprises a first level and a second lower level, relative to the first level. The lower level being substantially surrounded by the first level. According to a second aspect of the invention there is provided a settling tank including apparatus as defined hereinabove. According to a third aspect of the invention there is provided a sewage works, including a settlmg tank including apparatus as defined hereinabove. According to a fourth aspect of the mvention there is provided a method of treating liquid sewage, including the step of removing scum from the liquid using apparatus as hereinabove defined. Apparatus embodying the invention is hereinafter described, by way of example, with reference to the accompanying drawings. Fig. l is a side elevational view of apparatus for removing scum from the liquid surface in an activated sludge settling tank, according to the invention; Fig.2 is a plan view of part of A of the apparatus of Fig.1 ; Fig.3 is an end elevational view of the apparatus of Fig. 1 ; Fig.4 is a part side view of the apparatus of Fig. 1 in situ in a sludge settling tank; Fig.5 is a plan view of the apparatus of Fig. l ; and Figures 6 and 7 are plan and perspective views respectively of fixings for use with the invention. Referring to the drawings there is illustrated apparatus 1 for removal of scum or the like from the surface L of a tank 2 of liquid, die tank 2 comprising a boom device 3 to sweep over the tank 2 at or adjacent the liquid surface for providing relative movement between the apparatus 1 , and in use, liquid in the tank 2 whereby to remove scum from the liquid, the apparatus comprising a well 4 supported on adjustable support means 5 and connected to pump mounting means 6, the pump mounting means 6 being adapted for mounting pump means (not shown) by positive location alone. As shown in Figure 1 , the well 4 comprises a substantially frustoconical wall 7 and a base 8 which includes a central aperture. The base 8 is mounted on a upstanding pipe 9 which provides a conduit for removal of scum from the well 4. The conduit leads into a horizontal (in use) section 10 which in turn leads into a further, shorter upstand 11. The upstand is provided with pump mountmg means 6 in the form of a substantially circular flange perpendicular to the upstands 10,11. Referring in particular to Figure 2, it can be seen that the flange 6 comprises an outer, raised part 18 and, relative thereto an inner lower part 13. This enables a suitable pump to be placed on the flange 6 and to site thereon by positive location alone. For the avoidance of doubt, the phrase "positive location" is intended to mean that the pump locates on the flange 6 without the need for any securing means. The mounting means can be provided with a rubber gasket to assist in prevention of leakage. The support means 5 comprises a main upstand 14 which attaches to the boom 3 by releasable clamps 15. At the lower, as viewed, end of the main upstand 14 further releasable clamps 16 are attached by fixing 21 (Figures 6 and 7) which clamp onto the horizontal part 10 of the conduit. Thus, the entire support 5 for the well 4 can be moved both up and down, and side to side. In use, the apparatus is suspended from the boom 3 of a settling tank 2 as illustrated in Figures 4 and 5. The level of the well 4 is adjusted to be just at the surface of the liquid in the tank 2. A suitable pump is mounted on the mounting means 6 and the pump is then attached to a further conduit 17 (Figure 5) which runs up and along the boom 3 and feeds into a central stilling tank 18 of the settling tank 2. As illustrated in Figure 5 the boom 3 is provided with a scraper device 19 which is mounted at the surface of the liquid and extends across the surface along the length of the boom 3. The boom 3 and scraper 19 device with the well 4 are rotated round the tank 2 by a motor (not shown) driving a wheel 20 which runs on the periphery of the tank 2. Thus, there is relative (rotational) movement between the tank 2 and the scraper 19 and d e well 4. As the scraper device 19 collects and concentrates the scum it flows into the well 4 and the pump evacuates the scum therefrom into the stilling tank 18 via the conduit 17. As the level of liquid in the well is always below the liquid surface level in the tank 2 whilst the pump is running, there is a positive draw-off of scum which is also assisted bv the forward movement of the boom 3. It will be understood that the mvention extends into a settling tank incorporating apparatus as hereinbefore defined. Moreover, it will be understood that apparatus embodying the invention is able to be retro fitted to an existing settling tank, and is relatively simple and inexpensive to install in both old and new tanks. Moreover, an apparatus embodying the invention and as described with reference to the drawings has the following advantages :- 1. There is continuous removal of scum. 2. Any scum build up in the stilling box is killed. 3. There is positive draw at the surface of the tank. 4. The draw depth is adjustable to allow for thick consolidated build ups. 5. It can be used on a timer to save pumping costs. 6. No additional pipework and entry to the side of the tank is required. 7. Scum is killed within the tank.

Claims: CLAIMS 1. Apparatus for removal of scum of the like from the surface of a tank of liquid, the tank comprismg a boom device to sweep over the tank at or adjacent the liquid surface for providing relative movement between the apparatus and, in use, liquid in the tank whereby to remove scum from the liquid, the apparatus comprising a well supported on adjustable support means and connected to pump mounting means, the pump mounting means being adapted for mounting pump means by positive location alone. 2. Apparatus according to claim 1 , the well being substantially frustoconical. 3. Apparatus according to claim 1 or claim 2, the support means comprising a upstand slidable vertically in fixings adapted to attach to the boom of the tank. 4. Apparatus according to claim 3 , the support means including pipe means for entrainment of scum from the well to the pump means. 5. Apparatus according to claim 4, the pump mounting means comprising a flange of the pipe means. 6. Apparatus according to claim 5, the flange including a mounting surface for mounting pump means. 7. Apparatus according to claim 6. the mounting surface being disposed substantially normal to the horizontal. 8. Apparatus according to claim 6 or claim 7, the mountmg surface comprising a first level and a second lower level, relative to the first level. 9. Apparatus according to claim 8, the lower level being surrounded by the first level. 10. Apparatus substantially as hereinbefore described with reference to the accompanying drawings. 11. A settling tank, including apparatus according to any of claims 1 to 10. 12. A settling tank, substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings. 13. A sewage works, including a settling tank including apparatus according to any of claims 1 to 10. 14. A method of treating liquid sewage, including the step of removing scum from the liquid using apparatus according to any of claims 1 to 10.

Inventors: WILLIAMS IAN, WILLIAMS, IAN
Applicants: THAMES WATER UTILITIES, WILLIAMS IAN, THAMES WATER UTILITIES LIMITED, WILLIAMS, IAN
Application year: 2001
Main classification: B01D21
IPC codes: B01D17, B01D21