GB2068468A - Vacuum plant for ships for the removal of polluted water - Google Patents

Abstract

In a vacuum plant for ships for the removal of polluted water, a vacuum pump 18 is connected at the suction side to the upper part of a collecting container 10 in which collecting container a polluted water duct 12 (with an inlet valve 16) opens out. The valve 16 controls the suction of water and air together into the collecting container 10 through the duct 12. The duct 12 debouches near the bottom of the collecting container 10 after arriving there from a higher level. The duct 12 may enter the collecting container 10 above or below the level at which it debouches. <IMAGE>

Description

SPECIFICATION Vacuum plant for ships for the removal of polluted water Background of the Invention The invention relates to a vacuum plant for ships, for the removal of polluted water. In known plant a vacuum pump is connected to a collecting container at the suction side, one or more polluted water ducts (with inlet valves) opening out into this collecting container, the said valves controlling the suction of polluted water and air into the ducts and into the collecting container.

Vacuum plants for the removal of polluted water are suitable for ships because they allow freedom in the layout of the ducts. The design and layout of the ducts can take into account the particular spatial conditions prevailing in the given instance; there is no need to produce a pressure head; and smaller duct cross-sections can be used. Vacuum plants for the removal of polluted water of the kind in question are described, for example, in German Patent Specification No.

1,238,858 and in German laid-open Specification no.2455551.

As correct operation of the vacuum plant for the removal of polluted water depends, inter alia, on the vacuum level prevailing in the system, both the vacuum pump and also the polluted water ducts have hitherto been connected to the collecting container above the highest possible water level, so that the suction side of the vacuum pump was in direct communication with the polluted water ducts above the space in the collecting container and above the water level in this container. However, no attention was devoted to the aeration of the polluted water. Attention was merely devoted to the question of maintaining as small as possible the flow resistance between the vacuum pump and the polluted water ducts and also to the question of precluding the chance of back-flow.When, as is frequently the case on ships, the polluted water, containing faeces, has been passed to a clarification plant, a special aeration process took place, by means of compressed air and in conjunction with the clarification process, for the purpose of promoting the aerobic decomposition procedures. However, this aeration did not affect those coarser solid components of the polluted water which were retained, for example by sieves, before the clarification plant, and which were then separated from the polluted water.

Summary of the Invention Underlying this invention is the object of providing a vacuum plant, which serves for the removal of polluted water and which is of the kind defined at the outset of this specification, in which aeration of the polluted water is appreciab!y improved without entailing additional expense. It is proposed according to the invention and for realising this object, that the polluted water duct shall arrive from a higher level and then open out near the bottom of the collecting container.

As a result of this provision, proposed according to the invention, the air, which is suctioned by way of the polluted water duct and which is in the form of bubbles, must "bubble through" the volume of polluted water present in the collecting container before this air is sucked out of the collecting container by way of the vacuum pump. Accordingly, there is achieved, in the collecting container itself, not only strong turbulence, particularly of the sediment, but also continuous aeration of the polluted water in the collecting container.The water receives air in dissolved form, and air bubbles continue to adhere to the constituents of the polluted water. the desired aerobic decomposition processes start to take place immediately; indeed, these decomposition processes take place at all the components of the polluted water removed from the collection points including those components which are not directly passed, in the ship, to a clarification plant.

In dependence on the particular design of the clarification plant communicating with the vacuum plant for the removal of polluted water it is possible, when the provisions of the present invention are adopted, either to reduce the separate aeration process, which has hitherto been carried out in the plant for the removal of polluted water, or possibly to dispense with this aeration process completely.

With regard to the operation of the vacuum plant for the removal of polluted water, it has surprisingly been found that the operation of this plant for the removal of polluted water has even been improved by means of the invention. The additional flow resistance, presented at the collecting container by the modification to the ducting layout, or the loss in pressure, cost practically no energy, as, on account of the relatively short length of the polluted water ducts on a ship, the suction for -- hitherto present at the inlet valve, through which the polluted water, which accumulated at toilets and at other collection points for the polluted water, was sucked into the vacuum ducting system - was so great than even when the inlet valves were opened only for a very short period of time, larger quantities of air than were necessary were suctioned in the normal case, and the suction flow was so powerful that it produced undesirably loud noises. In this respect, when the provisions of the present invention are adopted, the water, through which the air has to flow and which is present in the collecting container and in the end of the polluted water duct, presents a resistance which is altogether of benefit and which somewhat reduces the power of the reactions of the plant when an inlet valve is opened for a short period of time.

It is also feasible, as an alternative to the inventive proposal, to arrange for all the polluted water ducts to be connected to the collecting container at the upper portion of the latter and, in the course of the further path of travel of the polluted water, to thrust the air, expelled from the pressure side of the vacuum pump, through the polluted water after the collecting container.

However, this procedure would entail the drawback of a decreased efficiency, as vacuum pumps should, insofar as is possible, not operate with counterpressure.

Brief Description of the Drawings Embodiments of the invention are described below with reference to the accompanying schematic drawings, in which: Fig. 1 illustrates a first embodiment, with a polluted water duct which enters a collecting container from above the latter; and Fig. 2 illustrates an embodiment with a polluted water duct which is connected to the bottom of the collecting container and enters the latter from below after descending from a higher level.

Detailed Description of the Preferred Embodiments Both Fig. 1 and Fig. 2 only show the collecting container, designated as 10, of a vacuum plant for the removal of polluted water, this vacuum plant being installed on a ship and having a single polluted water duct 12. It is to be understood that a number of ducts may be branched onto the duct 12 for the Durpose of leading polluted water to the collecting container from a number of toilets and other points from which the polluted water is collected. Alternatively, a number of polluted water ducts 12 could individually lead to the collecting container 10. For the sake of simplicity, in the embodiment shown in Fig. 1 only a single toilet 14 is shown, an inlet valve 16 being arranged from this toilet 14.The actuation of the inlet valve 1 6 may take place automatically by means of the underpressure present in the system, when a certain quantity of polluted water has accumulated upstream of the valve. The inlet valve 16 may be so controlled that, each time the valve opens, a specified amount of polluted water - and, also, a specified volume of air, which should be a multiple of the quantity of polluted water is admitted into the polluted water duct 12 before the valve automatically recloses. With reference to the control of the inlet valve 16 reference is made to German laid-open Specification No. 24 55 551, referred to earlier in this specification.Instead of the system whereby the inlet valve 1 6 opens automatically, it is also possible, as is known in the case of vacuum toilets, to provide an opening mechanism which can be actuated at will; however, it is also preferable if the opening duration can be adjusted to a fixed value so as to prevent losses occurring through the inlet valve being open too long.

The underpressure in the collecting container 10 and in the network of polluted water ducts 12 is produced by a vacuum pump 18 and is maintained during operation of the plant for the removal of polluted water. The underpressure causes the polluted water, which has been admitted into the duct system by the inlet valve 16, and also the air which has been admitted, to be sucked into the collecting container 1 0. Whereas the air is immediately removed from the collecting container 10 by the vacuum pump 18, the polluted water accumulates, and thus attains a greater volume in the collecting container 10, before it is pumped out of the collecting container 10 by one or more conventional polluted water pumps (not shown), and is passed to (for example) a clarification plant.A clarification plant of this kind usually has a number of stages in which take place, for example, the successive steps of primary clarification, aeration, biological purification, and secondary clarification. Conveniently, a sieve is arranged upstream of the polluted water pump, which also serves, to comminute the solid components of the polluted water, this sieve retaining the coarser components of the polluted water, so that these coarser components can be removed from the water.

As is clear from Fig. 1, the polluted water duct 12 leads, from above, into the polluted water container 10, which is completely closed and kept under vacuum, this duct 12 terminating close to the bottom of the collecting container and below the water level of the latter. The underpressure produced by the vacuum pump 18 is propagated to the polluted water duct 12 through the polluted water present in the collecting container 1 0.

When the inlet valve 1 6 is closed there is hardly any difference between the underpressure of the polluted water duct 1 2 and in the upper area of the collecting container 10 above the water level in the latter. Consequently, the water level is almost the same in the foremost end of the duct 12 and in the collecting container 10.

The arrangement, shown in Fig. 1, of the downstream end of the polluted water duct 12 relative to the collecting container 10 is such that the suction air must pass the volume of water present in the collecting container 10 before this air can be removed, by suction, by the vacuum pump 18. A guide and distribution device 20 may be provided for effecting a better distribution of the air in the polluted water contained in the collecting container 10. In the- embodiment shown in Fig. 1 this device 20 has the form of a flange which is located at the end of the duct 12 and which surrounds the latter. This flange may possibly also be perforated.

It may be recommendable to arrange for that part of the polluted water duct 12 which debouches into the collecting container 10 -- polluted water thus being present in this particular part of the polluted water duct 12 - to be of greater cross-section than the remaining part of the polluted water duct 12; in this way it is possible to reduce the flow resistance presented to the air by the water contained in the downstream end of the duct 12. This is illustrated in Fig. 2.

As is readily apparent from Fig. 1, the downstream end of the polluted water duct 12, which extends downwardly into the collecting container 10, does not have to be in the form of a tube or hose. Thus, the collecting container 10 may, by the shape given to it, itself form the downstream end of the polluted water duct 1 2.

For example, this modification may be such that a partition wall extends transversely through the collecting container and runs from the upper closure wall to a point lying close to the bottom of the collecting container, the polluted water duct 12 debouching on one side of this partition wall within the upper closure wall of the collecting container, while the vacuum pump 18 is connected to the collecting container on the opposite side of the partition wall. If this modification is adopted the air arriving from the polluted water duct 12 will be sucked, under the partition wall, through the water contained in the collecting container 10.

The embodiment shown in Fig. 2 differs from that shown in Fig. 1 in that the polluted water duct 12 passes to the inner region of the collecting container, close to the bottom of this collecting container, outside the collecting container 10 and, again, leads to this point from above the maximum water level in the collecting container. The construction and arrangement of the remaining part of the polluted water duct are of no significance for the purposes of the invention. In this respect use may be made of experience hitherto gained, with alternately rising and descending duct sections.

Claims (6)

1. Vacuum plant, for ships, for the removal of polluted water, comprising a collecting container whose upper part can be connected to the suction side of a vacuum pump, in which collecting container one or more polluted water ducts (with inlet valves) open out, which valves control the suction of polluted water and air together into the duct and into the collecting container, the polluted water debouching near the bottom of the collecting container after arriving there from a higher level.

2. Vacuum plant as claimed in claim 1, wherein the polluted water duct passes through the bottom of the collecting container.

3. A vacuum plant as claimed in claim 1, wherein the polluted water duct passes into the collecting container from above or laterally, and terminates in the vicinity of the bottom of the collecting container.

4. Vacuum plant as claimed in any one of claims 1 to 3, wherein that part of the polluted water duct which debouches into the collecting container is of greater cross-section than the remaining part of the polluted water duct.

5. Vacuum plant as claimed in any one of claims 1 to 4, comprising a fixed or movable guide and distribution device in the collecting container, this device being used to guide and distribute the inwardly suctioned air.

6. Vacuum plant, substantially as hereinbefore described with reference to and as illustrated by either of the embodiments shown in the accompanying drawings.