GB2500270A

GB2500270A - Apparatus for monitoring a sewerage system

Info

Publication number: GB2500270A
Application number: GB1204995.3A
Authority: GB
Inventors: David Robinson
Original assignee: Veolia Water Outsourcing Ltd
Current assignee: Veolia Water Outsourcing Ltd
Priority date: 2011-12-01
Filing date: 2012-03-21
Publication date: 2013-09-18
Anticipated expiration: 2032-03-21
Also published as: GB2500270B; GB2534072A; GB2497157A; GB2535045A; GB201605008D0; GB201605007D0; GB2534072B; GB2535045B; GB201204995D0; GB2497157B; GB201216308D0; GB201120804D0

Abstract

A method is disclosed for sensing a failure in a sewerage system having a sewer 50 and a plurality of drains 40 that feed sewage to the sewer 50. The method comprises receiving information from a plurality of sensing apparatuses 10 associated with respective drains 40, the received information indicative of sewage levels within the respective drains 40, and identifying a failure within the sewerage system in accordance with the received information.

Description

APPARATUS FOR MONITORING A SEWERAGE SYSTEM

FIELD

5 This invention relates to apparatus for determining the occurrence of a failure in a sewerage system. Embodiments of the invention also relate to determining the location of such a failure.

BACKGROUND

10

A public sewer is typically connected to receive matter in the form of surface water and/or foul water from buildings, such as houses, shops, offices and factories and certain outside areas associated therewith. For ease of reference, this surface water and/or foul water will be referred to herein as "sewage". Sewage flows from such

15 buildings to the public sewer through a conduit known as a "drain" that connects a single building to the public sewer. Typically, a public sewer runs below a highway or in common land or public land; any drain connecting to the sewer is therefore usually partly in the highway or the common or public land.

20 When a blockage occurs in a drain or sewer, water levels rise, backing up the drain until it overflows at or adjacent to the building served by the drain. The responsibility for unblocking the blockage rests with the owner of the sewer or drain which causes the back up of water.

25 Changes to the law in England and Wales that came into effect on 1 October 2011 affect the ownership of drains. In particular, these changes transferred to those responsible for public sewerage ownership of the part of each drain between the public sewer and the legal boundary of the building to which the drain runs. This part of the drain is called the "lateral drain". Prior to 1 October 2011, responsibility for the whole 30 of the drain, regardless of its location rested with the owner of the building served by it. Since 1 October 2010, the responsibility of the building owner has reduced such that he/she is only responsible for the part of the drain within the boundary of land on which the relevant building is sited.

As a result of this change in law, should part of the drainage system become blocked and start to overflow, or overflow for some other reason, it is not readily discemable whether there is a blockage in the public part of the sewer system - that is in the public sewer or in the lateral drain that is the responsibility of the sewerage company 5 responsible for the public sewer - or whether the blockage is in the part of the drain which is the responsibility of the owner of the relevant building.

This difficulty can be further appreciated with reference to Figure 1. This figure shows a typical arrangement of a public sewer in the highway with a single drain extending 10 therefrom to collect sewage from a building. A blockage at any of the points A, B, C or D will eventually manifest itself as sewage overflowing at point Z. The owner of the building served by the drain would then usually contact the company responsible for the provision of sewerage services. Previously, that company would have dealt with the blockage by inspecting to determine who is responsible before cleaning parts of the 15 sewer system for which it was responsible. With the change in law referred to above and the resulting change in responsibility at a specific point along the drain, it is generally not possible to know where the blockage is located or where the surcharge is coming from because the drain becomes full.

20 Generally the only cost effective way to know where the blockage is and therefore who is responsible for it is to clear the blockage. As clearing the blockage is usually by cleaning which often destroys all evidence of the blockage, it is often not possible conclusively to establish where the blockage was and so who was actually responsible for clearing it. For example, a blockage at point A or B would be the responsibility of 25 the sewerage company as lying on the public side of the legal boundary to the building, or the public side of the land on which the building is sited; whereas a blockage at point C or D would be the responsibility of the owner of the building as lying within that boundary. In addition, it may be found that the drain is surcharged due to a blockage in the public sewer. Such a blockage would be the responsibility of the 30 sewerage company.

As the location of the blockage cannot therefore usually be determined, the cost of clearing the blockage would be likely to be borne by the sewerage company. In those cases where the blockage was at C, this cost is incorrectly borne by the sewerage

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company and so this is to their disadvantage. There is therefore a need to establish the location of blockages in sewer systems, in advance of clearing it and to improve serviceability by knowing about the existence of a blockage etc before it affects the sewerage company's customer.

5

In the event that it is determined that the drain is not blocked but it is instead surcharged due to a failure such as a blockage in the public sewer, the location of the blockage in the public sewer then has to be determined. Such locating of the blockage is normally achieved by lifting manhole covers in order to identify the parts of the sewerage system 10 that are affected by the blockage. The location of the blockage can then be approximated from what is seen by the personnel lifting the manhole covers. Such a process of locating a blockage within a sewerage system is unduly time consuming and is often risky to operators, while also being extremely disruptive to road users and customers.

15

SUMMARY

According to a first aspect of the invention there is provided a method for sensing a failure in a sewerage system. The sewerage system having a sewer and a plurality of 20 drains that feed sewage to the sewer. The method comprises receiving information from a plurality of sensing apparatuses associated with respective drains. The received information is indicative of sewage levels within the respective drains. The method also comprises identifying a failure within the sewerage system in accordance with the received information.

25

A failure within the sewerage system may be identified when the received information is indicative of at least one respective drain being surcharged.

Furthermore, a failure in the sewer may be identified when the received information 30 indicates that a plurality of consecutive drains of the plurality of drains are surcharged.

It will be appreciated that reference to "consecutive", "neighbouring", or "adjacent" drains need not necessarily refer to drains that are geographically located next to each other but may refer to drains that are consecutive or similar in height above a fixed

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point, such as sea level or any other suitable ordnance datum. That is, consecutive drains may refer to the order in which drains will become surcharged. Both the geographical location of the drains is stored within the apparatus, along with information indicative of the order in which sewage would fill drains in the event of a 5 blockage or surcharge, for example, information relating to the drain height or drain sensor height, at any point in the sewerage system, to thereby define which drains are considered "consecutive", "neighbouring", or "adjacent".

The level of sewage that will result in a drain being identified as surcharged will depend 10 upon the position of the sensor within the drain, which may in turn depend upon characteristics of the sewer such as the angle of the drain, the location of the property boundary, and the length of the drain. It is for at least some of these reasons that "consecutive" need not refer to drains that are directly, geographically, adjacent.

15 The method may further comprise identifying that the failure in the sewer is a result of a blockage or siltation in the sewer when the plurality of consecutive drains become surcharged sequentially from the most downstream drain to the most upstream drain of the plurality of consecutive drains.

20 A blockage or siltation will result in the sewage levels increasing in the sewer and proximate drains upstream of the blockage or siltation as more sewage enters the sewerage system. The sewer and drains proximate in height above the blockage or failure point or siltation will therefore slowly become surcharged with the drains becoming surcharged in the order of their level above the point where the blockage or 25 failure occurs. It will again be appreciated that the term "nearest" is primarily used to refer to the drain that is most proximate to a physical location, but may also refer to the first drain to be surcharged due to both its location and height with respect to the sewer.

In addition, the method may further comprise identifying that the failure in the sewer is 30 a result of hydraulic overloading when the information indicates that the plurality of consecutive drains have become surcharged substantially simultaneously.

A large influx of water into a sewer due to a storm, for example, may result in the sewerage system becoming surcharged very quickly and drains of the sewerage system

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in the vicinity of the storm also becoming surcharged substantially simultaneously. It will be appreciated that the drains need not be surcharged at exactly the same time, but it will be appreciated that the difference in time taken to surcharge consecutive drains is likely to be very small compared to the time taken to surcharge consecutive drains when 5 the public sewer fails due to a blockage or siltation.

Whatever the cause of the blockage or failure, the speed at which additional drains become affected allows the sewerage company to determine the safest and most economic response. For example, if adjacent drains become affected rapidly, then a 10 rapid (emergency) response will be appropriate, whereas if neighbouring drains are not affected or become affected slowly then a more planned response will be appropriate.

Furthermore, the method may further comprise locating the failure of the sewer as being between the most downstream drain of the plurality of consecutive drains and a non-15 surcharged drain nearest to and downstream of the most downstream drain of the plurality of consecutive drains.

The method may also further comprise identifying a failure in a drain when the received information indicates that only one drain of a plurality of consecutive drains is 20 surcharged.

In addition, the method may further comprise identifying an action for rectifying the identified failure. For example, information relating to the location of the failure may affect the response provided. Certain personnel or equipment may be required due to 25 the location of the failure. Furthermore, information relating to the severity of the failure could also be provided, which will also affect the required response for rectifying the identified failure.

The action for rectifying the identified failure may comprise sending an alert including 30 information regarding the failure to an identified technician. The alert may be sent by text message to the identified technician, or alternatively by radio to a central service point.

5

According to a second aspect of the present invention apparatus for sensing a failure in a sewerage system is provided. The apparatus may be a sewer and a plurality of drains that feed the sewer may be provided. The apparatus may be arranged to perform any of the method steps disclosed above.

5

The apparatus may comprise a communication unit and a processor. The communication unit may be arranged to receive information from a plurality of sensing apparatuses associated with respective drains. The received information may be indicative of sewage levels within the respective drains. The processor may be 10 arranged to identify a failure within the sewerage system in accordance with the received information.

By receiving information relating to sewage levels in respective drains of a sewerage system the apparatus may be able to identify whether a failure in the sewerage system 15 has taken place within the sewer or within one or more of the drains. Furthermore, the apparatus is able to identify the specific location of the failure within the sewer.

The processor may be arranged to identify a failure within the sewerage system when the received information may be indicative of at least one respective drain being 20 surcharged.

Furthermore, the processor may be arranged to identify a failure in the sewer when the received information indicates that a plurality of consecutive drains of the plurality of drains are surcharged.

25

Also, the processor may be arranged to identify that the failure in the sewer is a result of a blockage or siltation in the sewer when the plurality of consecutive drains become surcharged sequentially from the most downstream drain to the most upstream drain of the plurality of consecutive drains.

30

In addition, the processor may be arranged to identify that the failure in the sewer is a result of hydraulic overloading when the information indicates that the plurality of consecutive drains have become surcharged substantially simultaneously. Additionally, a rain gauge located near to the blockage, or near to the sewerage system upstream of

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the blockage may be monitored and data from it indicating a heavy rain fall could also be collected and used to help in the identification of a failure due to hydraulic overloading.

5 The processor may also be arranged to locate the failure of the sewer as being between the most downstream drain of the plurality of consecutive drains and a non-surcharged drain downstream of and nearest to the most downstream drain of the plurality of consecutive drains.

10 Also, the processor may be arranged to identify a failure in a drain when the received information indicates that only one drain of a plurality of consecutive drains is surcharged.

The processor may be arranged to identify an action for rectifying the identified failure. 15 Once the processor has identified the failure the apparatus will provide a suitable response for rectifying that failure.

The action for rectifying the identified failure may comprise sending an alert including information regarding the failure to an identified technician via the communication unit.

20

According to a third aspect of the present invention a computer readable medium is provided. The computer readable medium comprises computer readable code operable, in use, to instruct a computer to perform any of the method steps disclosed above.

25 The processor may be arranged to record historical data and use it to determine if there is a real event such as a failure, or if the sensor has failed to operate.

The processor may be arranged to determine if a sensor has failed.

30 Also disclosed is apparatus for sensing the level of sewage in a conduit, the apparatus comprising sensing means and communicating means, wherein:

the sensing means is fitted to a conduit to sense the level of sewage in the conduit substantially at a legal boundary of the building or of land on which it is

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built, the conduit arranged to communicate sewage from the building to a public sewer across the legal boundary,

the communicating means is arranged to communicate with the sensing means 5 to determine whether the level of sewage in the conduit has at least reached a predetermined level and, responsive to this, to communicate information indicative of this to a remote location.

By fitting the sensing means such that the level of sewage is sensed at the legal 10 boundary, it is possible to determine, in the event of a blockage or surcharge, who is responsible for clearing that blockage. For example, if a blockage occurs, but the level of sewage is low at the boundary as sensed by the sensing means, then the blockage must be inside the boundary such that responsibility for clearing the blockage lies with the owner of the private property. If, however, a blockage occurs and the level of 15 sewage is high at the boundary, the blockage must be outside the boundary such that responsibility does not lie with the owner. By monitoring at this point, it is therefore possible for the sewerage company to know of a problem for which it is responsible long before the customer is affected, or if the customer reports a problem, for the sewerage company to determine whether or not it is responsible without the delay and 20 cost of sending someone out to investigate.

The legal boundary may be the boundary of land on which the building is sited.

The predetermined level may be chosen such that it is a level at which sewage still 25 flows in the pipe, but that is an unusually high level. The predetermined level may be substantially 50%; it may be substantially 65%, which is usually the maximum "designed for" level; it may be 75%, which is indicative of the maximum "designed for" level being exceeded and therefore indicative that there may be a blockage.

30 The sensing means may be fitted to the conduit substantially at the legal boundary. The sensing means may project into the conduit. The sensor means may comprise a sensor. The sensor may project into the conduit. This projection may be substantially at the legal boundary. The sensor may be responsive to contact or lack-of-contact with liquid to produce a signal. In an embodiment, the sensor means is operable to generate a signal

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indicative of the sensor not being in contact with liquid. The sensor may be positioned above half-way from the bottom of the conduit. The sensor may be positioned between 65% and 75% from the bottom of the conduit. The sensor may be angled to project into the conduit at an oblique angle. The oblique angle may be between 35 degrees and 55 5 degrees from the horizontal. The oblique angle may be 45 degrees from the horizontal. The sensor may project substantially towards the centre of the conduit.

The sensor may be orientated with respect to the conduit as described above, but instead located within a chamber constructed on the conduit at the same orientation.

10

The communicating means may communicate with the sensing means under the control of control means. The control means may be arranged periodically to operate the sensing means such that the sensing means generates a signal that is received by the control means indicative of the level of sewage in the conduit having reached and/or not

15 having reached the predetermined level. In an embodiment, the sensing means generates a signal indicative of the level of sewage in the conduit not having reached the predetermined level (i.e. an indication is provided that the drain is not full or part full and is therefore serviceable). This allows the apparatus to monitor serviceability and is also fail-safe.

20

The communicating means may communicate with the remote location under the control of the control means. In response to receiving a signal from the sensing means indicative of the level of sewage having at least reached the predetermined level and/or in response to receiving no signal from the sensing means when operated, the control

25 means may be arranged to wait for a period of time, which may be a predetermined period, before controlling the communicating means to communicate with the remote location and/or before operating the sensing means again. This is to guard against false alarms being generated.

30 The apparatus may further comprise a source of stand-alone electrical power. The source may comprise energy storage means such as, for example, a battery. The source may comprise electricity generating means such as, for example, means for generating electricity from solar radiation, such as photo-voltaic cells. The source could be any other electrical source such as power from the building.

9

The control means and/or the communicating means may be housed remote from the conduit. The control means and/or the communicating means may be housed above ground and optionally adjacent the sensing means. The control means and/or the 5 communicating means may be housed substantially at or just below ground level.

The conduit may be a lateral drain.

The remote location may be a private company or government agency with 10 responsibility for maintaining the public sewer.

Although referred to as a "public sewer", and indeed nearly all sewers are now publicly owned in England and Wales, the sewer may of course be owned and/or maintained by a private company in other countries. This may be the same private company as that 15 with which the remote location is associated. "Public sewer" is therefore used herein in a figurative sense to refer to a main conduit receiving sewage from a plurality of buildings.

Other aspects of the invention are envisaged in which the sensing means are not fitted 20 to sense the level of sewage at the legal boundary of private property. The sensing means may be fitted to sense the level of sewage at other points in a drainage system. Other aspects are also envisaged in which the level or absence of matter other than sewage is determined. In certain aspects the level of a liquid may be determined.

25 Also disclosed is a method of operating the above-described apparatus for sensing the level of sewage in a conduit. The method may comprise one, or all of the steps described below as being features of example embodiments. The method may comprise any combination of those steps.

30 The method may comprise the steps of the control means periodically operating the sensing means to ascertain whether or not the level of sewage has at least reached the predetermined level and then communicating information indicative of this to the remote location. The information indicative of this may be in the form of an alarm. The alarm may be in the form of an alarm message. The alarm message may be

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communicated wirelessly, for example by SMS text message. The information indicative of this may be in the form of data indicating whether or not the level of sewage has at least reached the predetermined level and the time of day at which this was ascertained. The data may be communicated wirelessly, for example by a data 5 connection over a mobile phone network.

The method may comprise the step of periodically operating the sensing means to ascertain whether or not the level of sewage has at least reached the predetermined level and, on ascertaining that it has reached the predetermined level, communicating 10 information indicative of this, and, optionally, on ascertaining that it has not reached the predetermined level operating the sensing means again to check this after a predetermined delay. The sensing means may be operated repeated in this way during a predetermined period. The sensing means may not then be operated again until the next periodic period of operation.

15

The method may comprise the control means resending the information upon not receiving confirmation information indicative that the information communicated by the control means has been received at the remote location. The method may comprise communicating to the remote location that the confirmation information has not been 20 received. This may be by sending an alarm message.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the invention and examples related to the invention will now 25 be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 shows an example of part of a sewerage system;

30 Figure 2 shows part of a sewerage system with apparatus fitted for sensing the level of sewage in a conduit thereof, the apparatus shown schematically;

Figure 3 is a section through the conduit and through sensing means of the apparatus;

Figure 4 is a flow chart showing a method, at least part of which is carried out by the apparatus;

Figure 5 provides a schematic plan view of a sewerage system to which a drain as 5 shown in Figure 1 connects; and

Figure 6 is a flow chart showing an alternative method, at least part of which is carried out by the apparatus.

10 DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS

A system for sensing a failure, such as a blockage, in a drain of a sewerage system will now be described with reference to Figure 2, which shows sensing apparatus 10 for sensing the level of sewage in a drain. The sensing apparatus is made up of three main 15 functional elements: sensing means in the form of a sensor 100, control means in the form of electronic circuitry including a microprocessor 20, and communicating means in the form of communications circuitry 30, including an aerial, arranged to communicate over a wireless cellular telephone communications network that operates in accordance with GSM and that is able to send data over such a network using, in this 20 embodiment, GPRS. In other embodiments, other forms of wireless communication are used. Each of the main functional elements will now be described in more detail, after the following description of Figure 2.

As can be seen from Figure 2, a drain 40 runs from a private property to a public sewer 25 50. The end of the drain 40 that is within the private property - that is, the end that is not connected to the public sewer 50 - is connected to receive waste water and other sewage from a house (not shown) that forms part of the private property. Within the boundary of the private property, a private inspection chamber 60 that runs from ground level down to the drain 40 and that connects to the drain is provided. Also provided 30 within the boundary of the private property is an outside gulley 70 that also runs from ground level to connect to the drain 40. The inspection chamber 60 and the gulley 70 are both away from the property boundary.

12

The sensing apparatus 10 is arranged with the sensor 100 mounted to the drain. The microprocessor 20 and the communications circuitry 30 are mounted together in a housing 25 that is buried above the drain and just below ground level. The sensor 100 is connected to the microprocessor 20 by a sensor cable 110.

5

The sensor 100 will now be described further with reference to Figure 3. The drain 40 is shown in Figure 3 in cross section, with the bottom of Figure 3 corresponding to the invert (bottom) of the drain 40 when buried in the ground. The cross section is taken at the boundary of the private property. The drain 40 is provided with a hole 42 through its 10 wall at about 45 degrees above the horizontal such that the sensor is between 65% and 75% of the diameter of the pipe above the invert of the pipe. The sensor 100 is mounted in a generally cylindrical sensor housing 120 with a sensing end of the sensor 100 projecting through one end of the sensor housing 120. That one end of the housing 120 is provided with a stepped shoulder portion to terminate in a spigot. The spigotted end 15 of the sensor housing 120 is mounted in (or, in other embodiments, covering) the hole 42 and secured in place by adhesive. The adhesive also provides a seal around the sensor housing 120, between the sensor housing 120 and the drain 40. The arrangement is such that the sensing end of the sensor 100 projects into the drain 40 when mounted in this way. Care should however be taken to avoid the sensor projecting so far into the 20 drain 40 that it collects solid matter in the drain and contributes to a blockage forming. The sensor cable 110, which is connected to the sensor 100, exits the sensor housing 120 at the other end of the housing. The sensor cable 110 is surrounded by and protected by a flexible cable duct 112 secured to the spigott.

25 In an alternative embodiment of the invention the sensor is connected directly to the drain 40, and as such the sensor housing 120 is not required.

By positioning the hole 42 at 45 degrees above the horizontal, the sensing end of the sensor 100 is positioned to correspond to a level of 75% of the height of the inside of 30 the drain 40. Drains 40 such as that shown in the Figures are usually designed such that the maximum anticipated flow in the drain results in a level of approximately 65% of the internal height of the drain. Placing the sensor in a position that corresponds to a 75% level therefore allows the sensor to sense a level above this designed-for maximum, indicating that the drain 40 is, or risks becoming, blocked.

13

In the present embodiment, the sensor 100 is an opto-electric "dry" sensor, meaning it provides a signal when it is not wet. The sensor 100 is selected to operate with low voltage and current, and with an ingression protection rating, such that it is intrinsically 5 safe and so suitable for use in the drain 50. In the present embodiment, the sensor operates with a voltage of 5VDC or less and a current of less than 40mA

As will be apparent from Figure 2, the sensor 100 is mounted to the drain 40 at the boundary of the private property. The reasons for this will become clear below.

10

With reference again to Figure 2, as mentioned above, the housing 25 contains the microprocessor 20 and the communications circuitry 30. The microprocessor 20 is in the form of an application-specific integrated circuit (ASIC) that is programmed and operable to carry out the steps of the method 200 described below and with reference to 15 Figure 4. The communications circuitry is arranged and operable under the control of the microprocessor 20 to send information about the apparatus wirelessly over a cellular telephone network.

With reference to Figure 4, the method starts with a series of steps that are one-off 20 commissioning steps. These steps would involve programming the relevant information into firmware (not shown) of the device. At step 202, the Duty Manager's GSM phone number is entered. The Duty Manager's phone number is the number to which the sensing apparatus 10 will send SMS text messages or radio messages containing alarms generated by the apparatus if the normal operating regime fails.

25

At step 204, the sensor activation frequency in minutes is set. As will become clear, this is the period between successive activations of the sensor 100.

At step 206 the sensor active period in minutes is set. This is the duration of operation 30 of the sensor 100 in each activation.

At step 208, the re-check frequency is set in minutes. This is the amount of time for which the method waits after a potential alarm condition before performing the recheck described below in step 244.

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At step 210, the time of day at which data is sent from the sensing apparatus 10 is set.

At step 212, the first activation of the apparatus is initiated. At step 214, the sensor 100 5 is operated and any signal provided therefrom are monitored and stored to the memory of the sensing apparatus 10, together with the time of day of that signal. The sensor is operated for the period previously set in step 206.

In an alternative embodiment, any of steps 202 to 212 may be pre-programmed into 10 firmware or alternatively included in a separate control system.

After operation of the sensor 10, the method proceeds to step 216 at which a query is asked as to whether or not it is the time of day set in step 210 as being that at which data is sent from the sensing apparatus 10.

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If the answer is "yes", the method proceeds to step 218 at which the stored data is sent using a data connection over the mobile phone network to a remote data storage and processing system location at the sewerage company with responsibility for the relevant sewer. The method then looks for confirmation at step 220 that the text message has 20 been received (by the receipt of a confirmatory text message back). If this is not received, the method goes through a loop of two further attempts to send the data in a text message. After three failed attempts, the method sends in an SMS text message to the Duty Manager's phone number entered at step 202 a text message at step 222 to the effect that the data upload failed. A visit to the site of the apparatus may then be made 25 to carry out maintenance of the apparatus and to recover manually data from the apparatus. Other alarms could be activated to notify other people and systems, as appropriate for the specific application.

If a confirmatory message is received by the sensing apparatus 10 at step 220, the 30 method logs that this is the case at step 224, before returning back to step 216, via a step that deletes data that is more than 100 hours old.

At step 216, if it is determined that it is not the time of day at which data is uploaded, the method proceeds to step 226 and awaits the next activation of the sensor 100. This

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is done by looping through a query at step 228 which asks whether the number of minutes set as the activation frequency in step 204 have elapsed since the end of the last activation of the sensor 100. If that number of minutes has not elapsed, the method sleeps until that number of minutes has elapsed, and then moves from step 228 to step 5 230.

At step 230, the method activates the sensor 100 for the number of minutes set in step 206 and proceeds to step 232. At step 232, it is ascertained whether or not the sensor 100 is "not dry" at any time during the sensing period (which is the duration of 10 activation of the sensor 100). If it is determined that the sensor is indeed not dry during the sensing period, the method moves to step 234 in which it is ascertained whether or not the sensor is not dry for the full duration of the check period. If it is determined that the sensor 100 is not dry for the full sensing period, the method proceeds to step 236 at which the output from the sensor is checked again, i.e. re-checked, after the period of 15 time set as the recheck frequency in step 208. The re-check takes place in step 238; if it is determined then that the sensor is dry, the method goes back to the query block of step 228; if it is determined that the sensor is not dry, the method moves to step 240 at which the method generates an alarm condition indicative of the sewer being surcharged. Subsequent steps are then followed; these will be described below.

20

If it is determined at step 234 that the sensor was not not-dry for the full sensing period (i.e. it was dry for at least some of the time), the method moves to step 242 and sets a re-check time as the previous check time plus 15 minutes (in other embodiments, this 15 minute period is configurable in the initial commissioning). At step 244, the re-25 check is carried out at the appropriate time. If, on carrying out that re-check at step 246, the sensor is not dry, the method moves to step 240 referred to above and generates the alarm condition indicative of the sewer being surcharged. The steps subsequent to step 240 will now be described.

30 From step 240, the method proceeds to step 248 at which an alarm is sent by text message to the Duty Manager. This is followed by step 250 at which the last 24 hours of data collected from the sensor and stored in the apparatus are uploaded, in the same way as is done in step 218. The method then waits for a confirmation by text message at step 252 that both the alarm and the data have been safely received. Steps 254 and 256

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add a re-send loop to the method such that two further attempts are made to resend the data if acknowledgement of safe receipt is not received, before proceedings to step 258 at which a text message is sent to the Duty Manager to the effect that the transmission has failed. A visit to the site of the apparatus may then be made to carry out 5 maintenance of the apparatus in response to the alarm(s) and to recover manually data from the apparatus. Should the acknowledgement of safe receipt be received at step 252, the method proceeds to step 224 described above.

An alternative system for sensing a failure, such as a blockage, in a sewerage system 10 shall now be described. This system differs from the system described above in that this system is arranged to detect a failure in both the public sewer and the drains feeding the public sewer. The means for detecting a failure within the drains is substantially the same as the above-described system and as such only those features of the alternative system that differ from the previously described system shall be described.

15

Service failures may occur in the public sewer due to blockage, siltation, collapse, hydraulic overload, or other restriction. Hereinafter, reference shall be made primarily with reference to the situation of a blockage in the public sewer, however, it will be appreciated that the system described herein is also applicable to other service failures 20 in the public sewer.

Figure 5 shows a schematic plan view of the sewerage system of Figure 1 along the length of the public sewer 50. A number of drains 40, 140, 240, 340, 440 feed into the public sewer 50. Each drain 40, 140, 240, 340, 440 takes the form of the drain 40 25 described above and therefore includes a sensing apparatus equivalent to the sensing apparatus 10 of drain 40. Each sensing apparatus is arranged to communicate with the remote data storage and processing system.

The remote data storage and processing system includes a memory for storing data, a 30 processor for processing the stored data, and a communication unit for transmitting and receiving data. The memory stores information relating to each of the sensing apparatuses, such as a sensing apparatus ID, and the geographical location of the sensing circuitry and the associated drain inspection chamber. Also stored in memory is information regarding sewage levels sent from the sensing apparatuses. The memory

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also stores the level of the sensor above the sewer or above ordnance datum, along with the geographical position of the sensor, for example in terms of longitude and latitude information. The processor may be arranged to make various determinations regarding where there has been a failure within the sewerage system based on the information 5 stored in memory. These determinations performed by the processor are discussed in more detail below. The communication unit is not only arranged for communicating with the sensing circuitry, but is also arranged to send communication messages, by text message or radio for example, to personnel who are identified as suitable for rectifying failures within the sewerage system.

10

When a sensing apparatus associated with a drain determines that the associated drain is surcharged, the sensing apparatus uploads stored data regarding sewage levels to the remote data storage and processing system. The remote data storage and processing system then checks its data storage to determine if any neighbouring drains are 15 surcharged.

If it is determined by the remote data storage and processing system that no other drains are surcharged then the processor determines that the drain is blocked between the public sewer and the sensing apparatus, i.e. in the public lateral drain or public property 20 portion of the drain. The duty manager or other personnel can then be informed by the system, e.g. via text message, and attempt to rectify the failure.

If a surcharge is detected at one or more other neighbouring drains then it is determined by the remote data storage and processing system that the blockage is within the public 25 sewer. The location of the blockage is then approximated from the information received from the drains in which a blockage is detected and the neighbouring drains, as discussed below.

Figure 5 shows a blockage in the public sewer at point X, with the sewage flowing from 30 point A towards point B along the public sewer. Shortly after the blockage X occurs and the public sewer begins to become surcharged, typically the drains 240, 340 and 440, which are upstream of the blockage X, will also start to become surcharged. The drains 240, 340, and 440 will most likely, but not necessarily, become surcharged

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sequentially from the drain nearest to the blockage, drain 240, to the drain furthest from the blockage, drain 440.

Once the blockage occurs, the remote data storage and processing system will identify 5 the blockages sequentially from data received from the respective sensing apparatuses. Since a sequential surcharging of consecutive or neighbouring drains is indicative of a blockage in the public sewer, the remote data storage and processing system will therefore then identify that there is a blockage in the public sewer. In addition, from the information received from the neighbouring drains the system will deduce that the 10 approximate location of the blockage is downstream of the most downstream surcharged drain of the consecutive surcharged drains and upstream of a drain not surcharged which is downstream of and nearest to the most downstream of the consecutive surcharged drains. Hence, in the example shown in Figure 5, drains 240, 340, and 440 are determined to be surcharged, while drains 40 and 140 are not 15 surcharged and as such the remote data storage and processing system is able to determine that the blockage is or is likely to be in the public sewer between the drain 140 and drain 240,

Once a blockage in the public sewer is diagnosed, a response such as an alarm for a 20 blockage in individual drains need not be raised, and instead a response for a blockage in the public sewer is raised. It is noted that different responses may be provided dependent upon where the blockage is identified as being likely to be located. Consequently, an appropriate technician can be called out to deal with the blockage. Hence, responses or alarms for failures in individual drains may not be issued until a 25 sufficient period of time has passed to enable the remote data storage and processing system to determine whether the absence of a dry signal from a particular drain may be the result of a service failure in the public sewer. The system discussed in accordance with Figure 5 therefore differs from the first described system in that an alarm signal is not sent to the duty manager as soon as surcharging is detected in a drain. Instead, the 30 relevant data is uploaded from the sensing apparatus associated with the surcharged drain to the remote data storage and processing system and this data is then analysed along with data received from neighbouring drains, and information stored regarding drains from which no data has been received, i.e. drains that are not surcharged. It is

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only once it is determined where the failure has occurred in the sewerage system that action is taken to rectify the failure of the system.

The remote data storage and processing system is also arranged to differentiate between 5 different types of public sewer failure. When there is a failure of the public sewer due to a blockage or siltation the liquid levels in the public sewer and drains upstream of the blockage or siltation may slowly and repeatedly fluctuate up and down around a mean point which gradually gets higher as not only the severity of the blockage increases, but also as more sewage enters the sewerage system. Eventually, the drains will become 10 completely surcharged and the sensing apparatuses will remain wet. The remote data storage and processing system is therefore arranged to detect these fluctuations in sewage levels in consecutive drains in order to detect or rule out a failure in the public sewer due to blockage or siltation as early as possible.

15 In contrast, failure of the public sewer by hydraulic overload, for example as a result of a storm, is likely to result in many drains becoming surcharged almost simultaneously, and levels in those drains will rise to a maximum level very quickly. The sewage levels will then slowly fall as the excess liquid in the sewerage system manages to pass through the sewerage system. Hence, the signals sent from the sensing apparatuses in 20 the case of a hydraulic overload are notably different compared to signals sent as a result of a blockage. Hence, the remote data storage and processing system is capable of differentiating between different causes of service failure within both the public sewer and sewer system as a whole. Consequently, a suitable response to the service failure can be actioned.

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The above-described system for detecting failures within a sewerage system is advantageous because the type of failure within the sewerage system can be quickly identified. Furthermore, in the case of blockages within the sewerage system, the location of the blockage can be swiftly identified. Consequently, the specific location 30 of a blockage can be identified by lifting a minimum number of manhole covers near to the identified location of the blockage. The system is also advantageous because no additional sensors need to be installed within the sewerage system, and instead information collected by the sensing apparatuses associated with the respective drains

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feeding the public sewer are utilised for determining service failures within the public sewer.

It will be appreciated that the system for detecting failure in the whole sewerage system 5 could use any suitable type of detection apparatus in each of the drains associated with public sewer. In particular, multiple level sensing apparatuses could be used in order to provide more accurate information to the remote data storage and processing system. Sensors providing more accurate information would allow for faster detection of failures within a sewerage system.

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Figure 6 is a flow chart illustrative of an alternative method for detecting failures in a sewerage system. The method described herein and illustrated in Figure 6 is arranged to be programmed into the microprocessor 20 in the form of an application specific integrated circuit (ASIC), as described with respect to Figure 4. In particular, Figure 6 ] 5 provides a flow chart of a real-time method for monitoring sensors. It will be appreciated that the method of Figure 6 is arranged to be an alternative to the method shown by the flow-chart of Figure 4. Only those features of the method that differ to those previously described will now be described.

20 Real-time monitoring is achieved in accordance with the system associated with Figure 6 by having a sensor control circuit that provides a periodic and regular output signal regarding the status of the drain to which it is connected.

The operation of the sensor control circuit associated with the sensor shall firstly be 25 described.

At step 301 certain operational parameters required by the sensor control circuit are initially set prior to deployment of the control circuit. For example, the sensor activation frequency is set in minutes at step 302, as is the sensor active period at step 30 303. Furthermore, at step 304 a checking process is established within the sensor control circuit in order to re-check the frequency. This check may take place after a predetermined number of minutes.

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Once the sensor control circuit is deployed it is switched on by an installation engineer at step 305. The sensor control circuit is activated by means of, for example, a magnetic switch, or other suitable method.

5 The sensor control circuit is then ready to function and commence sensing as indicated at step 306. At step 307 a determination is carried out as to whether the sensor is dry or not. If the sensor is dry, a dry monitoring relay circuit is activated (step 308). The dry monitoring relay circuit is communicatively coupled to the remote data storage and processing system, which may also be referred to as the data storage and management 10 system. Hence, a monitoring signal indicative of the sensor being dry is sent from the sensor control unit to the data storage and management system. The signal is transferred almost instantaneously after it is determined if the sensor is dry. The monitoring circuit is then maintained in an activated state until 'y' minutes have elapsed (step 309) and then the sensor control circuit is put into sleep mode (step 310). The 15 period "y" is kept to a minimum in order to conserve battery power and maximise battery life. At step 311 the monitoring circuit is re-activated so that sensing begins again.

When the sensor is determined not to be dry, i.e. to be wet, the sensor control circuit is 20 put into sleep mode for z minutes (Step 312), and then after z minutes the sensor control circuit is woken up (step 313). The absence of monitoring signal indicating that the sensor is dry is therefore indicative of the fact that either the sensor is wet or that the sensor is not functioning correctly.

25 A data communication apparatus is provided between the sensor control circuit and the data storage and management system, and acts as a communications interface. The data communication apparatus is arranged to constantly monitor the sensor status. The data communication apparatus is a radio system such as a GPRS/3G mobile communication system in which the sensor status is constantly monitored by means of a mobile 30 communications SIM-based device. The data communication apparatus therefore receives information from the sensor control circuit and sends the information on to the data storage and management system (step 314).

The operation of the data storage and processing system shall now be described.

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Firstly, at step 319 the duty managers GSM phone number is set. The duty manager may be any appropriately qualified person.

5 If the sensor is determined to be dry (step 315) then data indicative of this determination is stored in a data store of the data storage and processing apparatus (step 316).

If the sensor is determined to be not dry then the data storage and processing system 10 generates a system alarm which will indicate that either a part of the sewerage system is surcharged or the sensor has failed (step 318). A check is then carried out to determine whether another of the many sensor control circuits to which the data storage and processing system is coupled is surcharged or faulty (step 320). It is unlikely that two sensors will fail simultaneously and so two nearby sensors giving the same indication is 15 likely to indicate the true state of the conduit.

If no other alarms have been activated due to another surcharged drain or faulty sensor then an alarm is generated for a member of control staff to deal with what looks to be either a blocked drain or faulty sensor (step 321). In addition, the work job will be 20 generated and programmed within a Work Management System (step 322), which will enable the alarm to be monitored, and signed off once dealt with.

If other alarms are detected then the matter will be escalated to the duty manager with details regarding the number of alarms in the last 24 hours (step 323). At this point the 25 system can approximate the position of a blockage in the sewerage system as has been previously discussed. Again, the new work job will be programmed within the Work Management System.

The data store of the data storage and processing system generates a periodic system 30 report (step 324), which details data stored in the data store over a certain period. This report can then be viewed and analysed by control staff. From this analysis it can be determined if site work is required (step 325). If work is required then a job is set up with the Work Management System (step 322). If work is not required then the report is disregarded (step 326).

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The real-time process provides a simplified means for monitoring the status of one or more sensor control circuits associated with drain sensors. The real-time nature of the process means that problems within a sewerage system can be identified quickly and 5 therefore rectified more effectively.

The various methods described above may be implemented by a computer program. The computer program may include computer code arranged to instruct a computer to perform the functions of one or more of the various methods described above. The 10 computer program and/or the code for performing such methods may be provided to an apparatus, such as a computer, on a computer readable medium. The computer readable medium could be, for example, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, or a propagation medium for data transmission, for example for downloading the code over the Internet. Non-limiting examples of a 15 physical computer readable medium include semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disc, and an optical disk, such as a CD-ROM, CD-R/W or DVD.

20 An apparatus such as a computer may be configured in accordance with such computer code to perform one or more processes in accordance with the various methods discussed above.

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Claims

1. A method for sensing a failure in a sewerage system having a sewer and a plurality of drains that feed sewage to the sewer, the method comprising:

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receiving information from a plurality of sensing apparatuses associated with respective drains, the received information indicative of sewage levels within the respective drains, and

10 identifying a failure within the sewerage system in accordance with the received information.

2. The method according to claim 1, wherein a failure within the sewerage system is identified when the received information is indicative of at least one respective drain

15 being surcharged.

3. The method according to claim 1 or claim 2, wherein a failure in the sewer is identified when the received information indicates that a plurality of consecutive drains of the plurality of drains are surcharged.

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4. The method according to claim 3, further comprising identifying that the failure in the sewer is a result of a blockage or siltation in the sewer when the plurality of consecutive drains become surcharged sequentially from the most downstream drain to the most upstream drain of the plurality of consecutive drains.

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5. The method according to claim 3, further comprising identifying that the failure in the sewer is a result of hydraulic overloading when the information indicates that the plurality of consecutive drains have become surcharged substantially simultaneously.

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6. The method according to any one of claims 3 to 5, further comprising locating the failure of the sewer as being between the most downstream drain of the plurality of consecutive drains and a non-surcharged drain nearest to and downstream of the most downstream drain of the plurality of consecutive drains.

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7. The method according to claim 1 or claim 2, further comprising identifying a failure in a drain when the received information indicates that only one drain of a plurality of consecutive drains is surcharged.

8. The method according to any one of claims 1 to 7, further comprising identifying an action for rectifying the identified failure.

9. The method according to claim 8, wherein the action for rectifying the identified failure comprises sending an alert including information regarding the failure to an identified technician.

10. Apparatus for sensing a failure in a sewerage system having a sewer and a plurality of drains that feed the sewer, the apparatus arranged to perform the method of any one of claims 1 to 9.

11. A computer readable medium comprising computer readable code operable, in use, to instruct a computer to perform the method of any one of claim 1 to 9.

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