Patent Description:
A combined sewer system is a sewage collection system which combines waste water (sewage) and storm water (rain water) to direct the combined water, generally, to a waste water treatment plant.

A waste water treatment plant generally has a capacity limitation on the volume of water which may be captured for treatment. During for example heavy rain the volume of storm water in the combined system may be relatively high compared to the normal volume of water flowing in the system. If the volume of water flowing in the combined sewer exceeds the capacity of the waste water treatment plant the combined water may be output by a combined sewer overflow (CSO). Often the combined water may flow from the overflow to a water source such as a river, lake or into the sea. The overflow is generally a trough or aperture in a pipe, the aperture being arranged above the general water level in the pipe, if the water exceeds the level of the overflow it flows via the trough/aperture.

The monitoring of such overflow events is important for municipal water services as an overflow may lead to untreated waste water entering a water source in the environment, leading to pollution etc. Monitoring may be a regulatory or legal requirement on a municipal water service. Traditionally the monitoring of such overflow events occurs via estimation based on precipitation levels.

Some overflow sensor systems are known in the art. Previously float based sensor systems, or hydrostatic pressure sensors may be used to measure an overflow event. However, these are generally installed for a period of time, compared to known precipitation records and then estimation is subsequently used to determine if a combined sewer overflow event has occurred. This is because the systems generally consume substantial amounts of energy and it may be costly and difficult to maintain such sensors as they are in contact with inherently dirty water, both existing sensor systems have a capacity to attract debris and thus lead to incorrect and misleading information. Additionally, sensor systems generally require external power sources or have a short lifespan due to necessarily high power consumption over long durations arising from constant monitoring and transmission of water levels. Detailed monitoring with battery powered systems has previously not been possible due to the energy requirements of the sensor and communication systems.

<CIT> relates to a monitoring system including a monitoring device for sewers. The monitoring device is placed in manhole covers and communicates with a remote monitoring station.

Improved sensing systems are necessary to ensure that combined sewer overflow events are monitored.

Accordingly, the present invention preferably seeks to mitigate, alleviate or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination and solves at least the above mentioned problems by providing a system as defined in claim <NUM>.

A method in a combined sewer detection system is also provided, as defined in claim <NUM>.

Further advantageous embodiments are disclosed in the appended and dependent patent claims.

These and other aspects, features and advantages of which the invention is capable will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which.

<FIG> shows a combined sewer overflow system <NUM> for monitoring overflow events in a combined sewer <NUM>. The system <NUM> comprises a first sensor <NUM> for measuring the level of water in a combined sewer <NUM>. The sensor <NUM> is a non-contact sensor and is positioned at a height above the overflow outlet <NUM> of the combined sewer. The sensor <NUM> is connected to a controller <NUM> which receives an output from the sensor <NUM>, the output representing the height of water in the combined sewer <NUM>. The controller <NUM> is provided with a transmission module <NUM> for transmitting received sensor data to a data collection system <NUM>. The system <NUM> further comprises an on-board power source <NUM> for providing power to the controller <NUM> and the sensor <NUM>.

During operation the controller <NUM> is adapted to control the operation of the sensor <NUM>. The controller <NUM> is adapted to enable and disable the sensor periodically to detect the level of water in the combined sewer <NUM>. The controller <NUM> is generally initially in a coarse detection mode. When the controller <NUM> is in a coarse detection mode the interval i.e., period of time between enabling the sensor <NUM> to detect the height of water in the combined sewer <NUM> is t(detection)coarse. If the controller <NUM> receives data from the sensor <NUM> indicating that the height of water in the combined sewer <NUM> is above a predetermined threshold then the controller is adapted to enter an overflow mode.

In an overflow mode the system is in an enhanced operation mode. In an overflow mode the system <NUM> may be adapted such that the period between enabling the sensor <NUM> to detect the height of water in the combined sewer is t(detection)overflow. t(detection)overflow is shorter than t(detection)coarse.

When the controller <NUM> is in the coarse detection mode it uses minimal power. When the controller <NUM> is in an overflow mode it uses substantially more power than in the coarse detection mode. The different detecting periods, different transmission periods, and/or different sensor activation, depending on the level of water in the system enable the system <NUM> to consume substantially less energy than existing systems which, for example, sample at the same rate, and therein increases the lifespan and reduces maintenance costs for the system <NUM>.

The increase in lifespan is especially relevant in a combined sewer <NUM> as accessing the combined sewer <NUM> may be difficult, time consuming and costly. For example, the combined sewer <NUM> may be underground and only accessible to authorised personal. The less maintenance the system <NUM> requires substantially increases the ease of use of the system for a municipality/user.

The controller <NUM> is adapted to transmit sensor data via the transmission module <NUM>. The controller <NUM> transmits sensor data to the data collection system <NUM>. The sensor data sent from the controller <NUM> is received at the data collection system <NUM>. The controller <NUM> is adapted to adjust the duration between sending events based on the level of water detected in the combined sewer system <NUM>.

In the coarse transmission mode the controller <NUM> may transmit data at an interval of t(transmission)coarse. In the overflow transmission mode the controller <NUM> transmits data at an interval of t(transmission)overflow. t(transmission)coarse is substantially greater than t(transmission)overflow. That is, in an overflow mode the system <NUM>, and in particular the controller <NUM>, detects and transmits data at an increased rate compared to in the coarse mode, when the system <NUM> has detected that there is no overflow event occurring. The transmission of data is power intensive and therefore by sending data at a different rate/interval depending on the water level in the combined sewer <NUM> the system <NUM> saves power and increases maintenance intervals.

In an overflow mode, the overflow transmission mode, and the overflow detection mode may be advantageously combined. That is, the system <NUM> detects at an increased rate, and transmits data at an increased rate compared to in a coarse detection/transmission mode.

The system <NUM> may comprise additional sensors <NUM>, <NUM> adapted to measure water or environmental parameters in the combined sewer <NUM>, the parameter being distinct from the height of the water. For example, the system <NUM> may comprise a temperature sensor <NUM> to measure the temperature of the water in the combined sewer <NUM>, and/or the ambient temperature in the combined sewer <NUM>. The system may comprise a flow rate sensor <NUM> to measure the flow rate of water in the combined sewer <NUM>. The flow rate sensor may be a contact or non-contact flow rate sensor. Each of the additional sensors, or a combination of sensors, may be activated on entering the overflow mode.

On entering the overflow mode, the system <NUM> may activate at least one additional sensor <NUM>, <NUM>. The sensor, on activation, detects a parameter of the water distinct from the height of the water in the combined sewer <NUM>, the sensor data detected may thereafter be transmitted via the controller <NUM>. The transmission may occur at an interval of t(transmission)coarse of t(detection)overflow depending on whether the system <NUM> is transmitting in an overflow or coarse transmission mode.

In an overflow mode, the system <NUM> may each of: detect at a rate of t t(detection)overflow; activate an additional sensor <NUM>,<NUM> to detect a parameter of the water distinct from the water height; transmit detected height sensor data, and/or the sensor data from the additional sensor at a rate of t(transmission)overflow. In an overflow mode the system <NUM> may advantageously combine several, or all the above. For example, the height of water in the combined sewer <NUM> may be detected at a rate of t(detection)overflow, the at least one additional sensor <NUM>, <NUM> may be activated, and the sensor data may be transmitted at a rate of t(transmission)overflow.

<FIG> show the water level Hw during three separate time twenty-four hour periods. <FIG> also show sensing events and transmission events during the three separate time periods depending on the level of water in the combined sewer system <NUM>.

In <FIG> the water level Hw is maintained below the predetermined threshold height Ho. Each sensing event <NUM> is marked with a cross. Each sensing event indicates that the controller <NUM> is woken from a sleep mode, detects the height of water in the combined sewer <NUM>, and stores the detected height in a storage module <NUM> on the controller. Each transmission event <NUM>, is marked with an arrow. During each transmission event <NUM> the controller may be woken from a sleep mode, and sends data via the transmission module <NUM>. As can be seen in <FIG> the controller <NUM> transmits data once during a twenty-four hour period, i.e., t(transmission)coarse = <NUM> hours. As the controller <NUM> detects that the height of water in the combined sewer overflow does not exceed in the threshold Ho, it is maintained in a coarse detection mode throughout the twenty-four hour period of <FIG>.

<FIG> shows the water level during another twenty-four hour period. In <FIG> the water level exceeds the predetermined threshold height Ho. Each sensing event <NUM> is marked with a cross. Each sensing event <NUM> indicates that the controller <NUM> is woken from a sleep mode, detects the height of water in the combined sewer <NUM>, and stores the detected height in a storage module <NUM> on the controller. Each transmission event <NUM>, is marked with an arrow. During each transmission event 600a-c the controller may be woken from a sleep mode, and sends data via the transmission module <NUM>. As can be seen the controller <NUM> detects that the height has exceeded the threshold at time Ti. The height of water exceeding the threshold may be designated an overflow event. Once the controller <NUM> has detected that the height of the water in the combined sewer overflow has exceeded the threshold Ho the controller <NUM> enters the overflow mode. In the overflow mode the controller <NUM> detects the height of water in the combined sewer <NUM> more frequently than in the coarse detection mode. That is, it detects once every period, t(detection)overflow. The controller <NUM> is also adapted to transmit the detected height via the transmission module <NUM> more frequently than in the coarse detection mode. In <FIG> a first transmission event 600a occurs at T<NUM>. The first transmission event 600a may occur before any further sensing events. At the transmission events 600a-c the controller <NUM> transmits the stored data corresponding to the height of the water in the combined sewer <NUM>. In the transmission event 600a the transmitted data may comprise height data corresponding to the period when the water height was below the threshold level Ho and when the water height was above the threshold level Ho. A second transmission event 600b occurs after a period of t(transmission)overflow. At the second transmission event 600b the controller <NUM> transmits stored data corresponding to the height of the water in the combined sewer <NUM> stored since the previous transmission event 600a. At the first sensing event after the height of water in the combined sewer <NUM> drops below the threshold Ho this drop is detected by the sensor <NUM> and controller <NUM>. The controller <NUM> may thereafter return to the coarse measurement mode and detect the height once every period t(detection)coarse. After the intervening transmission period of t(transmission)overflow, the controller <NUM> transmits via the transmission module <NUM> the stored data corresponding to the height in the combined sewer <NUM>. The controller <NUM> then returns to the coarse transmission mode. A subsequent transmission 600c may occur after t(transmission)coarse which in <FIG> is at the completion of the twenty-four hour period. The subsequent transmission 600c comprises the stored data corresponding to the height of water in the combined sewer <NUM> when the water was above and below the threshold Ho.

<FIG> shows the water level in a combined sewer <NUM> during a third twenty-four hour period. In the period shown in <FIG> the water level increases above the threshold Ho for a short duration. The short overflow duration in <FIG> is less than the period t(transmission)overflow. Each sensing event <NUM> indicates that the controller <NUM> is woken from a sleep mode, detects the height of water in the combined sewer <NUM>, and stores the detected height in a storage module <NUM> on the controller. Each transmission event <NUM>, is marked with an arrow. During each transmission event <NUM> the controller may be woken from a sleep mode, and sends data via the transmission module <NUM>. As can be seen the controller <NUM> detects that the height has exceeded the threshold at time Ti. The height of water exceeding the threshold may be called an overflow event. Once the controller <NUM> has detected that the height of the water in the combined sewer overflow has exceeded the threshold Ho the controller <NUM> enters the overflow mode. In the overflow mode the controller <NUM> detects the height of water in the combined sewer <NUM> more frequently than in the coarse detection mode. That is, it detects once every period, t(detection)overflow. The controller <NUM> is also adapted to transmit the detected height via the transmission module <NUM> more frequently than in the coarse detection mode. In <FIG> a first transmission event 600a occurs after Ti. At the transmission events 600a-b the controller <NUM> transmits the stored data corresponding to the height of the water in the combined sewer <NUM>. In the transmission event 600a the transmitted data may comprise height data corresponding to the period when the water height was below the threshold level Ho and when the water height was above the threshold level Ho. The controller <NUM>, detects via the sensor <NUM> that the height of water in the combined sewer is below the threshold at sensing event 500d. In <FIG> 500d is shown to correspond to when the water level drops below the threshold Ho. However, as each detection event occurs at a predetermined rate, after the specified interval, there may be a delay corresponding to some portion of the interval t(detection)overflow before this detection occurs. The controller <NUM> may thereafter transmit the stored data corresponding to the height of the water in the combined sewer <NUM>. As the water level has dropped below the threshold Ho the controller enters the coarse detection and transmission mode and the subsequent transmission event 600b occurs after the interval t(transmission)coarse.

As can be noted in the above descriptions the transmission interval, and the sensing interval is dependent on the level of water in the combined sewer <NUM>. Via altering the sensing and transmission intervals based on the height of water in the combined sewer a reduced total energy consumption during overflow and non-overflow periods is achieved. The system <NUM> therein has lower energy consumption needs compared to a system which transmits are regular intervals regardless of the level of water in the combined sewer <NUM>. Clearly this is especially important for a system which has on-board energy storage and provision, e.g., battery power. This enables the system <NUM> to be installed in a combined sewer <NUM> and left, substantially maintenance free for periods of up to several years. For example, the system may be left without requiring replacement of a battery for up to <NUM> years.

It may be noted that generally the system <NUM> will be in the course measurement, and course transmission modes, as generally there is no overflow via the combined sewer outlet <NUM>. In most combined sewer <NUM> installations the combined sewer will not overflow unless relatively high precipitation occurs. Therefore, in a normal state, the system <NUM> consumes minimal power.

The sensor <NUM> may be any non-contact sensor for detecting the level of a fluid, for example an acoustic sensor, such as an ultrasonic sensor; a radar such as a pulsed coherent radar (PCR), and/or a laser sensor. An ultrasonic sensor is suitable due to its low power consumption and effectiveness in measuring the distance from the sensor <NUM> to the top of the fluid in the combined sewer <NUM>. A pulsed coherent radar (PCR) is an especially suitable sensor due to its low power consumption and that the radar signal is generally not affected by ambient light or noise. Furthermore, a PCR-type sensor may be fully encapsulated meaning it is mechanically protected from the ambient conditions in the sewer.

The sensor <NUM> is positioned at a height above the overflow outlet of the combined sewer <NUM>. Once in position in the combined sewer <NUM> the sensor <NUM> may be calibrated such that the predetermined threshold Ho is established for the particular installation.

The threshold Ho is implemented as a range and not a single distinct value, depending on the previous detected level. For example, Ho is a first height if the previous detected heights have been below the threshold Ho, however, if the system is in an overflow mode, then Ho is adjusted to a second height such that it is less than the first height. Via this technique the system is less likely to oscillate between coarse detection and overflow modes.

The controller <NUM> is preferably implemented by any commercially available MCU ("Micro Controller Unit"), MPU ("Micro Processor Unit"), CPU ("Central Processing Unit"), DSP ("Digital Signal Processor") or any other electronic programmable logic device. The controller <NUM> is configured to read instructions from memory and execute these instructions to control the operation of the system <NUM>. The memory may be implemented using any commonly known technology for computer-readable memories such as ROM, RAM, SRAM, DRAM, CMOS, FLASH, DDR, SDRAM or some other memory technology. The memory is used for various purposes by the controller <NUM>, one of them being for storing application data and program instructions for various software modules in the controller <NUM>. The software modules include a real-time operating system.

The transmission module <NUM> may be a radio frequency interface adapted to communicate via a low-power long-range radio technology such as LPWAN including, for example, LoRa, SigFox; NB-IoT, and/or LTE-M. The transmission module <NUM> may be adapted to communicate via e.g., GSM, W-CDMA/HSPA, UTRAN, long-range <NUM> or the like, however, these higher-power communication technologies are less suitable as they increase power consumption and therefore reduce battery life and the duration between maintenance periods. The transmission module <NUM> may be adapted to communicate with a second transmission module <NUM> in the vicinity of the first via a mesh-network. One of the first or second transmission modules <NUM> may thereafter transmit the sensor data to the data collection system <NUM>. Such a mesh-network arrangement may enable reduced energy consumption as each system <NUM> need not send sensor data over the long-range network.

<FIG> shows a flowchart describing an overflow monitoring and transmission process performed with the system <NUM>. The system <NUM> below is described as starting in the coarse detection mode and the coarse transmission mode.

Action <NUM>: the controller <NUM> wakes and enables the sensor <NUM> to detect the level of water in the combined sewer <NUM>.

Action <NUM>: the controller <NUM> receives sensor data from the sensor <NUM> corresponding to the height of water in the combined sewer <NUM>. The value is stored in the storage module <NUM>.

Action <NUM>: the controller <NUM> compares the received sensor data to the predetermined threshold Ho. The controller <NUM> determines if the height of the water in the combined sewer <NUM> is greater than the threshold Ho. If the height of water is above the threshold height the system <NUM> proceeds to Action <NUM>. If the height of water is below the threshold Ho then the system proceeds to Action <NUM>.

Action <NUM>: the system <NUM> enters the overflow mode. A flowchart representing the process performed by the system <NUM> during an overflow event, i.e., when the system is in overflow mode is shown in <FIG>.

Action <NUM>: the controller <NUM> determines if transmission of data is due. Transmission occurs in the interval t(transmission)coarse. If transmission is due then the controller <NUM> actives the transmission module <NUM> and transmits the data representing the measured height of water for the period t(transmission)coarse.

Action <NUM>: the system sleeps for a period of t(detection)coarse.

As noted, <FIG> shows a flowchart representing the process performed by the system during an overflow event, i.e., when the system is in an overflow mode.

Action <NUM>: the controller <NUM> activates the transmission module <NUM> and transmits the data representing the measured height of water.

Action <NUM>: the controller <NUM> wakes and enables the sensor <NUM> to detect the level of water in the combined sewer <NUM>,.

The controller <NUM> continues to detect the level of water in the combined sewer <NUM> and receive the data at an interval of t(detection)overflow. The controller <NUM> compares the received sensor data to the predetermined threshold Ho. The controller <NUM> determines if the height of the water in the combined sewer <NUM> is greater than the threshold Ho. If the height of water is above the threshold height the system <NUM> is maintained in the overflow mode. If the height of water is below the threshold Ho then the system proceeds to returns to the coarse detection mode, numbered Action <NUM>.

Action <NUM>: in parallel with the detection of water levels i.e., not necessarily subsequent to Action <NUM>, the controller <NUM> actives the transmission module <NUM> every interval t(transmission)overflow for transmission of the detected water levels for the period t(transmission)overflow.

Furthermore, the controller <NUM>, may activate an additional sensor <NUM>, <NUM> for detecting a water parameter distinct from the height of the water. The sensor data from the additional sensor <NUM>, <NUM> may be transmitted by the transmission module as described above.

The transmission and detection intervals above have been described in general terms. Typical values for t(detection)coarse may be from <NUM> minutes to <NUM> hour, such as <NUM> mins to <NUM> mins, whilst typical values of t(detection)overflow may be from <NUM> seconds to <NUM> mins, such as from <NUM> to <NUM> mins. Typical values of t(transmission)coarse may be from <NUM> hours to <NUM> hours. Typical values of t(transmission)overflow may be from <NUM> to <NUM> hour, for example, <NUM> mins to <NUM> mins. Furthermore, in some instances, in the coarse detection and/or coarse transmission modes the detection/transmission of data may occur at a scheduled time rather than after a given interval. For example, transmission of data may occur at midnight or noon etc, rather than after a set interval when no overflow event has been detected.

The sensor data may enable improved estimation of the volume of water which overflows via the overflow outlet of the combined sewer <NUM>. Previous systems using for example, a float sensor which floats on or under the surface of the water in a combined sewer would indicate the start of an overflow event, when the water level is above the predetermined threshold, and the end of an overflow event, when the water level is below the predetermined threshold. The volume of water which flows via the outlet could then be determined via the duration of the overflow event. The present system <NUM> enables the measurement of the height of water during the overflow event.

The sensor data is encrypted prior to transmission via the transmission module <NUM>. The sensor data is encrypted via the controller <NUM>. The sensor data represents the height of the water in the combined sewer but may not necessarily be a value in meters. As would be understood to a skilled person the sensor data may be raw sensor values corresponding to a height, but which are first converted to a height in e.g., metres after being received at the data collection system <NUM>. With an acoustic sensor as described herein the measured sensor data is for example, generally represents a distance of the measured fluid from the sensor <NUM>. The sensor <NUM> is installed in a combined sewer <NUM> at a known height with respect to the overflow outlet <NUM>, the distance from the sensor <NUM> corresponds to a height of water in the combined sewer <NUM>.

Furthermore, the threshold Ho may correspond to the height of the overflow outlet, or it may correspond to a height slightly below the overflow outlet, such that the controller enters the overflow detection and/or transmission modes when the water reaches a level in the vicinity of the overflow outlet <NUM> of the combined sewer <NUM>. The threshold Ho need not correspond exactly to the height of the opening of the overflow outlet <NUM>.

As described above, the system <NUM> may be located in a combined sewer <NUM>. For example, the controller <NUM>, the sensor <NUM>, the transmission module <NUM>, the on-board power source <NUM>, and the storage module <NUM> may be located in a combined sewer <NUM>. The transmission module <NUM> may therefore able to transmit data through the walls, coverings etc. of the combined sewer <NUM>.

Some embodiments may be represented as a non-transitory software product stored in a machine-readable medium (also referred to as a computer-readable medium, a processor-readable medium, or a computer usable medium having a computer readable program code embodied therein). The machine-readable medium may be any suitable tangible medium including a magnetic, optical, or electrical storage medium including a diskette, compact disk read only memory (CD-ROM), digital versatile disc read only memory (DVD-ROM) memory device (volatile or non-volatile), or similar storage mechanism. The machine-readable medium may contain various sets of instructions, code sequences, configuration information, or other data, which, when executed, cause a processor to perform steps in a method according to one or more of the described embodiments. The skilled person appreciates that other instructions and operations necessary to implement the described embodiments may also be stored on the machine-readable medium. Software running from the machine -readable medium may interface with circuitry, i.e., in the controller to perform the described tasks.

Although, the present invention has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims.

Claim 1:
A system (<NUM>) for detecting an overflow event in a combined sewer (<NUM>) comprising:
- a sensor (<NUM>) for detecting the level of water in the combined sewer (<NUM>), the sensor (<NUM>) being a non-contact level sensor positioned at a height above an overflow outlet (<NUM>) of the combined sewer (<NUM>),
- a controller (<NUM>) adapted to receive sensor data from the sensor (<NUM>),
- a transmission module (<NUM>) adapted to transmit sensor data to a data collection system (<NUM>),
- an on-board power source (<NUM>) for providing power to the sensor (<NUM>), the controller (<NUM>) and the transmission module (<NUM>); and,
wherein the system (<NUM>) is configured to operate in two modes, a coarse detection and transmission mode, and an overflow detection and transmission mode; and, wherein, in the coarse detection mode the system (<NUM>) is configured to detect the level of water in the combined sewer (<NUM>) at an interval of t(detection)coarse, and, wherein the system is configured to operate in a coarse transmission mode wherein in the coarse transmission mode sensor data representing the level of water in the combined sewer (<NUM>) is transmitted at an interval of t(transmission)coarse, and, wherein, in the overflow detection and transmission mode the system (<NUM>) is configured to:
(i) detect the level of water in the combined sewer (<NUM>) at an interval of t(detection)overflow, wherein t(detection)overflow is less than t(detection)coarse, and,
(ii) operate in an overflow transmission mode wherein data representing the level of water in the combined sewer (<NUM>) is transmitted at an interval of t(transmission)overflow, wherein t(transmission)overflow is less than t(transmission)coarse;
and, wherein the system (<NUM>) is adapted to enter the overflow detection and transmission mode if the level of the water in the combined sewer (<NUM>) exceeds a predetermined threshold Ho, corresponding to a first level, and wherein when the system is in the overflow detection and transmission mode, the system is adapted to enter the coarse detection and transmission mode if the level of the water in the combined sewer (<NUM>) below falls below a threshold corresponding to a second level, which is less than the first level.