When a sewer reaches its flow capacity, uncontrolled spills into the surrounding environment may occur. This is why utilities across Australia are near real time monitoring sewer levels and alarming at critical thresholds. The following is an article prepared by Paul Hart and Graeme Jones from Metasphere and Colin Murphy from Pulsar Process Measurement.
Many water utilities have Key Performance Indicators (KPIs) around minimising the risk of sewer blockage and uncontrolled discharges, which can cause health hazards and disruption to the community.
Proactive water utilities are opting to monitor and manage their high risk blockage sites using a combination of Metasphere Point Colour range of battery powered Remote Telemetry Units (RTUs) and Pulsar dBi Ultrasonic Level Sensors.
When combined with Metasphere’s Bureau service, ‘Palette’, an online data visualisation and management platform, they combine to create an effective, near real time, decision making tool for water utilities and government agencies.
Projects are underway with major water utilities in New South Wales, Queensland and Victoria using the above combination of technology.
This article details the benefits of this proactive monitoring approach, the technology adopted and why it was chosen.
The problem
Sewer networks have a finite capacity, which is often reduced through blockages. When a sewer reaches its flow capacity, uncontrolled spills into the surrounding environment may occur.
This creates environmental and community health hazards and disruption, and the responsible utility is likely to be in breach of Key Performance Indicators (KPIs) and possibly fined.
The solution
Near real time monitoring of sewer levels, and alarming at critical thresholds, is one solution being adopted by water utilities across Australia.
The practical nature of sewer level monitoring: confined space environment, lack of mains power, tendency for ragging, and potentially toxic gaseous environment (many water utilities designate their sewer networks as intrinsically safe environments) poses a number of technical challenges.
A number of major water utilities have adopted the following combination of technology and software to enable sewer level monitoring, data visualisation and management:
- Metasphere Point Colour Remote Telemetry Units (RTUs)
- Pulsar dBi HART Ultrasonic Level Transducer
- ‘Palette’ – Metasphere’s Web Based Data Visualisation and Management Platform.
A typical sewer level monitoring installation is shown in Plate 1 below.
Metasphere Point Colour RTUs
Metasphere’s Point Colour Range includes three battery powered RTUs: Point Green, Point Orange and Point Blue, of which the Point Orange and Blue are appropriate choices for a sewer level monitoring application.
The principle difference between the Point Orange and Point Blue RTUs is that the Point Blue is IECEx Type 0 accredited and therefore suitable for deployment in sewer level networks that have been designated intrinsically safe.
Key technical features of the Point Orange and Point Blue RTU’s include:
Point Orange RTU
- 3G Tri-band modem (850, 900 & 2100 MHz)
- Multiple protocols supported: DNP3, Medina, FTP
- DNP3: Level 2, 3 and parts of 4 compliant
- IP68 up to four metres for four days
- Five real time monitoring sensors
- Software configurable I/O: AI, Cl and Dl
- Up to four Passive Voltage inputs, two Active Loops inputs and five digital inputs
- Flexible I/O configuration
- RS232, RS485 and SDI-12 serial communications
- 5+ years battery life
- Provides remote configuration and upgrading of firmware
- Dynamic trending and dial in capability
- Internal immersion sensor
- Automatic switchable internal/external antenna
- Auto detection and switching to an external power source
- Rapid installation with integrated bracket.
Point Blue RTU
Point Blue provides one additional significant feature over the Point Orange:
- IECEx approved intrinsically safe
- ExII 1G Ex ia IIB T4 Ga (-20°C ≤ Ta ≤ +50°C)
The Point Blue’s IECEx accreditation makes it ideal for use by utilities (monitoring sewer and trade waste), gas and energy providers (network performance and monitoring), agricultural applications (monitoring silo’s, storages), inline monitoring of gases and liquids.
Pulsar dBi HART Ultrasonic Level Transducer
The Pulsar dBi Ultrasonic is specifically designed for sewer level monitoring.
Features of the Pulsar dBi Ultrasonic include:
- IP68
- Low power consumption (36 micro Amps per hour when 4 measurements p/hr are taken)
- Rapid boot up (powers up intermittently doesn’t stay on continuously)
- Low power in, but high acoustic power output, to give robust and reliable readings in the most arduous of applications
- Superior masking of intrusions and narrow beam
- Drip shield to prevent condensation effecting the signal or optional submersible shields
- False echo recognition software for difficult and tight applications
- Range of level sensors is 3, 6, 10 and 15m and variable cable lengths from 5m – 30m
- ‘Palette’ Metasphere’s web based data visualisation and management platform.
‘Palette’ is Metasphere’s own data visualisation and management platform. It is an attractive option for clients that don’t have their own ‘top-end’ or want an alternative data visualisation and management platform.
Palette utilises ‘Medina’, which is Metasphere’s own data protocol.
Palette allows the utilities to monitor their assets at three levels:
- Network Overview
- Site View
- Outstation View.
Data trends, thresholds and alarms can be viewed and managed in near real time. RTUs can be configured remotely via Palette.
Typical Configuration
A typical application configuration during low flows is for the RTU to power up dBi every 15 minutes and take a level measurement, with the value being saved in RTU memory.
The RTU then dials into ‘Palette once a day and transfers’ and displays the level data.
The RTU does however report on exception. When a pre-set level threshold is exceeded an alarm is sent (via email or SMS) and the RTU can dynamically trend to take data readings at pre-set more frequent interval, every five or one minute for example.
The RTU can also be configured to dial in and transfer the data more frequently when in the ‘alarm’ state.
This allows the flow event to be captured and the RTU battery power is called upon when its most needed.
Most importantly it allows the end user, viewing the data to see if in near real time and manage their business accordingly.
Typical Challenges
The main challenges are in the accurate installation and setup of the monitoring equipment in often cramped environments, as demonstrated by Figure 1 above. Every installation is different.
Key challenges include:
- Access – pits located on or close to roads, or in busy thoroughfares (foot / cycle paths) complicate access and installation. Roads or paths may need to be closed or temporarily cordoned off to gain access. Night working may be required if main roads require closing. Vehicles or other obstructions may be located over the top of pits when the installation crew turn up to install
- Position of pit cover in relation to sewer – The pit cover may not (regularly isn’t) located directly over the sewer centre line (high flow / maximum depth point). To ensure the water level sensor is over the sewer centre line varying types of brackets (for mounting the sensor) will be required. As each site is different it is difficult to standardise on the brackets required and often the particular challenges of each site aren’t known until the pit cover is lifted for the first time. Ensuring the sensor is properly positioned may require it to be some distance from the RTU, introducing an undesirable length of cabling that may add to ragging
- Health and Safety – the safe working and return home of all involved should be everyone’s No. 1 priority. Installing sewer level monitoring can involve working at height, in a confined space environment, in and around water, and in gaseous environments. Pre planning, prior site knowledge (through SWMS and Site Risk Assessments), and a well trained and equipped installation team are all crucial to preventing health and safety risks from materialising.
Key Benefits
Key benefits reported by utilities that have adopted the above sewer level monitoring approach include:
Reduced cost due to:
- Removing the need for mains power
- Removing the need for street furniture, i.e. turrets, as all equipment can be placed in the sewer network below ground
- Quick installation time
- Fewer fines due to quick event response through alarming and alerting system
- Relatively little ongoing operation and maintenance requirements.
Reduced water utility staff health and safety risk due to:
- Fewer site visits due to relatively little ongoing operation and maintenance requirements
- Fewer confined space entry events.
There is an increasing need for effective sewer level monitoring to help prevent uncontrolled overflows from sewer networks. Monitoring helps prevent blockages and overflows, preventing raw sewage entering the community and preventing utilities from being fined.
Metasphere’s Point Orange RTU, coupled with a Pulsar dBi ultrasonic level sensor and ‘Palette’ are proving to be an effective monitoring and data management solution.
This partner content is brought to you by Metasphere. For more information, visit www.metasphere.co.uk.
