waste water monitoring

Increasing the value of wastewater network monitoring

Increasing the value of wastewater network monitoring

Innovation is the key to delivering ever-increasing performance

Asset owners around the world are looking for innovative ways to deliver on the challenge of increasing wastewater network performance targets. With improved technology and the ability to handle large amounts of data, it’s become significantly easier to monitor flow and depth patterns, and highlight issues within a network that trigger a maintenance response prior to a flooding or pollution incident occuring

waste water monitoring

Radar level and IoT telemetry device from Metasphere (Sense Level, ART Sewer)
Wastewater monitoring can generate a return on investment when they prevent flooding and pollution incidents.

Of course, there is no point in installing monitors for the sake of it, they should be positioned so that they have the greatest value. Having monitors in areas that don’t generate a return on investment is not prudent, therefore knowledge of current system performance and planning is required to determine the optimal locations that will provide a positive return when installed in locations that are most likely to prevent flooding or pollution incidents. 

The most important part of the puzzle in locating monitors is to understand the characteristics of the most common failures within the network; blockages. A previous UKWIR project  identified the following: 

  • 20% of blockages reported over a year are repeats at property level and this increases to between 40% and 60% when analysed at the postcode level. 
  • The proportion of repeats increases to 30% and 70% at a property and postcode resolution respectively when there are 5 years of data available. 
  • Approximately 50% of postcodes and 4% of properties have suffered 1 or more blockages over a 9-year period, this reduces to 23% of postcodes and 1.2% of properties suffering repeat blockages over the same period. 

 

Picture of sewer blockage

Analysis of historic blockage data indicates blockages repeat at the same location over time.

This analysis shows repeat blockages happen at the same location and that if monitors are located correctly, they can be effective in preventing major incidents. 

 The report also identified the most common causes of blockages: high density of interceptors, high densities of FOG (fats. oils & grease) generating properties, older properties, terraced / high rise properties, small diameter sewers and lower affluence. 

 This suggests that taking remedial action such as removing interceptors, root cutting, repairing structural defects and educating customers about the use of FOGs and wet wipes would mitigate the probability of repeat blockages. Fixing the root cause will prevent having to constantly reattend to carry out blockage clearance maintenance, which causes inconvenience for the customers and increases operational costs. 

 In a perfect world asset owners would repair and replace all the defects in a wastewater network. The reality of course is there is no bottomless pit of money for this activity and funding will continue to be challenged given the current focus on the affordability of utility bills.  

Person calculating his expenses

The affordability challenge associated with utility bills means there will never be sufficient funding to repair all defects on the network.

Repairs are not always practical or cost effective

 This is where asset management comes in and provides us with the capability to effectively balance the cost, risk and performance triangle depending on the objectives of the asset owner. For example, In the case of complicated wastewater networks that may run beneath buildings with a flat gradient that increases the blockage probability, then the implementation of a proactive cleansing programme is likely the best approach to balance cost, risk and performance.  The use of monitoring in these situations allows the proactive maintenance costs to be optimised and ensure cleansing is only completed when it is required. 

Cost, risk and performance triangle

Asset Management provides the capability to balance the cost, risk and performance triangle to deliver the asset owner’s objectives.

Alternatively, the installation of a monitor where roots have been identified or where a partial collapse has occurred is unlikely to balance the triangle correctly. It will likely be more efficient to mitigate the root cause (e.g. cut out the roots or repair the collapse) compared to monitoring the location.  

Data is key to making informed decisions

The ability to adapt the correct balance of cost, risk and performance for each scenario is based on having the right data available to understand the root cause of a flooding or pollution location.  Using CCTV pipe inspection data provides the ability to understand the root cause and enables monitors to be installed at locations where they can generate the greatest Return on Investment (ROI).  The historic challenges with CCTV pipe inspection data have been its cost (e.g. it is not cost-effective to survey the entire network) and the ability to provide the outputs in a format that allows good investment decisions. 

 VAPAR uniquely combines Artificial Intelligence, the latest software capability and human input, reducing the cost of CCTV pipe inspections and making the outputs more accessible to decision-makers. Reducing the cost of CCTV pipe inspections makes it more economical to either complete CCTV pipe inspections prior to installing a monitor or use existing inspection data as part of the monitoring decision-making process. A great example of making the CCTV pipe inspection data more accessible is the visualisation of the survey results via a GIS, where the defect locations can be understood relative to the proposed monitor location on the pipe network. 

Pipe network and defects seen on GIS using VAPAR

VAPAR’s capability to visualise CCTV pipe inspection data allows monitoring locations to be identified that will deliver the greatest ROI.

Conclusion

It is fundamental for Asset Managers to look at alternate and innovative ways of managing pipe networks if they are to deliver the increasingly challenging financial and performance targets. The use of network monitoring provides one of these innovative ways, however, it will not provide a ‘Silver Bullet’ in isolation.  The use of VAPAR alongside monitoring will allow CCTV pipe inspection data to inform the decision-making process on where to install monitors. Ultimately this will balance cost, risk and performance and ensure the return on investment from monitoring is realised. 

Nathan Muggeridge - Author
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Local Sewer History Finds

Local Sewer History Finds

Keeping an eye out for local sewer history finds

Most major cities had their first sewer infrastructure constructed centuries ago. While much of the original networks are either long gone or buried deep underground, if you do a little research and keep your eyes open you’ll likely find some interesting structures that formed part of the original systems. In some cases, these will be decommissioned, others are still in services hundreds of years after they were built.

Sewer aqueduct spanning Johnstone's Creek (Annandale, Sydney)

Finding a piece of Sydney’s sewer history

Out on a recent morning jog in Annandale, I came across a sewer aqueduct that was partially enveloped by the canopy of a large fig tree. Reading the faded plaque on one of the concrete arch supports and reading up on its history, it was interesting to learn about the important role this structure played in the early Sydney sewer network.

The Johnstone's Creek Aqueduct

Designed by Prussian engineer William Baltzer and constructed by Carter, Gummow and Forest in 1896, the aqueduct contains 8 primary arches and has a total length of 281m. It was the first use of reinforced concrete for a large structure in Australia. This very new construction technique of the time was under patent and known as the Monier system. The historical significance of the Johnstone’s Creek aqueduct has led to it being listed on the NSW State Heritage Register.

 

Early example of reinforced concrete in Australia

Transporting sewage to Bondi

The separation of the Sydney’s combined stormwater and sewer pipework began in 1887, and by 1889 the Sydney sewer network had reached 140km of pipe and was servicing close to 25,000 properties across the inner city. With this flow discharging into the harbour, construction of more sustainable options had been underway for some time. Construction of the Bondi Ocean Outfall and Botany Sewage Farm was completed in 1889 and allowed for further expansion of Sydney’s sewer network. 

This included the Northern Main Sewer which would service the growing population in Annandale and Balmain and transport flow to a main line junction at the corner of Parramatta Rd and City Rd, then all the way through to Bondi. This extension required crossing both Johnstone’s Creek and White’s Creek with the construction of aqueducts the most suitable design option of the time.

 

Could reinforced concrete be trusted?

In the late 19th century, the idea of using concrete for such a large structure was not without detractors. The original Public Works Department design called for a brick arch construction and the submission for this new design and material had initially been rejected due to its experimental nature and unproven history. However, support from Robert Hickson (Under-Secretary for Public Works) was interested in trialling the use of reinforced concrete and what was an innovative idea at the time. The Monier design delivered spans that could be 50% larger than brick, and the total cost of the project was quoted as 20% cheaper – it received the go-ahead for construction after test arches were loaded to failure at Burwood with positive results.

Looking west from Glebe to Annandale showing construction of Johnstons Creek Sewer Aqueduct. (City of Sydney Archives)

The rest is history

It didn’t take long before the advantages of reinforced concrete led to a rapid increase in use for a wide range of structures. The first reinforced concrete water reservoir was built in Kiama just a few years later in 1899. The Annandale Aqueduct has certainly stood the test of time, it required only minor maintenance in its first 90 years of service – far exceeding the 3-year guarantee period. The flume was eventually plastic lined in the 1980s and the arches underwent repair and protection works in 1996. 

Still interested in more of the aqueduct’s history?
Well, there was some controversy!

Like any good historical story, the construction was not without controversy. A Royal Commission was held in 1896 and ran for over a year. It was based around accusations of favouritism, contract violations, and defective work. This was not assisted by the fact that at the time William Baltzer suggested the alternate design he was working as a draughtsman in Sewerage Construction Branch of the Public Works Department while also on retainer as an engineer for Carter, Gummow and Forest who were awarded the contract. Despite the large furore and public investigation, the final report fully exonerated Hickson, Baltzer and others involved. It even went as far as finding that some of the allegations appeared frivolous and not founded in truth. As difficult as this must have been for the engineers and others involved in the commission so soon after construction, it is the detailed record of the commission that has provided such informative history and detail about the project from inspection to completion. It was the commission proceedings themselves that meant this significant construction achievement become one of the best documented contracts of the era.

Extract from the Public Works Inquiry Commission

VAPAR.Solutions is designed to process and score video footage from a wide variety of camera systems, providing a single cloud-hosted location for all your inspection videos, images, reports and decisions.

About the Author Mark Lee