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
Enlight2786 (002)

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
MSCC5

Opportunities to improve the UK pipe inspection standard (MSCC5)

Opportunities to improve the UK pipe inspection standard (MSCC5)

MSCC5

Introduction

If you work within the UK water industry, you will be very aware of the MSCC5 (Manual of Sewer Condition Classification Fifth Edition). The first edition dates back nearly 40 years now, and in that time, many hundreds of thousands of miles of sewers and pipes by thousands of different contractors of all shapes and sizes have used the code to create a standardised output.

 

Is history holding back the future?

The Water Research Centre (WRC) first published MSCC back in 1980, and since then, other countries have adopted the idea behind a standard. This led to the creation of the European Standard  BS EN 13508-2:2003+A1:2011, which has allowed the different codes to use a common language. 

 

This alignment now presents a challenge with updating MSCC so it can keep pace with the technological changes. The need to align with the European Standard means many stakeholders will need to agree to any changes. However, there is a real need to update the standard, given that the current manual is still referring Cathode-Ray Tube (CRT) screens and their calibration. Is there anyone out there using these screens now? 

CATHODE RAY SCREEN

MSCC5 references the calibration of Cathode-Ray Tube screens. Does anyone else still use these screens?

The first opportunity to improve the standard is to consider what the future of pipe inspecting coding might look like and how MSCC can support the future. We feel that using AI and modern software techniques is the first step in modernising a sector that has not changed significantly in the last 40 years. 

car manufacturing with humans

Can the pipe inspection industry be modernised to deliver the benefits generated by the latest manufacturing plants?

How could we look at things differently?

So, what could a new coding standard look like in 2022 if we were designing it from scratch? If you look at computer software these days, it is a lot simpler than it used to be. Less is more now, and even the most complicated programmes have simple user interfaces to help speed up workflow and productivity. Gone are the days of needing to install desktop software and then updating it physically.

So how can this be applied to sewer surveying and classification, given that there are different types of users, from Water companies to small drainage contractors?

 

We need to think about why we are doing the survey and what is the result we want. The purpose of the standard is all about making an informed decision about investment in repair, maintenance, or renewal in line with its condition, serviceability, and budget available. Does the current coding standard meet the requirements? If yes, does it do it with simplicity in mind? This factor is essential when training people on how to code and survey? With so many codes and conditions to learn, this can extend training requirements and take years for operatives to gain all the experience needed to code the surveys to the exacting standards. Are contractors doing this, and is it possible to audit it accurately – probably not! 

 

By simplifying and determining the key elements that make up the investment decision, we could remove a lot of unnecessary work and time and use enhanced technology to fill in the gaps speeding up workflow and productivity and saving money. The delivery of this outcome could start with a single document containing the coding and scoring requirements. Currently, MSCC5 includes the codes, and the Sewer Risk Manual holds the scores to determine the condition grades that typically drive the investment need.

 

Coding observations

Do the current set of codes consider all likely defects on the network? Is coding of infiltration, H2S attack and Hydraulic overload accurate and in a way that informs decisions on the action necessary. We don’t currently have a condition grade that reflects the degree of infiltration associated with an asset.

 

Abandoned surveys require a comment in the remarks section to explain the root cause for the survey being abandoned. This approach is not helpful when you own a survey company and are looking to minimise the number of abandoned surveys and increase your productivity. How do you determine the value of providing the crews with longer cable lengths to minimise the number of ‘out of cable’ abandonments? In other countries, they have specific abandoned codes related to the defect before. For example, the Australian manual has ‘Survey Abandoned Collapsed Pipe’.

pipe inspection abandoned

How many abandoned surveys occur due to insufficient cable length? 

 Open and displaced joints always cause much debate and can be confusing 5-10% of diameter gets a score of 40, but 1.5 pipe wall thickness receives a score of 2. Typically, a pipe wall thickness equals 10% of the internal pipe diameter, so how can this be made more consistent?

Condition Assessments

We have a situation where we have two different types of condition assessment criteria in the UK. There are two scoring systems; the DRB Drain Repair book grades A, B & C (for domestic properties) and the SRM (Sewer Risk Management grades 1-5) on some software systems. Whilst they map against each other, it seems questionable to have two different approaches. It is essential to have accurate data to make informed decisions, and having one standard will make that accuracy more consistent. This further help simplify the training and reduces the costs for survey company owners.

 

Furthermore, is it also possible to be more scientific about the likelihood of further deterioration or collapse? Given that we have years of data, is it possible to develop a more accurate way of assessing risk on specific pipe lengths? Could this allow us to plan repair and maintenance more productively and head off issues at an earlier stage with a more cost-effective repair? We suspect the disparate data storage capability of the incumbent software applications for pipe inspection coding means this will be difficult. However, VAPAR’s central database of pipe condition assessments allows this type of data to be easily accessed and could be the key to unlocking a faster and more cost-effective solution to surveying and condition assessment.

Final thoughts

Technology plays a massive part in all our lives; whilst CCTV camera technology has advanced exponentially over the past ten years reporting systems have remained static. The traditional processes are still heavily manual and require extensive training and experience to keep the data collected consistently. But are we now at crossroads in terms of the old and the new?

VAPAR‘s AI platform is now able to generate MSCC5 compliant outputs. The development work to comply with MSCC5, plus the standards used in Australia, the United States and New Zealand, has provided us with a unique perspective.

VAPAR’s modern and unique capability to combine AI and human inputs to produce a fast and accurate output provides an opportunity to match the latest CCTV camera technology. Updating the MSCC standard is one part of the puzzle that will significantly improve how we do things for the customers using piped networks.

vapar platform ai and human

Vapar provides the capability to combine AI and human inputs to produce a fast and accurate output and provides an opportunity to match the capability of the latest CCTV camera technology.

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manhole cover in slovokia

Basics of Sewer Manholes

Basics of Sewer Manholes

Picture of sewer manhole

What are manholes?

Sewer manholes or also called maintenance holes are formal access points within the sewer pipe network that provide maintenance teams a chance to get access to maintain the sewer pipe network. They can come in many different shapes and sizes depending on how deep they go into the ground and what the surrounding ground conditions are like.

Why do you need manholes?

Once a blockage or a break in the sewer pipe is confirmed through a CCTV inspection, maintenance teams need to get access to remedy the issue. Without the presence of manholes, any remediation would be complicated and expensive.

Where can you find manholes?

The spacing of the manholes depends on a couple of factors. If a sewer pipe is running in a straight line in an area where access is not an issue, then they are usually placed every 80-100 metres (260-330 feet) along a sewer pipe. This spacing is determined by the practical length of water jetting equipment to reach the full length of pipe, regardless of whether the water jetting was done from the upstream manhole, or the downstream manhole.

That being said, manholes can also be built at shorter or longer lengths. For example, if the pipe needs to have bends in it, the design engineer might want to install extra manholes to account for the risk of blockage at the change point in the flow of sewage.

Manholes can also be placed within the network at irregular locations when the pipe network runs under a highly urbanised area. Placing manholes in the middle of roads, or in the middle of someone’s property is not advisable.

There are serious safety issues with placing manholes too close to live roads and having a manhole under a concrete floor slab doesn’t really serve anyone either. For this reason, the configuration of the network and the spacing of manholes might vary to account for the above ground infrastructure.

Drain spotting

You can identify the presence of manholes by the manhole covers on roads, footpaths and even in parks. The manhole covers themselves can come in many different shapes and sizes also, although most are round. They are usually made of metal to withstand the weight of heavy vehicles.

There is a great #drainspotting hashtag that you can browse to see what others have contributed from all over the world. Perhaps on your travels, you might feel compelled to contribute some interesting manhole designs and locations and help educate others on the weird and wonderful world of our underground sewer networks.

sewer points
About the author
IN-R Drone

Sewer Camera – An explanation of the different types of camera hardware

Sewer Camera – An explanation of the different types of camera hardware

The inspection of sewer and stormwater networks is commonly completed using a camera that records video footage from the inside of underground pipes also called the sewer camera. The photos and videos collected during a pipe inspection can be used to assign a condition grade to pipes through the identification of structural and service defects. Councils, municipalities, and water authorities use these condition grades to prioritise pipe maintenance (e.g., clearing roots and debris) and repair (e.g., patches and lining). 

Access to pipes is usually obtained through maintenance holes or pits which can be located within roads, kerbs, public space, and private property.

A variety of different camera equipment is available to record video footage for defect analysis and scoring. Common sewer camera types include:

Crawler Cameras

Crawler cameras are robust remotely controlled inspection robots that traverse through a pipe on wheels. They typically have a strong light source to illuminate the inside of the pipe and are connected via a cable to a vehicle on the surface that supplies power and transmits the video back to a vehicle computer for recording. The robot is controlled by an operator on the surface who directs the crawler’s progress through live vision fed back to their computer monitor. They can adjust for speed and direction, and often have the ability to pan, tilt and zoom the camera lens; leading to the term PTZ camera (they are also called tractor cameras in some regions). Crawler cameras are the most common type used for pipe network inspections throughout the world.

Fixed Zoom Cameras

Fixed zoom, or pole cameras, do not need to travel along the pipe to collect video footage. They consist of a fixed high-definition camera head attached to a pole that is lowered from the surface to the base of the pipe at surface entry locations. Using a combination of strong zoom, focus adjustment, and lighting; a video is recorded as the camera zooms in and the field of vision extends through the pipe from chainage zero to the end of pipe or bend. With a combination of optical (20-40x) and digital zoom (10-15x) they provide a fast and robust way to collect a condition overview of a network.

Image of pole camera for sewers

Push Rod Cameras

House connection branches or sewer laterals present unique challenges when collecting condition footage or diagnosing a problem. Their small diameter and frequent bends mean the larger camera hardware is unable to enter and travel through these smaller lines (typically < 150mm diameter). Push rod cameras are designed for tough and tight conditions. Appearing as a coiled cable on a real with a slim camera head, they can be inserted and controlled manually with imagery fed back to a control unit. The use of skids is sometimes employed to keep the camera head and vision steady and centred.

Pushrod camera for sewers

Inspection Rafts

For large pipes that cover long distances, an inspection raft may be the only choice to collect imagery from within a pipe. These are often used for outfall tunnels where they can be sent downstream and caught with a hook or net at location that could be many kilometres further down the pipe. They are usually designed to stay upright and balanced.

Image of push raft camera for sewers

Drone Cameras

With rapid advancement in UAV technology, the industry has seen an increase in the use of drones for pipe inspection over the last few years. Drones have some distinct advantages in certain situations, including; large pipes with high flow where a crawler may not be able to enter and raft would traverse along the pipe too quickly, and longer pipe inspections where equipment weight or cable length is prohibitive. It will be interesting to see how this technology develops and if it becomes a more mainstream option for pipe networks.

IN-R Drone

Manhole / Maintenance Hole Cameras

There are now a variety of dedicated cameras available for collecting photos, videos, and 3D scans of the vertical shaft that leads down to the benching and pipe channel. In the past this has been completed by visual surface or confined space entry inspection, using a regular camera, or with a crawler as it is lowered down to complete the main pipe inspection. Newer camera technology has been specifically designed to collect more detailed information with much higher resolution than ever before.

Manhole maintenance camera

Jetter Nozzle Cameras

Jetters can be used by operators to clear sediment, obstructions, fats, oils, grease, and roots from pipes. Some hydro jetters on the market include a nozzle camera that can be used to help guide the camera through the pipe, locate specific issues and even steer into lateral pipes. The camera is also able to collect video footage following its cleaning run through the pipe to collect information on the effectiveness of the clean and provide an indication of the condition of the cleaned pipe.

Image of Jetter nozzle camera for sewers

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
bom national report image

BOM National Performance Report 2020-21: A wastewater snapshot

BOM National Performance Report 2020-21:

A wastewater snapshot

Each year the Australian Bureau of Meteorology releases the National Performance Report for urban water utilities, the 2020-21 report is available for public download here: http://www.bom.gov.au/water/npr/

This annual report aims to provide benchmarking of pricing and service quality for urban water utilities. The report is helpful for utilities to monitor annual trends within their own organisations, as well as look at whether their key metrics sit within the typical range in a broader national context. Utilities are grouped within four size categories (small, medium, large, major). This reflects that revenue base and population density can be a factor in both the cost required to provide water and sewer to customers as well as the level of service that is appropriate or sustainable.

Running to 128 pages, this is a comprehensive report that lists metrics across 166 categories from 86 utilities.  Dependent on your area of expertise or interest, there is interesting information for everyone.

Figure 1 – Australian utilities that submitted data for the 2020-21 report.

This article summary focuses on some of the key metrics that relate to gravity sewer mains and wastewater expenditure.

Sewer Main Breaks and Chokes

To enable comparative analysis, many of the metrics are reported as ‘per 100km of asset’, this is the case for ‘sewer mains breaks and chokes’.1 This last year has seen improvements for many locations with 57% of utilities reporting a decrease in breaks and chokes compared to the previous reporting year with Clarence Valley Council, Gippsland Water, and Gladstone Regional Council all seeing reductions of > 75%.

Utilities reporting the lowest instance of breaks and chokes in each utility group size is listed in the table below.

Table 1: Number of sewer mains breaks and chokes per 100 km (Indicator A14)

Utility Group Utility Value
Small (10,000 – 20,000 properties) Water Corporation – Geraldton (WA) 3.4
Medium (20,000 – 50,000 properties) Tweed Shire Council (NSW) 1
Large (50,000 – 100,000 properties) Gippsland Water (VIC) 1.5
Major (100,000+ properties) City of Gold Coast (QLD) 3.8

Major utilities saw the largest improvement for this metric. However, reductions were not the norm for small-sized utilities with the median increasing from 13.7/year to 15.6/year, and the average increasing from 25.3/year to 35.5/year.

Capital Expenditure per Property (Wastewater)

The report notes that the national median per property capital expenditure on wastewater services decreased by 11% from 2019-20 to 2020-21.

Utilities reporting the lowest wastewater expenditure per property in each utility group size is listed in the table below.

Table 2: Capital expenditure per property – wastewater (Indicator F29)

Utility Group Utility Value
Small (10,000 – 20,000 properties) Gympie Regional Council (QLD) $88.90
Medium (20,000 – 50,000 properties) Dubbo Regional Council (NSW) $3.65
Large (50,000 – 100,000 properties) Power and Water Corporation – Darwin (NT) $146.72
Major (100,000+ properties) City West Water Corporation (VIC) $143.57

Looking more closely at the data split by utility size, the average annual capital expenditure on wastewater is surprisingly similar across all utility sizes; in the region of $275 to $300 per property. The reported figures over the last decade do indicate that small and medium sized utilities may be investing less, on average, on wastewater infrastructure.

While there may be a variety of reasons for this, it will be of some concern if a trend of reduced investment is reflected in a similar reduction in wastewater service level KPIs (including sewer main breaks and chokes).

Figure 2 – Capital Wastewater Expenditure per Property

Despite the significant reported drop in per property wastewater expenditure over the last year (11%); the overall reported capital expenditure on wastewater has remained reasonably stable since 2017 at around $2.7 billion dollars per year – with a drop of 2.9% from 2019-20 to 2020-21 based on reported figures.

Figure 3 – Capital Wastewater Expenditure

Wastewater Operating Cost per Property

The report saw 66 of 86 utilities submit data on operating cost per property to supply wastewater services. The following utilities in each category reported operating their networks at the lowest cost:

Table 3: Wastewater operating cost per property (Indicator F14)

Utility Group Utility Value
Small (10,000 – 20,000 properties) City of Kalgoorlie-Boulder (NT) $168.96
Medium (20,000 – 50,000 properties) Rockhampton Regional Council (QLD) $294.59
Large (50,000 – 100,000 properties) Toowoomba Regional Council (QLD) $243.35
Major (100,000+ properties) South Australian Water Corporation (SA) $231.92

Residential Wastewater Bill

The cost to provide services is impacted by a wide range of factors, including but not limited to: age of assets, condition of assets, density of population, climate and topography. The table below lists the lowest residential wastewater bill in each category for the 20/21 period.

Table 4: Typical residential wastewater bill (Indicator P14)

Utility Group Utility Value
Small (10,000 – 20,000 properties) Armidale Regional Council (NSW) $465
Medium (20,000 – 50,000 properties) Lower Murray Water (VIC) $491.84
Large (50,000 – 100,000 properties) North East Region Water Corporation (VIC) $239.16
Major (100,000+ properties) City West Water Corporation (VIC) $347.92

The report indicates 57% of utilities had a reduction in the typical residential wastewater bill with Central Coast Council seeing the largest change (-24%). However nationally, the overall trend was only marginal (<1% decrease).

1 Wastewater mains breaks and chokes is intended to include:

  • Gravity sewer mains
  • Rising (pumped) mains
  • Low pressure mains
  • Vacuum system mains

It excludes:

  • Property connections
  • Treated effluent mains
  • Recycled water mains

It can be questioned whether failures on pumped rising mains and chokes within gravity sewer networks should fall under the same metric. While these asset types are intrinsically connected to form the majority of a sewer network, they operate under very different conditions and the mode and cause of failure are often quite distinct.


The information and data for this snapshot is sourced from Part A and Part B of the National performance report 2020–21: urban water utilities. It has been used under the Creative Commons Attribution 3.0 Australian License.

Found the article interesting? Check out our case studies here VAPAR case studies.

Heavy rain in a city

What are combined sewer overflows?

What are combined sewer overflows?

Image showing heavy rain on a city street

Early underground pipe systems, such as those in the United Kingdom, were built before separation of wastewater and rainwater pipes were common practice. These types of systems are called combined sewer systems.

A combined sewer overflow (CSO) event is the term used to describe when the capacity of the pipe to carry wastewater and rainwater at the same time is too much for the system to deal with, and the system overflows.

The consequence of CSO events can have a very serious impact on the environment and public health. For this reason, most water utilities have a regulator that monitors the performance of the water utilities to ensure pipe networks operate in a safe way. In the United Kingdom, this performance is monitored by the Environment Agency and regulated by OFWAT, who have recently started to undertake further investigations on the release of unpermitted sewage discharges into rivers and watercourses by some UK water companies. In Australia and the USA, the regional Environmental Protection Agency (EPA) organisations regulate and fine water authorities that are not operating in accordance with certain agreed criteria.

What causes a combined sewer overflow?

A combined sewer overflow (CSO) will most likely happen when both the wastewater and surface water experiences high flow at the same time. For example, when there is a lot of rainfall, and a lot of people at home flushing toilets, showering and cooking, placing greater demand on the sewer pipe network.

Picture showing difference in combined sewer overflow over dry and wet weather conditions
*POTW is a publicly owned treatment works
Source: U.S. Environmental Protection Agency, Washington, D.C. “Report to Congress: Impacts and Control of CSOs and SSOs.” Document No. EPA 833-R-04-001

There are lots of factors that can increase the likelihood and occurrence of a Combined Sewer Overflow, such as rainfall, population growth, and pipe condition. With increasing areas of land being paved, an increasingly urban population that each uses ~150L per person per day, and increased intensity of rainfall as the climate changes, the pipe networks built during the 19th century are unable to adapt.

What is the water industry doing about Combined Sewer Overflow?

Most combined sewer systems will be designed to overflow at a specific point in the network that will minimise damage and risk to the public and the environment. Because an overflow would usually occur when there is a high rainfall event, rainwater would dilute the raw sewerage, minimising (but not eliminating) the impact of the overflow. If the system was built without a designed overflow point, then whenever there are high flow events, sewerage may backflow to the nearest exit point, which may be directly into some unfortunate persons’ property.

To tackle this problem, some water utilities have been installing monitoring devices at commonly overflowing points in their pipe network. These devices send a signal to the water companies to let them know if the level of sewage in the pipe/structure is rising more than usual. If the level of sewerage reaches a certain value, an early warning alert is sent to the water company to let them know that an overflow may be imminent so that they can take action if required.

How can spills from combined sewer overflows be prevented?

Adding storage capacity to the network

In addition to some of the initiatives being undertaken by water companies described above, prevention of these types of overflows could also come adding storage capacity to the network. By increasing the capacity of the network to not only convey, but store (for a short period of time), it is possible to reduce the incidence of sewer overflows. This can come in the form of storage/detention tanks for both sewage and surface water.

Increase the treatment capacity of the network

Another option is to increase the treatment capacity of the network so that the sewage can be turned into good quality water faster, leaving more capacity in the network to convey sewage during times of high flow. A key element to the efficacy of treatment in the network to reduce CSO’s is to also make sure the upstream and downstream network from the overflow structure are in optimum condition. If these pipes fail or get blocked, then treatment capacity is greatly reduced.

A great example of increasing the storage and treatment capacity of a combined sewer network to prevent CSOs is the Thames Tideway tunnel. Reconnecting London with the River Thames. This project both increases the storage capacity of the network, and increasing the treatment capacity of the network by routing sewage to an upgraded treatment plant.

Separating the sewer and surface water pipe network

This is an option, though depending on the level of existing infrastructure development not always a practical one. For newer developments, this is a great option to increase the conveyance capacity of a network to a downstream treatment source. A key challenge with separated systems is that regular monitoring of any new building developments is needed to reduce/eliminate illegal surface water connections into the sewer network. These illegal connections are either done mistakenly or deliberately, brought about when a surface water pipe is not available.

About the Author Amanda Siqueria

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sewer overflow

What causes sewer blockage and how to get it cleared?

What causes sewer blockage and how to get it cleared?

Image of sewer overflow due to blockage


Dry weather sewer overflows caused by blockages can create significant issues for utility providers, the community, and the environment. What are some of the reasons sewer/wastewater pipes become blocked?

Tree roots

The number one cause of sewer blockages in most networks is tree roots.1 In addition to sunlight and carbon dioxide, trees require water and nutrients to grow and survive. The consistent flow through sewer pipes provides a rich and attractive source for trees. While the gravity pipe network would ideally be a closed system, there are numerous pipe joints and cracks where tree roots are able to squeeze through as they seek out nutrients. If enough of a gap exists, the root mass can become so large within the pipe that it can eventually block, causing a back-up of sewage flow and discharge at a point upstream. The point of discharge is commonly a sewer maintenance hole or house overflow relief gully. Dry weather overflows may persist for some time before being observed and reported for fixing.

FOG: fats, oils and grease

Another contributor to sewer blockages is FOG: fats, oils and grease. If you’ve ever wondered why you are asked not to pour these cooking by-products down the sink, this is the reason. Incorrectly managed trade waste from food establishments is also a significant contributor to FOG issues in a sewer network. These products increase the likelihood of a blocked sewer and overflow. Fats, oils, and grease can solidify after they cool and build-up on the inside of pipe walls, they have a tendency to coagulate with similar particles, or exacerbate already existing root intrusion issues, and can result in partial or complete blockage of a pipe. An internet search of ‘sewer fatbergs’ will provide graphical insight into the scale of the problem.

Foreign objects

A third cause of sewer overflows is the flushing of objects down the toilet that belong in the rubbish bin. The most recent offender on this list is wet wipes. While toilet paper is biodegradable and designed to break apart after flushing, wet wipes are not the same. This material interacts with both tree roots, fat deposits and other solid materials dramatically increasing the likelihood of blockages. Other common items that don’t belong in the sewer system and contribute to blockages include paper towels, sanitary items, condoms, hair, kitty litter, and cotton balls.

Other potential triggers for blockages in pipes are the build-up of sediment or broken pieces of pipe which reduce the cross-sectional area of a pipe and can lead to partial chokes and eventual blockage.

How are these defects identified during a CCTV inspection?

VAPAR uses artificial intelligence to automatically identify and categorise pipe defects including root intrusion, debris/deposits (incl. FOG build-up), and other obstructions within a pipe that can identify the potential risk of blockage. The VAPAR.Solutions platform provides defect level reporting that can be matched with historical work orders and blockage events to assist in pipe maintenance programs to reduce the risk of future blockages.

Image of sewer corrosion
  1. Sewer performance reporting: Factors that influence blockages (Marlow et al., 2011)