10-07-2024

The 4 Es: The biggest challenges in wastewater treatment

The 4 Es represents the biggest challenges faced in wastewater treatment: Emissions, Energy and operating costs, Effluent & Experience. Each of these will be explored in more detail, so that they can be understood clearly. We will then explore ways in which these challenges can be managed and mitigated.

twinn aqua suite algorithms industrial wastewater

BernardMcWeeney

With more than 20 years experience in the water and wastewater industry in commercial and technical roles, Bernard McWeeney is the Global Sales Director for Aqua Suite, Royal HaskoningDHV’s software solutions that look after and optimise the complete man-made water cycle.

We have identified the four most prevalent challenges we see currently in wastewater treatment. In this blogpost, we will define and explore these challenges in greater detail, whilst also exploring ways and means to mitigate them. They encompass regulation, operating costs and people amongst other subjects. The 4Es represents the 4 major challenges in wastewater treatment:

Emissions
Energy costs
Effluent
Experience

1. Emissions

Wastewater treatment plants are responsible for approximately 1.5% of global emissions, which is only slightly lower than the aviation industry. This is quite a shocking statistic and shows the importance of reducing emissions in wastewater treatment processes. In the UK most utilities have ambitious plans to achieve net zero by 2030. The discovery of the impact of emissions such as N²O, has made this target even more challenging.

Electricity is not the main contribution to emissions. The combination of other emissions contributes more to the problem. Of those, Nitrous Oxide (N₂O) makes up the biggest percentage. The diagram shows the typical emissions split on a wastewater treatment plant. This is a change from what the pie chart would have looked like 10 years ago and this is due to the significant amount of research that has been conducted on process emissions.

Graph of total emissions during wastewater treatment

Emissions are released during every part of the wastewater treatment process. This diagram shows what emissions are released and where.

Graph that shows emissions during the wastewater process

Royal HaskoningDHV has conducted extensive research into N₂O emissions for more than 15 years. During this time, we have established that N₂O is a significant contributor to wastewater treatment plant emissions. On average, it makes up 37.5% of emissions, but more importantly, it is 265 times more potent than CO₂. N₂O is mainly produced due to the nitrogen removal process being sub-optimal The diagram below shows the difference in potency of the emissions released on a wastewater treatment plant.

Graph N2O pollution in relation to other emissions

2. Energy and Operating Costs

Wastewater treatment plants are directly affected by the high cost of energy, natural gas and chemicals.

During the covid pandemic , these costs increased due to inflation and other macroeconomic factors. Post-pandemic, they did not return to their pre-pandemic levels. The wastewater sector has had to get used to such significant increases in costs in a relatively short space of time. The diagram illustrates this.

When we look at the operating costs on a WWTP, we can observe the following split. Energy is still the biggest contributor to operating costs on site at 40%, with labour also being a significant cost at 30%.

Graph wastewater treatment costs breakdown

If we also look at the split with regards to different parts of the WWTP, we see that 55% of the costs are in the water line, 35% in the sludge line and the remaining 10% are associated with influent pumping.

Pie chart wastewater treatment cost split

A major factor in those costs, is the way that WWTPs are controlled using traditional PID based control. This method is based on feedback control, so the system is constantly searching for the correct setpoint. This causes high energy consumption, sub-optimal process conditions, and higher asset maintenance costs. One way to mitigate and improve this is to use Advanced Process Control. A prediction is made well in advance and the control is feed-forward as opposed to feedback. The software knows what is coming and dictates setpoint accordingly. where required. This results in the process being optimised and the operating costs being minimised.

Graph wastewater treatment irt process control

So, in summary, in order to mitigate high energy and operating costs it is essential to:

Use the right equipment: implement the best available technology and practices.
Use the equipment right: Choose a holistic, predictive control method.

3. Effluent

Ensuring effective wastewater treatment has become increasingly challenging. Demanding environmental standards mist be met, and pollution events prevented.

To illustrate the challenge please look at the diagram which shows that only 20% of water bodies in the UK are classified as having good ecological status. This is an alarming situation and partly identifies why maintaining the required quality of final effluent is such a challenge.

The European Water Framework Directive will be enforced to change this situation for the better and help to improve the status of our rivers and water bodies.

Wastewater treatment standards have become more demanding over the years as can be seen in the diagram below, with the need to remove micro-pollutants firmly on the horizon.

As treatment standards increase, progressing to the next step is difficult due to the need to modify existing processes on site and the necessity to add extra process steps. There are many different options to meet these evolving standards depending on what the need is and what is currently on that particular site.

Ultimately, the consequences for not meeting these standards are serious. As well as the clear risks to public health, not adhering to consents can result in significant fines for the utility.

To mitigate these issues, water utilities need to understand the limitation of their current WWTPs, whilst modifying and/or implementing new treatment steps. However, possibly the best mitigation is to implement predictive and holistic control.

4. Experience

The workforce is aging. 20% of the workforce in the water industry is due to retire in the next decade. In the UK, just 8% of all workers in the water industry are under the age of 24.

The diagram illustrated the fact that there are more workers in the higher age brackets now than there were in 1950. If people are retiring or leaving the water industry, clearly we do not want to lose their knowledge and experience.

Compared to previous generations, retaining talent is more difficult. Gen Z are much more likely to decide to leave a company or an industry than previous generations.

We must work hard as an industry to attract young and talented people but also think about what they need to stay engaged and continue to contribute positively to the water sector.

We need to capture the knowledge of those retiring or leaving the industry, whilst attracting and retaining younger talent.

We can do this by:

Investing more in digital solutions like AI and Advanced Process Control
Telling a more compelling story about the purpose of our industry and the importance of water in our world
Giving clear opportunities for people to develop their skills and experience

Digital solutions and AI will help us to capture and retain the knowledge of those retiring, whilst attracting new talent that wants to work with the latest technology and innovation.

Graph showing different generations in relation to retaining employees

The wastewater sector is faced with significant challenges now and in the future. With the research that has been done and the realisation that gases such as Nitrous Oxide (N₂O) have a marked effect on total emissions, this challenge will continue to be at the forefront of water professionals going forward. There will be continued focus on energy and operating costs, as there has been for 10-15 years already, with water companies searching for innovations to reduce these costs even further. Effluent quality and consents will continue to be the number one priority on wastewater treatment sites, in order to meet regulations and ensure public health. Finally, in order to have a thriving wasetwater sector, we need to have brilliant people. We must be able to attract new talent, as well as retaining the knowledge of those retiring and leaving the industry.

There is no simple solution for these complex challenges. However, as we have demonstrated in this series, one strategy that can help to tackle all these four issues, is the introduction and implementation of Advanced Process Control (APC). APC can provide real benefits immediately, without the need for more hardware or expensive changes to site. Through Twinn Aqua Suite, Royal HaskoningDHV has more than 28 years experience of offering and implementing APC software to optimise the operation of the man-made water cycle. If you interested in what we can do, please let us know, we would be happy to help you.

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