Climate Action through Water Efficiency: Dŵr Uisce Hackathon with young people from ECO-UNESCO

Roberta Bellini and Aisha Bello-Dambatta

Engaging young people during their summer break by sharing research findings while stimulating their creativity and fostering activism to combat climate change can sound like a day-dreaming objective. But when you put together over three hours passionate young people, enthusiastic academics and researchers, the outcome may positively surprise you: they can collaborate on practical solutions to raise awareness on the climate action potential of being more water efficient.

Last month, the Dŵr Uisce Team decided to host a Climate Action Hackathon aimed at young environmental activists from ECOUNESCO. Hackathons began as gatherings of data scientists, software developers, business people who worked collaboratively over a short period of time to produce a piece of software or hardware for a specific purpose. This format has proven very effective to drive innovation. In recent times, it has been used in many different fields to bring together citizens, academics, professionals and experts, to innovate and find solutions to pressing societal issues. Hackathons are inclusive, challenging, and a great opportunity for sharing knowledge, learning from others and feeling united on a common objective.

The Dŵr Uisce team designed and facilitated the Climate Action Hackathon to challenge young people aged 15-17 to explore the water-energy nexus. The objective was to find practical solutions to reduce water use; the associated energy required to provide, treat and use the water in society; and the amount of GHG emitted. In other words, it was a call to plan for climate action and raise awareness about the positive impacts of water-energy use efficiencies.

The event took place on June 29th and 30th 2021 as an online Microsoft Teams event. The one hour-long pre-event meeting on the first day was a briefing session to frame the problem. It was also an opportunity for the young participants to ask questions about the Dŵr Uisce project, interdisciplinary research, and the water-energy nexus. The Dŵr Uisce team members used polls to assess participant prior knowledge and understanding of the problem, of our project and their expectations from the event. The hackathon itself took place on Wednesday June 30th 2021. It was a highly paced event, with lively interaction, Q&A, feedback and, most of all, a fabulous outcome: great actionable ideas to encourage citizens to be more water efficient in their daily lives.

Two teams of young people took part to the event, and all the participants were involved actively in peer-education for sustainable development programmes with ECO-UNESCO.

They were familiar already with concepts such as climate action projects and how to plan for them. Both teams thought of developing an app as a tool to raise awareness about the importance of saving water, energy, money, and emissions; and to encourage citizens to adopt resource-efficient behaviours to take climate action.

The first team proposed the EireUisce app, which was imagined as linked to household water meters to help users to track their usage, get rewards for saving water and information about the importance of saving water in a climate action context. The young team proposed opportunities to incentivise communities to be more water efficient including setting up a competition, similar to Tidy Towns, to crown the most water efficient Irish town.

The second team proposed the Water Usage Rating app, which was based on the novel idea (for Ireland) of a water rating system for appliances and buildings. The objective was to make citizens aware of how much water is used in households by washing machines, garden tools and water fittings in buildings. The focus was on empowering citizens, as app users, to make resource-efficient choices.

All of the young participants worked energetically and displayed great skills and abilities in team working, critical thinking and in taking a holistic approach to problem solving. Both apps have huge potential to be further developed and the majority of the young participants were keen to take the ideas forward in collaboration with the Dŵr Uisce team. In truth, the Dŵr Uisce team was “blown away” by the outcome of the Hackathon. We all were impressed by the enthusiasm, skills and positive can-do attitude in evidence. As a result of attending the event, the young participants, as activists, felt that their understanding of water-energy efficiency and consequences on the climate crisis increased.

For the Dŵr Uisce team, the event was a success both for the level of engagement, the learning and awareness realised, and the link established with young people. They are now part of our network of stakeholders. From a science communication and educational point of view, the format of a hackathon was a great fit to our Dŵr Uisce project purpose as it delivered on a number of aspects: firstly it centred the focus of the event on the young participants rather than on the project; secondly it facilitated interaction and collaboration among young peers as well as with academic researchers and professors in an informal atmosphere; thirdly it gave us the opportunity to gauge the level of interest in what we do and how the Dŵr Uisce project work is understood and applied by a non-academic audience; and lastly it challenged participants’ creativity to come up with a practical solution in a short amount of time that could have far reaching impacts.

We are planning to roll out the Climate Action Hackathon to second level schools in Ireland and Wales, to reach out to more young people and raise awareness on the climate action potential linked to water-energy efficiency.

If you are interested in having your students participate in this, please contact Roberta Bellini bellinir@tcd.ie for more information.

We take this opportunity to thank Doireann and Dunchadh and all the young activists from ECO-UNESCO for their energetic participation.

Rethinking the analysis of future high flows in Wales

In the past few months, Richard, a postdoctoral researcher in our Bangor team, has been revisiting some analysis completed during his PhD with Dŵr Uisce. This work aims to improve our understanding of changes in the characteristics of high flow events in Wales under future climate change. It is important to understand such events, as very large streamflows can results in inundation and flooding, bringing economic and social costs, implications, and distress.

The analysis is based on the results of an extensive round of hydrological modelling completed for five catchments in Wales (Clwyd, Conwy, Dyfi, Teifi, Tywi) under a worst-case future climate change scenario (Representative Concentration Pathway 8.5 [RCP8.5]). Future climate scenarios were taken from the 2018 UK Climate Projections (UKCP18) data from the UK Met Office’s Hadley Centre, the most recent projections available. These were implemented at a daily timestep into the Soil and Water Assessment Tool (SWAT) hydrological model, in order to project future streamflows up to 2080.

Previous work focussed on analysis of change in the number of days per year and season where streamflow is greater than the 95th percentile value of the whole dataset, as well as change in seasonal and annual 1-day maximum flows. While these particular factors do give an indication of the future character of high flow days (frequency and severity respectively), it is not possible to take account of or characterise changes in prolonged high flow events, such as event severity and length. The graph in Figure 1 demonstrates the factors analysed in the original research, using an example dataset.

Figure 1. Example of previous analysis factors.

In order to better characterise high flow events observed in future streamflow projections, as opposed to just high flow days as previously studied, it is first necessary to separate one event from another, so that each event is hydrological independent. To do this, the method of baseflow separation was adopted, whereby the digital filter method is first applied to the streamflow timeseries to separate the baseflow (shown by the red line in Figure 2) from the overall streamflow (shown by the blue line). Following this, individual events with at least one day of flow above the dataset 95th percentile value can be identified, with the length of these being defined as starting when streamflow rises above baseflow levels and ending when the two are equal again (highlighted in Figure 2). This method therefore allows for the identification of multi-peak events, and marks a distinction from the previous analysis by not conflating an increased number of high flow days, with an increased number of high flow events, as the former maybe a product of longer and more severe events, rather than a larger number of events. By identifying individual events, it is therefore possible to gain a better understanding of how high flow events are changing. Changes in the frequency of high flow events, for example, can be calculated by totalling the number of individual events each year and season, and changes in the duration of events can be computed by taking the mean number of days between event start and end. Changes in the severity of events can also be studied, in two ways in fact, first, by calculation of the number of days per event where streamflow peaks above the dataset 95th percentile, and second, as in the previous analysis, 1-day maximum flow. Figure 2 provides a visualisation of the factors analysed, following the new methodology.

Figure 2. Example of the new analysis factors.

Figure 3. Seasonal and annual Mann-Kendall trend analysis results for Welsh study catchments.

As can be seen, the new analysis has the potential to provide a much clearer picture of changes in the severity, frequency, and duration of future high flow events. Indeed, the results of a Mann-Kendall trend analysis of this work (Figure 3) suggest that over the study period (2021-2080) several changes are projected, with varying patterns seen both between seasons and catchments. One of the clearest trends, with most agreement between catchments, is an increase in the severity (maximum flows) and frequency (number of high flow events) of high flow events in the winter and spring seasons. The least change is seen in the mean high flow event duration, with it generally decreasing across all seasons and annually, but only to a relatively small degree, and with the least statistical significance of all of the factors presented. As can be seen in all three factors presented, seasonal change is generally more substantial and significant than annual change, with large seasonal shifts often cancelling each other out in the annual picture. No statistically significant trends were found in the analysis of number of peaks above the 95th percentile per event, these results are therefore not included in Figure 3.

The results of this analysis have important implications for a variety of sectors, indeed anyone who abstracts from river systems or relies on their flow for other means could be impacted, as well as communities or individuals at risk of flooding. In terms of water resource use, hydropower operators in particular could be affected by the results presented, with two of the three catchments displaying declines in annual maximum flows. In addition, the increases seen in spring in terms of maximum flow volumes, and number of events, could also be worrisome for flood planners, as this has important implication for mitigation plans and measures. The impacts of changing high flow and flood events have far reaching consequences, it is for this reason that getting the best characterisation of future changes is important and is why this analysis has been strengthened.

We are grateful to Professor Neil Macdonald of the University of Liverpool for his suggestions for strengthening the analysis conducted. The improved analysis has been included in an article submitted to the Hydrological Sciences Journal and greatly enhances the results of this paper. Look out for news of this publication later this year, both here on our website, as well as on the Dŵr Uisce Twitter feed, @Dwr_Uisce.

Spreading the word to the future generation: Water-Energy webinars with the children of Rathnure Primary School, Co. Wexford (Ireland)

Roberta Bellini

Sharing research findings with the wider public is one of the objectives of the Dŵr Uisce project. In particular, engaging youth in activities that are educational but at the same time interactive, fun and stimulating, offers the opportunity to explore environmental issues and to appreciate innovative solutions. Furthermore, using a place-based learning approach in designing learning events, learners can connect the different topics and themes to their locality from an environmental, geographical and historical point of view. Embracing this educational challenge, the Dŵr Uisce Team, in collaboration with Blackstairs Group Water Scheme (GWS), looked at ways of presenting the recently installed pump-as-turbine (PAT) system at an age appropriate level to which the children could relate and link to their own lives and experiences.

 Following installation of an innovative pump-as-turbine energy recovery system at Blackstairs GWS, the Dŵr Uisce team had planned to organise in-school workshops and  site visits to the water treatment plant (WTP) for all three local primary schools served by the scheme: Rathnure National School, Caim National School and Donard National School. However, COVID-19 restrictions intervened. Undeterred, the team, in collaboration with Blackstairs GWS and local teachers, designed and delivered an online experience for primary school pupils. On May 31st 2021, the first three webinars were delivered to children of 4th, 5th and 6th class in Rathnure National School, Co. Wexford (Ireland).

 The webinars explored the water cycle, the water-energy nexus, the history and technical details of the Blackstairs GWS, and the innovative role of the pump-as -turbine system. To compensate for not physically seeing the WTP and for the lack of in-person interaction, each webinar included some fun and engaging activities and visualisation tools to help the children to connect with their locality, reflect on their water use behaviour and its consequences on the current climate crisis.

 Dr. Roberta Bellini, a Trinity-based team member, introduced the webinar ‘THINK WATER = THINK ENERGY’ and the Dŵr Uisce project. Dr. Bellini facilitated a group activity looking at what actions using water the children had carried out in the past 24hrs to immerse the children in the topic. To bridge with the second part of the presentation, the children were guided through the natural water cycle using an enquiry learning approach.

 From here, Ms. Dympna Skelton, Manager at Blackstairs GWS, presented an overview of the history of the Scheme, its geographical layout and its technical details such as pipe network, water treatment process and metering, and of the approach to climate action taken by the Scheme’s board of management. In particular, Ms. Skelton noted the collaboration between Blackstairs GWS and EPS, the WTP operator, to donate the financial savings arising from the Dŵr Uisce energy recovery system to the Wells of Life Ireland charity providing drinking water wells to rural communities in Uganda.

Figure 1: Ms Skelton presenting the Blackstairs Group Water schemes to the children in Rathnure Primary School

 To replace the site visit, pictures of the WTP were used throughout. A simple but very effective Google Earth image illustrated the hydrological contribution zone, pipes and other elements of the network in relation to the Rathnure school (Figure 2). When an image of a cartographic map of the network was presented, the children were able to position local places in relation to pipes, tanks and the whole network. The children were tasked to trace the pipes carrying water from the WTP to the schools in the area on a simplified map. Finally, they were encouraged to reflect on the need for energy to perform the different activities they had listed at the start of the webinar through a discussion and a group  activity.

Figure 2: Google Earth project showing the Blackstairs Mountain, some of the BGWS features and Rathnure N. S.

 To illustrate the part played by Blackstairs GWS in climate action, Ms Skelton invited to Dr. Daniele Novara, a Trinity-based Dŵr Uisce team member, to discuss the innovation enabling the carbon footprint reduction of the water treatment operation. Dr. Novara explained the underlying principles and technical details of the PAT-based energy recovery system, using diagrams and a picture of the actual PAT in place in Blackstairs. He concluded with the environmental and monetary saving realised by the scheme, highlighting the positive local and global impacts. The children came to understand how the monetary savings of the first 12 months of operation of the PAT-based system arose and were donated to Wells of Life Ireland. They were proud of the socially-responsible connection between their local community and another in Uganda.

 The children were wonderfully curious as they engaged in the webinar. They asked highly pertinent and detailed questions including the dimensions and costs of the PAT system, the length of time required from ideation to implementation, and the replicability of the scheme elsewhere. They were curious to know if there were other PAT systems in water networks in Ireland and, on learning that Blackstairs GWS currently operates the only one, it sparked in the most entrepreneurial children the idea for a potential tourist attraction!

 Feedback from children and their teachers has been extremely positive: they praised the group activities and the use of maps and aerial views for stimulating learning, critical thinking and creating a link with the local area.

 The Dŵr Uisce Team thoroughly enjoyed the engagement experience and we hope to deliver the webinar in two other local schools in the near future.

Beyond environmental sustainability – Isabel at the SETAC Europe Annual Meeting 2021

Isabel Schestak

How can we make a decision about the most suitable “green” solution of a problem if there are multiple interests at stake, of environmental, social and economic nature? This was one of the hot topics discussed at the SETAC Europe Annual Meeting 2021, which was held online. An example for a method combining environmental and economic objectives is the eco-efficiency assessment.

I presented a poster on my study looking at how the eco-efficiency of water and energy use in a distillery can be improved by recovering heat. Several process streams and the by-products are suitable heat sources which can serve to save up to 25% of heating fuel, as could be shown in a case study on whisky production. However, as additional equipment has to be purchased and installed for heat recovery, it also comes with an environmental footprint and at a financial cost. The eco-efficiency assessment showed that both environmental and economic burdens are by far outweighed through the savings, and that despite requiring most equipment, it can be recommended to recover heat from all possible steps in the whisky making process. The investment costs can be paid back in less than 2 years.

The conference was organised by SETAC, the Society of Environmental Toxicology and Chemistry, and spans a great variety of topics much beyond sustainability assessment, including transport of micro-plastics in the environment, insect decline or anthropogenic stressors in polar regions. Despite being held as a virtual event, there were plenty of opportunities for engagement and networking. The on-demand program was complemented by live discussions to every topic and life keynote presentations. Chat functions under each contribution served as another way of interacting personally with an author.

Our thanks go to Arbikie distillery for the fruitful collaboration enabling the heat recovery study and the funders of the Dwr Uisce project for supporting the participation to the conference.

Heat recovery options in a whisky distillery. Heat can be recovered after mashing (1.), at the two distillations (2.) and from the by-products pot ale and spent lees (3.). This can save up to 25% of heating fuel in the boiler, plus water for the boiler, for cooling or for cleaning. Dotted line: study boundaries.

Water and energy management in leisure centres

Aisha Bello- Dambatta

Leisure centres are large users of water and energy and are very expensive to run. Much investment and improvements tend to focus on energy management, especially given the current focus on emissions reduction and net-zero targets. Local Authority-run centres, in particular, face increasing pressure to reduce their carbon emissions as public bodies.

However, given the link between water and energy use, we suggest leisure centres consider water management as a core component of their energy management policy and carbon reduction ambitions and targets by considering water and energy management as a single, integrated management task rather than two separate tasks as is currently typically the case. Not much is currently being done in terms of emissions reductions from water consumption and there is a significant potential for both cost and carbon savings from water use efficiency.

Improving water use efficiency is often a simple, low-cost intervention with immediate results that can have an important role to play in helping meet emissions reduction targets, as well as help reduce operational and maintenance costs of centres.

This also makes business sense as even the simplest interventions can provide significant savings in operational costs and environmental taxes. Many simple to implement interventions that can be used to help reduce water consumption whilst still maintaining minimum standards of hygiene and comfort are available at zero or low-cost, with immediate results and short-term payback periods. There may also the possibility to claim capital allowances for investing in low-carbon and/or more water-efficient fittings and appliances.

We recommend interventions to be based on the framework of water management hierarchy which prioritises interventions in order of preference of implementation, where the next hierarchy should only be considered once all potential savings from the hierarchy above have been exhausted. This is based on the principles of waste management hierarchy of the EU Waste Framework Directive which ranks interventions according to their environmental performance with respect to climate change, air and water quality, and resource depletion. 

Some of the interventions leisure centres should consider include:

·         Measuring and regular monitoring of water and energy consumption as a first and continuous step to good practice water management. This information helps with understanding consumption patterns and trends and make it easier and quicker for faults and irregularities to be identified.

·         Implementing a programme of interventions focused on behavioural change in water use aimed at both staff and customers. The cost of such programmes is often minimal, but they can lead to significant savings.

·         Regular site walk-arounds and continuous record keeping of water using fittings and appliances will make it easier and much quicker to estimate how much water is used and to identify issues. It can also bring about other benefits, such as reducing the risk of damage to buildings from condensation due to overheating and evaporation, for example.

·         If possible, increasing the stock of low-carbon and/or renewable technology installations at the leisure centres like wastewater heat recovery, solar PV, biomass boilers, and heat pumps to further reduce carbon footprint and improve wider environmental performance.

 It is important to note that not all interventions will result in reduction in both water use and energy use, and some interventions may actually increase water or energy use. In general, if water or energy demand is to be reduced, then some other factor must change to accommodate this reduction, and where a reduction of water or energy results in an increase of the other, it may not necessarily be clear which is the more sustainable outcome, and this should be decided on project- or site-specific basis.

Another important note is that these interventions are not one-size fits all. Although leisure centres typically have the same water use types, they differ significantly in age, size, location, building types and materials, functionality, and efficiency; and for this reason, interventions must be considered on a site-specific basis.

For more information or advice on how your leisure centre can save water and energy use, please contact: a.bellodambatta@bangor.co.uk

The Dwr Uisce Summer Newsletter is out!

Welcome to our Summer 2021 Newsletter bringing you up to date on the Dŵr Uisce project. Hopefully, you remain well.

In this issue, Dr Novara explains how a pump-as-turbine works in a water network in parallel to a pressure reducing valve. Dr Murali and Dr Singh illustrate their latest advancements in drain water heat recovery technologies. In addition, you can read about the launch of the Heat Recovery Tool kit for commercial kitchens, the outcomes of our programme of on-line events and the latest research updates and publications.

We take this opportunity to wish all our followers and cluster members an active summer!

Click here.

Croeso i'n cylchlythyr Haf 2021 sy'n rhoi'r wybodaeth ddiweddaraf i chi am brosiect Dŵr Uisce.
Gobeithio y byddwch yn parhau'n dda.

Yn y rhifyn hwn, mae Dr Novara yn esbonio sut mae pwmp-fel-tyrbin yn gweithio mewn rhwydwaith dŵr ochr yn ochr â falf lleihau pwysau. Mae Dr Murali a Dr Singh yn darlunio eu datblygiadau diweddaraf mewn technolegau adfer gwres dŵr draen.
Yn ogystal, gallwch ddarllen am lansiad y pecyn Offer Adfer Gwres ar gyfer ceginau masnachol, canlyniadau ein rhaglen o ddigwyddiadau ar-lein a'r diweddariadau a'r cyhoeddiadau ymchwil diweddaraf.
Manteisiwn ar y cyfle hwn i ddymuno haf gweithredol i'n holl ddilynwyr ac aelodau'r clwstwr!

Summary of Discussion by the Expert Panel on Heat Recovery Potential of Leisure Centres

By Aisha Bello-Dambatta

At a Dŵr Uisce expert panel discussion earlier this year, experts working in different areas of leisure centre design, development, operation, and management discussed the potential for leisure centres to adopt heat recovery as a means of emissions reductions.

The experts agreed that, although the potential for heat recovery is there, significant challenges remain and much remains to be done for the sector to mobilise a critical mass to adopt heat recovery as means of emissions reduction.

In normal times, most leisure centres run throughout the year, which means the savings they can make from heat recovery can be quite significant. However, resource use and operational costs, and therefore heat recovery potential will vary widely because of the variation in types, sizes, ages, building material, etc. of leisure centres. The opportunities for heat recovery are a lot larger when there is a pump type system than when centres are only burning gas. What we might end up seeing is small heat networks and ambient heat networks within leisure centres, making use of waste heat from chillers/ condensers that would be otherwise dissipated. 

There is also potential for significant energy savings through simpler, lower-cost interventions such as demand management and behavioural change interventions, which should ideally be the first step in any efficiency improvement intervention. It is very important to consider leisure centres as whole systems, and not just their MEP systems, as a more cost-effective way to improve energy efficiency.

Heat recovery is also much easier to do with new-builds that must go through the regulatory and compliance process than it is with existing centres, even with the quiet reasonable impact it can have on cost and carbon savings for existing leisure centre stock. One way leisure centres can take positive climate action and have a critical mass emissions reduction as a sector is to work very closely with industry, for example PWTAG, to mainstream the idea of reducing carbon footprint into operational guidelines.

Policy is also a very important starting point to help drive change like this at the scale required, and the panellist agreed this is moving in the right direction even if it will mostly impact new builds. They also agreed that adoption of standards like Passive House and Part L Building Regulations for commercial buildings will also lead to much better energy efficiencies. These stepwise changes are moving in the right direction, but it may be challenging to ask already very financially stressed centres to buy into heat recovery systems, even with soaring fuel prices.

It remains to be seen if the government’s plan for net-zero ambitions and targets will push policy towards forcing leisure centres towards decarbonisation, although there is indication from current state funding for public sector buildings to increase adoption of newer, greener technologies. The question is whether policy, e.g., Part L Building Regulations will force the move to electrification. There is also an opportunity for localised networks to recover heat from different users though out the leisure centres – e.g., recovering heat from gyms to preheat pools, and vice versa in existing leisure centres, which is already standard in a lot of new builds. 

Challenges also remain with pool operation guideline orthodoxy. Many guidelines, such as the need to dump and replace 30 litres of hot water per bather or guidelines on circulation rates, for example, are largely based on experience of good practice over the years, with little scientific underpinning. Yet, these are considered quite sacrosanct even though there is no scientific basis for much of it. The general trend with operational guidelines in pools also tend to require more circulation, which inevitably means more energy use and more water dumping – both of which are in conflict of trying to run pools with minimal carbon footprint.  

Of course, with Covid-19 there is an additional need for ventilation and therefore energy use, costs, and emissions. There is legislation in place in both Ireland and Wales in relation to minimum efficiencies for heat recovery systems to allow centres to reopen and keep the pool environment as safe as possible. However, the requirement to increase the fresh air and flush out as much of the contaminated air as possible without putting it through the recycling system back into space is not energy efficient. There is therefore a trade-off between the efficiency gains in carbon savings and the need for additional ventilation to make everyone safe.

One very slight silver lining of the lockdown is having time to find out all sorts of interesting things about pools that were not previously known. We are in this experiment now with hundreds and hundreds of pools with no bathers. One of the quiet interesting observations is a dramatic reduction in the amount of chlorine needed to maintain a given chlorine concentration. Although it is certainly not going down to zero and pools differ quite widely in how much chlorine they are using – probably depending on the presence of things like biofilms (a non-direct bather related contamination that consumes chlorine). This has helped identify the source of not just the waste, but also the production of unnecessary Disinfection By-Products that can be that can be very harmful.

There has also been a discovery of quite several examples of controlled valves on heat exchangers passing. With the heating off, there is still quite a lot of hot water still circulating through the pool water heat exchanges. Therefore, the lockdowns and slowdowns are going to have some impact on future investment in energy efficiency, even if it is just to fix problems identified. There is very much a place for government investment in this process, and there may well be policy and business support to make this happen.

The panellists agreed that is not yet clear what the impact of the lockdowns will be on future investment in green technology like heat recovery, considering the long periods of closures that have happened since March 2020. One thing that is certain is that leisure centre operators are really struggling financially, but it is unclear to what extent this will have an impact on future investment. A lot of the pool operators operate on a not-for-profit basis and will be struggling, so there may not to be a desire to invest until centres are back up and running and profitable again.

For more information on the Dwr Uisce project work in leisure centres or advice on how your leisure centre can save water and energy use, please contact: a.bellodambatta at bangor.co.uk. 

Minimising the Impact of Heat Recovery on Wastewater Treatment Processes

By Madhu Murali

Our monitoring work at industrial and municipal wastewater treatment plants has found that they have a significant potential for heat recovery. However, there are some concerns regarding the impacts of heat recovery on the efficiency of treatment processes, particularly if a heat exchanger is introduced into the treatment area. To assess these potential impacts, we have replicated a common industrial treatment process, Dissolved Air Flotation, in the lab-scale at Trinity College Dublin. This setup will be used to both determine the scope for heat recovery from Dissolved Air Flotation Tanks and assess any subsequent impacts on their treatment efficiency.

Wastewater temperatures at industrial sites can be very high, particularly in the food and beverage industries where cleaning with high temperature water is often required. Our monitoring work at two meat processing plants showed that their peak wastewater temperatures were as high as 40°C with an average temperature of around 20-30°C. As the wastewater from these plants are treated on-site in treatment facilities, there is an opportunity to recover some of the embedded heat in the wastewater while it is treated. However, the potential negative impacts of heat recovery on the treatment efficiency of wastewater treatment processes should also be analysed to ensure they are minimal. A common treatment processes present in both on-site treatment facilities, Dissolved Air Flotation (DAF), has been selected to conduct a detailed analysis to determine the impacts of heat recovery on its operational efficiency.

Figure 1: A schematic diagram of the lab-scale dissolved air flotation tank

DAF is a physical treatment process by which suspended pollutants in water can be removed. Small bubbles (or microbubbles) are introduced into the wastewater in a DAF Tank, the bubbles aggregate around suspended particles in the water and lift them to the top of the tank where they can be skimmed off the surface. The microbubbles are formed by compressing air and water in a tank or vessel, called a pressure vessel, to a high enough pressure that the water is saturated with air. When this pressurised air and water mixture is released into the DAF tank through special valves that maintain pressure, the rapid change in pressure from the pressure vessel to atmospheric pressure causes the air to be released in the form of microbubbles. Flow patterns within the tank are controlled by the use of baffles, positioning of the inflow/outflow, and the volume of inflows such that the removal of suspended particles is improved. DAF is commonly used to treat wastewater from the meat processing industry, which have a lot of organic and suspended pollutants in them.

Figure 2: A photo of the lab-scale dissolved air flotation tank with microbubbles seen on the surface

A lab-scale DAF tank (Figures 1 and 2) has been set up at the Hydraulic Laboratory in Trinity College Dublin for experimentation related to heat recovery. The DAF tank is supplied heated water at a maximum temperature of 40°C from a supply tank and a pressure vessel supplies the water/air mixture to create microbubbles. The DAF tank also has two baffles near the inlet to control flow through the tank. Initially, the focus of our work with the lab-scale tank will be in identifying parameters to stably operate it and then characterising flow patterns in the separation zone of the tank to ensure that this is similar to that seen in other DAF tanks.

Future work will focus on identifying optimal locations for heat recovery in the DAF tank by measuring water temperature at different locations and identifying areas with optimal flow patterns. A heat exchanger can then be installed at a selected site to quantify the amount of heat recovery possible in our lab-scale tank. Another line of work will focus on determining any impacts on treatment efficiency in the DAF tank due to heat recovery.

This will involve examining the change in flow patterns and any significant changes in outlet wastewater temperature due to the introduction of the heat exchanger. A proxy suspended pollutant, such as clay, may also be used to determine if heat recovery impacts on its removal by the DAF tank.

Sharing the findings: Insights from the Dŵr Uisce Online Events Portfolio

By Roberta Bellini

The Dŵr Uisce Online Events Portfolio was planned and designed with the aim to share the research findings and project progress with a broad audience of interested participants. The Panelist Discussion on Heat Recovery potential in leisure centres and the Dŵr Uisce Sustainability Webinar Series, a programme of four online events covering the topics of Micro-hydropower, Drain Water Heat Recovery and Benchmarking water and energy efficiency, were featured in the portfolio. The events took place during the period February to April 2021 and have proven very successful.

Dr Aisha Bello-Dambatta, from Bangor University, hosted the Panelist Discussion on February 23rd. The panelists discussed the opportunities and challenges for heat recovery in leisure centres drawing from their professional experience. Twenty four attendees from leisure centres and other SMEs in Ireland and Wales took part in the event and discussion.

The Dŵr Uisce Sustainability Webinar Series was launched back in December 2020 with four events designed to provide the audience with insights and details of our various research areas, including demonstration of practical applications of the technological solution and tools being developed.

On February 24th, Dr Daniele Novara from Trinity College facilitated the first webinar of the series on EXPLORING MICRO-HYDROPOWER. In his presentation he covered the technical details, opportunities and challenges of Pump-As-Turbine (PAT) installations in ‘micro’ and ‘pico’ generation schemes, as well as the specifications of two PAT applications designed and deployed at two demonstration sites, one in Ireland and one in Wales. The webinar attracted over 30 participants from a range of fields, from water-energy companies to research institutes, from small business to public bodies and charities.

March was dedicated to the opportunities and applications of heat recovery from drain water with two webinars on 10th and 24th. In the first webinar, RECOVERING HEAT FROM DRAIN WATER- THE OPPORTUNITY, Dr Murali and Dr Singh, Trinity College Team members, took participants through the background, feasibility and opportunities for recovering the embedded wasted heat in wastewater at domestic, industrial and wastewater collection and treatment levels. The researchers gave an overview of both what they have achieved so far and their future research plans. Participants engaged with the facilitators via the chat asking questions and providing feedback. On March 24th, Isabel Shestak from the Bangor Team and Dr Jan Spriet, previously in the Trinity Team, introduced participants to the technical requirements and potential savings of drain water heat recovery in commercial kitchens. An innovative and user- friendly Heat Recovery Tool for commercial kitchens was launched on this occasion and participants were invited to test it using their own commercial kitchen data or a dataset provided on the day. Very positive feedback was received, with most of the participants saying their results were showing potential savings in costs and greenhouse gas emissions.

The last webinar, BENCHMARKING WATER AND ENERGY EFFICIENCY, was held on April 14th. Dr Annum Rafique, from the Bangor Team, explained what benchmarking is and how it can help businesses and organisations to improve their energy use in relation to water heating requirements. It was followed by the details of a study of benchmarking for the hotel sector and the opportunities for increased efficiency presented by Nathan Walker, Bangor University.

Screenshots form the four webinars of the Sustainability Series

The Dŵr Uisce Team was delighted to welcome over 100 participants to the five events, some of them attending more than one event. Feedback was received from more than a third of the participants; when asked how they would rate the events, 88% of the respondents thought they were ‘Excellent’ or ‘Very Good’. All of the respondents thought the events were either ‘extremely’ or ‘very’ organised.

The audience was a mature audience with some prior knowledge on the topics; nonetheless the webinar contents offered them the opportunity to further their knowledge and understanding. In fact, most of participants said they could use some the information and knowledge learnt from the events. There was a clear appetite for future events, particularly as an opportunity to share the results of long term monitoring at the demonstration sites.

Results of the feedback received from the participants.

In terms of growth and consolidation, the Water- Energy Network has expanded from 105 organisations (Nov ’19) to a current total of 141.

Watch this space: the team is now working on further events for the second half of 2021 and into 2022.

How does a Pump as Turbine operate in a real water network?

Daniele Novara

Pumps As Turbines (shortened as “PAT”) consist of regular water pumps running in reverse as turbines, and therefore generating power from a stream of pressurized water. How do these devices operate when installed within a water network in parallel to a Pressure Reducing Valve (PRV)? And how to design a system able to cope with sudden variations in water pressure and flow rate?

Whether you are a regular visitor of the Dŵr Uisce website or just someone who occasionally checks the project updates, you may be already familiar with the concept of using “Pump as Turbines” (in short, “PAT”) to generate power from water networks. In short, these devices consist of regular water pumps which are utilized in reverse to generate electricity from a pressurized water stream as an alternative to conventional (and expensive) custom-made water turbines. These devices can be used to produce carbon-free, clean and renewable power with a low installation cost and ease of maintenance and they are particularly suitable for integration with existing water infrastructures.

 In fact, most water transport or distribution systems such as drinking water, irrigation or industrial cooling networks will typically have nodes at which pressure must be reduced in order to avoid leaks and pipe bursts. This is normally achieved via a Pressure Reducing Valve (PRV) which dissipates the excess water pressure as heat and noise. However, a Pump as Turbine can be inserted in parallel to such PRV and recover a portion of the dissipated pressure as useful electricity. As a consequence, the power generated by the PAT will offset the electricity consumed by the whole water network in a circular economy approach.

 The Dŵr Uisce research team over the recent years has focused extensively on several aspects of the PAT technology which were previously unknown, helping the scientific community as well as the general public to learn more about this class of devices and their application. These efforts culminated in the construction of a hydraulic test rig at Trinity College Dublin to test the performance of centrifugal PATs and eventually to the installation of two devices in Ireland and Wales. However, both these pilot plants are located at sites which offer a “conventional” hydropower layout where a portion of the water flow of a river is diverted into a pipeline and eventually across the turbine. Therefore, neither sites are located in a fully pressurized water network in parallel to a PRV as mentioned in the previous paragraph, which would pose additional challenges in the system design. Among these challenges, the main one is to ensure at any time that the water flow is never disrupted by the presence of the PAT even under exceptional circumstances. This translates into the need of a bypass pipeline which diverts from the turbine the water that can’t be processed by it. However, at the same time it is also important to minimize at all times the amount of water that bypasses the PAT since this results in an energy loss.Despite the fact that over the last decade there has been a number of scientific publications investigating the behaviour of PATs in water networks, most of them either did not include experimental data or utilized a sophisticated computer-operated bypass valve which greatly increased the complexity of the system. As opposed to this approach, what if a conventional PRV could itself be used as the bypass valve without the need of an additional element? How well can a PRV act as a turbine bypass valve, and how finely is it possible to tune it?

 In order to answer these questions, the existing hydraulic test rig at Trinity College Dublin has recently been upgraded with a PRV in parallel to a PAT (Figure 2) and tests are ongoing to evaluate the interactions between the two devices under varying flow and pressure conditions.

Figure 2: Upgraded test rig with PAT in parallel to a PRV