Not going down the drain
Approximately 70 percent of the earth’s surface is covered in water, yet the amount of fresh wholesome water available is significantly limited. This is reflected in the increasing costs associated with supplying water to buildings.
The World Economic Forum believes water availability is posing a risk to your property portfolio. In fact, the Forum ranks it alongside climate change and, over the last six years, the issue has been consistently positioned within the top five global risks in terms of impact.
Within Australia, there’s huge demand for water conservation. This is a result of exciting new technologies, sustainability initiatives, evolving current and future codes, and legislation. Green plumbing is a result of environmental and economic issues, which are steering facility managers to implement innovative plumbing systems that use fewer resources, which effectively have a minimal impact on our planet.
But this is not a new concept, is it? We only have to look back 2000 years ago to our Roman predecessors who realised that aqueducts could utilise recycled bath (grey) water to flush out latrines and irrigate gardens. Somewhere along the way, however, society lost the pressing demand to conserve natural resources, instead focusing on luxury for the end user. In recent times, due to the rising costs associated with energy and the ever-impending threat of climate change, we need to consider how we can utilise energy and our resources more efficiently.
Approximately, 30 to 50 percent of the energy and water that flows into our buildings is wasted; we simply let it flow down the drain. This highlights the need to not only review and improve existing plumbing systems, in particular for ageing buildings within the facility manager’s portfolio, but to also influence future-proofing our facilities to become the smart buildings of our future.
For the past 30 years, plumbing technologies have been consistently evolving and improving. When considering the future availability and scarcity of water, where else should we look for inspiration than facilities located in extreme cold, tropical or arid environments?
However, taking plumbing systems to another dimension in terms of sustainability requires us to reach for the stars. This was the inspiration of a Swedish industrial designer, Mehrdad Mahdjoubi, working on an academic project for NASA (National Aeronautics and Space Administration). When you consider the extremities of plumbing in space, water supply must be as efficient as physically possible, particularly for existing and future facilities.
Inspired by his research and advancement with the space agency, Mahdjoubi developed a shower system recirculating the wastewater by utilising a filtration system to remove impurities, as the water is circulated. The shower system of the future operates on only five litres of water. As the water is constantly recirculated – over a period of 10 minutes – the average shower not only saves water consumption, but also saves energy.
Compare that to a typical shower, which generates about 25 percent of water savings under the current WELS (Water Efficiency Labelling and Standards) scheme. A standard showerhead uses about 15 to 25 litres of water per minute – in comparison, a three- star rated water efficient showerhead uses as little as six or seven litres per minute. You don’t have to be a mathematician to quickly realise the savings that could be made.
The revolutionary shower arrangement incorporates a simple two-stage filtration system, which ensures that larger particles, such as sand, skin and dust are removed, prior to passing through a finer filter to extract bacteria, viruses and blood. The recirculated water passes through a heat exchanger, exiting the shower nozzle, with the end user experiencing a shower with the same results as a conventional shower. Since launching, this technology has been a resounding success, in particular in Denmark, where the price of water is the highest in the European Union. It has also worked well in California, which experiences persistent drought every year.
After upgrading tap ware, showers and toilets to conserve water, are you still looking to aid water consumption and save energy in your building, but with little success? With the majority of buildings incorporating end-of-trip facilities for showering, utilising a technology that reduces water usage and energy consumption would be paramount. What can you do to take it that next step further?
SOME LIKE IT HOT
Approximately 40 percent of energy can be recovered from plumbing systems and reused by implementing a simple heat recovery system located in the drainage system. Heat recovery from wastewater systems has been operating successfully in the US, Canada and Europe for a number of years.
Smaller domestic systems generally consist of a heat exchanger – in some instances with a storage tank. Heat exchanger design ranges from fairly simple to extremely complicated, such as those incorporating a storage tank or heat pump. In most installations, however, the drainage configuration requires modification to separate the grey (shower) and black (WC) water. This is to ensure that any effluent or discharge, which contains solids and other potential contaminants, does not come into contact with and foul the heat exchanger.
The operating principles of a simple domestic heat recovery system are quite straightforward. Effectively, the incoming potable water from the main cold water counter flows through one side of the heat exchanger, while the wastewater passes through the other, preheating the incoming cold water. After leaving the heat exchanger, the potable water is plumbed to the hot water generator – in most cases, the hot water cylinder or directly to the hot water appliances, such as a shower.
There are several notable benefits that heat recovery from a wastewater system can provide to the end user, including:
- energy savings – reduction in carbon emissions, and
- reduction of the instantaneous peak hot water demand.
PLUMBING THE DEPTHS
Of the current configurations available, the most interesting technology available is sewer heat recovery, which can be used in conjunction with a heat pump that can be used for small networks of buildings. Effectively, specially adapted concrete sewers are installed with heat exchanger plates cast inside the pipework, located on the bottom (invert) of the sewer. The heat from the wastewater within the sewer is then recovered and extracted, to be used with a heat pump facility.
Channels are cast into the concrete sewer to ensure close proximity of heat transfer can take place from the effluent within the sewage. To provide an idea of water temperatures in sewers, in winter the average minimum temperature is approximately 10 degrees Celsius, whereas in summer the minimum temperature is 19 degrees Celsius, resulting in a mean annual temperature of 15 degrees Celsius.
An independent case study by Waste Water Heat, a joint European project involving research institutions from Germany, Austria, Sweden and Norway, published results after the testing of wastewater recovery devices.
Data from a sewer installation in Zurich, Switzerland, which has been in operation since 1999, provided a minimum efficiency of 69 percent in recapturing wastewater energy. The research data published indicates that this type of system can recover three to seven kilowatts of useful heat, per square metre of heat exchanger. To provide some perspective, the sewer in Zurich provides heating and hot water to a network of buildings (5300 megawatt hours of heat per year).
The future of plumbing relies on advancing technologies, creating smarter and more intelligent systems, effectively utilising water and energy in a way that leaves little to waste. Water scarcity is set to increase in the coming years. Along with the costs associated with supplying water and removing waste, this will require you to ensure your building or facility is resilient towards a net zero in tomorrow’s world.
Paul Angus is an associate director – hydraulic services atAECOM, based in Sydney. Paul has strong commercial and technical capability in developing and delivering hydraulic design strategies and solutions. He specialises in providing a sustainable approach to system design, including water conservation, recycling and generating innovative engineering solutions. He has extensive experience in the hydraulic design, pre-acquisition and condition surveys, including all forms of specialist client advisory work. He also has extensive experience in expert witness reporting, taking part in adjudications, mediations, negotiations and arbitrations.
This article also appears in the October/November issue of Facility Management magazine.
Image: Andrey Volokhatiuk © 123RF.com