Water and waste systems
Net Zero Water
Sustainability performance at the building, neighbourhood and city scale
Emerging storm water management methods represent a key approach to sustainability of integrating ecosystems within our infrastructure. [NE Siskiyou Green Street, Portland, OR; Kevin Robert Perry, ASLA]
by Bud Fraser.
How water and waste infrastructure strategies at different scales, from the building to the city, can respond to sustainability and other challenges.
As weather patterns change, some areas are experiencing more frequent droughts that slow the replenishment of wells and aquifers, while others may experience warmer winters and reduced snow pack that, in turn, may affect summer water supply. In the Metro Vancouver area, for example, summer watering restrictions are not uncommon, and winter rains have caused periodic water quality concerns. Elsewhere, finite water supplies are being put under pressure by the increased demands of population growth and other needs such as agriculture or industrial processes.
Infrastructure Systems and Concepts
Infrastructure systems deliver services by moving and processing resources, and include the supply of water, collection and treatment of wastewater and the collection, treatment and disposal of solid waste. At the city scale, these systems can be seen as parts of an “urban metabolism” - fluxes of energy, water, materials and wastes in and out of geographic boundaries; and perhaps more importantly, transformations of these resources as they are utilized and managed.
The concept of ‘zero waste’ is one in which, rather than producing waste products from resource usage, resources are transformed from one useful form to another. Avoiding the creation of difficult to manage products or materials supports this concept, and enables the fuller cycling of resources, as in natural ecosystems.
‘Integrated infrastructure’ - taking advantage of the linkages between different infrastructure systems and resources - also supports the zero waste concept and can help us make get the most value from the least resource input. This integration can work at any scale, from the building to the city scale.
Some Sustainable Infrastructure Goals
Net Zero waste and integrated infrastructure are two approaches that can help our infrastructure systems become more sustainable. But what are some of the challenges that a more sustainable infrastructure needs to address? These goals can include:
- Efficient resource usage such as water conservation that can extend our supplies and reduce the impacts of the water supply and wastewater infrastructure and their energy consumption;
- Effective management of rain water that protects waterways, aquatic ecosystems and water supplies;
- Minimizing waste generation and disposal, reducing transportation and disposal energy, greenhouse gases from landfills, and other emissions and contaminants; and
- Recovery of energy and materials from what was formerly waste - displacing fossil fuels and reducing the need for raw/virgin materials.
- A key approach in meeting sustainability challenges is the integration of ecosystems within infrastructure, using natural systems as models. This can support our sustainability goals and meet other objectives at the same time. A good example is the near-revolution in stormwater management, from traditional collection and discharge to integrated management using a suite of natural systems complemented with mechanical options.
- Infrastructure-related sustainability goals are recognized by green building programs. For example, LEED NC gives credit for water savings of 20-30% below baseline and for recycling facilities in buildings; LEED ND gives credit for water recycling and infrastructure energy consumption.
The Life of Our Water
The natural processes of precipitation, evaporation and transpiration that re-circulate water from the biosphere to the atmosphere and back, is a self-sustaining and self-cleansing system. Intervention through diversion for human use represents a considerable disruption of this natural cycle that has many implications, including the returning of contaminated wastewater to the cycle, and stresses on our aquatic ecosystems.
Conventionally, municipal water infrastructure involves the following main steps:
- Extraction, treatment and distribution to the point of use - e.g. homes and businesses [municipal infrastructure]
- At the building: water in, wastewater out
- Collection, treatment and disposal of the wastewater effluent back to the environment [municipal infrastructure]
To date, this simple in/out service model for buildings has predominated. However, there are signs of change as aspects of resource management that are typically part of centralized municipal systems are introduced at the building and neighbourhood level. Also, there are design strategies at the building and site scale that have implications for the larger infrastructure systems.
Building and Site Water Systems
Currently, at the scale of the building or occupied unit, the sustainability performance of water systems is largely dependent on interior design decisions such as the specification of water conserving fixtures and appliances [see Sidebar]. The user experience, which includes performance, aesthetics and reliability/durability, is important to the success of these measures.
For outdoors, water-wise landscaping and efficient irrigation systems are the most critical strategies contributing to water conservation. Rainwater harvesting is also a valuable option that can work at both the single family and multi-family building scale. The cost/benefit is locally specific and climate dependent. Generally, it is relatively inexpensive and practical for the single family home.
Wastewater flows are closely related to water consumption. Low flow fixtures and low flush toilets make a positive contribution; garburators typically do not. The quality of wastewater is also important, and green alternatives to traditional household chemicals can make a significant difference to waste water quality and treatment options, particularly when the treatment systems are smaller and decentralized.
Decentralized, on-site treatment and recycling of wastewater [or 'grey' water from bathtubs, sinks and showers] for flushing toilets or other non-potable uses is common practice in water-scarce urban areas of many countries, and is increasing in North America. It may involve source separation of wastewater to grey and black; and it makes possible the use of multiple water supplies for different applications on a site. It also brings new challenges in the design of dual water supply plumbing, system monitoring and maintenance.
In addition, in larger developments on-site amenities for water purification, which may take the form of water features in the landscape, can provide significant value and achieve multiple objectives. This localized approach focuses on the rehabilitation and enhancement of site ecology. The local reuse of water also heightens awareness of chemical use and other potential sources of contamination.
Such systems work at the scale of the individual building [although more effectively in larger buildings] or at the scale of the neighbourhood or community. There are of course economies of scale, and the necessity and practicality of this approach depend on the nature of the municipal services that are available, and on the value attached to the availability of local non-potable water sources.
Solid Waste
Municipal Solid Waste [MSW] is a mixture of many products and materials. As mentioned earlier, recovering materials and energy and avoiding disposal of these resources are part of the “zero waste” philosophy. To achieve this there are currently two approaches to the handling of these materials that starts at the building scale - combined processing, and source separation.
Combined processing, where many materials are processed together [e.g. incineration], has several potential disadvantages from a sustainability point of view. Once mixed, the various products in the waste stream [sometimes including hazardous contaminants] are hard to separate and recover, and processing plants are highly mechanized and thus tend to be more centralized - requiring more transportation infrastructure and energy consumption.
When materials such as paper, plastics, and organics are separated right at the source [like under a kitchen counter], different resources can be collected and reused/recycled locally - e.g. organics for composting. It is easier to recover more materials and local recovery reduces transportation and reprocessing energy - depending on the material. For maximum effectiveness, buildings should be designed so that source separation by occupants is easy and convenient. At the community scale, collection points for different resources [such as organics for composting and recyclables] set the stage for later reclamation and reprocessing of recyclable materials.
At larger community, city and regional scales, local governments throughout the country face an impending ‘infrastructure gap’, as demand for infrastructure services grows with development, systems age and wear out, and existing capacities are reached. New capital projects are challenging due to their high cost and the lack of financial resources. In many regions, water supply is becoming an issue. These factors are spurring local governments to investigate new ways of delivering and optimizing services.
Incorporation of sustainability goals into development projects, including those that impact infrastructure, for example, building water conservation, or on-site wastewater treatment in un-sewered areas - can, therefore, support the infrastructure priorities of local governments.
Future Possibilities
- Some approaches and technologies that are on the horizon, but not established yet [at least not in North America] include: Ecological Sanitation - for example, composting toilets minimize or eliminate the need for water in sewage management and enables this resource to be completely reprocessed on site. This method has implications for building design and requires alternate servicing plans,
- Integration of resource management with building structures, for example in ‘living buildings’ that are integrated with their environment and the local ecosystems, and incorporate sustainable water management or net zero water, and
- Restorative design - not only minimizing impacts to ecosystems, but actually restoring and enhancing ecosystems.
Increasingly we face many challenges with the infrastructure services that support our communities. There is financial, political and regulatory pressure to find more economic, efficient, and ecologically sound methods of delivering these services. Considering how resources can be managed more efficiently and sustainably at different scales, including the building scale, is part of a more holistic, integrated approach to infrastructure that brings together many players.
New design models being investigated have implications for the future design of buildings and communities. Designers should be aware of the ‘future forces’ that are driving change - change that can be realized in today’s designs as the infrastructure shifts toward Net Zero Water.
»»» Related Information: ….
Water Conserving Plumbing Fixtures
by Klaus Reichardt
Commercial buildings use about 20% of all potable drinking water in North America, mostly for landscaping or in washrooms. Fortunately, fixture technologies have emerged in recent years that promise to reduce water use.
More and more facilities are installing low-flow faucets, that can save more than 7.6 litres of water per use. However, the big savings come with the use of recent toilet and urinal technologies.
Waterless Urinals: Most people, even facility managers, are often unaware of how much water is flushed away with a conventional urinal. It is estimated that a water-based urinal in a typical North American office building can use as much as 170,000 litres of water per year per urinal - enough to fill a large swimming pool. Waterless systems use no water. Instead, they have a trap, which sits atop the drain area of the urinal that is filled with a thin layer of sealant. Urine passes through the trap, and the sealant forms a barrier preventing odours from escaping. In addition, the trap/sealant eliminates evaporation of the urine, which can harm indoor air quality.
High Efficiency Toilets [HETs]: These toilets are relatively new, but becoming more and more common, as are dual-flush toilets [see below]. HETs use less than 5 litres of water each time they are flushed, 20% less than used by conventional toilets. Pressurized units, similar to those found on airplanes, are now being tested and use even less water.
Dual-Flush Toilets: Dual-flush toilets, have the option to pull the lever-releasing 3.5 litres of water for liquid waste-or push it-releasing 6 litres for solid waste.
A significant benefit is that dual-flush toilets can be inexpensively retrofitted into many older toilet models. Therefore, the cost of purchasing scores of new toilets, paying plumbers and contractors to remove the old toilet, and then installing the new fixtures is eliminated.
Klaus Reichardt is managing partner of Waterless Co. LLC., manufacturer of water conserving fixtures. .