Sustainability by Design: The Future of Water and Wastewater Systems

Our environment has changed dramatically during the past few decades – and change is still unfolding. By 2050, there will be 9.8 billion people on our planet, most of them concentrated in cities. This rampant urbanization, combined with the effects of climate change, is putting increased pressure on resources like water, raw materials, and energy. Water quality, availability, and quantity is rapidly changing. The sustainability of natural resources and their efficient and effective use is becoming a critical public issue.

There are enormous opportunities to achieve a sustainable future in water and wastewater systems. Besides being a resource on its own, water is also a medium for other resources, such as nutrients, chemicals, and energy. As water resources become less available, their recovery and reuse are becoming even more imperative. There are an encouraging number of innovative technologies and management approaches emerging. Wastewater treatment plants can no longer be considered the villain, but instead become resource recovery “mines.”

Interestingly, there is no universally agreed-upon definition for sustainability. The idea stems from the concept of sustainable development, originally defined in 1992 as development that meets the needs of the present without compromising the needs of the future. The 2005 World Summit on Social Development introduced the three pillars of sustainability: environmental, social, and economic. More recent approaches, like the Circles of Sustainability, distinguish four domains of economic, ecological, political and cultural sustainability. Regardless, it’s clear that the term sustainability implies an integrated, holistic approach that provides for the needs of today, maintains balance between all ‘pillars,’ and ensures enough resources for the future.

To understand the opportunities for sustainable water and wastewater systems, these systems must be examined in a broad sense. As water moves throughout urban and rural areas, it acts as a transport medium for other important resources such as nutrients, energy, and materials, which brings many opportunities to recover these resources and close their cycles.

Water Cycle

One basic objective of sustainable development is to promote water protection, efficiency, and conservation. Improving efficiency reduces withdrawals from limited freshwater supplies, saving more water for future use while improving the ambient water quality and aquatic habitat, reducing operations costs and postponing the expansion of water infrastructure. There are many water efficiency and conservation strategies, ranging from supply-side practices (treatment technologies, leak detection and repair programs, reuse, increasing storage capacities, etc.) to demand-side policies (consumer conservation programs, public education programs, metering programs, water-efficient appliance incentives, etc.).

Historically, five to 10 per cent of our water is usually wasted in surface water treatment plants. Using residuals treatments ensures that wasted water is reclaimed back into the inlet of the plant, resulting in an overall water loss of no more than one per cent.

Converting wastewater into an alternative water source is recognized as a promising solution, with many communities approaching the limits of their available water supplies. Wastewater can be treated to different levels of quality to meet a variety of uses, such as irrigation, industrial water, groundwater recharge, non-potable domestic use, recreational, and ultimately potable use (direct or indirect).

For many municipal governments, water and wastewater treatment plants are their largest energy consumers, often accounting for 20 to 40 per cent of their total operation and maintenance (O&M) costs. On the other hand, energy costs represent the most controllable costs and the biggest opportunities in providing water and wastewater services. Incorporating energy efficiency practices into water and wastewater plants typically has payback periods of only a few months to a few years. The early savings can be reinvested in other sustainable solutions.

Energy-efficient equipment, systems, and components, such as variable speed pump drives, can be easily implemented to save energy. Smart controls can improve water and sewage operations in real time, optimizing energy consumption without the need for major capital investment. Renewable and clean energy sources, like solar and wind, can be explored as potential power sources.

The anaerobic digestion of the biosolids produced in wastewater treatment generates green energy, which can potentially offset the electricity consumption of the entire plant. In the most simplistic scenario, biogas can be used to feed boilers and provide hot water heating to the plant; however, it can also be used in combined heat and power (CHP) engines to produce electricity and thermal energy on-site. It can even be refined, then injected in the natural gas network or to produce biofuels for transport vehicles.

Moving away from the conventional biological treatment of sewage can also help the wastewater treatment plant achieve net-zero energy. Implementing ceramic filter membranes in place of active sludge reduces the energy needed for aeration and drastically reduces greenhouse gas (GHG) emissions. This established technology has lower sensitivity to incoming quality variations, is not easily fouled, is averse to abrasion, and allows the installation of pressure recovery devices. You can learn more in our “Re-Thinking the Treatment of Sewage” for additional insight.

Understanding how a system uses energy is essential to better manage costs and identify the opportunities in energy efficiency. The Barrie Wastewater Treatment Facility, located in Barrie, Ontario, is an example of identifying opportunities to reduce energy and operational costs.

The sustainable material management intent to reduce consumption, minimize waste and prevent pollution. The origin of the material or resource is equally important, low impact materials can be recycled/renewable or recovered and/or locally sourced.

There is a growing desire to minimize chemical usage during treatment. The ability to reduce chemical treatment provides direct operational benefits for communities, including operator safety, process stability, reduced chemical deliveries, and increased public perception. Removing contaminants from the source water by a biological path is also an alternative. Biological filtration to remove metals, such as iron and manganese, has been practiced for over 40 years, eliminating the need for strong oxidants and decreasing significantly the water used for backwash. Read about the Sainte-Angelique Water Treatment Plant in Saint-Lazare, Quebec, Pugwash Water Supply in northern Nova Scotia and this Canada released Western Australia Insight article as examples. A new treatment involving biological ion exchange resins for organics removal was recently installed full-scale, “The Future of Clean Drinking Water: A New Treatment Method” details this.

The integrated resources recovery approach stems from the circular economy concept, whereby waste is considered a valuable resource from which multiple products can be derived.

Resource recovery from wastewater and sludge should not be overlooked. Wastewater treatment plants can be designed for high-performance capture of phosphorus and nitrogen. These nutrients can be then consolidated into biosolids for use in agricultural fertilizers. “From Wastewater to Renewable Resource” looks further into sustainable resource recovery technologies. Different valuable products like cellulose, biopolymers, alginic acid, and metals can also be recovered from wastewater. However, since the solutions to recover these materials may compete, it is necessary to know which solutions or recovered products are preferred over others.

In terms of optimal site, water and wastewater facilities are contemplated as environmentally responsive buildings which create healthy, comfortable and productive surroundings. The facilities can include heat recovery ventilation systems, geothermal heating and cooling, high-efficiency boilers, natural daylighting, LED lightning, green roof, energy-efficient apparatus and water-efficient fixtures. Sites can be restored to provide native habitat on the undeveloped portions and local wildlife sanctuary. Stormwater runoff can be minimized, retention areas created and harvested for non-potable use. The facilities construction can use local and recycled materials, while construction waste can be recycled. Although green roofs are widely executed in the private sector, they are rarely seen on water and wastewater facilities. These opportunities are not exclusive of large facilities, it can also be found at smaller plants such as the Town of Ladysmith’s Wastewater Treatment Plant.

There are many barriers that must be overcome for these opportunities in water and wastewater systems grow into positive outcomes. For our purposes, two paradigms are worth mentioning: the perception sustainable designs are unjustifiable expenses, and reluctance to accept new treatment technologies.

Historically, engineers have approached sustainability considerations as design constraints, and utilities have perceived them as an unjustified investment. Water and wastewater system decisions have been traditionally driven by considerations of function, safety, and cost-benefit analysis by public utilities. Frequently, the assessment boundary is limited to the water/wastewater facility in question, putting aside opportunities such as co-digestion of the biosolids with food waste to boost the biogas production to be used in the region bus fleet.

In order to understand the value of sustainable design, we need a collaborative and integrative assessment of the design solutions. A life-cycle analysis is a holistic approach that clarifies whether a design is actually environmentally, economically and socially sustainable over the long term. To make the life-cycle assessment framework effective:

• Start early — Understand the primary goals of the project, set the sustainability goals, define the boundaries and incorporate sustainable alternatives from the beginning.
• Use benchmarking — Collect data on energy, water, resources and conduct investigations to set the baseline.
• Form an interdisciplinary team — Sustainability means finding new and creative solutions that cross disciplinary boundaries. Bring a diverse team together to find integrated strategies.
• Evaluate alternatives — Sustainable design requires careful evaluation of alternatives against multiple criteria. Select a comprehensive set of qualitative and quantitative indicators comprising the three dimensions of sustainability. Assess the performance of each solution. The most balanced solution with respect to the three pillars is the most sustainable option.

Water and wastewater systems must be measured and assessed in terms of sustainability performance and to enable continuous improvement. This work involves the selection of indicators and methodologies used for incorporating sustainability consideration into facility design. Although the life-cycle assessment framework is promising, the lack of early planning, a reasonable baseline and the selection of the indicators can threaten its success. An Integrated Resource Recovery (IRR) strategy was developed for the Courtice Water Pollution Control Plant in the Municipality of Clarington (Courtice), Ontario. The study created a powerful tool to help the Region identify and evaluate IRR options, not only at this moment, but also in the future.

Another important barrier for sustainable design is the adoption of innovative technologies. Water and wastewater treatment plants have traditionally been publicly owned entities, and the adoption of new technologies has been viewed with skepticism due to fear of failure. It is also important to understand that “new technologies” does not necessarily mean cutting-edge technology, but also processes that were not previously implemented by the utility or nearby, (even if it was widespread in a different region).

To hasten adoption of new treatment technologies, utilities need to collaborate with equipment manufacturers, consultants, and academia in evaluating, testing and implementing them. New technologies proven viable can help secure capital investment, minimize the risk of failure and achieve successful implementation. This is the foundation for regulatory agencies to endorse the innovations as part of the permitting process.

The limited availability of natural resources, accompanied by growing societal and environmental concerns, urges the adoption of an integrated holistic approach that encourages compromise to re-establish balance between the social, environmental, and economic aspects. Due to water’s intrinsic capability to carry over other resources, there are crucial opportunities at water and wastewater facilities to help achieve sustainable development.

Despite energy efficiency, water conservation and process optimization having long been hot topics in the water and wastewater field, few municipalities in North America have incorporated sustainable design into their infrastructure. Sustainable or “green” design is continuously perceived as an unsustainable investment.

By retrofitting the traditional life-cycle assessment and collaborating to validate new technologies, we can demonstrate the tangible benefits of incorporating sustainability into water and wastewater systems design. This won’t happen overnight – but with progressive thinking and commitment, we can lead the way without compromising the bottom line.