The smart home concept is one most people are familiar with.  Smart home gadgets and devices with the promise of making our lives easier while being energy efficient and more sustainable are flooding the domestic retail market and becoming a necessary innovation in our homes. 

Now expand that thought and imagine the smart home concept in a larger context — a smart city, the new frontier in sustainable technology.

Many cities strive to be smart, such as Amsterdam, which has more than 170 collaborative projects running on an interconnected platform through wireless devices and others with only a small initiative focusing on one or two public services or amenities. But are these cities truly smart? Do even the most advanced of them manage to integrate all aspects of technology into the city’s infrastructure at every level? 

Astonishingly, none of the smart city concepts have managed to integrate water and wastewater management and, in particular, water reuse into the smart city infrastructure. Most smart city concepts focus heavily on energy, communications, transportation and local agriculture — with water infrastructure posing a unique challenge as yet without a proven solution. Most technology for successful water and wastewater management already exists but it lacks meaningful implementation within the smart city concept, which is vital on several levels. 

Our aging and costly sewer infrastructure is a challenge for all cities and the investment to redevelop and modernize is enormous, so where do we start? DEWATS (decentralized wastewater treatment systems) are now a recognized and accepted technology capable of treating both domestic and industrial wastewater close to point source. By collecting and treating used water in DEWATS and redistributing to local homes and industry, transporting water over long distances is no longer needed, significantly reducing water wastage and cost. 

Water-processing equipment represents one part of communication between all vital systems, but such communications require standards that, while emerging, require critical expansion before successful smart city implementation is possible.

While some basic standards exist for water, water reuse and wastewater, they are in dire need of development and expansion to incorporate the demand of the smart city concept. Current standards and regulations often conflict with each other, causing confusion and, for the smart city future, are mostly inadequate. Specific standards for water reuse require a great deal of expansion from defining each of the wastewater sources and treated water classifications to composing meaningful standards in the interests of water conservation, reclamation and reuse. 

Treating and delivering water in any form requires power and constant monitoring, ideally achieved centrally to offset the cost and maintain control over potential public health implications. Multiple competency standards — such as electrical, mechanical, plumbing, energy and networking (communications) — as well as architectural guidance must be incorporated into guidelines and ultimately into new standards. They must be flexible and rapidly adaptable to facilitate the pace of innovation and to compensate for new scientific findings. 

While some states such as Arizona, Oregon, New Mexico and Texas have shown more progress in water reuse regulations, others are reluctant to expand their current thinking. There is certainly room for improvement and a willingness to publicly beta test with remote supervision, the Internet of Things (IoT) and adequate telemetry needs implementation. 

Arizona, for example, has aggressively pursued direct potable reuse (DPR), the holy grail of water reuse. The science for DPR as well as indirect potable reuse is well-established and de facto legal in several states. The whole notion that water is a waste product after a single use is not only unsustainable but fundamentally wrong.

To maximize water reuse, one must determine where the water for reuse originates and what one plans to do with it once treated. There are three categories of used water — greywater, which is relatively clean water from showers, bathtubs, sinks and washing machines; blackwater, containing feces, urine and flush-water from toilets and anal cleansing water; and what has become known as dark greywater, which is kitchen effluent. However, dark greywater is not yet reliably defined in the Uniform Plumbing Code and requires absolute definition if we are to implement water reuse standards effectively. 

Depending on the treatment and desired outcome of the treated water, we end up with either potable or nonpotable water, which is clearly defined by the U.S. Environmental Protection Agency and the World Health Organization.

Water usage plays an important part in determining where and how water should be reused. In arid or semi-arid regions, such as Southern California, roughly half the water usage is for irrigation of lawns, landscaping and yards. A big push by local authorities has resulted in the installation of drought-tolerant landscaping and smart watering controllers that significantly reduce outdoor water usage. 

But what about the water we use indoors? Similar to outdoor usage, indoor water usage varies. It depends upon local conditions including climate, how many people in your household, whether you take a bath or a shower, and how often and whether you do your own laundry and cooking at home. With the average American family of four using up to 400 gal. of water indoors each day, recycling and reusing that water within the home is becoming a necessity. 

With toilet flushing accounting for about one-third of indoor water usage, do we really need drinking-quality water to flush them or should smart city planners utilize nonpotable water for this purpose? A little-known fact is that for decades now, the city of Hong Kong conserves 270 million cubic meters of fresh water every year by applying sea water to flush its toilets.

Technological Challenges

To manage water resources and optimize water reuse, live data collection and networked controllers reporting to a master system must form a major part of the substructure in all smart cities. Collecting and processing this vast amount of data is straightforward when utilizing IoT, devices and other networking protocols, such as long-range Wi-Fi and Bluetooth. 

As with all computer-based systems, special care is vital in the design of such a system to protect against cyber attacks and nefarious misuse. The master control system, in essence, manages the smart city and should employ AI to ensure efficient and safe operation, and keep all subsystems in compliance while guarding public health. 

The underlying principal design of these water treatment systems is autonomy and reliability, needing little or no user input to perform and monitor tasks. One such pilot system, developed by CleanBlu, is installed at the ReNEWW House, a net-zero energy, water and waste research laboratory home, overseen by Whirlpool Corp. and Purdue University. The system requires zero user input, uses less than 50 watts of power, processes up to 400 gal. of water each day, is virtually maintenance free and can be installed in a utility closet. 

Besides residential applications, an even larger quantity of water is available for reuse from commercial applications. One of the most overlooked sources for water reuse is commercial kitchens within food service establishments. It is not unusual for commercial kitchens to use up to 40,000 gal. of water a day. The problem contaminant in such discharges is FOG (fats, oils and grease), which causes a myriad of problems for business owners, water districts and the EPA alike. 

Once removed by effective means, such as bioremediation (as shown by the CleanBlu FOG-DS system), this vast amount of water can be further treated and used in many reuse applications including irrigation, laundry, toilet flushing and vertical farming. The vertical farming application is particularly interesting as it allows the cultivation of vegetables and crops on an amazingly compact footprint even within city centers — the growing fields are floors stacked on top of each other in a high-rise fashion. 

Various water storage and pre-treatment options are available, such as ponds, water features, living walls and even sculptures, beautifully combining function and design. Living walls in particular not only pre-treat the water but clean the air and produce oxygen. 

For smart cities to become a functioning reality, water treatment and reuse must be recognized as a major design block and then augmented and implemented accordingly. Rapid city growth and climate change present major challenges to smart city designers, especially when it comes to making water usage sustainable. 

However, truly smart cities must make water reuse a fundamental design element in part by developing whole-house management systems controlling every aspect of a smart home — water, energy and waste — that integrates into the overall smart city concept and its infrastructure. Smart water systems should form part of the smart city model and should detect different water sources for treatment to any desired quality for various reuse applications. 

For integrated systems of water reclamation, recycling, treatment and reuse to interact efficiently and in compliance, a new set of multidisciplinary standards must be written and applied. Only then will a smart city be truly smart.