Decentralised Water & Wastewater Treatment In The Age of Water Scarcity & COVID
By Henry J. Charrabé 18 August, 2020
Fluence's CEO, Charrabé, shares the many advantages of decentralised treatment
Globally, water scarcity can no longer be ignored, even by major, modern cities. In Australia, Sydney suffered through its Millennium Drought for a decade. In Brazil, greater São Paulo nearly ran out of water for its 22 million inhabitants. The 4 million inhabitants of Cape Town, South Africa, narrowly escaped “Day Zero” with an emergency desalination build-out. And in India, Chennai, ran so dry that the crisis led to unrest in the streets. Add to the mix the widespread contamination of surface water and groundwater.
COVID-19 has pointed out shortcomings…
…we must get water & wastewater treatment to as many people as possible & now
While these crises — fueled by human activity and climate change — have become somewhat predictable, how many people could have seen the COVID-19 pandemic coming? This global catastrophe has pointed out shortcomings in wastewater and water-supply infrastructures, even as the World Health Organization states that frequent and thorough hand-washing and sanitation are the first line of pandemic defense.
The growing view is that we must start bringing water and wastewater treatment to as many people as possible – not in the future, but now. Many nations have declared clean water a human right, yet there often is a sharp class divide when it comes to access. The United Nations has acknowledged that progress toward its 2030 Sustainable Development Goal 6, pertaining to water and sanitation, has lagged far behind expectations.
Centralised treatment – outdated and inefficient
Traditionally, the water and wastewater sector has built large-scale water and wastewater treatment plants to leverage economies of scale. Massive investment in centralised plants and their wide distribution networks has delivered capacity to entire regions and allowed treatment to be sited remotely, where operations don’t affect civic life.
Mega-plants lack flexibility to react to changing conditions…
But mega-plants bring mega-risks. Sometimes cripplingly expensive, their massive capacity means nothing without expensive pipe networks to move water throughout the regions they serve. Typically, two-thirds of the capital expenditure for these types of plants is invested into the infrastructure of pipes and valves underneath the ground – investing in underground infrastructure which decays and is challenging to be fixed. And in addition, in a time of uncertain climate and population shifts, they lack the flexibility to react to changing conditions due to the lack of modularity.
An example is Australia’s massive Kurnell desalination plant in Sydney, which finally went into operation just as the 10-year Millennium Drought came to an end. It was promptly shuttered, long before it was paid for. It idled for another decade as ratepayers shouldered the double financial burden of upkeep and financing costs, earning the politically disastrous plant the title of “white elephant.” When the drought finally returned, Kurnell took months to restart.
Benefits of decentralised treatment – efficient into the future
In comparison, let’s look at decentralised treatment — sometimes referred to as distributed treatment — in which downscaled water or wastewater treatment plants are sited adjacent to water source, water demand, or ideally both. Decentralisation is often used as a catch-all term.
UN-Water explained the contrast between centralised and decentralised treatment by stating:
“While larger centralised water and sanitation systems provide opportunities for resource-sharing and economies of scale in high-density urban communities, less costly decentralised systems have been shown to be successful in smaller urban settlements.”
Decentralised systems often are locally controlled and not linked physically or managerially to a larger system but can typically be remote monitored. Distributed systems, on the other hand, typically feature an array of smaller plants that are connected to a central system, either physically or managerially.
…Comparatively, decentralised treatment is cheaper, flexible & comes in modular units
One of the largest advantages of decentralised treatment is the elimination of the need to build and maintain expensive pipelines, sometimes across forbidding terrain. Smaller-scale projects can also bypass time-consuming right-of-way and jurisdiction negotiations that might involve an entire region. Further, the flexibility and modularity of decentralised systems allows for just-in-time capex for customers and the opportunity to supplement existing plants or adjust, as local demography changes.
But while the concept of decentralisation has long been attractive, there have been obstacles. Plants once required ground-up design and construction, as well as trained personnel to maintain them. Global Water Intelligence‘s Christopher Gasson lamented:
“[T]he obstacle to growth is not really lowering the cost of the process. […] It is about technologies that help change the paradigm. Specifically, we need decentralised systems […].”
Fortunately, water and wastewater treatment equipment has evolved to address these problems. Pre-engineered, packaged units are now available for water and wastewater treatment, as well as desalination. These plants can be deployed with little site preparation or construction, meet the highest quality standards, and they deliver the flexibility to be scaled up or down by simply adding or removing units. They offer true agility with their unprecedented speed from order to commissioning, and give operators the ability to react to dynamic situations by moving plants or even selling them.
MABR technology reduces energy use by 90%
Another game-changing element of these pre-engineered and standardised units — at Fluence, we call them Smart Products Solutions or “SPS” — lies in the plants’ lower energy requirements. Even off-grid operation on alternative energy sources is possible in some cases. For example, our proprietary and proven MABR technology, treats domestic wastewater with up to 90% less energy and therefore allows for halving of operation & maintenance costs, compared to traditional treatment options. Since the commercialisation of our MABR technology two and a half years ago, Fluence has already deployed more than 150 of these AspiralTM plants, which contain our MABR technology, particularly in China.
Decentralisation in action
For an example of how decentralisation is spreading, consider a case in China, where the current Five-Year Plan (FYP) emphasises bringing wastewater treatment to even remote rural areas and villages. Decentralisation was the obvious answer to fulfilling the FYP mandate in Taiping village, in the Henan Province.
Decentralisation treatment was the obvious answer to fulfilling China’s FYP mandate
The village needed to treat domestic wastewater generated by its 5,000 inhabitants, but its remoteness and limited accessibility made a traditional solution difficult. So, a 300 m³/d decentralised wastewater treatment plant was installed and commissioned within a 10-day window. The technology — Fluence’s Smart Packaged Aspiral™ wastewater system — was chosen for its high nutrient removal. AspiralTM meets China’s stringent Class 1A standards, producing effluent suitable for non-potable reuse (in this case irrigation) and has a very low energy requirement.
The novel technology that makes AspiralTM so well suited for decentralisation is the membrane aerated biofilm reactor (MABR).
Because MABR relies on passive aeration, it uses much less power than traditionally aerated biological plants. The compact plants — packaged in shipping containers — owe their small size to the fact that simultaneous nitrification and denitrification (SND) take place in one tank. Portability and scalability are hallmarks of decentralised treatment.
Advanced, modular packaged plants also are available for seawater and brackish aquifer desalination. With similarly reduced energy requirements and the same unobtrusive profile, they can be quickly deployed and are easily hidden to maintain the environmental ambience of communities and resorts. Our Smart packaged NiroboxTM Mega system desalinates 1,500 m3 per day, allowing for 1.5 million liters of fresh drinking water. These NiroboxTM systems can be operated in parallel to become a Nirosite and provide millions of liters of fresh drinking water from seawater to industrial and municipal clients around the world.
Avoiding future water crises
What can go wrong next? It’s impossible to say, except in hindsight.
Delivering water & wastewater treatment now, will help with the next emergency
One thing that’s certain is that paying attention now to water and wastewater infrastructure and management can make dealing with the next emergency that much more manageable. Time and efficiency are of the essence, and in water and wastewater treatment, that clearly points to decentralised treatment – both in developing as well as developed economies.
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