Rethinking the water cycle
How moving to a circular economy can preserve our
most vital resource.
Three billion people will join the global consumer class over
the next two decades, accelerating the degradation of natural resources and escalating
competition for them. Nowhere is this growing imbalance playing out more
acutely than the water sector. Already, scarcity is so pronounced that we
cannot reach many of our desired economic, social, and environmental goals. If
we continue business as usual, global demand for water will exceed viable
resources by 40 percent by 2030.
Many experts have claimed that wasteful
treatment of water results from dysfunctional political or economic systems and
ill-defined markets. But the real issue is that water has been pushed into a
linear model in which it becomes successively more polluted as it travels
through the system, rendering future use impossible. This practice transforms
our most valuable and universal resource into a worthless trickle, creating
high costs for subsequent users and society at large. Since the linear model is
economically and environmentally unsustainable, we must instead view water as
part of a circular economy, where it retains full value after each use and
eventually returns to the system. And rather than focus solely on purification,
we should attempt to prevent contamination or create a system in which water
circulates in closed loops, allowing repeated use. These shifts will require
radical solutions grounded in a complete mind-set change, but they must happen
immediately, given the urgency of the situation.
A new, ‘circular’ perspective on water
management
The global water crisis is real and
graphically manifest. It’s apparent in rivers that no longer reach the sea,
such as the Colorado; exhausted aquifers in the Arabian Peninsula and
elsewhere; and polluted water sources like Lake Tai, one of the largest
freshwater reserves in China. The root of this challenge is the violation of
the zero-waste imperative—the principle that lies at the heart of any circular
economy. It rests on these three basic beliefs:
·
All durables, which
are products with a long or infinite life span, must retain their value and be
reused but never discarded or down cycled (broken down into parts and repurposed
into new products of lesser value).
·
All consumables, which
are products with a short life span, should be used as often as possible before
safely returning to the biosphere.
·
Natural resources may
only be used to the extent that they can be regenerated.
Even countries with advanced water-management
systems violate these fundamental rules. They often fail to purify water before
discharging it back into the environment because cleanup costs are high or
prohibitive, even when energy or valuable chemicals could be extracted. The
substances contained in the water then become pollutants. Equally troubling,
any volume of water removed from the system is seldom replaced with return flow
of the same quality.
When considering a redesign that will create a
new, circular water system, we can take three different views:
·
the product
perspective, which calls for a strict distinction between water as a consumable
and water as a durable, since there are different strategies for reducing waste
in each category
·
the resource
perspective, which calls for a balance between withdrawals and return flows
·
the utility
perspective, which focuses on maximizing the value of our existing water
infrastructure by increasing utilization and ensuring better recovery and
refurbishment of assets
Water as a product
If we consider water to be a product—something
that is processed, enriched, and delivered—we must follow the same strict
design rules applied to any other product in a circular economy.
When water is treated as a durable, it should be
kept in a closed loop under zero-liquid-discharge conditions and reused as much
as possible. The major goal is not to keep water free of contaminants but to
manage the integrity of the closed-loop cycle. Situations that favor the
durable view include those in which it would be too costly to dispose of the
solvents and re-create them—for instance, when water contains highly specific
water-born solvents, electroplating baths, acids, and alkaline solutions used
in heavy-duty cleaning. The Pearl Gas to Liquids complex in Qatar, for example,
requires large volumes of water to convert gas to hydrocarbon liquids,
including kerosene and base oil. To help prevent waste in a country plagued by
shortages and droughts, the complex has a water-recycling plant—the largest of
its kind—that can process 45,000 cubic meters of water per day without
discharging any liquids.
When water is treated as a consumable, it must
be kept pure and only brought into solution or suspension with matter that is
easy or profitable to extract. For instance, consumable water should not be
mixed with estrogenic hormones, toxic ink found on poor-quality toilet paper,
or textile dyes. All water, including freshwater and gray water (household
waste water still fit for agriculture or industrial use), should flow into
subsequent cascades, where it may be used for another purpose. Whenever
possible, energy and nutrients should be extracted from consumable water; there
are now many revolutionary new techniques to help with this process, as well as
other innovations that encourage reuse.
Consider the following:
Our ability to extract
energy. It is now commercially
viable to generate heat and power from sludge and other organic wastes through
thermal hydrolysis, which involves boiling them at high pressure followed by
rapid decompression. This process sterilizes the sludge and makes it more
biodegradable. Facilities at the forefront of this movement include the Billund
BioRefinery in Denmark.
Our ability to extract
nutrients. We can now
recover a wide variety of substances from water, reducing both waste and costs.
For instance, the potassium hydroxide that is used to neutralize the
hydrofluoric acid in alkylation units can be extracted, decreasing costs for
this substance by up to 75 percent. Substances can also be removed from sludge,
such as polyhydroxyalkanoates and other biodegradable polyesters. The technology
has advanced so much that value can be obtained from substances that were
formerly only regarded as contaminants. For instance, ammonia removed from
water can be used in the production of ammonium sulfate fertilizer, rather than
simply discarded.
Our ability to reuse
water. We are
witnessing significant improvements in membrane-based treatments that separate
water from contaminants, allowing for reuse and commercialization at grand
scale. Many types of water benefit from this treatment, from gray water to
Singapore’s branded NEWater, which is high-grade reclaimed water. In fact,
NEWater is so pure that it is mainly used by water-fabrication plants that have
more stringent quality standards than those used for drinking water. In
addition to innovative membrane-based technologies, experts have developed new
source-separation systems that reduce mixing between chemical-carrying
industrial and household waste water, making purification easier.
Although we should celebrate these
improvements in treating water and safely returning it to the system, the
creation of a truly circular economy will eventually require even more radical
solutions. Achieving this would require the prevention of impurity and
contamination in the first place. In the European Union, for instance, 95
kilograms of nitrate per hectare are washed away from fields into rivers (an
amount higher than the 80 kilograms allowed). Discontinuing this process would
reduce both waste and contamination.
Water as a resource
Water can come in the form of a finite stock
or a renewable flow. As one example, water used for agriculture in Saudi Arabia
comes almost exclusively from fossil aquifers that will be depleted in a few
decades. Since these stocks are difficult to regenerate, future Saudi agriculture
efforts must eventually involve new irrigation sources, such as gray water, and
follow more stringent guidelines for reducing waste.
Luckily, most hydrological systems are flow
systems—rivers or replenishable aquifers. Water from such systems can be withdrawn
or consumed as long as the volume taken does not exceed the minimum
“environmental flow” required to keep the ecosystem intact, or the natural
replenishment rates. You cannot be more circular than managing the water
balance of a river basin in a rigorous and integrated fashion. Investing in
strategies that promote the vitality of a watershed are also circular,
including those that involve better forest management (protection,
reforestation, and forest-fuel-reduction programs that help control or eliminate
wildfires), improved agricultural practices (such as no-tillage farming), and
restoration of wetlands. The list of highly successful watershed-protection
programs is long, ranging in location from New York’s Catskill Mountains to
Bogotá, and many additional opportunities exist.
Technologies that help balance supply and
demand can also help water (both stock and flow) become part of a circular
model. These include drip-irrigation systems that promote conservation by
directly delivering water to root zones, irrigation scheduling, new
technologies for steel dedusting that use air instead of water, and the
application of Leadership in Energy & Environmental Design principles,
which mandate inclusion of water-saving devices.
Water as an infrastructure system
Our global water networks and treatment
plants, which are worth approximately $140 billion, consume about 10 to 15
percent of national power production. Following the principles of a circular
economy, we must maximize the benefits over these deployed assets. These
approaches may help:
Using existing assets
for more services. Utilities have
many options here. For instance, they could allow telecommunication companies
to install fiber cables through their trenches for a fee and then charge for
their maintenance, or they could use their sewage systems and
wastewater-treatment facilities to collect and treat preprocessed food waste
with sewage sludge. Using the latter technique, New York State has begun a
program that has the potential to process 500 tons of food waste daily,
generating heat for 5,200 homes. Utilities could also provide their data to
governments or other interested parties for use in various initiatives, such as
those related to healthcare or flood management.
Selling performance,
not water. Instead of
selling water and charging by the cubic meter, utilities could pay consumers
for curbing use and then sell the conserved volume—termed “nega water”—back to
the system. Such an effort, and similar initiatives, would also require a major
overhaul of rate-setting mechanisms. Utilities should also promote conservation
by selling double-flush toilets and similar devices, or by offering different
levels of service, pricing, and convenience, with the goal of encouraging
consumers to reduce use. As such, there should also be rate-setting mechanisms
in place to encourage utilities to undertake water-conservation efforts.
Driving asset
recovery. Utilities should
establish asset-recovery centers and create procedures that promote reuse of
equipment. This would include standardizing their pipes and meters to ensure
they can be easily recovered and refurbished. Utilities should also begin
tracking assets, which will allow easier reuse of equipment.
Optimizing resource
efficiency. Finally,
utilities should invest in ever more efficient operations and use green power,
ideally generated in-house, whenever possible. They should be given incentives
for doing so—something that does not typically happen today. There are many
examples where anaerobic digestion of sludge alone produces biogas that covers
more than 60 percent of energy consumed at wastewater-treatment plants.
Next-generation moves
for water-system management
Innovators, responsible operators, and
committed system developers are spearheading the creation of new technological
solutions, pilot cases, and initiatives to improve water management. Many of
the technologies are already generating profits or will be soon. These include
the bespoke polymers that are created during the biological digestion of
wastewater, as well as vapor-transfer irrigation systems that use low-cost
plastic tubes that allow water vapor to pass but not water or solutes, making
saltwater irrigation possible.
Equally important, leaders are also rethinking
their institutional approach to water management. Many of their solutions are
only being applied at small scale, however, and this must change over the next
ten years to meet the water-resource challenge. So how can the water sector
drive the much-needed system-level transition from today’s linear model to
tomorrow’s circular design? What are the attractive, integrated plays? Five
ideas stand out:
Product-design
partnerships. Even in 2015,
there is no dialogue between producers—say, of atrazine herbicides,
antimicrobial disinfectants, or detergent metabolites—and wastewater operators.
Their relationship resembles that between a distant water source and a sink,
with diluted accountabilities. As the cost of treatment mounts, pressure will
increase on producers to reduce contamination, especially as new technologies
make it easier to identify their source. Shouldn’t wastewater operators help by
offering their expertise to producers and initiating product-design
partnerships to ensure that water stays pure after use?
Resource-positive
utilities. Wastewater
utilities are ubiquitous, visible, and largely similar. They could soon become
energy positive thanks to technical advances related to sludge methanization,
waste-heat recovery, potassium hydroxide reduction, or on-site distributed
power generation. Who will champion further advances, including those that aim
to convert wastewater to energy, integrate grids, and recover nutrients?
Management for yield. Water is a powerful driver of yield in
almost any industrial process and the extraction of raw materials. Improved
site-level water management can increase beverage yields by 5 percent and
oil-well productivity by 20 percent, largely benefitting the bottom line. It
can also convey many other advantages, such as reduced heat or nutrient loss
during processing. Taken together, these advantages can turn water into a major
value driver. For instance, one pulp-and-paper producer discovered that it
could improve margins by 7 percentage points through better water management,
leaving a much more circular operation behind. Who will help other companies
find such value?
Basin management. From Évian-les-Bains to Quito,
floodplain protection is a viable method for reducing the risk of flooding and
preventing freshwater contamination. But attempts to improve basin management
often fail because they require sophisticated multiparty contracts and a deep
knowledge of hydrology and engineering. Who will help connect interested
parties and minimize the bureaucracy associated with basin-management
agreements?
Local organic nutrient
cycles. Most communities
are struggling to handle low-quality sludge and fragmented, contaminated
streams of organic waste coming from households and businesses. Simultaneously,
agriculture experts are exploring new sources for nutrients, since mineral
fertilizer will soon be in short supply. If we aggregate local organic waste
flows, we could help communities deal with their problem while also creating
vibrant local markets for fertilizer components. Who will create and manage the
local organic nutrient cycle of the future?
Each of these plays represents a new way of
looking at water and represents a huge business opportunity. They provide the
industry with a chance to reposition itself and develop a new generation of
designers, power engineers, yield managers, ecosystem-services marketers, or
synthesis-gas tycoons.
The shift to a circular water economy holds much promise. It
would replace scarcity with abundance and greatly reduce the resources needed
to run our global water infrastructure. At some point, a circular water economy
might even eliminate rapidly growing cleanup costs because no harmful
substances would ever be added to the water supply. Since water is the single
most important shared resource across all supply chains, and wastewater is the
largest untapped waste category—as big as all solid-waste categories taken
together—it is the natural starting point for the circular revolution. The
water sector’s advanced technologies and proven record of multistakeholder
agreements also lend themselves to circular solutions. We must capture this
unique opportunity now, before localized droughts and shortages become a global
crisis.
byMartin Stuchtey
http://www.mckinsey.com/Insights/Sustainability/Rethinking_the_water_cycle?cid=other-eml-alt-mip-mck-oth-1505
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