 |
The small pilot plant, which uses solar energy to heat the water for desalination.
(Source: The New York Times) |
Introduction
Chennai has a population of 7 million and every year it
faces an acute water shortage crisis. (Willem Hofste, Reig, and Schleifer
2019). As defined by the UN Water initiative, a country is
classified as ‘water stressed’ and ‘water scarce’ if water availability goes
below 1700 m3 per person and 1000m3 per person, respectively. India currently
scores at 1453 m3 per capita water availability. The Minjur and Nemmeli desalination
plants were setup to counteract this precise status of India and ease the
demand burden on the Chennai metropolitan. Currently, both plants supply 100
million litres a day (MLD) but at exorbitant operational costs.
The global situation of water is an observable feature of
climate change and a huge question mark. Population growth, over-extraction, climate-induced
water stress, and pollution are all reasons responsible for the loss of
freshwater.
It is important to distinguish what freshwater is in
comparison to other kinds of water. Freshwater is found in glaciers, lakes,
reservoirs, ponds, rivers, streams, wetlands, and even groundwater. These
freshwater habitats are less than 1 percent of the world’s total surface area.
It is different from saltwater which is 97 percent of the water found on Earth.
Brackish water forms the third constitutive element of all the water found on
the planet (US-NOAA).
This disproportionate fractionation of water harkens
discussions on Malthus’ controversial claims. It is not difficult to predict
that with such an asymmetrical distribution of water, there are large
populations that do not have access to fresh water and it is only worsening
with time. The Malthusian problem flourishes in this argument in particular,
even for the staunchest skeptic. Naturally, for millennia the water cycle has
been sufficient in providing water to the world population. But, the
disturbance in the water table presently has led to more than a third of the
population experiencing decreased water access. And with the population
burgeoning in size, an enlarging population will suffer from water insecurity.
Desalination is a technique currently in use in the
countries of Israel, Saudi Arabi, the United States, and Singapore, to name a
few. It involves taking seawater and turning it into consumable water for
households and industrial facilities. Currently, it serves an extremely likely
future for treating seawater and producing freshwater to bridge the shortage
gaps for populations.
Flow diagram of RO desalination process.
Deeper Dive: Desalination as a
Process
Present-day desalination is in some ways a modernized and
technologized example of a process that has been a practice for many years.
Today, the process is a lot more intricate and tedious. It can be divided as
follows:
1.
Desalination
Plants located near seawater sources intake saltwater from the sea through
pipelines. Most plants are located very close to the sea or at the harbor to
reduce costs. Additionally, plants can be jointly located next to
energy-generating plants.
2.
Saline
water goes through pre-treatment which includes sedimenting and less intensive
filtration to remove larger sediments. Processes like carbon-filtering are also
employed occasionally.
3.
Water flows through winding pressurized tubes
for one of two processes that are most widely used for treating seawater -
thermal desalination which distills the water by turning it into vapor or by
membrane-filtering which involves reverse osmosis. RO/Membrane desalination is
currently the more widely used technology. Its desalting rate is about 98-99.5%
which makes it extremely effective.
 |
| A sheaf of reverse-osmosis membranes, unfurled to show the layers that separate salt from water.(Source: The New York Times) |
4.
In
efforts of energy conservation and carbon footprint reduction, a hybrid method
of desalting was developed. The hybrid method utilizes both the distillation
method and the RO method.
5.
Adding conditioners to the water like alkalic
products and some metals naturally found in freshwater which the human body
requires. Alkalic products like caustic soda, limestone might be added to
tackle RO permeated water which contains carbon dioxide and is acidic enough to
corrode water distribution pipelines.
6. Fully-treated water is supplied to water utility services and brine water is released. There are multiple methods to deal with brine water but the most common is to release it back into seawater.
What is wrong with it?
●
Cost - Currently, desalination plants
have a very capital-intensive, and the technology is still not used at the
scale where the costs can be driven down. Although, there are near about 13,000
desalination plants supply water in 120 countries. Yet, most of the
desalination plants are located in energy-rich and high-income countries. These
countries find it cheaper to establish and operate a desalination plant. There
is also the issue of maintenance of membrane and replacement. High-pressured
streams passing through membranes cause them to wear out and reduce their
effectiveness.
●
Energy-intensive
- Desalination is geographically
located in energy-abundant regions because it is very energy-demanding. From
the start of the process where seawater is flown into pressurized pipes, the
heating and membrane-filtration, and finally the separation of the remaining
brine discharge from the treated water require a large amount of energy.
●
Ecological - With regards to costs, the brine
discharge from desalination being unregulated and released untreated into the
sea is one of the bigger and more uncertain threats. Brine water is 3-5%
saltier than seawater and is adversely depleted of oxygen. The unregulated
release of brine water is a serious question mark due to the adverse effects it
can have on marine biology. Due to having a higher density than seawater, brine
water coagulates and it is speculated that this brine water could form
underground pools that can exist under the ocean currents and stay collected.
It is known that naturally-occurring brine pools are particularly harmful to
marine organisms living close to the seabed. If they enter the bounds of the
brine pool, they enter into a state of toxic shock and often die. Thus, while
there is a lack of concrete data of this aspect of a plant’s released brine, it
is an unknown variable that could pose a serious threat.
The temperature of the wastewater is
also a matter of concern as releasing of warmer water into the sea is water
pollution. It leads to the destruction of aquatic plants and animals, and it
promotes oxygen depletion through algae and reduction in dissolved oxygen.
Wastewater from desalination plants also contains toxic metals which become
more soluble in warmer water.
Moreover, a recent study revealed
how a previously estimated brine release was grossly underestimated. The study
revealed how 142 million cubic meters of brine is discharged all over the world
daily. In comparison, the amount of potable water produced is nearly 150% less
at approximately 65 million cubic meters. This number in itself is gargantuan
to comprehend; the amount of potable water produced is half of what the Niagra
falls averages.
Threats to the ecological system do not just end here, apart from mentioning
the effects of the energy-intensive process on the general environment, it is
important to note that the process of intaking water is also risky. In many
nations, like the United States, desalination’s strongest contention has been
due to the intake process threatening fish and their eggs, planktons, and
larvae. The pressurized pump acts like a vacuum sucking up all the water,
without discrimination. The countermeasures put in place to avoid taking in sea
organisms are not completely effective. In California, grills have been put in
place in an endeavor to minimize harm but. With the grills featuring gaps as
thin as a credit card, marine life does not stand a chance at being protected
due to their generally smaller sizes.
●
Privatization - High operation costs have led to
private players assuming a key role in the desalination industry - a possible
future of the majority of the freshwater resource available. This puts things
into perspective, in terms of how precarious it can be to have
private-ownership of water in a water-scarce future. The risks of privatization
run along many lines with one of them being the cost of buying comparatively
expensive water due to the production costs and profit margins of a private
owner. Low-income groups are at threat of being unable to afford water with
higher profit margins. And finally, peri-urban and rural groups could face
underserving of water supply due to higher expenses for provision, particularly
landlocked ones. With water being deemed internationally as a subset of all
human rights as per the UN yet, privatization could make it extremely hard to
hold private stakeholders accountable. The severity of mismanagement could lead
to more than shutting down of the company, it could disrupt water supply
leaving entire establishments without a regular supply of water.
●
Price - The price of desalinated water is
typically higher than those sold by public services. This stems from the
previously mentioned high capital requirements but also because of ownership of
plants being with the private or in a public-private partnership. The largest
desalination plant in the Western hemisphere is located in Carlsbad,
California, and is privately owned by a company called Poseidon, which is being
met with resistance over new expansions in the state due to the price of
desalinated water being 4-5 times more expensive than the state’s water supply.
It is also necessary to note that currently, cheaper methods to procure water
can be employed by harvesting natural resources and promoting conservation
efforts in agriculture, which are 2-4 times less expensive than opening a
desalination plant.
Politics - Desalination has played a very interesting role in
domestic and international politics. If managed correctly, it promises to ease
internal tensions due to rising water scarcity. Water has always played an
extremely key role in negotiations and bilateral relations and multilateral
relations. Desalination plants have introduced new dynamism to the situation.
For example, Israel which began its desalination plant in 1964 was suffering
from acute water shortage. But it now produces a surplus of potable water due
to its strides in the effective employment of desalination plants. This surplus
is forwarded to the West Bank as water diplomacy, but the courtesy is also
retracted to engage in hard-liner politics. This provides new dimensions to
general water politics and it raises the question "will landlocked
countries face a greater disadvantage in water politics in the future?"
Saudi Arabia has the highest concentration of desalination plants and is the
owner of the largest desalination plant in the world. Saudi ARAMCO, the largest
fossil fuel company and the most valuable company in the world is also a major
partner in the desalination sector. Dow Chemicals, too, are investors and
providers within the industry. Both these companies have tainted track records
of mismanagement of resources and are heavy industry companies that rely on the
hydrocarbon industry. But these hard-to-abate industries could potentially
diversify into water resource management which calls for closer inspection of
the environmental management and the motive of transitioning to
desalination.
What could the future look like
Given the concerns about the environmental costs draw the biggest attention, the attempt has been to reduce carbon footprints of desalination plants. The aforementioned hybrid method achieves just that. Technological advance in desalting has made it 50 times more efficient than before. But it is still far behind in being termed as ‘affordable’ and ‘sustainable.’ Attempts to increase sustainability have largely been to geographically place plants adjacent to energy plants that require water input. This fulfills requirements for energy plants which are supplied water for cooling from desalination plants which in turn saves heating costs for desalination. Along the same lines, when energy demand is low, energy production is redirected to desalination plants which do not see much variance in demand curves.
Solar power’s rise as the best option for renewable energy
has seen a transition within the desalination industry too. The generation of
electricity is now being performed by photovoltaic panels in smaller desalination
plants over the world such as in Australia. The Australian plant also harvests
wind turbine energy.
A contentious sustainable source of energy is now in process
of approval to be constructed adjoined to a desalination plant in the Saudi
kingdom. It is a proposal for a nuclear reactor engaged desalination plant.
Nuclear desalination is not new, most nuclear reactors have utilized the
benefit of having an attached desalination plant due to their position away
from civilization and water resources as concern for contamination. Nuclear
ships also use small reactors not just to power the engines but also to
maintain a supply of potable water. But with any nuclear technology, the
question of its practicality looms. Nuclear energy’s exhaustive lifespan is
also an added concern over the security concerns.
The most revolutionary attempt to make desalination truly
green is also an ambitious one. Circular water economies rely on tapping into
every single resource of the wastewater. This treatment of brine is recognized
as the ‘Zero Liquid Discharge’ (ZLD) method. ZLD reserves the brine produced by
the desalting process and treats it further by separating the water from the
salts. Expensive technologies like brine concentrator and brine crystallizer
allow for the most efficient separation and allow for resale of these salts for
industrial use (Panagopoulos, Haralambous, and Loizidou 2019). The separated
water would go back into the pipelines for processing and for being treated
into potable water. The energy source would also have to be renewable. However,
using these technologies would further increase the price of operating.
Small desalination practice is proliferating in agriculture.
In the future, irrigation from desalted water could form a sizable share. But,
mismanaged disposal of brine is already threatening aquifers and other
freshwater sources with brine contamination.
Finally, it is important to realise that desalination
regardless of its negatives is gaining large traction. How much ground it gains
in provision of freshwater is a matter of time. But it is crucial that
regulations and their implementation be placed on the industries relatively
soon, before we are the brink of exacerbating climate change with another
anthropogenic activity.
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