Cities and The Future of Fresh Water: Desalination and Deep Tunnels

It’s clear that seven billion humans cannot continue to rely on Earth’s natural cycles to provide for our increasingly urban civilization. To sustain our current and future needs, and to protect the rest of life on Earth, we need reliable systems that minimise our impact on the environment.

Clean fresh water provision and sewage treatment are two of the foundations of civilization – which together provide a huge boost in health, quality of life and productivity. Increasing demands on the natural water cycle and ageing legacy systems (that date back in some areas to Victorian or even Roman engineering) mean that new technologies and novel large-scale engineering projects are needed.

On the supply side: 96.5% of Earth’s water is locked up in the salty seas, while 40% of people on the planet already suffer from water shortage*, and half the world’s people live within 60km of a coastline* – so it’s obvious that desalination is a key water supply technology.
Advances in semi-permeable membrane production allow for fast high volume desalination, especially using reverse osmosis – where hydrostatic pressure is used to push fresh water through the membrane, leaving salts and micro-organisms safely trapped on the other side.
(*UN figures)

Even in the UK, London is at risk of water restrictions in times of drought, so the Thames Water Desalination Plant was built to offset this. The plant (in Beckton, East London) runs entirely on renewable energy and can take in brackish water from the tidal River Thames – removing salt using the reverse osmosis process to produce 150 million litres of clean fresh drinking water each day – enough for nearly one million people. Once treated the water is transferred to North East London in a new 12km long pipeline, which can hold a staggering 14 million litres of water.


Photo: London at night, from the International Space Station. Credit: NASA/JSC
(public domain)

The flip-side of sustainable water management is sewage treatment: to prevent the spread of disease, minimise pollution reaching natural waterways, and to reclaim fertilizer for agriculture. Increasingly large cities produce massive sewage flows, requiring new engineering works on a heroic scale that might surprise even the late great engineering genius Isambard Kingdom Brunel.

Greater London has a population of over 8.7 million people and growing, yet like many cities it still has an extensive legacy combined sewer system, which also collects surface runoff. During heavy rainstorms excess rainwater and sewage automatically overflows to prevent flooding of the sewage treatment works. These Combined Sewer Overflows (CSOs) now pour 39 million tonnes of mixed stormwater and untreated sewage out of the 150 year old Victorian sewer system into the River Thames and River Lea every year.

Image: Combined Sewer System. Credit: EPA (public domain)

To stop this pollution two huge tunnels are being commissioned to store the excess during storms, so it can be safely treated later: the 7.2m wide, 6.9km long Lee Tunnel is the first – it runs underneath the London Borough of Newham, from London’s largest CSO at Abbey Mills to the recently much enlarged Beckton Sewage Treatment Works.

The Lee Tunnel is London’s deepest-ever tunnel, because its shallowest point was set at 75m deep so as to capture flows from the lowest point of the massive new Thames Tideway Tunnel; a 7.2m wide, 25km long tunnel currently under construction below the River Thames – which will connect 34 of London’s most polluting CSOs to the Lee Tunnel, and hence to the Treatment Works.

While other smaller cities such as Philadelphia, USA have used various approaches under the umbrella term of Sustainable Drainage Systems (SuDS) to tackle excess storm flows, London has six times the population and sits on layers of impermeable clays and saturated gravels that severely limit the flows SuDS methods can cope with – which is why the giant Lee and Tideway Tunnels are essential to fix London’s river pollution problem.


Child’s life saved from leukemia in ground-breaking use of gene-edited immune system cells

Doctors at Great Ormond Street Hospital (GOSH) successfully used “off the shelf” genetically engineered white blood cells (T-cells) in a last ditch effort to treat a one-year old girl, called Layla, who was suffering from acute lymphoblastic leukemia (ALL) that had resisted chemotherapy. This is the world’s first instance of this targeted cancer therapy in a human patient.

To achieve this GOSH doctors worked with research scientists at University College London’s (UCL) Institute of Child Health (ICH) and biotech company Cellectis. The gene-edited T-cells were modified using a “molecular toolkit” that scientists have pirated from a few genes found in certain bacteria – especially a biological editing tool called TALEN.
TALEN is a combination of a modular protein (TAL) that can effectively be “programmed” to find and bind very specific DNA sequences, together with an endonuclease (EN) which is a protein that can cut DNA, ready to replace that gene with the version desired.

The modified T-cells are called UCART19 cells, and they are produced to fight leukemia in a two step process:
First, they have a gene that programs for a characteristic cell surface protein deleted – so the UCART19 cells will be “invisible” and remain safe from the anitibodies that are given to leukemia patients to destroy their existing, diseased immune system.
Secondly, the T-cells have the gene for the CAR19 surface protein added – CAR19 will bind the UCART19 cells to a different protein called CD19, which is only found on the surface of immature white cells (called “blasts” – lymphoblasts in ALL) that proliferate in leukemia and “crowd out” other healthy blood cells, thus causing the disease symptoms. Once bound to the leukemia cells (lymphoblasts) the UCART19 cells recognise them as foreign and destroy them.

(Above: The blood stream of a healthy subject vs. a leukemia patient.
RBCs = Red Blood Cells. WBCs = White Blood Cells.

Public domain image, credit: NCI, Alan Hoofring.
Modified by J.Overton)

Clinical trials taking place at the moment normally begin with white blood cells taken from the patient because these run least risk of causing auto-immune problems, but this “bespoke” method of production is expensive. However, due to the chemotherapy and highly agressive nature of the leukemia she suffered, little Layla did not have enough white blood cells left to work with, so the team gave her “off the shelf” UCART19 cells created from donated T-cells.

Previously, this experimental treatment had only been tested on mice in the lab, in fact it was so new that GOSH had to convene an emergency ethics meeting to decide whether Layla should receive it. As routine chemotherapy and a bone marrow transplant had already failed to help Layla, and her condition was worsening, all the doctors had left to offer was either palliative care to relieve her suffering during terminal illness, or the hope of possible recovery with the UCART19 cells. So, together with Layla’s parents, they decided to opt for treatment.

After about two weeks of receiving the UCART19 cells, Layla got a rash which is characteristic of the expected immune response, and a few weeks later results showed her system was clear of leukemia cells. After two months Layla received a second bone marrow transplant, which was successful, and once her healthy blood cell count was high enough she was able to return home with her family to recuperate further. While it is still too early to declare Layla cured, and she is still being monitored in case the leukemia returns, so far she is doing well.

Hopefully, further trials will show similar success and this targeted treatment may then become more widely available for other leukemia sufferers.

(Clinical information from GOSH Press Release, biotechnology information from New Scientist  and The Tech Museum of Innovation)