Drink it in

Martin Pitt looks back on the history of drinking water and chemical engineers’ contribution to it

FOR THE supply of clean drinking water, we rightly give credit to civil engineers, from the marvellous aqueducts of the Ancient Romans and the magnificent pump rooms of the Victorians to the dams, pipelines, and modern technology of our colleagues today. However, chemical engineering is also very much involved.

Materials

The above examples depend on the synthetic material concrete, invented by the Romans, and used by them, among other things, to create siphons and high-pressure pipes.

Modern concrete stems from a thermochemical process patented in 1824 by builder Joseph Aspdin (1778–1855) in Leeds and improved by his son William (1815–1864) who created the modern cement industry. Roman concrete used lime with volcanic rock. Aspdin effectively created a similar rock by heating clay or slate with limestone, which eliminates water leaving active sites. When powdered and mixed with not too much water, alkaline hydrolysis takes place, forming bridges between particles and new rock – much faster than the Roman process, and from common minerals.

The Romans used lead (in Latin, plumbum) in their plumbing, a conveniently malleable metal, still used in modern times (until 1970 in the UK and 1986 in the US). It is attacked by soft water, giving a significant concentration of lead in water which has been standing overnight, hence the traditional advice in the UK was always to run the cold water tap for a few minutes before making the breakfast tea, and never to use the hot water supply for drinks or cooking. Hard water has a higher pH and tends to deposit scale on the inside of pipes, so reduces this danger.

The Romans were pleased to find that lead containers converted sour wine back into sweet. This is because acetic acid dissolves lead, and lead acetate was known by Victorian chemists as “sugar of lead” for its sweet taste. Unscrupulous people at this time actually added it to food and drink.

Modern synthetic plastics have substantially replaced lead, copper, earthenware, and cast iron in both domestic and civic piping. The first was polyvinylchloride (PVC), created by German chemist Eugen Baumann (1846–1896) in 1872, and patented in 1913, but no use was found for it until American inventor Waldo Semon (1898–1999) produced a plasticised version, sold by BF Goodrich in 1926 for golf balls and shoe heels, followed by the use of unplasticised PVC pipes in sanitary drainage in the 1930s and for drinking water from the 1950s.

The second was polythene (PE), accidentally discovered in 1898 by German chemist Hans von Pechmann (1850–1902). Canadian-born British chemist Michael Perrin (1905–1988) patented the first practical industrial process in 1935, and his company, ICI, secretly went into production in 1939 specifically for use with radar equipment during the Second World War. A higher density form (HDPE) was produced in the 1950s. In 1980, blue HDPE pipes were first used for drinking water in the UK, and have made laying or replacing mains vastly quicker, easier, and cheaper. Both uPVC and HDPE have an estimated service life of 100 years.

Unit operations

As well as materials of construction, the water industries use unit operations and some chemical processes familiar to chemical engineers.

The main process is the removal of suspended solids by settling and filtration, practised extensively by the Romans. In 1804, the first modern water treatment plant (using slow sand filtration) was installed in Paisley, Scotland, designed by Scottish civil engineer Robert Thom (1774–1847). Initially bottled water was supplied to households by cart but, after three years, piping began.

Very fine particles can take a long time to settle and clog filters. To deal with this, chemical coagulants can be used, which go back further than you might expect.

In the Bible (Exodus 15:23 - 25) the Israelites found a well at Marah where the water was bitter. With divine advice, Moses put some wood into it, and it became sweet. This could possibly refer to the action of tannins which leach out of woods such as oak, and which are still used today as coagulants, causing suspended matter to settle out. Sanskrit writings from about the same time (1500BC) recommend Strychnos potatorum, known as the clearing-nut tree, which is also an effective coagulant, for treating drinking water. The Ancient Egyptians used alum (Al2(SO4)3) for the same purpose prior to filtration of muddy water, and this is still the most used, though care is taken today to limit aluminium concentration in the final supply. Coagulation can actually remove a lot of bacteria, viruses, and organic chemicals which stick to the settling particles, particularly with gentle agitation for flocculation. While this and fine filtration can largely exclude bacteria, this was not understood until the germ theory of disease in the late 19th century (to discover how the beer and wine industry led to this theory, see Brewing Up a Storm – TCE 982).

Camelford pollution incident

The largest case of mass poisoning in Britain occurred on 6 July 1988 when 20 t of aluminium sulfate solution was delivered to an unattended water treatment plant for the 20,000 population of Camelford in Cornwall. The driver was not used to this delivery and had been given vague instructions. The key he had been given fitted the lock on a manhole to the final reservoir of treated water. Quality measurement was done on the reservoir inlet, so people ringing to complain about the acid taste were told the water tested fine. Advice was given to add orange juice or boil it. Within two days the management knew of the delivery error, but staff had been warned not to talk about it. It was 16 days before a letter was sent admitting higher than normal levels of aluminium sulfate but assuring residents there were no health risks. The government was keen to keep it quiet, so as not to spoil the imminent privatisation of the water industry.

Meanwhile, babies screamed as formula milk burnt their lips. Diarrhoea, vomiting, joint aches, and painful urination were experienced by many who drank the water but dismissed by authorities. The effects were not only due to the chemical itself. The acid water stripped heavy metals from domestic copper pipes and soldered joints. Shampooing resulted in green or blue hair. There are strong suggestions that people’s brain health was affected by aluminium and as many as 20 people may have died from this. Some compensation was paid for inconvenience, but a High Court judge ruled that compensation for medical conditions was not justified.

Disinfection

Chlorine gas is now the most common method of disinfection. It was first prepared in 1774 by Swedish chemist Carl Wilhelm Scheele (1742–1786). In 1800, Scottish chemist William Cruickshank (1740–1811) prepared it by electrolysis of brine, though his process was not used commercially until 1890. The first machine to chlorinate water from a cylinder of gas was produced in 1913 by American inventor Charles F Wallace (1885–1964) to disinfect the Jersey City water supply. Prior to this, the water was treated with calcium hypochlorite (Ca(ClO)₂) from 1908, a procedure adopted in many places around the world. Chlorine gas had largely taken over by 1941.

Chlorine gets its disinfectant ability from being a powerful oxidant. Ozone is an even stronger one, but so unstable it cannot be transported. German-Swiss chemist Christian Friedrich Schönbein (1799–1868) noted a distinctive smell during the electrolysis of water, so isolated it, and in 1840 called the new gas ozone, after the Greek word ozein meaning to smell. He also invented guncotton, an explosive, by accidentally wetting his wife’s cotton apron with nitric acid, and placing it on the stove to dry, with startling results. In 1857, the German inventor Werner von Siemens (1816–1892) (after whom the SI unit of electrical conductance is named) built the first commercial ozone generator, and later published a book on its possible use as a disinfectant. As a result, it was trialled at Oudshoorn, Netherlands, in 1893. French chemist Marius-Paul Otto (1870–1939) studied this and his business Compagnie Générale de l’Ozone (now Company of Water and Ozone) started the first permanent drinking water disinfection plant in 1906 in Nice, which continues today (a previous attempt in 1903 at Niagara Falls failed). By 1916, there were 26 in France and 23 elsewhere in Europe. It is effective against some very resistant organisms, particularly cryptosporidium, which killed 69 people in 1993 in Milwaukee despite the water meeting the standards for chlorination. In addition, traces of phenols (from industry or tarred roads) which are not noticeable are converted by chlorine to much stronger tasting chlorophenols such as the well-known antiseptic trichlorophenol (TCP). Other organics can give substances such as chloroform (CHCl₃). Ozone does not do this so gives a better taste in some areas.

Nevertheless, following the First World War, chlorine was cheaper (because industrial production had developed for its war gas use) and it took over generally, apart from in France, where about half the water ozone plants in the world were in the 1970s, and ozone is still extensively used.

An alternative is chlorine dioxide (ClO₂), discovered in 1811 by British chemist Sir Humphrey Davy (1778–1829) and first used to treat water at Niagara Falls in 1944. It is not handled directly, being a gas which spontaneously explodes, but is produced in solution for immediate use by treating sodium chlorite (NaClO₂) with acid or reducing sodium chlorate (NaClO₃) with hydrogen peroxide (H₂O₂). Belgium changed from chlorine to this compound in 1956. It is the main one used in Italy and Germany and has recently been adopted by Botswana. Like ozone, it oxidises rather than chlorinates, and one of the main drivers for its use (which applied in Niagara) is improved taste. It is also more effective against cryptosporidium.

The halogens bromine and iodine have been used to some extent, as has potassium permanganate (KMnO₄).

The Sanskrit writers and the Greeks believed in the power of sunlight, but for magical reasons rather than any knowledge of germs. The 1903 Nobel Prize for Medicine was awarded to Danish physician Niels Ryberg Finsen (1860–1904) for UV treatment of bacterial skin disease and in 1910 UV disinfection of drinking water was trialled in Marseille, France, though it was unreliable. Progress was made and now New York City has the world’s largest UV water disinfection plant, serving 9m people.

Other chemical treatment

To appreciate the importance of other chemical treatment, consider what happened when the city of Flint in Michigan, US, got it wrong. It got its water from the Detroit Water and Sewerage Department, but in order to save money in April 2014 switched to the River Flint which it filtered and chlorinated itself. Complaints about the taste and colour were followed by illness from bacteria, so the chlorination was increased. Chlorine caused corrosion problems at the General Motors factory, so in October they switched to the Detroit supply, costing the city US$400,000 a year. In 2015, extremely high levels of lead were detected, and many people were ill. The Detroit water contained added phosphate which passivates lead. The river water did not and was a lower pH (which should have been treated with lime) so corroded both iron and lead pipes. In addition, the increased chlorine exacerbated the problem. Free bottled water had to be provided until 2018. It cost the city US$97m to replace lead pipes, and US$600m was paid in compensation, all for a failure to treat the water chemically as the previous supplier had done.

Responsible water suppliers monitor (and take steps to adjust if necessary) pH, chloride, sulfate, and dissolved metal levels, traces of the disinfectant plus a range of chemicals including pesticides. Low pH and chloride attack metals, while high pH and sulfate attack concrete. Other dissolved salts (water hardness) can clog equipment. Chemical process control is an essential chemical engineering aspect of the industry.

Desalination

The phenomenon of osmosis through a membrane was discovered in 1748 by French physicist Jean-Antoine Nollet (1700–1770). It was purely a laboratory phenomenon until after the Second World War when it was clear that the US was running into difficulties with water supply. Senator John F Kennedy (1917–1963) began promoting the idea of research into converting brackish waters (too high a level of dissolved solids) into drinkable ones. Researchers started to develop suitable membranes (a challenging task) and in 1965 American-Israeli chemical engineer Sidney Loeb (1917–2008) started a 5,000 gallon per day reverse osmosis (RO) pilot plant producing drinking water for the town of Coalinga, California. Sadly, Kennedy was not there to see it, having been assassinated in 1963. Loeb’s cellulose acetate membrane was used in many places, but in 1979 American chemist John E Cadotte (1917–2005) patented composite polyamide membranes, essentially the breakthrough technology for RO which has made it so successful today. As someone who remembers President Kennedy’s assassination, I have seen RO develop from a trendy new replacement for the laboratory water still into a routine full-scale unit operation.

The real problem for supply of drinking water today is the profligate use and waste of water

Conclusion

The real problem for supply of drinking water today is the profligate use and waste of water. A fifth of all fresh water is used for food production, including thirsty crops such as melons in places with low rainfall. The US, in particular, has pumped out thousands of years of accumulated groundwater, and is now having to desalinate far from the sea. In 1960, the Aral Sea (between Kazakhstan and Uzbekistan) was the second-largest freshwater lake in the world with a substantial fishing industry. Diversion of water for agriculture in the USSR resulted in it being almost completely dried up by 2010, changing a productive fishery into a new desert, hurting the environment and people’s livelihoods.

Climate change has exacerbated the problem. In 2023, China’s coal production reached record levels to make up for the lack of hydroelectric power from its dams, and the Hoover dam in the US also reached record low levels, limiting irrigation and power generation. The electronics industry uses prodigious amounts of water, and a 2020–2021 drought in Taiwan restricted production of microchips with worldwide effects.
The basic chemical engineering concepts of mass balance and recycling must be more widely applied along with our concern for the environment.

The IChemE Water SIG reflects the increasing involvement of our graduates in the water industry, and the interest in the global problem shown by young members is essential if we are to continue to get a drink of water from the tap in future.

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For more on chemical engineers in the water industry see https://www.thechemicalengineer.com/features/working-in-water

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Martin Pitt CEng FIChemE is a regular contributor. Read other articles in his history series: https://www.thechemicalengineer.com/tags/chemicalengineering-history