Thirsty Industries: Hospitals

The water a hospital is built around is the water at the basin outside every ward, where the hands are washed between one patient and the next, and it is the smallest part of what the building uses. Behind the wards, in the basement and on the roof, are the users that take the rest: the steam sterilisers that run all day for the operating theatres, the laundry that washes a tonne of linen before lunch, the cooling towers that keep the theatres and the scanners cold, the kitchen, and a room on the renal floor where a row of machines are each passing a patient's blood past a stream of water that has been cleaned more carefully than anything the patient will drink. A hospital bed in a rich country uses several hundred litres of water a day, and in the largest teaching hospitals a thousand or more, which is as much as a small household uses in a week.

This article is about where a hospital's water goes, why a dialysis machine is the most demanding tap in the building, what the drains carry out, and why a hospital that loses its water is in more trouble than one that loses its power.

Where it goes

The water in a hospital is spent, in rough order of size, on cooling, on sanitation, on the sterilisers, on the laundry and the kitchen, and on the medical equipment. The shares vary with the climate and the age of the building. In a hot country the cooling towers on the roof, which the Legionella article on this site describes, evaporate the largest single share, hundreds of cubic metres a day in a big site; in an old building the sterilisers, which in their older designs used a continuous stream of cold water to condense their steam and cool their drains, can be the largest user, and replacing that one piece of plumbing has cut whole hospitals' water by a fifth. The basins, toilets and showers of a building where thousands of people work, visit and lie in bed are the steady base load underneath.

Against this stands the other end of the world. The WHO sets a minimum for a health facility anywhere of about five litres per outpatient and forty to sixty per inpatient per day, enough to wash hands, clean a ward and give a patient a drink, and about one in four health facilities on Earth has no basic water service at all: no piped supply on the premises, a well or a tanker or a walk. The rich country hospital's five hundred litres a bed and the clinic's bucket are the two ends of the same industry.

The dialysis room

A kidney cleans the blood; when both fail, a machine does it, and the machine does it with water. In haemodialysis the patient's blood is pumped through a filter of hollow fibres while a solution called dialysate flows past on the other side of the fibres, and the waste in the blood crosses the membrane into the dialysate and is carried away. A session takes about four hours and uses about a hundred and twenty litres of dialysate, three times a week, and the dialysate is made on the spot from purified water and a concentrate. Because the membrane is thin and the blood is on the other side of it, anything in the water that can cross goes straight into the patient, several hundred litres of it a week, and the water standards for dialysis are stricter than for drinking water by orders of magnitude on the things that matter.

The things that matter begin with chlorine. City water carries a residual of chlorine or chloramine to keep it safe in the pipes, which the disinfection article on this site explains, and at the few tenths of a milligram per litre in a tap it is harmless to drink. Across a dialysis membrane it is not: chloramine in particular oxidises the haemoglobin in red cells and destroys them, and outbreaks of anaemia in dialysis wards in the 1970s and since have been traced to a utility switching to chloramine without the hospital noticing. So every dialysis unit runs its own treatment plant before the machines: a softener, then two beds of activated carbon in series to strip the chlorine and chloramine, then reverse osmosis to take out the dissolved salts, the aluminium that once caused dementia in dialysis patients, and the bacteria, and then a loop of pipe that circulates the pure water past every machine and back, with no dead ends in which a biofilm could grow. The loop is tested for bacteria and for endotoxin, the fragments of dead bacteria that cause fever, to limits that drinking water is never held to, and a run of fevers in a dialysis ward is treated as a water fault until something else is proved. The reverse osmosis rejects about half of what it is fed, so a dialysis session uses on the order of three to five hundred litres of city water for its hundred and twenty of dialysate, and a unit with twenty chairs running two shifts a day is a factory's water in a single room.

Steam and linen

The theatres run on steam. Every instrument that goes into a body is sterilised in an autoclave, a pressure vessel in which steam at a hundred and thirty degrees is held for a few minutes, and a large hospital runs a bank of them through the day; the steam is made from softened and often purified water, because minerals would scale the chamber and stain the instruments, and in the older machines the exhaust steam was condensed and the hot drain cooled by running mains water through a jacket, continuously, whether the machine was sterilising or idle. That one design, repeated across a sterile services department, used tens of thousands of litres a day, and replacing it with a closed cooling loop is the single largest saving most hospital water audits find.

The laundry is the other steady user. A hospital changes its sheets, gowns and towels daily, several kilograms of linen per bed per day, and washes them hot, at seventy degrees or more to kill what they carry, with a rinse to match, at twenty to thirty litres per kilogram of linen in a modern tunnel washer and more in an old one. Many hospitals have sent the laundry to contractors, which moves the water off the site rather than removing it, and the hospitals that run their own recover the heat from the rinse water to warm the next wash, which cuts energy more than water.

What goes out

The drains of a hospital carry what no other building's do. The patients excrete the drugs they are given, and a share of every dose leaves the body unchanged: antibiotics from every ward, the iodine contrast agents injected for scans by the kilogram a day, the cytotoxic drugs of the oncology unit, anaesthetics, painkillers, hormones. The concentrations in a hospital's sewer are tens to hundreds of times those in the town's, and the sewage works at the end of the pipe, which the wastewater and pharma articles on this site describe, was built for the biology of ordinary sewage and takes out some of them and passes the rest to the river. A hospital is a small share of a city's sewage, a percent or two, and a large share of some of what the river carries. A few hospitals in Denmark, the Netherlands and Switzerland have built their own treatment plants, with membranes, ozone and activated carbon, to clean the effluent before it reaches the sewer, and the results are good and the cost is high; most of the world's hospitals discharge to the public sewer like any building, and the pathogens, including the resistant bacteria that the antibiotics select for, go with the drugs.

Losing the water

A hospital that loses its power has generators, by law, and tests them. A hospital that loses its water has far fewer options, and the question of what happens is one that the water outages of recent years, in Jackson, Mississippi, in Houston in the freeze of 2021, in the cities of the Day Zero article, have forced into the plans. Without water the sterilisers stop, which closes the theatres within hours; the dialysis stops, which within a day or two is a medical emergency for every patient on it; the cooling stops, which closes the scanners and the theatres again; the toilets stop; and the hand washing on which every infection rule is built stops. Hospitals in the countries that have thought about it hold a day or two of water in tanks and have a contract for tankers and a plan for which services close first, and the dialysis units have agreements to move patients to the nearest unit with water. The hospitals that have not thought about it find out, as the one in Jackson did in 2022, what a building with a thousand beds and no water pressure is.

What it teaches

The hospital is the industry on this site whose water is a safety system rather than an ingredient. The sterilisers, the dialysis loop, the cooling and the basins are each a line of defence, and the water behind them has to be there, at pressure, clean to a standard set by what it touches, every hour of every day. Most of it goes to cooling and cleaning, as in any large building; the part that goes across a membrane into a patient's blood is the strictest water in the city, cleaner than the ultrapure water the chip plants use on the measures that matter to a body. A hospital's drains return the drugs to the river, and the works downstream were not built for them. The next time the tap in a ward runs, something in the basement made it possible.

Five hundred litres a bed, a hundred and twenty litres a session across the blood, and a building that cannot work for a day without it.