Sustainability Issue #2 April 2012

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Gastric ailments because of the water?

Can bursts cause gastric ailments when the leak is repaired? This is being investigated by industry-sponsored doctoral student Annika Malm, using Göteborg as the example.   Photo: Göteborg Vatten

Gastric ailments because of the water?

By Agneta Olofsson

Can heavy rain and bursts in water mains give us gastric ailments? This is being investigated at present by researchers at Umeå and Göteborg. They have already found that heavy downpours upstream from the waterworks reduce the quality of the incoming water. Downpours are becoming much more common as a result of climate changes.

Can heavy rain and bursts in water mains give us gastric ailments? This is being investigated at present by researchers at Umeå and Göteborg. They have already found that heavy downpours upstream from the waterworks reduce the quality of the incoming water. Downpours are becoming much more common as a result of climate changes.

You will surely remember the gastric ailments in Östersund in the autumn of 2010? Those affected had been infected by the intestinal parasite Cryptosporidium that was also found in the drinking water in the town. One of the theories now is that a heavy downpour in the autumn had caused water levels in the sewers to rise so much that emergency overflow discharge had to used out into the lake Storsjön which also serves as a water source.

The polluted water may have settled at a depth in the lake where intake to the waterworks does not occur. When, later in the autumn, the water became mixed, polluted water may have got into the waterworks that had no treatment stage which satisfactorily removed or inactivated parasites such as Cryptosporidium.

- After Östersund and Skellefteå, which also had an outbreak, waterworks quickly bought UV treatment plants, says Bertil Forsberg, professor of environmental medicine at Umeå University.

The UV plant inactivates parasites if properly used. Such an expensive extra treatment stage or better protection of the water source would have been macroeconomically justified in cases such as Östersund and Skellefteå.

The Göta River is the largest water source for Göteborg. When there is heavy rain upstream from the waterworks, turbidity and the number of bacteria in the water increase. Photographer: Peter Svenson

Water quality is lower after rain

Because of climate change, we will see more and more downpours, and this affects the quality of the water entering the waterworks. This is shown by an investigation performed by doctoral student Andreas Tornevi at Umeå University, with the Göteborg water source Göta River as the example. The research project is partly funded by Formas.

He has found that the raw water outside the intake to the Alelyckan waterworks is heavily impacted by precipitation in the area. Rain thirty km upstreams gives rise to elevated values of cloudiness, turbidity and the concentration of intestinal bacteria.

The cause may be emergency discharge of sewage effluent from other municipalities upstream from Alelyckan. Another cause may be runoff from pastures where the water contains intestinal bacteria from animals.

Andreas Tornevi also found that heavy rain is at least as good an indicator of poor water quality as many of the measurements made at the waterworks. When turbidity in the river is high, for example, the intake to Alelyckan is closed and Göteborg gets its water from the lake Delsjö instead.

- But turbidity may be caused by the passage of a ship, and perhaps there are no elevated numbers of noxious organisms in the water, says Andreas Tornevi.

Towards the raw water intake. Göta River passes many municipalities on its way to the raw water intake for Göteborg. After heavy rain there is overflow dicharge of sewage effluent out into the river, which impacts water quality. Photographer: Peter Svenson

Viruses and parasites in the mains?

Indicator bacteria, coliform intestinal bacteria, are removed comparatively easily in the waterworks, but other pathogenic agents such as viruses and parasites are more difficult to tackle. They are also more difficult to detect since this requires time consuming laboratory tests; and for many pathogens there are no laboratory methods that can show whether the treatment is sufficient.

One hypothesis which Andreas Tornevi is now working on is that these pathogenic organisms are partly left behind in the drinking water and give rise to a certain increased morbidity in the population. Not proper outbreaks – those are easily noted – but a certain increase in the number of calls to 1177, Health Service Advice Centre, concerning gastric troubles.

The number of calls per day greatly varies, with most contacts during the winter months, but a certain relationship with rainfalls can also be seen.

- Just now we are looking at alternative explanations of this pattern. When the weather is bad, there is perhaps less outdoor activity at  childcare centres with greater spread of infection as a result, says Andreas Tornevi.

UV and ultrafilters. Alelyckan waterworks to the north of Göteborg centre is one of the two waterworks that supply Göteborg with pure drinking water. UV plants will shortly be installed, and the waterworks will also be equipped with an ultrafilter to deal with viruses and parasites. Photographer: Lars Lundborg

New treatment is good investment

Göteborg Water is about to expand its water treatment with an ultrafilter that increases the barrier effect through separation more than 10,000 times. This will provide an enhanced facility to stop intestinal parasites and viruses. This reinforcement costs about BSEK 1 if it is provided at both waterworks of the city, but it is considered to be macroeconomically justifiable compared with doing nothing and risking a new outbreak of gastric ailments.

Climate changes impact surface water sources such as those at Göteborg, but groundwater sources are also affected by a heavy downpour. In a groundwater source where the water passes through aerated soil strata, microorganisms are to a high degree removed before the naturally purified water is pumped up into the waterworks.

When there is more rain, the groundwater table rises and water has less time and a shorter distance through the filtration zone that is not saturated. This may cause a deterioration in the quality of water entering the waterworks.

The significance of precipitation for the number of calls to Health Service Advice Centre, 1177, in Göteborg. The yellow field denotes calls about gastric troubles, the grey one other symptoms. The vertical y-axis shows the percentage change in the expected number of calls. The horizontal x-axis shows the number of days with continuous rain. Diagram: Andreas Tornevi

Do leaks lower water quality?

Another risk of reduced water quality for the consumer is a disruption in water supply. Industry-sponsored doctoral student Annika Malm at Chalmers University of Technology and Göteborg Water is studying bursts, water leaks, and whether these co-vary with e.g. a higher number of calls to the Health Centre Advice Centre about gastric ailments. This investigation also is partly funded by Formas.

Data are collected from the 838 geographical areas in Göteborg. Each of these areas houses around 600 people. Thanks to GIS, Geographical Information System, and information given to the Advice Centre, both information concerning water leaks and cases of gastric ailments can be associated with a specific area.

Each year there are between 300 and 400 bursts in Göteborg. So long as the leak is  running full and there is pressure in the main, there is little risk of contamination. But if the water is turned off  when the leak is repaired, pressure is reduced and surrounding water can get into the main. This may be groundwater and even sewage effluent if conditions are unfavourable and the sewer is also damaged.

- It is preferable to repair water mains under pressure, and we are doing this as far as possible. I myself do not think that there is a very high risk of disease due to water main burts, but we do not know, says Annika Malm.

There are more bursts in winter and, according to Annika Malm, this is because of ground movements when the temperature is near zero. One complication in the measurements is that this coincides with periods with winter vomiting disease that spreads from person to person.

- If we have a disruption where there are a lot of gastric ailments, we can compare areas and we can also compare the time before and after a burst in the area, so that we can correct for the usual infection routes, she says.

Author :

Agneta Olofsson is a free-lance journalist

Responsible for this page: Birgitta Bruzelius

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