Spanish Researchers Find Parasites in Treated Water in Galicia

Research team tested treated water from water and wastewater treatment plants

A team led by researcher José Antonio Castro Hermida, a scientist at the Galician Institute for Food Quality in the Xunta de Galicia in Spain, took 232 water samples in 55 Galician towns, and confirmed the presence of Cryptosproridium oocyts and Giardia cysts in wastewater treatment plants, drinking water treatment plants and recreational areas.

The results of the study, which was published in the journal Water Research, reveal that Cryptosporidium and Giardia are widely distributed in the environment, and also highlights problems with the treatments used to reduce and deactivate these parasites.

Giardia cysts appeared in 96% of the wastewater samples discharged from treatment plants, at levels of up to 6,000 per liter, while 64% of samples contained Cryptosporidium oocysts. These figures were 36.5% and 32.7%, respectively, in the case of drinking water treatment plants, and around 60% in recreational areas for both protozoons.

It was also found that treatment plants located along the coastal belt discharge their effluent directly into the sea, while those located in inland areas get rid of their water straight into rivers.

Cryptosporidiosis and giardiosis are parasitic illnesses that cause a syndrome of poor nutrient absorption and diarrhea in mammals and birds. This causes high morbidity and mortality rates in domestic ruminants during their first month of life, leading to significant economic losses for livestock farms. In humans, the prevalence of these two illnesses is heightened among people with AIDS and other immunosuppressant conditions.

The researchers acknowledge that it is not easy to find a definitive solution to these waterborne infections, which are found all over the world. Since the parasites can overcome the normal water treatment systems used in wastewater and drinking water treatment plants outbreaks could occur even in developed countries.

Cooperation between governments and the industries involved in monitoring water is also considered essential. In the United Kingdom and the U.S., the Drinking Water Inspectorate and the Environmental Protection Agency, respectively, require water companies to monitor the presence or absence of these two parasites.

Legislation in Spain states that action must be taken to determine the amount of Cryptosporidium and other organisms in the water when turbidity exceeds 5 UNF (the unit used to measure this aspect). However, 403,000 people were infected by this protozoon in Milwaukee in 1993, when water turbidity levels fluctuated between 0.25 and 1.70 UNF, so the researchers recommend that the presence of the two enteropathogens should be monitored at much lower turbidity levels.