Effects of pollutants on the aquatic environment
Effects of pollutants on the aquatic environment

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Effects of pollutants on the aquatic environment

7.5 Viruses

Viruses are tiny (5–30 nanometres in size) infective agents that can grow only in living cells. The virus that causes smallpox, declared eradicated from the world in 1979, is illustrated in Figure 11.

Described image
©
Copyright © Eye of Science/Science Photo Library
Figure 11  Smallpox viruses (Variola)

Most viruses are able to remain viable in water at low temperatures, provided there is some organic matter present. Once excreted, the number of viruses cannot increase since they only multiply within living susceptible cells.

The main threat to water quality comes from human enteric (intestinal) viruses that are produced by infected persons and excreted faecally. Depending on local circumstances, this may contaminate river water directly or, if treated, via sewage effluent that may be discharged into a river. If the river water is abstracted and treated for drinking purposes, the viruses may not be completely removed. (It is possible for a person to be susceptible to only one viral particle.)

The presence of any enteric virus can be taken as an indication of the possible presence of other harmful viruses. In temperate climates, enteric viruses occur at peak levels in sewage during late summer and early autumn. The exception is the hepatitis virus, which increases in the colder months.

T868_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371