Overview: Bacteria monitoring

Citizen science monitoring of bacteria involves collection and/or testing of water samples for levels of certain indicator bacteria, typically Escherichia coli (E. coli), which is one particular species of faecal coliform bacteria, and Intestinal Enterococci (IE). These bacteria are sometimes referred to as faecal indicator organisms (FIOs) as they are used to indicate the presence of human or animal waste in environmental waters. These bacteria themselves do not generally pose a serious threat to human health, but they are well understood and relatively easy to measure so serve as a useful indicator that human or animal faeces, alongside other potentially harmful organisms, may be present. This type of monitoring is particularly valuable in assessing potential risks to human health and identifying sources of contamination in rivers, lakes, and coastal waters.

Most conventional bacteria testing methods rely upon culturing bacterial populations over 24 – 48 hours in a warm place, until they can be detected due to a colour change in a provided growth media. This means it is not possible to obtain a result in real time, by the river bank – and that extreme care must be taken when sampling (to avoid contamination of the sample) and with any cultured samples (as they will contain unnaturally elevated levels of bacteria).

Purpose of bacteria monitoring

1. Human health protection: Monitoring bacteria like E. coli or faecal coliforms helps assess whether water is safe for recreational use or drinking. High bacteria levels can indicate contamination from sewage or agricultural runoff.
2. Environmental health: Rivers are naturally full of bacteria and other micro-organisms, and while faecal indicator bacteria themselves are not harmful to the aquatic ecosystem, they can indicate the presence of pollution that is likely to contain chemicals that are
3. Source identification: A regular programme of testing helps trace contamination sources, such as failing septic systems, agricultural practices, or stormwater discharges.
4. Community awareness: Involving citizens increases awareness of local water quality issues, fostering stewardship and advocacy for cleaner water.

Common ways to test

1. Lab testing: Samples are sent to professional labs for incubation and testing of bacteria levels, typically expressed in colony-forming units (CFU) per 100 mL of water. Environmental DNA (eDNA) can also be analysed at professional labs, eDNA can be used to identify the source of the faecal indicator bacteria (e.g. humans, cows, sea birds). Volunteers need to be trained to collect samples in sterile containers.
2. Community lab set-ups: Some citizen science programs use portable testing kits like Coliscan Easygel or IDEXX Quanti-Tray to detect and count bacteria colonies, set up at their own premises or at volunteer homes.
3. Field tests: Some novel methods like Bacterisk and Fluidion provide a much quicker result, either in minutes or hours. These methods employ a very different measurement principle, so are not directly comparable with methods that rely on culturing bacteria.

Case studies that include bacteria monitoring

• The Severn demonstrator catchment is currently testing multiple bacteria types to understand both test accuracy, but also how best to ensure volunteers are involved.
• Water Rangers, in collaboration with academic and catchment partners, has built a grassroots community lab in ZERO Guildford, a local environmental action centre.