Lakes And Rivers Are Reservoirs For Microbial Contaminants


Microbial contaminants can enter lakes and rivers from an extensive range of sources. Main sources of microbial contamination include faecal contamination from humans, domesticated animals, and wildlife (Jung, et al., 2014). These microbes pose a significant health risk to humans who may be consuming the water, using the water recreationally, or for harvesting seafood from the lakes. It is therefore important that the microbes in the lakes and rivers are controlled, or that there is prevention of microbial contamination to begin with. This essay will outline how microbes enter rivers and lakes, the health risk they pose, and how they are controlled or prevented. There will be particular emphasis to lakes and rivers as a reservoir in developed countries.

How do microbes enter rivers and lakes?

One way in which human faecal contamination occurs is due to release of treated wastewater from sewage treatment plants into lakes and rivers . First of all, it affects the healthy biodiversity of the region, how water pollution affects animals and why it is important to know.
What are the main types of water pollution and what rivers and lakes are in the worst condition. Although the sewage is treated before being released, the treatment plants are only responsible for reducing the number of specific microbes such as coliforms, E. coli, phosphate and ammonia. Therefore, other faecal contaminants still remain in the effluent when it is released into the lakes and river. This is because other pathogens are not classed as high risk and so they don’t need to be monitored. For example Windemere, a lake in the Lake District National Park in the United Kingdom, is classed as a recreational bathing water and so only certain pathogens have to be reduced in the effluent before it is released. The output of water treatment plants is largely increased in summer in Windemere due to the Lake District being a popular tourist destination, attracting 15.5 million tourists each year (Rhodes, et al., 2012). Therefore, this results in more microbial contamination of lake Windemere in the summer. Sewage treatment plants account for around 46% of the faecal indicator bacterial load in lake Windemere (Stapleton, et al., 200).

Whats wrong pollution you can also look into, a non-standard problem is human faecal contamination of rivers and lakes can also occur due to overflow of septic tanks. Septic tanks often experience issues causing them to overflow. The overflown material then gets washed into the lakes and rivers. This material is untreated and so contains many microbes which contaminate the reservoirs. In some locations, such as Windemere, human faecal contamination can be the result of sewage overflow. This can be due to sewage systems being outdated and so they often aren’t able to cope causing them to overflow. This untreated material then gets washed into lakes and rivers, further contaminating them with microbes. In the Lake District there are often sewage spills into Windemere; since the year 2000 there have been an average of 248 spills per year (Stapleton, et al., 200). This inputs a large amount of microbial contaminants from human waste into the lake.

Topics of water pollution

Animal faecal contamination is a large cause of microbial contamination of lakes and rivers. Animals defecate on the land surrounding lakes and river, and then the faecal material gets washed into lakes and rivers by surface runoff when it rains. Animal faeces contains many pathogens including E. coli and campylobacter which will contaminate the water. In the Lake District there is a large amount of sheep farming and so there will be a large amount of faeces that get washed into lakes such as lake Windemere. The sheep in this area are largely prone to infection with Cryptosporidium, and so Cryptosporidium spores get released in their faeces and washed into the lakes and rivers. Animals such as badgers and deer can also carry the Cryptosporidium pathogen, further increasing its spread. Birds have also been shown to contribute to the faecal contamination of lakes and rivers. In lake Windemere it was found that birds are responsible for around 0.2-1.2% of the total faecal coliform load (Rhodes, et al., 2012).

Rainfall is a large contributor to microbial contamination. In periods of high rainfall, surface runoff into lakes and rivers is greatly increased. Surface runoff can contain many contaminants including animal faeces and fertilisers which will be washed into the rivers and lakes and cause further microbial contamination (Sasakova, et al., 2018). A study conducted in 2013 showed that rainfall had a significant positive correlation with increased concentration of faecal indicator bacteria load (Staley, et al., 2013).

Deforestation has contributed to the microbial contamination of lakes and rivers (Mapulanga & Naito, 2019). In Thirlmere, which is a reservoir in the Lake District, a large proportion of the trees surrounding the lake have been removed. Trees contribute the water management because their roots absorb a lot of the water, which reduces the amount of water available to flow over the ground into lakes and rivers. Therefore, if there are less trees there will be less management of water because less water will be absorbed. This means there will be more water that travels over the ground into the lakes and rivers, carrying with it lots of faecal material and other microbes. Removal of trees is also associated with increased occurrence of landslides which adds more land matter, and so faecal material, into the lakes and rivers increasing microbial contamination.

How does water pollution affect the ecosystem

Also an important point is to study the question of how to solve water pollution in a short time. According to our data, the process of water treatment is very long. Exposure to microbial contamination of water supplies can have negative impacts on human health. This can be through either consuming water from lakes and rivers or from using them for recreational bathing. Due to improvements in sanitation infrastructure and increased water quality in high income countries, the pathogen load of public water supplies has largely been eliminated (Bridge, et al., 2010). Although the pathogen load is largely eliminated there are still recurrent outbreaks of waterborne diseases in high income countries (Bridge, et al., 2010). For example, in 2010 in the USA it was suggested that between 12-19.5 million cases of illness are caused by waterborne pathogens per year, supporting the fact that waterborne pathogens are still a significant health risk (Bridge, et al., 2010).

An example of a disease caused by a waterborne pathogen is cryptosporidiosis, which is caused by Cryptosporidium spp. Cryptosporidiosis is a diarrhoeal disease which is highly contagious (Cacciò & Chalmers, 2016). In 2010 in the UK it was estimated that there are around 60,000 cases of cryptosporidiosis each year, with tap water being to most common source of encountering the parasite (Bridge, et al., 2010). Figure 1 displays the life cycle of Cryptosporidium. The figure shows how cryptosporidium cysts from the faeces of both infected humans and infected animals, such as cattle, can enter lakes and rivers. Cryptosporidium from the faeces of infected humans can end up in lakes and rivers via effluent released from sewage treatment plants. Cryptosporidium from the faeces of infected animals can be washed into lakes and rivers via surface runoff during periods of rainfall. Figure 1 then shows how humans who use the lakes and rivers recreationally or for drinking water can ingest the Cryptosporidium cysts and thus develop cryptosporidiosis. This creates a cycle of infection.

Mycobacterium avium subsp. Paratuberculosis (MAP) is another waterborne pathogen that poses a significant health risk to humans. If animals are infected with the bacteria pathogen MAP, they will then contaminate their pasture (Rhodes, et al., 2012). When it rains MAP will travel from the pasture into the lakes and rivers via surface runoff, thus contaminating the lakes and rivers with MAP (Pickup, et al., 2006). If people then use those MAP contaminated lakes and rivers recreationally or consume water from them, they will then be infected with MAP. MAP is associated with causing Crohn’s disease in humans, therefore if lakes and rivers are contaminated with the pathogen MAP it can have serious negative impacts on human health (Rhodes, et al., 2012). Sediments from 9 out of 10 lakes receiving inflow from catchments in the Lake District tested positive for MAP (Pickup, et al., 2006). In addition, asample of effluent taken from the Ambleside sewage treatment works tested positive for MAP. Ambleside sewage treatment works discharges their effluent into Lake Ambleside, which then discharges into Lake Windemere. Lake Windemere is used for recreation and can be used as a drinking water supply during periods of drought. Therefore, there is potential for humans to become infected with MAP, negatively impacting their health. The MAP organism will then end up back at the sewage treatment plant, allowing it to cycle through the population.

Control and prevention of microbial contamination of rivers and lakes?

Waterborne diseases are controlled through a set of standards to which water supplies must keep to. This set of standards is a definition of the safe levels of contaminants which are allowed to remain in the water depending of what the water supply is used for (Bridge, et al., 2010). The water supplies are regularly monitored to ensure that the standards are met and if they are not met then penalties are given (Bridge, et al., 2010).
You can explore the issue with the cause and effect essay on pollution. Although these standards have proved highly effective at reducing waterborne disease outbreak, these standards are only focussed on faecal indicator organisms rather than disease-causing organisms (Bridge, et al., 2010). Faecal indicator organisms are mostly coliforms which are usually non-pathogenic whereas disease-causing organisms are organisms which are known to cause disease when encountered, such as Escherichia coli and Campylotoxin (Bridge, et al., 2010). This bias of the standards is largely due to the fact that coliforms are easier and cheaper to detect in water samples than disease-causing organisms (Bridge, et al., 2010).

However, it has been proven in the past that if clear links can be made between a specific waterborne pathogen and a disease in the human population, then this does result in action from policymakers and industry within the water section (Bridge, et al., 2010). Colleges and modern educational institutions can write essays on the environment and make a great contribution to modern research. This was displayed in the United Kingdom when a link was found between Cryptosporidium in drinking water and outbreak of the disease Cryptosporidiosis (Bridge, et al., 2010). This resulted in action by the policymakers to ensure that Cryptosporidium was removed from drinking water (Bridge, et al., 2010). Long-term surveillance of cryptosporidiosis outbreaks has shown a reduction in the number of cases (Bridge, et al., 2010). In order to prevent future outbreaks of diseases caused by waterborne pathogens in developed countries, it will require communication and collaboration between health and water sector policy makers, industries and research agencies in order to develop a robust, widespread surveillance of waterborne diseases (Bridge, et al., 2010).

Sewage treatment plants act to prevent microbes from entering rivers and lakes.

Microbial contamination of lakes are rivers which are used as a source of drinking water is controlled by water treatment plants in developed countries. Water treatment plants aim to remove all pathogenic microbes from the water that risk causing harms to humans who consume the water. However, as cryptosporidium travels in the water as spores it is particularly difficult to remove from the water. This was a problem for Lake Thirlmere which supplies drinking water to half of Manchester. In order to combat this problem United Utilities built a better treatment works in Manchester in order to completely filter the Cryptosporidium out of the water because it gets to homes. They carry out frequent tests for Cryptosporidium and if one Cryptosporidium cyst is found in 1000 litres of water, they will close the whole supply until its cleared out completely. In Sidney, Australia Cryptosporidium is a large problem and so in order to manage this they have a 50 kilometre exclusion zone from all animals around their reservoirs.


To conclude, lakes and rivers are subject to a vast variety of ways in which microbes can enter. The main ways in which they enter is through human faecal contamination, via sewage treatment plants, septic tank over flow and sewage spills, and animal faecal contamination, via surface runoff.