Water Microbiology, Common Contaminants and Water Treatment Methods

A “contaminant” is any physical, chemical, biological, or radiological substance in water. Essentially, anything other than water molecules is a contaminant. Drinking water may contain small amounts of contaminants. Some can be harmful at certain levels, while others are harmless. This blog post covers bacteria, viruses, and common water contaminants. It also discusses disinfection methods to manage them.

What is Water Microbiology?

Water microbiology studies micro-organisms in water like bacteria, fungi, yeast, viruses, protozoa, and algae. In water treatment, bacteria are the main concern since some can harm humans. If unchecked, bacteria growth can lower water system effectiveness, leading to costly business impacts.

Understanding Drinking Water Microbiology

Safe water contains millions of non-pathogenic microbes per glass found in both bottled and tap water. The water distribution system, including reservoirs, wells, tanks, and pipes, hosts various harmless bacteria, algae, invertebrates, and viruses. However, some, like E. coli, Giardia, and Cryptosporidium, can cause gastrointestinal issues and flu-like symptoms similar to those from undercooked or improperly stored food. Water companies must protect water up to the supply point. Commercial building managers handle water safety and hygiene from the source to the supply point. Microbiological and organic contaminants might not be detected by sight, smell, or taste. Proper water hygiene and disinfection techniques are crucial to safeguard health from common bacteria, viruses, and contaminants.

Bacteria in Water

Bacteria in water can use many compounds as food. Certain strains can metabolise organic material, sulfate, and even cyanide. Oxygen levels affect bacterial growth. Some bacteria need oxygen (aerobic), while others grow without it (anaerobic). Water temperature influences bacterial growth. Most bacteria thrive between 15°C and 40°C, but some can grow at 5°C and others at 60°C.

Virus Issues and Pathogens in Water

Parasitic infectious microbes, made mostly of protein and nucleic acids, can cause diseases in humans. Pathogenic viruses lead to gastroenteritis and hepatitis. These viruses are the main targets for detection, filtration, and removal through water disinfection, sanitisation, and purification.

Parasites in Water

Parasites in water can cause serious health issues. They are often found in contaminated water sources. Parasites like Giardia and Cryptosporidium can survive for a long time in water. Ingesting such contaminated water can lead to gastrointestinal diseases. It is essential to apply effective filtration and disinfection methods to remove these parasites. Proper treatment ensures safe and clean drinking water, protecting public health.

Common Contaminants in Water

Water can contain several common contaminants, including:

Aluminium – Al, Al3+, Al(OH)3

Aluminum is the most common metal on earth. It often appears as aluminium chloride, hydroxide, oxide, or sulfate. It can also be found mixed with organic matter and other elements. Aluminium does not give water any noticeable taste or smell. However, when levels exceed 0.2 PPM, it can make water appear hazy or bluish.

Ammonia – NH3, NH4+

In water, ammonia is present as ammonium and a hydroxide ion but is usually just called ammonia. It typically comes from dead organic material, industrial waste, and agricultural runoff in raw water. Ammonia is not usually harmful to humans but can affect chlorine disinfection. Nitrifying bacteria in soil can change ammonia into nitrite and nitrate through nitrification.

Arsenic – As, As(III)

Arsenic is a natural element found in the earth’s crust and the environment, including air, water, and land. People mainly encounter arsenic through water, as it appears in a tasteless and odourless form. Drinking water or consuming food made with arsenic-contaminated water are major exposure sources. The WHO estimates that over 140 million people in more than 50 countries drink water with arsenic levels exceeding 10 μg/L. Arsenic exposure can have both immediate and long-term health effects.

Barium – Ba, Ba2+

Barium is a naturally occurring alkaline metal. It is not found in its elemental form but combined with other elements. Common barium compounds include barium sulfide, chloride, oxide, hydroxide, sulfate, acetate, and carbonate. Barium, mainly as barium sulfate and carbonate, occurs in nature as ore deposits. Leaching and erosion of these deposits can contaminate groundwater.

Cadmium – Cd, Cd2+

Cadmium is a metal found in sulfide ores that contains zinc and lead. It is used in industries for anticorrosive plating of steel, electric batteries, electronic parts, and nuclear reactors. The picture shows natural cadmium sulfide. Cadmium usually doesn’t enter water naturally. Industrial and agricultural activities are the main sources of cadmium pollution in drinking water. Contamination can happen when cadmium leaches from zinc in galvanised pipes or solder in fittings, water heaters, coolers, and taps. Acute cadmium toxicity is rare. However, long-term exposure is linked to kidney disease, protein, phosphorus, and calcium loss, leading to kidney stones and osteomalacia.

Chloramines – NH2Cl, NHCl2, NCl3

Chloramines form when chlorine and ammonia mix in water, remaining as “residuals.” Their formation depends on concentrations and water’s physicochemical properties. Chloramines disinfect drinking water and are used in pipes between treatment plants and homes due to their long-lasting effect. They provide moderate protection against bacteria and low protection against viruses. Chloramines can change the taste and smell of water at low concentrations. Levels below 5 mg/L and sometimes as low as 0.3 mg/L can be detected by individuals, according to the WHO. There is no concrete evidence linking chloramines to health problems, though the WHO discusses possible connections to methemoglobinemia and certain cancers.

Chromium – Cr, Cr(III), Cr+3

Chromium is found in soil and rocks in different oxidation states. It is used in industries for chrome plating, dye and textile production, leather tanning, Portland cement, stainless steel, welding, and wood treatment. Water pollution from chromium can happen due to leaching from topsoil or rocks and industrial contamination. Hexavalent chromium (Cr[VI]) in drinking water is the most dangerous as it is highly toxic to humans. Contaminated water can lead to allergies, contact dermatitis, and kidney and liver toxicity. It may also cause gastrointestinal issues, sperm damage, and anaemia.

Copper – Cu, Cu2+

Copper is a versatile metal widely used in manufacturing for wiring, pipes, valves, and more. It’s present in all water types, with concentrations in municipal systems varying based on water properties and plumbing. Corrosion of copper pipes often causes contamination. People consume 0.1-1 mg of copper from water daily, but higher levels can lead to health issues. Copper in water can cause a turquoise colour and metallic taste.

Lead – Pb, Pb(PH)2, PbCO3, Pb2O

Lead, a common heavy element, contaminates water mainly from old plumbing systems. The WHO estimates over 240 million people globally are exposed to lead-contaminated water, contributing to over 850,000 deaths annually. An adult typically ingests 5 µg/l of lead daily from water. Lead exposure can cause central nervous system issues, kidney disease, anaemia, abdominal pain, constipation, gum hyperpigmentation, and various hematologic symptoms.

Mercury – Hg, Hg2+, Hg1+

Mercury is a natural metallic element found in the environment. Its use in manufacturing is decreasing due to environmental concerns and regulations. In water, mercury levels are usually below 0.5 μg/L. Drinking water is a minor source of mercury exposure unless there’s significant pollution. Acute mercury poisoning can cause gastroenteritis and renal failure. Chronic exposure can lead to Minamata disease and fetal defects.

Radium – Ra, Ra2+

Radium is a naturally occurring radioactive element and a known carcinogen. It is usually found at low levels in rocks, soils, and groundwater. Groundwater can have high radium levels depending on local geology. Deep bedrock aquifers used for drinking water can sometimes exceed regulatory standards.

Water Treatment Methods

Temperature control is the primary defence against bacteria, viruses, and other contaminants, but it may not always be enough in complex water systems. Use these water treatment methods to ensure the water is clean and safe.

Chlorination

Chlorination involves adding chlorine to water to disinfect and control microbiological contaminants. It also helps oxidise impurities like dissolved iron, manganese, and hydrogen sulfide, making water clearer. Public water companies add chlorine to ensure drinking water is safe. Ultralox40® is a chlorine form approved for potable water and is effective for better water quality and hygiene and pipework treatment, swiftly eliminating Legionella and other microbes. It is extensively used in NHS facilities.

Ultraviolet Light (UV)

UV disinfection is a simple and low-cost method to purify water. This method uses light at a specific wavelength to kill microbes in water. UV systems are effective for disinfecting water in underground tanks, like those in sports stadiums, before using it for irrigation. UV eliminates bacteria, viruses, fungi, protozoans, and cysts in water. However, this method may not remove all contaminants, such as gases, heavy metals, or particulates, so combining it with another treatment technique is often recommended.

Ozone

Ozone forms when oxygen interacts with high-voltage current. It can eliminate viruses and bacteria and remove iron, sulfur, and manganese from water. Ozone disinfects quickly and decomposes rapidly, reducing harmful by-products and unpleasant tastes or odours linked to some chlorination methods.

Chlorine Dioxide

Chlorine Dioxide (ClO2) is an effective tool for microbiological control, Legionella control, and disinfection of water supplies. It must be generated on-site, as it can’t be purchased in a drum. ClO2 is ideal for removing biofilm and is suitable for membrane systems, water distribution, cooling towers, hospitals, hotels, horticulture, breweries, dairies, and locations with hazardous chemical restrictions. Its sustained release offers long-term stability in water systems, good conversion rates, and low chemical handling risk. However, it is less effective in very hot water systems.

Controlling Bacterial Levels in Water Systems

Bacteria levels in water systems can be controlled by adding biocides or using temperature control. Our technical team is ready to help you find the best treatment plan for your water system. Managing bacteria growth is crucial in water treatment, including drinking water, water services, process waters, closed circuits, recreational waters, and open cooling systems.

How to Choose the Right Water Treatment Method for Your Water Distribution System?

Choosing the right solution depends on your goal, how the water is used (drinking vs. industrial), and flow rates. You may need a mix of techniques for your building or water system. For more details on water chemistry, water analysis, microbiology, or water testing, contact our Confort Services Group professionals.

FAQs

What is the job of a water microbiologist?

A water microbiologist conducts routine microbiological tests on water samples in a lab. They assist with more complex investigations and analyses and participate in specific research project tasks. They also perform other related duties as needed.

What are the types of microorganisms in water?

In water, you can find many infectious microorganisms. Bacteria like Shigella, Escherichia coli, Vibrio, and Salmonella are present. Viruses such as the Norwalk virus and rotaviruses are there, too. Protozoans like Entamoeba, Giardia, and Cryptosporidium may also be found.

Why is water microbiology important?

The main goal of drinking water microbiology is to prevent waterborne diseases. Achieving this requires proper water treatment and control practices. Monitoring their effectiveness is also important.