In the UK, we are fortunate to have the luxury of water running directly into our homes and buildings.

But how does it get there?

Water passes from rivers, reservoirs and lakes into public treatment facilities. When the water is at the treatment plant, it is cleaned and filtered. From here, it is distributed to homes, schools, hospitals, and commercial and industrial buildings.

At this point, the water is usually fresh, clean and safe. But, it may not be contaminant-free.

The entire water distribution system is prone to multiple species of bacteria, algae, invertebrates and viruses. Even perfectly safe water contains millions of non-pathogenic microbes in every glass. 

Some of these contaminants are harmless to human health. However, some are still dangerous. 

Pathogens such as E.coli, Giardia, and Cryptosporidium can cause gastrointestinal problems and flu-like symptoms. 

There is also the risk of Legionella bacteria, which can lead to the potentially fatal Legionnaires’ disease.

The way water is supplied to our buildings, the quality of the water we drink, and the way factories, plants and businesses store and distribute their water, are therefore protected and controlled by a range of regulations, treatments and processes. 

And businesses have a responsibility to meet these requirements.

Get it wrong, and there can be critical damage to performance and reputation. and you can critically damage your performance and reputation. 

Get it right, and you can dramatically improve your safety records, operational efficiencies and the quality of your customers’ and employees’ experiences.

Drinking water quality is something we take for granted in the UK. But it is still the preoccupation of employers, site facility managers and water hygiene technicians. 

As we’ve seen, drinking water sources may be subject to contamination. Especially if your drinking water is fed from an alternative source, such as a borehole.

The greatest risk to human health is from waterborne pathogens, viruses and infections. 

These exist primarily between water entering our buildings and the building water distribution system within it, as well as in the last few metres before the point of delivery, i.e. taps and showers.

Factors that influence drinking water quality - and how to manage them

1. The microbes in our water distribution system

Some microbes naturally exist in our water distribution systems. But they only cause illness to humans in certain conditions. 

If microbes such as E. coli are found in water, it indicates that pathogenic microorganisms may have entered the water distribution system. 

A common characteristic of microbiological communities in water distribution systems is, given the right conditions, their propensity to form biofilms. These can become highly attractive host environments for opportunistic pathogens.

These opportunistic pathogens, such as those listed below, can cause infection, especially in children and vulnerable people with weak or impaired immune systems.

  • Non-tuberculous mycobacteria (NTMs) - can cause pulmonary and lymphatic disease, skin ulcerations and other health issues
  • Legionella pneumophila - the causative agent of the severe and potentially fatal Legionnaires’ disease and the milder variation Pontiac fever
  • Pseudomonas aeruginosa - can infect ears, skin, eyes and in some cases, cause pulmonary disease
  • Escherichi Coli (E. Coli) - can cause nausea, vomiting, abdominal pain and diarrhoea if consumed in contaminated water
  • Campylobacter Jejuni - can be found in contaminated drinking water and cause infections with symptoms of cramping, diarrhoea, fever and pain
  • Hepatitis A - can be found in contaminated drinking water and cause symptoms including dark urine, jaundice and stomach pain
  • Giardia Lamblia - a waterborne parasite that causes nausea, cramps, gas and diarrhoea
  • Salmonella - a common pathogen that can be infected through water and food ingestion and that can cause chills, fever, headaches, diarrhoea
  • Cryptosporidium - a parasite that spreads through contaminated drinking water that can cause severe pain and painful diarrhoea

Many biofilms in water distribution systems pose no significant threat to human health. But they can still cause physical damage, such as corrosion of pipes and blocking intake valves. 

These biofilms can also break down chemicals used to minimise microbial growth, while others may release nutrients that help sustain pathogens in water distribution systems.

Controlling microbiological activity:

Common alternative drinking water treatment strategies often target biofilm formation, without sometimes fully understanding what microbes may exist within your own water distribution system. 

Water treatment chemicals such as chlorine, for example, can be used to kill pathogens.

However, some pathogens, such as mycobacterium avium, are resistant to chlorine. Some disinfectants may also further promote the growth of pathogens.

The only way to check the water quality is being maintained is to monitor the microbiology and bacteria in the water. If required, the most appropriate methods of primary disinfection and secondary disinfection can then be selected. 

2. Pipe material and age

Water pipe material utilised will often vary from building to building and within individual systems. The fixings and installation quality can dictate system integrity, corrosion rates, flow and pressure. 

The composition and condition of the pipes can influence what chemicals may be released into the system and the types of bacteria that colonise within water distribution systems and on pipe surfaces.

Some pipe materials may break down and release biosource compounds, such as iron, hydrogen and phosphate, that can encourage biofilm growth and bacteria to multiply.

Biofilms coating the interior surfaces of water distribution pipes usually develop slowly and can take years to reach maturity. Older pipes are therefore more prone to developing large amounts of scale and rust.

Reducing corrosion and scale in water pipes:

Water softeners can be used to reduce corrosion and scale. 

Water treatment chemicals can also be used to coat the interior of water distribution pipes, which controls corrosion and scale and destroys biofilms. 

Some phosphates, for example, achieve this by stimulating bacterial biofilm growth and re-regrowth. Some silicates, on the other hand, work by inhibiting biofilm growth.

What is a biofilm?

A biofilm is a layer of microorganisms which forms on surfaces in contact with water. The presence of biofilms in water pipe networks can have a negative effect on water quality and cause operational problems.

Biofilms can be responsible for increased bacterial levels, reduction of dissolved oxygen, taste and odour changes, as well as problems due to iron or sulphate-reducing bacteria and reduced life of materials.

Microorganisms that form biofilms include bacteria, fungi and other organisms such as larvae and crustacea.

One of the biggest concerns with biofilms in drinking water systems is the growth of coliform bacteria in the pipe network.

Breaking down biofilms:

  • GENOX generating NEUTHOX® is a particularly effective way of controlling biofilm. Approved for drinking and process water, it is equally effective across most types and ages of water system pipe. 
  • Ultralox® is also effective at breaking down the biofilms that harbour pathogens.

3. The physical integrity of the water distribution system

If there is a break or a leak in a pipe, it can lead to low-pressure events which cause bacteria to cling to surfaces.

It may also encourage biofilm growth. And any sediment that enters the system can serve as a source of nutrients that cause bacteria to grow.

Alterations to the pipework can also impact the system integrity. 

4. Storage facilities

The type of storage facility can impact hydraulic pressure and water age. 

Water tanks are common habitats for water microbes. Systems with water tanks that do not turn over frequently can encourage microbiological activity. 

This can cause the water supply company’s disinfectant concentrations to drop and sediment to accumulate and influence microbial growth.

5. Water chemistry

The source, stability and temperature can all impact water quality. 

Source water

Nutrients in the water can influence water microbiology. Microbes can feed on the compounds, carbons and nutrients found naturally within water. This becomes more important with water re-use as disinfection concentration becomes impaired over time. 

Chemical stability

Once water has been treated, it changes and can start to respond in ways that favour microbiological growth. For example, residual disinfectant effectiveness can decrease at rates depending on water temperature and disinfectant dosing. 

Temperature

Temperature can heavily influence the microbiology in water. Different organisms respond differently to changes in temperature and seasonal temperature changes. This is why disinfection regimes are often stepped up or changed in hotter periods.

Testing for water chemistry:

There are increasingly sophisticated and sensitive water testing and laboratory analysis services that can help determine what may be happening in your water chemistry. This can lead to better decision-making when it comes to water treatment.

Your responsibilities as a duty holder

Every business needs to understand and carry out their legal duties regarding the control of legionella – the bacterium that causes Legionnaires’ disease, a lung infection that can be fatal.

Legionella Risk Assessment

In the UK, there is an obligation for anyone responsible for maintaining water systems in buildings to mitigate the risk of Legionella. 

This is supported by prosecutions and fines for duty holders found to have failed to comply with regulations and endangered human health.

Employers, Health and Safety managers, and those in control of premises with a duty of care for others are required to:

  • Identify and assess sources of risk
  • Prepare a programme to prevent or control risk
  • Implement, manage and monitor precautions
  • Keep records designed to manage, monitor and control Legionella risk and potential danger to human health.

A Legionella Risk Assessment is obligatory - it's a legal requirement under the Health and Safety at Work Act 1974. It also has to be conducted by a suitably trained person who would be regarded as "competent" in a court of law.

Consider a specialist company offering Legionella Risk Assessments or a Legionella Review of Risk Assessments carried out in-house. The member directory of the Legionella Control Association is a good source of information.

ACoP L8 Compliance

Legionnaires’ disease: the control of legionella bacteria in water systems is an approved Code of Practice (ACOP). The current edition is L8 (fourth edition) and was published in 2013. It is commonly referred to by the shortened acronym ACoP L8.

Business owners can face prosecution for breaching health and safety law if they don’t follow the advice provided in the code.

ACOP L8 is “aimed at duty holders, including employers, those in control of premises and those with health and safety responsibilities for others, to help them comply with their legal duties in relation to legionella. These include identifying and assessing sources of risk, preparing a scheme to prevent or control risk, implementing, managing and monitoring precautions, keeping records of precautions and appointing a manager to be responsible for others.”

Disinfection methods

Disinfection is an important step in ensuring that drinking water is safe.

UK water companies are required to meet the EU Drinking Water Directive by disinfecting public water to the point of supply. They have to kill or inactivate disease-causing organisms in the water supply.

There are two principles of disinfection:

Primary disinfection: Once the water has been filtered, a disinfectant such as chlorine or chloramine is added in order to kill any remaining bacteria and viruses.

Secondary disinfection: Provides enhanced protection by preventing the regrowth of microorganisms harmful to human health between incoming public water supply to your building and the water distribution system inside your building right up to point of use, i.e. taps, showers etc.

There are many uses of water in industry. Large quantities are required for the cooling of products and equipment, for process needs, for boiler feed, and for sanitary and drinking water supply.

But water entering an industrial plant needs to be treated before it can be used in industrial processes.

If unclean water is used in the production process, it can negatively affect product quality. 

Bacteria in the water can also reduce the efficiency and operating life of boilers and other systems.

And when left untreated, bacteria can grow, including legionella.

Industrial water treatment ensures the water quality is suitable for use. It also reduces energy consumption and improves operational efficiency.

Benefits of industrial water treatment 

Industrial water treatment can benefit a wide range of industries, including many areas of manufacturing, food and beverage, healthcare, and pharmaceuticals.

  • Manufacturing - Water treatment is critical for improving the lifetime of equipment, increasing operational efficiencies and reducing manufacturers’ environmental impact. It is required for many areas of manufacturing, including aerospace and defence, automotive and components, building and construction, electronic goods, plastics, rubber and textiles.
  • Food and beverage - Water is used in many parts of the day-to-day operations in the food and beverage industry, from cleaning raw materials to inclusion in recipes.
  • Healthcare - Properly treated and managed water can have a significant impact on the health, safety and comfort of patients, staff and visitors.
  • Pharmaceuticals - The pharmaceuticals industry require higher grades of water than many other sectors.

Risk factors and how to manage them

There are four main problem areas that industrial water treatment seeks to manage:

1. Scaling

Scaling is the build-up of unwanted material on solid surfaces.

Scale deposits are formed when the chemistry and temperature conditions are such that the dissolved mineral salts in the water precipitate.

The scale deposits can be free-moving, like fine silt, or can form in layers on the metal surfaces of the system.

In cooling towers, scale can be a harbouring ground for bacteria to breed, including legionella.

In closed systems, the primary problem with scaling is the inhibition of the heat transfer process and blocking of tubes, causing low flow.

Scale inhibitors and water softeners can be used to minimise the build-up of scale.

2. Corrosion

Corrosion is a naturally occurring process that converts a refined metal (such as iron) to oxidise or causes a refined metal, which gradually causes the integrity of the plant equipment to become compromised.

The problems caused by corrosion are similar to scale. But corrosion can also lead to leaks, which can result in catastrophic failures within a pressurised system.

The consequences of corrosion are many and varied:

  • Reduction of metal thickness
  • Hazards or injury rising from structural failure
  • Down Time of equipment
  • Reduced values of goods
  • Contamination of fluids in vessels or pipes
  • Escape of contents of vessels or pipes
  • Loss of technically important surface properties of a metallic component
  • Mechanical damage to valves/pumps or blockage of pipes by solid corrosion products
  • Added complexity of equipment required to withstand corrosion

Corrosion inhibitors can be added or pre-treatment used to reduce the rate of corrosion.

3. Microbiological activity

Microbes thrive in untreated cooling water. Fungal spores and other material can collect in the water if not treated with biocides.

The severe and potentially fatal Legionnaires’ disease has also often been associated with unmanaged water systems.

To control microbiological activity:

  • Biocides (chemical substances or microorganisms intended to destroy, deter or exert a controlling effect on any harmful organism) can be added to the water to effectively control microbial growth.
  • Disinfection methods can kill harmful microbes and pathogens in the water.
  • Regular monitoring - the best way to ensure water quality is maintained is by continually monitoring the microbiology and bacteria in the water so the most effective disinfection solution can be selected.

4. Disposal of residual water

Certain industrial and manufacturing processes can cause substances to get carried away with water when it is disposed of.

The presence of these substances can be toxic if recycled back into the plant without being treated.

In many cases, effluent water from one process can be reused in another process if given suitable treatment.

Industrial water treatment systems

Industrial water treatment can be broken down into three primary areas.

1. Boiler water systems

Boiler water systems are an essential component in many industrial applications where the primary purpose is to transfer energy from one part of the system to another.

If a boiler system is not maintained or the water is left untreated, it can lead to serious issues that will affect its integrity and performance.

A well-managed boiler water treatment programme will:

  • Optimise costs and operational efficiencies
  • Reduce downtime
  • Achieve water and energy savings
  • Maintain steam quality Increase reliability and safety

Boiler water treatment solutions include:

  • Commercial water softeners and other pre-treatment plant
  • Chemical scale inhibitors
  • Corrosion inhibitors
  • Steam conditioners

2. Cooling systems

Cooling systems are susceptible to corrosion, scaling, fouling and microbiological contamination.

In fact, many outbreaks of Legionnaires’ disease have been traced to poorly managed cooling towers.

A well-managed cooling system water treatment programme will:

  • Optimise costs and operational efficiencies
  • Reduce downtime
  • Achieve water and energy savings
  • Increase plant reliability
  • Improve safety and regulatory compliance

Cooling system water treatment solutions include:

  • Specialist cooling water corrosion inhibitors
  • Pre-filtration of the water
  • Cooling water treatment chemicals
  • Side stream filtration
  • Periodic cleaning and disinfection
  • Regular monitoring and testing for Legionella

3. Closed circuit systems

Closed circuit systems provide heating or cooling to buildings, manufacturing and industrial processes.

They are used in a variety of industrial processes, most commonly in heating systems.

They have a number of advantages over open water systems, including greater efficiency and lower maintenance requirements. But it would be wrong to think of them as maintenance-free.

As a ‘closed loop’ or ‘closed system’, they are not normally susceptible to outside contaminants.

But, they can still be affected during routine maintenance and refurbishment work by factors such as corrosion and microbiological contamination.

Closed circuit system water treatment solutions include:

  • High-performance corrosion inhibitors
  • Oxygen scavengers
  • Broad-spectrum biocides

The importance of control and management in closed circuit systems

Testing of water quality is an essential part of the industrial water treatment process, especially in closed circuit systems which are impossible to view from the inside.

Poor management can lead to scale and corrosion issues, reduced efficiency and even damage to critical systems.

Monitoring can be completed by physically removing and testing representative samples of the water. Inline and online monitoring systems are also now becoming more prevalent.

There are two elements to maintaining an efficient closed circuit water system:

  1. The integrity of the system - measuring water flow and pressure for fluctuations will help determine if there are any issues within the physical system.
  2. The water chemistry - a lowered pH value can indicate bacterial growth or a leak, bacteria can create biofilm which can coat surfaces making them less efficient, and contaminants can result from unseen corrosion.

Water analysis

Performing water analysis on a regular basis can help you keep on top of your closed system water treatment levels.

A BSRIA Closed System Water Analysis - BG 50/2015 is a comprehensive set of tests that cover a full range of chemistry and micro-analysis.

A standard closed system would typically look at:

  • pH
  • Alkalinity
  • TDS
  • Nitrate
  • Tannin
  • Molybdate
  • Phosphate
  • Glycol % (if type known)
  • Iron
  • Aluminium
  • Copper

Monitoring and control of water systems is essential to ensure the water in your buildings is safe for drinking and use in industrial processes. 

Monitoring water treatment systems typically involves conducting chemical tests and comparing the results to specific chemical control limits.

The testing frequency can vary from once per month, to once per day to even once per hour.

Routine water testing

Water testing is an essential part of asset management, ensuring system integrity, water hygiene risk management and Legionella control.

Routine water testing allows duty holders to monitor for contaminants, corrosion and scale, and identify when a new approach to treatment is required to tackle these problems effectively.

What to test for:

  • Total viable count (TVC) - estimates the total numbers of microorganisms, such as bacteria, yeast or mould species and gives an overall indication of the general water quality
  • Legionella - the bacteria that causes Legionnaires’ disease
  • Pseudomonas - bacteria that can lead to damaging blockages and corrosion of pipework
  • Chemical make-up of water 
  • Physical parameters - testing for total and suspended solids
  • Metal parameters - testing for metal determines asset wear, system integrity and water quality
  • Corrosion, scale and contaminants - reveals water quality, underlying system parameters and safety

Deciding which disinfection solution is right for you depends on a number of criteria, including your objective, application, water usage, and flow rates.

In all likelihood, a combination of techniques will be required for your building or water distribution system.

Water treatment techniques

The following water treatment techniques can be employed to deal with bacteria in water: 

Chlorination

Chlorine is added to water for disinfection and control of microbiological contaminants.

It is added to water by public water companies making it safe to drink.

Today, forms of chlorine such as Ultralox40® are widely used as methods of disinfection and secondary disinfection of water distribution systems within buildings.

Ultraviolet Light (UV)

UV disinfection is a simple, low cost and popular method of water disinfection. 

It is efficient at killing bacteria, viruses, fungi, protozoans and cysts that may be present in water. But cannot be used to remove gases, heavy metals and particulates, and bacteria can hide behind larger debris.

UV is often used in conjunction with other water disinfection methods.

Ozone

Ozone is produced when oxygen is exposed to high-voltage current.

It can destroy viruses, bacteria and microbiology, while also removing iron, sulphur and manganese. 

Ozone is a quick disinfection method and then rapidly decomposes, cutting down on the introduction of harmful disinfection by-products and foul tastes or odours associated with some chlorination.

Chlorine Dioxide

Chlorine Dioxide (ClO2) production is a particularly effective microbiological control, Legionella control and primary and secondary water disinfection measure.

For reasonable quantities, it requires generation and is suitable for biofilm eradication, membrane systems and filtration, water distribution systems, cooling towers, hospitals, hotels, horticulture, breweries, dairies and sites with hazardous chemical restrictions.

ClO2 should be the preferred method of ensuring purity in your water system. This is because it does not form undesirable disinfection by-products, has 2.6 times the oxidative capacity of chlorine, and will react in a third of the time - meaning at typical treatment levels, it is less corrosive to pipes and equipment.

Traditional Sodium Hypochlorite

Sodium Hypochlorite (NaOCI) is one of the most commonly used compounds for water purification, especially across large scale surface purification, bleaching, odour removal and water disinfection in cooling towers. 

It is a cost-effective method, simple to dose, and can be safely stored and transported. However, it can be hazardous and corrosive in concentration and does not deactivate Giardia Lambia and Crptosporidium. It is most effective in waters <ph8.

Water treatment innovations

Today, there are a variety of innovative technologies that can improve the safety and reliability of your water systems.

These include:

Chlorination (Hypochlorous Acid Generation)

The GENOX generator produces a colourless liquid which is generated on-site and requires no mixing or handling of toxic chemicals. Direct electrolysis of brine, creates an oxidant NEUTHOX® on demand.

Advantages:

  • Low-cost biocide
  • No hazardous chemicals are mixed, stored or handled
  • Inexpensive to operate and maintain
  • Particularly effective as a disinfectant against bacteria, waterborne pathogens and microbes
  • Prevents biofilm reforming in water pipes
  • Effective legionella control
  • NEUTHOX® contains hypochlorous acid as an active agent, the same style defence mechanism produced by the human immune system to fight infection

Limitations:

  • Should not be stored for more than one month
  • Best generated on-demand in real-time

Chlorine Dioxide (new style Catalytic Generation) or ClO2IX

A universally effective primary and secondary disinfectant, that doesn’t have the usual limitations of chemical mixing, handling or storage.

Advantages:

  • The disinfectant effect is independent of pH
  • Sustained-release means long-term stability in water piping systems
  • Destroys biofilms in pipework and tanks, offering reliable protection against legionella 
  • High yield
  • Low risk from chemical handling and mixing toxic ClO2 gas

Limitations:

  • Less effective in very hot water systems

Chlorine Dioxide – WRAS Approved Pureox 3500

A universally effective primary and secondary disinfectant, generated using a patented Safe Generation per Batch (SGB) technology.

Advantages:

  • The disinfectant effect is independent of pH
  • Sustained-release means long-term stability in water piping systems
  • Destroys biofilms in pipework and tanks, offering reliable protection against legionella 
  • >98.6 conversion efficiency of yield

Limitations:

  • Residence time of treated water in drinking water system needs to be minimal to avoid a build-up of oxidants

Ozonation

Ozonation is a water treatment process that destroys microorganisms and degrades organic pollutants through the infusion of ozone, a gas produced by subjecting oxygen molecules to high electrical voltage.

Advantages:

  • Requires a shorter contact time and dosage than chlorine - ozone can be added at several points throughout the treatment system for both primary and secondary disinfection
  • Odour and taste-neutral
  • Enhances the coagulation and flocculation process
  • Effective in large scale effluent treatment
  • Can reduce some disinfection by-products

Limitations:

  • Ozone is an unstable gas and must be generated on-site
  • Use requires an additional disinfection control because ozone has a short life, is unstable and often has limited residual effect in water
  • Capital cost is relatively high
  • Operating is complex
  • Can be corrosive if not used appropriately

Ultraviolet Light (UV)

Ultraviolet (UV) radiation is generated by a special lamp. When it penetrates the cell wall of an organism, the cell’s genetic material is disrupted and the cell is unable to reproduce.

Advantages:

  • Effectively destroys bacteria and viruses
  • Produces no known toxic residuals
  • Requires short contact times
  • Equipment is easy to install and maintain

Limitations:

  • May not always reliably inactivate Giardia lamblia or Cryptosporidium cysts
  • Should be used only by groundwater systems not directly influenced by surface water
  • Unsuitable for water with high levels of suspended solids, turbidity, colour or soluble organic matter, as bacteria may pass through being shielded from the UV

Ultralox40®

Ultralox40® is a regulated, stable, and highly effective low concentration form of chlorine that works as a fast-acting biocide. 

Advantages:

  • Only one chemical required
  • No generator required
  • No danger of chlorite overdose
  • Low concentration
  • Fast-acting biocide particularly effective against bacteria and waterborne pathogens, including legionella and pseudomonas
  • Can be dosed into incoming mains, break tank or via fixed or mobile control system
  • Low hazard
  • Long shelf-life

Limitations:

  • Primarily for smaller applications or critical applications (e.g. acute hospital systems)
  • May impact pH
  • May generate trihalomethanes (THMs) in drinking water