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Manufacturers require a certain level of water quality to produce their goods. The exact standards vary from industry to industry, but in all cases, water used in manufacturing has to be free from biological and mineral contaminants. High water standards are not simply a matter of legal compliance. They also underpin consumer confidence in many of our industries, especially cosmetics and pharmaceuticals.

Deionisation is an advanced water treatment process that uses the polarity between different ions to strip unwanted contaminants out of the water. Deionisation water treatment systems are extremely effective and are widely used by businesses in all industrial sectors.

The Benefits Of Water Purification

Investing in a deionisation system allows you to meet all the internationally recognised water standards relevant to your industry, including:

  • British Pharmacopoeia
  • European Pharmacopoeia
  • Japanese Pharmacopoeia
  • United States Food and Drug Administration (FDA)

Crucially, a good purification system also helps you avoid common water problems, such as bacterial contamination; which can cause expensive downtime and missed production targets.

Water purification systems are our area of expertise at Wychwood Water. Our job is to find you a cost-effective solution that aligns with your business goals and gives you access to the purified water you need. We understand manufacturing and know that it is a delicate balance between resources and deadlines. We are here to help you avoid many of the common water treatment problems that plague businesses,, and make your operation more profitable.

This is our guide to deionised water treatment systems. We will explain how these systems work, and how they complement and differ from other systems (such as Reverse Osmosis). We will suggest how common – and frequently costly – mistakes with these systems can be avoided, and propose some minimum quality standards that any system should have.

Deionisation, Continuous Electro-Deionisation and Reverse Osmosis

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Deionisation is one of two main processes involved with industrial water treatment; the other is Reverse Osmosis (RO). Deionisation is then further broken down into ‘chemical,' or standard deionisation (DI), which is the most commonly used process, and Continuous Electro Deionisation, which is the preference of some industries but is a little bit more involved.

You may already know exactly what you need for your industry, or you may be a bit unclear about what each of the processes involves, so in the following three sections we provide a breakdown so you can make your mind up.

If you have any questions or want to speak to one of our qualified water purification experts, please call us now on 01993 892 211.

For a free quote, you can get in touch with our technical sales team on

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How Reverse Osmosis (RO) Works

Reverse Osmosis (RO) is an efficient, nonchemical water purification process that is commonly used across the manufacturing sector. It uses a membrane to filter contaminants out of the feed water, leaving purified water (permeate), at the end.

Many industries use RO systems in conjunction with chemical disinfection treatment. It is the most common alternative to deionisation and is a worthwhile investment decision, even if you choose to use RO alongside other purification methods.

Our Reverse Osmosis systems are some of the best on the market and operate at a reliable 70% efficiency with low energy membranes. So in other words, for every 100ml of impure water you put through the system, you get 70ml of pure water.

70% is a pretty good ratio. You may find some companies promising you 80% efficiency, but you should be careful of these, as it simply means that their systems force the membranes to work harder. The result is the membranes do not last as long and need to be replaced more frequently, thus reducing the overall cost effectiveness of the system.

You should also be very careful of cheaply marketed Reverse Osmosis systems, as not all RO processes are created equal. We have come across bargain basement systems that have an efficiency of 25% or less. These are simply not worth your money and time.

How Reverse Osmosis Works

RO systems are, in principle, very simple. They use a flat sheet membrane of a composite material that is cleanable and fouling resistant. The water is pressed through the membrane using a low-energy pump at comparatively low speeds.

Reverse Osmosis is highly effective at removing organic compounds and dissolved minerals from the water, as well as most bacteria and large viruses, as these cannot pass through the physical barrier of the membrane.

Water Pre-Treatment

However, Reverse Osmosis does not work on its own. The purification process is only as good as the pre-treatment of the water is feeding it. There are certain contaminants that will impede Reverse Osmosis, including free chlorine, calcium, and magnesium, so these need to be stripped out first.

You need to pre-treat the feed water with activated carbon to remove the free chlorine and then add a water softener to strip out the calcium and magnesium, before it can be put through the RO system.

If you fail to do this, then the free chlorine in the water will degrade the membrane and let organic contaminants through, and the calcium and magnesium will scale the membrane up, reducing its efficiency and working life.

This is the reason many industries consider Reverse Osmosis to be wasteful, time-consuming and expensive. The alternative is deionisation.

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How To Maintain Ultra Filtration Water Systems To Keep Producing Pure Water.jpgHow Deionisation (DI) Works

Deionisation is a complex, chemical purification process, which despite being more involved than Reverse Osmosis, is far more effective at removing a wide range of mineral contaminants. Deionisation uses an ion exchange process that attracts mineral impurities such as sodium and other metallic elements.

The contaminated water is treated with two different ion exchange resins to remove the impurities.

1) Negatively charged Cation resin is first added to attract positively charged ions in the water, while
2) Positively charged Anion resin attracts the negative ions.

Both resins are pre-charged with hydrogen and hydroxide before treatment. Deionisation is extremely efficient at taking out mineral and metallic impurities.

Deionisation is a tried and tested method, having been used in industry for the past 80 years. However, despite this, it is less popular than Reverse Osmosis. For this reason, many water treatment companies only offer Reverse Osmosis, whereas we offer our customers the choice of Reverse Osmosis or Deionisation, or both if necessary.

Controversies Surrounding Deionisation

There are a couple of reasons why deionisation is controversial in some quarters. Some of this boils down to the chemicals used. For instance, due to regulations, excessive chemical treatment is unacceptable in the pharmaceutical industry. Deionisation is also labelled – perhaps unfairly, as a less environmentally sustainable water treatment process than Reverse Osmosis.

However, the truth is that all water purification processes (as opposed to simple filtration) do require some kind of chemical treatment. Moreover, chemical treatments don’t have to be damaging to the environment, so long as they are managed and disposed of in a responsible and ecologically sensitive manner.

Another downside of deionisation is that it is ineffective in dealing with bacteria and viruses. It therefore needs to be used in conjunction with another purification or filtration process to get completely pure water.

None of this should put you off. Conventional Deionisers typically recover deionised water at a rate of 90% plus, which makes them a highly effective water purification system.

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How Continuous Electro Deionisation (CDI) Works

For those of you who may be squeamish businesses who are uncertain about the chemicals used in conventional deionisation, there is an alternative. This is the third main process we deal with, and is known as Continuous Electro Deionisation, or CDI. It is a popular option among pharmaceutical companies, as it allows strict compliance with FDA, EU and BP regulatory authorities.

Electrical Ion Exchange

CDI uses ion exchange resins packed in cells and sandwiched between ion selective membranes. An electrical field is then passed across the cells and the impurities removed into a reject stream. The important point is that no chemicals are used in the process. The deionisation elements are continually charged with electricity, rather than chemicals.

Benefits And Drawbacks Of CDI

This makes CDI a fairly expensive water purification method. Moreover, the water still needs pre-treatment with Reverse Osmosis to remove organic and inorganic impurities. However, the end result is an extremely pure water with almost no organic or inorganic contaminants. This makes CDI the treatment of choice for industries where absolute purity is a must, such as the pharmaceutical, electronics and power generation industries.

The Importance Of Regular Maintenance

CDI units are complex and precise systems. They have specific operational and feed water requirements that unfortunately leave them wide open to human error. When mistakes are made, the system can suffer loss of performance, damage or even be put out of action. It is therefore important that a Continuous Electro Deionisation system is thoroughly monitored and a regular schedule of maintenance and repairs put in place. By the time a problem in one of these units becomes obvious, the window of opportunity for a simple solution has often closed.

How To Avoid CDI Problems

The main way to avoid problems with your CDI unit is to make sure your Reverse Osmosis system is working properly, as this is the usual source of chemicals and other particles that can reduce the effectiveness of continuous electro deionisation.

  • Ensure that your CDI is fed with Reverse Osmosis permeate.
  • Your RO plant should be working at peak efficiency. Any issues here are also likely to affect your CDI system.
  • The water softeners you use must be removing all traces of hardness.
  • No traces of free chlorine can be present in the feed water entering your CDI plant.
  • Excessive carbon dioxide will prevent the CDI unit performing and suppress the quality of purified water produced.
  • If Co2 is in evidence, de-gasser membranes are used to remove the CO2. Excess Co2 may also be a symptom of biological contamination.
  • Lack of effective pre-treatment of water will affect the working of both the RO and CDI systems.

A Working Partnership

All of these processes work brilliantly on paper. However, as with everything in the real world, each process is subject to the whims of human error. In the following two sections we will look at where things can go wrong with deionisation and how these mistakes can be avoided. By recognising how and why these mistakes happen,they can be more easily avoided and rectified quicker when they occur.

There is no binary choice between Reverse Osmosis or Deionisation. Although they are commonly seen as an either/or decision, they can, in fact, be used as complementary processes; with mineral impurities being removed by deionisation and reverse osmosis being employed to eliminate bacterial and organic contaminations. If in doubt, one of our qualified chemical engineers will be able to help you make an informed decision.

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Troubleshooting Part One: Understanding Deionisation Resins & Chemicals

A conventional DI or CDI system will work brilliantly so long as the feed water is of the required quality, AND the resins are working properly. As noted, deionisation is a chemical process and requires the safe handling of potentially harmful chemicals. There is no reason why safe and effective chemical handling systems can’t be installed and operated.

Most problems with deionisation systems result from negligence or carelessness in storing or handling chemicals, rather than in misuse of the system itself.

Resin Sensitivity

The resins of deionisation systems are very sensitive to chlorine and chloramine, breaking down when water containing these chemicals is allowed to pass through the system. The same is true if water containing iron or debris travels through. Pre-treatment of the feed water through activated carbon, reverse osmosis and/or filtration is therefore essential.

Resin Regeneration

In deionisation, water is stripped of its impurities by pushing it through a cation and anion resin. Deionisation systems, whether in column or bed form, require regular cleaning and regeneration of the resins, which can become blocked over time by sodium, calcium and magnesium deposits. The regeneration process is carried out using hydrochloric acid and caustic soda. This makes it unsuitable for pharmaceutical facilities. Regeneration chemicals need to be of the required quality and strength to be effective. Refer to the system manufacturer for confirmation if in doubt.

Batch Regeneration

All resins in a DI system must be regenerated at regular intervals. If more than one resin becomes contaminated, regenerate each one separately. This may take a bit more time, but we recommend that batch regeneration – where several resins are treated together – be avoided. This is because treatment can be rendered inadequate if one or two resins in the batch are fouled.


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You will need to monitor the health of a DI system’s resins by consulting the onboard water monitoring device that most of them include. A digital water quality meter can also be used, but must be properly calibrated for accurate results.

Resin Life Span

Ion Exchange Resins typically have an effective working life of three years. Beyond this they should be replaced. One of the most common causes of problems is when users continue to run the system using old resins. This leads to a plethora of issues throughout your system, including:

  • Excessive use of regeneration chemicals
  • Excessive production of regeneration wastewater
  • Slow rinse up from regenerations
  • Low PH Deionised water
  • Slippage of weak ionic species through the ion exchange resins, (silica).

In balance, deionisation systems are subject to a lesser margin of human error than Reverse Osmosis. Even so, sufficient care should be taken to monitor the quality of the chemicals required to make the system work. Any noticeable drop in recovery rate should be taken note of and a maintenance engineer called in to check for any developing problems with the system.

In the same way that Reverse Osmosis plants are dependent on the RO membranes, Deionisers are dependent on the performance of their ion exchange resins.

During the life span of ion exchange resins, the performance of the resins will change. This is a factor of the physical condition of the resins and the level of fouling in the system.

Cation Resins

Conventional DI systems use a gel-based cation resin. These resins provide a good working life span but will degrade physically after approximately 5 to 7 years, after which time they need to be replaced. Before this it is possible for softener resins to become fouled with iron particles if the pre-treatment is inadequate, but this can be remedied with an acidic rinse.

Water Softeners contain a strong gel cation resin. These resins do not completely lose their capacity to reduce water hardness through ion exchange, but they do break down physically over time.

Anion Resins

Depending on the type of deionised water and PH required, different anion resins can be used. Anion resins are prone to fouling, and because of this a microporous resin is often used. Anion resins do break down physically but they also lose their capacity to exchange anion impurities out of the water being treated. This is a progressive effect which increases when the resins are 3 to 5 years old.

Because of the costs involved in labour and materials, it can be tempting to operate DI systems with resins that are beyond their useful working life. This, in many cases, is a false economy as the effects are a decreased volume of deionised water, coupled with an increased volume of regeneration effluent. You will also need to use more regeneration chemicals to achieve the same result, adding to your operating costs.

Fouled anion resins can be cleaned to remove what is typically organic fouling. This is achieved by mixing up a solution containing 2% caustic soda and 10% brine. Ideally the solution should be at a temperature of around 40°C. The solution is pumped into the resin and left to soak overnight. When rinsed out the next day a strong, discoloured effluent is produced.

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Chelate Resins

Specialist Chelate resins are sometimes used to remove heavy metals from your water. These are very effective in ensuring that waste stream outfalls are within consent limits. These resins need to be regenerated in a very specific way: First, the service run impurities are removed with hydrochloric acid, and then the resins are put into a sodium form through counter-flow regeneration.

The quality of ion exchange resins is critical to the whole process. Substandard resins have a shorter working life and do not perform as well. Cheap resins can be purchased from the Far East, but manufacturing standards are unpredictable at best. As resins are so fundamental to the efficient operation of a DI system, we strongly recommend that you don’t take the risk.

Does CDI Require Resins?

Yes, CDI also pushes water through cation and anion resins. However, an electrical charge is used to separate water molecules and also regenerate the cation and anion beds, without the need for chemicals. This is seen as an advantage by many users.

However, if your facility requires bacteria-free water, reverse osmosis must be used to pre-treat the feed water before it goes through the CDI system. This observation leads us on to our next section; how to prevent bacteria causing chaos in your system.

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Troubleshooting Part Two: How to Avoid Bacterial Contamination

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The presence of bacteria following microbiological testing is like a nightmare come true. Bacterial infections can quickly become entrenched in a system and are difficult to deal with conclusively. Installing a high-quality DI system is an effective way of keeping on top of the problem of bacteria long term. This section looks at how water contamination occurs and how to deal with it.

How Contamination Occurs

Contamination of feed water is a big problem for a water purification system. Once feed water is contaminated, bacteria can easily enter the system and become embedded. Six factors come into play when assessing the contamination risk:

1) Pipe Length

Bacterial growth is a constant threat, especially when water has to travel through a series of long pipes. The farther the distance water has to travel, the higher its chances of becoming contaminated by bacteria that may be living there. The best advice when considering a DI system is to choose a location that will allow water to travel as short a distance as possible before reaching its destination. It is therefore extremely important that your system is installed professionally, by a team who are fully aware of the risks and how to guard against them.

2) Pipe Material

The use of the correct materials for pipe construction is very important in deterring bacteria. ABS and PVC piping are very effective, with an excellent range of fittings available to suit every installation. It is possible to install a complete purified water system in 316L grade stainless steel, which makes it difficult for bacterial colonies to take hold

3) Pipe Installation

Materials play a role in lowering contamination risk, but all of this can be wasted if the installer is not trained in all aspects of purified water system design and construction. Within the pipe work installation, all joints should be crevice free, without dead spaces (deadlegs), and should be longer than four internal pipe diameters.

No matter what material is used, crevice free construction is imperative to prevent hide out areas where bacteria can grow.

4) Tanks

Inevitably within a purified water system there will be one or more system water tanks. These tanks should be made of the correct material of construction, which should in most cases be polypropylene or 316L stainless steel.

Tanks should be manufactured with crevice free interiors and have a sealed lid.

For integrity the tank will be vented, and this vent will also be filtered to 0.01 microns, to prevent the ingress of airborne bacteria.

If the tank is part of a recirculation system it should include a 360/180 degree upwards spray ball, through which the returned water will pass.

Tank level controls should be of the ’non-intrusive’ type. Hydrostatic level controls with a diaphragm seal are the best for crevice-free, reliable operation.


5) Temperature

Bacteria strains such as pseudomonas will multiply at temperatures as low as 20°C. It is therefore sensible to keep the temperature of permeate and feed water to a maximum of 18°C.

Remember that devices such as pumps and UV sterilisers will pass heat energy into the purified water, increasing the contamination risk. A stainless steel plate heat exchanger and air cooled chiller are an effective method of removing excess heat.

6) Flow Rates

Bacteria can start to take hold if the flow of water around a system is too slow. We recommend you aim to achieve a velocity of 1.5 to 2 meters per second. You therefore need a well-ordered pipe network and an adequate pump.


Disinfection Methods

Regardless of the system being used to remove bacteria from water, disinfection is crucial. A system that does not undergo regular disinfection will become infested by all manner of viruses, algae and bacteria. If the system is not disinfected regularly, complete flushing may become necessary, which can be expensive in terms of downtime. These are the three most common ways of achieving this:

- Pre-Treatment Through RO

You can use reverse osmosis as an effective pre-treatment method to strip bacteria out of feed water before deionisation. As the pump propels water through the system, organic compounds, bacteria, and many viruses become trapped on the surface of the membrane.

- Ultra Violet Sterilisation

UV sterilisers are effective devises in the prevention of bacteria growth.

The UV unit needs to be of 316L stainless steel construction with a correctly sized 254 nanometre per second UV arc lamp. Many UV arc lamps have an effective ‘killing’ career of 9,000 hours. The lamp should be replaced at this time.

There are many UV units available to suit different budgets. A unit should be selected that includes a UV intensity monitor, to enable you to monitor the UV lamp performance.

- Chemical Sterilisation

Feed water can be disinfected with chlorine, sodium hypochlorite, hydrogen peroxide or perecetic acid, which kill most bacteria. The suspended chemicals will then have to be removed with activated carbon, before the water is put through an RO membrane to remove residual particles. This is the cheapest disinfection method but is the least eco-friendly, as chlorine is an extremely hazardous chemical.

No system is completely immune to bacteria. Even with the best designed and constructed purified water system it is still advisable to disinfect every six months.

Chemical disinfection is completed by recirculating a disinfecting chemical around the pipe work and tanks.

Disinfection procedures can be complex and should not be undertaken by anyone who has not had adequate training. In addition to health and safety issues, it is also important that the disinfection has been effective in achieving the desired result.

Is Bacteria-Free Water Possible?

Bacteria-free water is achievable through conventional deionisation by adopting the precautions discussed in this section. In the case of CDI, systems are generally less susceptible to contamination but bacteria can still build up on resins between cleaning and recharging sessions. Periodic disinfection of the whole system is therefore advised, even if just as a precaution.

If your facility requires varying levels of water purity, then you will find that a deionised water system offers the versatility you need. Most DI systems can produce water that’s between 50 and 0.055 Microseimens in purity, meaning that you can have the pure water you need virtually on demand.

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How To Choose The Right Company

For a deionised water treatment system to perform as it should, correct installation and regular maintenance are essential. Therefore any business will benefit from having a partnership with an experienced supplier and service company. What should you look for in a water purification specialist? If you are investing in new equipment or setting up a water purification system for the first time, then the following can act as a checklist of desirable features.


Water purification is a technical process that requires specialist knowledge, specific equipment and a thorough knowledge of chemical and biological contaminants. It is a wide field, and therefore a water purification company needs to demonstrate knowledge in a wide variety of areas. When selecting a company, talk to their service team about the expertise of their engineers. What is their industry background? Have they got current clients in your sector? How have they successfully dealt with similar problems to your own in the past?

Experienced Engineers

Every engineer has to learn somewhere, but when it comes to designing, installing or servicing your water purification system, it is better to have the confidence that the engineers you are dealing with have solid experience and know what they’re doing. Some companies use apprentice technicians and inexperienced graduates as frontline engineers on installations and maintenance jobs. This does nothing except increase the risk of human error and installation faults. Choose a partner whose engineers have a long track record of proven industry experience and expertise, so you can be sure you are in safe hands.


No company worth its salt should leave you to fend for yourself as soon as your system is installed, but this is unfortunately common practice in the industry. When pricing up different options, pay special attention to the after sales support offered by the company. Ultra-low quotes may include only minimal support, or no after sales support at all. This means that if something goes wrong, downtime will be increased as you struggle to find a supplier to come and service the system.

For companies who do provide support and routine maintenance contracts, check where their engineers and supply depots are based. Has their team got a national reach? You will ideally need access to a 24-hour helpline and out of hours service engineers in order to have peace of mind that you will be looked after when problems arise.

Remember to ask questions, questions, questions. Find out about their expertise, the background of the company, their industry experience and their service level guarantees. Get feedback and references if possible from previous and existing customers. And don’t always chase the cheapest quote; remember that low price doesn’t always equate to value for money, especially when the consequences of a substandard system can be extremely expensive.

Industrial_Water_Quality_Standards__Are_You_Up_To_Scratch.pngWhy Choose Wychwood Water

Now that you have hopefully found out a few more things about deionised water treatment systems and the characteristics you should look for in a service provider, you may be wondering what next steps to take?

We would like you to consider using Wychwood Water for your water purification requirements. We have the expertise, the experience, the qualifications and the passion to serve your company, helping you get the most out of your DI system.

We offer a comprehensive water purification service, from offering advice as to which system works best for your business, to design, installation and after sales maintenance. We also provide the full range of chemicals, consumables and spare parts you will require to keep your DI or CDI system running at peak performance.

Don’t Take Risks With Your Water

With so much resting on high-quality water purification, you need a team of experts on your side to ensure your system is installed and maintained correctly.

At Wychwood we offer the complete package. We are an ISO 9000 accredited company with 20 years’ experience of designing, manufacturing and installing deionised water treatment systems. Our focus is to create high quality, good value systems that do exactly what they’re supposed to do, for a long time!

You can buy a cheap system, or cut some corners on the installation, but the chances are this will cost you more in the long run. We are more than just a manufacturer or service company. We have accrued decades of practical engineering experience that we pour into our product range and make available to our customers.

So have a chat with one of our technical sales team about what we can do for you. If you haven’t used a deionised water treatment system before, you may be surprised at your high yields of purified water or the way it speeds up your whole production line. Equally, if you ran into difficulties with a previous installation, we can iron out these problems and install your new system so that it needs minimal long-term maintenance.

We are proud to offer a range of additional services to make your life easier, including refurbishments, calibration and decommissioning of old systems. In our long experience, we have found that no two manufacturers are exactly alike, so our goal is to find a bespoke solution to suit you, and not expect you to accommodate an off-theshelf system.

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