Sidestream Filtration

BSRIA BG29/2012 & BSRIA BG 50 now recommend the use of  side stream filtration to maintain water quality and keep systems clean for the life if the system.

The water in closed systems usually contains a suspension of fine, abrasive particles which is harmful to the equipment and leads to unscheduled shutdowns and increased maintenance. There are various sources of these particles, mostly resulting from corrosion—oxygen dissolved in the fluid being an important contributor. They are rarely oxygen-free during operation, due to constant air leakage through pressure equalization valves, pipe joints, pump packing, etc. In addition, a quantity of oxygen, although small, is continually added to the system through makeup water. Since most systems are largely constructed of steel, this leads to the generation and circulation of suspended iron oxide particles throughout the equipment. Other sources of particulate matter are millscale and debris left over from assembly, as well as material introduced when the system is opened up for routine maintenance. With any biocide treatment works it can be common to see the release of debris which has been held out by biofilms leading to an increase in suspended solids.

Suspended iron oxide particles and other debris including micro biological proliferation, are very abrasive to mechanical pump seals and can coat or plug up heating coils, causing them to lose their heat-transfer ability. Additionally, areas of the piping and equipment that become covered with debris are subject to under-deposit corrosion and can provide suitable conditions for planktonic conditions to arise which can contribute to MIC (Microbiologic induced corrosion)

Implementing a properly designed water treatment program following a pre commission clean is the first step towards maintaining acceptable water conditions and minimising maintenance and repair costs.

A Side Stream filtration system is designed to treat 5 – 15% of the main water circuit flow, to remove both suspended solids and the chemically treated biomass. Our filter media are available in a range of absolute micron ratings so the removal efficiency can be adjusted to achieve a progressive clean up of the re- circulating water. Typically a 20 µm rate filter is used for the initial clean up. Once this is achieved a finer filter can be used e.g.10 µm absolute. We recommend the use of absolute rated filters as unlike nominal filters they maintain their removal efficiency for contaminants throughout the lifetime of the filter, even under varying water quality conditions. It is typical for nominal filters to suffer reduced removal efficiency or to unload previously retained contaminants after a period of use and this will cause unexpected system fouling.

Installation recommendations are available from us and we have included a pre-installation survey.

Benefits of installing a ph Water Technologies Side Stream Filtration System

  • Protection of automated valving from fouling to ensure effective building temperature control is maintained
  • Removal of suspended solids to reduce abrasive wear and tear on process plant.
  • Removal of chemically treated biomass to further reduce pipework degradation.
  • Reduced time and lower labour costs when compared to a conventional flushing regime.
  • Reduced maintenance, equipment down time and repair costs.


Water Softeners

Limescale causes a significant increase in energy input to the boiler to meet the same heat demand it will also insulate the water from the heat source and impair performance and heat transfer. Build up of scale along with fluctuating temperatures encourages the growth of bacteria including Legionella and this could pose a serious risk to users of the system.

Softened water will eliminate the build-up of limescale in pipes, on heating elements and at the outlets reducing maintenance/repair costs and improves efficiency.

The Health and Safety Executive’s Approved Code of Practice (ACoP) and Guidance document titled “Legionnaires’ disease: The control of legionella bacteria in water systems” (L8) gives practical advice on how to comply with UK health and safety law with respect to the control of Legionella bacteria.

HSG274 Part 2: The control of legionella bacteria in hot and cold water systems

2.8 The cleanliness of the system must be maintained, as legionella bacteria are more likely to grow in a system fouled with deposits. In hard water areas, softening of the cold water supply to the hot water distribution system should be considered to reduce the risk of scale being deposited at the base of the calorifier and heating coils, and to reduce the potential for scale build-up within the system pipework and components.

2.72 Light scale formation on the inner surfaces of pipes can be protective against the leaching of metals such as lead or copper, but heavier deposits are likely in hard water areas. These deposits increase the surface area and therefore the potential for microbial colonisation (biofilm formation) and can provide protection from the effects of biocides. In hard water areas, softening of the cold water supply to the hot water distribution system should be considered. This is to reduce the risk of scale being deposited at the base of the calorifier and heating coils, especially at temperatures greater than 60 °C, and the potential for scale build-up within the system pipework and components (eg TMVs) which may significantly reduce flow and adversely affect the efficiency of the system.

PH- Water Softeners are brilliantly designed with unrivalled reliability. They are easy to use and produce luxuriously soft, limescale-free water. The costs of water softeners are usually far outweighed by the benefits and cost savings obtained, through using softened water.

Ultra Violet Disinfection (UV)

As an alternative or supplement to traditional chemical disinfectants, an ultraviolet disinfection system offers a number of operating advantages. UV disinfection systems are safe and easy to operate. In addition, the use of UV does not inject any taste or odour into the processed water, nor does it produce any undesirable by-products.

There are no micro-organisms known to be resistant to UV light. UV is known to be highly effective against bacteria, viruses, algae, moulds and yeasts. In practice, bacteria and viruses are the cause of most major waterborne pathogenic diseases. Of these enteric viruses, hepatitis virus and Legionella pneumophila are readily eliminated by UV treatment. For most microorganisms, the removal efficiency of UV for microbiological contaminants such as bacteria and virus generally exceeds 99.99%.

It is recommended that UV systems should be installed with pre-filtration to maintain effectiveness as sediment and other contaminants in the water can create a “shadow” which prevents the UV rays from reaching and disinfecting the harmful microorganisms.

Once installed units must be regularly serviced and the lamps and Quartz sleeve replaced periodically. Typically a life expectancy of a lamp is usually 8000 operating hours. After that period the ability of the lamp to emit UV radiation will decrease significantly.

Quartz sleeves, just like UV lamps, wear out over time. Quartz will lose its ability to transmit UV rays into the reactor chamber. To maximize the optimal performance of any UV unit, manufacturers recommend that the quartz sleeves be replaced with each lamp replacement.

Chlorine Dioxide

Chlorine dioxide is an oxidising biocide/disinfectant that when used correctly, has been shown to be effective at controlling both legionella and biofilm growth in hot and cold water systems. In the appropriate application, it may be used to aid legionella control where maintaining a conventional temperature regime is difficult or where the removal of all dead legs and little used outlets is impractical. Chlorine dioxide is usually produced on site from a chlorite-based precursor using a chlorine dioxide generator or dosing system by reaction with one or more other chemical precursors or by a catalytic oxidation process.

It has a bacterial efficiency comparable with that of free chlorine in the neutral pH range, however unlike chlorine, its efficiency increases as the pH rises. Another important fact is that it is extremely soluble in water, being up to five times more soluble than chlorine.

Used commercially in aqueous solution rather than gas due to its explosiveness when exposed to rising temperatures, exposure to light or allowed to come into contact with organic substances. In aqueous solution it is completely harmless and will not react chemically with water, as would chlorine. It can be used up to a maximum dose level of 0.5ppm for drinking water disinfection, and has a particular advantage where phenols are likely to cause taste problems or in waters which have high pH or ammonia levels.

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