Filtration Plant FAQs

Filtration Plant - Frequently Asked Questions

How many types of water filter does Derwent Water Services manufacture?

The water filters which Derwent Water Services manufactures are basically split into two main types, each type of filtration plant contains different varieties to remove different substances:

Category One Reverse Osmosis and Cartridge Filters

For information on reverse osmosis equipment and plant, please see our main reverse osmosis web page.

For information on cartridge filters, please see our main cartridge filter page on our website.

Category Two Regeneratable Water Filters

The regeneratable water filters category is split into six different categories, each filter with its own removal properties:

• carbon filters
  
• sand-anthracite filters (also known as multi-media filters)
  
• sand filters
  
• birm filters and iron removal filters
  
• pH neutralising filters

What is a carbon filter?

A carbon filter, or activated carbon filter as it is sometimes called, is primarily used for its absorbent capacities and the removal of dissolved organics.

Tastes and Odours: an activated carbon filter will also remove chlorine and other halogens and low-molecular-weight substances (below 100mm).

Activated carbon filters are very prone to infection from bacteria and can become somewhat of a breeding ground. All activated carbon filters must be periodically sterilised to avoid bacterial growth and contamination.

An activated carbon filter is backwashed frequently with a reverse flow wash but will eventually exhaust, unless fitted after a reverse osmosis plant or after ultra-filtration. Activated carbon can be re-activated once completely exhausted but this requires a heat treatment process which cannot always be undertaken on site and, owing to its relatively low cost, is usually just replaced.

How does a carbon filter work?

A carbon filter consists 3 main components:

1) a composite pressure vessel
2) a carbon filter control valve (usually low voltage)
3) carbon media

The water filters down through the carbon filter media, up through a riser tube in the centre of the composite pressure vessel and out through the carbon filter control valve to service.

Periodically, the carbon filter will backwash, which changes the water flow through the carbon filter. The water in the backwash cycle flows in from the inlet, down the centre riser tube, up through the carbon bed and out of the control valve to drain.

The next step in a carbon filter regeneration cycle is rinse. The water in a rinse cycle of a carbon filter flows as in service, down through the composite pressure vessel and carbon filter media, up through the centre riser tube, through the carbon filter control valve and to drain. The carbon filter then returns to its normal service position.

Please note that the above relates only to the smaller simplex carbon filters which we supply. For other types of carbon filters, such as multi-media filters, duplex carbon filters, triplex carbon filters and cartridge carbon filters, please contact Derwent Water Services Limited.

Does Derwent Water Services Ltd stock spares for carbon filters?

Yes. Derwent Water Services Limited carries stock for all types of water filters, including carbon filters.

How often does a water filter / carbon filter require servicing?

We recommend that a water filter is serviced at least twice a year to keep it in good working order.

Can Derwent Water Services service water filters / carbon filters?

Yes. We offer single-day services or service contracts on all water treatment equipment. All our water treatment service engineers are fully qualified and experienced on the full spectrum of water treatment equipment available. Please see our service package facility on the home page.

Does a carbon water filter use any re-agents?

No. A carbon water filter regenerates entirely on the feed water.

How do I know what size of carbon filter or water filter I require?

The fail-safe way of sizing any type of filter is to contact our technical team at Derwent Water Services Limited who will be more than happy to advise you on sizing your carbon water filter.

Can Derwent Water Services supply carbon filters for export?

Derwent Water Services Limited supplies carbon filters to the UK and for export.

What is a sand-anthracite filter?

A sand-anthracite filter or dual media filter/multi-media filter is primarily used for the removal of turbidity and suspended solids as low as 10-20 microns. Inside a sand-anthracite filter is a layered bed of filter media. The bed is graded from bottom to top as follows:

Having the filter media graded this way enables the sand anthracite filter to run for longer times before a backwash is necessary.

How does a sand-anthracite filter work?

A sand anthracite filter or multi-media filter consists of 3 main parts:

• a composite pressure vessel
• a sand-anthracite filter control valve (usually low voltage)
• graded beds of sand and anthracite

The water filters down through the sand-anthracite filter media, up through a riser tube in the centre of the composite pressure vessel and out through the sand-anthracite filter control valve to service.

Periodically, the sand-anthracite filter will backwash, which changes the water flow through the sand-anthracite filter. The water in the backwash cycle flows in from the inlet, down the centre riser tube, up through the sand and anthracite bed, and out of the control valve to drain.

The next step in a sand-anthracite filter regeneration cycle is rinse. The water in a rinse cycle of a sand-anthracite filter flows as in service, down through the composite pressure vessel and sand-anthracite filter media and up through the centre riser tube, through the sand-anthracite filter control valve and to drain. The sand-anthracite filter then returns to its normal
service position.

Please note that the above relates only to the smaller simplex sand-anthracite filters which we supply. For other types of sand-anthracite filters, such as multi-media filters, duplex sand-anthracite filters, triplex sand-anthracite filters and cartridge sand-anthracite filters, please contact Derwent Water Services Limited.

How often does a sand-anthracite / multi-media filter require servicing?

We recommend that a water filter is serviced at least twice a year to keep it in good working order.

Can Derwent Water Services service water filters / multi-media filters?

Yes. We offer single-day services or service contracts on all water treatment equipment. All our water treatment service engineers are fully qualified and experienced on the full spectrum of water treatment equipment available. Please see our service package facility on the home page.

How do I know what size of sand-anthracite filter or water filter I require?

The fail-safe way of sizing any type of filter is to contact our technical team at Derwent Water Services Limited who will be more than happy to advise you on sizing your carbon water filter.

Can Derwent Water Services supply sand-anthracite filters for export?

Derwent Water Services Limited supplies sand-anthracite filters for the UK and export.

What is a birm filter?

The word BIRM is an acronym for Backwashable Iron Removal Media. The media birm is a manganese-coated aluminium silicate, used primarily for the removal of dissolved ferrous iron in a water supply. It is worth noting at this point that a birm filter will not work if the pH is below 7, as the iron will not drop out of solution. To change the water-soluble ferrous iron to an insoluble ferric iron, an oxidising agent or oxygen is introduced to the system which then enables the birm to remove the iron from the water.

How does a birm filter work?

A birm filter consists of four main parts:

• a composite pressure vessel
• a birm filter control valve usually low voltage
• birm filter media
• an eductor system

The water filters down through the birm filter media, up through a riser tube in the centre of the composite pressure vessel and out through the birm filter control valve to service. Oxygen is introduced to the inlet water via an ejector to raise the oxygen level to 15%. This aids the oxidisation of the iron and helps it to precipitate. This, in turn, lets the birm remove the now ferric iron from the water.

Periodically, the birm water filter will backwash, which changes the water flow through the birm water filter. The water in the backwash cycle flows in from the inlet, down the centre riser tube, up through the birm media bed and out of the control valve to drain.

The next step in a birm iron removal filter regeneration cycle is rinse. The water in a rinse cycle of a birm iron removal filter flows as in service, down through the composite pressure vessel and sand birm filter media, and up through the centre riser tube through the birm filter control valve and to drain. The birm iron removal filter then returns to its normal service position.

Please note that the above relates only to the smaller simplex birm or iron removal filters which we supply. For other types of birm or iron removal filters, such as duplex birm or iron removal filters, triplex birm or iron removal filters and cartridge filters, please contact Derwent Water Systems Limited.

How often does an iron removal filter or birm filter require servicing?

All water filters, including iron removal or birm filters, require servicing twice a year to ensure that they are kept in good working order.

Can Derwent Water Services service water filter - birm filters?

Yes. We offer single-day services or service contracts on all water treatment equipment. All our water treatment service engineers are fully qualified and experienced on the full spectrum of water treatment equipment available. Please see our service package facility on the home page.

Does a birm filter / iron removal filter require any chemicals?

A birm filter or iron removal filter does not usually require any chemicals for standard use. However, if the pH is below 7, some pH correction using chemicals may need to be considered.

How do I know what size of birm or iron removal filter I require?

The fail-safe way of sizing any type of water filter is to contact our technical team at Derwent Water Services Limited who will be more than happy to advise you on sizing your carbon water filter.

Can Derwent Water Services supply birm filters or iron removal filters worldwide?

Derwent Water Services Limited supplies birm filters and iron filters to the UK and for export.

Does Derwent Water Services Ltd stock spares for birm and water filtration systems?

Yes. Derwent Water Services Limited stocks spares for birm filters and water filration equipment for dispatch to the UK or for export.

What other types of iron removal filter can Derwent Water Services supply?

Derwent Water Services can also supply manganese green sand iron removal filters and manganese dioxide iron removal filters. For information on the above water filters, please contact the Technical Department at our offices (see home page).

What is a sand filter?

Sand filters are one of the water filtration methods primarily used for the control and removal of turbidity. Sand water filters can economically process large volumes of water to service.

Sand filters can only remove relatively large suspended solids. Therefore, secondary water filters of a finer media grade are sometimes installed as necessary.

How does a sand water filter work?

A sand water filter or consists of 3 main parts:

a composite pressure vessel
a sand water filter control valve (usually low voltage)
graded beds of sand

The water filters down through the sand water filter media, up through a riser tube in the centre of the composite pressure vessel and out through the sand filter control valve to service.

Periodically, the sand filter will backwash, which changes the water flow through the sand filter. The water in the backwash cycle flows in from the inlet down the centre riser tube, up through the sand bed and out of the sand water filter control valve to drain.

The next step in a sand filter regeneration cycle is rinse. The water in a rinse cycle of a sand filter flows as in service, down through the composite pressure vessel and sand filter media, up through the centre riser tube through the sand filter control valve and to drain. The sand filter then returns to its normal service position.

Please note that the above relates only to the smaller simplex sand water filters which we supply. For other types of sand filters, such as multi-media filters, duplex sand water filters, triplex sand water filters and cartridge sand filters, please contact Derwent Water Systems Limited.

Does Derwent Water Services Ltd stock spares for sand filters and water filtration systems?

Yes. Derwent Water Services Limited stocks spares for sand filters and water filtration equipment for despatch within the UK or for export.

How often does a sand filter requires servicing?

We recommend that a sand filter in the UK requires servicing every six months.

Can Derwent Water Services service my existing sand filter?

Yes. We offer single-day services or service contracts on all water treatment equipment. All our water treatment service engineers are fully qualified and experienced on the full spectrum of water treatment equipment available. Please see our service package facility on the home page.

Does a sand filter use any regenerants or chemicals?

No. A sand filter regenerates entirely on the incoming feed water.

How do I know what size of sand filter or water filter I require?

The fail-safe way of sizing any type of water filter is to contact our technical team at Derwent Water Services Limited who will be more than happy to advise you on sizing your carbon water filter. Please see our home page.

Can Derwent Water Services supply sand filters or water filters for export?

Derwent Water Services Limited supplies sand filters and water filters to the UK and for export.

What is a pH neutralising filter?

Many borehole water or spring supplies have a pH of less than 7. If your water supply has a pH of less than 7, it is considered to be acidic and must be treated. Acidic water can cause various problems, such as staining and corrosion. The water filter media used in a pH neutralising filter is crushed and processed limestone, called Magnadol. Magnadol can usually raise a pH from 6 to 7.

The Magnadol dissolves into water as it passes through the filter and the natural alkalinity of the Magnadol (pH neutralising water filter media) raises the pH. Because of the calcium level in the Magnadol, the hardness of the water is affected. The hardness would be expected to rise around 50ppm.

How does a neutralising filter work?

A water neutralising filter consists 3 main components:

• a composite pressure vessel
• a neutralising filter control valve (usually low voltage)
• neutralising media (Magnadol).

The water filters down through the Magnadol filter media, up through a riser tube in the centre of the composite pressure vessel and out through the neutralising water filter control valve to service.

Periodically, the pH neutralising filter will backwash, which changes the water flow through the water filter. The water in the backwash cycle flows in from the inlet down the centre riser tube, up through the Magnadol bed and out of the control valve to drain.

The next step in a pH neutralising filter regeneration cycle is rinse. The water in a rinse cycle of a pH neutralising filter flows as in service, down through the composite pressure vessel and Magnadol filter media and up through the centre riser tube through the neutralising filter control valve and to drain. The pH neutralising filter then returns to its normal service position.

Please note that the above relates only to the smaller simplex water filters which we supply. For other types of neutralising filters, such as large simplex water filters, duplex water filters, triplex water filters and cartridge neutralisers, please contact Derwent Water Services Limited.

Does Derwent Water Services Ltd stock spares for pH neutralising water filters?

Yes. Derwent Water Services Limited stocks spares for pH neutralisers and water filtration equipment for despatch within the UK or for export.

How often does a pH neutraliser require servicing?

We recommend that all water filters need servicing every six months, including water neutraliser and pH correction filters.

Can Derwent Water Services Ltd service my existing neutralising filter?

Yes. We offer single-day services or service contracts on all water treatment equipment. All our water treatment service engineers are fully qualified and experienced on the full spectrum of water treatment equipment available. Please see our service package facility on the home page.

Does a neutralising filter require any chemicals?

No. A neutralising filter does not require any chemical for standard use.

How do I know what size of neutralising filter I require?

The fail-safe way of sizing any type of water filter is to contact our technical team at Derwent Water Services Limited who will be more than happy to advise you on sizing your pH neutralising water filter.

Can Derwent Water Services supply pH neutralising filters for export?

Derwent Water Services Limited can supply pH neutralising equipment and water filters to the UK and for export.