Transcript Eclox-M
Equipment to control
(Private) Water Quality
Neil Grant
Kennet Water Components
Background
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Me – MSc in instrumentation and analytical science,
3 years at WRc, 15 years at Severn Trent
(municipal), 8 years at Kennet (Private/industrial)
water
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Kennet Water - Part of the Pollet Water Group
Supplier of equipment to the Water
professionals/installers (rather than end users)
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Products for PWS treatment
Arsenic reduction, pH, Iron & Manganese, Nitrate,
Sediment, Colour, Organic Scavengers, Carbon,
Sediment, UV, Filters
Reverse osmosis
Components – vessels/valves/media
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Member of UKWTA
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Equipment to control PWQ
Questions we need to ask
What is the application
how much water
what is the source water
any special site info
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Applications
Drinking water (private supply)
Domestic municipal drinking
water improvements
Process water
Swimming Pools
Not Municipal Water Treatment
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Private Water Treatment Layout
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Chemical Parameter Limits
• Laid down by European Union
• UK: Private Water Supplies Regulations 2009,
Covers microbial and chemical parameters
Different sampling regime for small and large supplies but basically the
same chemicals are covered
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Typical treatments in PWS
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Private water supplies often treated differently to Municipal
Water supplies due to size and use and number of users.
Municipal works use coagulation, flocculation, chlorination
PWS typically use filtration, ion exchange, Ultraviolet
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Common chemical parameters
• Depends on where in the country (different rock strata)
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South West : iron, manganese, arsenic
East : nitrates, hardness
North England: iron, manganese, arsenic
Scotland: colour (tannins), pH
Wales: Manganese, pH
Pollution
Mine runoff, road runoff, oils, fertilisers, pesticides
Arsenic bearing rocks
• Recycled water
Organics, sediment
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Water sources
• Also depends on type of water source
• Borehole
Often more consistent quality
Iron, manganese, arsenic,
• Surface
Often flashy
Natural colour, sediment, nitrates
• Recycled water
Organics, sediment
• Infrastructure:
Pipes, tanks (lead,copper)
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Chemical Mitigation Methods
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Nothing works better than stopping it getting into the PWS in
the first place
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Treatment/mitigation methods
Filter housings
Manual/backwashing filter systems
Ion Exchange Medias
Reverse Osmosis
Chemical dosing
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Borehole Pumps & Pressure Tank
• Borehole pump: - Down to you !
• Pressure Tanks
reduce the on/off cycling of pumps
Steel or plastic
Single flow/flow through
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Filters & Filter housings
• How does it work
Water passes through a filter housing and is trapped by a sediment filter or other
media (carbon, nitrate reduction)
• Advantages
Simple,
Cheap
Easy to maintain
• Disadvantages
Ideal breeding ground for bacteria
Can restrict the flow
Easily blocked
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Filters & Filter housings
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Sizes
10”, 20”, 30” and 40”
Slim, Big
• Flow rates
0-20 m3/hr
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Types of sediment filters
Spun
Wound
Pleated
Bag
Antibacterial
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Filter systems
What are they used for and trade names
Iron & Manganese
Sediment
Arsenic
pH
Organics/pesticides
Birm, Aquamandix, Filox, Greensand, Pyrolox
Sand, Turbidex, Filter Ag, Glass
Bayoxide
Juraperle, Corosex, pHlocrite
Carbon (many variations)
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Filter systems
How does it work
Water passes through a filter and impurities are trapped or adsorbed. In
many instances they can be backwashed away.
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Example: Arsenic Reduction
• Legal limit for Arsenic in water is 10ug/l (10 parts per billion)
• Can Cause
Cancers, linked to cardiovascular disease
•
Media used is Bayoxide
Regulation 31 approved – used by Severn Trent, UU
Arsenic reduction system on Transition list of approved products PWS
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Arsenic is absorbed by the media and held
Eventually the media becomes saturated and needs replacing.
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Example: Arsenic Reduction
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How to size a unit
Service flow rate max: 20m/hr, Backwash rate: 25 m/hr
Working pH range 6.8 to 9.5
Raw water must contain less than:
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200ug/l PO4, 200ug/l Fe, 50ug/l Manganese, 10 mg/l suspended solids
For waters with over 50ug/l a lead lag (dual) system will be needed
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Ion-exchange systems
What are they used for and trade names
Iron & Manganese
Nitrate
Softening
Natural colour
Demineralisation
Crystal Right
A520E
Purolite C100E, Dowex
organic scavenging,
MB400, NRW3240
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Ion-exchange systems
How does it work
Water passes through the media where certain ions are exchanged in the resin for
other ions eg calcium (scale) is held and exchanged for sodium. Periodically the
resin is regenerated eg with salt (sodium chloride)
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Ion exchange systems
Advantages
Normally automatic,
Can be targeted to the chemical pollutant
Can be sized accurately
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Disadvantages
Adds chemicals to the water
Need to be specified correctly
Need maintenance
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Example: Nitrate Reduction
• Legal limit for Nitrate in water is 50mg/l (50 parts per million)
• Can Cause
Methaemoglobinaemia (blue baby syndrome)
• Media used is Nitrate reducing resin eg Purolite A520E
Regulation 31 approved – used by Anglian, Thames, …
• Nitrate is absorbed by the media and chloride is exchanged
Chloride limit is 250 so normally adding say 50 to a background level of 80 is no a
problem. It can be blended with raw water. It is regenerated with salt – sodium chloride
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UV Disinfection
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UV Disinfection
UV systems from 5 l/min to 1000 m3/hr
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Domestic (post Municipal) Treatment
Taste (chlorine)
Particles
Mineral Reduction (RO)
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Industrial Process Water
Depends On Process
Large volume sediment reduction
Pure Water (Revers Osmosis)
Chemical Dosing
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Reverse Osmosis
To remove chemicals such as Sulphate and sodium
Reverse osmosis means the permeation of liquid
through a semipermeable membrane caused by a
pressure exceeding osmotic pressure.
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Reverse Osmosis
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Dosing systems
What are they used for and trade names
Chlorine
pH
Scale Reduction
Sodium/calcium Hypochlorite
sodium bicarbonate, sodium hydroxide
Ortho/poly phosphates
Advantages
Often automatic,
Can use feedback from sensors to be
accurate
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Disadvantages
Add chemicals to the water
Need a lot of maintenance
Can block
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Swimming Pool Water Treatment
Chemical dosing (Chlorine/pH)
Often automatic,
Sediment Filtration
Requires variable speed pumps
Low pressure manual sand filters
Top up water
Depends on source water
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Conclusions
Bacterial contamination normally more of a health
issue than chemical problems (Pragmatic approach)
Different from municipal treatment because of size
Many variations which often look similar
Work well if specified and maintained properly
Shouldn’t be used as a sticking plaster (stop the
chemicals getting in in the first place before chemical
mitigation)
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