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Water Treatment for the Recycling of Process Rinse
Water
Tony Mitchelmore
Wychwood Water Systems Ltd.
Why Recycle Water?• Reduce Operating Costs
Cost to buy and discharge 1m3 water ≏ £1.50 - £2.00
• Quality ImprovementFinal rinsing of the product with deionised water can reduce staining, surface blemishes, lower reject rates by improving coating adhesion and reduce failures due to conductive contamination.
• Environmental Responsibility/IPPC/ISO14001Reducing our industrial water consumption conserves supplies, and minimises damage to water courses and aquatic wildlife by reducing demand for excessive water abstraction. CO2 emissions are also reduced as utility companies need less electrical energy for pumping.
Traditional Process
Final Rinse 1st Rinse Surface Treatment
Mains or Deionised Water
Flow of Work
Methods of Water Recycling
• Recycling Deionisation System
- incorporating system tank feeding plant comprising an activated carbon filter, to prevent fouling of resins and a twin-bed filter deioniser .
• Reverse Osmosis
- possible, but not practical due to high reject rate from plant and pre-treatment needed by RO.
Water-Suitability for Recycling
• Only low level of suspended solids, preferably none. No appreciable turbidity, otherwise particulate (sand) filter required.
• No oil or other hydrocarbons.
• Added conductivity up to 200µS/cm
Rinse Water Recycling System
Mains Water
Final Rinse 1st Rinse Surface Treatment
Effluent Treatment
• Recycling plant concentrates ionic contaminants.
• Produces small volume (1-2m3, depending on plant size) of effluent at each regeneration.
• Heavy metals can be:-
Plated out
Precipitated
Concentrated by RO
Evaporated
Regeneration FrequencyRinse Water Conductivity v Capacity
- 2.5m3/hour Plant
0.0100.0200.0300.0400.0500.0600.0
10 20 30 40 50 60 70 80 90 100
Added Conductivity uS/cm
m3/regeneration
Operating Hours
Economics of Recycling
Water consumption – 30m3/day @ £1.50/m3 = £11,250/year.
Plant cost - £10,000+ depending on size.
Payback = 1 year
