Potable and Waste Water Systems

Potable and Waste water treatment

Neutralization of basic pH effluents by carbon dioxide injection

Does your production process or your cleaning routine consume large amounts of water? Are you committed to implementing the relevant environmental laws (discharge consent) and observe a responsible attitude towards your environment? Praxair can help you focus on your core business while controlling waste water effluents.

Neutralizing the pH of industrial waste waters through CO2 injection has several advantages over chemical methods.

  • Safety: Carbon dioxide is non-hazardous and non-corrosive.
  • Efficiency: The effect is immediate and without risk of over-acidification.
  • Simplicity: Easy to control, simply injecting liquid carbon dioxide in the waste water effluent stream in order to re-balance its pH.

Alkaline or acid detergents are often used to clean production equipment and installations. In some sectors, such as the manufacture of paper and cardboard, the industrial processes themselves generate the basic aqueous effluents. The pH is one of the most important measures of water quality and a component of the Mogden formula for trade effluents in the UK.  

Main sectors concerned:

  • Food and beverage (beer/cider, soft drinks, slaughterhouses, meat packing, dairies ...)
  • Pulp and paper
  • Thermal power stations
  • Oil and Refining
  • Chemical, petrochemical and pharmaceutical
  • Metallurgical Industry
  • Surface treatments
  • Automotive and Mechanical
  • Mining Industries
  • Steel Industry
  • Textile industry

Re-mineralization of potable water with CO2

Praxair has advised water companies across UK and Ireland in their approaches towards the re-mineralization of drinking water (re-mineralization of potable water). Re-mineralization is required in very soft waters for which the calcium-carbon balance could lead to too high a final pH.  CO2 re-mineralization has the distinct advantage of setting the water calcium-carbon balance by controlling the choice of the final pH. The reagents used are CO2 and lime, or CO2 and a limestone filter.

When processed, the water is decanted and filtered and then usually disinfected (sometimes using ozone) and filtered again through a coal or carbon filter. At this stage, the water is clear and clean  but it is not yet ready to be used as drinking water. Before that,  the water must be mineralized. Why? Because a water lacking minerals has some adverse effects:

  • Strong corrosion potential 
  • Risk of dietary deficiency leading to ischaemic heart diseases and cerebrovascular diseases (WHO, 2005; WHO, 2006)

Re-mineralization by CO2 injection must be done in accordance with the relevant national and local standards and laws, including BS EN 936 "Chemicals used for treatment of water intended for human consumption - Carbon dioxide" relating to methods of treatment of water intended for human consumption. This standard describes the characteristics of carbon dioxide and specifies the requirements and corresponding analytical methods for carbon dioxide. It also gives information on its use in water treatment. 

Praxair offers:

  • Technical audits of waste water treatment facilities
  • Injection system design and installation
  • Remote control of dosing and storage levels through telemetry
  • Delivery reliability
  • CO2 storage solutions
  • Technical and safety training for your staff
  • Technical support for injection systems and software