Comparison of treatment capabilities and verification of treatment solutions
Type of Treatment | Description | Contaminants treated | Uses | Advantages | Disadvantages |
---|---|---|---|---|---|
Particulate Filters. | Filters of pleated papers, woven cartridges or ceramic candles. | Particulate matter (colour, turbidity) | To reduce discolouration and prepare water for further treatment | Simple, easy to use, no chemicals involved | Prone to blockage, can contaminate water with bacteria as bacteria can grow within the filters. |
Activated carbon. | Utilisation of activated carbon to adsorb chemicals. | Colour, taste, odour, pesticides THMs. Will act as a physical filter to remove particles | Effective against target contaminants | Small, easy to use, no chemicals involved | Taste and odour from bacteria growth on the filter if not changed frequently enough. |
Reverse osmosis units. | Physical filter | Usually used for chemicals which are difficult to remove with other treatments systems. Can be different pore size. | Usually used at point of use and blended with non-filtered water | Effective | Lots of waste water produced. Reduces minerals in the water to unacceptable levels. Can reduce pH to a level which corrodes pipework. |
Ion exchange units. | Swaps target contaminants on a media for anions or cations. Typically used in domestic water softeners. | Normally hardness and nitrate but different resins can be supplied for specific contaminants. | Typically used for hardness or nitrate removal | Excellent system for removal of nitrates. | Requires periodic backwash to regenerate resin. Requires replenishment of the salts periodically |
Chlorine disinfection | Killing of micro-organisms through timed exposure to a chlorine dose | Bacteria and other microorganisms | Good for large supplies or supplies with a long network where the presence of a disinfectant residual is beneficial | Well-understood technology | Requires storage and use of chemicals, pH might need to be adjusted, requires contact time with the chlorine. May require a pre filtration stage. |
Ultraviolet disinfection (UV). | The passing of the UV light through the water to kill micro-organisms. | Bacteria and other microorganisms | Widely used. Can be particularly effective at inactivating Cryptosporidium. | Effective for the killing of micro-organisms. | Requires regular cleaning and bulb replacement, and an electricity supply. May require a pre filtration stage as ineffective if water is turbid or highly coloured. |
Iron and/or manganese removal | Oxidation of iron/manganese in water followed by filtration to remove it | Iron and/or manganese | Removal of iron/manganese | Often supplied as a single proprietary unit. Uses air for oxidation | Requires periodic backwash (although this may be automated) |