Water treatment conventionally applies to the treatment of brackish water coming from the acquifers in the underground (well water) or from the surface (rivers, lakes).
Well water treatment
This water is roughly defined by:
- low to moderate salinity
- low presence of micro-organisms, bacteria, algae, fungi
- turbidity and suspended solids are normally in the lowest range but concentration could rise in particular conditions
- presence of oils and organics is normally not likely unless with possible sources of contamination
- traces of metals and micropollutants could be present in groundwater naturally or due to industrial pollution
Treatment of well water may consist of filtration by means of media filters in order to effectively remove the suspended solids. Cannon Artes’ Hydraback® automatic valveless gravity filters are employed for this purpose. Those filters enable important savings in the energy impact since filtration is done by gravity and the plant is in fact operated on a hydraulical principle without instrumentation, backwashing pumps and control panels.
The efficiency of filtration can be enhanced by use of chemical agents (In-line Clarification) or by selection of a membrane process (Microfiltration, Ultrafiltration), that could be sized also to get rid of the microorganisms and viruses.
Granular Activated Carbon (GAC) adsorbers are effective in the removal of organics and could be moreover useful to perform the removal of free chlorine in case chlorination is done as disinfection of raw water.
When the dissolved solids content is too high to enable any industrial or civil use, a desalination process could be implemented by means of the reverse osmosis technology. This is particularly true when well or river water are contaminated by a seawater inflow.
Surface water treatment
Water from rivers or lakes is the most variable source of raw water and the most easily accessible. The following characteristics may be highlighted:
- moderately low salinity
- high bacteria content
- high turbidity,suspended solids and colloidal matter content
- important variability because of weather or seasonal variations
Treatment of surface water may consist of a sequence of different stages such as Water Clarification with coagulation and flocculation in order to destabilise and precipitate colloids and solids into a gravity settler or lamella-pack clarifier, filtration on media filters in order to effectively remove the residual suspended solids. The efficiency of filtration can be enhanced by use of chemical agents (coagulation agents or filter aids) that promote the solid particles to coalesce and further grow.
Granular Activated Carbon (GAC) adsorbers are effective in the removal of organics and could be moreover useful to perform the removal of excess free chlorine in case chlorination is done to achieve the disinfection of the feed water.
Microfiltration and Ultrafiltration may be valid alternatives to the Chemical physical unit because of the high potential of retaining suspended solids, bacteria, viruses and high-molecular-weight hydrocarbons.
When the dissolved solids content is too high to enable any industrial or civil use, a desalination process could be implemented by means of the reverse osmosis technology. This is particular case of water taken from the river estuaries when it may be contaminated by seawater inflow during the dry season.