Water Well Journal
Issue link: https://read.dmtmag.com/i/692787
by the overwhelming presence of sodium ions from the resin bed and removed from the softener unit. This "cycle timing"—which includes the time required for the necessary initial period of backwashing, followed by the regeneration process, and finally the final rinse and resettling of the bed before returning the unit to service—is initiated and performed automatically by the control head and valve and is started based on either the total water volume passed through the unit (demand-based regeneration) or from a preset auto- matic timer (automatic regeneration). Another important design factor that must always be con- sidered is the possible presence of other potential contami- nants in the raw water supply. For example, water-softening applications that include iron or manganese in the incoming water supply can result in "fouling" or an eventual plugging of the resin bed over an extended period of operational time. It is critical the designer fully evaluate any applications that may include iron, iron bacteria, manganese, or hydrogen sulfide in the raw water supply. It is also crucial to use a resin designed and approved for the removal or tolerance of these contaminants, and only allow the use of what is called "iron- resistant" or "iron-out" water softener salt in the unit—salt especially formulated for this type of application. In many cases, pre-treatment of the raw water to remove iron, manganese, and hydrogen sulfide is indicated to lower the demand on the water softener, improve service, and extend the operational life. Although salt (sodium chloride) has his- torically been used for creating brine solutions, increasing concerns due to the potential health impacts caused by higher sodium ingestion, as well as increased salt levels in sewage treatment and wastewater collection systems, have seen a recent increase in the use of alternatives such as potassium chloride (KCl) for creating brine solutions. Although more expensive to use, potassium chloride negates the health con- cerns related to the ingestion of sodium and potential prob- lems to the wastewater system and replaces it with the far more beneficial health impacts gained from the use of potassium. As a reminder—depending on the size, application, and treatment intent—water softeners (either ion or anion ex- change units) are capable of discharging large volumes of backwash and "rejected ion" water with high levels of re- moved, sometimes hazardous, contaminants that must be accepted by a local sewer system, septic tank/drain field, or other type of wastewater receiving facility. To guard against any long-term problems, the designer must remember to fully evaluate and confirm the discharged wastewater will not adversely impact the septage receiving facility nor interfere with the ongoing wastewater treatment process. WWJ July 2016 47 Twitter @WaterWellJournl ENGINEERING continues on page 48 Ion exchange is most efficient when the media is contained and used inside of cylindrical beds and the incoming water is directed to flow downward.