The illustration depicts a negatively-charged zeolite to which [positive] sodium ions are attached. Calcium or magnesium ions in the water displace sodium ions, which are released into the water. In a similar way, positively-charged zeolites bind negatively-charged chloride ions (Cl–), which get displaced by bicarbonate ions in the water. As the zeolites become converted to their Ca2+ and HCO3– forms they gradually lose their effectiveness and must be regenerated. This is accomplished by passing a concentrated brine solution though them, causing the above reaction to be reversed. Herein lies one of the drawbacks of this process: most of the salt employed in the regeneration process gets flushed out of the system and and is usually released into the soil or drainage system— something that can have damaging consequences to the environment, especially in arid regions. For this reason, many jurisdications prohibit such release, and require users to dispose of the spent brine at an approved site or to use a commercial service company.