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12.48 CHAPTER TWELVE

terns. However, they have a disadvantage in that they must usually treat the entire water
supply---even portions that are not necessary, such as for watering lawns and flushing toi-
lets. Centralized treatment allows for more effective monitoring of the effluent quality,
and in cases where the contaminant must be removed from the wastewater prior to dis-
charge, the centralized treatment facility provides an easier pathway to collect and treat
the regenerant waste.

Exchange Tank or Lease Services
Exchange tank services are becoming more widely available and are one of the larger fu-
ture trends in the way that ion exchange is used. Exchange tank services are available for
all flows, from point-of-use systems up to large centralized treatment facilities. There are
advantages in the capital cost saved by not installing the treatment system, and there are
advantages in the freedom of not having to regenerate and dispose of the wastewater pro-
duced by the regeneration process. The exchange tank service companies are experienced
in performing regenerations and are, in some cases, able to charge a lower unit water cost
than can be provided by a municipality or a homeowner. Most of these companies will
perform the monitoring and validation requirements of the ion exchange system. These
services are far more readily available in urban communities than in rural communities
as they are transportation-sensitive (location-sensitive).

Operation and Maintenance of Equipment

Operation. The main duty of an operator is to operate the equipment and to document
the procedures followed and the effluent parameters of the ion exchange system. In man-
ual systems the operator must also operate valves and pumps during the regeneration pro-
cedure and in some cases even make up the chemical solutions used during regeneration.
As a bare minimum, the operator should log the flow rate, throughput, effluent quality,
and time and date of each regeneration. It is also helpful to record the flow rates, con-
centration doses, and inventory levels of chemicals used during regeneration. In highly
automated systems these functions would be performed by PLC. The objective of taking
these data is to be able to determine trends in the ion exchange system performance and
to spot malfunctions or events that might cause malfunctions and to prevent them from
happening.
Most ion exchange systems require between 1 and 2 h to regenerate. Where manual
operation is employed, the operator must be present during the entire regeneration, al-
though she or he will have time between steps to perform other duties, such as filling out
the logbook. Even with automated systems, if the process is critical and the effluent is
critical, an operator should be present during the regeneration to watch over the automatic
system and to verify that it performs the way that it is supposed to. In larger systems au-
tomation has other advantages. It frees the operators from the necessity of climbing to
reach valves that may be in rather inaccessible locations. It generally ensures that regen-
erations will be carried out in a predictable fashion and performed the same way each
time in every unit within the system. A single operator may be able to control several au-
tomated processes simultaneously from a central control room, thereby reducing the over-
all workforce requirements. Most large industrial ion exchange plants are automated and
have operators whose duties include watching over the automated regeneration. The strat-
egy of having operators who are dedicated to the ion exchange plant is not always eco-
nomically feasible. The second-best choice would be to have a chemist or a lab techni-
cian on a part-time basis perform the necessary operation of the ion exchange system, as