Water treatment tank with conductivity monitor
A water treatment system has a water treatment tank that stores a resin bed, a conductivity monitor, a valve assembly, a flow meter, and a controller. The control valve assembly is switchable to selectively permit untreated water flow into the tank, treated water flow out of the tank, and regenerant flow into and out of the tank. In one configuration, the conductivity monitor includes at least an uppermost probe located within 6″ of the nominal mid-point of the resin bed and a second probe located half-way between the first probe and the bottom of the resin bed. Signals from these probes are used in combination with flow data as measured by the flow meter to provide precise information regarding volumetric capacity as depletion is registered at each probe. Also disclosed are an improved technique for sampling data from the conductivity monitor, and a wireless conductivity monitor.
1. A water treatment system:
a water treatment tank that is configured to be placed in communication with a water source and to store ion exchange media forming a resin bed, the water treatment tank including a peripheral wall, a bottom end, and a top end;
a conductivity monitor comprising first and second vertically-spaced probes located in a portion of the water treatment tank that is configured to contain the resin bed;
a flow meter that is configured to measure volumetric water flow through the water treatment tank;
a control valve assembly that is configured to control fluid flow into and out of the water treatment tank;
a controller in operative communication with the conductivity monitor, the flow meter, and the control valve assembly, the controller being configured, during a service phase of a water treatment cycle that follows a regeneration phase of the water treatment cycle, and using signals from the flow meter and the conductivity monitor, to
detect depletion of the ion exchange media at the first probe and, upon such detection at the first probe, determine an actual volume of water (AV P1 ) that has flowed through the water treatment tank thus far during the service phase of the water treatment cycle, and estimate an actual total volumetric capacity ATVC of the ion exchange media in the resin bed,
detect depletion of the ion exchange media at the second probe and, upon such detection at the second probe, determine an actual volume of water (AV P1-P2 ) flowing through the water treatment tank between depletion detection at the first and second probes, and
calculate an updated actual total volumetric capacity UATVC based on the determined values of (AV P1-P2 ) and AV P1 .
2. The water treatment system of claim 1 , wherein the first probe is located proximate a nominal midpoint of the resin bed and the second probe is located half-way between the first probe and a nominal bottom of the resin bed, and wherein the controller is configured, during the service phase of a water treatment cycle to
estimate a total volumetric capacity ETVC of the ion exchange media in the water treatment tank at the beginning of the service phase of the water treatment cycle.
3. The water treatment system of claim 2 , wherein the controller is configured to determine UATVC using the equation: UATVC=2(AV P1-P2 )+AV P1 .
4. The water treatment system of claim 2 , wherein the controller is further configured, upon detection of depletion of the ion exchange media at the first probe, to determine that one half of the estimated total volumetric capacity of the ion exchange media remains, leaving an estimated remaining capacity ERVCP1=½ ETVC.
5. The water treatment system of claim 3 , wherein the conductivity monitor further comprises a third probe that is positioned beneath the second probe near a bottom surface of the resin bed, and wherein the controller is configured to detect depletion of the ion exchange media at the third probe and, upon such detection at the third probe, determine actual or imminent exhaustion of the of the resin bed.
6. The water treatment system of claim 1 , wherein the controller is configured to detect depletion at each probe by comparing conductivity-based measurement between that probe and another probe.
7. The water treatment system of claim 1 , wherein the controller is further configured to normalize data from the second probe to data from the first probe prior to determining the actual total volumetric capacity ATVC in the water treatment tank.
8. The water treatment system of claim 1 , wherein the controller is configured to normalize data by,
obtaining raw data readings from each of the first and second probes at the same time,
determining a scaling factor required to make the data reading from the second probe equal the data reading from the first probe, and
for subsequent data readings, multiplying the data reading from the second probe by the scaling factor.
9. A water treatment system:
a water treatment tank that is configured to be placed in communication with a water source and to store ion exchange media forming a resin bed, the water treatment tank including a peripheral wall, a bottom end, and a top end;
a conductivity monitor comprising first and second vertically-spaced probes located in a portion of the water treatment tank that is configured to contain the resin bed;
a flow meter that is configured to measure volumetric water flow through the water treatment tank;
a control valve assembly that is configured to control fluid flow into and out of the water treatment tank;
a controller in operative communication with the conductivity monitor, the flow meter, and the control valve assembly, the controller being configured, using signals from the flow meter and the conductivity monitor, to determine an actual total volumetric capacity of the water treatment tank, wherein the controller is further configured to
transmit excitation signals through the first and second probes to produce output signals at each probe that are dependent upon the prevailing conducity of the ion exchange media at the respective probe, each of the output signals being of finite duration, having a beginning and an end, and
periodically sample the output signals from each of the probes, wherein at least some of the samples are obtained with a delay of no more than 10 milliseconds from the beginning of the corresponding output signal.
10. The water treatment system of claim 9 , wherein the delay is no more than 5 milliseconds.
11. The water treatment system of claim 1 , wherein the water treatment tank further comprises
a riser tube that is configured to extend vertically through the resin bed, and wherein
the first and second probes are supported on the riser tube.
12. The water treatment system of claim 11 , further comprising wires that extend from the probes through a sealed opening formed in an upper dome of the water treatment tank.
13. The water treatment system of claim 1 , wherein the controller is further configured to, after determining the updated actual total volumetric capacity UATVC of the ion exchange media, determine a remaining volumetric capacity of the ion exchange media.
14. The water treatment system of claim 13 , wherein the controller is further configured to, after determining a remaining volumetric capacity of the resaid bed, implementing control of one or more aspects of a regeneration cycle of the system.
15. The water treatment system of claim 9 , wherein, when graphed in voltage amplitude versus time, a curve of each output signal is generally saw-toothed in shape, having a leading edge, a trailing edge, and a peak located between the leading edge and the trailing edge, and wherein the sample is obtained at a time corresponding to a location between the leading edge of the curve and the peak of the curve.
16. A water treatment system:
a water treatment tank that is configured to be placed in communication with a water source and to store ion exchange media forming a resin bed, the water treatment tank including a peripheral wall, a bottom end, and a top end;
a conductivity monitor comprising first and second vertically-spaced probes located in a portion of the water treatment tank that is configured to contain the resin bed;
a flow meter that is configured to measure volumetric water flow through the water treatment tank;
a control valve assembly that is configured to control fluid flow into and out of the water treatment tank;
a controller in operative communication with the conductivity monitor, the flow meter, and the control valve assembly, the controller being configured, using signals from the flow meter and the conductivity monitor, to determine a volumetric capacity of the water treatment tank, wherein the controller is further is configured to
periodically transmit excitation signals through the first and second probes to produce output signals at each probe that are dependent upon the prevailing conductivity of the ion exchange media at the respective probe, each of the output signals having a temporal period, and
sample the output signals from each of the probes, wherein at least some of the samples are obtained with a delay of no more than 20% into the period of the corresponding output signal.
17. The control system of claim 16 , wherein the delay is no more than 10% into the period of the corresponding output signal.