| Reduced Throughput |
| Possible Cause |
Solution |
| Increased ionic loading |
| |
· Check influent water analysis
· Increase regenerant
· Add capacity
|
| Channeling, poor distribution |
|
· Suspended solids loading
|
· Check backwash; extend if needed
|
|
· Broken or clogged distributors
|
· Repair
|
|
· Low flow
|
· Maintain minimum flow
|
| Premature break |
| |
· Check previous run throughput
· If normal regenerant does not restore capacity, double regenerate
· Adjust end point
|
| Regenerant concentration and quantity |
| |
· Check metering pumps, eductors, piping, etc.
· Regenerant dosage
· Check dilution flows, time settings
· Apply correct amount at correct concentrations
|
| Resin loss |
|
· Excessive backwash
|
· Check temperature and flowrate
|
|
· Underdrain failure
|
· Check and repair (resin trap?)
|
|
· De-crosslinked resin
|
· See "oxidation"
|
|
· Flotation by dissolved gas
|
· Effluent flow control
|
|
· Normal bead attrition
|
· Topoff
|
| Resin Age |
| |
· Up to 5%/yr loss in capacity considered normal
· Analyze resin to determine remaining useful life
|
| Resin oxidation |
|
· Presence of oxidents (chlorine) and oxygen in presence of iron (catalyst) causes de-crosslinking which reduces wet volume capacity (eventually high ΔP)
|
· Chemical pretreatment of feedwater/ activated carbon filter
· Replace resin when moisture content exceeds 65%
|
| Resin fouling |
|
· Calcium sulfate, iron, manganese, aluminum fouling and precipitates
|
· Check water supply
· Check backwash
· Check regenerant chemicals for contaminants
· Clean resin by air-scour and backwash and chemically if required
|
|
· Microbiological fouling
|
· Clean resin with appropriate cleaner (compatible with resin)
|
| Excessive rinsing |
| |
· Check end-of-rinse set points
· Readjust rinse time to suit
· Check for fouling (see above)
|
| Note: All of the items listed above for "Reduced Throughput" should also be checked regarding poor effluent quality |
| Poor Effluent Quality |
| Calcium sulfate precipitation |
|
· Calcium in treated water should be zero
|
· Check resin
· If severely fouled, replace resin
· If moderately fouled, clean resin with an HCI soak (caution - check materials of construction for compatibility with HCI)
· Check influent water calcium concentration (% of total cations)
· Check and adjust acid concentration (stepwise regeneration) and flowrate
|
| Presence of calcium phosphate or other complexes in feedwater |
| |
· Check pretreatment
|
Notes: For weak acid cation exchangers regenerated with H2SO4, acid strength should not exceed 0.8% with a flowrate of 2 gpm/ft3.
Once sulfuric acid injection is started, never stop flow. If acid injection must be interrupted, stop concentrated acid flow but let dilution flow run until all acid is displaced. |
| Excess sodium in treated water ran past breakpoint |
| |
· Check and adjust set points
· Check regenerant dosage and quality
· Investigate conversion to upflow or hydrochloric acid regeneration
|
| Leaky valve |
| |
· Check bed sample vs discharge pipe sample (before and after valving); special caution on backwash inlet valve
· Check limit stops on valve operators
· Check air pressure on pneumatic valves
· Check sealing gaskets on multiports
· Check for physical damage due to water hammer
|
| Flow rates too high |
|
· Insufficient reaction time (kinetics)
|
· Reduce flow
|
| Flow rates too low |
|
· Poor distribution channeling
|
· Place one or more units in standby to increase flowrate
· Recycle treated water to inlet
|
| Resin fouling |
| |
· See "Resin fouling" above under "Reduced Throughput"
|
For counter-current regeneration, a loss of inert (inactive) resin allows resin migration which, in turn, causes high leakage
In countercurrent regeneration, it is important to use decationized or demineralized water for regenerant dilution and displacement rinse |
| |
· Check resin level at exhaustion and add resin as needed
|
| High Pressure Drop |
| Bed compaction |
| |
· Check flow and temperature for sufficient backwash
· Air or mechanical scour prior to backwash
|
| Resin fines |
| |
· Remove with backwash
|
| Cation resin de-crosslink |
| |
· Analyze resin and replace if necessary
|
| Lower water temperature |
| |
· ΔP increases with higher water viscosity at lower temperature
|
| Increased flow rate |
| |
· ΔP increases with flow (do not exceed specified ΔP)
|
| Valve partially closed |
| |
· Check and adjust all valves
|
| Internal distributor blockage |
|
· With resin, iron, debris
|
· Inspect strainers and clean
· Repair / clean distributors
|
| Plugged underdrain |
|
· Resin or subfill in collectors outlet strainers
|
· Inspect internals
|
| Increased suspended solids loading in influent |
| |
· Mid-cycle backwash
· Check filtration ahead of demineralizer
|
| Resin fouling |
| |
· See "Resin fouling" above
|
| Low Pressure Drop |
| Note: Low pressure drop is not necessarily a problem in itself; however, it may be a symptom of a problem |
| Reduced flow |
| |
· ΔP decreases with flow (normal)
|
| Increased temperature |
| |
· Lower viscosity
· Check backwash rate at higher temperature
|
| Resin loss, reduced bed depth |
|
· Underdrain failure
|
· Check for loss to sewer during backwash and rinses
|
|
· Resin attrition
|
· Inspect and repair
|
|
· Resin loss
|
· See "Resin loss" above under "Reduced Throughput"
|
