Common Problems and Troubleshooting for Membrane Separation

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1. Flux Decline & Reduced Permeate Production
Causes
Membrane fouling (suspended solids, colloids, organic matter, microbes)
Severe concentration polarization
Membrane scaling (Ca, Mg, Si, fluoride salts)
Abnormal operating pressure
Poor backwashing/rinsing effect
Solutions
Strengthen pretreatment: coagulation and flocculation, cartridge filtration, sedimentation tank
Increase backwashing frequency/intensity, add air-water backwashing
Perform CIP (Cleaning-in-Place):
Organic fouling → alkaline cleaning (NaOH + NaClO)
Inorganic scaling → acid cleaning (citric acid, HCl)
Reduce influent turbidity, SDI, COD
Properly lower recovery rate to reduce concentration polarization
2. Rapid Increase in Trans-Membrane Pressure (TMP)
Causes
Fast membrane fouling/clogging
Excessive influent loading
Incomplete cleaning
Solutions
Immediately reduce influent flow rate
Enhance backwashing, draining, and venting
Conduct enhanced CIP
Check for sudden water quality deterioration (high turbidity, oil, SS)
3. Deteriorated Effluent Quality (Increased Salt Passage, Reduced Removal Efficiency)
Causes
Broken or damaged membrane fibers
Leakage at O‑rings/seals
Membrane aging or oxidation
Reduced filtration precision
Solutions
Shut down system for pressure holding and leak detection
Replace damaged membrane modules
Inspect seals, end caps, and connections for leaks
Control residual chlorine and oxidants to prevent membrane oxidation
4. Membrane Scaling
(especially in fluorochemical, high‑salinity, high‑hardness water)
Causes
Crystallization of Ca²⁺, Mg²⁺, SiO₂, fluorides
Excessively high pH
Overly high recovery rate
Solutions
Add antiscalant
Remove scale by acid cleaning
Reduce system recovery rate
Softening pretreatment (lime softening, ion exchange)
5. Microbial Fouling & Biofilm Formation
Causes
High water temperature, abundant nutrients
Insufficient or delayed disinfection
Solutions
Add biocide to influent (isothiazolinone, NaClO with residual control)
Clean with alkaline + sodium hypochlorite
Avoid long‑term shutdown with stagnant liquid
6. Poor Backwashing Effect
Causes
Insufficient backwash pressure/flow
Poor quality of backwash water
Severe internal membrane clogging
Solutions
Increase backwash flow/pressure
Use permeate or clean water for backwashing
Perform chemical cleaning before resuming backwashing
7. High Operating Current / Energy Consumption
(for frequency‑modulation membranes and pumps)
Causes
High membrane resistance
Flow channel blockage
Improper VFD parameters
Solutions
Clean membrane to restore flux
Inspect flow channels and water distributors
Optimize matching of VFD, flow, and pressure
8. Abnormal Noise, Vibration, or Leakage
Causes
Air lock, water hammer
Aging seals
Loose supports or piping
Solutions
Vent air and clear blockages
Replace sealing rings/gaskets
Tighten piping and supports
Simple On‑Site Troubleshooting Rules
Flux drops → heavy fouling → backwash first, then chemical clean
High TMP → fast clogging → reduce load and strengthen cleaning
Poor quality → broken/leaking membrane → leak test and replace modules
Frequent scaling → add antiscalant + acid clean
Biofilm buildup → disinfect + alkaline clean