Reverse osmosis (RO) equipment is a core component in industrial water purification, brackish water desalination, and domestic water supply purification. The total dissolved solids (TDS) value of the permeate is a crucial indicator for measuring the desalination effect and operational status of the RO equipment. Under normal operating conditions, the TDS of the permeate from RO equipment should remain stable at a low level. However, if the TDS is high, fluctuates upwards, or desalination fails to meet standards, it will directly lead to substandard production water and substandard water supply, affecting production operations and water safety.
DIEN Water Treatment: Direct Sales from the Source Manufacturer of Reverse Osmosis Equipment
I. Membrane Element Failure, Aging, or Damage (Core Cause of High TDS)
The reverse osmosis membrane is the core component for desalination. Membrane problems are the primary cause of excessive TDS in the permeate, and most abnormal TDS issues originate from this.
Irreversible Membrane Oxidation Damage: Excessive residual chlorine in the feed water and excessive addition of oxidizing agents can damage the desalination functional layer on the surface of the reverse osmosis membrane, causing permanent membrane element failure and a precipitous drop in desalination rate.
II. Abnormal Equipment Operating Parameters (High-Frequency Controllable Faults)
Abnormal Inlet Water Temperature: For every 1°C drop in water temperature below the standard temperature, membrane flux and desalination performance decrease simultaneously. Failure to implement constant temperature treatment in low-temperature winter environments is a common cause of increased TDS in the permeate.
Excessively High System Recovery Rate: Blindly increasing the equipment recovery rate can lead to highly concentrated salt in the concentrate, increasing the salt concentration gradient on the membrane surface, resulting in salt ion permeation and ultimately causing TDS levels in the permeate to exceed standards.
Solutions:
Calibrate the high-pressure pump operating pressure, clean blockages in the pipelines, and match the operating pressure to the standard based on the raw water TDS to ensure sufficient desalination power.
III. Pretreatment System Failure (Hidden Long-Term Faults)
Pretreatment Filter Media Failure:** If quartz sand, activated carbon, and softening resin are not replaced or regenerated for a long time, their filtration and softening capabilities are lost, leading to excessive turbidity, hardness, and impurities in the inlet water, increasing the operating load on the reverse osmosis membrane.
- Excessive SDI and turbidity in feed water: Raw water containing large amounts of colloids, suspended solids, and silt enters the membrane system directly without effective filtration, causing membrane surface clogging and fouling, and damaging membrane screening performance.
- Untreated scaling and fouling: High feed water hardness and alkalinity, insufficient or discontinued scale inhibitor dosage, lead to rapid scaling on the membrane surface, clogging membrane pores and reducing desalination rate.
Solutions
- Regularly replace pretreatment filter media and regenerate softening resin to ensure normal pre-filtration and softening functions;
Precisely add scale inhibitor according to the raw water quality, and regularly clean membrane elements to remove scale and contaminants from the membrane surface.
Reverse Osmosis Equipment
IV. Improper Equipment Operation and Maintenance and Water Quality Issues
Main Causes
- Long-term equipment shutdown without maintenance: Long-term inactivity of reverse osmosis equipment allows microorganisms and algae to grow on the membrane elements, causing membrane biofouling. After restarting, the TDS in the permeate remains high.
- When the equipment is shut down for an extended period, maintain the membrane elements with proper moisture and antibacterial care, and periodically cycle and flush them.
- According to equipment operation and maintenance standards, promptly conduct alternating acid and alkali chemical cleaning when pressure differential or permeate flow is abnormal.
V. Rapid Troubleshooting Procedure for High TDS (Practical Guide)
Check the membrane housing's sealing performance to check for cross-contamination and leakage.
Assess the degree of membrane element fouling and aging, and determine the cleaning or replacement plan.
High TDS in reverse osmosis equipment permeate is primarily caused by four categories: membrane element malfunction, abnormal operating parameters, pretreatment failure, and improper operation and maintenance. In daily operation, standardized parameter adjustments and regular maintenance can significantly reduce the probability of TDS exceeding standards, ensuring the long-term stable production of compliant purified water from the reverse osmosis equipment.
