RO reverse osmosis concentrate evaporation treatment
RO systems are widely used in industrial pure water, municipal wastewater reuse, and seawater desalination. Their concentrate typically contains high concentrations of salt and recalcitrant organic matter; direct discharge would cause environmental pollution and waste water resources. Evaporation is the mainstream technology for achieving zero discharge of RO concentrate.
Wastewater characteristics
● TDS range: 10,000～80,000 mg/L, due to significant differences in upstream water quality;
● Contains organic matter: COD is usually between 200 and 5000 mg/L, and organic matter is prone to foaming during evaporation;
● High silicon content: SiO₂ can reach 50-200 mg/L, which easily forms silicon scale at high temperatures, making it one of the most difficult scales to remove through evaporation;
● Relatively small water volume: Suitable for single, compact systems such as MVR.
Processing flow
| RO concentrate evaporation treatment process RO concentrate → Pretreatment (pH adjustment/scale inhibitor addition/silicon removal) → MVR evaporation and concentration (80%~90% volume reduction) → Forced circulation evaporation and crystallization → Centrifugal salt separation → Solidification and landfilling or resource recovery of impurities Condensate: The water quality is close to pure water, and all of it is reused, achieving zero discharge. |
Key Processes
● MVR Priority: RO concentrate volume is relatively small and fluctuates little, while MVR has significant advantages in low energy consumption (30~60 kWh/t), and its operating cost is much lower than that of multi-effect evaporation.
● Silica removal pretreatment: pH adjuster and flocculant are added before entering the MVR to precipitate and remove colloidal silica, preventing silica scaling that would lead to frequent cleaning.
● Defoaming control: RO concentrate containing organic matter is prone to foaming during evaporation, so a demister or defoamer needs to be installed in the evaporator.
● Crystallized salt management: Mixed salts have complex compositions and poor economic efficiency in salt separation. They are usually evaporated and sent to hazardous waste landfills.
