Application of High-Efficiency Reverse Osmosis Technology in Reclaimed Water Treatment in Power Plants

Because of the poor quality of the operational water (urban reclaimed water) of one power plant in Hebei, China, a high-efficiency reverse osmosis (HERO) system with foreign patents is utilized for advanced treatment of the reclaimed water. The influence of the main factors (including the alkalinity and the suspended solid content of the feed water, the flux, and the pH of the concentrated water) on the performance of the HERO system were studied. The high alkalinity (high concentration of carbonate) of the feed water resulted in HERO scaling, and the low alkalinity caused the penetration of hardness through the weak acid ion exchangers and, therefore, also caused HERO scaling. The high suspended solid content of the feed water caused rapid decrease in the product flux of HERO. The low concentrated water flux also decreased the product flux. As the pH of the concentrated water became higher, the stability of the HERO operation increased. Based on the pH endurance of the membranes and the characteristic of the high-pH operation of the HERO system, the water production was basically stable when the pH of the concentrated water lay between 10.5 and 10.8. Affected by the ammonia in the reclaimed water, the pH of the product water was higher than that of the feed water. The pH of the feed water was higher than that of the concentrated water. When the pH of the concentrated water was above 10.8, the pH values were close to one another. The results of the chemical cleaning experiments indicated that hardness, phosphorus, ammonia, silicon dioxide, and iron ions were the main influencing chemical factors of HERO, in which the former three formed a sediment of magnesium ammonium phosphate, and the latter two formed an iron silicate sediment.