Prompt Description

Illustration: A schematic diagram of the synergistic mechanism of "phosphorus pre-recovery - FO membrane VFA retention - ammonia nitrogen migration" is constructed by combining Zeta potential, FTIR characterization results, and full-process performance data. The core synergistic logic can be divided into three closely linked steps to achieve full-chain synergy of "water quality optimization - interface regulation - substance distribution": The first step: Water quality optimization synergy of phosphorus pre-recovery. The vivianite method achieves efficient phosphorus recovery through the crystallization reaction of Fe²⁺ and PO₄³⁻. At the same time, it removes some organic pollutants and colloids through crystal adsorption, reduces wastewater turbidity, ionic strength, and pollutant load, avoids inorganic scale deposition and aggravated organic pollution during subsequent FO membrane separation, and provides a stable influent water quality basis for efficient FO membrane separation. The second step: Regulation synergy of membrane surface characteristics. Phosphorus pre-recovery avoids the modification effect of inorganic scale on the membrane surface and maintains the original strong negative charge characteristics of the membrane surface. It strengthens the directional retention of VFA⁻ through Donnan repulsion. At the same time, the electrostatic attraction of the membrane surface negative charge to NH₄⁺, combined with the osmotic pressure drive of the draw solution, accelerates the permeation and migration of NH₄⁺ and water molecules, and realizes the synchronous recovery of ammonia nitrogen and water. In addition, phosphorus pre-recovery reduces the adsorption of organic pollutants on the membrane surface, maintains membrane flux stability, and further improves the synergistic efficiency of "retention-migration". The third step: Full-process synergy of substance migration. The PO₄³⁻ removed by phosphorus pre-recovery does not chemically react with VFA and ammonia nitrogen, avoiding the loss of target resource components. VFA is directionally retained on the feed liquid side to achieve enrichment, and ammonia nitrogen permeates through the membrane into the draw solution side to achieve recovery. The migration paths of the two do not interfere with each other and complement each other, forming a precise substance distribution pattern of "retention-migration", and ultimately achieving efficient synergy in wastewater resource utilization.