Influence of organic matter in fermentation supernatant on process and products of phosphorus recovery via vivianite crystallization

Vivianite crystallization is recognized as an efficient and environmentally friendly approach for phosphorus recovery in wastewater resource utilization. However， in practical phosphorus recovery processes， the dissolved organic matter （DOM） present in the supernatant of sludge anaerobic fermentation may interfere with vivianite crystallization， thereby affecting both the phosphorus recovery efficiency and the product properties. In this study， polysaccharides， proteins， acetic acid， propionic acid， and humic substances were selected as representative organic matter to systematically assess how their types and concentrations affect vivianite crystallization， and to elucidate their impacts on crystal morphologies and structure as well as the associated interaction mechanisms. The results showed that the inhibitory effects of different types of organic matter on phosphorus recovery via vivianite crystallization followed the order of humic substances > proteins > propionic acid > acetic acid > polysaccharides. The presence of humic substances significantly reduced the phosphorus recovery rate and crystal size， and led to the formation of irregular surface deposits on the crystals. This study provides a theoretical foundation for clarifying the interference mechanism of DOM in vivianite crystallization within fermentation broth and offers insights for its regulation. These findings are of great importance for guiding the optimization of the efficient phosphorus recovery processes in real wastewater systems.