Effects of wet-dry alternation on organic phosphorus dynamics and sediment characteristics in the intertidal zone of Nansi Lake.

The study of the fractions and distribution characteristics of organic phosphorus in the sediment of the water level fluctuating zone of Nansi Lake is conducive to revealing the transformation of phosphorus in the lake, and has important scientific significance for controlling the eutrophication of Nansi Lake. Based on the sediment of the water level fluctuation zone of Nansi Lake. The improved Hedley continuous grading extraction, ultraviolet-visible spectroscopy and three-dimensional fluorescence spectroscope were used to characterize the structural characteristics and stability of organic molecules in the sediment, and to reflect the differences in the structure and stability of organophosphate in the water level fluctuating zone. Principal component analysis (PCA), Redundancy analysis (RDA) and correlation heat map analysis were used to analyze the correlation between phosphorus and physicochemical index. The results showed that the alternation between wet-dry conditions was more favorable for the release of phosphorus from sediment, compared to continuous inundation conditions. Moreover, the higher the frequency of wet-dry alternations, the greater the release of phosphorus in different forms from the sediment. Wet-dry alternation resulted in a reduction of substituent on the aromatic rings of sediment DOM (dissolved organic matter), and the continuous drying would increase the molecular weight and humidification degree of DOM in the sediment. Correlation analysis showed that NaOH-Po content in sediment was significantly negatively correlated with TP, IP, OP and various organophosphorus forms, indicating a close transformation relationship between phosphorus forms in sediment. The results can provide a scientific basis for controlling the release of endogenous phosphorus and the risk of eutrophication in Nansi Lake.

Applied research on aquatic macrophyte fermentation broth in SBR denitrification.

In the traditional biological process for nitrogen removal, an insufficient carbon source is often the limiting factor. To solve this problem, reed fermentation broth was selected as the source of denitrification carbon for nitrogen removal in a SBR, and the influence of different C/N conditions on the denitrification and the characteristics of bacteria in the reactor were examined. Leaching experiments with reeds employed fluorescence excitation-emission spectrophotometry and revealed that the reed material had a high capacity for carbon release, the average dissolved organic carbon release content proportion was 11.3 mg/g, and the dissolved organic matter mainly consisted of humic acid-like compounds. Using reed fermentation broth as an additional carbon source promoted the denitrification of wastewater by microbes. When reed fermentation broth was added at a C/N ratio of 6, the best nitrogen efficiency for nitrogen removal was 88.3-96.4%. Analyses of microbial diversity indicated that in the SBR reactor, the relative abundance of denitrifying bacteria at the genus level reached 38.5%. These results revealed that reed fermentation broth promoted the growth of anaerobic denitrifying bacteria and improved the efficiency of denitrification. The findings will contribute to a better understanding of the use of reed fermentation broth as an external carbon source that increases the efficiency for denitrification of wastewater. PRACTITIONER POINTS: Using fluorescence excitation-emission spectrophotometry and parallel factor analysis to evaluate the supply capacity of DOMs released from reed. Research the feasibility of reed fermented broth as external carbon source under the condition of extremely low carbon source. Provides theoretical guidance for deep denitrification in sewage treatment plant with SBR process.