Mechanism Of Synergetic Biosolubilization Of Mid-low Grade Rock Phosphates By Mixed Bacteria

In order to provide the theoretical basis for the difficulty of utilizing the rich mid-low grade rock phosphates, mixed bacteria were used to solubilize the mid-low grade rock phosphates in this study.The main experiments are as follows: 1.Exploration of the mixed bacteria synergistically solubilize the mid-low grade rock phosphatesThe mixed bacteria from two different sources(wheat rhizosphere soil and activated sludge from a municipal wastewater treatment factory) and two different mid-low grade rock phosphates were research objects and the experiment were performed in shake flasks. The results showed that under the initial pH of 7.0, reaction temperature of 25 ℃and the stirring speed of 200 r/min, more phosphorus in the ore could be solubilized by the mixed bacteria when the particle size of the ore was 150 μm and the pulp density was 1%. There were correlations between biomass and P content, pH value and P content, P content was positively related with the biomass in the culture and negatively related with the pH value. 2. Mixed bacteria synergistically solubilize the mid-low grade rock phosphates in the column leaching deviceThe mixed bacteria from activated sludge of a municipal wastewater treatment factory without any screening process and the rock phosphate from Yunnan were research objects in this experiment. Mid-low grade rock phosphate solubilization by the mixed bacteria was studied in this column device. The results showed that column device could be used to study the phosphate solubilization by the bacteria. During the reaction, biomass in the effluent increased, pH maintained in acid range and the P content increased gradually. The results of chemical oxygen demand(COD) concentration in influent and effluent in the operation time 60-67 th days showed that the mixed bacteria in the column consumed large amount of organic matter. The measure of pH in the biofilm suggested that the pH(about 4-5) in the biofilm was nearly consistent with the pH in the effluent. The dissolved oxygen(DO) was depleted at 1100 μm below the biofilm surface, oxygen layer and hypoxic layer both existed in the biofilm. Scanning electron microscope(SEM) analysis were performed after 30 d and 90 d, respectively, and the results showed that biofilm gradually covered the surface of the ore and damaged the structure of the ore. The results of community analysis indicated that community in effluent and biofilm were different. Alphaproteobacteria( 63.19%) was the main community in the effluent, while richer species diversity of the community in biofilm were displayed. 3. Mixed bacteria synergistically solubilize the mid-low grade rock phosphates in the bioreactor deviceThe mixed bacteria from two different sources(wheat rhizosphere soil and activated sludge from a municipal wastewater treatment factory) and two different mid-low grade rock phosphates were research objects in this experiment. Mid-low grade rock phosphate solubilization by the mixed bacteria was studied in this device and phosphate-solubilizing capacities were compared. The results showed that the mixed bacteria from two sources could both effectively solubilize the mid-low grade rock phosphates. More soluable P content was achieved when mixed bacteria reacted with ore 1. When the mixed bacteria from different sources reacted with the same ore, the effect of mixed bacteria from the activated sludge was better than that with soil bacteria. SEM analysis were performed after 30 d, the results showed that the structure of the rock was damaged by the mixed bacteria. The results of community analysis showed a similar species of organisms. However, the content differs under different reaction condition. When soil bacteria solubilized ore 2, Alphaproteobacteria and TM7_class_incertae_sedis were more abundant; when activated sludge bacteria solubilized ore 2, the content of TM7_class_incertae_sedis(34.52%), Gammaproteobacteria(19.84%)were higher than with ore 1.