| Shanxi Province, located in Loess Plateau, is one of the13Chinese provinces that suffer from sever water shortage.. Nowadays, the imbalance between coal richness and the water poverty is the most prominent problem. Although water resource in Shanxi province is scarce, underground karst water resource is rich, which cannot be used as living or industrial water. The salinity and hardness of karst water are3643mg/L and3044mg/L, respectively, in Taiyuan city. The underground karst water can not be directly used, so it needs to be treated by flocculants. In this paper, the appropriate strains were selected and the microbial flocculants were preparated for processing the high-salinity and hardness underground karst water in Taiyuan to reach the industrial standard.In this paper, the growth curve was determined by the unit quality and OD method, and the optimum cultured conditions were selected; the flocculantion factor and activity distribution were determined by the flame atomic absorption and conductance method. The four strains, Geotrichum candidum, Bacillus subtilis, Saccharomyces cerevisiae and Streptomyces griseus, were selected to produce microbial flocculants. Those were cultured for8days in the same culture condition and inoculation, but different culture media. At the same time, the growth curves were measured in order to determine the most optimal growth condition. The daily flocculent activity of the broth and supernatant was measured. The results showed that:â‘ The G. candidum s expansile cultured medium â…¡ was the best expansile medium, and the thalli and supernatant were separated on the4th day;â‘¡The B. subtilis’culture medium â…¡ was the best expansile medium, and the thalli and supernatant were separated on the4th day;â‘¢The S. cerevisiae expansile culture medium IV was the best expansile medium, and B. yeast was separated on2nd day;â‘£The S. griseus’medium â…¡ was selected and the3rd day was the most exuberant stage. The broth and supenatant’s flocculation were along with the microbial activity. The thalli and secretions of G. candidum and B. subtilis and the S. cerevisiae’s thalli were found to have flocculent activity on karst water. S. griseus’flocculent activity was low and difficult to be cultured on a large scale, so no further study was made..The flocculation of G. candidum, B. subtilis and S. cerevisiae were affected by immobilized methods, stirring time and dosage to Kast water near Xiaodian community in Taiyuan. The results described that:â‘ The immobilized balls had better stability and resistance to the pressure and better repeated useness.â‘¡G. candidum’s ball immobilized by SA-gelatin-PVA had better flocculation factor than others. And the G. candidum’s optimum flocculent condition was60min of stirring and at the4g/L dosage. The flocculantion factor of karst water’s salinity was86.25%, and the salinity of the karst water of Taiyuan fell from3643mg/L to506.86mg/L.â‘¢When the dosage of S. cerevisiae’s ball immobilized by SA was4g/L and the stirring time was30min, the karst water’s salinity and hardness fell to2239mg/L and489mg/L, respectively.â‘£When the dosage of B. subtilis’ball immobilized by SA-PVA was1g/L and the stirring time was90min, the karst water’s salinity and hardness dropped to2055mg/L and575mg/L, respectively. In contrast to conventional flocculants, the microbial flocculant has the advantages of simple operation, no second pollution and better flocculation fator and so on.In this paper, the ultraviolet and infrared scanning spectrum was used to analyse the microbial flocculantion mechanism. The results showed that:â‘ the G. candidum’s active flocculent substance and groups were protein and C-H and N-H, respectively.â‘¡B. subtilis’flocculent active substances and groups were protein and nucleic acid and N-H,-CH3and-CH2, respectively. And P=O was stretched vibrated, suggesting that new lipid had been generated.â‘¢The protein and nucleic acid may be the S. cerevisiae’s active substances. And their active groups were N-H, C-N,-CH3and-CH2. After reaction, the N-H was stretch-vibrated, suggesting that a new protein may be generated.This paper made further research on the supernatants’flocculation. The extraction method of microbial flocculants was determined by single factor control method. The results showed that:â‘ G.candidum’s supernatantâ†'Rotary evaporated to the1/10in original volume at50℃â†'In twice the volume of the cooling anhydrous acetoneâ†'centrifugal effect at high speedâ†'crude products.â‘¡the B. subtilis’supernatantâ†'rotationaly evaporated to1/10in the original volume at48℃â†'adjusted the pH to5and added the anhydrous etherâ†'precooling8h at-4℃â†'centrifugal effect at high speedâ†'crude products.The color reaction and a series of related experiments respected the composition of microbial flocculant.â‘ The main components of B. subtilis’ secretion were35%protein and39%amylose. And the main flocculation activity substances may be protein and nucleic acid. And the flocculational activity moiety are-CH2,-CH3,=C-H, N-H and O-H.â‘¡The main component of G. candidum secretion was51%amylose and43%protein. The main active flocculent substance is protein. And the activity moiety was N-H and O-H. |
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