Production of soluble microbial products and their impact on biological phosphorus removal systems operated under different environmental stress conditions.

• Main Authors: Jheng-Hong Wu, 吳政鴻
• Other Authors: Wei-Chin Chang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/51365650993347998156

碩士 === 雲林科技大學 === 環境與安全工程系碩士班 === 97 === Microorganisms in biological treatment system biodegrades organic material and also generates soluble microbial products (SMPs). SMPs may be produced directly from substrate metabolism or from biomass decay. SMPs contain a variety of organic matter and their biodegradability is poor than influent substrates. The past researches showed that the remaining soluble organic matter of the effluent was actually SMPs. In addition, SMPs exhibited biological toxicity which inhibited acetate uptake and nitrification capacity, reduced microbial activity and affected the flocculating and settling properties of sludge in biological wastewater treatment. SMPs is mostly discussed to influence on carbon removal and nitrification of the biological treatment system, but seldom has report the inhibitory effect of SMPs on enhanced biological phosphorus removal (EBPR). In order to confirm the reasons why SMPs influence phosphorus removal system, we operated two anaerobic–aerobic activated sludge reactors on different SRT (5 day and 15 day) and accumulate SMPs in their supernatant by lengthen their hydraulic retention time (HRT). Then anaerobic and aerobic batch experiments were conducted by using the supernatant from each reactor. Finally, this research investigate the effect of SMPs on anaerobic phosphorus release and aerobic phosphorus uptake of PAOs, and compare the effect of SMPs on the phosphorus removal efficiency from different SRT system. Experimental results showed that lengthens HRT can increase SMPs and lead to reduce treatment efficiency of biological phosphorus removal system. Batch experiments further confirmed that the existence of SMPs in the biological phosphorus removal system doesn’t affect the function of anaerobic phosphorus release, but direct inhibit the capacity of aerobic phosphate uptake. Batch experimental results also showed that are very similar under different concentrations of SMPs to the use of PHAs by PAOs. This illustrated SMPs can directly block the path of PAOs phosphate uptake. The further calculation of inhibition kinetics of SMPs on aerobic phosphorus uptake display that inhibition intensity of aerobic phosphate uptake from SRT 15 day is higher than that from SRT 5 day. The past research indicated that different environmental stress conditions imposed on the anaerobic treatment system can increase the concentration of effluents in SMPs. This study tries to operate two anaerobic–aerobic activated sludge reactors, to explore the production of SMPs and their impact on phosphorus removal by imposing different environmental stress (nutrient deficiency and presence of the toxic compounds) on biological phosphorus removal system. Experimental results showed that the nutrient deficiency will result in increased of SMPs and affect PAOs cell metabolism, leading to the loss of function to removal carbon and phosphorus. When removing the external environment stress (nutrient added back), the system still unable to respond to phosphorus removal capabilities, and population of GAOs become the dominant. The presences of toxic substances will also increase the production of SMPs in EBPR, the increase may be due to the biomass decay or hydrolysis of extracellular polymeric substrates. In addition, by adding heavy metals (Zn2+, Cr6+) batch experiments showed that heavy metals will directly affect anaerobic phosphorus release of PAOs, resulting in decrease of substrate uptake rate and PAHs generation, thereby causing the deterioration of phosphorus removal. The further calculation of the inhibition kinetics of heavy metals on anaerobic phosphorus release and aerobic phosphorus uptake display that Zn2+ has a higher inhibition on the SRT 5 day biological sludge and Zn2+ effects of PAOs is higher than Cr6+.