【作者】 李楠；

【导师】 任南琪；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2010， 博士

【摘要】 生物除磷工艺是一种经济有效地控制水体富营养化的手段,在全世界范围的污水处理厂被广泛应用。但在实际工程中,生物除磷工艺稳定性较差。温度是影响生物除磷工艺的重要参数,在温度低于10℃的低温环境,有大量生物除磷失效的报道。本研究考察了低温运行的生物除磷系统的性能,分析低温条件下生物除磷反应器中的微生物群落结构、功能微生物、聚磷污泥活性以及磷去除途径的特异性,从生物去除和生物诱导的化学去除等方面分析低温对磷的去除机制的影响。在5℃条件下启动生物除磷反应器,发现低温条件下通过A/O方式运行的SBR可以实现聚磷菌在反应器中的富集,反应器启动所需的时间为31d。温度越低,反应器启动需要的时间和污泥龄越长。5℃的生物除磷反应器在稳定运行后,对磷酸盐的去除率在85%左右,15℃的SBR除磷效率为95%,而25℃的除磷反应器磷酸盐的平均去除率为78%。污泥龄对低温生物除磷系统的性能有很大影响。在5℃,将反应器的污泥龄从30d降到15d后,生物除磷的性能严重恶化,聚磷菌逐渐从反应器中被洗出。通过模型计算低温生物除磷反应器适宜的污泥龄,发现5℃时生物除磷反应器的洗出污泥龄为12d,稳定污泥龄为18d,即在5℃要获得稳定高效的生物除磷性能,必须保证反应器的污泥龄在18d以上。低温生物除磷系统中聚磷菌的代谢受到了pH的影响。厌氧释磷能力随着pH的升高而加强。pH在6和8之间变化时,乙酸吸收和PHB的合成能力也随着pH升高而加强,但是当pH升高到8.5时,聚磷酸盐分解释放的能量主要用于克服细胞膜两侧电势差(Δ? ),导致PHB合成动力不足,从而抑制了好氧段磷的吸收。在pH为8时,生物除磷系统实现了充分的释磷和吸磷,并取得了最好的除磷效果。在不同pH下长期运行生物除磷反应器,发现pH影响了生物除磷系统的微生物种群结构。在酸性条件下(pH为6)长期运行的生物除磷系统中聚糖菌大量存在;而pH为8时,聚磷菌在活性污泥中占有优势地位。发现低温条件下EPS对磷的去除起重要作用。5℃时,平均每个运行周期通过EPS去除的磷达到2.4mg,EPS去除的磷占磷去除总量的13%。而15和25℃通过磷酸盐沉淀在EPS表面富集而去除的磷分别占磷去除总量的4.2%和4.8%。低温条件下有利于磷酸根与金属结合生成沉淀并附着在EPS中。在不同温度生物除磷系统中,通过微生物代谢和聚磷菌过量吸收进行的胞内磷去除均占主导作用,达到磷去除总量的80%以上。在15℃,生物除磷系统通过微生物的胞内作用去除的磷最多,典型周期SBR反应器通过微生物的胞内作用去除的磷为18.2mg,除磷效率也达到了95%。应用分子生物学技术考察了低温运行的生物除磷系统在微生物群落结构和功能微生物的特异性。FISH技术结合反应器运行的结果显示,5℃条件下,较短的污泥龄(15d)容易造成聚磷菌洗出,维持较长的污泥龄有利于聚磷菌的富集。5℃,污泥龄为30d的生物除磷反应器中聚磷菌含量最高,在活性污泥微生物中约占64.3%。应用PCR-DGGE技术考察了温度对生物除磷系统功能微生物的影响,发现不同温度的生物除磷反应器功能微生物有差异,5、15和25℃条件下运行的的生物除磷反应器中都存在的功能微生物为Uncultured beta proteobacterium gene for 16S rRNA clone:OS1L-4和Gemmatimonas aurantiaca。Uncultured actinobacterium clone GCP18大量存在于25℃的生物除磷反应器中,在5℃的生物除磷反应器中,Tetrasphaera elongata的含量很高,可能为低温条件下起主要作用的功能菌。考察了温度对富磷污泥反应动力学的影响,发现聚磷菌的厌氧反应活性在25℃时最大,好氧反应活性在5-30℃随着温度的升高而提高。温度对生物除磷系统中微生物动力学反应有较大影响,生物除磷系统在低温运行时,聚磷菌的活性最差。厌氧乙酸吸收、PHB合成和磷酸盐释放的温度系数分别为1.056、1.047和1.053,好氧的磷酸盐吸收和PHB消耗的温度系数分别为1.057和1.066。更多还原

【Abstract】 Biological phsophorus removal (BPR) process has been widely implemented in many wastewater treatment plants (WWTP) worldwide as a economical and effective method to control wastewater eutrophication. However, the lack of stability is still a noticeable problem. There were a lot of reports about the loss of phosphorus removal capability for BPR (biological phosphorus removal) processes operated at temperatures under 10 oC. Sludge characteristics, microbial community structure, kinetics and mechanism of P removal were investigated in BPR system operated at low temperature, and biological phosphate removal and biologically induced phosphorus precipitation characteristics was analysed at low temperature.In BPR reactors started up at 5°C, PAOs were acclimated in SBR when the reactor was operated at A/O mode under 5°C, and the start up time was 31d. Lower temperature resulted in longer start up time. When the BPR reactor was well started up, the phosphorus removal efficiency was ~85%. The phosphorus removal in this reactor was lower than that operated at 15°C, but larger than the reactor operated at 25°C.SRT had a great effect on performance of BPR system. For SBR operated at 5 oC, the phosphorus removal capability seriously deteriorated after the SRT reduced from 30 days to 15 days, and PAOs were simultaneously washed out from the reactor gradually. Wash-out SRT (or minimal SRT) and stable SRT for BPR at were calculated according to the model proposed by Brdjanovic. Wash-out SRT were 12 for BPR reactor operated at 5 oC, while stable SRT was 18 days. Longer stable SRT was demanded for BPR operated at lower temperature.Variation of pH had effects on PAOs metabolization characteristics in BPR operated at low temperature. Anaerobic phosphorus release capacity increased with pH at 5 oC in the range of 6 to 8.5. Anaerobic acetate uptake and PHB formation capacity enhanced with the pH increasing from 6 to 8. When the pH increased to 8.5, too much power supplied by degradation of poly-P was used to overcomeΔ? . Less poly-β-hydroxybutyrate (PHB) was synthesized in anaerobic phase inhibited consequent uptake of orthophosphate in aerobic phase. Highest phosphorus removal efficiency was obtained in batch tests at pH 8 accompany with typical phosphorus release and uptake. BPR performance and microorganisms were monitored in 5 oC SBR operated at pH 6 and 8 to investigate pH effect on microbial community structure of BPR at low temperature. Acidic condition (pH=6) favored the growths of GAOs, while PAOs take predominant roles in BPR systems at pH 8.It is the first time to investigate that extracellular polymeric substance (EPS) played an important role for phosphorus removal in BPR system. Phosphorus removed by EPS removal achieved the highest value at 5 oC (2.4 mg P per cycle). Low temperature was propitious to EPS phosphorus removal, accounting for 13 % of total phosphorus removal at 5 oC, which was much higher than that at 15℃(4.2%) and 25℃(4.8%). Phosphorus removed by intracellular absorption was demonstrated as the dominant part (>80%) in total phosphorus removal operated under different temperatures. Intracellular phosphorus contents reduced with the increase of temperature. At 15℃, the highest total phosphorus removal rate of 95 % was obtained due to the highest intracellular phosphorus absorption of 18.2 mg P in a typical cycle.Molecular techniques were applied to investigate the microbial community characteristics and founctional microbes at low temperature. Results of FISH showed that shorter SRT (15 days) was unfavorable at 5℃for BPR due to the wash-out of PAOs to some extent. At 5 oC and 30 days SRT, the highest PAOs content among total bacteria reached 64.3%. PCR-DGGE was applied to investigate the temperature effects on founctional microbes. Founctional microbes of BPR differed with temperature. Uncultured beta proteobacterium gene for 16S rRNA clone:OS1L-4.and Gemmatimonas aurantiaca existed in SBRs operated at 5, 15 and 25 oC as founctional microbes. Uncultured actinobacterium clone GCP18 existed in a large amount in BPR operated at 25 oC, while Tetrasphaera elongata, which had a large population in BPR reactor operated at 5 oC, might be the main founctional microbe at low temperature.Anaerobic specific phosphorus release rates (SPRR), specific acetate uptake rates (SCUR) and specific PHB formation rates increased with the temperature in the range of 5 to 25 oC, and decreased at 30 oC. Temperature coefficients for P-release, acetate uptake and PHB formation were 1.056, 1.047 and 1.053, respectively. Aerobic specific phosphorus uptake rates (SPUR) and specific PHB consumption rates increased with the temperature in the range of 5 to 30 oC, and temperature coefficients for these two aerobic reactions were 1.057 and 1.066.更多还原