【作者】 李金娟；

【导师】 赵林；

【作者基本信息】 天津大学 ， 环境科学， 2012， 博士

【摘要】 采用乙酸钠为碳源,通过好氧动态供料法对活性污泥进行驯化,富集聚羟基脂肪酸酯(PHA)积累菌,研究驯化后活性污泥积累PHA的规律。结果表明,瞬时投加高浓度碳源(931.5mg C/L),活性污泥合成聚羟基丁酸酯(PHB)。feast阶段内乙酸钠去除94%,其中53.4%的乙酸钠被转化为PHB,PHB储藏量为836mg/L。为了进一步提高活性污泥中PHB含量,分别考察F/M(食微比)、溶解氧、氮源对其累积的影响。研究发现:①随着F/M升高,PHB合成量也逐渐增加。当F/M比为2.5mg C L-1/ mg C L-1)时,PHB合成量于8h达最高值1070mg/L;②溶解氧浓度的提高明显加速了底物的吸收,但是适当限制氧气流量有利于PHB的合成。当空气流量为80L/h(KLa为8.93 L/h)时,乙酸钠的PHB转化率最大为0.76;③以氮源为限制因子时,活性污泥生物量的增加主要是由于PHB的合成引起的,PHB的最大积累量达1598mg/L,占的质量分数的65.2%。考察碳源类型对活性污泥合成PHA成分的影响,分别采用乙酸钠、丙酸钠、丁酸单一碳源以及其混合有机酸为碳源,合成PHA。研究发现,以乙酸钠或丁酸为碳源时,合成的PHA为PHB;以丙酸钠为碳源,合成的PHA为聚(3-羟基丁酸3-羟基戊酸3-羟基2-甲基戊酸酯)(P(HB-HV-HMV))共聚物;以混合有机酸为碳源合成的PHA也为P(HB-HV-HMV)共聚物,PHA中HV的含量与丙酸含量线性相关。考察以淀粉酸化液为碳源合成PHA的情况。在pH7、厌氧的条件下,有效地转化为丁酸、乙酸、乙醇、丙酸、戊酸。酸化废水经活性污泥合成PHA,合成结束后PHA占污泥干重的34.7%,纯度为96.8%。经分析,此PHA为PHBV,3HV的含量占8.9mol%。此样品熔点为150℃,热分解温度为270℃,具有较好的热稳定性。为了使淀粉液成为合成PHA的理想碳源,进一步研究了淀粉液的酸化条件(温度、HRT、OLR、pH)。研究发现最佳酸化温度为35℃;HRT主要影响酸化液中丁酸、乙酸的含量;OLR主要影响酸化液中乙醇的含量;而pH对酸化产物类型的影响较大,在pH为5.5的条件下,酸化液中丙酸含量提高,在低pH条件下,乙醇含量提高,在高pH条件下,丁酸含量高。因此通过调控酸化条件,提高酸化废水中丙酸的含量,使其成为活性污泥合成高性能PHA的理想碳源。更多还原

【Abstract】 A sequencing batch reactor was conducted by aerobic dynamic feeding with acetate as carbon source to domesticate activated sludge to enrich PHA -accumulating microorganisms. After being domesticated, the PHB accumulation was researched. The results showed that feeding by high acetate dosage of 931.5mg C/L; the activated sludge produced PHB. During feast period, 94% acetate was removed, in which a fraction of 53.4% of acetate was transformed to PHB. The PHB content of activeated sludge is 836mg/L.To improve the PHB content in activated sludge and to find the optimal condition for PHB synthesization. Three critical factors: F/M (food/microbiology), dissolved oxygen and nitrogen deficiency was evaluated. The results showed that:①with the F/M increasing, the maximum PHB production increased correspondingly. Feeding by a high dosage acetate with a F/M (Food to Microorganisms) of 2.5 mg C L-1/ mg C L-1, PHB production reached its maximum value of 1070mg/L at 8 h. when F/M ratio above 2.5 mg C L-1/ mg C L-1, PHB content didn’t increase anymore because of the long time of storage reaction (excess 8 hour).②the rate of substrate uptake increased with the increase of dissolved oxygen concentration, but a moderate dissolved oxygen supply appears to be appropriate for the most efficient conversion of acetate to PHB. At a moderate dissolved oxygen supply rate of 80L/h(KLa 8.93 L/h), a much higher conversion of 0.76 was reached.③Subjected to nitrogen -limiting conditions, the growth of activated sludge is manly due to the storage of PHB, yet the residual cell biomass didn’t increase. Under the nitrogen-limiting condition, the maximum value of PHB storage was 1598mg/L, 65.2% of activated sludge.To research the effect of carbon source on PHA stucture, unique carbon source aceatate, propionate, butyrate and mixed carbon of them was used to produce PHA, respectively. Results showed that using acetate or butyrate as carbon source, PHB was obtained, when the carbon source was propionate or mixed carbon, the terpolymer of HB/HV/HMV was obtained. And the HV content of PHA was linear with the propionate content.The production of PHA by starchy wastewater was investigated. The results showed that the starchy wastewater was almost acidificated to butyric, acetic, propionic, valeric acids and ethanol. At the second stage, activated sludge was fed by the organic acids discharged from the acidification reactor to produce PHA and 34.7% PHA of sludge was acquired, with a purity of 96.8%. The PHA in the sludge was extracted and its structure and thermal character were analyzed. The results showed that the PHA was composed of HB and HV and the PHA had HV content of 8.9 mol%. The results of thermal analysis showed that the melting point was 150℃and the thermal degradation temperature was 270℃. Therefore, feeding by the acidified starchy, the copolymer of 3HB and 3HV was produced by activated sludge, and the PHBV had the character of lower melting-temperature and good thermal stability.The acidogenic react was investigated for the optimal PHA production using the acidifitied starchy. Results showed that the degree of acidification was higher when temperature was controlled at 35℃. HRT influence the acetate and alcohol content and OLR influence alcohol content. However, the type of fermentation was maily influeced by pH. Propionic acid type fermentation occurred at pH about 5.5. Ethanol fermentation occurred at lower pH. Butyrate fermentation was dominant with a higher Ph value.therefore,improving the propionic acid content by control the fermentation condition make acidficited starchy a good carbon source for PHA synthesis.更多还原