聚羟基烷酸脂论文两段式和三段式工艺制取聚羟基烷酸酯的试验研究模板.doc

聚羟基烷酸脂论文：两段式和三段式工艺制取聚羟基烷酸酯试验研究

【汉字摘要】聚羟基烷酸酯(PHA)是一类羟基脂肪酸聚合物,当外界环境较恶劣时,部分微生物能够在体内以内碳源形式贮存PHA。PHA含有生物相容性和可生物降解性,同时依据单体组分不一样还能够含有同石化塑料相类似多个物理性质,能够替换现行难降解塑料,以此可缓解环境固体废弃物污染。然而现在PHA商业化生产全部采取纯菌发酵方法,成本较高,阻碍了PHA大规模应用。采取活性污泥混合菌群生产PHA能够采取廉价有机废物为底物,有望大大降低PHA生产成本。两段式PHA生产工艺包含有机废物厌氧酸化和PHA生产两步,后者在时间上分为污泥适应阶段和PHA积累阶段,适应阶段采取均衡营养百分比而PHA积累阶段则限制进水中营养元素。本研究发觉在PHA积累阶段一步降低进水中80%(相对于均衡百分比)氨氮,比逐步降低能够更有效促进PHA积累;在每七天期底物全部能够消耗完成条件下,不管底物为乙酸钠还是污泥水解液,该阶段反应器厌氧-好氧运行和好氧运行得到结果几乎没有区分;研究还发觉适应期污泥龄较长时能够确保反应器长时间稳定运行,而污泥龄较短时易引发污泥膨胀,污泥龄低于5天引发污泥膨胀会使得污泥产PHA能力下降。以污泥水解液为底物时,其中VFAs能够得到快速吸收,PHA积累和其中氨氮水平有很大关系。三段式PHA生产工艺包含有机废物厌氧酸化、菌群富集和PHA积累,其中菌群富集是最关键一步。本研究以乙酸钠为底物考察以SBR富集产PHA菌群时,发觉反应器易于发生污泥膨胀。在污泥龄为1天、底物负荷较高(6.6 g COD/L/d)时,反应器膨胀很严重,大量泡沫产生,污泥很快丧失了产PHA能力;而污泥龄为10天、负荷较低(2.7 g COD/L/d)条件下得到膨胀污泥则含有较高PHA合成能力,好氧SBR运行102天时污泥积累PHA最大含量达成了53%,PHA平均积累速率为0.19 mg COD/mg X/h,PHA产率为0.76 mg COD/mg COD,而和此SBR同时运行厌氧-好氧SBR则运行55天左右后忽然瓦解,污泥浓度甚至不足500 mg/L。以蔗糖模拟糖蜜废水经厌氧酸化用于PHA合成时,产酸反应器开启运行1个月后逐步稳定为乙醇型发酵,此时出水经中空纤维膜过滤后用于SBR富集产PHA混合菌群和PHA积累,实现了生物制氢和PHA合成系统耦合。SBR运行负荷为4.2-4.5 g COD/L/d,污泥龄为10天,开启运行1个月内污泥浓度从3300 mg/L增大到8000 mg/L以上,尽管底物充盈时溶解氧控制于3.0 mg/L左右,然而30天时SBR仍然发生了污泥膨胀,这可能是污泥浓度过大造成。对比发觉,膨胀后污泥在底物吸收、PHA合成和生长方面比非膨胀污泥快了1倍左右。本试验在SBR运行25天时,系统每消耗1 kg COD蔗糖,约生产16 L氢气和0.1 kg CODPHA,其中单体HV质量比约占24%左右。
【英文摘要】Polyhydroxyalkanoates (PHAs) are a class of polymers, which can be accumulated as internal carbon sources by part microorganisms under adverse circumstances. PHAs are biocompatible and biodegradable and can also possess the similar properties with the petro made plastics, which enables them to substitute the current plastics to reduce solid wastes. However, PHAs in market are all commercially produced by pure cultures, which bring about high costs and hampered their large-scale application. PHA production by mixed microbial cultures can be completed in open reactors and future more, more cheap organic wastes can be used. This would make cost reduction possible.Two-stage PHA production process includes acidogenic fermentation of organic wastes and PHA production, and the latter is composed by sludge acclimation and PHA accumulation. In sludge acclimation, nutrients are balanced while in PHA accumulation, nutrients are unbalanced. In this study, results showed that direct limitation of ammonia by 80% (compared with balance level) in influent could better stimulate PHA accumulation than gradual limitation. When there was no substrate left in every cycle, little difference was observed in PHA accumulation between anaerobic-aerobic and aerobic operation with substrate as acetate or sludge alkaline fermentation liquids. It can also be drawn that long sludge retention time would guarantee longterm stability of the reactor, while low sludge retention time would bring about sludge bulking. Especially, when sludge retention time was lower than 5 days, the PHA storage capacity would be damaged. VFAs could be uptaken rapidly and the PHA accumulation depended highly on the level of ammonia when the substrate was sludge alkaline fermentation liquids.Three-stage PHA production process includes acidogenic fermentation of organic wastes, culture selection and PHA accumulation, and stage of culture selection is the most important. It was observed that bulking sludge was easily established when selecting cultures in SBR with actate as substrate. Under SRT of 1d and high organic loading rate (6.6 g COD/L/d), the bulking was more severe with a great deal of foam and poor PHA storage ability. While, under SRT of 10 d and low organic loading rate (2.7 g COD/L/d), bulking sludge possessed high PHA storage capacity. After 102 days’operation, sludge from SBR could accumulate PHA to 53% of TSS, under ammonia starvation, with average storage rate of 0.19 mg COD/mg X/h and yield of 0.76 mg COD/mg COD. However, another SBR operated in parallel with anaerobic-aecobic pattern suddenly failed after 55 days’operation.When using cane sugar to simulate molassess as the substrate, after anaerobic fermented, for PHA production, the CSTR gradually stablized towards ethonal-type fermantation one month after startup. The effluent was clarified with hollow fiber membrane and then was used for culture selection and PHA accumulation, thus coupling bio-hydrogen production with PHA production system was achieved. The TSS in SBR rised up to more than 8000 mg/L from 3300 mg/L with organic loading rate of 4.2-4.5 g COD/L/d and SRT of 10 d. Although DO was maintained above 3 mg/L in feast phase, sludge bulking still happened after 30 days’operation. This may be caused by high sludge concentration. Bulking sludge exhibited higher rates in substrate uptake, PHA storage and biomass proliferation than well-settling sludge, about 2 times than the latter. When SBR run 25 days after inoculation, the whole system could produce 16 L H2 and 0.1 kg COD PHA using 1 kg COD cane sugar. The HV weight proportion of PHA was 24% approximately.
【关键词】聚羟基烷酸脂 混合菌群 污泥膨胀 生物制氢 PHA合成
【英文关键词】polyhydroxyalkanoates mixed microbial culture sludge bulking bio-hydrogen production PHA synthesis
【目录】两段式和三段式工艺制取聚羟基烷酸酯试验研究

摘要

4-6

Abstract

6-7

第1章 绪论

11-31

1.1 课题背景

11-12

1.1.1 课题起源

11

1.1.2 课题研究目标和意义

11-12

1.2 PHA 概述

12-19

1.2.1 PHA 结构和性质

12-14

1.2.2 细胞储存PHA 微生物学意义

14-15

1.2.3 微生物合成PHA 代谢机制

15-18

1.2.4 PHA 提取回收

18-19

1.3 混合菌群合成PHA 中国外研究现实状况

19-29

1.3.1 底物选择

19-20

1.3.2 工艺步骤

20-22

1.3.3 工艺运行策略

22-25

1.3.4 影响原因

25-29

1.4 关键研究内容

29-31

第2章 试验材料和方法

31-36

2.1 试验装置及运行工况

31-33

2.1.1 试验装置

31-32

2.1.2 关键设备仪器

32-33

2.2 检测方法

33-36

2.2.1 PHA 检测

33

2.2.2 乙醇-VFAs 检测

33-34

2.2.3 气体成份检测

34

2.2.4 其它常规指标测定和分析方法

34-36

第3章 两段式PHA 制取工艺优化

36-49

3.1 氨氮限制方法对PHA 积累影响

36-39

3.1.1 试验工艺控制

36-37

3.1.2 污泥性状变迁

37-38

3.1.3 限制进水氨氮下PHA 循环积累

38-39

3.2 PHA 积累期厌氧-好氧和好氧运行方法对比

39-41

3.2.1 试验工艺控制

39-40

3.2.2 底物消耗和PHA 积累

40-41

3.3 短污泥龄、短周期污泥适应期

41-45

3.3.1 试验工艺控制

42

3.3.2 污泥性状变迁

42-43

3.3.3 底物消耗和PHA 积累

43-45

3.4 污泥水解液用于两段式工艺

45-48

3.4.1 试验工艺控制

45-46

3.4.2 底物为污泥水解液时PHA 积累情况

46-48

3.5 本章小结

48-49

第4章 以乙酸钠为底物富集产PHA 混合菌群

49-63

4.1 试验工艺控制

49-50

4.2 第一阶段SBR 运行情况

50-51

4.3 膨胀污泥合成PHA

51-58

4.3.1 富集反应器污泥膨胀

52

4.3.2 厌氧-好氧运行SBR 表现

52-53

4.3.3 好氧运行SBR 表现

53-54

4.3.4 两SBR 中PHB 含量改变

54-55

4.3.5 两SBR 富集污泥积累PHB

55-57

4.3.6 PHB 积累过程中膨胀污泥性状改变

57-58

4.4 污泥增殖-PHA 积累循环模式

58-61

4.4.1 试验工艺控制

58-59

4.4.2 污泥增殖

59-60

4.4.3 PHB 积累

60-61

4.5 本章小结

61-63

第5章 三段式PHA 制取工艺初步探索

63-76

5.1 试验工艺控制

63-65

5.1.1 CSTR 运行工况

63-64

5.1.2 SBR 运行工况

64

5.1.3 PHA 积累试验

64-65

5.2 CSTR 开启及稳定运行

65-66

5.3 SBR 开启运行监测

66-69

5.3.1 接种后污泥浓度及SVI 改变

66-67

5.3.2 SBR 一周期参数改变

67-68

5.3.3 未膨胀污泥和膨胀污泥合成PHA 对比

68-69

5.4 PHA 积累试验

69-73

5.4.1 进水底物浓度对PHA 积累影响

69-71

5.4.2 进水底物pH 对PHA 合成影响

71-72

5.4.3 SBR 运行过程中剩下污泥合成PHA

72-73

5.5 生物制氢和PHA 生产工艺耦合

73-75

5.6 本章小结

75-76

结论

76-77

提议

77-78

参考文件

78-86

致谢

86