典型农业废弃物干式厌氧发酵产氢影响因素的研究

以5种典型农业废弃物(猪粪、鸡粪、秸秆、餐饮垃圾和厨余垃圾)为研究对象,采用干式厌氧发酵产氢技术,研究不同初始pH、温度对产氢潜力和代谢途径的影响。结果表明,当中温、初始pH为7.0时,餐饮垃圾产氢效果最佳,最大累积产氢量为261.96mL,最大产氢速率为15.18mL/h,氢气体积分数最大值为64.61%;当中温、初始pH为6.0时,秸秆产氢效果最好,最大累积产氢量为254.41mL,最大产氢速率为24.50mL/h,氢气体积分数最大值为65.54%。5种农业废弃物干式厌氧发酵产氢的代谢途径均以丁酸型发酵为主。     

酸化餐厨垃圾厌氧消化产氢研究

分析了餐厨垃圾酸化过程中的pH、挥发性脂肪酸(VFA)产量及含水量等参数的变化,考察了酸化餐厨垃圾厌氧消化过程中的产氢情况,并探讨了调节初始pH对酸化餐厨垃圾产氢的影响.结果表明,餐厨垃圾的酸化是一个前期极为快速的过程,经过1d的酸化,新鲜餐厨垃圾的pH就从6.0左右下降到4.5左右,而后pH缓慢下降,经过5～6 d的酸化,pH下降到4.0以下;餐厨垃圾酸化过程中,产生的VFA主要是异戊酸,其浓度变化与VFA的浓度变化趋势较为一致;酸化时间为1、3、4、5、6d的餐厨垃圾体系产生的氢气的最高体积分数呈递减趋势,产氢量也呈现出相同的变化趋势;初始pH对酸化餐厨垃圾体系的产氢影响是很大的,调节到相同初始pH的不同体系,产氢的结果可以相近.因此,pH是酸化餐厨垃圾厌氧消化产氢过程中必须控制的关键因素之一.     

初始pH对原污泥厌氧发酵产氢的影响

市政污泥(简称污泥)厌氧发酵产氢既可解决污泥的出路问题,又能产生清洁能源——氢气,是一种较为理想的处理处置方式。调节污泥适合的初始pH值能够提高污泥的产氢效率。为了考察不同初始pH值对污泥厌氧发酵产氢的影响,将未经任何预处理污泥(原污泥)的初始pH分别调到2.0~12.0,用于批式实验。研究表明:调节原污泥初始pH,适当条件下能促进氢气的生成。初始pH为强酸性条件时,污泥基本不产氢;初始pH在4.0~11.0,污泥总体产氢量也很低;初始pH=12.0条件下,污泥总体产氢量最高,比产氢率达到3.39 m L·(g VS)-1。不同初始pH下污泥的降解均以蛋白质降解为主。酸性条件下,蛋白质及糖类物质有一定降解;中性条件下,蛋白质及糖类物质都得到较好的降解,浓度均较低;碱性条件下,糖类物质的酸化较微弱,但蛋白质却得到较好的降解,降解蛋白质生成的TVFA由于甲烷菌受到抑制而产生积累。     

木薯酒精废水高温厌氧发酵产氢研究

以木薯酒精废水为厌氧发酵产氢底物,以中温(37℃)厌氧颗粒污泥作为接种物.研究了高温条件(60℃)下厌氧发酵产氢的可行性;并比较了60～80℃条件下的累积产氢量,产氢速率和液相发酵产物组成,以确定温度对木薯酒精废水厌氧发酵产氢的影响以及不同温度下厌氧发酵产氢菌的代谢类型.结果表明,60℃时累积产氢量为383 mL(木薯酒精废水用量140 mL)、产氢率为70.0 mL(以每克挥发性固体(VS)计),中温厌氧颗粒污泥适合作为高温条件下木薯酒精废水厌氧发酵产氢的接种物;从60℃升高到80℃时,累积产氢量逐渐下降,最大产氢速率逐渐降低,80℃时产氢完全受到抑翩.70℃为产氢的临界点,低于70℃时厌氧发酵产氢菌的代谢类型属典型的丁酸型发酵,此过程中伴随着大量氢气产生,大于等于70℃时,正丁酸生成受到严重抑制,累积产氢量迅速降低;氢气的产生主要来自于溶解性碳水化合物的分解.     

温度和初始pH对农业固体废物暗发酵产氢的影响

以猪粪、鸡粪、玉米秸秆、餐厨垃圾和厨余垃圾等5种农业固体废物为底物,采用修正的Gompertz模型,研究了典型农业固体废物暗发酵产氢动力学和代谢产物变化规律,探讨了不同温度和初始pH条件下的主要产氢代谢途径。结果表明:温度和初始pH对农业固体废物暗发酵产氢具有显著影响;高温组累积产气量和氢气百分含量显著高于中温组。在55℃高温且pH为6.0的条件下,餐厨垃圾暗发酵产氢效果最佳,累积产气量和氢气百分含量最大,为1 100 mL和73.58%,最大产氢速率和产氢潜力分别为37.11 mL·h~(-1)和660.30 mL;厨余垃圾暗发酵产氢效果次之,鸡粪产氢潜力最差。在暗发酵产氢末期,以鸡粪为底物的代谢产物的氨氮浓度最高,过高的氨氮浓度可能抑制了产氢过程。VFA分析表明:不同底物和条件下丁酸浓度均最高,且含有少量乙醇、乙酸、丙酸等;暗发酵产氢代谢途径是以丁酸型发酵为主的混合型发酵。通过温度、初始pH等非生物性控制因素的优化调控,显著提高了农业固体废物暗发酵产氢潜力和底物利用效率,为生物制氢的技术研发与工程应用提供参考。     

初始pH对产氢发酵液厌氧产甲烷的影响研究

以啤酒厂厌氧颗粒污泥为接种物,对葡萄糖废水产氢后的发酵液进行间歇式中温厌氧发酵产甲烷实验.研究了不同的进水初始pH为5.5±0.2、6.0±0.2、6.5±0.2和7.0±0.2时对产氢发酵液产甲烷的影响,并以产氢发酵液的原始pH(4.2～4.4)作为对照.结果表明:产氢发酵液厌氧产甲烷必须添加一定量的碱加以调节,进水...     

利用有机基质厌氧生物产氢的试验研究

对利用有机基质厌氧生物产氢过程进行了试验研究 ,结果表明 ,污泥种类、基质种类、基质浓度和起始 p H对厌氧产氢反应有显著影响。当校河底泥在以 2 0 g COD/L的果糖为基质 ,起始 p H为 6.5时 ,产氢效果最佳 ,停滞期仅为 5 h,产气速率高达5 0 .1m L/g VSS·h,且可持续 12 h,累积产气量高达 60 4.9m L/g VSS,其中氢气含量约为 5 0 %。半连续试验的结果表明 ,若及时更换和补充基质 ,适当调节 p H,就可实现持续产氢 ,在 16h内平均产气速率可达 60 .0 m L /g VSS· h,氢气含量约为 45 %。     

氢自养生物还原去除地下水中对硝基氯苯（p-NCB）的实验研究

采用批式实验讨论了氢自养还原菌在厌氧条件下,利用氢气作为电子供体还原地下水中对硝基氯苯的可行性及其影响因素。结果表明,氢自养菌能利用氢气生物还原对硝基氯苯,并产生中间产物对氯苯胺,继而进一步还原脱氯产生苯胺,该过程可提高对硝基氯苯的可生化性。对硝基氯苯在初始阶段还原速率较快,最高去除速率达到610μg/（L.d）,随后逐渐降低达到稳定。影响因素实验表明,在一定浓度范围内提高对硝基氯苯浓度对其去除率影响较小,但硝基进一步还原和脱氯效果降低;氢自养菌还原硝基氯苯的最适宜pH值在7.0~8.0之间;水中的硝酸盐和对硝基氯苯对电子供体存在竞争,硝酸盐反硝化对对硝基氯苯还原具有抑制作用。     

初始pH值对泔脚发酵产氢余物甲烷化的强化研究

以城市生活垃圾厌氧消化污泥为接种物,考察了初始pH值为5、6、7和8时对泔脚发酵产氢余物中温(36℃)批式厌氧消化的影响。结果表明,当初始pH值低于7时,随着初始pH值的增大,产氢余物的产甲烷能力也随之增大;而当初始pH值高于7时,体系的产沼能力却受到了极大的抑制。结合Gompertz模型拟合结果,初始pH值为7为泔脚发酵产氢余物沼气化的最佳初始pH值,其沼气化的延迟时间λ、产甲烷率、生物气中甲烷的最高体积含量分别为:4.02 d,379.28 mL/g VS,82.2%。厌氧消化结束后,除初始pH值为5的以外,厌氧消化余物的pH值在6.8~6.9之间,这为沼气中甲烷的高体积含量(高于常规厌氧消化的最高甲烷体积含量75%)提供了证据。     

木糖高温厌氧发酵产氢的影响因素及两相产氢-产甲烷的能量转化效率

通过批次实验,考查了木糖高温(55℃)厌氧发酵中初始pH(5.0~10.0)和初始底物浓度(2.5~15 g·L~(-1))对产氢效率、液相产物以及木糖降解率的影响;并进行了两相产氢-产甲烷实验,对比单相产甲烷与两相产氢-产甲烷能量转化效率。结果表明:在初始pH=5.0或初始底物浓度为2.5 g·L~(-1)时无氢气产生,最大产氢率1.31 mol H2·(mol木糖)-1在pH=7.0,底物浓度7.5 g·L~(-1)时获得,同时木糖降解率和累积产氢量分别为97.48%和328.4 mL;其主要代谢副产物为丁酸和乙酸,属于丁酸型发酵。厌氧产氢后末端产物甲烷产率为274.9 mL CH_4·(g COD)-1,两相系统能量转化效率达到63.98%,高于单相产甲烷系统的49.39%。     

Inhibition of residual <Emphasis Type="Italic">n</Emphasis>-hexane in anaerobic digestion of lipid-extracted microalgal wastes and microbial community shift

Converting lipid-extracted microalgal wastes to methane (CH₄) via anaerobic digestion (AD) has the potential to make microalgae-based biodiesel platform more sustainable. However, it is apparent that remaining n-hexane (C₆H₁₄) from lipid extraction could inhibit metabolic pathway of methanogens. To test an inhibitory influence of residual n-hexane, this study conducted a series of batch AD by mixing lipid-extracted Chlorella vulgaris with a wide range of n-hexane concentration (～10 g chemical oxygen demand (COD)/L). Experimental results show that the inhibition of n-hexane on CH₄ yield was negligible up to 2 g COD/L and inhibition to methanogenesis became significant when it was higher than 4 g COD/L based on quantitative mass balance. Inhibition threshold was about 4 g COD/L of n-hexane. Analytical result of microbial community profile revealed that dominance of alkane-degrading sulfate-reducing bacteria (SRB) and syntrophic bacteria increased, while that of methanogens sharply dropped as n-hexane concentration increased. These findings offer a useful guideline of threshold n-hexane concentration and microbial community shift for the AD of lipid-extracted microalgal wastes.     

Microwave enhanced advanced oxidation process for treating dairy manure at low pH

This study investigated the treatment of dairy manure using the microwave enhanced advanced oxidation process (MW-AOP) at pH 2. An experimental design was developed based on a statistical program using response surface methodology to explore the effects of temperature, hydrogen peroxide dosage and heating time on sugar production, nutrient release and solids destruction. Temperature, hydrogen peroxide dosage and acid concentration were key factors affecting reducing sugar production. The highest reducing sugar yield of 7.4% was obtained at 160°C, 0 mL, 15 min heating time, and no H₂O₂ addition. Temperature was a dominant factor for an increase of soluble chemical oxygen demand (SCOD) in the treated dairy manure. The important factors for volatile fatty acids (VFA) production were microwave temperature and hydrogen peroxide dosage. Temperature was the most important parameter, and heating time, to a lesser extent affecting orthophosphate release. Heating time, hydrogen peroxide dosage and temperature were significant factors for ammonia release. There was a maximum of 96% and 196% increase in orthophosphate and ammonia concentration, respectively at 160°C, 0.5 mL H₂O₂ and 15 min heating time. The MW-AOP is an effective method in dairy manure treatment for sugar production, nutrient solubilisation, and solids disintegration.     

粉煤灰负载铁离子催化氧化活性黄染料废水

以粉煤灰为载体,制备铁/粉煤灰负载型催化剂,并利用该催化剂催化H2O2氧化降解活性黄染料废水,探讨了H2O2投加量、催化剂投加量、染料初始浓度和初始pH值等因素对染料废水COD去除率和脱色率的影响。结果表明,当染料废水COD初始浓度为200 mg/L,初始pH值为1.7,投加0.5 g/100 mL催化剂及加入1.0 mL浓度为1.13 mol/L的H2O2溶液时,处理效果最好,此时染料废水的COD去除率和脱色率分别达到63%和99%,并且废水的可生化性得到很大的提高。利用该负载催化剂能够有效地减少活性黄染料废水中Fe3+的残留量。     

Treatment of coking wastewater by an advanced Fenton oxidation process using iron powder and hydrogen peroxide

In this study the treatment of coking wastewater was investigated by an advanced Fenton oxidation process using iron powder and hydrogen peroxide. Particular attention was paid to the effect of initial pH, dosage of H₂O₂ and to improvement in biodegradation. The results showed that higher COD and total phenol removal rates were achieved with a decrease in initial pH and an increase in H₂O₂ dosage. At an initial pH of less than 6.5 and H₂O₂ concentration of 0.3 M, COD removal reached 44-50% and approximately 95% of total phenol removal was achieved at a reaction time of 1 h. The oxygen uptake rate of the effluent measured at a reaction time of 1 h increased by approximately 65% compared to that of the raw coking wastewater. This indicated that biodegradation of the coking wastewater was significantly improved. Several organic compounds, including bifuran, quinoline, resorcinol and benzofuranol were removed completely as determined by GC-MS analysis. The advanced Fenton oxidation process is an effective pretreatment method for the removal of organic pollutants from coking wastewater. This process increases biodegradation, and may be combined with a classical biological process to achieve effluent of high quality.     

Harnessing dark fermentative hydrogen from pretreated mixture of food waste and sewage sludge under sequencing batch mode

Food waste and sewage sludge are the most abundant and problematic organic wastes in any society. Mixture of these two wastes may provide appropriate substrate condition for dark fermentative biohydrogen production based on synergistic mutual benefits. This work evaluates continuous hydrogen production from the cosubstrate of food waste and sewage sludge to verify mechanisms of performance improvement in anaerobic sequencing batch reactors. Volatile solid concentration and mixing ratio of food waste and sludge were adjusted to 5 % and 80:20, respectively. Five different hydraulic retention times (HRT) of 36, 42, 48, 72, and 108 h were tested using anaerobic sequencing batch reactors to find out optimal operating condition. Results show that the best performance was achieved at HRT 72 h, where the hydrogen yield, the hydrogen production rate, and hydrogen content were 62.0 mL H₂/g VS, 1.0 L H₂/L/day, and ~50 %, respectively. Sufficient solid retention time (143 h) and proper loading rate (8.2 g COD/L/day as carbohydrate) at HRT 72h led to the enhanced performance with better hydrogen production showing appropriate n-butyrate/acetate (B/A) ratio of 2.6. Analytical result of terminal-restriction fragment length polymorphism revealed that specific peaks associated with Clostridium sp. and Bacillus sp. were strongly related to enhanced hydrogen production from the cosubstrate of food waste and sewage sludge.     

Kinetics study of fermentative hydrogen production from liquid swine manure supplemented with glucose under controlled pH

Kinetics of H₂ production from liquid swine manure supplemented with glucose by mixed anaerobic cultures was investigated using batch experiments under four different pH conditions (4.4, 5.0, 5.6, and uncontrolled). The temperature for the experiments was controlled at 37 ± 1°C and the length of experiments varied between 50 and 120 hours, depending upon the time needed for completion of each individual experiment. The modified Gompertz model was evaluated for its suitability for describing the H₂ production potential, H₂ production rate, and substrate consumption rate for all the experiments. The results showed that the Gompertz model could adequately fit the experimental results. The effect of pH was significant on all kinetic parameters for H₂ production including yield, production rate and lag time, and the substrate utilization rate. The optimal pH was found to be 5.0, at which a maximum H₂ production rate (0.64 L H₂/h) was obtained, and deviation from the optimal pH could result in substantial reductions in H₂ production rate (0.32 L H₂/h for pH 4.0 and 0.43 L H₂/h for pH 5.6). The results also showed that if pH was not controlled for the batch fermentation process, the substrate utilization efficiency could steeply decrease from 98.8% to 33.7%.     

Reusing colored industrial wastewaters in a photofermentation for enhancing biohydrogen production by using ultrasound stimulated <Emphasis Type="Italic">Rhodobacter sphaeroides</Emphasis>

One-time ultrasonication pre-treatment of Rhodobacter sphaeroides was evaluated for improving biohydrogen production via photofermentation. Batch experiments were performed by varying ultrasonication amplitude (15, 30, and 45%) and duration (5, 10, and 15 min) using combined effluents from palm oil as well as pulp and paper mill as a single substrate. Experimental data showed that ultrasonication at amplitude 30% for 10 min (256.33 J/mL) achieved the highest biohydrogen yield of 9.982 mL H₂/mL_medium with 5.125% of light efficiency. A maximum COD_total removal of 44.7% was also obtained. However, when higher ultrasonication energy inputs (>256.33 J/mL) were transmitted to the cells, biohydrogen production did not improve further. In fact, 20.6% decrease of biohydrogen yield (as compared to the highest biohydrogen yield) was observed using the most intense ultrasonicated inoculum (472.59 J/mL). Field emission scanning electron microscope images revealed the occurrence of cell damages and biomass losses if ultrasonication at 472.59 J/mL was used. The present results suggested that moderate ultrasonication pre-treatment was an effective technique to improve biohydrogen production performances of R. sphaeroides.     

Fenton氧化法深度处理抗生素废水二级出水

采用Fenton氧化法对青霉素和土霉素混合废水二级处理出水进行深度处理,通过正交和单因素实验研究了废水初始反应pH值、H2O2投加量、Fe2+/H2O2摩尔比及反应时间等因素对废水处理效果的影响。实验结果表明,Fenton氧化法处理的最佳反应条件为:初始pH值4、H2O2(30%)投加量50 mL/L、Fe2+/H2O2摩尔比1/20和反应时间60 min,处理后出水COD小于120 mg/L,COD去除率在75%以上,急性毒性(HgCl2毒性当量)小于0.07 mg/L,满足《发酵类制药工业水污染物排放标准》(GB21903-2008)表2标准要求。     

Study on substrate metabolism process of saline waste sludge and its biological hydrogen production potential

With the increasing of high saline waste sludge production, the treatment and utilization of saline waste sludge attracted more and more attention. In this study, the biological hydrogen production from saline waste sludge after heating pretreatment was studied. The substrate metabolism process at different salinity condition was analyzed by the changes of soluble chemical oxygen demand (SCOD), carbohydrate and protein in extracellular polymeric substances (EPS), and dissolved organic matters (DOM). The excitation-emission matrix (EEM) with fluorescence regional integration (FRI) was also used to investigate the effect of salinity on EPS and DOM composition during hydrogen fermentation. The highest hydrogen yield of 23.6 mL H₂/g VSS and hydrogen content of 77.6% were obtained at 0.0% salinity condition. The salinity could influence the hydrogen production and substrate metabolism of waste sludge.

     

Hydrogen Sulfide Gas Treatment by a Chemical‐Biological Process: Chemical Absorption and Biological Oxidation Steps

In order to remove high concentrations of hydrogen sulfide (H₂S) gas from anaerobic wastewater treatments in livestock farming, a novel process was evaluated for H₂S gas abatement involving the combination of chemical absorption and biological oxidation processes. In this study, the extensive experiments evaluating the removal efficiency, capacity, and removal characteristics of H₂S gas by the chemical absorption reactor were conducted in a continuous operation. In addition, the effects of initial Fe^2 + concentrations, pH, and glucose concentrations on Fe^2 + oxidation by Thiobacillus ferrooxidans CP9 were also examined. The results showed that the chemical process exhibited high removal efficiencies with H₂S concentrations up to 300 ppm, and nearly no acclimation time was required. The limitation of mass‐transfer was verified as the rate‐determining step in the chemical reaction through model validation. The Fe^2 + production rate was clearly affected by the inlet gas concentration as well as flow rate and a prediction equation of ferrous production was established. The optimal operating conditions for the biological oxidation process were below pH 2.3 and 35°C in which more than 90% Fe^3 + formation ratio was achieved. Interestingly, the optimal glucose concentration in the medium was 0.1%, which favored Fe^2 + oxidation and the growth of T. ferrooxidans CP9.