Anaerobic treatment of wastewater containing fatty acids in upflow reactors

An extended summary is presented of a Dr.Sc. Thesis in which the results of a study on anaerobic treatment of wastewater containing fatty acids have been reported. This study, concerning the technological features of this process in upflow reactors, was aimed at the following subjects :

• - the dynamics of the fluid flow in the reactor;

• - the dynamic behaviour of the sludge particles in the reactor;

• - the kinetics of the conversion of the fatty acids and of the formation of the products (mainly biogas and anaerobic sludge); and

• - the separation of the gas and the sludge from the treated water.

From the results obtained in experiments on lab-scale and (semi) technical scale, a quantitative model for the operation of the reactor has been derived. This model can be used for scaling-up purposes and for optimisation of the process performance.     

Modeling of the upflow anaerobic sludge bed-filter system: a case with hysteresis

A hybrid upflow sludge bed-filter (UBF) anaerobic reactor was successfully used for treatment of synthetic soluble 1% sugar waste. An hysteresis phenomenon was observed and discussed with respect to changes in acidogenic/acetoclastic specific activities ratio. The Haldane equation was adapted for predicting performance inhibition by undissociated acids as a function of substrate-COD and pH. The Monod and adapted Haldane models were solved simultaneously with substrate mass balance for a UBF reactor. The soluble COD removal efficiency and methane productivity were predicted as a function of the dilution rate. Critical values of solid and hydraulic residence times were also estimated and discussed in detail.     

Effect of settling on performance of the upflow anaerobic sludge bed reactors

The effects of settler volume on the start-up and steady-state performance of 41. laboratory upflow sludge bed reactors treating bean blanching waste of 10,000 mg COD l⁻¹ were determined. The rate of start-up, as well as the maximum loading rate, increased with increased settler volume and performance. A loading rate of 30 kg COD m⁻³ day⁻¹ (based on reactor volume alone) and a COD removal of 95% was obtained with a 21. settling flask and a 4 to 1 recirculation rate. Without a settler, the maximum loading rate was 10 kg COD m⁻³ day⁻¹. The sludge was flocculent rather than granular. Sludge profiles and characteristics in the reactors and settlers were determined.     

Effects of increase modes of shear force on granule disruption in upflow anaerobic reactors

Sludge washout is listed among the top practical problems of the high rate upflow anaerobic reactors. This study investigated quantitatively two sludge washout processes operated under different hydrodynamic shear increase modes with the intervals of 1 and 10 days respectively. The results reveal that the sludge washout accompanying with large-scale granule disruption could lead to performance failure with heavy sludge loss ratio of about 46.1% at sludge loss rate about 0.35 gVSS L⁻¹ d⁻¹ during the process with shear increase interval of 1 day, while the highest sludge loss rate was only 0.12 gVSS L⁻¹ d⁻¹ during the process with 10-day interval. The intensified shear conditions could weaken the granules through inhibiting the extracellular polymers production and bioactivity. As consequences, an outbreak of large-scale granule disruption would raise and then significantly accelerate the sludge washout. Since long interval could provide the granules the opportunity to recover from these negative effects to some extent, the shear increase strategy of long interval over 10 days is favorably recommended to operate full-scale reactors during the start-up and shock load periods. The pioneer use of the micro particle image velocimetry in this study offers the possibility to discover the real hydrodynamic conditions around granules at microscale for the first time and reveals that the shear force exerts directly on the granular surface as a mechanical disruption force and big granules undergo high disruption force. The granule disruption is a result of the competition between the granule and the ambient hydrodynamic shear conditions rather than a process with shear force as a sole dominant factor. These could facilitate the understanding of the complicated interactions between the hydrodynamics and reactor performance and favor then a better control of the full-scale reactors.     

Rheological and fractal characteristics of granular sludge in an upflow anaerobic reactor

The rheological and fractal characteristics of the granular sludge in an upflow anaerobic sludge blanket (UASB) reactor were investigated in this study. The influences of sludge concentration and temperature on the rheological properties of the granular sludge were evaluated, and the Bingham model was adopted to describe its rheology. In addition, image analysis was used to determine the sludge fractal dimension. The results indicate that the UASB granular sludge showed a shear-thinning behavior. The relationships between the limiting viscosity and the sludge concentration, as well as the limiting viscosity and temperature could be respectively modeled using an exponential equation and Arrhenius equation well. The Bingham model was able to adequately describe the rheology of the granular sludge. The fractal dimension of the granular sludge, 2.79+/-0.03, was larger than that of some other aggregates, suggesting that the granular sludge were more compact and denser. Furthermore, the relationship between rheological and fractal properties of the granular sludge could be properly described with the model proposed by Shih et al. [1990. Scaling behavior of the elastic properties of colloidal. Phys. Rev. A 42, 4772-4779].     

Bacterial populations and their roles in a pharmaceutical-waste anaerobic filter

The bacterial populations, their roles and distribution in an anaerobic filter treating a simulated pharmaceutical effluent containing a branched-chain fatty acid (BCFA) were studied. The BCFA degradation pathway and mechanisms were also investigated. The biofilm from the filter was enriched in serum bottle cultures using different BCFAs and fatty acids as the sole carbon source. The anaerobic biofilm was a consortium of (1) BCFA-degrading Syntrophomonas spp. which produced ethanoic acid and H₂, (2) H₂-utilizing Methanococcus spp. and (3) ethanoate-utilizing Methanothrix spp. Beta-oxidation was proposed as the acidogenic mechanism. The bacterial consortium could degrade BCFAs with tertiary carbon but not those with quaternary carbon. Branching at the alpha or beta position along the carbon chain interfered with the beta-oxidation mechanisms. Bacterial distribution in the filter was uneven, which was attributed to incomplete mixing.     

Accelerated start-up and enhanced granulation in upflow anaerobic sludge blanket reactors

In the present study, the effects of a cationic polymer on reactor start-up and granule development were evaluated. A control reactor R1 was operated without adding polymer, while the other five reactors designated R2, R3, R4, R5 and R6 were operated with different polymer concentrations of 20, 40, 80, 160 and 320 mg/L, respectively. Experimental results demonstrated that adding the polymer at a concentration of 80 mg/L markedly accelerated the start-up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4 g COD/L.d was reduced by approximately 50% in R4 as compared with the control reactor. The same reactor with 80 mg/L polymer was able to achieve an OLR of 12 g COD/L.d after 59 days of operation, while R1, R2, R3, R5 and R6 achieved the same loading rate at much longer period of 104, 80, 69, 63 and 69 days, respectively. Comparing with the control reactor, the start-up time of R4 was shortened markedly by about 43% at this OLR, while other reactors also recorded varying degree of shortening. Monitoring on granule development showed that the granule formation was accelerated by 30% from the use of the appropriate dosage of polymer. Subsequent granules characterization indicated that the granules developed in R4 with 80 mg/L polymer exhibited the best settleability, strength and methanogenic activity at all OLRs. The organic loading capacities of reactors were also increased by the polymer addition. The maximum organic loading of the control reactor was 24 g COD/L.d, while the polymer-assisted reactor added with 80 mg/L polymer attained a markedly increased organic loading of 40 g COD/L.d. The laboratory results obtained demonstrated that adding the cationic polymer could result in shortening of start-up time and enhancement of granulation, which in turn lead to improvement in organics removal efficiency and loading capacity of the UASB system.     

物料比对污泥与餐厨废弃物协同厌氧消化的影响

依托市政污泥与餐厨废弃物协同处理工程,考察了物料比对市政污泥与餐厨废弃物协同厌氧消化效果的影响。结果表明,在不同物料比下,厌氧消化液的酸碱比(VFA/ALK)保持在0. 10~0. 12,挥发性脂肪酸(VFA)维持在1 093~1 529 mg/L,碱度(ALK)维持在10 321~13 688mg/L,厌氧消化系统处于稳定状态;随着餐厨废弃物比例的增加,VS降解率和VS添加产气率呈增加趋势,当污泥与餐厨废弃物的比例为1∶2时,两者协同厌氧消化效果最好,此时VS降解率达到79. 4%,VS添加产气率为0. 56 m^3/(kgVS·d),沼气中的甲烷含量达到61. 4%,H2S产量为77. 4mg/m^3;污泥与餐厨废弃物的协同处理有利于减少沼气中的H2S含量。     

现代商品混凝土配合比优化设计的探索与实践

结合节能减排和提高混凝土性能的要求,采用3因素、3水平L9(34)排列方法对掺矿粉、粉煤灰等多组分材料混凝土配合比的试配进行优化设计,从试验结果中比选出既能满足施工要求,又能满足强度等级要求的最优配比作为混凝土理论配合比。该优化设计方法对提高混凝土性能,保证混凝土质量确有显著的效果。     

PEO与粉煤灰组合对厌氧污泥颗粒化影响

以聚氧化乙烯（PEO）为筛选物,结合粉煤灰的吸附特性,就絮凝剂与粉煤灰组合后对厌氧污泥颗粒化的影响进行了研究,通过研究确定了聚氧化乙烯与粉煤灰的最佳组合。     

多层砌体结构抗震性能影响因素分析及应用

分析了多层砌体结构房屋抗震性能影响因素,从设计、施工以及管理三个方面进行了阐述,强调在重视砌体结构验算和构造措施的基础上,突出概念设计对多层砌体结构房屋抗震的重要性,并进行了较为详细的分析。同时,强调了施工阶段操作过程以及管理的重要性,并阐述了房屋使用阶段日常管理的必要性。     

Acidogenesis of gelatin-rich wastewater in an upflow anaerobic reactor: influence of pH and temperature

The influence of temperature and pH on the acidification of a synthetic gelatin based wastewater was investigated using an upflow anaerobic reactor. Gelatin degradation efficiency and rate, degree of acidification, and formation rate of volatile fatty acids and alcohols all slightly increased with temperature. Temperature affected the acidogenesis of gelatin according to the Arrhenius equation with an activation energy of 1.83 kcal/mol. Compared with temperature, pH had a more significant effect on the acidogenesis. Gelatin degradation efficiency substantially increased with pH, from 60.0% at pH 4.0 to 97.5% at pH 7.0. The degree of acidification increased from 32.0% at pH 4.0 to 71.6% at pH 6.5, but dropped to 66.8% when pH increased to 7.0. The optimum pH for the overall acidogenic activity was found to be 6.0, close to 5.9, the optimum pH calculated using a semi-empirical model. Operation at pH of 4.0-5.0 favored the production of propionate, hydrogen, whereas the operation at pH 6.0-7.0 encouraged the production of acetate, butyrate, and i-butyrate. The region between pH 5.0 and 6.0 was the transition zone.     

粉煤灰效应及其对混凝土性能的影响

研究了粉煤灰的形成、资源特性及粉煤灰的效应。探讨了粉煤灰对新拌混凝土和硬化混凝土在和易性、强度、抗冻性、抗渗性及抗碳化等方面的影响 ,提出粉煤灰在混凝土的应用中具有其它材料无法替代的技术优势     

Long-term performance analysis of chemical filters in clean rooms based on a prediction model

Chemical filters are the most important devices for removing gas-phase pollutants in clean rooms. However, the testing concentration of chemical filters is too high for reflecting their performance in a real clean room environment. This study tested the adsorption performance of chemical filters in the two most commonly used shapes at different concentrations. Then, the Langmuir equation and Wheeler-Jonas kinetic equation were combined to establish an adsorption performance prediction model of chemical filters under actual conditions. The predicted values of the model were in good agreement with the experimental results, which indicated the high accuracy of the prediction model. The model does not need to test the microscopic parameters of the adsorbent and can maintain high accuracy at low concentrations. A fast method for calculating the service life of chemical filters was also presented. Based on this model, the total cost of using a chemical filter with a high carbon content in microelectronic clean rooms could be decreased by 45% due to decreasing the number of filter replacements over 3 months. So a chemical filter with a high carbon content should be preferred over a filter with low resistance in microelectronic clean rooms.     

OMMT掺量对SBS改性沥青路用性能的影响研究

通过一定的剪切工艺,制备出OMMT为不同比例的OMMT/SBS复合改性沥青,对其各项技术性质进行了试验研究。结果表明：OMMT能显著改善SBS改性沥青的高温性能、感温性能、存储性能、老化性能;通过添加OMMT的方法,可以获得性能优良的SBS改性沥青。     

粉煤灰掺入量对植被生态混凝土性能影响的探究

通过改变粉煤灰的掺入量,探究了粉煤灰的掺入量对该植被生态混凝土的抗压强度、抗折强度、孔隙率、透水性系数和pH值的影响,确定了粉煤灰在该植被生态混凝土中的掺入量在20%~40%范围为宜。     

粗集料对混凝土性能的影响及生产中的控制

通过理论分析和试验,讨论了粗集料的含泥量、粒型和颗粒级配等指标对混凝土性能的影响,并对不同使用粗集料的混凝土进行经济成本分析,以实现混凝土配合比的优化,为实际混凝土生产中粗集料的选择和配合比设计提供指导。     

搅拌对给水厂污泥浓缩的影响

通过试验研究了搅拌对给水厂污泥浓缩的影响,并分别探讨了快速搅拌和慢速搅拌对沉降效果的影响,结果表明:适当的慢速搅拌可以在一定程度上提高浓缩效果,建议最佳搅拌的速度梯度为1.4 s-1。     

混凝土叠合板结构性能检验影响因素分析

对混凝土叠合板结构性能检验的发展进行了论述,基于相关标准规范,结合实际工程检验实例,分析了混凝土叠合板结构性能检验的影响因素,指出工程中检验叠合板结构性能存在的不妥之处,具有一定的工程意义。     

高性能混凝土配合比设计的影响因素探析

依据高性能混凝土的定义及特性,介绍了高性能混凝土配合比的设计原则,并对配合比设计中水胶比、浆集比、砂率、减水剂用量等进行了阐述,并给出了其试配和调整方法,以提高高性能混凝土在建筑工程中的应用质量。