Acidogenic fermentation of blended food‐waste in combination with primary sludge for the production of volatile fatty acids

The performance of a laboratory‐scale anaerobic acidogenic fermenter fed with a mixture of blended kitchen food‐waste and primary sludge from a sewage treatment plant was investigated for the production of volatile fatty acids (VFA). The operating variables for acidogenic fermentation were kitchen food‐waste content (10 and 25 wt %), hydraulic retention time (HRT: 1, 3 and 5 days), temperature (ambient: 18 ± 2 °C, and mesophilic: 35 ± 2 °C) and pH (varied from 5.2 to 6.7). The experimental results indicated that effluent VFA concentrations and VFA production rates were higher at ambient temperature than at mesophilic conditions. The net amount of VFA with 10 wt % food‐waste increased up to 920 mg dm^?3 with an increase of HRT, but contrasting results (a decrease of 2610 mg dm^?3) were found due to the conversion of VFA into biogas in the case of 25 wt % food‐waste, which increased significantly at HRT of 3–5 days. In terms of biogas composition (CO₂ and CH₄), the organic matter was converted into CO₂ through the oxidative pathway by facultative species at low temperature while mesophilic temperature and optimum pH (6.3–7.8) played a pivotal role in increasing rate of conversion of VFA into biogas by methanogenesis. Rates of VFA production and their conversion are dependent on the food‐waste content in the mixture. Yet, the higher concentration of food‐waste (25% compared with 10%) did not produce VFA proportionally due to the increased rate of conversion of VFA into gaseous products. The maximum VFA production rate (0.318 g VFA_produced g^?1 VS_fed day^?1) was achieved in the 10 wt % food‐waste at ambient temperature and at a 5‐day HRT. Copyright © 2005 Society of Chemical Industry     

pH值对脱硫废水处理系统污泥性质的影响

在不同pH值工况下，对脱硫废水处理系统产生的污泥特性进行分析，研究了pH值对污泥产量、组成、沉降性能和脱水性能的影响。基于污泥沉降性能和脱水性能优化实验，对华能南通电厂脱硫废水"三联箱"工艺进行调试。结果表明：pH值越高，污泥产量就越高，污泥沉降比也越高。脱水性能的改变是由于污泥中各成分占比发生了改变，脱水性能在pH值为8.5时最优。投加阴离子型聚丙烯酰胺（PAM），能显著改善污泥的沉降和脱水性能。现场"三联箱"工艺运行pH值为8.5，将非离子型PAM更换为阴离子型PAM，泥饼含水率和出水浊度分别降低至25.2%和12.6 NTU。     

好氧颗粒污泥处理印染废水的特性探究

在柱状序批式反应器内调查了好氧颗粒污泥处理印染废水的可行性,并考察进水有机负荷率（OLR）对颗粒污泥形成规律及COD、氨氮的去除影响。结果表明,当进水OLR由1.0 kg/（m³·d）升高至7.0 kg/（m³·d）时,颗粒污泥质量浓度呈现上升趋势。当进水OLR为5.0 kg/（m³·d）时,颗粒污泥系统沉降性最好,污泥沉降指数(SVI₃₀)仅为52.6m L/g。此外,进水OLR影响颗粒污泥粒径分布、胞外聚合物（EPS）含量及组分。当进水OLR为5.0 kg/（m³·d）时,颗粒污泥粒径主要分布于0.9～1.2 mm,且占比38.5%,EPS的含量升高至81.3 mg/g,显著高于其他进水OLR组别。进水OLR变化主要影响EPS内蛋白质（PN）含量变化,而对多糖（PS）含量变化影响较小。进水OLR能影响颗粒污泥处理印染废水中污染物的去除,当进水OLR为5.0 kg/（m³·d）时,COD和氨氮去除率最高,且分别为79.5%和85.6%,而进水OLR对浊度...     

三种方法制备PS用硬酯酸锌的性能比较简

比较了三种不同方法（湿法、干法、压力法）制造的聚苯乙烯（PS）造粒用硬酯酸锌（Znst）的质量指标和应用性能（与乙苯的相容性及在苯乙烯中的沉淀性）,在3种方法制造的ZnSt中,以压力法制造的应用性能最佳.     

Assessment by Microscopy of the Coverage of Sludge Flocs by a Nano‐scale Surface Layer

Flocs are irregularly shaped suspended particles of complex structure and composition that occur naturally in aquatic systems. In water treatment facilities, the settling of flocs is extremely important. Transmission electron microscopy was used to quantify the formation of a nano‐scale surface layer on flocs from two laboratory bioreactors modelling a biological wastewater treatment facility. By comparing different floc populations, we demonstrated that flocs that settled quickly out of wastewater had a significant amount of this layer, whereas those with little nano‐scale surface layer had poor settling properties. This morphological feature of floc ultrastructure may permit engineering manipulations that promote floc settling.     

含盐量对好氧颗粒污泥结构及处理效能的影响

研究了含盐量对好氧颗粒污泥结构的影响.研究发现高含盐量有助于提高颗粒污泥的沉速,减小孔隙率.从而形成更加密实的颗粒结构.对比结果表明,在低含盐量下颗粒污泥容易形成中空结构,这是低含盐量下颗粒污泥孔隙率大的根本原因.但高含盐量下形成的菌胶团颗粒污泥容易被丝状茵颗粒污泥所取代,因此控制丝状茵的过度繁殖是采用好氧颗粒污泥处理高盐度有机废水时需要注意的问题.     

Growth and control of filamentous microbes in activated sludge: an integrated hypothesis

Since its initial development and application, the activated sludge process has undergone a continual evolution aimed at maximizing process efficiency and controlling population selection. Organic loading rate, dissolved oxygen concentration and reactor configuration have been implicated as key process variables affecting sludge settleability, their combined effects determining which microbe or microbes are best able to grow and survive in a given system. Using available pure and mixed culture observations, a conceptual hypothesis centered around three model organisms has been developed to explain the growth and control of filamentous organisms in activated sludge. Organism selection in continuously fed systems has been hypothesized to be dominated by filamentous organisms with high sustainable growth rates at low reactor substrate concentrations/organic loading rates and filaments best able to compete for dissolved oxygen at elevated reactor substrate concentrations/organic loading rates. Intermittently fed systems, on the other hand, enrich for nonfilamentous organisms which both rapidly extract substrate from solution and maintain peak activity during extended periods of endogeneous metabolism. While both types of reactor induced feeding patterns can control filamentous organism growth, intermittently fed systems are capable of operation over a wider range of operating conditions by accentuating differences in organism physiology. Additional selection pressures such as substrate composition, non-ideal reactor hydraulics and time-variable influent waste streams were also discussed in relation to their impact on idealized systems.     

Lecane tenuiseta rotifers improves activated sludge settleability in laboratory scale SBR system at 13°C and 20°C

Two experiments at different temperatures were conducted in five laboratory‐scale bioreactors with enhanced nutrient removal simulating the work of sequencing batch reactors (SBRs). The process was operated in three 8‐hour cycles. The oxygen concentration, pH and temperature were controlled and maintained at 1 mg of O₂/L, 7 and 13°C, respectively, throughout the first two weeks and at 20°C for the next 10 days. The introduction of Lecane tenuiseta improved the settling properties of the activated sludge dominated by Microthrix parvicella at both temperatures tested. L. tenuiseta rotifers led to a reduction in filamentous bacteria abundance and did not negatively affect the chemical parameters of the effluent. For each temperature, there were no differences in COD, N_tot, N‐NH₄ or P‐PO₄ values between the treatment and control bioreactors. The results have shown that the application of L. tenuiseta is a promising biological tool for bulking prevention especially in a cold season.     

Effect of feeding pattern and storage on the sludge settleability under aerobic conditions

The selection of filamentous bacteria is often assumed to be associated with specific microbial properties such as growth rate, substrate uptake rate, substrate affinity and potential for substrate storage. In this study we aimed to verify some of these factors. Sequencing batch reactor (SBR) systems were used to scale-down aerobic activated sludge systems with an aerobic selector. Adding acetate in different aerobic feeding periods allowed us to simulate a variable relative size of aerobic selector with different bulk liquid substrate concentrations. The experiments showed that as expected, the aerobic fill time ratio (FTR(ox)) and the corresponding feast period, which can be assumed similar to contact time in an aerobic selector, had a strong effect on the sludge settleability. Promoting a strong substrate gradient in the SBR (FTR(ox)<5.4%) resulted in good sludge settleability (SVI<120mLg(-1)). Whenever acetate was added in a limiting rate (FTR(ox)>6.2%), a condition in which the acetate concentration in the reactor was always very low, the sludge settleability decreased (SVI>150mLg(-1)). Sludge settleability could be improved by changing the feeding strategy to a pulse feed. The maximum specific acetate uptake rate and poly beta-hydroxybutyrate (PHB) production rate of bad settling sludge, including bulking sludge, was similar to well-settling sludge, which is not in accordance with the general assumptions that well settling sludge have a higher maximal substrate uptake rate and better storage capacities. An alternative hypothesis for the development of filamentous structures in biological flocs has been formulated. It is hypothesized that bulking sludge originates from the presence of substrate gradients in sludge aggregates. Whereas at low bulk liquid substrate concentration filamentous bacteria give easier access to the substrate at the outside of the flocs and thereby proliferate, at high bulk liquid substrate concentration there is no substrate advantage for filamentous organisms and smooth bacterial structures predominate. In this hypothesis there is no need for an intrinsic difference in kinetic parameters between floc and filamentous bacteria. Where presence of filamentous bacteria is related to process conditions, the presence of a specific filament is likely due to presence of a specific limiting substrate.     

含酚废水处理中活性污泥沉降性能影响因素的研究

实验考察了生物降解含酚废水过程中污泥负荷、溶氧、C／N／P质量比、温度4种因素对活性污泥沉降性能的影响，结果表明在低氮、磷营养条件下，由于菌胶团结构中丝状菌对营养物质具有累积的能力，处于生长优势，造成菌胶团结构松散、压实性差，从而导致污泥沉降性能恶化，而在一定范围内污泥负荷、溶氧、温度发生变化，并未影响污泥沉降性能，但在污泥负荷过高，溶氧浓度过低的情况下，细菌生理活性受抑制，出水水质恶化。