PAC投加对絮体破碎后再絮凝特性和颗粒去除的影响

为改善絮体破碎后的再絮凝能力,提高颗粒的去除效率,以西宁地区低温低浊水为研究对象,通过光学检测仪器及数学拟合方式,分析补投聚合氯化铝(PAC)对破碎后絮体粒径与分布、生长速率变化的影响,描述颗粒及浊度的去除效果.结果表明:随PAC补投量的升高,絮体粒径和生长速率均先增大后减小,各自达到峰值所需补投药量分别为4和6 mg/L;剩余浊度和颗粒数先降低后升高,最低时可分别降至0.79 NTU、90个·m L-1.补投2 mg/L药剂后,280~630μm絮体颗粒体积分数由22.85%增大到46.36%,4~35μm絮体颗粒体积分数由1.21%减小至0.19%,再絮凝后絮体平均粒径为400μm,大于未破碎前的370μm,粒径增长率为8.11%,絮体生长速率为77.26μm/min.补投PAC可促进絮体破碎后的再絮凝,提高浊度及颗粒数的去除效果,可有效改善实际工程絮凝工艺效果.     

不同曝气剪切条件下活性污泥絮体特性研究

采用轮流搅拌-曝气SBR系统模拟两种不同曝气方式(分点曝气和分段曝气),研究其形成的污泥絮体特性.结果表明:在相同的运行条件下,分点曝气形成的污泥絮体尺度大、沉降性能好,两者的SVI平均值分别为133mL/g和202mL/g,平均粒径分别为74.26μm和53.46μm,而且分点曝气中拥有更多的大颗粒絮体;分点曝气形成的污泥絮体稳定性优于分段曝气,在连续曝气条件下,两种污泥絮体均受到剪切破碎,不仅初始粒子被剥离,而且絮体也被打碎变小,但分段曝气被破碎的程度更大;分点曝气和分段曝气所形成的污泥絮体的EPS含量分别为31.21mg/gVSS和21.6mg/gVSS,且前者EPS中的多糖、蛋白质和DNA组分均比后者多,两者EPS的主要组分以蛋白质为主.两种污泥经连续曝气3h后,EPS皆增大,且多糖含量增加较多;分点曝气和分段曝气形成的污泥比阻分别为5.21×1012 m/kg和7.94×1012 m/kg,前者污泥的脱水性能较好.经连续曝气3h后,两种污泥的比阻明显增大,脱水性能变差.     

Floc architecture of bioflocculation sediment by ESEM and CLSM

Sediment flocculation is a critical component for the understanding of cohesive sediment dynamics. Traditionally, the referred study has largely been devoted to forming mechanism, influencing factors and physicochemical sediment conditions of all kinds of organic-flocculation and inorganic-flocculation. However, during the last decade, the bioflocculation of sediment by biological activity has been given increasing attention. But most studies have focused on the interrelations between biological and sedimentological variables. With the assistance of a newly developed field kit and correlative microscopy (which includes environmental scanning electron microscopy and confocal laser scanning microscopy), this article begins to bridge the resolution gap between sediment particles and biological activities as well as its metabolic products biofilm, in order to better understand the role of polymeric material biofilm in floc ultrastructure and outward floc behavior of bioflocculation sediment. Results have demonstrated that bioflocculation sediment was observed to be composed of complex networks of biofilm and appeared to be of complicated physical floc structures. The biofilm was found to embed particles and permeate the void space, representing the dominant physical bridging mechanism of the flocs and contributed to the extensive surface area, architecture characteristics, and mechanical properties of bioflocculation sediment.     

ACTIFLO(R)技术用于海水净化处理的问题及解决方案

ACTIFLO(R)微砂加重絮凝斜管高效沉淀技术具有沉淀速度快、处理效果好、耐冲击负荷能力强和占地面积小等特点,目前被广泛应用于淡水净化领域.针对ACTIFLO(R)技术应用于我国东南沿海某电厂海水净化处理中出现的藻类繁殖与附着、斜管局部塌陷和斜管跑砂等问题,在分析问题成因的基础上,提出了相应的解决方案,以期有利于该技术的不断完善.     

Characteristics of fluoride adsorption onto aluminium(III) and iron(III) hydroxide flocs

The fluoride adsorption onto the hydroxide flocs of Al(III), Fe(III), or a mixture of the two was studied. The optimum pH was influenced by the flocs’ solubility and surface charge. Although the Al(III) hydroxide flocs had a maximum adsorption capacity at the equilibrium concentration of 8 mg-F/L, the two-stage adsorption process revealed that the mixture of the Al(III) and Fe(III) hydroxide flocs required the smallest adsorbent dose as the concentration changed from 40 to 8 mg-F/L. Thus, the simultaneous dosing of Al(III) and Fe(III) combined with a two-stage adsorption process appears to be an effective option for fluoride removal.     

Ultrasonic pre‐treatment of biological sludge: consequences for disintegration,anaerobic biodegradability,and filterability

BACKGROUND: Disintegration was developed as a pretreatment process for sludge to accelerate the digestion processes. Ultrasonic treatment may be a good alternative for sludge disintegration. In this study, different specific energy inputs ranged between 0 and 15 880 kJ kg^?1 and very low ultrasonic densities ranged between 0.04 and 0.1 W mL^?1 were applied to biological sludge for disintegration purposes. The potential for improving anaerobic digestion through ultrasonic pre‐treatment and the effect of ultrasonic pre‐treatment on the filterability characteristics of sludge were also investigated. RESULTS: 9690 kJ kg^?1 TS of supplied energy and very low power density of 0.09 Wm L^?1 are efficient for floc disintegration. For 9690 kJ kg^?1 TS, 44% higher methane production was achieved than with raw sludge as a result of biochemical methane potential assay. The supernatant characteristics of the sludge were also affected by the ultrasonic pre‐treatment. For 9690 kJ kg^?1 TS, the soluble chemical oxygen demand (SCOD), dissolved organic carbon (DOC), total nitrogen (TN), and total phosphorus (TP) in the sludge supernatant increased by 340%, 860%, 716%, and 207.5%, respectively. CONCLUSION: Ultrasonic pre‐treatment is an effective method for biological sludge disintegration even at very low ultrasonic density levels. It leads to increased anaerobic biodegradability but deteriorates the filterability characteristics of biological sludge. Copyright © 2009 Society of Chemical Industry     

Stroboscopic determination of settling velocity, size and porosity of activated sludge flocs

A multi-exposure photographic method was developed for the combined measurement of the settling velocity and size of activated sludge flocs. The proposed method mainly differs from the previous stroboscopic tests by introducing a new experimental arrangement which ensures sharp images of flocs on photographs.The relationships between individual floc-settling velocity and the floc size were found to be linear or fractional power functions. All these relationships were well correlated.Based on a simplified floc structure assumption and results of experimental measurements of floc-settling velocity and size, the floc porosity was determined. The porosity increased at two distinct rates as the floc size increased.     

Characterization of activated sludge exocellular polymers using several cation-associated extraction methods

Evaluation of prior research and preliminary investigations in our laboratory led to the development of an extraction strategy that can be used to target different cations in activated sludge floc and extract their associated extracellular polymeric substances (EPS). The methods we used were the cation exchange resin (CER) procedure, base extraction, and sulfide addition to extract EPS linked with divalent cations, Al, and Fe, respectively. A comparison of sludge cations before and after CER extraction revealed that most of Ca(2+) and Mg(2+) were removed while Fe and Al remained intact, suggesting that this method is highly selective for Ca(2+) and Mg(2+)-bound EPS. The correlation between sludge Fe and sulfide-extracted EPS was indicative of selectivity of this method for Fe-bound EPS. The base extraction was less specific than the other methods but it was the method releasing the largest amount of Al into the extract, indicating that the method extracted Al-bound EPS. Concomitantly, the composition of extracted EPS and the amino acid composition differed for the three methods, indicating that EPS associated with different metals were not the same. The change in EPS following anaerobic and aerobic digestion was also characterized by the three extraction methods. CER-extracted EPS were reduced after aerobic digestion while they changed little by anaerobic digestion. On the other hand, anaerobic digestion was associated with the decrease in sulfide-extracted EPS. These results suggest that different types of cation-EPS binding mechanisms exist in activated sludge and that each cation-associated EPS fraction imparts unique digestion characteristics to activated sludge.     

三维分形絮团沉降的格子Boltzmann模拟

黏性泥沙絮团的形成机理和沉降特性对河口海岸细颗粒泥沙运动规律研究具有重要作用。为了从微观结构出发研究絮团运动机理，由扩散受限絮凝体聚集模型生成不同大小的分形絮团，引入格子Boltzmann方法模拟三维分形絮团的静水沉降，获得了絮团沉速的变化过程。比较格子Boltzmann算法模拟结果与采用盒子计数分维数的 Winterwerp絮团沉速公式，发现二者有较好的一致性，表明格子Boltzmann模拟方法可应用于河口海岸环境中的黏性泥沙运动研究。