Strategy for minimization of excess sludge production from the activated sludge process

Increased attention has been given to minimization of sludge production from activated sludge process since environmental regulations are being more and more stringent in relation to excess sludge disposal. In a biological process, the more organic carbon utilized in carbon dioxide production, the fewer sludge produced, and vice versa. This paper, therefore, reviews strategies developed for minimization of excess sludge production, such as oxic-settling-anaerobic process, high dissolved oxygen process, uncoupler-containing activated sludge process, ozonation-combined activated sludge process, control of sludge retention time and biodegradation of sludge in membrane-assisted reactor. In these modified activated sludge processes, excess sludge production can be reduced by 20-100% without significant effect on process efficiency and stability. It is expected that this paper would be helpful for researchers and engineers to develop novel and efficient operation strategy to minimize sludge production from biological systems.     

厌氧消化污泥微生物组研究方法及应用

污泥厌氧消化是在消化污泥微生物组的协调下将剩余污泥中有机物转化为甲烷的微生物过程。与传统厌氧消化过程不同,污泥厌氧消化系统的进料底物为含有大量微生物细胞及胞外多聚物等复杂大分子有机物的剩余污泥。因此,厌氧消化污泥微生物组的种群组成、功能及种群间互作关系等异常复杂,使厌氧消化污泥微生物组分析成为难点问题。但近年来高通量测序技术及生物信息学分析方法的快速发展为消化污泥微生物组研究提供了契机,并迅速推动了该研究领域的发展。本文从4个方面梳理、总结厌氧消化污泥微生物组的研究及应用现状:剩余活性污泥结构、组成及其厌氧消化;基于16SrRNA基因序列测序的微生物组研究;基于宏基因组及宏转录组分析的微生物组研究;厌氧消化污泥微生物组研究案例分析。最后我们提出了厌氧消化污泥微生物组研究亟待解决的关键科学问题。     

The phosphorus fractions and alkaline phosphatase activities in sludge

The alkaline phosphatase activities (APA) and phosphorus fractions in activated sludge during wastewater treatment were studied. Our results showed that the phosphorus concentration and fractions in activated sludge were highly correlated with the characteristics of influents. Inorganic phosphorus (IP) and non-apatite inorganic phosphorus (NAIP) were the main phosphorus fractions of sludge. A larger phosphorus concentration was found in activated sludge due to the more readily mobilizable and bio-available forms. The APA in sludge was directly correlated with mixed liquor suspended solids (MLSS) in activated sludge. The APA in the sludge is implicated the depletion of organic phosphorus forms in sludge, whilst also implying its less inhibition of inorganic phosphorus in sludge. The APA and phosphorus fractions in different sludge samples from the same wastewater treatment plant were quite stable. This stability shows their tight interactions in sludge.     

Survival of enteroviruses and coliform bacteria in a sludge lagoon.

Enteroviruses associate with aerobically and anaerobically digested sludge were determined before the addition of the sludge to a sludge lagoon. The fate of sludge-associated viruses was followed during detention of sludge in the lagoon and after application of sludge to land for disposal. While digested sludge was being added to the lagoon, enteroviruses were readily detected in grab samples of sludge from the lagoon. Sludge-associated viruses dropped to low or undetectable levels after disposal of sludge on land and during periods when addition of digested sludge to the lagoon was suspended. Changes in the levels of fecal coliforms in the lagooned sludge paralleled changes in the numbers of enteroviruses. Enteroviruses were not detected in water from deep wells located on the sludge disposal site or near the lagoon. During the initial part of the study, poliovirus serotypes accounted for greater than 90% of the viruses identified. Later, poliovirus serotypes comprised less than 40% of the virus isolates, and echoviruses and Coxsackieviruses were the most common enteroviruses identified.     

论城市污泥农用资源化与可持续发展

根据可持续发展观的基本思想，在对城市污泥的特征、处理现状及其对农业和城市发展的影响进行分析的基础上，认为城市污泥的农用资源化对于城市和农业的可持续发展具有重要意义和紧迫性，也是未来城市污泥处置的根本出路，关键在于控制污泥中毒性污染物的含量，科学合理地施用。     

Kinetics of lactate,acetate and propionate in unadapted and lactate-adapted thermophilic,anaerobic sewage sludge: the influence of sludge adaptation for start-up of thermophilic UASB-reactors

Summary A thermophilic anaerobic sludge digestor was adapted to lactate metabolism. The adapted sludge showed an improved capacity for lactate degradation when tested by a batch activity test, compared to the performance of unadapted sludge. Acetate was the major intermediate produced during the degradation. When adapted sludge was used as the inoculum for a lactate-fed, upflow anaerobic sludge blanket (UASB) reactor, the chemical oxygen demand reduction rate was higher than with unadapted sludge. After 39 days, however, the difference vanished due to an extensive wash-out of sludge from the reactor inoculated with adapted sludge.Offprint requests to: B. K. Ahring     

Development of a test method to assess the sludge reduction potential of aquatic organisms in activated sludge.

This article shows the development of a quantitative sludge reduction test method, which uses the sludge consuming aquatic worm Lumbriculus variegatus (Oligochaeta, Lumbriculidae). Essential for the test are sufficient oxygen supply and the presence of a non-stirred layer of sludge for burrowing of the organisms. The test eliminates the unwanted effects of the organisms' movements, so-called bioturbation, on oxygen transport and (therefore) on sludge reduction. We used fresh untreated activated sludge grown on sewage, in order to stay close to the daily practice of sludge treatment. By separating sludge and worms, sludge reduction and worm growth are quantified independently and accurately. Predation by L. variegatus approximately doubles the decay rate of activated sludge. A minimum ratio of initial worm to sludge biomass (W(0)/S(0)) of about 0.4g worm/g sludge dry mass is required. Under the test conditions 20-40% of the predated sludge is converted into worm biomass. Our test is simple, reproducible and accurate and is done with equipment generally available in any laboratory, yielding results within a few days. The test can also be used to assess the application of mixtures of different aquatic organisms, but does not provide enough information for the design of a sludge treatment reactor.     

Heat inactivation of poliovirus in wastewater sludge.

The effect of raw and anaerobically digested sludge on heat inactivation of poliovirus was investigated. Raw sludge was found to be very protective of poliovirus plaque-forming ability at all temperatures studied, but digested sludge had variable effects that were highly dependent upon the experimental conditions. In low concentrations and at relatively low inactivation temperatures, digested sludge is nearly as protective of poliovirus as raw sludge. However, at higher tempeatures and concentrations, digested sludge caused a significant acceleration of poliovirus inactivation. The difference between the protective capability of raw and digested sludge is not due to loss of protective material, because this component is present in the solids of digested sludge as well as in those of raw sludge. Instead, the difference is due to a virucidal agent acquired during digestion. Addition of this agent to the solids of either raw or digested sludge reverses the protective potential of these solids during heat treatment of poliovirus.     

Heat inactivation of poliovirus in wastewater sludge.

The effect of raw and anaerobically digested sludge on heat inactivation of poliovirus was investigated. Raw sludge was found to be very protective of poliovirus plaque-forming ability at all temperatures studied, but digested sludge had variable effects that were highly dependent upon the experimental conditions. In low concentrations and at relatively low inactivation temperatures, digested sludge is nearly as protective of poliovirus as raw sludge. However, at higher tempeatures and concentrations, digested sludge caused a significant acceleration of poliovirus inactivation. The difference between the protective capability of raw and digested sludge is not due to loss of protective material, because this component is present in the solids of digested sludge as well as in those of raw sludge. Instead, the difference is due to a virucidal agent acquired during digestion. Addition of this agent to the solids of either raw or digested sludge reverses the protective potential of these solids during heat treatment of poliovirus.     

城市污泥土地利用研究

通过培养试验、盆栽试验和田间试验系统地研究了污泥的组分特征、性质及其农地和城市园林绿化地利用对作物或绿化灌木、土壤肥力及其环境的影响,结果表明,污泥富含有机质和氮磷养分,且养分当季有效性介于化肥农家肥之间。施用污泥将明显提高土壤肥力,表现改善土壤物理性质;增加土壤肥机质和氮磷水平,并增加土壤生物活性,因此施用污泥的处理作物产量较高,并有利于后茬作物的稳健生长。但污泥施用也存在重金属、病原物等污染     

Effect of ultrasonic waves on the rheological features of secondary sludge

The increasing production of sewage sludge is a problem for wastewater treatment plants today. Research has sought to improve sludge processing efficiency and minimization. This study examined the changes in the rheological features of secondary sludge as a function of ultrasonic specific energy. It has been analyzed the dependency of steady state viscosity on shear rate and the hysteresis area. Steady state viscosity and the hysteresis area decreased significantly with increased ultrasonic specific energy. This may be due to the disruption of sludge flocks leading to a less rigid internal structure. The centrifugation of ultrasonicated sludge increased the total solid content by approximately 21%, leading to dewatered sludge. This sludge showed less elasticity, viscosity and thixotropy than untreated sludge.     

Influences of Extracellular Polymeric Substances on the Dewaterability of Sewage Sludge during Bioleaching

Extracellular polymeric substances (EPS) play important roles in regulating the dewaterability of sludge. This study sought to elucidate the influence of EPS on the dewaterability of sludge during bioleaching process. Results showed that, in bioleaching system with the co-inoculation of Acidithiobacillus thiooxidans TS6 and Acidithiobacillus ferrooxidans LX5 (A. t+A. f system), the capillary suction time (CST) of sludge reduced from 255.9 s to 25.45 s within 48 h, which was obviously better than the controls. The correlation analysis between sludge CST and sludge EPS revealed that the sludge EPS significantly impacted the dewaterability of sludge. Sludge CST had correlation with protein content in slime and both protein and polysaccharide contents in TB-EPS and Slime+LB+TB layers, and the decrease of protein content in slime and decreases of both protein and polysaccharide contents in TB-EPS and Slime+LB+TB layers improved sludge dewaterability during sludge bioleaching process. Moreover, the low sludge pH (2.92) and the increasing distribution of Fe in the solid phase were another two factors responsible for the improvement of sludge dewaterability during bioleaching. This study suggested that during sludge bioleaching the growth of Acidithiobacillus species resulted in the decrease of sludge pH, the increasing distribution of Fe in the solid phase, and the decrease of EPS content (mainly including protein and/or polysaccharide) in the slime, TB-EPS, and Slime+LB+TB layers, all of which are helpful for sludge dewaterability enhancement.     

嗜热微生物及其降解剩余污泥的机理

活性污泥法已经被广泛应用于污水处理中.剩余污泥是此过程的副产物,其处理费用约占污水处理系统总成本的25%～60%,处理不当则会带来严重的二次污染,成为目前污泥处理研究的难点之一.利用嗜热微生物降解污泥操作方便、经济性较好且易于管理,具有良好的应用前景.本文对污泥降解中的嗜热微生物、嗜热微生物污泥降解机理以及污泥降解过程中起重要作用的嗜热蛋白酶和脂肪酶的最新研究进展进行综述,归纳总结了影响嗜热微生物降解污泥的主要影响因素,并对嗜热微生物在污泥消化方面的应用研究进行展望.     

Preserving sludge from meat industry waste waters through lactic fermentation

This article presents the results of research on preserving sludge from meat industry waste waters. The sludge precipitated by chemical purification of effluents contains considerable amounts of proteins and fats which under certain conditions can be used for feeding to animals. The preservation of sludge was based on lactic fermentation conducted with the use of Lactobacillus delbrückii. Molasses, as the source of sugars which are necessary in the process of silage, were added to the sludge. Basic conditions for preserving sludge through this method, such as addition of molasses, sludge moisture and fat content, were established. The results of the research imply that silage of sludge from the meat industry effluents can be a good way of preserving sludge and converting it into a fodder.     

Psychrophilic methane fermentation of excess sludge by enrichment culture

This study was carried out to determine the possibility of the psychrophilic methane fermentation of the excess sludge produced from fish-processing wastewater treatment. Three different kinds of seed sludge, named M seed sludge, K seed sludge and KL seed sludge were used for batch methane fermentation in Erlenmeyer flasks. M seed sludge was mesophilic, while the other two were prepared in our laboratory by soil collection to obtain a psychrophilic biological community. The effects of temperature on the total volume of biogas generated and on the rate of biogas generation were examined. The activity of K seen sludge with respect to gas yield at 15°C was found to be 1.6-fold higher than that of M seed sludge. Enrichment techniques were then used to accumulate psychrophilic bacteria in KL seed sludge, and the activity at 15°C increased by about two times due to these techniques. Comparison of the three kinds of seed sludge indicates that methane fermentation at low temperature may be feasible, and therefore further study to isolate the psychrophilic bacteria in anaerobic digestion is needed.     

高活性厌氧颗粒污泥稳定性及基质代谢和种间氢转移的研究

选择了几种废水形成的厌氧污泥,进行了稳定性、基质代谢及种间氢转移的研究.颗粒化的污泥对盐、pH、酶作用、温度、压力等外界条件影响有一定的抗性,在丙酸代谢中,丙酸对颗粒污泥抑制浓度可达1000mg/L,而絮状污泥在500mg/L就被明显抑制,并比较了两者的最大比产甲烷速率和氢酶活性,在种间氢转移实验中,乙醇对颗粒污泥的抑制浓度比絮状污泥要高,颗粒污泥在各方面的性能都明显优于絮状污泥,还对颗粒污泥的物理特性及保存方式进行了初步研究.     

Simultaneous methanogenesis and phototrophic bacterial growth in relatively dry sewage sludge under light

Anaerobically digested sewage sludge with a variety of moisture content, namely 81%, 86%, 90% and 98%, were anaerobically cultured at 35 degrees C under light. Phototrophic bacteria grew in the 86% moisture sludge (bacteriochlorophyll a, 0.46 g/L), 90% sludge (bacteriochlorophyll a, 0.36 g/L) and 98% sludge (bacteriochlorophyll a, 0.04 g/L) with methane production. Phototrophic bacteria could not grow in the 81% moisture sludge (bacteriochlorophyll a 0.004 g/L). Phototrophic bacteria could assimilate about 46% of the extracellular ammonium in the 90% moisture sludge. Phototrophic bacteria utilized organic compounds competing with methanogens; therefore, methane yield from the 90% moisture sludge under the light conditions was lower than that under the dark conditions. Phototrophic bacteria could grow in anaerobically digested sludge with relatively low moisture content, and assimilated extracellular ammonium in the sludge. The quality of digested sludge with phototrophic bacterial biomass for fertilizer could be improved compared with that without phototrophic bacterial biomass.     

构树的污泥适应性及养分和重金属吸收累积特征

构树是我国重要速生经济树种,具有适应性强、生物量大和重金属富集能力强等优点,而污泥中含有大量养分和重金属,在污泥中种植构树有望同时实现污泥生态修复和构树资源生产。本研究通过盆栽试验,分析在对照(赤红壤)、50%污泥(污泥、赤红壤混合基质,重量比各50%)和100%污泥基质中构树生长及不同部位(根、茎、叶)养分和重金属吸收累积特征,并通过主成分分析和隶属度函数对吸收累积能力进行综合评价。结果表明: 构树在50%和100%污泥中均可正常生长且株高、生物量显著高于对照,在100%污泥中长势最好,质量指数(1.02)分别是对照和50%污泥处理的4.3和2.4倍。50%和100%污泥处理构树各部位N含量和茎P含量显著高于对照,100%污泥处理构树茎、叶K含量显著低于对照。构树对Cu、Zn、Pb、Cd、Ni的吸收部位以根为主,根系重金属含量与污泥比例呈正相关,叶Pb、Cd含量符合《饲料卫生标准》(GB 13078—2017)。构树对Cd的吸收累积效果好于其他重金属元素。与对照相比,50%和100%污泥处理构树根部Zn、Pb、Cd滞留率显著提高(57.8%~85.8%),100%污泥处理构树根部Cu、Ni滞留率显著提高(67.5%和74.8%)。污泥处理全株养分和重金属累积量均显著大于对照,其中100%污泥处理显著大于50%污泥处理。与50%污泥处理相比,100%污泥处理构树各部位及全株养分和重金属累积量大幅提高。不同处理下构树污泥适应性和元素吸收累积的综合评价得分为100%污泥(0.848)>50%污泥(0.344)>对照(0.080)。构树对污泥具有良好的适应性,在纯污泥中能够正常生长并具有较强的吸收累积养分和重金属能力,可在修复污泥的同时进行构树资源生产。     

Removal of excess activated sludge by aerobic mineralization

The removal of excess activated sludge from biological purification plant treating crude oil refining wastewaters by the method of aerobic digestion was studied. In stationary system 58% of excess sludge was removed within 32 days. In semicontinvous system (with daily addition of sludge) 85--64% of the sludge was removed, depending on amount of excess activated sludge added. Enrichment of the aerating air in oxygen (10% v/v) increased the efficiency of sludge digestion by about 10%.     

Impacts of sterilization, microwave and ultrasonication pretreatment on hydrogen producing using waste sludge

Hydrogen production by sterilization, microwave and ultrasonication pretreated waste sludge was investigated in this study. A new strain of Pseudomonas sp. GZ1 (EF551040) was inoculated in pretreated waste sludge to produce hydrogen. The experimental results showed that different pretreated sludge had evident differences in the yield of hydrogen production and lag time. Sterilized sludge had the largest yield of hydrogen production, and the maximum yield was 15.02 ml/gTCOD. The lag time of using sterilized sludge was 15 h, longer than other two pretreated sludge. Using the ultrasonicated sludge, the hydrogen production yield was smallest and lag time was shortest in the three pretreated sludge. Protein and carbohydrate could be released from waste sludge by pretreatment. Protein was the main nutrient used for hydrogen production. The concentration of protein, carbohydrate and SCOD increased after pretreatment and fermentation. The impacts of different pretreatments on hydrogen production were also discussed in detail.