CaO低温预处理作用下市政污泥有机物迁移规律及与粘滞性的关联

通过向机械脱水后污泥中添加CaO粉末,在不同预处理时间和温度条件下,测量污泥提取液中蛋白质和多糖的含量,探究不同预处理条件对污泥上清液中有机物含量变化的影响,以及对污泥表面粘附性的影响。测量结果表明,预处理时间的延长会提高污泥上清液中有机物含量；预处理温度的升高也会提高有机物含量；CaO粉末的添加能提高有机物含量,但是添加剂含量过高反而会降低有机物含量,如10%CaO添加量时有机物含量反而减少。研究发现,随着CaO引入,污泥表面粘性有明显增加,并推断这和CaO导致的胞内高粘性有机物大量释放密切相关。采用旋转粘度计测量不同CaO含量污泥的粘度值,结果表明,随着CaO添加量的增加,污泥粘性明显降低,但CaO含量达到8%和10%时,污泥混合物的粘度则随时间延长开始增加。     

Solar drying in sludge management in Turkey

Two main wastewater treatment plants in Bursa city in Turkey will start to operate and produce at least 27,000 tons of dry solids per year by the end of 2006. The purpose of this study was to investigate an economical solution to the sludge management problem that Bursa city would encounter. The general trend in Turkey is mechanical dewatering to obtain a dry solid (DS) content of 20%, and liming the mechanically dewatered sludge to reach the legal landfilling requirement, 35% DS content. This study recommends limited liming & solar drying as an alternative to only-liming the mechanically dewatered sludge. Open and covered solar sludge drying plants were constructed in pilot scale for experimental purposes. Dry solids and climatic conditions were constantly measured. Faecal coliform reduction was also monitored. The specially designed covered solar drying plant proved to be more efficient than the open plant in terms of drying and faecal coliform reduction. It was found that, if the limited liming & solar drying method was applied after mechanical dewatering instead of only-liming method, the total amount of the sludge to be disposed would be reduced by approximately 40%. This would lead to a reduction in the transportation, handling, and landfilling costs. The covered drying system would amortize itself in 4 years.     

规模化猪场厌氧消化污泥脱水工艺研究

规模化猪场厌氧消化污泥堆肥是消化污泥处置的最重要途径之一,而作为污泥堆肥的重要预处理环节,消化污泥脱水却一直是道难题,文章就如何选择合理的污泥脱水工艺展开深入探讨.研究表明,规模化猪场消化污泥具有相对密度小、比阻大、有机养分含量高等特点,运用机械方法脱水不但费用高,而且技术上难度大,还会破坏消化污泥原本的有机养分组成,降低其堆肥后的农用的价值;和机械脱水方法相比,自然脱水方法在经济上具有明显的优势,而且技术上也可行.最后,文章认为污泥干化床工艺是自然脱水方法中较为理想的厌氧消化污泥脱水工艺.     

Coupling of hydrothermal pretreatment and supercritical water gasification of sewage sludge for hydrogen production

In this study, hydrothermal pretreatment and supercritical water gasification were coupled to form a combined process for the treatment of dewatered sludge for hydrogen production. First, the effects of varying hydrothermal pretreatment conditions on the transformation of organic matter in sludge were studied. Results showed that about 31% of the carbon in sludge was transferred into liquid products at 250 °C for 60 min, which were considered to be the optimal pretreatment conditions considering both the hydrothermal pretreatment effects and the energy consumption requirements. The organic matter components were determined, showing that 87% of the carbohydrate components in sludge were transformed during the process of hydrothermal pretreatment, with 49% of crude proteins and 62% of humus remaining in the solid phase products. During the subsequent process of supercritical water gasification, AlCl₃, KOH, K₂CO₃ and CaO were selected as catalysts. Compared with directly catalyzed supercritical water gasification of sludge, the integrated process was found to improve H₂ selectivity, H₂ yield and energy recovery. Moreover, the use of AlCl₃ as a catalyst showed the highest H₂ yield and energy recovery. The H₂ yield and the energy recovery increased by 45.1% and 13.2%, respectively.     

Fermentative hydrogen production by conventionally and unconventionally heat pretreated seed cultures: A comparative assessment

In this study, the effects of pretreatment temperature and time during conventional and unconventional, microwave-assisted heat shock on the hydrogen producing capability of anaerobic seed sludge from soluble starch was focused. It was found that the different heat transfer techniques resulted in seed cultures with comparable hydrogen production potentials, with the highest obtainable values of approximately 0.9 L H₂/L-d. A comprehensive, statistical analysis revealed that both treatment temperature and time could be designated as significant process variables, however, in distinguishable extents for the two alternative methods. The results indicated that microwave-based sludge pretreatment needed remarkably shorter curing times (2 min) to eliminate H₂-consuming, methanogenic activity in comparison to the conventional heat shock method (30 min). It was also demonstrated that microwave irradiation increased the soluble organic matter content in the seed sludge.     

超声波预处理对污泥干燥速率影响研究

在超声波预处理污泥干燥实验基础上,分析了超声波预处理技术对污泥干燥速率的影响,并对污泥干燥过程进行了指数拟合,结果表明.超声波预处理能有效提高污泥干燥效率,其改善的程度取决于不同的实验条件;超声波预处理能够加速表面自由水分蒸发和快速结束污泥恒速干燥阶段;增大超声波功率可以更好地改善污泥的干燥特性,但改善的程度随着十燥时间的延长而放缓;超声波处理时间过长可能会增大污泥的黏度,反而不利于污泥脱水干燥.     

Advances in economically driven optimization of processing of biosolids from sewage sludge

Management of biosolids from sewage sludge is a problem of global importance with comprehensive environmental and economic impacts. A wide portfolio of various processing techniques was investigated during last decades, however, most of them failed from the economic point of view. This study initially mentions some inhibition mechanisms in the steam-explosion pretreatment followed by anaerobic fermentation and assesses them in a commercial scale from the technological–economic point of view. Several synergies have been observed that improve the management of biosolids (increased CH₄ production, deeper removal of the organic matter, and easier dewatering). Nevertheless, other results indicate that the full technological–economic potential is far from being achieved.     

Optimization of dilute acid and hot water pretreatment of different lignocellulosic biomass: A comparative study

Pretreatment of biomass to alter their recalcitrant structures is an essential step to obtain high yield of products via bioconversion processes. In this study, main emphasis was to compare the results evaluated in terms of total reducing sugars (TRS) yield after acid and hot water pre-treatment process performed with laboratory scale equipment using different lignocellulosic biomass. The biomass chosen for this purpose i.e. sugarcane bagasse and bamboo were collected from Guwahati, Assam and their physico-chemical characteristics were examined using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermo gravimetric analysis (TGA) including proximate and ultimate analysis. Crystalinity of the biomass used was observed to be 33.15% and 31.29% for sugarcane bagasse and bamboo respectively. Hot water and dilute acid pretreatment allows selective solubility of hemicellulose which improves the accessibility of enzymes for cellulose hydrolysis. The highest yield of TRS was observed at run order 8 for both acid and hot water pretreatment (23.49 and 26.50 gL⁻¹) with respect to sugarcane bagasse. But, the pretreatment results obtained for bamboo was slightly different to that of sugarcane bagasse. The highest yield of TRS was obtained at run order 8 for acid (15.6 gL⁻¹) and run order 10 for hot water (17.98 gL⁻¹) pretreatment respectively. Irrespective of biomass type, hot water pretreatment process produced more TRS than acid pretreatment process.     

污泥脱水性能指标的比较分析

研究了评价污泥脱水性能的4个指标:毛细吸水时间(CST)、污泥比阻(SRF)、结合水(BW)、含固率(DS)之间的相关性,发现DS与标准化CST、SRF、BW显著相关。标准化CST与SRF极显著相关,与BW的相关性较弱,SRF与BW的相关性更弱。研究结果表明,在衡量污泥的脱水性能时没必要同时测定CST和SRF,CST测定简单,重现性好,是衡量污泥脱水性能的较好指标,但同时,也应当与衡量污泥脱水程度的指标,如含固率等,一起综合考虑污泥的脱水性能。     

A comprehensive review on pretreatment of microalgae for biogas production

Use of microalgal biomass for renewable energy production has gained considerable attention in the world due to increasing global energy demand and negative environmental impacts of nonrenewable fossil fuels. Anaerobic digestion is one of the renewable technologies that microalgal biomass is converted into biogas by anaerobic archea. One of the main drawbacks of using microalgal biomass for biogas production is that certain types of microalgae has rigid cell wall characteristics, which limits accessibility of anaerobic archea to microalgal intracellular organic matter during hydrolysis phase. This limitation lowers efficiency of biogas production from microalgal biomass. However, introducing pretreatment methods prior to anaerobic digestion provides disruption of rigid microalgal cell wall and improve biogas yields from microalgal biomass. The objective of this paper was to review current knowledge related to pretreatment methods applied prior to anaerobic digestion of microalgal biomass. Efficiency and applicability of pretreatment methods mainly depend on type of microalgae, cell wall characteristics, and cost and energy requirements during pretreatment process. In this review, various type of pretreatment methods applied to microalgal biomass was discussed in detail with background knowledge and literature studies in their potential on maximization of biogas yields and their cost effectiveness, which is important for large‐scale applications. In the view of current knowledge, it was concluded that each pretreatment method has a relative contribution to improvement in biogas production depending on the type of microalgae. However, energy and cost requirements are the main limitations for pretreatment. So, further studies should focus on reduction of cost and energy demand by introducing combined methods, novel chemicals, and on‐site or immobilized enzymes in pretreatment to increase feasibility of pretreatment prior to anaerobic digestion in industrial scale.     

Enhanced anaerobic digestion of sewage sludge by thermal or alkaline-thermal pretreatments: Influence of hydraulic retention time reduction

The influence of hydraulic retention times (HRTs) reduction from 25 days to 15 days on the enhancement effects of two pretreatments (thermal pretreatment and alkaline-thermal pretreatment) on the continuous anaerobic digestion (AD) of sewage sludge was studied in a long-term experiment (196 days). The operation of the semi-continuous AD fed with raw sludge or pretreated sludge was stable at the three HRTs. The methane production increased from 70.6 to 165.8 ml/L·d to 75.2–172.6 ml/L·d and the methane yield decreased from 98.9 to 234.9 ml/g added volatile solid to 65.6–144.9 ml/g added volatile solid when the HRT reduced from 25 days to 15 days. The two pretreatments reduced the HRT of raw sludge AD by over 40%, and the effects of the alkaline-thermal pretreatment were greater than those of the thermal pretreatment. The reduction of HRT from 25 days to 15 days increased the enhancement effects of the two pretreatments on the removal of organic matter (4.7–15.9% for volatile solid), average hydrolysis ratio (36.9–116.4%), and specific hydrolysis rate (44.1–155.6%) but decreased the enhancement effects of the pretreatments on the methane production (0.9–4.6%) and yield (4.0–15.8%), average reaction ratios (0.4–8.2%), and specific rates of the last three AD steps (0.1–13.9%). The influence of HRT reduction on the enhancement effects of the alkaline-thermal pretreatment for sludge AD was slightly greater than on the enhancement effects of the thermal pretreatment.     

Co-combustion of sludge with coal

Utilisation of waste-water sludge is one of the most difficult processes of environment protection because of the high moisture and contents of harmful substances. The waste-water treatment systems in Poland, especially in small towns, are often not separate from industrial sewage systems and this causes relatively large contents of heavy metals and other toxic substances in the sludge. Incineration is the only effective method of utilisation of such waste material. From the other side, coal is still the most popular fuel in Poland, and it is often used in many boilers producing hot water for the central heating of buildings or parts of the towns. Mostly they are stoker fired boilers of old construction, and they need urgent modernisation. The use of stoker-fired boilers for incineration of the sludge in small towns is the object of the analysis presented in this paper. There are two important points in the co-combustion of sludge with coal in a stoker-fired boilers: ecological and exploitation requirements. The important restriction of the sludge/coal ratio is the emission of harmful substances with the flue gas. There are substances originating from the components of the sludge: SO₂, NO_x, HCl, heavy metals and dust. Their concentrations in the flue gas should meet the environmental regulations. The other factor influencing the co-combustion process is the change of physical and thermal properties of the fuel: heating value, moisture content and ash composition. These influence the thermal output of the boiler, the amount of air required for combustion, the volume of flue gases and dust concentration and particle distribution. In this paper, the results of experiments performed with an experimental boiler are presented. The effects of the following parameters are considered: composition and thermal parameters of the sludge and their change during the year, emissions of SO₂, NO_x, CO and dust from the experimental boiler for various compositions of the fuel (sludge/coal ratio, moisture content). As a result of the analysis, the parameters limiting the amount of sludge in a mixture with coal are identified.     

Evaluation of different pretreatment methods for preparing hydrogen-producing seed inocula from waste activated sludge

Waste activated sludge (WAS) is the most favorable inoculum for dark fermentative hydrogen-producing processes, because it can be collected economically. In order to accelerate the start-up process and develop the efficiency and stability of a hydrogen production system, pretreatment of the seed sludge has been examined to enrich hydrogen-producing bacteria. Six pretreatment methods including acid, base, heat-shock, aeration, chloroform and 2-bromoethanesulfonate (BES) were performed on WAS in batch cultures utilizing glucose as the substrate. The results showed that, at 35 °C and initial pH of 7.0, hydrogen yields of the pretreated sludge (except for BES) were higher than the control test. The pretreatment methods resulted in different distributions of soluble metabolites. Acid pretreatment at pH of 3 was the best among all six pretreatment methods, and the maximal hydrogen yield of 1.51 mol/mol-glucose-consumed and the maximal specific hydrogen production of 22.81 mmolH₂/g VSS were observed. The hydrogen yield of the acid treated sludge increased to 1.82 mol/mol-glucose-consumed after five repeated-batch cultivations. It was concluded that acid pretreatment is a simple, economic and effective method for enriching hydrogen-producing bacteria from WAS.     

厨余和污泥不同混合比例碱处理产氢特性研究

以厨余垃圾和污泥为反应底物,加热预处理的污泥为发酵接种物,考察了碱处理下厨余与污泥不同混合比例的发酵产氢特性。结果表明:不同pH碱液对厨余垃圾进行预处理后,其效果以pH=13时最佳,预处理3h后SCOD和还原糖含量分别为31316.8mg/L和5.54mg/mL;碱预处理后的污泥与厨余联合发酵能够改善物料的营养平衡,缩短反应延迟时间到1h内;当厨余与污泥混和比例为5:1时为本试验最佳的试验条件,其氢气含量、比产氢速率峰值和氢产率分别为52.69%,1.73mL H_2/(h·gVS)和50.27mL H_2/gVS。     

Effects of different pretreatment methods on fermentation types and dominant bacteria for hydrogen production

In order to enrich hydrogen producing bacteria and to establish high-efficient communities of the mixed microbial cultures, inoculum needs to be pretreated before the cultivation. Four pretreatment methods including heat-shock pretreatment, acid pretreatment, alkaline pretreatment and repeated-aeration pretreatment were performed on the seed sludge which was collected from a secondary settling tank of a municipal wastewater treatment plant. In contrast to the control test without any pretreatment, the heat-shock pretreatment, acid pretreatment and repeated-aeration pretreatment completely suppressed the methanogenic activity of the seed sludge, but the alkaline pretreatment did not. Employing different pretreatment methods resulted in the change in fermentation types as butyric-acid type fermentation was achieved by the heat-shock and alkaline pretreatments, mixed-acid type fermentation was achieved by acid pretreatment and the control, and ethanol-type fermentation was observed by repeated-aeration pretreatment. Denaturing gradient gel electrophoresis (DGGE) profiles revealed that pretreatment method substantially affected the species composition of microbial communities. The highest hydrogen yield of 1.96 mol/mol-glucose was observed with the repeated-aeration pretreatment method, while the lowest was obtained as the seed sludge was acidified. It is concluded that the pretreatment methods led to the difference in the initial microbial communities which might be directly responsible for different fermentation types and hydrogen yields.     

石化污泥离心脱水处理研究

独山子石化公司对原有石化污泥处理工艺进行了离心脱水技术改造,对影响离心脱水效果的因素进行了分析,确定了离心脱水法污泥处理量为8．4～12．8m^3／h,进离心机污泥含固率控制在1．43％～4．18％,离心机转速为3330r／min,差速为16～25r／min,聚丙烯酰胺投加量在3～8kg／t干泥,脱水后的泥饼含水率不大于85％,固相回收率不小于90％（平均）。改造后药剂节约费用为27．72万元/a,罐车拉运费用每年节约14万元左右。     

预处理温度对活性污泥发酵产氢特性的影响

为寻求适宜的种泥热处理方法,利用摇瓶发酵实验,考察了城市污水处理厂好氧活性污泥分别经65、80、95、110℃热处理30min后,其利用葡萄糖发酵产氢的特性。结果表明:在初始pH=7.0、葡萄糖浓度10g/L、接种量2gMLVSS/L条件下,35℃培养72h,经65℃和95℃处理的种泥表现出较好的发酵产氢性能,其葡萄糖的氢气转化率分别达到1.08和1.11mol/mol,污泥的比产氢率分别为8.36和9.05mmol/gMLVSS;经65℃预处理的种泥发酵体系,表现为丁酸型发酵,其葡萄糖降解率和最大产氢速率分别高达82%和11.29mL/h,而经95℃预处理的种泥发酵体系则呈现混合酸发酵特征,其葡萄糖转化率和最大产氢速率分别仅为76%和4.45mL/h。     

Influence of thermal and chemical pretreatment on structural stability of granular sludge for high-rate hydrogen production in an UASB bioreactor

Fermentation of organic waste materials presents an alternate route instead of photosynthetic and chemical routes for hydrogen production. Low yield of biohydrogen production is the major challenge in the fermentative hydrogen-producing technology. Improvement of fermentation process by various sludge pretreatment methods is one of the ways that have been applied to boost hydrogen productivity. This study sheds new light on the impact of thermal and chemical pretreatments on the hydrogen-producing granular sludge morphology and strength as well as up-flow anaerobic sludge blanket (UASB) reactor performance treating palm oil mill effluent (POME). Thermal pretreatment showed devastating effects on the morphological and structural characteristics of the granules. However, the chemically pretreated granules remained structurally stable and relatively undamaged. The thermal pretreatment increased the cumulative hydrogen production by 40% and 76% over chemical pretreatment and control test (untreated), respectively.     

污泥在流化床中的焚烧特性研究

本文研究了高水分、低热值的污泥在流化床中的结团特性、着火特性。考察了床温、污泥水分、辅助燃料、给料粒径、流化风速对污泥结团的影响，比较了多种不同污泥的结团情况，并运用中间相理论对污泥结团机理作了初步分析。试验结果对于污泥流化床焚烧的基础理论和应用研究都有着重要意义。     

Effect of High-Temperature Microwave Irradiation on Municipal Thickened Waste Activated Sludge Solubilization

Sludge digestion and stabilization governs almost half of the operating cost of wastewater treatment plants, and hydrolysis is the limiting step in sludge digestion. Increasing hydrolysis by implementing pretreatment prior to digestion can increase the digestion efficiency. Among pretreatment methods, thermal pretreatment at temperatures around 160–175°C tends to produce better solubilization. Microwave (MW) pretreatment was recently studied as an alternative method to conventional thermal pretreatment. Until now, MW pretreatment above boiling point had not been studied for sludge solubilization and digestion. This paper provides preliminary results on the effect of MW pretreatment operating conditions such as high temperature (T) (110–175°C), MW intensity (I) (1.25 and 3.75°C/min), and sludge concentration (C) (6 and 11.85%) on solubilization. From experimental results and three-factor fixed-effect analysis of variance (ANOVA) determination it was found that T, I, and C main effects and T:I and T:C interactions as well as T:I:C interaction are significant at a 94% confidence interval.