Effects of Ultrasonic on the Dehydration Function of Sludge and Discussion on Internal Mechanism

[Objective] The aim was to study the effects of ultrasonic on the dehydration function of sludge and internal mechanism.[Method] Taking the residual sludge from a municipal domestic sewage treatment plant as an object,the effects of ultrasonic time and sound energy density on the dehydration function of sludge were studied firstly,then the internal mechanism of improvement of sludge dehydration function by ultrasonic was discussed.[Result] As the increase of ultrasonic time,sludge particles became smaller,and COD of sludge filtrate went up obviously;meanwhile,the capillary suction time (CST) of sludge increased firstly and then decreased,and the minimum value (75.7 s) appeared when ultrasonic time was 8 s.With the raising of sound energy density,the size of sludge particles went down gradually.However,long ultrasonic time and high sound energy density could decrease the dehydration function of sludge.For the possible mechanism of improvement of sludge dehydration function by ultrasonic,ultrasonic adjusted and regrouped sludge,and hydration water in the sludge was released.[Conclusion] The study could provide certain theoretical foundation for the industrial application of ultrasonic.

Modification technology for separation of oily sludge

Based on the analysis of the properties of oily sludge samples,the effect of modification parameters,such as liquid to solid (L/S) ratio,agitation temperature,agitation intensity,agitation time and pH on the modification of oily sludge was investigated with the content of oil remnants in dry sludge as a reference index. Remixing experiments were carried out according to a simplex-lattice design,where Sx4056 was used as the demulsifier,petroleum sulfonate as the surfactant and sodium silicate (Na2SiO3) as the dispersant. The surface modification reagent formulation was optimized by a regression equation on the modified effect and based on the amounts of surface modification reagents. The results show that the content of the oil remaining in dry oily sludge is 0.28% of 10.15% oily sludge,when the reagent concentration rises to 3.5 g/L under the optimum experimental conditions.

Strontium ferrite powders prepared from oily cold rolling mill sludge by solid-state reaction method

Oily cold rolling mill （CRM） sludge is one of the pollutants emitted by iron and steel plants. Recycling oily CRM sludge can not only reduce pollution but also bring social and environmental benefits. In this study, using oily CRM sludge as sources of iron oxide, the strontium ferrite powders were synthesized in multiple steps including vacuum distillation, magnetic separation, oxidizing roasting, and solidstate reaction. The optimal technological conditions of vacuum distillation and oxidizing roasting were studied carefully. To consider the effects of Fe203/ SrCO3 tool ratio, calcination temperature, milling time and calcination time on magnetic properties of prepared strontium ferrite powders, the orthogonal experimental method was adopted. The maximum saturation magneti- zation （62.6 mA-m2.g-1） of the synthesized strontium ferrite powders was achieved at the Fe203/SrCO3 mol ratio of 6, 5 h milling time, 1250 ~C calcination temperature, and 1 h calcination time. Strontium ferrite powders syn- thesis method not only provides a cheap, high quality raw material for the production of strontium ferrite powders, but also effectively prevents the environmental pollution.

Synthesis and properties of SrFe_(12)O_(19) obtained by solid waste recycling of oily cold rolling mill sludge

The aim of this study was to develop a new approach for the preparation of environmentally friendly, high-value products from oily cold rolling mill(CRM) sludge. Utilizing oily CRM sludge as a source of iron, strontium hexaferrite(SrFe_(12)O_(19)) powders were prepared by multi-step processes involving acid leaching, chemical conversion treatment, and synthesis by a citrate precursor. The influences of citric acid dosage and the pH of the sol system on the formation, crystallite size, and magnetic properties of the obtained SrFe_(12)O_(19) powders were investigated. High saturation magnetization(74.8 mA·m^2·g^(–1)) and intrinsic coercivities(614.46 mT) were achieved for pH 7.0 of the sol system, for which the molar ratio of citric acid dosage to the total dosage of Fe^(3+) and Sr^(2+) was 1.5. This study presents a new approach to utilizing oily CRM sludge, and even refractory iron-containing solid waste.

Characterization of oil component and solid particle of oily sludge treated by surfactant-assisted ultrasonication

The ultrasonic technique has been demonstrated to be a promising method for the disposal of hazardous oily sludge.However,the separation of oil from the surfaces of the solid particles is still difficult due to the strong interaction between the oil and solid particle.In this study,three types of surfactants were used to assist the ultrasonic treatment of oily sludge.The oil component,surface composition,and structure of the solid particle were determined.The results showed that different surfactants had different oil removal abilities.In the three surfactant-assisted sonication systems,the oil removal rate increased during the starting reaction period and then decreased with longer sonication time.The results of four components analysis suggested that surfactant easy to be ionized in water posed a better removal effect on resins,while the amphiphilic surfactant preferred saturates,aromatics and asphaltenes.The morphology analysis indicated that particle size was shattered into smaller ones by the ultrasonic process,and the wettability of the solid surface also changed during this treatment.The characterization of the oil component and solid particle during surfactant-assisted ultrasonication treatment will help to better understand the separation of oil from oily sludge and improve the oil recovery efficiency from oily sludge.

Application of hydrophobic ionic liquid [Bmmim][PF6] in solvent extraction for oily sludge

In this study, an ionic liquid(IL), 1-butyl-2,3-dimmmethylimidazolium hexafluorophosphate([Bmmim][PF6]),was used in combination with a composite solvent of methyl acetate and n-heptane to enhance the oil extraction from oily sludge. The oil recovery increased by approximately 15% compared with that of solvent extraction without [Bmmim][PF6] at the optimal ratios of IL to sludge and solvents to sludge, which were at 2:5(M/M) and 4:1(V/M), respectively. The saturate, aromatic, resin and asphaltene(SARA) analysis revealed that the recovery of resins and asphaltenes was increased by 14% and 38%, respectively, in the solvent extraction with the addition of [Bmmim][PF6]. [Bmmim][PF6] maintained a good performance after its reuse four times. The addition of[Bmmim][PF6] changed the adhesion forces between oil and soil. The IL-assisted solvent extraction procedure followed the pseudo second-order kinetic model, while the unassisted solvent extraction procedure followed the pseudo first-order kinetic model. The results also demonstrated that [Bmmim][PF6] decreased the solvent consumption by approximately 60% each time. Additionally, [Bmmim][PF6] can be easily separated. The results suggested that enhancing the solvent extraction with this IL is a promising way to recover oil from oily sludge with a higher oil recovery rate and lower organic solvent consumption than those with the unassisted solvent extraction method.

Experimental Study on Three-phase Separation of Oily Sludge

Three-phase centrifuge was used to process oily sludge,and the requirement of mud,oil and water three-phase separation was satisfied through the optimization of parameters. The results showed that when the input quantity was lower than 5 m^3/h,the optimal operation parameters of the three-phase centrifuge are shown as follows: the frequency of the main motor and vice motor was 33 and 30 Hz respectively,and the flocculant flow was 0. 7 m^3/h,while the oily sludge temperature was 55 ℃. Water content in the separated sludge decreased from 98% to lower than 70%,and the goal of reduction and harmless treatment of oily sludge could be achieved,which could provide essential conditions for subsequent resource utilization and could be used to guide industrial production.

Preparation and Bloating Mechanism of Porous Ultra-lightweight Ceramsite by Dehydrated Sewage Sludge and Yellow River Sediments

To solve the disposal problems of solid wastes, dehydrated sewage sludge and Yellow River sediments were tested as components for production of ultra-lightweight ceramsite. The effects of Yellow River sediments addition on the characteristics of ceramsite were investigated. Ceramsite with different Yellow River sediments additions was characterized using thermal analysis, X-ray diffraction, morphological structures analyses, pore size distributions and porosity analyses. Chemical components, especially ratios of Si O2 ＋ Al2O3/Flux, were used to explain the glassy shell formation, physical properties and pores distribution of ultralightweight ceramsite; physical forces for instance expansion force and frictional resistance which combined with Si O2 ＋ Al2O3/Flux ratios were used to explain the bloating mechanism. Results showed that the maximum addition of Yellow River sediments for making ultra-lightweight ceramsite was 35%. Macropores（between 0.226 μm and 0.554 μm） of ultra-lightweight ceramsite were dominant in the pore structures of ultra-lightweight ceramsite and its porosity was up to 67.7%. Physical force of expansion force was constant with the variation of Yellow River sediments content and physical force of frictional resistance was decreased with the increase of Yellow River sediments addition. The relationship between expansion and frictional resistance could determine the expansion rate of ceramsite. Larger pores inside the ceramsite bodies could be obtained as Yellow River sediments additions ranged from 10% to 30%. Ceramsite with higher Yellow River sediments additions of 40%（Si O2 ＋ Al2O3/Flux ratios 4.25） became denser and have lower porosity. Crystal components analysis proved that the sintering process made some components of raw materials transfer into other crystals having better thermostability.

Solid- liquid phase separation and resource recycling study for waste rolling oily sludge

On the basis of the characteristics of a highly emulsified solid-liquid phase （fine particles, sticky consistency,black color, and low reuse ratio）, waste rolling oily sludge has been a focal problem in the steel industry. In this article, a solid-liquid phase separation and resource recycling process was described, with pilot test results showing that flocculation-sedimentation is an effective pretreatment, and that the filtration-coagulationvacuum distillation process is simple and feasible with a 53.5% recovery rate for regenerated oil that is qualified for return to the roiling production line. Then,solid phase oil-sludge was extracted by solvents with a 77% metal resource recovery rate and a wide utilization range. Finally, according to the experimental results, a set of feasibility plans for a 50 t/a waste rolling oily sludge solid-liquid separation and resource recycle project was designed, with the expectation of 50% regenerated oil yield, 70% solid metal resource recovery, and a 2. 5-year investment payback period.

Application of Screw Press Filter for Oily Sludge Dewatering

In order to find suitable oily sludge treatment equipment for a produced water treatment station of an oilfield in Iraq,the widely used mechanical dewatering equipments overseas including plate and frame filter,belt press filter,centrifugal filter and screw press filter were compared and analyzed,and the application situation of screw press filter was investigated at site. The site survey showed that,screw press filter was an integrated equipment combined with functions of concentrating and dewatering,which was characterized by low water content of filter cake,small occupied area,easy to separate,no blocking and can realize self-cleaning,which is suitable to low concentration sludge. Screw press filter can simplify oily sludge treatment process,and save engineering construction and operation cost,which is a better choice for oily sludge dewatering. The design of screw press filter adopted in the produced water treatment station of an oilfield in Iraq was introduced here.

Pollution characteristics of polycyclic aromatic hydrocarbons (PAHs) in oily sludge from the Zhongyuan Oilfield and its peripheral soils

The purpose of this study is to determine the degree of contamination caused by polycyclic aromatic hydrocarbons (PAHs) in oily sludge and soils around it in the Zhongyuan Oilfield. The contents of polycyclic aro-matic hydrocarbons in oily sludge samples were determined with HPLC. The contents of PAHs of oily sludge from three different oil production plants vary from high to low in the order of the Wenming oily sludge dumping site of No. 3 Oil Production Plant (3W)>the Mazhai oily sludge dumping site of No. 3 Oil Production Plant (3M)>the Wen'er oily sludge dumping site of No. 4 Oil Production Plant (4W). Naphthalene, acenaphthylene, acenaphthene, fluorine and phenanthrene are the major pollutants of PAHs in oily sludge. The contents of PAHs in soil samples around the oily sludge dumping sites vary widely from 434.49 to 2408.8 ng/g. Naphthalene, acenaphthene, fluorine, phenanthrene and pyrene are the characteristic factors of PAHs in soil samples of 3M and 3W, and naphthalene, acenaphthene, fluorine and phenanthrene are the characteristic factors of PAHs in soil samples of 4W. According to these data and the ratios of Fl/Py, PAHs in oily sludge samples come mainly from petrogenic sources, and soil samples are divided into petrogenic soil samples and mixed-source soil samples, and both petrogenic and pyrogenic soil samples in terms of the sources of PAHs. The classification by Nemero index P indicates that soils around the oily sludge dumping sites have been seriously polluted.

Dissipation of polycyclic aromatic hydrocarbons in crop soils amended with oily sludge

Oil fields present a potential ecological risk to nearby farmland soil. Here we present a new method designed to evaluate the ability of winter wheat(Triticum aestivum) to contribute to the dissipation of polycyclic aromatic hydrocarbons(PAHs), which are priority pollutants in soils contaminated by oily sludge. The influence of different doses of oily sludge on the dissipation of PAHs was studied along with individual PAH profiles in soils after different periods of plant growth. Five soil samples were artificially contaminated with different percentages of oily sludge(0 %, 5 %, 10 %, 15 % and 20 %). Winter wheat grew in the oily sludge–amended soils for 265 days.PAH content in the soils was monitored over the course of the study. The rate of PAH dissipation is related to the properties of different PAHs, period of winter wheat growth, and oily sludge application dose. Analysis for treated soils indicates that the dissipation of PAHs increased significantly over the first 212 days, followed by minimal changes over the final 53 days of treatment. In contrast, PAH dissipation slowed with increasing oily sludge application. For each PAH, the experimental results showed a significant compound-dependent trend. Winter wheat in the present study significantly enhanced the dissipation of PAHs in oily sludge–contaminated soil.

Theoretical study on the pressurization characteristics of disc-seal single screw pump used in high viscosity oily sludge conveying field

The disc-seal single screw pump(DSSP)used in the field of high viscosity oily sludge transport has a huge advantage.However,there is no research on the pressurization characteristics of the DSSP at present,which makes its application limited.In view of this,the pressurization process mathematical model of the DSSP was established based on the geometric model of the pump.By using this model,the pressurization characteristics of DSSP and the influence of working parameters on the pressurization process were studied combined with the principle of back-flow pressurization.Analysis results show that the instantaneous pressurization process could be realized mainly depending on the reflux pressurization from the outlet chamber to the pressurization chamber when the screw rotor rotating angle is located at-5°to+5°.The pressure in the pressurization chamber will increase with the increase of working parameters which include inlet pressure,outlet pressure,screw rotation velocity and dynamic viscosity of fluid medium in the area of flow-back pressurization.The screw rotation velocity and the viscosity of the conveying medium have significant effects on the peak pressure in the pressurization chamber,and the peak pressure in the pressurization chamber is proportional to the screw rotation velocity and the dynamic viscosity coefficient of the conveying medium.The proportional coefficient between the peak pressure and the screw rotation velocity is 6.29×10~4.The proportional coefficient between the peak pressure and the dynamic viscosity of the conveying medium is 6.28×10~6.

Oil Phase Molecular Compositions of Oily Sludge Using Mass Spectrometry

Oily sludge was recognized as a kind of hazardous wastes,so recycling its high content of petroleum hydrocarbons can contribute to the clean environment.In this study,oily sludge was subjected to continous ultrasonic extraction with an acetone/carbon disulfide(CS2)mixture solvent.Fourier transform infrared spectroscopy(FTIRS),gas chromatography/mass spectrometry(GC/MS),and Quadrupole exactive Orbitrap mass spectrometry(QPEOTMS)were used to analyze the oil phase compounds from oily sludge.The n-alkanes ranging from C8 to C31 hydrocarbons were detected in oil phase.Compared with the analysis results of GC/MS,more heteroatom-containing compounds(HACOCs)of oil phase such as O3,O4,N2Oo and N3Oo(o=0—3)could be detected by using the QPEOTMS analysis.Overall,these findings will potentially contribute to the clean and efficient utilization of oily sludge.

Uptake, accumulation and translocation of polycyclic aromatic hydrocarbons by winter wheat cultured on oily sludge-amended soil

The purpose of this study is to comparatively investigate the plant uptake, accumulation and translocation behaviors of polycyclic aromatic hydrocarbons (PAHs) as priority pollutants in soil contaminated with oily sludge. The influence of different oily sludge application doses on the uptake of contaminants was studied together with the profile of individual PAH in roots, straws and leaves of winter wheat. Pot experiments were conducted using oily sludge application doses of 0, 5, 10, 15 and 20 percent, respectively. The total PAHs contents of control soil and oily sludge were 16.96 and 3504.66 μg/g, respectively. Analysis for the contents of the 16 PAHs was carried out with a HPLC-UV using plant tissue samples obtained at the 265th day of growth. The total PAHs contents in treated winter wheat were 9.02-334.81 ng/g for roots, 8.45-336.52 ng/g for straws and 10.70-406.32 ng/g for leaves. In addition to 5% of oily sludge dose, the total PAHs content in leaves was always highest under other doses of oily sludge application. With respect to individual PAH, the content did not show a significant plant tissue related trend. However, both the total content and individual content of PAHs in treated winter wheat tissues did increase with increasing oily sludge application dose. Another analysis for the control soil indicates that the degradation rate of PAHs was significantly enhanced by winter wheat after 265 days of growth based on the residual concentrations of PAHs in planted and unplanted soils.

Application of Chitosan Flocculant to Conditioning Sludge

The dewaterability of activated sludge conditioned by chitosan flocculant was studied. The effects of chitosan characteristics such as molecular weight, degree of deacetylation, and dose on the dewaterability were investigated. The sludge dewaterability is evaluated in terms of specific resistance to filtration, residual turbidity of supernatant, moisture content of cake, and settling rate. Sludge dehydrating behaviors conditioned with CTS, PAM and PAC flocculants were compared. The conditioning was also carried out with dual flocculants in two stages. It is found that the sludge conditioned with CTS has better dewaterability than that with PAC. The optimum conditions with chitosan are: dose 0.8 - 1.2 g per 100 g dry cake, molecular weight 300,000, and degree of deacetylation 70%. The conditioning in two stages with dual flocculants is found to be more effective than that with single flocculant.

生物表面活性剂烷基多苷强化含油污泥厌氧资源化利用的机制解析

为了探究生物表面活性剂烷基多苷(APG)对含油污泥的厌氧资源化利用的影响,构建了序批式厌氧污泥反应器,探究了APG的含量对含油污泥资源化利用的影响,结果表明APG能够高效地提高含油污泥厌氧发酵产挥发性脂肪酸(VFA),且APG的最佳含量为6%,对应VFA的最大浓度为186.5 mg/g VSS。APG促进了VFA内小分子羧酸如乙酸和丙酸的占比。APG提高了含油污泥的溶出和水解过程,促进了有机质的释放。此外,APG有效促进了油脂的释放与利用,在6%APG组别内,油脂利用率高达75.6%。酶活性分析揭示APG促进了负责水解方面蛋白质和淀粉酶,酸化过程PTA、AK和BK的相对活性。APG促进了含油污泥厌氧发酵内副产物氨氮和磷酸盐的释放。研究结果拓宽了APG的应用范围并为含油污泥的资源化提供备选方案。

基于全生命周期的污油泥热脱附处理技术评价

基于全生命周期评价(LCA)软件eFootprint和国内典型污油泥热脱附处理实际,从绿色和可持续性两个方面对污油泥热脱附技术进行评价。结果表明:污油泥热脱附处理过程中,主要评价指标按所产生的环境影响由大到小排列依次为可吸入无机物(RI)、富营养化潜值(EP)、竞争-土地使用(CLU)、臭氧层消耗潜值(ODP)和水资源消耗(WU);回收油和天然气是初级能源消耗(PED)、非生物质资源消耗潜值(ADP)、WU、全球增温潜势(GWP)、ODP等11项评价指标的主要贡献因素,蒸汽是影响RI的最主要因素;污油泥热脱附处理产生的回收油能够抵消热脱附处理过程的部分能源和资源消耗,从而减小PED、ADP、GWP等评价指标的数值;为了进一步提升污油泥热脱附处理技术的绿色和可持续性,建议提高能源效率,减少蒸汽消耗,回收蒸汽余热,优化尾气净化系统和器具清洗系统,减少废水排放和水分挥发。

掺油泥改性生土材料动态荷载下的损伤及裂缝分形特征

为研究改性生土材料在动态荷载作用下内部损伤演化过程,提取掺入水泥、油泥的绿色改性生土材料配方,制作6个100 mm×100 mm×100 mm的生土试件,借助CT扫描技术对单轴压缩下的立方体试件进行扫描,获取灰度图像和CT值,分析了图像中裂缝、孔隙随应力的变化形态,研究了CT数和材料破坏的关系,建立了CT均值与应力之间的联系;采用图像处理技术对CT图像进行阈值划分,利用盒维数法估算出图像的分形维数值,在此基础上获得了不同应力和分形维数、材料损伤之间的关系。结果表明:CT技术能够清晰地诠释试件从受力直至破坏的全过程,CT图像可从细观层面表现材料的损伤演化规律。CT值随应力的增加而变小,CT值随材料孔隙、裂缝的增大而显著减小。材料从受力直至破坏,低应力状态下分形维数增长缓慢,高应力状态下分形维数增长迅速,数值的波动随应力的增大而增大。分形维数可以定量地描述生土材料在动荷载作用下的损伤状态和演化过程。

聚合硫酸铁絮凝剂对好氧颗粒污泥处理含油废水的影响

为了明确絮凝剂PFS对好氧颗粒污泥颗粒化及运行效能的影响,以PFS和含油废水为探究对象,研究了PFS浓度对AGS处理含油废水的影响并揭示相关机制。结果表明,PFS存在利于AGS颗粒化,提高ASG内污泥浓度及大粒径污泥占比。AGS稳定性分析表明PFS提高了胞外聚合物含量,并促进了蛋白质和多糖含量,提高了Zeta电位。PFS促进了AGS处理含油废水过程内污染物、营养盐和油脂的去除,且PFS的最佳含量为50 mg/L。PFS作为骨架结构为微生物增殖提供便利条件。此外,PFS具有一定吸附能力从而提高了污染物、营养盐及油脂的去除。研究结果为AGS处理含油废水过程内快速颗粒化提供一定的数据支撑和理论依据。