Research Progress and Development Trend of Disposal Technology for Municipal Sludge in China

At present,main sludge disposal manners of China contain landfill,composting,natural drying and incineration. A large number of sludge does not obtain standardized processing,which directly causes"secondary pollution"and seriously threatens eco-environment. Therefore,how to rationally treat municipal sludge is one of problems that need urgent solution at present. In this paper,current mainstream pretreatment technique of municipal sludge and backend disposal technique are explored,and mainstream backend disposal technique is introduced. Moreover,key problems in municipal sludge disposal field are analyzed,which has certain reference significance for further understanding the current development of municipal sludge disposal field in China.

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.

New technology for recycling materials from oily cold rolling mill sludge

Oily cold rolling mill （CRM） sludge is one of metallurgical industry solid wastes. The recycle of these wastes can not only protect the environment but also permit their reutilization. In this research, a new process of ＂hydrometallurgical treatment ＋ hydrothermal synthesis＂ was investigated for the combined recovery of iron and organic materials from oily CRM sludge. Hydrometallurgical treatment, mainly including acid leaching, centrifugal separation, neutralization reaction, oxidizing, and preparation of hydrothermal reaction precursor, was first utilized for processing the sludge. Then, micaceous iron oxide （MIO） pigment powders were prepared through hydrothermal reaction of the obtained precursor in alkaline media. The separated organic materials can be used for fuel or chemical feedstock. The quality of the prepared MIO pigments is in accordance with the standards of MIO pigments for paints （ISO 10601-2007）. This clean, effective, and economical technology offers a new way to recycle oily CRM sludge.

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.

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.

Recovery of heavy metals from electroplating sludge and stainless steel pickle waste liquid by ammonia leaching method

A coordinative disposal process for treatment of electroplating sludge and stainless steel pickle waste liquid containing Cu, Ni, Zn, Cr and Fe etc., has been developed to recover valuable metals and to eliminate pollution. The recovery of Cu, Ni, Zn and Cr is 94%, 91%, 90% and 95%, respectively. The ammonia was recycled by the simplified process of CaO caustic distillation. The precipitated product of Cu, Ni and Zn obtained from caustic distillation of ammonia was separated by extraction or high\|pressure hydrogen reduction in an autoclave. The qualified metal salt products were obtained through extraction. The rich chromium residue from coordinative disposal was subjected to recover Cr by hydrothermal oxidation in NaOH medium and Fe\-3O\-4 was synthesized by wet methods from the residue produced by extracting Cr. Cr was a stable chemical fixed in Fe\-3O\-4 and harmless. The recovery process has been used in a pilot plant with sludge production capacity of 2000 t/a.

Performance of wastewater sludge ecological stabilization

In this article, wastewater sludge ecological stabilization （WWSES） was presented for sludge dewatering, mineralization, and stabilization, as well as for percolate treatment. Two years of pilot scale experimental results indicated that sludge volatile solid, Wiphenyltetrazolium chloride （TTC）-dehydrogenase activity （DHA）, and moisture content as indicators showed the process and degree of sludge stabilization. The observation on dewatering process showed that dried sludge reached a content of 20%-50% total solid after two years of system operation. Sludge TTC-DHA in the first year was obviously lower than that of the second year, and TTC-DHA tended to decrease with an increase in the drying time of the sludge. Total nitrogen, total phosphorus, and organic contents of sludge decreased gradually from the top to the bottom of dried sludge layer. In comparison with natural stands on stands treated with sewage sludge, individual shoot was significantly higher, and coarse protein, coarse fat, and coarse fiber contents in reed roots, stems, and leaves in the system were higher than that of wild reed, especially coarse protein contents of reed roots in the system （7.38%） were obviously higher than that of wild reeds （3.29%）.

Effect of Industrial Sludge Application on Soil Nitrogen and Wheat Plant Response

Wazirpur industrial area of Delhi generates a huge quantity of sludge per day, which is highly acidic in nature (pH 2.7 to 4.4) and contains macronutrients, micronutrients as well as toxic metals. A pot-culture experiment was conducted by taking the two soils (JNU and Chhattarpur) amended with sludge (0%, 10%, 20%, 30%), pretreated with lime (0%, 0.5% and 1%). Two wheat seedlings were planted per pot containing 3 kg sludge amended or control soil and the experiment was carried out till harvesting (four months) in a glass house. Lime treatments enhanced the N content in wheat plant in almost all cases. Sludge and lime treatments enhanced dry weight in wheat plants grown in Chhattarpur soil and dry weight increased with time. Maximum growth was observed in 0.5 lime treated and 20% sludge amended soils. But we have to take an account about any kind of metal toxicity before disposal of this waste to land.

Insights into multisource sludge distributed in the Yangtze River basin, China: Characteristics,correlation, treatment and disposal

Sludge is the by-product of wastewater treatment process. Multisource sludge can be defined as sludge from different sources. Based on the sludge properties of five typical cities in the Yangtze River basin, including Jiujiang, Wuhu, Lu’an, Zhenjiang and Wuhan, this study investigated and summarized the characteristic variations and distribution differences of multiple indicators and substances from municipal sludge, dredged sludge, and river and lake sediments. The results demonstrated pH of multisource sludge was relatively stable in the neutral range. Organic matter and water content among municipal sludge were high and varied considerably between different wastewater treatment plants. Dredged sludge had an obviously higher sand content and wider particle distribution, which could be considered for graded utilization depending on its size. The nutrients composition of river and lake sediments was usually stable and special, with lower nitrogen and phosphorus content but higher potassium levels. The sources of heavy metals and persistent organic pollutants in multisource sludge were correlated, generally much higher among municipal sludge than dredged sludge and river and lake sediments, which were the most important limitation for final land utilization. Despite various properties of multisource sludge, the final fate and destination have some overall similarities, which need to be supplemented and improved by standards and laws. The study provided a preliminary analysis of suitable technical routes for municipal sludge, dredged sludge, river and lake sediments based on their different characteristics respectively, which was of great significance for multisource sludge co-treatment and disposal in the future of China.

农林废弃物共热解对污泥生物炭Cu(Ⅱ)吸附性能的影响

将山地城市污泥与水稻杆、水稻壳、桉树枝、桉树叶等农林废弃物进行共热解,研究共热解对生物炭理化性质及Cu(II)吸附性能的影响,探讨共热解对Cu(II)吸附性能的协同作用。结果显示,与污泥炭相比,水稻壳、水稻杆、桉树枝、桉树叶与污泥共热解制备的生物炭,C含量分别增大了0.64倍、0.87倍、1.04倍、1.22倍,O含量分别增大了1.11倍、1.25倍、2.01倍、2.17倍,对Cu(II)最大吸附量分别增大了28.4%,60.3%,82.7%,99.7%。共热解对生物炭Cu(II)吸附性能具有明显的协同作用,污泥与桉树叶共热解炭对Cu(II)最大吸附量的协同量化值最高(90.13%)。