WATER REMOVAL FROM SLUDGE IN A HORIZONTAL ELECTRIC FIELD

A new method for sludge dewatering was proposed, in which a horizontal electric field was applied in order to facilitate the dissipation of gases produced at electrodes and to keep the anode soaked in water during the dewatering process. The effects of operation conditions such as the magnitude of electric field strength, pH of aqueous phase, the pretreatment procedures including flocculation, freezing and heating on the water removal were examined, respectively. The morphological difference between the concentrated sludge produced by electrodewatering and by vacuum filtration was revealed with scanning electron microscopy, which shown that electrodewatering was effective in removing the capillary water in the sludge floc. At electric field strength of 1200 V/m, the sludge concentration could be increased from 3 to 8%(w/w), indicating that over 60% of water was removed from the sludge. Compared to those operated in a vertical electric field, the method described in the present study has the advantages in terms of high eficiency, simple structure and ease of operation.     

Abatement of Organic Pollutant Concentrations in Residual Treatment Sludges: A Review of Selected Treatment Technologies Including Drying

As a result of increasing population, industrialization, and effluent quality, sludge production has increased worldwide. Organic micropollutants in sludge have become a more critical environmental health concern compared to heavy metals. New sludge disposal regulations limit persistent organic pollutants (POPs) in addition to conventional organic indicators like total and dissolved organic carbon. This study aims at providing a brief review on POP concentration in the sludge in different regions of the world, sludge regulations, assessment of conventional biological sludge stabilization methods according to their ability to remove POPs, and discussions on alternative sludge treatment methods. The impact of sludge treatment unit operations including conditioning, thickening, mechanical and thermal dewatering, and biological and thermal stabilization on sludge management is also discussed in the context of organics. The occurrence and removal of micropollutants such as absorbable organic halogen compounds (AOX), nonylphenol and nonylphenol ethoxylates (NPE), di-2-(ethyl-hexyl)-phthalate (DEHP), dibenzo-p-dioxins and furans (PCDD/F), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) are also evaluated specifically for sludge treatment unit operations. A concise discussion is also included on different drying technologies suitable for drying of sludge.     

A NEW HIGH-INTENSITY ULTRASONIC TECHNOLOGY FOR FOOD DEHYDRATION

ABSTRACT

At present, there is a growing interest in the field of dehydration for preserving food. Ultrasonic energy represents a means to obtain dehydration without affecting the food. This paper deals with an experimental study about the use of high-intensity ultrasound for vegetable dehydration by using a new power ultrasound generator and a procedure in which ultrasonic vibrations are applied in direct contact with the product and under a certain static pressure. The drying effect of this new process is compared with that obtained from forced-air drying assisted by air-bome ultrasonic radiation and from a conventional hol-air drying. The results show that by using the new technology and procedure it is possible to reduce dramatically the treatment time and it is relatively easy to reach a final moisture content in the samples less than 1%. In addition, the product qualities are well preserved, the sample rehydration is higher than 70% and, because of the high efficiency of the new ultrasonic system employed, the energy consumption is low. As a consequence of the results a new technology for industrial applications is under development     

水热处理抗生素菌渣制备固体生物燃料

以生物超胶体形式存在的抗生素菌渣既是一种危害严重的环境污染物又是一种生物质资源,但因高含水且难以机械脱除而制约其处理和高效利用。借助水热技术,抗生素菌渣的沉淀、脱水及干燥性能得以显著改善,获得的固体生物燃料固含率和热值随水热处理温度和历时的增加而增大,但过于苛刻的水热条件易生成焦油甚至发生碳化。在优化的水热条件200℃、30～60 min下,固体生物燃料固含率52%～55%(质量分数,下同)、热值约14 MJ·kg^-1,固体回收率65%～75%。通过部分转化非凯氏有机氮(NKON)为凯氏有机氮(KON)并最终主要以氨氮(NH₄⁺-N)形式进入液相的迁移途径,菌渣中45%以上的氮在水热处理过程中被脱除。经水热无害化处理的抗生素菌渣液体产物的COD高于20×10⁴ mg·L^-1,具备良好的生物气生产潜力。水热技术被证实是针对包括抗生素菌渣在内的生物发酵制药过程残渣无害化处理和资源化利用预处理的有效技术。     

回归法预测片麻水层冻结井筒施工临界值的研究

针对采用帷幕冻结法井筒下部冰点位置难以精确估算而导致施工困难的问题,利用回归分析法从竖向和径向温度场变化规律分析,得出了冰点地层位置,确定了安全施工范围,简化了施工工艺,达到了井筒安全施工的目的,为淮南矿区冻结法施工井筒确定安全临界值提供了重要的参考依据。     

不锈钢冷轧废水站污泥脱水系统

介绍了采用板框压滤机处理不锈钢冷轧废水重金属污泥的工艺。设计泥量(以干污泥计)24 t/d,各水处理子系统的污泥,主要以含酸废水处理系统的污泥为主,泵入污泥浓缩池浓缩后,含固率8%～10%的污泥通过变频器控制的偏心单螺杆泵输送至板框压滤机。经过板框压滤机脱水后的泥饼含固率要求大于35%。系统自2007年9月初调试正常以来,运行良好,泥饼含固率稳定在35%以上。     

低阶煤干燥脱水技术的研究

介绍了转筒式干燥工艺、流化床干燥工艺、气流床干燥工艺等蒸发干燥工艺和热力脱水工艺（HTD）、机械热挤压脱水工艺（MTE）、UBC低阶煤干燥提质技术等非蒸发脱水工艺的工艺流程、技术特点及发展现状等。分析了低阶煤脱水工艺系统建设过程中干燥工艺、厂址、干燥介质与能源消耗的选择原则和依据。发现低阶煤干燥脱水工艺的选择应考虑目标用户对产品质量的要求,产品加工工艺对提质煤水分的要求且应尽量选择安全可靠、能耗较小、成本较低的干燥技术。厂址的选择需多方面综合考虑。干燥介质的选择应因地制宜,同时必须综合考虑干燥介质的成本及安全性。较低的干燥能耗才能够保证干燥工艺的长期运行,并产生经济价值。低阶煤干燥脱水技术的研究为低阶煤干燥工艺的选择及良好运行提供参考。     

低游离甲醛三聚氰胺甲醛树脂的合成

以三聚氰胺、甲醛、甲醇、过氧化氢为原料,合成了一种低游离甲醛三聚氰胺甲醛树脂。讨论了影响树脂中游离甲醛含量的因素。结果表明,当n(甲醛)∶n(三聚氰胺)=6,n(未反应甲醛)∶n(H2O2)=1∶1.1,在60~65℃羟甲基化反应60 min,使用脱水法合成的三聚氰胺甲醛树脂的游离甲醛含量为0.04%。     

LLL1150×600A离心脱水机在火烧铺矿选煤厂的应用

介绍了LLL1150×600A型立式过滤离心脱水机的工作原理、技术参数及几项主要技术特点:差速器采用整体结构,设置了专门的润滑用电动机,关键部件进行精加工和校正,采取了防堵措施;指出了生产中应注意的问题;实践证明,该离心机脱水产物水分低、脱水工艺指标良好、处理量大、性能稳定、工作可靠。     

Dewatering behaviour of water treatment sludges associated with contaminated site remediation in Antarctica

Sludge reduction and dewatering is an important aspect of water and waste water treatment. This is especially true in the case of Australia's Antarctic contaminated site remediation program, where the reduction in volume of wastes to be returned to Australia can lead to significant transport and handling cost savings. The dewatering characterisation of water treatment sludges from an Antarctic contaminated site was conducted using a theory of suspension dewatering developed by Buscall, Landman and White. This theory uses fundamental material properties of compressibility and permeability to determine the diffusivity of a suspension. Diffusivity is a useful property that can be used to directly compare the dewaterability of various sludges. In this investigation, several water treatment sludges were collected and characterised in the field to determine the impact of temperature and additives on compressibility, permeability and diffusivity. The Antarctic sludges were found to be less compressible and less permeable than materials such as mineral suspensions and alum water treatment sludges. Compressibility was found to decrease with the addition of powdered coagulation aids such as bentonite and chitosan.