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Municipal Sewage Sludge Drying Treatment by an Composite Modifier
Na Wei
Mathematical Problems in Engineering , 2012, DOI: 10.1155/2012/979764
Abstract: A sludge composite modifier (SCM) which comprises a mixture of three cementitious components was proposed for sludge drying and stabilization. Effect of SCM components on sludge moisture content was analyzed using uniform design and the optimum composition of SCM was determined by computer-aided modeling and optimization. To compare the drying effect of SCM, quicklime, and Portland cement, the effects of material content and curing time on moisture content of sludge were also studied. The results showed that the optimum ratio of modifier component was slag/cement clinker/dihydrate gypsum = 0.64/0.292/0.068 and the moisture content of SCM-stabilized sludge decreased with the increasing material content and extending curing time. Besides, the experimental results showed that optimized SCM behaved better than quicklime and Portland cement in sludge semi-drying and XRD analysis revealed that the main hydrated product of stabilization was ettringite, which played an important role in the effective drying process. Sewage sludge stabilized using SCM could be used as an effective landfill cover.
Microbiological Evaluation of the Effectiveness of Sewage Sludge Sanitization with Solar Drying Technology  [PDF]
Zbigniew Paluszak,Krzysztof Skowron,Ma?gorzata Sypu?a,Karolina Jadwiga Skowron
International Journal of Photoenergy , 2012, DOI: 10.1155/2012/341592
Abstract: The aim of study was to estimate the sanitization effectiveness of the sludge solar drying process carried out on technical scale in Poland based on the inactivation of bacteria and parasite eggs. Sewage sludge samples inoculated with Escherichia coli, Salmonella Senftenberg W775 and enterococci and perlon bags containing Ascaris suum eggs were placed inside the carriers fixed in the dried sludge pile and on the shovels and frame of the sludge turner. The number of reisolated microorganisms was determined with MPN method and the percentage of invasive A. suum eggs—with the microscope counting. On the basis of regression equations, the theoretical survivability and elimination rate of bacteria and parasite eggs were calculated. Experiment showed low hygienization efficiency of solar drying method. The theoretical survival time was 46–104 days in summer and 90–98 days in winter for S. Senftenberg W775 and, respectively 42–55 and 71–148 days for E. coli, depending on the carriers location. Enterococci were able to survive for 52–168 days in summer and in winter its number increased. The decrease in the percentage of invasive A. suum eggs was almost not observed. Results indicated that solar drying is a technology, which does not guarantee biosafety of product. 1. Introduction Growing effectiveness of sewage treatment technologies results in a considerable increase in generated sewage sludge [1]. The dry matter of stabilized municipal sewage sludge is expected to amount to 662,000?Mg in Poland in 2015. A considerable number of viruses, bacteria, and intestinal parasites may be present in sewage derived from hospitals, slaughter houses, and animal farms [2–5]. According to Bień [6], Sahlstr?m [7], Pepper et al. [8], and Sun et al. [9], bacteria of the genera: Salmonella (about 1,700 types), Shigella (4 species), Escherichia coli, Vibrio cholerae, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Clostridium perfringens, Bacillus anthracis, Listeria monocytogenes, Streptococcus faecalis, and Proteus vulgaris and viruses of the genera Enterovirus (67 types), Rotavirus, Parvovirus, and Adenovirus (31 types) are frequently isolated from sewage sludge. Of various methods of sewage treatment in Poland, those consisting in physicochemical processing, including drying, are developing dynamically. Conventional drying allows considerable reduction in the mass and volume of produced sludge, but it generates high costs resulting from the facility operation and causes a substantial emission of gaseous pollutions to the atmosphere. The unconventional, low-temperature
Feasibility analysis on drying and incineration of sewage sludge from a wastewater treatment plant

Li Bo,Wang Fei,Yan Jianhua,Chi Yong,

环境工程学报 , 2012,
Abstract: Experiments were carried out in a paddle sludge drying machine and a fluidized bed incinerator to analyze the feasibility of drying and incineration treatment of sewage sludge from Shaoxing Wastewater Treatment Plant (WTP).The sludge natures,as well as the contaminants emission during the treatment process were detected.Results show that,the sludge from Shaoxing WTP has similar characteristics with other sewage sludge,as the ash content is relativily high and the heating value is relativily low.The drying rate can reach up to 0.6 kg/(m2·min) in the small paddle drying machine and a drop of drying rate also appear during the process.The concentration of ammonia,which is the main pollution gas during the sludge drying process,can reach up to 170 mg/Nm3.The condensate from sludge drying process should be treated before discharge,as its COD can reach up to 820 mg/L.Sewage sludge from Shaoxing WTP would combust without any auxiliary fuel when its water content is lower than 30% after drying.The noxious gases and heavy metals in the flue gas should be taken seriously.The leaching toxicity of sludge incineration ash is below the national standard limits.
Dynamics of SO2 absorption by sewage sludge during drying

WENG Huanxin,FENG Xi,SU Minhu,ZHANG Jinjun,MA Xuewen,

环境科学学报 , 2010,
Abstract: Using the actual operating parameters of a contact-type sludge drying process, a simulation was conducted to study the dynamics of absorption of suffur dioxide (SO_2) from flue gas by sewage sludge during drying. The factors and causes leading to changes in the absorption rate were analyzed. The results show that the SO_2 absorptian rate decreased with increasing temperature and airflow. At 80℃, the SO_2 absorption rates of sludge with moisture contents of 55% and 75% , were 16.0% and 25.0% respectively. These rates were reduced to 6.0% and 7.0% , respectively, at 160℃. Absorption of SO2 by sludge occurs when SO_2 gas diffuses from the gas phase to the gas-liquid interlace, so elevating the drying temperature and increasing the airflow accelerate the evaporation of sludge water, thus hampering the process and causing the SO_2 absorption rate to drop. Increase of the SO_2 concentration in the flue gas had no obvious effect on SO_2 absorption rate. After absorption of SO_2 , the pH of the sludge dropped, indicating that acidic reactions had occurred. Infrared analysis of the sludge shows that absorption of SO2 by sludge is a chemical absorption process.
Study on the integration of vertical enhanced filtration and concentration and natural drying and digestion on sewage sludge

Jiang Wenchao,Zhang Zhi,Qu Zhenxiao,Hu Jian,Chen Bin,Yu Yiping,Jiang Futong,

环境工程学报 , 2008,
Abstract: In light of the existing problems of domestic sludge treatment and disposal, and in order to achieve the integration of concentration and digestion of sludge, a new type of reactor of integration of vertical enhanced filtration and concentration and natural drying and digestion on sewage sludge treatment was developed. Furthermore, the test was made on the sewage sludge treatment. The result shows that under the conditions of organic loading 0.8 kg VSS/(m3 ·d) , the average HRT 8.3 d, and sludge settled time 120 d, the organic removal rate comes up to 44.4%, and water content in sludge comes up to 79.1% with clear supernatant. Sludge digestion and concentration can be stimulated by each other. The filtrated liquid must be returned to sewage treatment plant for treatment.
Drying of municipal sewage sludge: from a laboratory scale batch indirect dryer to the paddle dryer
Arlabosse, P.;Chavez, S.;Prevot, C.;
Brazilian Journal of Chemical Engineering , 2005, DOI: 10.1590/S0104-66322005000200009
Abstract: among available technologies, disk and paddle dryers are often encountered in france to process municipal sewage sludge but their thermal design is still a question of know how rather than scientific knowledge. from experiments performed on an industrial naratherm? paddle dryer and the literature, a simple model has been developed. the dryer is divided into two parts depending on the sludge consistency. a constant evaporating flow rate is assumed in the pasty zone whereas its linear decrease with the moisture content is taken into account in the granular zone. to compute this model, some of the sludge properties have to be characterized with a set of laboratory scale experimental techniques. the agreement with the experimental data is good.
Experimental characterization of isothermal drying of dewatered sewage sludge particle

WEI Lihong,ZHANG Xiong,LI Rundong,WANG Lei,ZHENG Tao,

环境科学学报 , 2012,
Abstract: Three types of dewatered sludge with different particle sizes were dried at constant temperature of 65℃,85℃,105℃ and 125℃,respectively.The results showed that reducing sludge particle size or increasing the drying temperature had good effect on improving the drying rate of sludge.The drying rate of digested sludge was the highest,followed by biological aerated filter sludge and excess sludge.SEM analysis indicated that there were significant differences in the micro-morphologies of three types of sludge.Digested sludge had very rough surface and loose structure,while excess sludge had smooth surface and dense structure and biological aerated filter sludge had rough surface and less dense structure.There was a positive correlation between the surface roughness of sludge and the drying rate.
Experimental Research on Indirect Thermal Drying Process of Sewage Sludge

WANG Xing-run,JIN Yi-ying,WANG Zhi-yu,DU Xin,NIE Yong-feng,

环境科学 , 2007,
Abstract: Technical parameter, condensed steam water quality and flue gases were studied and organic compound hydrolysis mechanism was discussed. During experimental study, observed that the relationship between water content of sewage sludge and residence time have a negative exponential function. The condensed steam water has a high-concentration organic content. Total organic carbon (TOC), volatile fatty acid (VFA) and NH3 -N of the water were very high and the pH value was between 9 and 9.5. VFA and NH3 -N come from two sections: (1) In the 110 - 130 degrees C temperature range, hydrolysis of protein occurred with the formation of VFA and NH3 -N; and (2) In the 140 - 150 degrees C, fats hydrolyzed into VFA. There was no gaseous pollution produced in the whole experimental progress.
Drug-Resistant Microorganisms in Soils Fertilized with Sewage Sludge
Ewa Stańczyk-Mazanek , Teresa Nalewajek , Magdalena Zabochnicka
Archives of Environmental Protection , 2012, DOI: 10.2478/v10265-012-0008-6
Abstract: One of the methods of sewage sludge disposal, which is based on its fertilizing properties, is its use in nature, e.g. in farming (if all the permissible standards are met). However, the sludge used for soil fertilization might also contain heavy metals, pathogenic microorganisms, thus causing contamination in soil foundation and deterioration of the conditions for development of indigenous organisms. Particular threat is posed by the existence of drug-resistant microorganisms in sewage sludge. This problem has not been researched in detail yet. The authors of the present study aimed to determine qualitative changes in drug-resistant microorganisms in sandy soil fertilized with selected sewage sludge. Sewage sludge after different types of drying process (natural and solar) was added to the degraded sandy soil. The effect of the methods of sewage sludge drying on concentration of drug-resistant microorganisms in soil fertilized with the sludge was analysed. The study demonstrated that sewage sludge dried naturally in drying beds pose threat to soil environment and, potentially, to people and animals which have contact with fertilized soils. In sandy soils fertilized with these types of sewage sludge, pathogenic forms which exhibit resistance to first-line antibiotics can be found.
Biological Toxicity of Sewage Sludge Stabilized by Reed Bed on the Luminescent Bacteria  [PDF]
Jiangang Li, Yubo Cui, Wanjun Zhang, Yuying Dong, Shuran Jia
Journal of Geoscience and Environment Protection (GEP) , 2015, DOI: 10.4236/gep.2015.31001
Abstract: With the expanding scale of urban wastewater treatment, the resulting excess sludge quantity is also growing. Excess sludge treatment and disposal has become an important part of the sewage treatment. Sludge itself is rich in essential nutrients of plant growth such as nitrogen and phosphorus, so it’s a good organic fertilizer; but it often also contains harmful substances such as heavy metals. If the sludge treatment is not good, it not only can bring secondary pollution to the environment, but also can cause the waste of resources. Luminescent bacteria tests are conducted in this research by comparing the effects on the absorption and transformation of toxic substances between traditional sludge drying bed and reed bed. The study finds that the biological toxicity of surface layer sludge either in reed bed or in traditional drying bed has little change with the seasons and maintains in low level. While the biological toxicity in the bottom of sludge has change with the seasons and achieves the lowest level in summer and fall, and the biological toxicity of sludge in reed bed is lower than that of traditional drying bed.
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