Papers by Keyword: Sewage Sludge

Abstract: the treatment and disposal of sewage sludge is one of the hot spots in recent years, and the value of its energy utilization has gradually received attention by researchers. In this paper, the concept, yield, harm as well as the conventional disposal methods of sewage sludge are described, three kinds of main technologies of oil making from sewage sludge are introduced, including high temperature pyrolysis, low-temperature pyrolysis and direct thermo chemical liquefaction, and the research progress of these three technologies is reviewed.

Abstract: Microbial Fuel Cell (MFC) technology utilizes bacterial growth in carbon-containing substrates to generate electricity. For direct production of electricity, this MFC operates aerobically at the cathode and anaerobically at the anodes. This study tested the effect of glucose (10 %, 20 %, 30 %, 40 % and 50 % (w/w)), on the growth of bacteria, and then subsequent electricity production after 144 hours of the incubation period. Obvious substrate degradation rates (SDE) were detected in MFC fed with initial glucose concentration of 20 % (w/w) and 30 % (w/w) at 46.29 % and 40.27 %, respectively. The former generated 0.808 mW and the later was 0.736 mW. Glucose, being a basic component for growth of electrogenic bacteria influenced electricity generation. Higher the glucose concentration supplemented to the sludge, the more saturated the substrate was. Hence, inhibited the bacterial growth, and reduced electricity generation.

Abstract: The main objective of this study is to determine the basic characteristics of fluidization using sewage sludge particle as non-visual phenomena which can then be modeled physically and numerically with the program of Computational Fluid Dynamic (CFD). CFD modeling using Eulerian model incorporating the kinetic theory for solid particles was applied to the gas-solid flow at various superficial velocities for different particle sizes. The transfer momentum was calculated using Syamlal-O'Brien drag function and Eulerian multiphase model was used for analysis. Two-Dimensional computational domains discretized using rectangular cells (Quad), made within the 20 iteration steps of 0,001s. The gas velocity is found to be the ​​the most important factors that influence the formation process of fluidization; by increasing the rate of fluidization the bed expanse occurs higher as well the time of onset fluidization is shorter. The phenomenon can be explained well by modeling and simulation.

Abstract: Thermogravimetric analysis (TGA), coupled with Fourier transform infrared analysis (TG-FTIR) of sewage sludge was carried out to investigate the influence of moisture and oxygen on gas evolution during pyrolysis of sewage sludge. Wet sewage sludge with moisture of 86.47(wt. %) was collected from Shanghai, China. Wet sewage sludge and air dried sewage sludge were used in TG-FTIR analysis, while combustion (air flow) and pyrolysis (nitrogen flow) were separately introduced to achieve comparison. In condition of dry sewage sludge pyrolysis, there were two peaks representing release of separately moisture and volatile. Weight lost 85% in the temperature range of 25-600 °C while the main volatile matters were released before 600 °C. When air flow was introduced, a third peak of char combustion occurred. Wet sewage sludge made no much difference, except for the relatively outstanding peak of moisture release. Temperature regions for each stage were the same for wet and dry sewage sludge from TG curve. However, from the FTIR analysis, ammonia has two peaks between 50 and 450 °C in pyrolysis while ammonia has only one peak between 50 and 300°C.

Abstract: With Chinese continuous improvement of the urbanization and industrialization level, water pollution has becoming more and more serious, and the by-product —sludge has caught the focus of public attention. The total amount of sewage sludge produced in Beijing in 2010 is about 3,700t/d (wet base), 2,500t/d of which is from the urban area and 1,200t/d is from country side. Such a large amount of sludge with abundant water brought great difficulties to the subsequent processing. However, the cost of sludge treatment amounts to almost half of the sewage plant running cost while the consumption of drug covered more than half of the sludge treatment expenditure. Another aspect is that the water content of the dewatered sewage sludge is not stable, because of the variation of inlet amount and quality. Without knowing the relationship between the characteristics of sewage sludge and conditioning reagent, the operator just try to add more reagent, which in the end increase the cost of sludge treatment. Meanwhile, cationic polyacrylamide (C-PAM) is currently the most widely used sludge conditioning reagent. This research is to find out the relationship between the characteristics of sewage sludge and adding dosage of CPAM, which can be the first step to discuss how to adjust the conditioning reagent according to sewage sludge with different characteristics.Polyacrylamide (PAM) of different cationic (15%,35%,45%,60%), molecular weight (8 million, 10million, 12million) and dosage (2‰,3‰,4‰,5‰,6‰) are under testing in the experiment considering the index of capillary suction time (CST).Experimental material is the sludge from digestion tank in one of Beijing sewage plants. According to the experiment, it was found that the 8million-10million molecular weight, 4‰-6‰ adding dosage perform the best.

Abstract: To develop new clean energy has become an urgent task for many countries forced by the energy and environment crisis. To make biodiesel from sewage sludge is one of the solutions. In this study, biodiesel production from sewage sludge by in situ transesterification was discussed. The solvent is methanol and catalyst is sulfuric acid. In-situ transesterification, has many merits over conventional transesterification reaction such as it simply the procedure by skipping the step of lipid extraction and as a result cost can be saved. That is, the steps — sludge dissolved, lipid extraction and transesterification reactions — take place simultaneously. Methanol acts as an extraction solvent and as an esterification reagent as well. Experiments were conducted to determine the optimal parameters of in-situ transesterification for maximizing the yield of biodiesel, which are methanol to sludge mass ratio, acid concentration and temperature. The optimum synthesis condition was determined by orthogonal test L₁₆ (4³), and it was found that an optimum biodiesel yield can be obtained from sewage sludge by in-situ transesterification (16.6%) at methanol to sludge mass ratio 10:1(w/w), H₂SO₄ concentration 5% (v/v), and temperature 65°C. Temperature, H₂SO₄ concentration, and methanol to sludge mass ratio in sequence had significant influence on FAMEs yield. The FAMEs in the product were analyzed by GC-MS and the purity can be higher than 96%.

Abstract: This study aims to find out the optimum extraction time varied from 5 min to 60 min for extracellular polymeric substances (EPS) from sewage sludge pretreated at 80 °C. The change of the contents of EPS and its components under different time limit were recorded and compared. The results showed: the contents of soluble protein, TOC, soluble sugar and DNA was increased by 579.17 mg/l, 514.25 mg/l, 132.79 mg/l, and 34.69 mg/l, respectively, with the increase of thermal pre-treatment time during the process, and the DNA content increased the least, which indicating that the effect of thermal pre-treatment at 80 °C on cell lysis of sewage sludge was small. The EPS content, as a whole, was increased with the increase of thermal pre-treatment time. By analyzing the experimental data with the Analytic Hierarchy Process Model, which was used to identify the optimum thermal pre-treatment time of extracting EPS, the results showed that the effectiveness of EPS extraction from sludges was 30 min>60 min>50 min>20 min>40 min>10 min>5 min. Therefore, the 30 min was choosed as the optimum thermal pre-treatment time.

Abstract: The nitrogen conversion with attention to the intermediates and NOx precursors has been investigated during the primary pyrolysis of sewage sludge by using Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analyzer (TGA) coupled with Fourier transform infrared spectrometry (FTIR). The results indicated that 75.4% of total nitrogen exists in the forms of protein in the sewage sludge. Amine compounds and nitrogen heterocyclics were found to be the main nitrogenated intermediates during the pyrolysis process in the temperature range of 250-400 °C. As the dominant nitrogenated compounds, the relative proportions of amine compounds were above 52% in all cases. And since the decomposition of sewage sludge was promoted by high temperature, the relative proportion of amine compounds increased by 24.6% when the temperature raised from 300 to 400 °C. Moreover, the generation of NH₃ at 250 ^oC was mainly derived from the decomposition of ammonium salt, while the deamination of amine compounds led to a significant increase of NH₃ at 300 °C.

Abstract: Due to the foreseeable changes in the framework for bioenergy and especially for the use of energy crops, the organic waste and residuals becomes the focus of attention. Approximately two-third of the available total (organic) residue potential in Germany is already energetically used, whereby the thermal recovery with the use of waste wood preponderates. Approximately one-third of the total technical potential of biogas (including energy crops) consists of fermentable waste and residuals such as manure, industrial and municipal organic waste. The anaerobic digestion of biowaste and green waste also plays an increasingly major role in practice. The potential of agricultural residues as co-products (straw) and manure is slowly tapped for biogas production.

Abstract: Phosphorus is a necessary nutrient element to all lives in the world. Distribution and phosphate rock reserves in the world disclose shortage crisis of phosphorus. Thus phosphorus recovery has been a research hot spot in the world. Mr.Ohtake’ group [1] recommended a new method to recover phosphorus from sewage sludge during heating process. It seems that nearly 90% of the poly-phosphate (poly-P) and 87% of total phosphate (T-P) can be released from cultivated sludge by heating at 70 °C for 1 hour. Meanwhile, released poly-P can precipitate with Ca in neutral condition without any pH adjustment. Sewage sludge was used in this research to identify its performance during thermal treatment. With the increase of temperature and heating time, release of poly-P and T-P increased obviously. However, poly-P would be hydrolyzed when temperature was higher than 80 °C. With addition of EDTA, release of poly-P increased nearly 100%. Migration of metal cations during thermal treatment can provide indirect evidence which kinds of metal cations would make impediment on poly-P release. A novel phenomenon was observed poly-P mixed with ortho-phosphate can precipitate with NH₄⁺ and Mg²⁺ as struvite at pH 8.5.