Moisture Content Of Sludge Research Articles

Study on Sludge Characteristics of Lead and Zinc Smelting Acid and Sewage

Taking the lead and zinc smelting acid and sewage as the research object, the indicators of sludge moisture content, leaching concentration, corrosivity, phase, chemical composition, soluble salt dissolution rate were tested. The lead and zinc smelting acid and sewage was dried to different temperature, then the leaching toxicity and corrosivity of the original samples were measured, and the arsenic and selenium of the sludge was analyzed by the effects of leaching toxicity and corrosivity at different temperatures. The conclusions show that when lead and zinc sludge were mixed, with the temperature of 160 °C, the leaching concentrations of arsenic and selenium are lower than the leaching toxicity standard, and the pH value is between 2.5-12.5, which is lower than the corrosive standard.

Direct conversion of wet sewage sludge to carbon catalyst for sulfamethoxazole degradation through peroxymonosulfate activation

The high moisture content of wet sewage sludge generated from wastewater treatment process not only brings high cost of sewage disposal, but also limits its utilization as resource. In this study, an efficient strategy of directly utilizing wet sludge to develop advanced carbocatalyst via a hydrothermal coupled pyrolysis process was proposed. The possible application of as-synthesized carbocatalyst was evaluated by activating peroxymonosulfate (PMS) to degrade a model pollutant of sulfamethoxazole (SMX). Experimental results showed that about 100% of SMX and 59% of total organic carbon (TOC) could be removed within 15 min. Moisture content in wet sludge also affected the performances of as-obtained carbocatalysts. Further studies verified that singlet oxygen (1O2) dominated SMX degradation, which was generated in the process of PMS activation by CO groups on the surface of carbocatalyst. In the preliminary ecological test, a lower ecotoxicity of SMX degradation solution compared with the original solution was observed. This study demonstrated the feasibility of directly utilizing wet sludge for advanced carbocatalyst fabrication, which provided another solution for wet sludge treatment and utilization.

Hydrogen-rich syngas production via catalytic gasification of sewage sludge and wheat straw using corn stalk char-supported catalysts

The co-gasification of wheat straw and wet sewage sludge for hydrogen-rich gas production was investigated in a fixed bed reactor with corn stalk char (CSC)-supported catalysts. The Ni/CSC, Ni-Fe/CSC, and Ni-Fe-La/CSC catalysts were characterized via ultimate analysis, X-ray fluorescence, thermogravimetric, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopy analyses. A series of experiments were performed to explore the effects of reactor temperature, catalyst type, moisture content of wet sludge, and catalyst recycling performance on the composition and yield of gasification gases. The experiments demonstrated that the nickel-iron alloy (Fe0.64Ni0.36) was detected in the Ni-Fe-La/CSC catalyst, and the Ni-Fe-La/CSC catalyst showed much higher hydrogen production compared with the Ni/CSC and Ni-Fe/CSC catalysts. Furthermore, La2O3 effectively maintained the catalytic performance of the catalyst by relieving carbon deposition. Compared with non-catalyst biomass gasification, H2 yield increased from 3.80 mol/kg to 11.96 mol/kg using Ni-Fe-La/CSC catalyst at 600 °C. The newly developed tri-metallic Ni-Fe-La/CSC catalyst exhibited high catalytic activity for biomass gasification at low temperature.

Electro-dewatering of sewage sludge: Effect of near-anode sludge modification with different dosages of calcium oxide

The efficiency of common sludge electro-dewatering (EDW) is restrained by the following issues: 1, the near-anode sludge dries out quickly, causing a rapid increase in electrical resistance; 2, the pH at anode decreases by the accumulation of H+ from the electrolysis of moisture, resulting in a decrease in Zeta potential (ζ). Alleviating the negative impact of these problems is the key to improving the dewatering efficiency of EDW. Therefore, in this study, calcium oxide (CaO) was used for near-anode sludge modification to increase its pH and electrical conductivity. With increasing CaO dosage, pH rose from 6.0 to 12.2, electrical conductivity increased from 368 ± 16 μS/cm to 6285 ± 21 μS/cm and the ζ declined from −15.3 ± 0.6 mV to −8.8 ± 0.4 mV. The EDW tests were conducted at 30 V and 25.5 kPa. The results indicate near-anode sludge modification with CaO weighing 3%–5% mass of raw sludge (mu(RS)) improved the EDW effect, while the energy consumption increased slightly. When 3%–5% mu(RS) of CaO was added, the final moisture content of sludge was 54.5%–44.3%, below that of the blank group (no CaO added), which was 57.9%; the time to obtain target moisture content (60%) was 910 s–590 s, lower than the blank group's 1060 s; and the energy consumption to obtain target moisture content was 0.233 kW h/kg H2O–0.271 kW h/kg H2O, higher than the blank group's 0.157 kW h/kg H2O. A quantitative criterion (KsiEDW) was adopted to assess the feasibility of EDW. Economically and energetically, the experiment with 4% mu(RS) of CaO added for near-anode modification was the optimal condition in this research, due to its second smallest KsiEDW, the best sludge reduction effect (67.2%), lower final moisture content (46.2%) and less time (640 s) to obtain target moisture content. The results show some mechanisms of EDW and provide experience for practical application.

Secondary energy component in energy-saving processes of cement production

Problems of energy saving in the firing of raw sludge is an important factor in the long-term development of cement production. An integrated approach to the study of the properties of raw materials and additives makes it possible to find ways to save fuel and energy resources. Reducing the moisture content in the sludge by the use of plasticizing reagents is one way to solve the problem of reducing energy consumption during firing of sludge. Reducing the moisture content of raw sludge from 41% to 35.5% makes it possible to reduce energy consumption by 23.3 kilograms of equivalent fuel per ton of clinker. The most effective type and concentration of plasticizing reagent was selected. A decrease in the moisture content and an increase in flowability were studied on a model raw sludge based on kaolinite-montmorillonite clay, chalk and pyrite cinder – a coal -alkaline reagent (0.1 wt.%). The studied reagents were arranged in the following sequence according to the effectiveness of increasing the flowability of sludge: coal-alkaline reagent, Polyplast SP-1, calcium lignosulfonate (LST), Viscocrete20HE, Linamix PK.

Experimental investigation on sludge dewatering using granulated blast furnace slag as skeleton material.

The highly compressible nature of sludge and the presence of colloidal particles cause difficulties in sludge dewatering. Reducing the moisture content in secondary sludge is a key factor in reducing the capital costs, operational costs, and transportation costs in wastewater management. This investigation concerned the combined utilization of quicklime and granulated blast furnace slag (GBFS) to improve sludge dewatering. The experimental work included the initial characterization of the sludge and granulated blast furnace slag and evaluation of the dewatering ability of the treated sludge (CST, moisture content, turbidity, zeta potential, and heavy metal and biopolymer contents). Optimization using the Box-Behnken design (BBD) was carried out with various operational parameters, and the best performance was found to be at a pH of 10.2, a dose of 0.34g/g DS, and a contact time of 14min. A characterization study was carried out by scanning electron microscopy (SEM) in conjunction with EDS, X-ray diffractometry (XRD), and Fourier transform infrared spectroscopy (FTIR) to confirm the structural features (dense), elemental composition, and the presence of different functional groups. Hence, this study concluded that the use of quicklime with granulated blast furnace slag is suitable for conditioning during sludge dewatering. Graphical abstract.

Protein extraction from excess sludge by alkali-thermal hydrolysis.

The protein in excess sludge can be extracted effectively by the alkali-thermal method, and the extracted protein can be used as a foaming agent and in other industrial raw materials to realize its resource utilization. In this paper, the factors influencing sludge protein extraction by the alkali-thermal method were optimized based on the protein extraction rate and the polypeptide content, which determine the foaming performance of the extracted protein. The results showed that the optimal conditions were a pH of 12, a temperature of 120°C, a reaction time of 4h, and a sludge moisture content of 92%. Under these optimized conditions, the extraction rate of protein and the concentration of polypeptides were 88.3% and 6599mg/L, respectively. Additionally, the foaming performance of the extracted protein solution was tested, and the foamability and foam stability were close to 450% and 88.8%, respectively. Therefore, the sludge protein extracted by the alkali-thermal method can meet the relevant standards of foam extinguishing agents and concrete foaming agents in China. In addition, the dewatering performance of the hydrolyzed sludge was improved by 93.1%, which provided favorable conditions for the subsequent separation of the protein solution.

Numerical simulation of co-incineration of sewage sludge and municipal solid waste in municipal solid waste incinerator

Incineration is widely used as an important method of sludge and garbage utilization and harmless treatment. The simulations of co-incineration of sludge and municipal solid waste are conducted by computational fluid dynamics method(CFD) in a MSW incinerator. The study focuses on the effect of mixing proportion, moisture content of sludge, excess air coefficient and primary and secondary air distribution ratio on the combustion progress. Simulation results indicate that the combustion temperature of furnace decreases rapidly with the increase of the mixing proportion and moisture content of sludge, which is mainly because the moisture content of sludge is higher than that of MSW as well as its low calorific value. As a result, it is recommended that the water content and mixing ratio of sludge would be controlled below 40% and 7% respectively. Therefore, the fresh sludge should be dried before entering the furnace.

Feasibility Study of Shell Powder as Sludge Conditioning Agent

Sludge becomes a “world problem” with the increase of wastewater treatment amounts across the world. Sludge treatment is mainly for reduction, stabilization, harmlessness and recycling. By adding sludge conditioning agents, it can effectively reduce the moisture content and the specific resistance of sludge, and provide effective guarantees for subsequent sludge dewatering. The shells were used to reduce the moisture content and specific resistance of sludge herein. Through the analysis of experimental data, the results showed that the best dosage of shell powder solution was 6% of the dry weight of the sludge, and the best dosage of shell powder was 24% of the dry weight of the sludge. Under the optimal dosage, changing the pH value could also cause changes in the water content and the specific resistance of the sludge. The optimal pH values of the shell powder solution and shell powder for sludge conditioning were 8-9 and 7, respectively.

Improvement of the sludge flocculation dewatering efficient by electromagnetic wave loading: research based on removal of bound water.

Excess sludge was loaded by 2450MHz electromagnetic wave in this study. The mechanism of electromagnetic wave loading on the releasing of bound water before sludge flocculation dewatering was investigated through observing the changes of extracellular polymeric substances (EPS) composition, surface charge, and particle size distribution. The results showed that the 8.55g/g total suspended solids (TSS) of bound water was reduced with 160J/mL electromagnetic wave, and the moisture content of sludge decreased by 3.02%. The EPS structure in the sludge floc matrix was destroyed and the LB-EPS content reduced. Simultaneously, infrared spectrum analysis indicated that bound water content was correlated both to the changes of hydrophilic and hydrophobic functional groups. Moreover, protein secondary structure analysis found that looser protein structure facilitated the exposure of internal hydrophobic groups and further promoted the sludge hydrophobic properties. Additionally, electromagnetic wave disintegrated colloidal stability through dipole motion. The zeta potential increased from - 25.57 to - 14.32mV; the medium particle size (d0.5) decreased from 119.99 to 80.41μm. More small molecules created in the supernatant were helpful to release bound water, which could further improve flocculation dewaterability of sludge with electromagnetic wave loading.

Investigation of filtration properties and microbiological characteristics of sewage sludge after physical conditioning with the use of ground walnut shells

In this research, ground walnut shells were used in order to improve the sewage sludge treatment. The influence of walnut shells on capillary suction time (CST); the sludge moisture content (MC), bound water (BW), the specific resistance to filtration (SRF) as well as the total bacteria number was investigated. The results have shown that the addition of ground walnut shells into sewage sludge affected the reduction of total bacteria count and the improvement of sewage sludge dewaterability. The addition of ground walnut shells in the amount of approximately 200% of sewage sludge dry mass (DS) decreased the MC by 66%, CST by 68% and SRF by 64%. The total bacteria number was reduced by approximately 88% after physical conditioning with the use of walnut shells in a dosage of 200% DS. It was proved that walnut shells might be considered as a material assisting the sewage sludge treatment.

Feasibility Analysis of Drying Sludge Using Flue Gas Waste Heat

Using sewage sludge as fuel has been considered an effective way to handle the sludge. However, due to the high water content, sludge is required to be dried before it can be burnt. In this paper, a paddle sewage sludge dryer was proposed to add after bag house gas filter (BHF) and before flue gas quench (FGQ), which can use the waste heat of the flue gas (FG) and therefore, improve the overall efficiency of the biomass-based plant and sludge handling. A mathematical model was developed to simulate the heat transfer in the paddle dryer, which was validated through the comparison with measured data. Based on this model, the impacts of flow rate of sludge and stirrer speed on the moisture content of exit sludge, temperature of exit sludge were studied. The results show that the increase of stirrer speed or the decrease of sludge mass flow rate all can reduce the moisture content of exit sludge.

Extraction of protein from excess sludge by thermal pretreatment assisted enzymatic hydrolysis

In this paper, the hydrolysis conditions to extract protein from excess sludge by thermal pretreatment assisted enzymatic were studied. The optimum technological conditions were the sludge moisture content of 95%, thermal pretreatment temperature of 100 °C, heating time of 3h, initial pH of enzymolysis sludge of 11, enzyme dosage of 3000U/g dry sludge, enzymolysis temperature of 55°C and time of 3h. Up to 52.8% of the protein content of the sludge was extracted, and the dehydration performance of the hydrolyzed sludge was 87.46% higher than that of the original sludge. Therefore, thermal pretreatment-assisted enzymolysis can effectively extract protein from excess sludge and improve its dewatering performance.

Свойства материалов для перспективной технологии совместной утилизации техногенных отходов

With the aim of improving the technology of co-processing of red mud (RM) and oily mill scale free (OMS) using co-temporal methods and apparatus, including using equipment of the center «Ural-M», studied the physico-chemical properties of industrial wastes. The main components of RM are: Fe (35.7%) in the form of hematite and complex hydroalumination, Ca (11.0%) in the form of calcite and hydro-aluminosilicates, Al (6.8%) and Si (4.7%) in the composition of hydroalumination, Na (2.8%) in the form of hydroalumination, carbonate and hydroxide, Ti (2.5%) in the form of rutile. The sludge moisture content was 11.9%. The main components of the OMS are: Fe (71%) in the form of magnetite, wustite and hematite with a very small amount of fayalite. The contents of Si (in the form of quartz), Al and P (non-forming phases) are within 1-3%. Humidity OMS – 16.3%, the content of indelible organic matter – 4.0%. Granulometric composition of RM is characterized by high dispersion. With an average diameter of 1.6 µm, all particle sizes are in the range of 0.5-12 µm. Granulometric composition of OMS is characterized by complexity. With an average diameter of 8.6 µm, maxima of 0.9 µm and 15 µm and a minimum of about 1.2 µm are observed in the particle size distribution. The specific surface area of the materials is equal to RM 23.7 m2/g, and OMS – 1.9 m2/g. The change of waste properties after exposure to aqueous solutions of alkalis and acids neutralizing the effect of organic (OMS) and alkaline (RM) surface compounds was studied. Neutralization of aqueous sus¬pension with HCl solution leads to removal of alkaline film from the surface. As a result of the impact of reagents, there is a decrease in the content of water-soluble components in the processing products. At the same time, the average particle sizes of RM and OMS increase to 2 and 14 µm, respectively, and the specific surface area to 25.7 and 2.3 m2/g. The distribution of particle size of RM is almost constant, and the OMS is approximately 5 and 10% of the smoothed maximum and minimum in the area of at least 0.5 and 15 µm.

Meso-mechanism of mechanical dewatering of municipal sludge based on low-field nuclear magnetic resonance

Both huge volume and high moisture content of municipal sludge have brought great troubles and attracted extensive concerns in the world. In this paper, the mechanical press filtration (MPF) dewatering was performed under ultrahigh pressure in order to improve the dewatering performance of municipal sludge. Low-Field Nuclear Magnetic Resonance (NMR) technique was used to study the effect of MPF parameters on dewatering performance. Based on the pore characteristics of municipal sludge, a capillary bundle model was developed to explore the mesoscopic mechanisms of MPF dewatering. The results indicate that moisture content of sludge cake decreases gradually with the increase of compressed pressure and dewatering time as well as the decrease of sludge weight , and the moisture content of municipal sludge can be reduced to as low as 30% with MPF dewatering. According to the peak and envelope area of relaxation time curve in NMR, it can be found that the size of pores decreases and the percentage of small pores increases during the dewatering process. Therefore, the capillary water cannot be removed by MPF method because the capillary pressure in very small pores increases evidently. Furthermore, the compaction degree of the outmost layer is generally higher than that of the middle layer, and the difference of moisture content between the middle and outmost layers of cake is 25%–28.4%. The present work may be helpful to understand the MPF dewatering mechanism and shed light on the new dewatering techniques of municipal sludge.

Optimization of a hybrid sludge drying system with flush drying and microwave drying technology

The purpose of this study is to optimize a hybrid sludge drying system using a primary cold flush drying system and a secondary microwave drying system filled with a heating material. The system also includes an odor reduction facility to remove the complex odors generated from sludge drying. Through operating the system, the final dry sludge moisture content was reduced to an average of 15.8%. The energy consumption was 711.6kcalkg−1. The advantage of this system is that it can achieve high efficiency sludge drying with low energy consumption, and it can apply a complex heating technology to each drying section, depending on the physical properties and operating conditions of the target material to be dried. Therefore, this system is expected to achieve a high drying efficiency while simultaneously reducing the energy and processing costs in future sludge drying processes.

A new method to characterize sludge stickiness during drying: Effects of sludge temperature and calcium oxide (CaO) on stickiness

Stickiness is a phenomenon widely observed in drying practices of sewage sludge. This work is aimed at demonstrating the effects of sludge temperature (30–70 °C) and calcium oxide (CaO) on the stickiness of two municipal sewage sludges, based on a newly designed device which can conveniently and systematically determine the temperature-dependent variables of tensile stress (adhesion), shear stress (adhesion) and compression stress (cohesion), respectively. The results indicated that both sludges showed the highest stickiness in the moisture range of 0.43–1.50 kg H2O kg−1 DS (dried sludge). In sticky region, the compression stress was an order of magnitude higher than the shear stress, while the shear stress was about 1–4 times higher than the tensile stress. Furthermore, CaO addition (3 wt.%) led to the increase of the tensile stress, shear stress and compression stress, partially owing to the increased release of organic components (protein, polysaccharides (PSC) and total organic carbon (TOC)) from sludge. However, despite of the increased release of organic components, marked decrease of the above-mentioned stresses was observed when sludge temperature increased from 30 °C to 70 °C, indicating that the temperature-induced changes of sludge rigidity and liquid tension played more important roles in sludge stickiness than organics release. The results of the analysis of variance (ANOVA) indicated that the moisture content of the sewage sludge showed the most significant influence on the tensile stress, shear stress and compression stress, compared with that of the temperature and CaO.

Preparation of high surface area sludge-based activated hydrochar via hydrothermal carbonization and application in the removal of basic dye

Conventional methods to produce sludge activated carbon require high-energy due to high moisture content and poor dewaterability of the wet sludge. Recently hydrothermal carbonization (HTC) has been emerged as a promising thermo-chemical wet biowaste conversion technology for the valorization by converting these precursors into high value-added products such as a nanostructured carbon. In this study, sludge-based activated hydrochars (SAC) were prepared from high moisture content (88.9%) wastewater sludge (without pre drying) via HTC followed by physical (P-SAC) and chemical (C-SAC) activation with CO2 and KOH, respectively. Further, the effects of HTC temperatures (170, 200, 230 and 260 °C) and the activation methods on the physicochemical characteristics of hydrochar and SACs were investigated through ultimate analysis (CHNO), SEM, BET, BJH, FT-IR, Boehm back titration and zeta potential. The result showed that KOH-activation at 700 °C could significantly enhance the surface area of hydrochars (from 6.3 to 1613.9 m2/g) compared with CO2-activation even at 900 °C (261.6 m2/g). The mesopore P-SAC prepared from hydrochar at lower HTC temperature due to the presence of ash content. While, the negatively charged microspores C-SAC (VTotal: 0.88 cm3/g and Vmicro/VTotal: 73.3%) with high SBET was synthesized at higher HTC temperature. Prepared hydrochars were applied for the removal of a basic dye (such as methylene blue, MB) from aqueous solution. Based on Langmuir isotherm model (R2>99.4%), the maximum monolayer MB adsorption capacity of hydrochar, P-SAC and C-SAC were 63.3, 122.4, and 588.2 mg/g, respectively at pH > 8.0. The MB adsorption on C-SACs followed the pseudo-second-order kinetic model and a spontaneous endothermic reaction from 298 to 328 K. The commercial ACs also was compared with our materials and found that produced activated hydrochars showed superior results for MB removal. Therefore, HTC can be the potential carbonization method for wet biomass conversion to valuable carbonaceous material in a cost-effective way.

Convective drying of sawdust-sludge mixtures: The effect of the sludge matrix

Thermal drying is an important treatment method for sewage sludge. Sludges from Oupeye, Grosses Battes, and Embourg wastewater treatment plants (WWTPs) were chosen for study. The effect of the mass fraction of sawdust (10%, 20%, 30%, and 40%) on sludge drying in a fixed bed dryer was investigated. A universal testing machine was used to determine the stiffness of the samples. X-ray tomography was employed to measure the structural properties of sample beds including the volume, total exchange surface, and void fraction. Both a lower moisture content of sludge and a higher mass fraction of sawdust lead to higher stiffness. The initial void fraction, bed volume, and total exchange surface of the sample bed are all related to sludge matrix and sawdust addition; however, the maximum drying rate is proportional to the initial total exchange surface, which is independent of the sludge matrix. This proves that sawdust addition is a positive means of sludge drying because of the increase in the initial total exchange surface.

МАТЕМАТИЧЕСКОЕ МОДЕЛИРОВАНИЕ СОВМЕСТНОЙ КОНВЕРСИИ УГЛЯ И ШЛАМА СТОЧНЫХ ВОД В ОБРАЩЕННОМ СЛОЕВОМ ГАЗОГЕНЕРАТОРЕ

Актуальность исследования обусловлена необходимостью утилизации бытовых и промышленных отходов. Утилизация горючих отходов, таких как шламы сточных вод, может быть совмещена с производством энергии для небольших потребителей. Одним из способов такой утилизации может стать газификация, позволяющая получить горючий газ, пригодный для получения тепловой и электрической энергии. Цель: на основании результатов математического моделирования оценить эффективность совместной конверсии шлама с более качественным топливом (бурым углем) при разных условиях проведения процесса (коэффициент избытка окислителя, состав топливной смеси, начальная влажность шлама сточных вод); оценить допустимую долю шлама в смеси с углем. Объект: процесс обращенной слоевой газификации смесей бурого угля и шлама сточных вод. Метод: математическое моделирование процесса слоевой термохимической конверсии твердых топлив с помощью разработанной ранее автором стационарной одномерной модели. Результаты. Построены расчетные зависимости характеристик процесса газификации (химический КПД, состав и калорийность газа) от удельного расхода дутья, отношения уголь/шлам (0–100 %) и начальной влажности шлама (10–40 %). Определены максимальные значения доли шлама в смеси с углем при фиксированном на уровне 60–70 % химическом КПД и максимальные значения химического КПД при фиксированной на уровне 20–30 % доле шлама в смеси с углем (для того чтобы избежать спекания слоя). При влажности шлама 40 % его максимальная доля в смеси с углем может достигать 50 % (при исключении спекания). Влага, содержащаяся в шламе, испаряется и выступает в качестве дополнительного газифицирующего агента. При ограничении доли шлама в смеси с углем на уровне 20–30 % эффективность газификации падает незначительно по сравнению с углем без добавок шлама.