Sludge Characteristics Research Articles

Application of Encapsulated Quorum Quenching Strain Acinetobacter pittii HITSZ001 to a Membrane Bioreactor for Biofouling Control

Quorum quenching (QQ) is a novel anti-biofouling strategy for membrane bioreactors (MBRs) used in wastewater treatment. However, actual operation of QQ-MBR systems for wastewater treatment needs to be systematically studied to evaluate the comprehensive effects of QQ on wastewater treatment engineering applications. In this study, a novel QQ strain, Acinetobacter pittii HITSZ001, was encapsulated and applied to a MBR system to evaluate the effects of this organism on real wastewater treatment. To verify the effectiveness of immobilized QQ beads in the MBR system, we examined the MBR effluent quality and sludge characteristics. We also measured the extracellular polymeric substances (EPS) and soluble microbial products (SMP) in the system to determine the effects of the organism on membrane biofouling inhibition. Additionally, changes in microbial communities in the system were analyzed by high-throughput sequencing. The results indicated that Acinetobacter pittii HITSZ001 is a promising strain for biofouling reduction in MBRs treating real wastewater, and that immobilization does not affect the biofouling control potential of QQ bacteria.

Characterization of Sludge Resulting from Chemical Coagulation and Electrocoagulation of Pumping Water from Fishmeal Factories

In the fishmeal industry, seawater is used to transport fish to the factories. Due to this, “pumping water” with high concentrations of organic matter is generated that is treated via chemical coagulation before letting it into the sea. The objective of this study is to characterize and compare the sludge obtained from conventional chemical coagulation and the sludge from the electrocoagulation process. A pilot electrocoagulation plant was built next to a chemical coagulation plant. The sludge obtained from both methodologies was analyzed for its proximal composition, its iron and aluminum content, and the fatty acid profile in its contained fat. Electrocoagulation was found to produce sludge with a higher concentration of lipids and ash, which indirectly confirmed that it removes more organic pollutants and salts than chemical coagulation. The contents of aluminum and iron in the sludge obtained by electrocoagulation were 4.2% and 0.025%, respectively, while those in the sludge obtained from chemical coagulation were 0.01% and 4.8%, respectively. Aluminum comes from the sacrificial electrode of the electrocoagulation tank, while iron comes from the salts used in chemical coagulation. The sum of w-3 fatty acid values (EPA + DHA) was 12.5% and 18.8% for sludges from the electrocoagulation and chemical coagulation processes, respectively, so we can assume that electrocoagulation is a more oxidizing process than chemical coagulation. Due to their high organic load, both sludges must be assessed as an alternative feed ingredient.

Co-Gasification Synergistic Characteristics of Sewage Sludge and High-Sodium Coal.

A comprehensive study was conducted to assess the co-gasification characteristics of sewage sludge and high-sodium coal. As the gasification temperature increased, the CO2 concentration was decreased, and the concentrations of CO and H2 were increased, while the change of CH4 concentration was not obvious. As the coal blending ratio increased, the H2 and CO concentrations initially increased and then decreased, while the CO2 concentration initially decreased and then increased. The mixture of sewage sludge and high-sodium coal shows the synergistic effect of co-gasification, and the synergistic effect was to promote the gasification reaction positively. The average activation energies of co-gasification reactions were calculated by the OFW method, and the average activation energy initially decreases and then increases as the coal blending ratio increases. Both fluidized-bed gasification and thermogravimetric analyzer gasification show that the optimum coal blending ratio is 0.6. Overall, these results provide a theoretical basis for the industrial application of sewage sludge and high-sodium coal co-gasification.

Co-gasification of municipal sewage sludge and cotton stalk enhanced by metal-enriched texture dyeing sludge additives for syngas production

In this study, co-gasification characteristics of municipal sewage sludge (MSS) and cotton stalk (CS) for syngas production enhanced by using metal-rich texture dyeing sludge (TDS) pyrolysis residues as additives wereinvestigated in a TGA and a fixed bed reactor. Kinetic analysis results showed that the addition of TDS residue prepared at 600 °C (TDS-600) resulted in the reduction of activation energy of MSS/CS co-pyrolysis to the maximum extent. The syngas yield greatly increased with the rising temperature and steam volume fraction (fH2O). However, the excessive steam at high temperature may lead to the decrease of syngas yield due to the gas expansion effect. The maximum syngas yield of 0.808 m3/kg could be obtained at an optimal gasification temperature of 850 °C and a fH2O of 20 %. In the co-gasification of MSS and CS, the syngas yield increased from 0.683 without TDS-600 to 0.903 kJ/mol with 20 % TDS-600 and the tar content decreased from 40.15 % to 26.45 %, suggesting the outstanding catalytic effect of TDS-600 on promoting syngas yield and tar decomposition. The possible ecological risk of heavy metals in ashes after co-gasification was evaluated by the potential ecological risk index (RI). The calculated RI values of all samples were <50, demonstrating the safe application of ashes in agriculture industry.

Comparison of Carbon Emissions in Different Treatment and Disposal Process Routes of Municipal Sludge

With the introduction of the goal of carbon neutrality, the efficient resource recycling of municipal sludge has been given increasing attention. In order to scientifically evaluate the routes of sludge treatment and disposal from the perspective of carbon emissions, four typical routes were chosen for accounting the carbon emissions per ton for dry sludge (DS). Based on the Intergovernmental Panel on Climate Change (IPCC), combined with Chinese sludge characteristics, carbon emissions were divided into three types:the direct emissions, indirect emissions, and carbon offsets, and accounting boundaries were initiated at sludge thickening and ended at products or energies. The results showed that the total carbon emission of R4 (gravity thickening+thermal hydrolysis+anaerobic digestion+plate and frame filter pressing+transportation+land utilization) was 99.41 kg·t-1(calculated as CO2/DS, same below), which was the route with lowest carbon emissions. If the fugitive emission of CH4 from anaerobic digestion was avoided, the route (R4) could achieve carbon neutrality at this stage. Process units with larger carbon emissions should focus on optimization to reduce the carbon emissions, such as through thermal drying (1049.24 kg·t-1), deep dewatering (960.99 kg·t-1), sanitary landfill (786.24 kg·t-1), incineration (635.52 kg·t-1), aerobic composting (614.17 kg·t-1), and thermal hydrolysis (544.67 kg·t-1). The main carbon offsets were the incineration power generation (-1440.29 kg·t-1), CH4 collection of anaerobic digestion (-435.06 kg·t-1), land utilization (-415.83 kg·t-1), and building materials utilization (-169.75 kg·t-1). In summary, "anaerobic digestion and land utilization" has a great potential for carbon offsets, which should be advocated for as the widely used treatment.

Performance evaluation of submerged membrane bioreactor for municipal wastewater treatment: Experimental study and model validation with GPS‐X software simulator

AbstractIn this study, flat sheet submerged MBR (FS‐SMBR) was investigated under 6 and 4 h hydraulic retention times (HRT) and 40 days solid retention time with real municipal wastewater. The implementation of the treatment system was evaluated in terms of physico‐chemical and microbial analysis as well as sludge characterization. The permeate of FS‐SMBR complied with the standards for reuse and non‐detectable levels of faecal coliform was achieved at 6 and 4 h HRTs, with pore‐blocking resistances (Rt) of 28 × 1011 and 40 × 1011/m, respectively. Examining another dominant factor, that is, sludge viscosity, the best results were acquired using HRT 4 h for domestic wastewater. Furthermore, the results obtained were validated and calibrated using the GPS‐X software simulator, and the results of modelled data were completely matched with the experimental data under the same conditions.

Implementation of an anaerobic selector step for the densification of activated sludge treating high-salinity petrochemical wastewater.

Sludge bulking is a common challenge in industrial biological wastewater treatment. Leading to difficulties such as bad sludge settling and washout, which is a problem also encountered in the petrochemical industry. Anaerobic feeding strategies can be used to induce the growth of storage-capable organisms, such as glycogen-accumulating organisms (GAO), leading to denser sludge flocs and better settling. In this study, the implementation of an anaerobic feeding strategy was investigated for high-salinity petrochemical wastewater (±35 g salts·L-1), using a sequencing batch reactor. Influent, effluent and sludge characteristics were analyzed throughout the operational period, which can be divided into three stages: I (normal operation), II (increased influent volume) and III (longer anaerobic mixing). Good effluent quality was observed during all stages with effluent chemical oxygen demand (COD) < 100 mgO2·L-1 and removal efficiencies of 95%. After 140 days, the sludge volume index decreased below 100 mL·g-1 reaching the threshold of good settling sludge. Sludge morphology clearly improved, with dense sludge flocs and less filaments being present. A maximum anaerobic dissolved oxygen carbon (DOC) uptake was achieved on day 80 with 74% during stage III. 16S rRNA amplicon sequencing showed the presence of GAOs, with increasing relative read abundance over time from 1 to 3.5%.

Impact of Irrigation with Contaminated Water on Heavy Metal Bioaccumulation in Water Chestnut (Trapa natans L.)

This study investigated the monitoring of six heavy metals (Cd, Cr, Cu, Fe, Mn, and Zn) in pond water, sludge, and cultivated water chestnut (Trapa natans L.) crops in Saharanpur district of Uttar Pradesh, India. For this purpose, samples of pond water, sludge, and T. natans plant (nut, shoot, and root) were collected in November of 2021 and 2022 from three zones (Zone 1: agricultural area irrigated with borewell water, Zone 2: urban area irrigated with municipal wastewater, and Zone 3: rural area irrigated with mixed type of wastewater) and subsequently analyzed for heavy metal concentration using atomic absorption spectroscopy. The results showed that the physicochemical and heavy metal characteristics of pond water and sludge were significantly (p &lt; 0.05) higher in Zone 2 and 3 than to those in Zone 1. The concentration of heavy metals in T. natans root was comparatively high followed by shoot and nut parts. The bioaccumulation factor (BAF) was maximum while using pond water as a reference medium compared to pond sludge. Overall, the increasing order of heavy metals in T. natans was observed as Cd &lt; Cr &lt; Cu &lt; Zn &lt; Mn &lt; Fe. In the edible part (nut) of T. natans, the average contents of Cd (0.005 ± 0.002 mg/kg), Cr (0.134 ± 0.009 mg/kg), Cu (1.043 ± 0.104 mg/kg), Fe (9.589 ± 0.957 mg/kg), Mn (4.326 ± 0.753 mg/kg), and Zn (1.540 ± 0.537 mg/kg) were comparatively less than shoot and root parts. Overall, the results revealed that T. natans irrigated with contaminated irrigation supplies at Zone 2 and 3 showed the highest BAF of heavy metals than Zone 1. Because the heavy metal concentrations in edible parts of T. natans did not exceed the threshold limits, the contaminated water sources in the Saharanpur region of India should be used in a safe and controlled manner.

Investigation on Co-combustion characteristics and NOx emissions of coal and municipal sludge in a tangentially fired boiler

Using the current coal-fired power plant to treat sludge with large annual production is an efficient sludge treatment method. Nevertheless, the majority of the previous studies concentrated on sludge co-firing with low blending ratio and moisture content in utility boiler. Further analysis and discussion are necessary regarding the impact of sludge with high blending ratio and high moisture content on co-firing performance as well as the potential interactions between high moisture content sludge and coal during the co-firing process. The simulation results of the verified computational fluid dynamic (CFD) model can be regarded as numerical experiments. In the present research, CFD was used to analyze the co-firing characteristics of municipal sludge and coal in a 600 MW tangentially fired utility boiler. The impacts of sludge moisture content, blending ratio, blending strategy, and secondary air (SA) distribution on co-combustion characteristics and NOx emissions were investigated, and their potential synergistic effects were assessed. The co-firing of coal and sludge has little impact on the furnace outlet temperature while potentially lowering NOx emissions, provided that the net calorific value of the feeding of the mixture of sludge and coal is kept constant. The reduction of sludge moisture content can significantly improve co-combustion performance, but it also facilitates NOx production. Blending sludge from the position of the medium-upper burners can reduce the number of layers needed to burn the sludge in practical coal-fired boiler. Furthermore, the SA distribution has a major impact on the furnace outlet flue gas temperature and NOx content. The shrunk-middle type is the optimum scheme for SA distribution. This study contributes to a deeper knowledge of the actual co-firing of sludge and coal in the utility boiler and provides a possible theoretical foundation for the widespread, clean, and effective use of sludge.

Analysis of the effect of using divalent and trivalent iron compounds on sludge dewatering performance in thickening units

Abstract Sludge is one of the by-products of wastewater treatment plants (WWTPs). To assist biological processes, part of the produced sludge is returned to the treatment process and the excess is removed from the treatment plant whereby it undergoes thickening and dewatering. Numerous studies have been conducted to investigate the effect of different coagulants on dewatering from sludge, but the effect of using divalent iron for this purpose has not been investigated so far. In this research, the effect of divalent and trivalent iron compounds (ferrous sulfate and ferric chloride) on the dewatering of excess sludge of the first module of the Bojnourd WWTP (Iran) has been investigated. In this regard, first, the effect of different doses of each coagulant to optimize the dewatering characteristics of sludge was investigated and then the effect of pH change by adding lime was investigated. The results showed that the addition of optimal doses of FeSO4 (0.6 and 0.4 g/l) and lime (0.664 and 1.5866 g/l) reduced the capillary suction time of sludge by 30.6 and 32.7%, respectively, while reducing the moisture content of sludge cake by 26 and 30.6%.

Prediction of hydrogen yield from supercritical gasification process of sewage sludge using machine learning and particle swarm hybrid strategy

This study presents an integrated framework of machine learning models (Artificial Neural Network, Ensembled Learning Tree, Support Vector Machine, and Gaussian Process Regression) and particle swarm optimization (PSO) to predict and optimize hydrogen production from SCWG using sewage sludge characteristics and process parameters. According to the results, ELT-PSO is preferred for forecasting hydrogen yield (Coefficient of determination (R2) = 0.997, Root Mean Square Error (RMSE) = 0.093), and it is highly suggested for handling complex variable-target correlation. However, Support Vector Machine (SVM) performed poorly, with R2 = 0.83 and RMSE = 2.28. According to SHAP feature importance Temperature, Carbon, Hydrogen, and Pressure are among the parameters that have strong impact. In addition, by adjusting the ML hyperparameters, optimization method (PSO) was used to maximize H2 yield. The optimized ELT-PSO model was utilized to establish a Graphical User Interface that made it simple to calculate H2 yield.

Characteristics of Sludge from the Treatment of Soilless Plant Cultivation Wastewater in a Rotating Electrobiological Disc Contactor (REBDC)

Due to the high nitrogen and phosphorus concentrations in wastewater from soilless cultivation of tomatoes, the sludge formed during wastewater treatment can be used as a source of nutrients in agriculture. The effect of electrical direct current (DC) density (J) and hydraulic retention time (HRT) in a rotating electrobiological contactor (REBDC) on the quantity and quality of sludge generated in the process of tomato soilless cultivation wastewater treatment was determined. The cathode consisted of discs immobilized with biomass, while the anode was an aluminum electrode. HRTs of 4 h, 8 h, 12 h, 24 h and (J) of 0.63, 1.25, 2.50, 5.00, and 10.00 A/m2 were applied. The study showed that the increase in (J) caused an increase in the amount of sludge generated. The increase of (J) contributed to increased concentrations of biogenes in the sludge, whereas extension of HRT at a given current density contributed to increased concentrations of nitrogen and phosphorus (up to 6.2% and 0.8% respectively) and to the reduced content of organic matter (up to 23.04%). The examined sludge was stabilized, sanitary, and safe, and may be an alternative to mineral fertilizers. This study showed that larger sludge amounts are produced in a DC mode aerobic REBDC than in an alternating current anaerobic one.

Effect of hydrothermal process on the pyrolysis of oily sludge: Characterization and analysis of pyrolysis products

In this paper, the effect of the pretreatment method combined with hydrothermal treatment and in situ mechanical compression (HT-MC) on the pyrolysis characteristics of oily sludge (OS) was investigated. The results of the thermal analysis showed that the temperature range in different pyrolysis stage intervals shifted to a lower level and the weight loss rate decreased significantly after HT-MC. Isoconversional methods were employed with an estimated apparent activation energy of 92.66 –198.21 kJ·mol−1 for the pyrolysis of OS after HT-MC. As the hydrothermal temperature increased to 240 °C, the yield of char increased from 80.44 to 86.08 wt%, and the yield of oil decreased from 16.03 to 11.23 wt%. Compared to the raw material, the gas products from the pyrolysis of OS after HT-MC had a higher H2 concentration and yield. The analysis results of GC-MC showed that, compared with the pyrolysis oil obtained by direct pyrolysis, the content of olefins in pyrolysis oil obtained in pyrolysis of OS after hydrothermal treatment increased from 0.86 % to 5.73 %. Furthermore, the relative content of alkanes in pyrolysis oil increased from 76.12 % to 87.40 % with the rise of hydrothermal temperature from 160 to 240 °C.

The Effect of the Elemental Composition of Municipal Sewage Sludge on the Phosphorus Recycling during Pyrolysis, with a Focus on the Char Chemistry—Modeling and Experiments

The present study investigates how the original sewage sludge characteristics influence the composition of sewage sludge-based chars for land applications. Sewage sludge from two different wastewater treatment plants in Sweden was pyrolyzed at 500, 700, and 900 °C, and the resulting chars were analyzed. Thermodynamic equilibrium calculations (TEC), together with chemical fractionation, were implemented to simulate the char after the pyrolysis process at different temperatures. The results showed that, in general, for both the municipal sewage sludge (MSS), phosphorus (P) was significantly retained in the char at various temperatures. However, no specific correlation could be found between the pyrolysis temperature and the amount of P remaining. With regard to the heavy metals removed from the char after the pyrolysis reaction, the concentrations of copper, chromium, lead, nickel, zinc, and cadmium were below the limits of the Swedish regulations for farmland application.

Effect of Metal Oxides on Combustion Characteristics of Excess Sludge

In this paper, it was studied that the effects of heating rate and four metal oxide on the combustion characteristics of excess sludge, such as CaO, Fe2O3, MgO and Al2O3, and the combustion kinetic parameters of sludge were obtained based on Coats-Redfern model. This result indicated that the ignition of sludge can be restricted with the increase of heating rate, but it was conducive to burnout, and the increasing about the flammability, stability and comprehensive combustion characteristic index of sludge. The addition of Fe2O3 and Al2O3 could improve the ignition performance of sludge to a certain extent, which was most obvious at the heating rate of 10 and 20 °C/min, respectively. Furthermore, the existence of Fe2O3, MgO and Al2O3 can improve the burnout performance of sludge, represented by MgO. Under the condition of low heating rate, the presence of Fe2O3 and MgO was beneficial to improve the comprehensive combustion characteristics of sludge. According to the distribution of combustion kinetics parameters, it was showed an increasing trend about the activation energy of sludge with the increase of heating rate at the range of 374.88-575.61 °C, which was also unfavorable to the combustion of fixed carbon. At the same heating rate, the activation energy decreased by adding Fe2O3 and Al2O3 at the range of 148.40-374.88 °C, which was beneficial to the release of volatiles and the combustion reaction, while the activation energy at the range of 374.88-575.61 °C decreased after adding CaO, which promoted the combustion of fixed carbon.

Characterization of sludge from the Water Treatment Plant (WTP) of the city of Palmeira dos Índios - Alagoas for potential application in ceramic masses

RESUMO O lodo de Estação de Tratamento de Água (ETA) quando disposto inadequadamente pode ocasionar desequilíbrio ambiental e problemas de saúde pública, devido à lixiviação de metais pesados para os corpos hídricos. Dito isso, este trabalho objetivou caracterizar de maneira física, química, térmica e mineralógica o lodo da ETA da cidade de Palmeira dos Índios-AL. A metodologia empregada foi de caráter experimental através da realização dos ensaios de granulometria, limites de Atterberg, fluorescência de Raios X, difração de Raios X e análise termogravimétrica. Após o ensaio de granulometria o lodo apresentou característica de areia fina. Na análise química identificou-se presença do Ca (7,81%) e Mg (2,51%), que podem interagir com elementos formadores de fase vítrea Si (55,65%) e Al (12,03%) durante a sinterização. Ademais, os percentuais mais significativos de silício e alumínio apresentaram-se na forma de quartzo e caulinita, corroborando com os resultados de fluorescência de Raios X. Na análise térmica houve perda de massa em torno de 42% até a temperatura de 400°C, sinalizando a possibilidade de tratar termicamente o subproduto, antes de sua incorporação em cerâmicas. Por fim, o lodo apresenta potencial de aplicação em matrizes cerâmicas, dado a presença de elementos com características fundentes.

Experimental Study on Rheological Properties of Temporary Storage Sludge

In order to master the rheological properties of temporary sludge, the sludge in Shanghai Laogang temporary storage area was sampled, and the rheological properties test was carried out. The effects of temperature, solid content and other parameters on the rheological properties of sludge were analyzed. Based on the above research and analysis results, the key parameters that affect the rheological properties of sewage sludge were analyzed, and combined with previous research conclusions, the methods such as summary and numerical fitting were used. The sludge function expression of the rheological characteristics of the temporary storage sludge is obtained, which provides theoretical guidance for the transport of sludge in the temporary storage area.

Numerical Simulation of Vacuum Preloading for Chemically Conditioned Municipal Sludge

Municipal sludge is a sedimentation waste produced during the wastewater process in sewage treatment plants. Among recent studies, pilot and field tests showed that chemical conditioning combined with vacuum preloading can effectively treat municipal sludge. To further understand the drainage and consolidation characteristics of the conditioning sludge during vacuum preloading, a large deformation nonlinear numerical simulation model based on the equal strain condition was developed to simulate and analyze the pilot and field tests, whereas the simulation results were not satisfactory. The results of the numerical analysis of the pilot test showed that the predicted consolidation degree was greater than that measured by the field tests, which is attributed to the relatively low permeability layer formed during the preloading process of the prefabricated vertical drain. To better reflect the consolidation process of the conditioned sludge, a simplified analysis method considering the low permeability layer around the prefabricated vertical drain was proposed. The initial permeability coefficient of the low permeability layer is determined via numerical simulations using finite difference method. The predicted settlement curve was in good agreement with the measured results, which indicated that the numerical simulation based on the equal strain condition considering the relatively low permeability layer can better analyze the consolidation process of ferric chloride-conditioning sludge with vacuum preloading.

Investigation of the influence of negative temperatures on the technological properties of belite sludge

The paper describes the characteristics of belite sludge - a large-tonnage waste of alumina production. The influence of negative temperatures on the technological properties of the sludge was investigated. The regularities of sludge cooling during its excavation, long-term storage and in the technological process of structural layers’ construction in winter conditions have been studied. Recommendations have been developed for the construction of foundations (coatings) from sludge and sludge-mineral materials at temperatures below minus 20°C. The implementation of research results helps to prolong the construction season, reduce material consumption and increase durability during construction, reconstruction and repair of transport infrastructure objects.

Study on Treatment Techniques for Food Waste and Municipal Sludge in County-Level Cities in Guizhou Province

Based on the characteristic of food waste and municipal sludge and the adaptability of various treatment techniques, comparisons of economic efficiency are proposed against the ubiquitous problems concerning food waste and municipal sludge disposal in county-level cities in Guizhou Province. And aerobic fermentation and hermetia illucens-based bioconversion are recommended for municipal sludge and food waste, respectively, to maximize resource reclamation and utilization.