Papers by Keyword: Sewage Sludge

Abstract: This article discusses the use of solar dryers as a method for stabilizing and reducing the volume of residual sludge produced by wastewater treatment facilities. The study focused on the convective drying behavior of sewage sludge produced by the wastewater treatment plant of Meknes City under convective solar drying. The study aimed to investigate the drying kinetics of sewage sludge and emphasize the effect of temperature and water content on the evolution of the drying rate. The measured water content values showed a decrease as drying time increased. The results revealed the presence of phase II, which characterizes the decreasing rate drying period, and the absence of phase I, which describes the constant rate drying period.The study developed an empirical model to describe the kinetic behavior of convective solar drying of Moroccan domestic sludge. The model can be used to predict the shape of a drying curve under other aerothermal conditions. Additionally, the study analyzed the thermal diffusivity and activation energy of sewage sludge using an experimental macroscopic method based on Fick's diffusion model and the Arrhenius equation. The measured diffusion coefficient values range from 0,71 10^-9 m².s^-1 to 1,47 10^-9 m².s^-1, and the value of activation energy was evaluated at 17.54 kJ/mol.

Abstract: Chemical fertilizers currently poison arable agriculture, so organic fertilizers are now a new trend for soil improvement. This study investigates the appropriate ratio of fertilizer use and materials mixed with sewage sludge in the anaerobic co-digestion treatment method, which will best support agriculture. In the study, bio-organic fertilizer was composted of the co-digestion anaerobic with sewage sludge and agricultural wastes such as rice husk, rice husk charcoal, water hyacinth, cassava peel, and then tested on rice. The specific criteria of fertilizers such as total organic (TOC), total nitrogen (TN), and effective phosphorus (P₂O₅) and plant growth parameters such as germination rate (%), tillering rate, total weight (g) were evaluated. Initial results show the untreated sludge can be impacted negatively on plant development. The concentration of nutrients in the co-digestion composts was meet the requirements of the Ministry of Agriculture’s standards of organic fertilizer. These bio-fertilizers will play an important role in soil productivity and sustainability. Hence, the widespread use of organic fertilizers from waste to partially replace chemical fertilizers will open up opportunities to reduce farming costs for farmers and develop agriculture sustainably.

Abstract: Ethyl acetate as acyl accepter have been used for sewage sludge biodiesel production in micro packed bed reactor. Lipase acrylic resin enzyme activity was investigated in the interesterification reaction of converting the sewage sludge into a biodiesel product. The main parameters affecting the process was adjusted via the design of Box-Behnken and approach of response surface then the optimum conditions were as follow (reaction time=15 h, ethyl acetate/oil ratio=24:1, temperature=40 °C and enzyme quantity=18 wt%) providing 95.78 % biodiesel yield. The lipase acrylic resin was examined under the optimum conditions for the reusability. the flow effect and the heating process of the micro packed bed reactor was investigated. The product biodiesel physicochemical properties were evaluated according to the ASTM D-6751-2 and found acceptable comparable to the mineral diesel properties.

Abstract: Excess sludge generated from wastewater treatment plants (WWTPs) can cause negative impacts on human health, water bodies, aquatic plants, and soil quality. However, the produced sludge could be appropriately managed to obtain various economic and environmental benefits. One of the feasible and practical options of sludge management is the synthesize of biochar via oxygen-limited pyrolysis. The use of biochar adsorbent for pollutant removal offers various advantages such as high adsorption capability, low operating and chemical costs, no production of toxins. Hence, this study addresses the applications of sewage sludge-derived biochar for industrial wastewater treatment. The methods of sludge collection, drying, pulverization, and pyrolysis are illustrated. Biochar characterization methods (SEM, EDX, XRD, and FTIR analyses) and mechanisms of the adsorption process are described. The sludge-derived biochar could be used as an adsorptive material for industrial effluent treatment. Recommendations for future studies that could enhance the adsorption capacity of biochar and modified-biochar are given.

Abstract: Conversion of organic-containing sludges to a high value fertilizer is considered to be a rational solution from a recycling point of view. Aerobic respiration could serve as an indicator of stability and maturity of the treated sewage sludge (SS). The aim of this study was to characterize two SS samples, obtained from different wastewater treatment plants („D” and „J”), i.e, at the initial stage of treatment, alone and with amendments. Two methods for estimation of microbial respiration, as well as dehydrogenase activity were used. The SS-J demonstrated the higher microbial biodegradation activity, as compared to SS-D. In experiments with OxiTop® device, statistically significant (p<0.05) differences of the pressure drop between SS-J and SS-D have been revealed. Addition of peat to SS resulted in a more intensive pressure drop, compared to non-amended SS, i.e., -145 hPa vs. -76 hPa for SS-D and-199 hPa vs. -180 hPa for SS-J, respectively. The obtained results represent a methodical approach for characterization of raw SS in order to evaluate the amount of aerobically degradable organic substances and intensity of their oxidation. Further research is needed for highlighting the mechanisms responsible for interrelation of respiration intensity, bacterial community activity and other metabolic changes towards SS stabilization.

Abstract: This paper aims to present the characteristic of dewatered sewage sludge (SS) and red gypsum (RG) to determine their recycling potentials into a valuable product. The materials were characterized based on their physical-mechanical-chemical properties and morphology. The results showed that dewatered sewage sludge and red gypsum could complement each other when used together to form a new material the merits of which will be investigated in subsequent studies. RG has a better performance in term of plasticity and strength than SS due to fines content in the former and therefore its ability to retain moisture that contributes to cohesion between particles. Fine prisms and closer packing particles add strength in RG leading to higher resistance in compression. Unlike RG, SS has coarser particle and more voids causing it to lose the moisture content and becomes easily disintegrated. Chemical compositions of RG and SS as determined by XRF demonstrated a significant amount of CaO in the former and SiO₂ in the latter; the formation of hydrated products in the form of CSH and CAH gel from hydration or pozzolanic reaction contributes to strength improvement of the SS.

Abstract: Biological treatment of municipal and industrial wastewater becomes more common in EU countries. As a result, the amount of wastewater sludge increases. The political and economic situation in world is requiring new methods for recovery of non-renewable mineral resources. Sludge is great secondary source of many elements. The aim of this research is to summarize available techniques for sustainable utilization of industrial sludge and recovery of critical raw minerals (CRMs). The most common sustainable method is using treated sludge as fertilizer in agriculture due to high content of P, N, C and microelements. However, this method has many restrictions, e.g. it can contain toxic substances or lack of appropriate land. Thermal sludge treatment methods like pyrolysis have developed crucially in last decade and pyrolysis units for sludge treatment are commercially available now. Pyrolysis becomes the most sustainable method due to recovery of CRMs and better energy recovery comparing to incineration.

Abstract: Giving the current trend of recycling and reutilization residues, sludge reuse has become an environmental, social and economic necessity. A possible destination would be the utilization of sludge as part of cover layer in solid waste landfills. This paper aimed at investigating the geotechnical implications of the addition of domestic sanitized sewage sludge on clayey-silty sand. The sludge was sanitized with hydrated lime, in the proportion of 25% lime and 75% sludge, and held for 90 days in an agricultural greenhouse for its total stabilization. Then, geotechnical tests were conducted using pure soil, pure sanitized sewage sludge and mixtures of these two materials. Three mixtures were tested: 50% soil and 50% sludge, 66% soil and 33% sludge and 90% soil and 10% sludge. The results showed that the sanitized sludge is a coarse-grained material and, its Atterberg’s limits showed the lack of plasticity. Generally, the greater the sludge percentage in the mixture, the bigger the decrease on the shear strength parameters, it also leaves them lighter and more permeable. At the end, the conclusions were that the 10% sludge and 90% soil mixture has shown geotechnical characteristics that allow its utilization as daily and intermediate cover layers. The sludge and the 50% sludge mixture have shown geotechnical properties adequate for their utilization as component in draining sub-layer in final cover layer.

Abstract: LC-MS methods have become a very important method for brominated flame retardants (BFRs) analysis and replaced the traditional GC-MS method. This method enables the combination of excellence LC separation column with the sensitivity and specificity of state-of-the-art mass spectrometers and also suitable for the analysis of thermolabile and polar BFRs. In this study, a LC-MS/MS method has been developed for several classes of BFRs in sewage sludge matrix by combining the optimized LEE extraction and GPC cleanup. The advantages of the method include low detection limits (pg range), and the absence of thermal degradation of BDE-209.

Abstract: The paper discusses the EU directive and the rules for disposing of sewage treatment plant (STP) sludge and storage conditions that have been adopted, it does not fully cover possible use of STP sludge for industrial purposes. One of the ways of reducing amount of sludge is treatment of this waste for further application as additive or raw material for producing building materials. Manufacturing of porous ceramic materials from local raw materials (e.g. clay) using water treatment sludge and sawdust as combustible filler is possible. In order to reduce the sludge humidity, freezing method was used, where sludge give away more loose water in the process of thawing. It was proved during the research that sewage treatment plant sludge can be used to make porous ceramic materials.