Sewage Sludge Fly Ash Research Articles

Properties of artificial lightweight aggregates prepared from coal and biomass co-fired fly ashes and sewage sludge fly ash

The use of solid waste such as coal and biomass co-fired fly ashes and sewage sludge fly ash instead of clay and other non-renewable resources to produce lightweight aggregates (LWAs) is conducive to sustainable development. In this study, the effects of co-fired fly ashes, sewage sludge fly ash and quartz sand proportion, sintering temperature and sintering time on the physical properties and microstructure of LWAs are studied by single factor experiment. Experimental results show that the optimal experiment conditions are the raw material ratio of co-fired fly ashes: sewage sludge fly ash: quartz sand = 9: 1: 4, 2 wt% SiC as an expansion agent, and sintering at 1060 °C for 10 min. The LWAs obtained under the above conditions have a bulk density of 0.85 g/cm3, an apparent density of 1.84 g/cm3, a 1-h water absorption of 2.71 %, and a compressive strength of 8.68 MPa, which are in accordance with the GB/T17431.1–2010 standard. Besides, the heavy metal immobilization effect of the LWAs is satisfying, where the heavy metal leaching concentrations meet the standard of GB5085.3–2007. In conclusion, it is feasible to use the raw materials to prepare the LWAs under the above sintering conditions, and the prepared LWAs have high strength and low water absorption.

Preparation and characterization of biomass-ash composites derived from incinerated sewage sludge fly ash after hydrothermal treatment

With the increasing prominence of global environmental issues and the growing demand for sustainable development, biomass composites have attracted widespread attention as candidates for environmentally friendly and renewable construction materials. In this study, environmentally friendly biomass-ash composites (BACs) were fabricated using hydrothermally activated incinerated sewage sludge ash (HT-ISSA) as filler and straw powder with waste sawdust as the biomass matrix for hot pressing. An investigation was conducted into the effect of HT-ISSA on the physical properties of the composite, including the bending strength, compressive strength, and thermal conductivity. The composite prepared with 15 wt% HT-ISSA demonstrated an exceptionally high bending strength (30.60 MPa), compressive strength (44.76 MPa), and low thermal conductivity (0.2380 W/m·K). The enhanced physical properties of the BAC material are attributable to the change caused by hydrothermal treatment of the filler phase. Due to the introduction of hydrated calcium silicate, the cohesion performance of the filler significantly improved, thus leading to strong adhesion and penetration within the matrix. The obtained BAC is applicable for packaging and insulation materials, thus providing an effective solution for the economical and environmentally friendly recycling of incinerated sewage sludge ash and other bulk solid waste. Additionally, it contributes novel insights into alleviating the current shortage of forest resources.

Modification of Concrete Composition Doped by Sewage Sludge Fly Ash and Its Effect on Compressive Strength.

The sustainable development of construction materials is an essential aspect of current worldwide trends. Reusing post-production waste in the building industry has numerous positive effects on the environment. Since concrete is one of the materials that people manufacture and use the most, it will continue to be an integral element of the surrounding reality. In this study, the relationship between the individual components and parameters of concrete and its compressive strength properties was assessed. In the experimental works, concrete mixes with different contents of sand, gravel, Portland cement CEM II/B-S 42.5 N, water, superplasticizer, air-entraining admixture, and fly ash from the thermal conversion of municipal sewage sludge (SSFA) were designed. According to legal requirements in the European Union, SSFA waste from the sewage sludge incineration process in a fluidized bed furnace should not be stored in landfills but processed in various ways. Unfortunately, its generated amounts are too large, so new management technologies should be sought. During the experimental work, the compressive strength of concrete samples of various classes, namely, C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, and C35/45, were measured. The higher-class concrete samples that were used, the greater the compressive strength obtained, ranging from 13.7 to 55.2 MPa. A correlation analysis was carried out between the mechanical strength of waste-modified concretes and the composition of concrete mixes (the amount of sand and gravel, cement, and FA), as well as the water-to-cement ratio and the sand point. No negative effect of the addition of SSFA on the strength of concrete samples was demonstrated, which translates into economic and environmental benefits.

Highly Effective Adsorption Process of Ni(II) Ions with the Use of Sewage Sludge Fly Ash Generated by Circulating Fluidized Bed Combustion (CFBC) Technology.

Recently, more and more attention has been paid to the removal of nickel ions due to their negative effects on the environment and human health. In this research, fly ash obtained as a result of incineration of municipal sewage sludge with the use of circulating fluidized bed combustion (CFBC) technology was used to analyze the possibility of removing Ni(II) ions in adsorption processes. The properties of the material were determined using analytical methods, such as SEM-EDS, XRD, BET, BJH, thermogravimetry, zeta potential, SEM, and FT-IR. Several factors were analyzed, such as adsorbent dose, initial pH, initial concentration, and contact time. As a result of the conducted research, the maximum sorption efficiency was obtained at the level of 99.9%. The kinetics analysis and isotherms showed that the pseudo-second order equation model and the Freundlich isotherm model best suited this process. In conclusion, sewage sludge fly ash may be a suitable material for the effective removal of nickel from wastewater and the improvement of water quality. This research is in line with current trends in the concepts of circular economy and sustainable development.

Cementitious eco-composites and their physicochemical/mechanical properties in Portland cement-based mortars with a lightweight aggregate manufactured by upcycling waste by-products

Abstract This article presents testings’ results of cement composites with Composite Lightweight Aggregates (CLAs) as a partial substitute of natural aggregates. A new sustainable eco-composite manufacturing took place in laboratory conditions by using 100% waste by-products: PET flakes and sewage sludge fly ash (ssFA) streams or siliceous fly ash (FA). The manufactured (EN 196-1) modified cement mortars were tested in a various series of CLAs by applying volume replacements of 10% and 25% regarding the standard aggregate. The new insights on physical-chemical properties of the original materials and effective water and mechanical performance of both the fresh and hardened specimens contrasted the qualitative and quantitative assessments in the function of the two different aggregates production methods lines. Frattini test is also used to assess the impact of the aggregate composite on the cement composite and their mutual interactions. The obtained results show that the use of CLA as a substitute of standard aggregate allows reducing the water content in the mix while maintaining good workability and increasing compressive and flexural strengths up to 25% of reference mortar.

Lightweight PET based composite aggregates in Portland cement materials - Microstructure and physicochemical performance

This article presents testing results of cement mortars, in which Composite Lightweight Aggregates (CLA) obtained in laboratory conditions substitutes a part of natural aggregates. The new aggregates are sustainable products obtained by using 100% waste by-products: PET flakes and sewage sludge fly ash (ssFA) streams or siliceous fly ash (FA). The level of natural aggregate replacement by CLAs in mortars was 10% and 25% by vol. The purpose of the research was to assess the physicochemical properties of fresh and hardened mortars in the context of the quality assessment of two methods of producing CLAs and the type of fly ash used as their integral components. Surface modification of PET using both types of fly ash improves the useable properties of the obtained mortars compared to mortar using unmodified PET. In case of CLA aggregate based on PET and FA, no symptoms of depolymerization of polyethylene terephthalate were observed in the presence of alkali from cement paste. In case of mechanical properties modelled with CLA composite, an increase in compressive or flexural strength has been observed due to the possibility of lowering the w/c ratio in CLAs mixtures without loss of workability. Replacing only a small part of the natural aggregate with CLA aggregate allows for a double ecological aspect: saving of natural resources and full management of problematic plastic and mineral waste. Cement composites with composite lightweight aggregates may be ecosolution for a number of applications for building engineering like ordinary concrete, small pre-cast or modulus concrete.

Evaluation of the co-application of fly ash and sewage sludge on soil biological and biochemical quality

Disposal of sewage sludge (SS) and fly ash (FA) is a multifaceted problem, which can affect environmental quality. FA has the potential to stabilize SS by reducing metal availability and making the SS suitable for application in the agricultural sector. An experiment was performed to evaluate soil biological quality changes with the combined amendment of SS and FA (fluidized bed combustion ash (FBCA) and lignite fly ash (LFA)). SS was amended with 0, 10, 30, 50 and 100%, (w/w) of FA, and then the FA–SS mixtures were incubated with red soil at 1:1 (v/v). Soil quality parameters such as pH, electrical conductivity, N, soil enzyme activities such as dehydrogenase (DHA), urease (URE), and catalase (CAT), and microbial biomass carbon (MBC) were evaluated at 20, 30, and 60 days of incubation. pH and EC increased with FA–SS dose; however, N decreased. DHA and URE were found to be increased with 10% LFA amendment; thereafter it decreased. However, URE increased up to 30% of FBCA. CAT and MBC increased with both FA amendments, even up to addition of 50% FA. Bioavailable Zn, Cu, and Co contents were decreased by the addition of FA. Principal component analysis showed that pH is the most influential factor. MBC appears to be a sensitive soil indicator for the effects that result from the addition of FA–SS. Phytotoxicity studies with Zea mays showed optimum performance at 30% FA. Addition of 10–30% FBCA or LFA to SS has a positive advantage on soil biological quality.

Evaluation of leaching and ecotoxicological properties of sewage sludge–fly ash mixtures

The objectives of this work were the evaluation of sewage sludge stabilization by mixing with fly ash, the examination of the physicochemical properties of the produced materials and their leachates and the assessment of their environmental impact by the evaluation of the ecotoxic characteristics. Different ratios of fly ash and sewage sludge (1:1, 1:2, 1:3, 1:6, and 1:9) were mixed for 48 and 72 h. After mixing, the liquid phase of the produced materials was analyzed for total coliforms and Escherichia coli, while the solid residue was dried and tested for the leaching characteristics by the application of TCLP and EN 12457-2 standard leaching methods. Furthermore, the produced leachates were analyzed for their content of specific metals, while their ecotoxicological characteristics were determined by the use of toxicity bioassays, using the marine photobacterium Vibrio fischeri and the crustacean Daphnia magna. The phytotoxicity of sewage sludge–fly ash mixtures was also determined by utilizing seeds of three higher plants (one monocotyl and two dicotyls). The mixtures exhibited low metal leaching in all cases, while the ecotoxic properties increased with the increase of fly ash/sewage sludge ratio. The phytotoxicity testing showed increased root length growth inhibition.

Effects of the Basicity on the Comelting Conditions of Municipal Solid Waste Incinerator Fly Ash and Sewage Sludge Ash

In this study, the effects of the basicity on the pouring point of the municipal solid waste incinerator fly ash-sewage sludge ash mixture is investigated. Four kinds of sewage sludge ash, which were collected from several primary and secondary sewage treatment plants and were produced by different processes and sludge conditioning alternatives, were used as modifiers. The results indicate that the pouring point of the mixture increased with increasing basicity, within the range of 0.65–1.90. The pouring point is affected by the contents of the mixtures (CaO, SiO2, Al2O3, and the flux). It is suggested that an increase in the CaO content tends to raise the pouring point, whereas an increase in the SiO2 and/or the Al2O3 contents cause as adverse reaction. The prediction equation, obtained by multilinear regression (significant level is 0.05), is as follows: pouring temperature =1189.6 + 4.19CaO-0.96 SiO2-4.33 Al2O3 (R2 = 0.91). In general, the pouring point decreased when the basicity was <1. The pouring point apparently increased when the basicity was>1.2. The regression squares for the different basicities were between 0.84 and 0.91. From these relationships, we note that a basicity index of 5 gave the best R2 (0.91). From the results of this study, it can be concluded that the modification of the basicity of the fly ash by the addition of sewage sludge ash to lower the pouring point is feasible and leads to a more energy-efficient melting process. In addition, these synthetic slags have a good pozzolanic reactive activity.

04/00967 Crystalline phase control of glass ceramics obtained from sewage sludge fly ash: Park, Y. J. et al. Ceramics International, 2003, 29, (2), 223–227

04/00967 Crystalline phase control of glass ceramics obtained from sewage sludge fly ash: Park, Y. J. et al. Ceramics International, 2003, 29, (2), 223–227

Crystalline phase control of glass ceramics obtained from sewage sludge fly ash

Different types of glasses and glass-ceramics were made using fly ash from sewage sludge incinerators. The optimum nucleation condition was heating at 760 °C for 1 h. Crystallization of the nucleated specimen in the region of 1050–1200 °C resulted in the formation of two crystalline phases, i.e. anorthite and diopside. The relative fractions of these two phases changed with crystallization temperature. Specimens heat-treated for 2 h at 1050 °C consisted mainly of diopside crystals with a minor proportion of anorthite. On the other hand, those heat-treated at 1150 °C were primarily composed of anorthite. Glass-ceramics containing large amounts of diopside (1050 °C/2 h) generally displayed better physical and chemical properties than their anorthite counterparts (1150 °C/3 h) due to the interlocking microstructure of diopside crystals.