Monika Czop

Mineral residues from wastewater may constitute potential secondary resources; however, their heterogeneous composition and potential to release contaminants through leaching require careful evaluation. This case study compared grit chamber (GC) waste and sewer cleaning (SC) waste collected from a municipal wastewater management system, focusing on their physicochemical properties, chemical composition, particle size distribution, and leaching behavior. The tested materials were separated into coarse (≥2 mm) and fine (2. Sulfate concentrations in aqueous extracts from GC reached 1511 mg/L, compared with 98.6–105 mg/L in extracts from SC. Under the applied leaching conditions, the release of selected trace elements was limited. The results indicate that particle size alone does not fully explain the observed differences in contaminant distribution and release. Although SC waste exhibited relatively favorable properties for raw material recovery, these findings are limited to the tested material batches and laboratory conditions. Therefore, before material recovery is considered, detailed characterization is necessary, taking into account waste origin, appropriate pretreatment, and an environmental assessment tailored to the intended application.

The management of hazardous municipal solid waste incineration (MSWI) residues represents a critical challenge for sustainable development due to their increasing generation and environmental risk. At the same time, the cement industry faces urgent pressure to reduce CO₂ emissions associated with clinker production, creating a demand for alternative supplementary cementitious materials. The aim of this study was to evaluate the feasibility of valorising hazardous municipal solid waste incineration (MSWI) air pollution control fly ash (EWC 19 01 07*) as a constituent of Portland composite cement, in line with circular economy principles and the need to reduce CO₂ emissions associated with clinker production. The investigated fly ash, originating from flue gas cleaning processes, is characterised by high alkalinity and elevated concentrations of heavy metals, which currently necessitate controlled landfilling. To enable its safe reuse, the ash was subjected to high-temperature thermal treatment following granulation and subsequently incorporated into cement formulations under semi-industrial conditions. Two Portland composite cements were produced with different ash contents, corresponding to CEM II/A-07 and CEM II/B-07, while a Portland cement manufactured from the same clinker was used as a reference material. The chemical and phase composition of the ash before and after thermal treatment was analysed using XRF and XRD, supported by SEM/EDS observations. The results demonstrate that thermal treatment at 1150 °C induces partial phase stabilisation of APC fly ash without full vitrification, allowing its integration into cement systems under semi-industrial conditions. The incorporation of ash significantly alters hydration behaviour through increased water demand governed by particle porosity, CaO-rich phase composition, and early ionic interactions in the pore solution, leading to reduced workability and mechanical performance. While immobilisation efficiencies exceeding 99.5% were achieved for most heavy metals due to precipitation and incorporation into hydration products, barium exhibited persistent leaching controlled by its solubility under highly alkaline conditions and limited incorporation into C–S–H phases. These findings define both the technological feasibility and the key environmental constraints of APC fly ash utilisation in Portland composite cement. From a sustainability perspective, the proposed approach contributes to the reduction in hazardous waste landfilling and supports clinker substitution in cement production. The results demonstrate the potential of integrating waste management and low-carbon material design within a circular economy framework while highlighting current environmental limitations related to barium leaching.

Assessing soil quality is essential for sustainable land use and agricultural productivity, particularly in the case of degraded, sandy, or low-organic-matter soils that suffer from poor water retention and reduced biological activity. One promising tool in this context is the Dexter soil quality index (S-index), which focuses on the relationship between volumetric water content and soil structure stability. Unlike general soil quality indices (SQI) that often integrate chemical or biological indicators, the S index offers a more physically grounded and quantifiable parameter for evaluating soil physical quality and water availability. It is particularly valuable for monitoring changes following organic amendments such as sewage sludge. The aim of this study was to evaluate the influence of sewage sludge application on the Dexter S-index, as an indicator of improved soil usability in terms of volumetric water content and retention capacity. The research was based on controlled pot experiments involving three mineral soil types: sandy- loam clay, loose sand, and clayey silt. Each soil type was amended with sewage sludge at rates equivalent to 50, 100, and 200 Mg∙ha−1. The results showed a clear increase in the S-index with increasing sludge doses across all soil types. The greatest relative improvements were observed in light-textured soils (0.042), where the original S values were lowest (0.018). This confirms the positive effect of sewage sludge on enhancing soil structure and water availability, particularly in sandy soils with inherently low retention capacity.

This study investigates the valorisation of mixed municipal waste glass (MMWG; EWC 20 01 02) as a sustainable supplementary material in cement mortars. In contrast to most existing studies, which focus almost exclusively on homogeneous container glass, this work addresses a heterogeneous waste stream derived from municipal selective collection, containing flat glass, mirrors, ceramics, porcelain, and metallic residues. Such mixed household glass has not previously been systematically evaluated in cement mortars, thereby addressing a clear research gap. The MMWG was washed, dried, and ground in a Los Angeles drum with corundum abrasives to obtain a fine glass powder (FGP < 63 µm) with a median particle size of approximately 20 µm and a Blaine fineness of 360 m²/kg. Microstructural and chemical characterisation of the milled glass confirmed its highly amorphous nature and angular particle morphology resulting from grinding. In addition, coarse glass granules (0–4 mm) were used as partial replacements for natural sand in mortar mixtures. The incorporation of FGP led to a 4–12% reduction in flowability, attributable to the angular shape and increased specific surface area of the ground-glass particles. At 28 days, mortars containing 5–10% FGP exhibited mechanical properties comparable to the reference mix, while at 56 days their compressive strength increased by up to 8%, indicating delayed pozzolanic activity typical of finely milled, amorphous glass. Mortars containing coarse glass primarily reflected a filler and aggregate-replacement effect. Leaching tests conducted in accordance with PN-EN 12457-4 demonstrated that all mortars, both reference and MMWG-modified, complied with the non-hazardous waste limits defined in Council Decision 2003/33/EC. Minor exceedances of Ba and Cr relative to inert-waste thresholds were observed; however, these values remained within the permissible range for non-hazardous classification and were attributed to ceramic and metallic contaminants inherently present in the mixed glass fraction. Overall, this study demonstrates that mixed municipal waste glass—a widely available yet rarely valorised heterogeneous waste stream—can be effectively utilised as a finely ground supplementary material and as a partial aggregate replacement in cement mortars, provided that particle fineness is adequately controlled and durability-related effects are monitored. The findings extend the applicability of glass waste beyond container cullet and support the development of circular-economy solutions in construction materials.

This study investigates the valorization of municipal solid waste incineration (MSWI) residues—specifically bottom ash with slag (BA + S) and fly ash (FA)—through alkaline activation in geopolymer and cementitious systems. The research demonstrates that alkali activation significantly improves mechanical properties, with compressive strengths up to 45.9 MPa for cement mortars and 33.2 MPa for geopolymers. A key innovation includes the quantification of hydrogen gas release during activation, with up to 72.5 dm³/kg H₂ from BA + S, offering insights into binder design and potential green hydrogen recovery. Environmental leachability assessments confirmed that activated BA + S immobilizes heavy metals effectively, although FA showed higher barium and lead leaching. Morphological analysis (SEM, granulometry) revealed microstructural changes enhancing reactivity. Additionally, a practical swelling test is proposed for early detection of expansion risk. The findings contribute to the development of sustainable, high-performance binders from waste, with implications for circular economy and energy valorization strategies.

This study evaluates the potential use of reclaimed sand from municipal wastewater treatment plants (WWTP), categorized as waste under code 19 08 02, as a full substitute for natural sand in cement mortars. The sand was subjected to alkaline pretreatment using sodium hydroxide (NaOH) at concentrations of 0.5%, 1% and 2% to reduce organic impurities and improve surface cleanliness. All mortar mixes were prepared using CEM I 42.5 R as the binder, maintaining a constant water-to-cement ratio of 0.5. Mechanical testing revealed that mortars produced with 100% WWTP-derived sand, pretreated with 0.5% NaOH, achieved a mean compressive strength of 51.9 MPa and flexural strength of 5.63 MPa after 28 days, nearly equivalent to reference mortars with standardized construction sand (52.7 MPa and 6.64 MPa, respectively). In contrast, untreated WWTP sand resulted in a significant performance reduction, with compressive strength averaging 30.0 MPa and flexural strength ranging from 2.55 to 2.93 MPa. The results demonstrate that low-alkaline pretreatment—particularly with 0.5% NaOH—allows for the effective reuse of WWTP waste sand (code 19 08 02) in cement mortars based on CEM I 42.5 R, achieving performance comparable to conventional materials. Although higher concentrations, such as 2% NaOH, are commonly recommended or required by standards for the removal of organic matter from fine aggregates, the results suggest that lower concentrations (e.g., 0.5%) may offer a better balance between cleaning effectiveness and mechanical performance. Nevertheless, 2% NaOH remains the obligatory reference level in some standard testing protocols for fine aggregate purification.

In light of the global raw material crisis and the ongoing degradation of the natural environment, this study provides a significant contribution to the advancement of the circular economy in the construction sector. The authors conducted a comprehensive analysis of the feasibility of using waste sands originating from wastewater treatment plants as substitutes for natural fine aggregates in concrete mixtures. The investigation included the evaluation of the physicochemical, environmental, and mechanical properties of the analyzed waste sands. The results demonstrate a high application potential for sewer cleaning sand (SC), which, in its current form, can be used in non-structural applications. The key advantages of the sand that was examined include a high sand-equivalent value (98.2%), low contents of impurities (LOI < 1.5%), and a favorable chemical composition. Leaching tests for harmful substances, including heavy metals, for both the sand and the mortar samples, did not indicate any significant environmental risk. One principal conclusion of the study is the identification of the possibility of closing the waste life cycle at the wastewater treatment plant stage, which could significantly contribute to the reduction of landfilled waste volumes and operational costs.

Using waste materials as replacements for sand in building materials helps reduce waste and improve the properties and sustainability of the construction materials. Authors proved the possibility of using imperial smelting furnace (ISF) slag granules as a 100% substitute for natural sand in self-compacting (SCC) cement-based mortars of calcium sulfoaluminates (CSA). The study proved that ISF slag’s radioactive properties meet this area’s requirements. CSA cement eliminates the noted problem in the case of concrete with Portland cement, which is the extended setting of the cement binder. The research findings indicate that using slag to replace sand up to 100% in mortars without grains smaller than 0.125 mm allows high flowability, compaction, low porosity and mechanical parameters. The compressive strength of the CSA cement mortars was about 110 MPa, and more than 140 MPa for geopolymer mortar. Unfortunately, the alkaline pH of a geopolymer causes high leachability of barium and sodium. Thus, the CSA cement is in a more favourable binder to achieve high strength, is environmentally friendly, and is a self-compacting mortar or concrete.

The study concerns evaluating the physical and chemical properties of sand from sand separators of wastewater treatment plants in terms of requirements for construction aggregates. Thus, an analysis of the physical properties of sand was carried out, i.e. its moisture content, bulk density, and grain density, as well as an analysis of the chemical composition of sand. The intention of the research is to find an alternative to the dwindling supply of this type of raw material, which is essential for the construction sector. It is currently estimated that within 20 years there will be a shortage of sand of suitable quality for use in construction. The article presents the results of physicochemical tests and leachability of selected harmful substances (P, F, N-NH4+, Cl, SO42-) and heavy metals (Ba, Zn, Cu, Pb, Cd, Cr, Co, Fe, Ni) from waste from desanding.

Innovative building materials should also be pro-environmental. This article discusses the environmental footprint of geopolymer and cement-based mortars. It describes the methodology for preparing geopolymer and cement mortars using mineral wool waste. The phenol–formaldehyde resin used in mineral wool is a source of phenol and formaldehyde emissions to the environment. The prepared mortar samples were subjected to durability tests to assess the correlation between the amount of mineral wool and the flexural and compressive strength of the samples. The key element of the paper is to test whether immobilisation of mineral wool in the geopolymer will reduce leaching of phenol and formaldehyde into the environment. The results revealed that cements prepared with mineral wool showed higher compressive strength, whereas geopolymer samples had better flexural strength. The study also proved that immobilisation of the wool in the geopolymer reduces phenol and formaldehyde leaching significantly.