Search Results (226)

In the face of the raw materials crisis and environmental concerns, sustainable waste management has become a priority for current and future generations. Recycling waste from wastewater treatment plants in a closed loop protects natural resources, reduces landfill volumes, and lowers disposal costs. This paper presents the results of tests on the physical, filtration, and mechanical properties of mixtures of washed mineral waste (WMW) from grit chambers with fly ash from the thermal treatment of municipal sewage sludge (SSA) in a fluidized bed furnace. Additionally, radiological tests of the mixture components were conducted. Based on the conducted tests, the possibility of sustainable use in civil engineering, such as soil backfills and embankment construction materials, was assessed. The possibility of safely using waste materials in the indicated construction solutions was demonstrated for mixtures with dominant WMW content (90% and 70% by total weight). The waste mixtures correspond to poorly or medium-grade sands with a small amount of silt (uniformity coefficients of 3.33, 3.50, and 8.00). They are characterized by maximum dry densities of 1.542, 1.770, and 1.780 g/cm³; optimal moisture contents of 12.54, 12.86, and 20.25%; permeability coefficients of 0.08, 0.22, and 0.39 m/d; and internal friction angles of 38.4, 39.5, and 40.1°. The values of the determined parameters of some mixtures are similar to those of natural sands used as construction aggregates. All mixtures meet the geotechnical criteria for use in road embankments, below frost depth, and in flood embankment bodies. Mixtures with a 90% mass fraction of WMW were also approved for application as backfill for installation trenches. However, none of the mixtures met the hydraulic conductivity threshold required for the upper layers of embankments nor for backfill of abutments and retaining structures without the use of an additional binder (cement or lime), which is considered a prerequisite for these applications. Full article

Sustainable phosphorus (P) management in agriculture requires a circular economy approach through the use of so-called bio-based fertilizers (BBFs). The properties of BBFs vary widely depending on raw materials and production processes. However, it is still unknown how these properties, and particularly the dominant P compounds determine not only the efficiency of BBFs in supplying P to crops, but also their effects on soil functioning and crop quality. This study aimed to evaluate the efficiency of a representative set of BBFs, and relate this efficiency to their composition and dominant P compounds. To this end, 14 BBFs were studied: four from water purification (struvite, vivianite, and sewage sludge with and without composting), four composts (municipal solid waste (MSW), vineyard residues, and two using olive husks), three vermicomposts (two homemade and one commercial), fish meal, digestate, and a commercial organic fertilizer. Phosphorus forms in BBFs were determined using ³¹P nuclear magnetic resonance spectroscopy (P-NMR). The BBFs were compared to a single superphosphate (SSP) in a pot experiment growing wheat in two different alkaline soils, one rich in iron (Fe) oxides and one rich in carbonates. The effects on critical elements in grain [magnesium, Fe, zinc (Zn), manganese, and copper] and enzyme activities related to soil functioning and P cycling were also assessed. The dominant P compound in the BBFs was orthophosphate (73.8–89.5% of the total P in the NaOH–EDTA extracts). The MSW had the highest polyphosphate content (4.1%), a complex inorganic P compound. The organic P content ranged from 9.2% (fish meal) to 25.5% (Moge). Sewage sludge and composted sludge contributed high levels of phosphonates (4.1 and 5.6% of extracted P). The most abundant organic P compound class was inositol hexakisphosphates (IHPs), and myo-IHP (phytate) was the dominant IHP stereoisomer (1.2–6.4%) followed by D-chiro-IHP and scyllo-IHP. Plant dry matter and grain yield with most BBFs were not significantly different from that of SSP in both soils, likely due to the high concentrations of phosphate in relatively soluble forms in most of the BBFs. Vivianite and sewage sludge resulted in significantly higher grain yield than SSP (43% and 40%, respectively) in the carbonate-rich soil, likely due to progressive phosphate dissolution, which decreased the precipitation rate of insoluble calcium (Ca) phosphates. The highest P recoveries were obtained with horse manure vermicompost (65% and 15% higher than SSP in the Fe oxide-rich and in the carbonate-rich soil, respectively), partially attributed to the decreased precipitation rate of insoluble Ca phosphates with the added organic matter. Some BBFs increased micronutrient concentrations in grains and most decreased the P-to-Zn ratio relative to SSP. Overall, phosphatase and β-glucosidase activities increased with carbon-rich BBFs. Most of the studied BBFs could effectively replace fertilizers from non-renewable sources, in some cases with better crop P recoveries. Furthermore, some BBFs could provide additional benefits to grain quality, in terms of micronutrient supply for humans, and soil functioning. Full article

ASP flooding wastewater contains crude oil, suspended solids, anionic polymers and surfactants, with high viscosity, high zeta potential, difficult demulsification, flocculation and slow separation and sedimentation. In order to solve the problem of wastewater treatment of ASP flooding in oil fields, a magnetic branched core was prepared from ethyl silicate (TEOS), nano Fe₃O₄ and aminopropyl triethoxysilane (APTES), and then reacted with polyamine and methyl acrylate to synthesize the magnetic hyperbranched molecule FSNMN with demulsification ability. Using acrylamide (AM), acryloxyethyl trimethylammonium chloride (DAC) and maleic anhydride (MA) as raw materials, cationic polymer long chain (CAMHA) with flocculating properties was synthesized and grafted with hyperbranched molecules. The demulsification flocculation ability of the product regarding ASP flooding wastewater was evaluated, and the demulsification flocculation mechanism was summarized. The results showed that the average molecular weight of 3-FSNMN₄-C was 4.7 million, the cationic degree was 20.5%, and the saturation magnetization was 20 EMU/g. The removal rate of oil and suspended solids was 93.82% and 91.95% respectively when the simulated sewage was treated by magnetic field for 30 min. Magnetic hyperbranched star chain polymer provides a solution to the serious ecological environment problems caused by ASP flooding. Full article

Wastewater treatment plants (WWTPs) are important interfaces for the persistence and dissemination of antimicrobial resistance genes (ARGs) in the environment. This study investigated colistin resistance and the presence of mobile colistin resistance (mcr) genes in Enterobacterales isolated from a poultry slaughterhouse WWTP in Brazil. Samples were collected from raw sewage, an equalization tank, and treated effluent. A total of 27 Enterobacter spp. isolates were identified, of which 70.4% showed resistance to colistin (MIC range: 2 to ≥512 mg/L). PCR screening detected mcr-1 in two isolates and mcr-10 in three isolates distributed across all treatment stages, including the final effluent. Whole-genome sequencing of a representative isolate from treated effluent identified Enterobacter vonholyi ST3343, carrying a plasmid-borne mcr-10 gene on an ~107 kb IncFII(Yp) plasmid, along with additional resistance determinants. Phylogenetic analysis supported the classification of this gene as a novel allele, mcr-10.6. The persistence of a clonal lineage harboring mcr-10.6 throughout the treatment system indicates that conventional wastewater treatment may not effectively eliminate clinically relevant ARGs. These findings highlight treated effluent as a potential route for environmental dissemination of colistin resistance and reinforce the need for improved monitoring and mitigation strategies within a One Health framework. Full article

The pollution of water, including salt and fresh water, has become an emergency problem. Pollutants come from different sources and have various characteristics, starting from industry and fertilizers used in agriculture, sewage related to human living, and other sources. Diverse sources of pollution require a comprehensive approach to water purification. One possible approach may be the use of appropriate sorbents. Currently, one of the most promising materials used is zeolites. This is because they can come from various sources, including waste raw materials such as fly ash, and, therefore, allow for the use of a circular economy approach. Moreover, these materials can be modified, which enables their selective use for selected types of pollutants. Eventually, these materials become economically viable options. The main aim of this article is to present and analyze possible solutions to water pollution based on zeolite materials. For this purpose, a critical literature review was prepared. The review reveals that zeolites perform particularly well in ion-exchange-driven removal of inorganic contaminants, while their effectiveness for organic micropollutants under realistic conditions is often limited. The identified trade-offs between removal efficiency, regeneration stability, and scalability indicate that zeolites are best applied as function-specific rather than universal sorbents. From a sustainability perspective, this targeted applicability is supported by advantages, such as low material cost, long service life, and the possibility of using naturally occurring or waste-derived precursors, which, together, enable resource-efficient water treatment processes, reduced reliance on energy-intensive technologies, and the valorization of industrial byproducts within circular economy frameworks. Full article

To address the bottleneck of poor biological nitrogen removal efficiency caused by the extremely low carbon-to-nitrogen (C/N) ratio of domestic sewage in alpine plateau regions, this study used Hordeum vulgare var. coeleste L., a characteristic crop endemic to the Qinghai–Tibet Plateau, as raw material and adopted pretreated highland barley straw as an external carbon source. Three parallel experiments were carried out using the anaerobic–aerobic–anoxic sequencing batch reactor (AOA-SBR) process to investigate the nitrogen removal performance and functional succession of the microbial community in the AOA-SBR system under three C/N ratio ranges: 5~7, 7~9, and 9~11. The results showed that the addition of an external carbon source significantly improved nitrogen removal efficiency. The optimal C/N ratio range for nitrogen removal in this study was determined to be 7~9. A weakly alkaline environment was conducive to denitrification. The fermentation broth prepared by alkali pretreatment contained a large amount of readily biodegradable organic matter with low toxicity, and achieved excellent nitrogen removal performance, helping to realize cost reduction and efficiency improvement in wastewater treatment. At the optimal C/N ratio of 7~9, the average removal efficiencies of ammonia nitrogen (NH₄⁺-N) and total nitrogen (TN) reached 94.46% and 61.32%, respectively, which were significantly improved compared with the blank control group without external carbon addition. During the experimental period, no obvious changes were observed in microbial abundance at the phylum level, whereas the community structure at the genus level responded significantly to the addition of a straw carbon source. Among them, genera with specific degradation capabilities for straw hydrolysates, such as norank_f__Chitinophagaceae and unclassified_f__Comamonadaceae, were highly sensitive to variations in the C/N ratio. These genera could partially replace the nitrification and denitrification functions of other microorganisms and played a key role in the nitrogen removal process. In contrast, Thauera, a typical conventional heterotrophic denitrifier, showed no significant response to changes in the C/N ratio, indicating that the straw-based external carbon source mainly affected microbial genera with specific hydrolysate-degrading functions. Full article

The escalating production of sewage sludge presents a significant environmental challenge, while the construction industry simultaneously seeks sustainable raw materials to improve its circularity. This review analyses the technical and regulatory landscape for valorizing SS within the Latvian construction sector, set against the divergent strategies of its Baltic neighbours. While global research confirms the technical viability of using SS in fired-clay bricks and as a supplementary cementitious material (SCM), national management approaches differ starkly. Lithuania has adopted widespread incineration, and Estonia has focused on advanced composting. In contrast, Latvia’s national strategy is failing, with 51% of its 2024 sludge production diverted to “temporary storage”. This review identifies this crisis as a unique opportunity, arguing that incorporating dewatered digestate into fired-clay bricks is the most logical and economically viable pathway for Latvia, as it leverages existing industrial infrastructure. The primary obstacle to this circular solution is not technical but legal, specifically the lack of a national “End-of-Waste” (EoW) criterion for sludge-derived construction materials. Therefore, this article proposes a strategic roadmap for Latvia, centred on developing this essential legal framework, creating a national sludge characterization map, and initiating a pilot project to bridge the research-to-industry gap. Although Latvia is the primary focus of this review, the regulatory, infrastructural and material constraints analysed here are common in many small and mid-sized countries, making the insights applicable beyond the Latvian context. Full article

With ongoing development in the process industries, the accumulation of industrial inorganic solid wastes (IISWs) has become increasingly significant. IISWs are characterized by large volume and toxicity and pose challenges in treatment and control. IISWs from chemical processes mainly include red mud (RM), zinc slag, lithium slag (LS), electrolytic manganese residue (EMR), phosphogypsum (PG), water treatment sludge (WTS), sewage sludge, blast furnace slag (BFS), steel slag (SS), coal fly ash (CFA), coal gasification slag (CGS), copper smelting slag (CSS), and lead smelting slag (LSS). Having been chemically processed, they exhibit complex compositions that pose challenges for further utilization. In this paper, we comprehensively review the preparation of adsorbents from IISWs as raw materials, the applications of IISW-derived adsorbents, and their adsorption mechanisms. The obtained adsorbents include modified IISWs, zeolites, porous ceramics, and composite and hybrid adsorbents. The adsorption mechanisms, such as van der Waals forces, electrostatic interactions, and π–π interactions, contribute to the rapid adsorption kinetics and high adsorption capacity observed in these adsorbents. Full article

As solid biofuels gain increasing importance, the issue of rational management of the ash obtained from biofuel combustion is becoming increasingly relevant. This relevance will only increase in the future, since it is predicted that the main biofuel raw material will not be wood, but agricultural biomass with a high ash content. Biomass ash contains valuable nutrients, such as potassium and phosphorus, and therefore, it could be used for fertilization in agriculture. The concentration of nutrients in the ash can be made more balanced by granulating it with organic waste. This work presents the results of the environmental impact of using multi-crop biomass ash for fertilization of spring barley using the life cycle assessment method. Five scenarios were analyzed: (1) mineral fertilizer (MF), (2) non-granulated ash (NA), (3) ash and cattle manure pellets (ACM), (4) ash and sewage sludge pellets (ASS), and (5) ash and sapropel pellets (ASP). The results of the study show that all scenarios using ash for fertilization have a lower environmental impact compared with the scenario using only mineral fertilizers (MFs). The lowest carbon footprint (583.94 CO_2eq.) was determined for the ASP scenario. Normalization of the results showed that the ASS and ASP scenarios are the best from an environmental point of view, with the lowest environmental impact (24.90 and 24.60 Pt, respectively). Full article

Al-Musk Lake, an artificial waterbody of 2.9 km² formed by illegal dumping of 9.5 million cubic meters of raw sewage near Jeddah, Saudi Arabia, remains a significant subsurface environmental hazard after drainage activities in 2010. The current research employs a multidisciplinary approach, integrating geological mapping, aeromagnetic and electromagnetic surveys, Landsat imagery, and chemical analyses, to investigate contamination migration and accumulation. The objective is to delineate subsurface contamination pathways and assess their impact on soil and groundwater quality. Frequency-domain electromagnetic (FDEM) surveys identified areas of high apparent conductivity (up to 200 mS/m at 2000 kHz), indicative of deep contamination saturation. Chemical analysis of water and soil samples revealed distressing levels of heavy metals, Na⁺ up to 2400 mg/L, Ca²⁺ up to 3648 mg/L, and Fe up to 4150 mg/L, far exceeding irrigation safe standards. Findings locate two at-risk areas several kilometers from the lake, where contaminants accumulate through basement depressions controlled by faults. These pose immediate risks to adjacent residential areas and expanding agricultural belts. In short, subsurface contamination continues to spread westward. Short-term remedies include halting agricultural activities, treating in-storage water, and paving infiltration zones. A larger-scale geophysical survey, along with denser geochemical sampling and analysis, is necessary to guide long-term remediation and to protect public health. Full article

The urgent need for effective food waste management, coupled with the scarcity of carbon sources for sewage treatment, highlights the potential of producing carbon sources from food waste as a mutually beneficial solution. This study investigated the production of carbon sources through anaerobic fermentation using the liquid phase of food waste three-phase separation. Compared with previous studies using raw food waste or mixed substrates, the liquid phase derived from three-phase separation is richer in soluble organic matter and has been pre-heated (80 °C), which facilitates subsequent fermentation and offers easier integration into existing food waste treatment plants. A series of lab-scale batch fermentation experiments were carried out at different temperatures, including ambient, mesophilic, and thermophilic conditions, as well as varying initial pH levels (uncontrolled, neutral, and alkaline). The experimental results indicated that optimal production parameters involve a 4-day mesophilic fermentation at 35 °C with an initial alkaline pH, which increased the total VFAs yield by 252.5% to 40.26 g/L and raised the acetic acid fraction to 45.5% of total VFAs. Under these conditions, there was an observed increase in the relative abundance of acidogenic bacteria and a decrease in that of methanogen archaea. Furthermore, the denitrification performance of the produced carbon source was evaluated in short-term tests, and near-complete nitrate removal was achieved within approximately 2 h. These findings suggest the fermented liquid phase of food waste is a promising partial substitute for conventional external carbon sources. Full article

Mining and sewage treatment wastes have been accumulating at growing rates in urban areas. Recycling these wastes can be used to generate safe products for various agro-environmental uses, including the synthesis of fertilizers with the potential to sequester carbon (C) in the soil. Therefore, this study evaluated the physicochemical characteristics and C sequestration potential of biochar obtained by co-pyrolysis (500 °C) of sewage sludge (SS) individually or combined at a 1:1 (w:w) ratio with zeolitic basalt (ZB), referred to as SS + ZB_BC. Subsequently, the raw materials and biochars were characterized by X-ray diffraction analysis, proximate analysis, elemental analysis, and FTIR spectroscopy, as well as pH and electrical conductivity (EC) determination. The results show that pyrolysis optimized material properties, especially SS biochar (SSB), which exhibited high stability with the highest fixed C content (13.6%) and thermostable fraction (TSF) of 43%. On the other hand, ZB had a higher pH and a lower EC than SS. Co-pyrolysis promoted complementary effects on the chemical and C stability properties of the SS + ZB_BC combination. The combination raised the pH to a value close to neutrality (6.5), indicating potential corrective action for acidic soils. Furthermore, after co-pyrolysis, the TSF remained high (25.2%) and was classified as a high-longevity material (>1000 years), indicating high aromaticity and C condensation. Therefore, the co-pyrolysis of SS and ZB optimized the individual characteristics of the materials, thereby providing a promising and sustainable alternative for agro-environmental use that addresses the need to reduce C emissions and promote waste recycling. Full article

Advanced phosphorus (P) recycling from wastewater is critical for improving nutrient circularity and reducing soil pollution associated with the direct application of sewage sludge in agriculture. However, few studies evaluate the long-term environmental and economic trade-offs between recycled P products and raw sewage sludge application. This study compares struvite, vivianite, and dicalcium phosphate (CaP) as P alternatives to sludge to mitigate heavy metal accumulation in Spanish agricultural soils. Using data from 27,835 plots, heavy metal accumulation was simulated over 50- and 100-year fertilisation scenarios. The results indicate that continuous sludge application leads to widespread exceedances of zinc, copper, and cadmium, especially in alkaline soils, whereas substitution with recycled products can substantially reduce these risks. Vivianite balances P recycling and costs, CaP offers the best environmental performance but with higher investment, and struvite suits smaller regions prioritising environmental safety. Economic analysis favours advanced recycling over sludge, especially considering externalities such as soil remediation costs. Despite limitations, our findings emphasise the importance of integrating environmental externalities into economic assessments and the value of advanced P recycling for sustainable soil management. Full article

The growing medium is one of the key factors determining the yield and quality of lavender oil. The research conducted in greenhouse conditions aimed to assess the impact of a substrate with a reduced peat content enriched with compost from sewage sludge and bark on the growth, yield, and chemical composition of the oil from the inflorescences and leafy stems of English lavender ‘Sentivia Blue’. The plants were grown in pots filled with peat and chemical fertilizer, or in a substrate containing bark and sewage sludge compost, with or without fertilizer. Media affected the growth, leaf greenness index, and biomass production of lavender. Plants growing in peat with fertilizer were the tallest and widest. In turn, the highest number of inflorescences and the highest dry weight of inflorescences and leafy stems were found in plants grown in a mixture of bark and sewage sludge compost, with the addition of fertilizer. A significant interaction between the plant organ and the type of substrate was demonstrated, which affected the content of specific oil components. The content of essential oil was higher in inflorescences (1.15%) than in leaves (0.21%). The oil from the inflorescences was dominated by linalool, caryophyllene oxide, and linalyl acetate, while caryophyllene oxide, borneol, and geranyl acetate dominated in the leafy stems. The highest linalool content was found in oil obtained from inflorescences of plants grown in both media, based on bark and sewage sludge compost. The results show that the best quality parameters of the raw material and oil, including particularly high dry weight and linalool content, were obtained when the plants were grown in a medium consisting of bark, sewage sludge compost, and chemical fertilizer. Full article

This study systematically evaluated the removal performance of iron–carbon (Fe/C) micro-electrolysis materials with different proportions and preparation methods for nitrogen (N), phosphorus (P) and chemical oxygen demand (COD) in domestic sewage. This study investigated the effects of different Fe/C ratios, hydraulic retention time (HRT), raw materials and sintering bonding conditions on the efficiency of domestic sewage treatment through both static and dynamic experiments. In the static experiments, iron filings (IFs), steel slag (SS), and coconut shell carbon (CSC) were physically mixed, whereas the dynamic tests simulated the continuous treatment of domestic sewage. The results indicated that the Fe/C materials effectively removed P, particularly materials with high Fe/C ratios, which achieved removal rates of 96–98%. The COD removal efficiency of low Fe/C ratio material was better, reaching a removal rate of more than 70% under the optimal conditions. For Fe/C physical mixed materials, SS replacing IFs had excellent performance in ammonia nitrogen (NH₄⁺-N) removal (>93%), but other indicators were poor, which limited its application. Results from the continuous flow experiment indicated that the physically mixed filler with an Fe/C mass ratio of 2:1 showed excellent and stable TP and COD removal rates (98.6% and 92.8%) for the actual domestic sewage. In addition, the Fe/C micro-electrolysis filler sintered at 400 °C using kaolin as a binder exhibited good potential for pollutant removal, providing a feasible solution for reducing energy consumption. This study provides important data support for the development of low-cost and efficient decentralized rural sewage treatment technology. Full article