Search Results (82)

Municipal solid waste landfill leachate represents one of the most environmentally challenging liquid effluents in modern waste management; however, its high nitrogen and phosphorus content renders it a potentially valuable nutrient source for microalgal phycoremediation. Here, Chlorella sp. and Scenedesmus sp. were cultivated for 15 days in CHU-10 standard medium and 50% (v/v) municipal landfill leachate from Nauta, Peru, and characterized across 33 biochemical variables, 14 physicochemical parameters, and 32 metal ions and trace elements. A sequential competitive multivariate pipeline comprising principal component analysis (PCA), hierarchical cluster analysis (HCA), permutational multivariate analysis of variance (PERMANOVA), and linear discriminant analysis (LDA) was applied to both the biochemical and bioremediation datasets. Leachate supplementation increased peak biomass density by 26.6–28.3% and elevated total protein by 56.9% in Chlorella sp. and 73.4% in Scenedesmus sp., while reducing total lipids by 37–46% and suppressing polyunsaturated fatty acid production. Both species achieved net biological removal efficiencies (NBRE) exceeding 86% for ammonium and ammonia; toxic elements, including Cd (~96%), Al (~92%), As (~90%), and Pb (~90%), were removed at higher NBRE than macro- and micronutrient categories. LDA achieved 100% leave-one-out cross-validation accuracy for species classification from both physicochemical and 32-element NBRE profiles. These findings indicate two complementary valorization directions, contingent on further biomass safety verification: leachate-grown Scenedesmus sp. shows a favorable combination of protein enrichment and nutrient removal for single-cell protein production integrated with bioremediation, while Chlorella sp. in standard medium shows a more favorable fatty acid profile for nutraceutical applications. Because leachate-grown biomass also accumulates inorganic and trace-element constituents from the medium, its suitability for protein or nutraceutical use requires direct heavy-metal characterization of the harvested biomass, independent of the demonstrated removal efficiency from the liquid phase. Full article

This study explored the utilization of coal gangue with high iron content to synthesize poly-ferric-alum-sulfate (PAFS) and coal gangue leaching residue-PAFS (CG@PAFS) coagulants, which were subsequently applied to treat landfill leachate and its concentrate. The results demonstrated that the PAFS coagulant exhibited notable removal efficiency for key pollutants, including chemical oxygen demand (COD) and total phosphorus (TP), with removal rates of 23.8% and 77.5%, respectively. Its performance was comparable to polyferric sulfate (PFS) and superior to aluminum polysulfate (PAS). Mechanistic investigations revealed that Fe³⁺ in the PAFS coagulant reacted chemically with phosphate ions, forming insoluble precipitates and facilitating phosphate removal through flocculation. Furthermore, PAFS also exhibited moderate removal efficiency for COD and ammonia nitrogen (NH₃-N) via flocculation processes. From a sustainability perspective, this study advances a circular economy model by simultaneously addressing two pressing environmental challenges: the valorization of coal gangue (a massive industrial solid waste) and the treatment of landfill leachate (a hazardous wastewater). Importantly, the post-treatment sludge, rich in available phosphorus and silicon, demonstrates promising potential for beneficial reuse as a soil conditioner, thereby closing the material loop and reducing reliance on virgin chemical resources. This integrated waste-to-resource approach aligns with multiple Sustainable Development Goals (SDGs), particularly SDG 6 (Clean Water and Sanitation), SDG 11 (Sustainable Cities and Communities), and SDG 12 (Responsible Consumption and Production). Overall, this study provides valuable insights into the resource-efficient utilization of coal gangue and presents an effective, low-carbon, and sustainable approach for landfill leachate management. Full article

Coastal riparian zones are important transitional areas for carbon cycling between terrestrial and aquatic ecosystems. However, the associations among litter-derived dissolved organic matter (DOM), soil DOM composition, and soil organic carbon (SOC) fractions across habitats remain insufficiently understood. This study aimed to clarify SOC fraction distribution in woody and herbaceous habitats and evaluate its associations with litter-derived DOM, soil DOM composition, and soil environmental factors in different seasons from a coastal riparian zone. In this study, woody habitats had higher SOC content in March, whereas herbaceous habitats showed greater SOC content in November. Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) were generally higher in different habitats. MAOC accounted for a large proportion of the measured SOC-related pools and showed a consistent positive association with SOC content. Soil DOM consisted of protein-like and humic-like components, with herbaceous habitats showing a stronger protein-like component and woody habitats showing a stronger humic-like component in March. Woody litter showed greater DOC and DON release potential than herbaceous litter leachates, while litter-derived humic-like DOM was closely associated with a soil humic-like component. The labile SOC pool was mainly associated with vegetation type and electrical conductivity, whereas MAOC was positively associated with soil moisture content and total phosphorus. Overall, the distribution of SOC fractions in coastal riparian habitats is shaped by habitat-specific environmental factors, including vegetative carbon inputs, litter leaching and soil physicochemical properties. This finding is critical for developing targeted management strategies to facilitate SOC accumulation in coastal zones. Full article

Tomato production is highly affected by salt stress conditions, especially under protected cultivation systems using low-quality irrigation water. This study assessed the effects of increasing electrical conductivity (EC) levels of the nutrient solution (2, 4, 6, and 8 dS m⁻¹) on growth, biomass distribution, RGB-based spectral indices, physiological traits, petiole sap composition, and leachate chemistry in tomato plants (Solanum lycopersicum cv. Tiny Tim) cultivated in containers within a bamboo nethouse under tropical conditions. The results obtained reported that increasing salinity significantly reduced fresh and dry biomass (61.72 and 61.55% respectively) across all plant organs, with fruits showing the highest sensitivity. Leaf area index (LAI), SPAD values, leaf nitrogen (N) concentration, leaf relative humidity (LRH), and water uptake also declined progressively under saline conditions. In contrast, root and leaf biomass allocation increased under the highest salinity level. Spectral analyses reported reductions in red and blue RGB components and normalized red and blue index values, while normalized green index increased under higher salinity levels. Petiole sap analysis showed a progressive accumulation of sodium (Na⁺) and chloride (Cl⁻) together with reductions in nitrate (NO₃⁻-N) and potassium (K⁺) concentrations, particularly during the reproductive stage. In contrast, °Brix, calcium (Ca²⁺), and phosphorus (P) concentrations increased under salinity, particularly during the reproductive stage. Leachate analyses confirmed salt accumulation in the substrate and reduced plant water uptake. Overall, petiole sap analysis and RGB-based spectral indices provide a rapid, non-destructive, and cost-effective tool for the early detection of salinity stress in tomato, enabling timely irrigation and fertigation adjustments to improve crop performance and resource-use efficiency under saline conditions. Full article

Sediment internal nutrient loading is a major cause of surface water eutrophication. Adding organic amendments to dredged sediments can improve reuse potential but risks enhancing nutrient leaching. This column study investigated the effect of adding compost (25% v/v), freshwater algae suspension (2.5% v/v), or their combination (22.5% compost + 2.5% algae) to reservoir bottom sediments on the leaching of orthophosphate (PO₄³⁻) and nitrate nitrogen (NO₃-N) under three simulated weekly rainfall events. Unamended sediment served as the control. Compost-amended sediment showed the highest PO₄³⁻ concentrations in the leachates, but these levels stabilized over time, whereas NO₃-N concentrations decreased rapidly. Algae alone reduced both PO₄³⁻ and NO₃-N leaching compared to the control. The combination of compost and algae enhanced the retention of several elements, though it did not fully mitigate phosphorus leaching. Furthermore, this combination effectively decreased overall leachate volume; it was a direct result of the progressive hydration of the organic material, which increased the mixture’s water-holding capacity and thereby reduced percolation. Chemically, compost promoted nitrogen transformation processes (e.g., immobilization or denitrification), while algae likely facilitated nutrient uptake. We conclude that organic amendments play a dual role: compost increases phosphorus availability but stabilizes its release, whereas algae reduce the leaching of both nutrients. The choice of amendment should therefore align with specific water quality targets. Longer-term and field-scale studies are needed to confirm these trends. Full article

Baijiu brewing generates large quantities of wastewater sludge, which presents major disposal challenges but contains abundant organic matter and nutrients, indicating great potential as a soil amendment. This study investigated the soil amendment effects of granulated and coated Baijiu brewing sludge through a 112-day soil column leaching experiment. Sludge particles were coated with sodium alginate (SA), polyvinyl alcohol (PVA), and ester gum (EG), and compared with untreated air-dried sludge (CK₁), uncoated granulated sludge (CK₂), compound fertilizer (F), and a blank control (B). The results showed that coated sludge treatments significantly increased soil leachate pH, total organic carbon, total nitrogen, total phosphorus, and total potassium, and exhibited obvious controlled-release effects on nitrogen, phosphorus, and potassium nutrients compared with uncoated sludge. Soil enzyme analysis indicated that SA treatment increased catalase activity, acid phosphatase activity was generally enhanced by sludge addition, and urease activity was reduced in coated sludge treatments. FTIR and BET analysis showed that both coated and uncoated sludge increased soil-specific surface area and changed soil pore structure. These findings confirm that granulated and coated Baijiu brewing sludge can be used as an effective slow-release soil amendment, and sodium alginate coating shows the most comprehensive improvement in multiple soil health indicators, with high application value for resource utilization of Baijiu sludge and soil quality improvement. Full article

The algae-based landfill leachate (LL) treatment system has been proved promising for nutrient recycling and biomass production at lab- or small-scale photobioreactors (PBRs). However, many assessment tools such as techno-economic analyses (TEAs) usually utilize parameters from small-scale experiments as input data to predict the potential performance of commercial large-scale or full-scale bioreactors. Reliability of using data from lab-scale for commercial large-scale estimation is still uncertain. This study compared the performance of three photobioreactor systems that differed simultaneously in scale, geometry, light intensity, mixing mode, and aeration: 0.125 L small-scale flask, 1 L medium-scale tubular PBR, and 15 L wall-shaped PBR for real LL treatment. The 1 L medium-scale tubular photobioreactor outperformed the other two systems in biomass growth rate and the rates of nitrogen and phosphorus removal, even though all three systems removed nearly all NH₄-N and PO₄-P (≈100%) within two weeks. Possible reasons for this better performance include stronger illumination, a bubbling aeration mode, the reactor shape (which improves mixing), and higher surface area to volume ratio × light intensity. According to these results, using relatively small-scale flask experimental data for predictive analysis of industrial-scale algal systems could be inadequate. In this study, volumetric optical radiation (VOR) serves as a promising preliminary descriptive indicator to reflect the overall performance of an algal-based treatment system. Full article

Livestock manure management remains a significant environmental challenge due to nutrient losses that may contribute to soil and water contamination. This study investigated nitrogen and phosphorus transformations, as well as organic matter stabilisation, in poultry manure subjected to microbial inoculation under controlled laboratory conditions (EI) and long-term field storage (EII). In the laboratory experiment, chicken and turkey manure were treated with denitrifying bacteria, conditioning bacteria, or their combination. The results indicate treatment-dependent differences in ammonium accumulation and nitrate formation in leachates, with the combined microbial inoculum suggesting reduced nutrient mobility compared with the untreated controls. In the field experiment, temporal changes in nitrogen fractions revealed an initial phase of intensive mineralisation, followed by gradual stabilisation of nitrogen forms. Phosphorus concentrations (total phosphorus—P_tot and orthophosphate—PO₄³⁻) decreased over time, suggesting reduced potential for leaching, although the underlying mechanisms likely include immobilisation and redistribution within the manure matrix. Differences in nutrient dynamics between chicken and turkey manure were observed. A humification stabilisation index (HSI) was applied to describe changes in organic matter quality during manure storage, indicating progressive transformation towards more stable forms. However, due to the limited replication and the lack of continuous monitoring of key process parameters, the results should be interpreted as indicative rather than conclusive. Overall, the study suggests that microbial inoculation may influence nutrient transformations and support manure stabilisation processes, highlighting its potential as a complementary strategy in environmentally oriented manure management strategies. Full article

This study evaluates the performance of natural plant-derived coagulants as sustainable alternatives to conventional chemical coagulants in water treatment. Surface water samples were collected from the Meda Ela stream in Karadiyana, Sri Lanka, which is an urban water body impacted by leachate from the Karadiyana dumpsite, industrial discharges, and urban runoff. Grab samples were analyzed for key water quality parameters, including pH, conductivity, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), settleable solids, total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), total nitrogen, and total phosphorus. Several parameters exceeded permissible standards established by the Central Environmental Authority (CEA) of Sri Lanka, including turbidity (35 NTU; limit: 20 NTU), COD (80 mg/L; limit: 15 mg/L), TDS (1000 mg/L; limit: 500 mg/L), and TSS (100 mg/L; limit: 40 mg/L), indicating significant pollution levels. Jar test experiments were conducted to compare the coagulation efficiency of cowpea seeds (75.8%), fenugreek seeds (69.2%), papaya seeds (72.5%), okra pods (84.6%), and Moringa oleifera (drumstick) leaves (87%) with conventional alum (94.2%) at an optimum dosage of 12 mL/L. Among the tested plant-derived coagulants, Moringa oleifera leaves demonstrated the highest turbidity removal efficiency, reducing residual turbidity to 4.54 NTU. A low-cost integrated treatment system incorporating coagulation, flocculation, sedimentation, and filtration using sawdust and cotton wool was developed, achieving average removal efficiencies of 90.13% for turbidity, 88.57% for COD, 83.46% for TDS, and 74.83% for TSS, with all effluent parameters maintained within CEA permissible limits. The results confirm that locally available plant-derived coagulants, particularly Moringa oleifera leaves, offer an effective, environmentally friendly, and economically viable approach for sustainable water treatment, highlighting the potential of nature-based solutions in strengthening climate-resilient water management strategies. Full article

Inland water management is increasingly important under climate change due to the need for landscape-scale water retention, but in situ studies are limited by fluctuating, shallow, and intermittent water cover. This study simulated prolonged waterlogging under controlled laboratory conditions. Four agricultural soils (Calcisol, Arenosol, Chernozem, and Solonetz) were flooded for 40 days using identical 1:5 soil-to-water ratios at two temperature regimes, at 4 and 22 °C. Given that periodic water cover may conflict with agricultural production, particular attention was paid to crop-relevant indicators, including pH, water-soluble salts, and N, P, K. The laboratory simulation revealed significant differences among soil types and between temperature treatments. Elevated Mg concentrations limited the irrigation suitability of leachate derived from Calcisol, with Mg% values ranging from 57 to 64%, exceeding the 50% guideline threshold. Soil buffering capacity controlled phosphorus and potassium dynamics, resulting in stable or slightly increasing AL-soluble nutrient levels, except in low-buffering sandy soils where up to 3–4-fold variability was observed. Reductive conditions developed early in the Calcisol samples, supported by dissolved oxygen saturation values below 20% during the first days of the experiment. Oxygen saturation increased later, only exceeding 60% twice in the cooled Calcisol treatment, while nitrate–ammonium dynamics reflected changing redox conditions. Temperature significantly affected solubility and nutrient mobility, partly through its influence on microbial activity. These findings improve our understanding of inland water–soil interactions and support the development of sustainable, water-retentive land management strategies. Full article

Diesel is a major soil contaminant that poses significant environmental risks, making its removal essential. This study investigates the synergistic application of thermal desorption (TD) and thermal plasma for the remediation of diesel-contaminated soil, while simultaneously converting desorbed contaminants into valuable gaseous products. Artificially contaminated soil (25 g/kg) was treated by TD at 250–300 °C and the resulting off-gas and volatilized diesel were subsequently processed in a thermal plasma system. Soil samples were characterized using CHNS, EDX, FTIR, and TGA/DTG analyses, while gas composition was determined using a gas analyzer. The results demonstrate that TD achieved diesel removal efficiencies of up to 86% at 300 °C and 65% at 250 °C. TD off-gas and volatilized diesel were predominantly converted into synthesis gas (H₂ + CO) in a thermal plasma environment, with H₂ and CO concentrations reaching up to 15.49 vol% and 7.61 vol%, respectively, depending on the plasma-forming gas, carrier gas flow rate, and remediation temperature. Thermal treatment of diesel-contaminated soil significantly altered key physicochemical properties, including reduced organic matter content, increased soil compaction, and temperature-dependent shifts in pH and nitrogen speciation (decreased NO₃⁻-N and increased NH₄⁺-N). These changes were accompanied by enhanced phosphorus availability, indicating substantial thermally induced transformation of soil nutrients. Phytotoxicity assessment using Lepidium sativum in a soil leachate-based bioassay indicated that higher treatment temperature (300 °C) increased toxicity and inhibited plant growth, whereas treatment at 250 °C resulted in lower phytotoxicity. These findings highlight the adaptability of the proposed combination of methods enabling effective soil remediation while supporting energy recovery. Full article

Phosphogypsum (PG) stockpiles pose a persistent threat to regional water environments, yet their differential impacts on surface water and groundwater remain unclear. This study examined the pollution characteristics, sources, mechanisms, and model-predicted trends of PG-derived contaminants in both systems within a representative PG-affected region. Results showed that total phosphorus declined sharply from surface water to groundwater due to soil retention, whereas SO₄²⁻ and F⁻ remained comparable. Nitrogen species accumulated more in groundwater, indicating distinct transport and transformation processes. Arsenic was higher in surface water but rarely exceeded limits. In contrast, lead and manganese were significantly enriched in groundwater, exceeding standards by up to 27- and 11-fold, mainly due to reductive mobilization and subsurface geochemical processes. The Nemerow Index indicated heavy pollution in 35% of surface water and 43% of groundwater samples. Principal component analysis identified PG leachate as the dominant pollution source. Model predictions further suggested that increasing stockpile capacity would intensify contamination and pose long-term environmental risks. This study provided a scientific basis for understanding the distinct pollution mechanisms of PG stockpiles and offered guidance for targeted water environment management in PG-impacted areas. These findings have broader implications for regions globally facing similar challenges from industrial solid waste storage. Full article

This study aimed to evaluate the leaching of nutrients and pathogens following the surface application of pH-modified slurry on sandy soil. Three slurry pH modification strategies—mineral and biological acidification (pH 5) and alkalinization (pH 9.5)—were tested using mineral acids or bases, paper-industry by-products, or combinations of additives. We hypothesized that: (i) acidification increases nitrogen (N) and phosphorus (P) leaching through nutrient solubilization, and (ii) effective sanitization reduces the risk of pathogen leaching. A 24-day column leaching experiment was conducted with slurry applied at 240 kg N ha⁻¹ and four weekly irrigation events. Results indicated that nitrate (NO₃⁻) leaching accounted for less than 15% of the total nitrogen applied; however, acidified slurry significantly increased ammonium (NH₄⁺) leaching by 72%. The combination of H₂SO₄ with sucrose reduced NH₄⁺ and NO₃⁻ leaching, although P leaching exceeded 35% of the total P applied. Sulphur (S) concentrations in leachates ranged from 42.3 to 112.8 mg S kg⁻¹ soil, particularly in treatments involving H₂SO₄ or SO₄²⁻—rich additives such as spent acid. Faecal coliform leaching declined throughout the study, with acidified slurry consistently maintaining levels below the threshold for irrigation water (<100 MPN/100 mL). Regarding nutrient leaching, pH-modified slurry may present a higher risk of N, P and S leaching compared to untreated slurry, which could also be interpreted as an increase in plant nutrient availability. Full article

Soil and water contamination with high nutrient concentrations from swine farms poses a risk to human and animal health. This study investigated the effects of biochar derived from young aromatic coconut husk (CH), coconut shell (CS), and their mixture (CHCS) on nutrient retention in biochar-amended soil columns for variable synthetic swine wastewater (SW) loading based on water use for piglets and fattening stalls. A 0.9 L leaching test column contained 3 g of each biochar type mixed with 300 g of soil. It was loaded daily with synthetic SW for 42 days at loading rates of 30 mL/day (piglet SW) and 60 mL/day (fattening SW). CH-amended soil was then selected to investigate the effect of rainfall rates at 0 (R0), 25 (R25), 70 (R70) and 140 (R140) mL/4 days on soil nutrient retention. Leachate was collected every 7 days to analyze nitrogen and phosphorus concentrations. The results showed that CH-amended soil had the highest retention of total nitrogen (TN) and phosphate among all treatments. For piglet SW, TN retention in CH-amended soil was 1.4–1.6 times higher than with CS and CHCS treatments, probably due to enhanced ammonium retention on exchangeable sites associated with the high cation exchange capacity of CH. High phosphate retention in CH-amended soil was linked to Ca²⁺ release from CH, facilitating phosphate precipitation. Moreover, CH-amended soil at R25 showed the highest ammonium retention but inhibited seed germination. Overall, CH-amended soil effectively retained nutrients and was suitable as a seedling growth medium, except under the R25 rainfall condition. Full article

In this work, iron–phosphorus-based composite biochar (FPBC) was prepared by modification with the leachate of spent LiFePO₄ batteries. The effects of solution pH, dosage, adsorption time, initial concentration, and temperature on the adsorption performance of FPBC were investigated by batch adsorption experiments with Pb(II) and Sb(III) as the target pollutants, and the adsorption mechanism was explored using SEM, BET, XPS, FTIR and XRD characterization. The results indicated that as the initial pH of the solution increased, the removal efficiency of FPBC for Pb(II) gradually increased, while the removal efficiency for Sb(III) remained largely unchanged. The removal of Pb(II) and Sb(III) by FPBC fitted the pseudo-second-order kinetic model and the three-step intraparticle diffusion model, indicating that their removal was primarily controlled by chemical adsorption. Isothermal adsorption studies revealed that FPBC adsorption of Pb(II) better fitted the Langmuir and D-R models, suggesting a monolayer-dominated adsorption process. In contrast, adsorption of Sb(III) fitted the Langmuir, Freundlich, and Temkin models, suggesting a combination of monolayer and multilayer adsorption characteristics. The maximum adsorption capacities of FPBC for Pb(II) and Sb(III) were 312.54 mg·g⁻¹ and 219.20 mg·g⁻¹ at 30 °C, which were approximately 12.85 and 3.37 times those of commercial corn stalk biochar (BC). Thermodynamic analysis confirmed that the removal of Pb(II) and Sb(III) by FPBC was a spontaneous and endothermic process. In addition, FPBC demonstrated strong selective adsorption of Pb(II) in the binary co-adsorption system of Pb(II) and Sb(III). Mechanism studies indicated that Pb(II) removal primarily occurred through co-precipitation, complexation, ion exchange, and electrostatic adsorption, while Sb(III) was mainly adsorbed by FPBC via redox reactions and complexation. Therefore, this work not only provides a low-cost, high-performance adsorbent for the remediation of water contaminated with Pb(II) and Sb(III), but also opens up new avenues for the resource recovery of the leachate of spent LiFePO₄ batteries. Full article