Raw Leachate Research Articles

Occurrence and efficient removal of PFAS from landfill leachates using on-site DTRO systems: A comprehensive analysis across 11 Chinese cities

Per- and polyfluoroalkyl substances (PFAS), known for their persistent toxicity and mobility, pose significant environmental and human health risks. Here we explored the occurrence and efficacy of on-site Double-Pass Reverse Osmosis (DTRO) systems in removing 30 different PFAS from landfill leachates in 11 diverse cities across China. PFAS concentrations in landfill leachate ranged from 938 to 32,491 ng/L, averaging 6,486 ng/L, predominantly comprising short-chain PFAS, notably perfluorobutane sulfonate (PFBS). Notable emerging substitutes like 6:2 fluorotelomer sulfonate, fluorobutane sulfonamide, and 9-chlorohexadecafluoro-3-oxanone sulfonate were also identified. The PFAS levels correlated positively (r2 = 0.79, p < 0.01) with regional economic development, with coastal areas exhibiting higher concentrations than inland regions. The DTRO membrane filtration and ion exchange resin achieved an average removal efficiency of 94 % for ∑30PFAS and even 99.97 % for PFBS (the concentration of PFBS in the raw leachate ranged from 226.36 ng/L to 27,935.61 ng/L, with an average concentration of 4,506.88 ng/L). The Na ion exchange resin had a limited effect on further reducing the PFAS concentration. Our findings not only contribute to the theoretical understanding of PFAS behavior in landfill leachates but also offer a practical engineering applications for global waste management practices.

Sustainable approach for landfill leachate treatment through dielectric barrier discharge/ferrate (DBD/Fe(VI)) enhanced nanofiltration

Landfill leachate, with its high concentrations of persistent organic pollutants, salts, heavy metals, and emerging contaminants, presents significant environmental challenges. This study investigated the combination of dielectric barrier discharge (DBD) and ferrate (Fe(VI)) pretreatment technology in landfill leachate treatment, focusing on its effectiveness in enhancing oxidation performance and mitigating membrane fouling. The results indicated that after DBD/Fe(VI) treatment, TOC and UV254 removal efficiencies increased by 44 % and 67 %, respectively. Additionally, the DBD/Fe(VI) system excelled in removing fluorescent substances and high molecular weight organic compounds, thereby reducing the formation of the cake layer on the nanofiltration membrane. This system enhanced oxidation performance through the synergistic production of reactive intermediates, with Fe(V)/Fe(IV) and •OH being the main active species, O2•-, and 1O2 also contributing significantly. The degradation pathway of perfluorooctanoic acid was investigated by utilizing it as the representative pollutant. Compared to the raw landfill leachate system, the DBD/Fe(VI) increased membrane flux by 104 %, while reducing reversible and irreversible fouling resistances by 67 % and 75 %, respectively. Furthermore, the advantages and practical application potential of the DBD/Fe(VI) system were evaluated from energy consumption, economic cost, and carbon dioxide emissions. The study offers an innovative method for landfill leachate treatment and fouling mitigation.

Effect of landfill leachates on urban soil: A review

The increasing generation of Municipal Solid Waste (MSW) is a significant global concern, with landfills receiving around 1.4 billion tonnes of MSW yearly. Inadequate landfill management contributes to environmental degradation, with landfill leachate being a substantial outcome of MSW decomposition. Leachate contains inorganic nutrients, volatile and dissolved organic molecules and heavy metals and its properties vary depending on waste composition, moisture content and seasonal elements. Heavy metals found in leachate include Pb, Cu, Cr, Ni, Mn, Hg, Fe, Zn and Cd and Emerging Organic Contaminants (EOCs) such as Persistent Organic Pollutants (POPs), Endocrine Disrupting Chemicals (EDC), pharmaceuticals and Personal Care Products (PCPs) are also prevalent. Microplastics (MPs) have been found in raw leachate samples at concentrations ranging from 49.0 ± 24.3 to 507.6 ± 37.3 items/L. Landfill leachate production ranks among the most aggressive pollutants to the environment, particularly to soil and poses a danger of contaminating both surface and groundwater. This review examines the potential impacts of landfill leachate on soil quality and the broader implications of this phenomenon, summarizing recent scientific studies and presenting the direct and indirect effects of leachate on soil based on the literature. Bibliometric analysis of publications in the Scopus database reveals a growing scholarly interest in this topic, with the number of publications in the Science Citation Index (SCI) database increasing dramatically to over 464 articles between 2009 and 2024.

Unraveling drivers of per- and polyfluoroalkyl substances (PFASs) occurrence and removal in leachate: Insights from disposal methods, geo-climate, and biodegradation

Leachate is a substantial reservoir of per- and polyfluoroalkyl substances (PFASs) within the environment. However, comprehensive information on the occurrence and fate of PFASs in leachate, particularly in semi-arid and moderate-elevation regions where PFASs may aggregate, is lacking. Here, 13 legacy PFASs were investigated in leachate from landfills and an incineration plant in such area. PFASs concentrations ranged from 6063 to 43,161 ng·L−1 in raw leachate, influenced by leachate origin, climate, wastewater disposal, and especially bacterial communities. Bacteroidetes and Firmicutes were enriched in raw leachate, while Proteobacteria dominated during leachate treatment processes, possibly due to PFASs selection pressure. In addition, top 20 biomarkers indicated the potential of these bacterial indicators for PFASs detection. Tracing analysis also suggested that PFASs in groundwater may have originated from leachate and effluent from wastewater treatment plants. PFASs levels in groundwater showed a significant correlation with the presence of Brevundimonas, Leptothrix, Malikia, and Sphaerotilus. The pathogenic bacterium Brevundimonas suggested potential human health risks, while Leptothrix, Malikia, and Sphaerotilus may serve as indicators of groundwater contamination. This study is believed to provide insights into how to prevent and control PFASs-related environmental pollution.

Enhanced reducing leachate pollution index through electrocoagulation using response surface methodology

Addressing the urgent need to effectively manage landfill leachate as a harmful flow for human health and the environment, this research investigates how electrocoagulation (EC) processes could alleviate the pollution potential of leachate. So far, no experimental study has been carried out on reducing the leachate pollution index (LPI) under the EC process. For this purpose, in this novel research, the LPI was utilized as a key metric to evaluate the efficiency of the treatment process. Central Composite Design (CCD) as a subset of Response Surface Methodology (RSM) was applied to enhance the LPI parameters decreasing percentage. The data were analyzed by analysis of variance and multivariate regression and 3D plots assessed variable interactions. Under optimal conditions, it showed removal of 97.48 % for COD, 91.42 % for BOD5, 98.52 % for N-NH3, and 91.6 % for TDS. Significant reductions were observed in 94.81 % TKN, 87.20 %, 82.80 %, 96.66 %, and 99.28 %, 99.18 %, and 96.56 % for TKN, Cl−, CN−, As, Cr, Zn, and Ni, respectively. Moreover, the kinetics of COD removal indicated that it follows a first-order model. Thus, based on experimental results, the LPI of raw leachate decreased from 38.06 to 7.22 (81 % decrease) under the EC treatment method. The study indicated that the EC treatment method successfully reduced leachate pollution and met the leachate discharge standard.

Chemical toxicity of leachates from synthetic and natural-based spat collectors on the embryo-larval development of the pearl oyster, Pinctada margaritifera

In French Polynesia, the pearl farming industry relies entirely on collecting natural spat using a shade-mesh collector, which is reported to contribute to both plastic pollution and the release of toxic chemicals. With the aim of identifying more environment-friendly collectors, this study investigates the chemical toxicity of shade-mesh (SM) and alternative materials, including reusable plates (P), a newly developed biomaterial (BioM) and Coconut coir geotextile (Coco), on the embryo-larval development of Pinctada margaritifera. Embryos were exposed during 48 h to four concentrations (0, 0.1, 10 and 100 g L-1) of leachates produced from materials. Chemical screening of raw materials and leachates was performed to assess potential relationships with the toxicity observed on D-larvae development. Compared to the other tested materials, results demonstrated lower levels of chemical pollutants in BioM and no toxic effects of its leachates at 10 g L-1. No toxicity was observed at the lowest tested concentration (0.1 g L-1). These findings offer valuable insights for promoting safer spat collector alternatives such as BioM and contribute to the sustainable development of pearl farming.

Pretreatment for potable reuse: Enhancing the biological removal of 1,4-dioxane from landfill leachate through cometabolism with tetrahydrofuran.

1,4-Dioxane is a probable human carcinogen and a persistent aquatic contaminant. Cometabolic biodegradation of 1,4-dioxane is a promising low-cost and effective treatment technology; however, further demonstration is needed for treating landfill leachate. This technology was tested in two full-scale moving bed biofilm reactors (MBBRs) treating raw landfill leachate with tetrahydrofuran selected as the cometabolite. The raw leachate contained on average 82 μg/L of 1,4-dioxane and before testing the MBBRs removed an average of 38% and 42% of 1,4-dioxane, respectively. First, tetrahydrofuran was added to MBBR 1, and 1,4-dioxane removal was improved to an average of 73%, with the control MBBR removing an average of 37% of 1,4-dioxane. During this period, an optimal dose of 2mg/L of tetrahydrofuran was identified. Tetrahydrofuran was then fed to both MBBRs, where the 1,4-dioxane removal was on average 73% and 80%. Cometabolic treatment at the landfill significantly reduced the concentration of 1,4-dioxane received from the landfill at a downstream wastewater treatment and indirect potable reuse facility, reducing the load of 1,4-dioxane from 44% to 24% after the study. PRACTITIONER POINTS: Cometabolic degradation of leachate 1,4-dioxane with THF in MBBRs is a feasible treatment technology and a low-cost technique when retrofitting existing biological treatment facilities. The MBBRs can be operated at a range of temperatures, require no operational changes beyond THF addition, and operate best at a mass ratio of THF to 1,4-dioxane of 24. Source control of 1,4-dioxane significantly reduces the concentration of 1,4-dioxane in downstream wastewater treatment plants and potable reuse facilities.

Seasonal Survey of Bacterial Species and their Bioremediation Potentials in Leachates from a Nigerian Municipal Solid Waste Dumpsite

Myriads of microorganisms present in dumpsite leachates produce varieties of extracellular enzymes that can degrade toxic compounds to innocuous products. The present study involved a seasonal survey of bacterial species and their bioremediation potentials in leachate from the Ikueniro open solid waste dumpsite situated in Uhunmwode Local Government Area, Edo State, Nigeria. Bacterial isolation and enumeration of the leachate samples was carried out using pour plate technique. Phenotypic techniques and 16S rRNA gene analysis identified the bacterial isolates. The bacterial mastermix for bioremediation of the leachate consisted of a consortium of bacterial strains isolated from leachate discharging from the Ikhueniro dumpsite. The bioremediation efficiency of the leachate was deduced by measurement of heavy metals and other chemical analytes using standard methods prescribed by the American Public Health Association. The bacterial species isolated from Ikueniro dumpsite such as Bacillus licheniformis strain EGBON &amp; OKORIE 103 and Klebsiella aerogenes strain EGBON &amp; OKORIE 108 were deposited in the United States NCBI GenBank. A consortium of these bacterial strains served as inocula for the bioremediation setup. A huge removal of ammonia from the leachate was observed during the 28-day bioremediation experiment, amounting to a mean bioremediation efficiency of 80.65%. The removal of the heavy metals from the raw leachate by the bacterial mastermix in increasing order was as follows: nickel&lt;copper&lt;zinc&lt;lead&lt;iron&lt;cadmium&lt;arsenic&lt;mercury. Bioremediation of the leachate using indigenous bacteria promises to be an effective tool for management of toxicants from leachates of open solid waste dumpsites.

Landfill leachate treatment using sequential natural zeolite adsorption and peroxymonosulfate activated by UV/Fe2+ system: Effects of main operating parameters and application of fluorescence EEM to monitor organic matters’ transformation

The significant increase in global Landfill Leachate is a pressing challenge directly linked to the growing global population. Among the strategies for landfill leachate treatment, advanced oxidation processes using sulfate radical (SR-AOP) have gained considerable interest, despite the challenge of nitrate generation during ammonia oxidation. This study introduces a sequential treatment method that combines adsorption and a UV/PMS/Fe2+ system to assess its impact on COD (Chemical Oxygen Demand) and ammonia removal efficiencies.The results show that the sequential process achieves optimal COD and ammonia removal rates of 88 % and 88.3 % respectively. The increase in UV254 absorbance removal during the adsorption phase indicates the removal of UV quenching substances (UVQS), supporting the effectiveness of using adsorption as a pretreatment for the UV-assisted systems (UV/PMS/Fe2+). Additionally, analysis using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) reveals that the adsorption treatment before the SR-AOP process not only enhances COD and ammonia removal efficiencies, but also eliminates heavy metals such as vanadium (V), titanium (Ti), zinc (Zn), and aluminum (Al) present in leachate.Moreover, the higher BOD/COD ratio suggests improved biodegradability of the effluent. When compared to other systems at optimal conditions, the sequential adsorption and UV/PMS/Fe2+ systems demonstrate superior performance, focusing on removing refractory matter and reducing ammonia content, especially effective at a pH level of 7.25. Analysis using Excitation-Emission Matrix (EEM) shows a shift from primary peaks in raw leachate spectra associated with humic and fulvic acid-like compounds to lower-intensity peaks from fulvic-like small molecule materials in the treated effluent.

Alterations in viscera histoarchitecture and organosomatic index as biomarkers of toxicity induced by Aba-Eku and Olusosun solid waste landfill leachates in Rattus norvegicus.

Solid waste disposal generates leachate, a mixture of deleterious chemical, physical and microbial contaminants, which poses risk to human and wildlife health. Leachate toxicity on relative organ weight and histopathology of important viscera in mammalian body is scarce. Leachate induced toxic effects on organosomatic indices and histopathology of vital mammalian organs were investigated. Wister rats were orally exposed to 1 - 25 % of raw and simulated leachates from Aba-Eku and Olusosun landfills for 30 days. At post-exposure, organosomatic index and histoarchitectural assessment of major viscera (heart, spleen, thymus and lungs) were conducted. The physico-chemical and organic compositions of the leachates were analysed using standard protocol. The tested leachates decreased weekly and terminal body weights, and altered organosomatic index of examined viscera in rats. The histoarchitecture of the investigated viscera revealed pathologies that ranged from mild to severe degeneration, cellular infiltration, haemorrhage, congestion, necrosis, disorganization of tissues and vacuolations. Others include increased histiocytes within the bronchial associated lymphoid, lymphoid depletions, haemosiderin deposits and apoptosis were observed in the examined viscera. Physico-chemical analysis of the leachates showed different concentrations of toxic metals, PAHs and PCBs that were higher than national and international permissible limits allowed in wastewaters. The physico-chemical compositions of the leachates are capable of eliciting the observed alterations in organosomatic indices and histopathological lesions in mammalian viscera. Xenobiotic components of the leachates possibly generated free radicals and/or directly disrupted the organ architectures. These findings suggest health risk to wildlife and human population exposed to emissions from waste landfills.

Antifungal activity of heat-treated wood extract against wood decay fungi

Using heat treatment for wood protection has been driven to maturity, but the role of heat-treated wood extracts in decay resistance has lacked attention. To assess the potential of heat-treated wood extract for wood preservation, the antifungal activity of the extract against wood decay fungi and the effects of the extract on fungal wood degrading enzyme activity and cell membrane integrity were tested. Small shavings generated during the processing of larch (Larix gmelinii (Rupr.) Kuzen) were heat-treated and extracted. The antifungal activity of extract against wood decay fungi and decay resistance of extract impregnated wood were tested to assess their potential. The effect of extracts on the enzyme activity of the white-rot fungus, Trametes versicolor (L.) Lloyd and the brown-rot fungus, Gloeophyllum trabeum (Pers.: Fr.) Murr. for wood degradation was assessed by detecting the activity of cellulose, hemicellulose, and ligninase of fungi incubated with extract. The effect of extracts on the integrity of cell membranes of fungi was assessed by staining with propidium iodide (PI) and the leakage detection of nucleic acid and protein in fungi after exposure to extract. The toxicity to freshwater luminescent bacteria (Vibrio qinghaiensis sp. -Q67) and mouse macrophages (RAW264.7) of the extract impregnated wood leachate was tested and compared with the leachate of the raw wood. The results denoted that the decay resistance of poplar (Populus tomentosa Carr.) wood could be improved by heat-treated larch wood extract, and the effect of the extract impregnated wood leachate on Q67 and RAW264.7 was the same as that of raw wood leachate. The extract inhibited ligninase activity (only for T. versicolor), cellulase activity, and respiratory metabolism of tested fungi, and impaired the membrane integrity. The study identified a potential wood preservative.

Optimization of ultrasonication and alkalinization as pretreatment methods for leachate co-digested with food waste toward maximum synergistic effects

Anaerobic co-digestion (AcoD) of food waste (FW) and landfill leachate has shown promising results in enhancing the methane yield. However, leachate includes toxic and refractory compounds that may impact the decomposition process. In this research, co-digested leachate was pretreated using ultrasonication and alkalinization to manipulate its characteristics toward improved synergism with FW. Experimental optimization was conducted through biochemical methane potential (BMP) assays to identify the optimum operating conditions of the pretreatment methods. The study evaluated the synergistic effects of co-digestion with raw and pretreated leachate on enhancing the performance in terms of feedstock solubilization and methane production. The BMP test demonstrated that alkalinization and ultrasonication improved the total methane generation by 35% and 27%, respectively, yielding around 397 and 375 mL CH4 per g of volatile solids. Moreover, ultrasonication and alkalinization enhanced the synergistic effects by 28% and 36%, respectively, compared to co-digestion with untreated leachate. Optimization by response surface methodology revealed that maximum performance could be achieved with leachate sonication at 212 W for 37.5 min or augmenting 788 g NaOH per kg of volatile solids. Kinetic and statistical models were derived to simulate and assess the impacts of the pretreatment parameters on the AcoD process. The results indicated that the ultrasonication energy had a higher influence on total solubility and methane production than alkaline dosage. Additionally, energy efficiency analyses were performed to examine the overall viability of the examined management approach and found that alkalinization increased the net energy efficiency by 23%, whereas ultrasonication was inefficient within the examined laboratory conditions despite the improved performance. The findings support an integrated organic waste management system where separated FW is co-treated with landfill leachate.

Plastic takeaway food containers may cause human intestinal damage in routine life usage: Microplastics formation and cytotoxic effect

The microplastics and organic additives formed in routine use of plastic takeaway food containers may pose significant health risks. Thus, we collected plastic containers made of polystyrene, polypropylene, polyethylene terephthalate, polylactic acid and simulated two thermal usages, including hot water (I) and microwave treatments (M). Nile Red fluorescence staining was developed to improve accurate counting of microplastics with the aid of TEM and DLS analysis. The quantity of MPs released from thermal treatments was determined ranging from 285.7 thousand items/cm2 to 681.5 thousand items/cm2 in containers loaded with hot water with the following order: IPS>IPP>IPET>IPLA, while microwave treatment showed lower values ranging from 171.9 thousand items/cm2 to 301.6 thousand items/cm2. In vitro toxicity test using human intestinal epithelial Caco-2 cells indicated decrease of cell viability in raw leachate, resuspended MPs and supernatants, which might further lead to cell membrane rupture, ROS production, and decreased mitochondrial membrane potential. Moreover, the leachate inhibited the expression of key genes in the electron transport chain (ETC) process, disrupted energy metabolism. For the first time, we isolate the actually released microplastics and organic substances for in vitro toxicity testing, and demonstrate their potential impacts to human intestine. SynopsisPlastic take-out containers may release microplastics and organic substances during daily usage, both of which can cause individual and combined cytotoxic effects on human colon adenocarcinoma cells Caco-2.

The nematode Caenorhabditis elegans enhances tolerance to landfill leachate stress by increasing trehalose synthesis.

The burgeoning issue of landfill leachate, exacerbated by urbanization, necessitates evaluating its biological impact, traditionally overshadowed by physical and chemical assessments. This study harnesses Caenorhabditis elegans, a model organism, to elucidate the physiological toxicity of landfill leachate subjected to different treatment processes: nanofiltration reverse osmosis tail water (NFRO), membrane bioreactor (MBR), and raw leachate (RAW). Our investigation focuses on the modulation of sugar metabolism, particularly trehalose-a disaccharide serving dual functions as an energy source and an anti-adversity molecule in invertebrates. Upon exposure, C. elegans showcased a 60-70% reduction in glucose and glycogen levels alongside a significant trehalose increase, highlighting an adaptive response to environmental stress by augmenting trehalose synthesis. Notably, trehalose-related genes in the NFRO group were up-regulated, contrasting with the MBR and RAW groups, where trehalose synthesis genes outpaced decomposition genes by 20-30 times. These findings suggest that C. elegans predominantly counters landfill leachate-induced stress through trehalose accumulation. This research not only provides insights into the differential impact of leachate treatment methods on C. elegans but also proposes a molecular framework for assessing the environmental repercussions of landfill leachate, contributing to the development of novel strategies for pollution mitigation and environmental preservation.

Design and evaluation of slow sand and UV filters for effective nutrient recycling in closed soilless cultivation

Nutrient and water use efficiency can be improved in soilless cultivation systems by recirculating the leachate. However, untreated leachate contains particulate matter that may clog drip emitters and root pathogens which can pose a threat to the crop health if reintroduced into the system. To address this issue, an ultraviolet (UV) filter was developed to complement the slow sand filter to enhance its treatment efficiency in removing root pathogens. The experiment was conducted during 2019 and 2020 at Punjab Agicultural University, Ludhiana, Punjab to assess the effectiveness of the UV filter in removing pathogens, specifically Dickey zeae and Xanthomonas, from the leachate in a closed soilless cultivation system. Pre and post-treatment measurements were made 40 days after transplanting (DAT) and 80 DAT to evaluate the efficiency of the UV filter. The results revealed that combined UV and slow sand filters substantially treated the raw leachate. At 40 DAT, the pathogen removal efficiency was 94.8%, while it was 92% at 80 DAT. The findings highlight the importance and effectiveness of using the UV filter as an additional treatment step in closed soilless cultivation systems with significant improvement in the overall removal efficiency of root pathogens from the leachate.

The Performance of Iron Nanocomposites as Persulfate Activators in Permeable Reactive Barrier Technology for Treatment of Landfill Leachate

Landfill leachate contains a large organic load and a wide spectrum of pollutants, and it needs appropriate treatment to reduce the severity of these contaminants. Therefore, the present study aimed to remove chemical oxygen demand (COD) and ammonia (NH3 ) as target contaminants from the landfill leachate. To this end, the zero-valent iron nanofibers/reduced ultra-large graphene oxide (ZVINFs/rULGO) and converter sludge (CS) were used as persulfate (PS) activators in permeable reactive barrier (PRB) technology for removing COD and NH3 . The Box–Behnken design (BBD) was employed to determine the possibility of using each activator and optimize three parameters: activator, pore volume (PV), and flow (mL/min) using target contaminants. In the Batch process, the effects of pH, activator concentration, and PS/COD mass ratio on COD removal were examined. The BBD experiments provided a satisfactory predictive model, indicating that ZVINFs/rULGO is superior to CS when used as activators of PS in PRB technology. The biochemical oxygen demand (BOD5 )/COD ratio increased from 0.24 in raw leachate to 0.67 in treated leachate, and leachate toxicity was reduced by more than 85%. Additionally, the ZVINFs/rULGO and CS contributed to the activation of PS.

Boosting synergistic recovery of ammonia nitrogen and phosphate from phosphorus chemical wastewater by co-pyrolyzing the biomass and magnesite

In this study, biomass was co-pyrolyzed with the low-cost magnesite to prepare nano-MgO loaded biochar (n-MgO/biochar) composites for the simultaneous recovery of NH4+-N and PO43--P consisting in wastewater. It was found from the outcomes that the addition of biomass effectively reduced the pyrolysis temperature of magnesite, and the dispersion of biochar promoted the reactive activation of nano-scale MgO. The nano-MgO could provide Mg2+ and OH− simultaneously for the efficient recovery of NH4+-N and PO43--P. At a pH of approximately 9 and an N/P/Mg molar ratio of 1:2:1.5, the NH4+-N and PO43--P in the experimental wastewater were recovered by 93.7 % and 84.8 %, respectively. Mechanism analysis revealed that chemical adsorption, with the main product being MgNH4PO4·6H2O, predominantly controlled the recovery process. Furthermore, n-MgO/biochar demonstrated a successful recovery of NH4+-N and PO43--P consisting in the complex phosphogypsum leachate. What’s more, NaH2PO4, n-MgO/biochar/P, and raw phosphogypsum leachate could all serve as effective phosphorus sources for recovering NH4+-N consisting in nitrogenous wastewater with phosphorus deficiency. Conclusively, this study provides an alternative method for the simultaneous recovery of NH4+-N and PO43--P consisting in the wastewater.

Electrochemical-coupled sulfur-driven autotrophic denitrification for nitrogen removal from raw landfill leachate: Evaluation of performance and mechanisms

The cost-effective and environment-friendly sulfur-driven autotrophic denitrification (SdAD) process has drawn significant attention for advanced nitrogen removal from low carbon-to-nitrogen (C/N) ratio wastewater in recent years. However, achieving efficient nitrogen removal and maintaining system stability of SdAD process in treating low C/N landfill leachate treatment have been a major challenge. In this study, a novel electrochemical-coupled sulfur-driven autotrophic denitrification (ESdAD) system was developed and compared with SdAD system through a long-term continuous study. Superior nitrogen removal performance (removal efficiency of 89.1 ± 2.5 %) was achieved in ESdAD system compared to SdAD process when treating raw landfill leachate (influent total nitrogen (TN) concentration of 241.7 ± 36.3 mg-N/L), and the effluent TN concentration of ESdAD bioreactor was as low as 24.8 ± 5.1 mg-N/L, which meets the discharge standard of China (< 40 mg N/L). Moreover, less sulfate production rate (1.3 ± 0.2 mg SO42−−S/mgNOx−−N vs 1.7 ± 0.2 mg SO42−−S/mgNOx−−N) and excellent pH modulation (pH of 6.9 ± 0.2 vs 5.8 ± 0.4) were also achieved in the ESdAD system compared to SdAD system. The improvement of ESdAD system performance was contributed to coexistence and interaction of heterotrophic bacteria (e.g., Rhodanobacter, Thermomonas, etc.), sulfur autotrophic bacteria (e.g., Thiobacillus, Sulfurimonas, Ignavibacterium etc.) and hydrogen autotrophic bacteria (e.g., Thauera, Comamonas, etc.) under current stimulation. In addition, microbial nitrogen metabolic activity, including functional enzyme (e.g., Nar and Nir) activities and electron transfer capacity of extracellular polymeric substances (EPS) and cytochrome c (Cyt-C), were also enhanced during current stimulation, which facilitated the nitrogen removal and maintained system stability. These findings suggested that ESdAD is an effective and eco-friendly process for advanced nitrogen removal for low C/N wastewater.

Microbiology of post-fermentation leachate

Using post-fermentation leachate as fertilizer is a good alternative and solution to the problem of waste at wastewater treatment plants and contains the principles of sustainable development. Leachate from anaerobic treatment of sewage sludge contains valuable elements such as phosphorus, nitrogen and potassium, which can improve soil properties. The production of liquid fertilizer minimizes the negative impact of leachate on the main biological stream in the WWTP and improves the energy efficiency of the entire wastewater treatment system. This transfers into the operating costs of the facility. When thinking about the agricultural use of digestion leachate and its introduction into the environment, a very important issue is its microbiological contamination. The purpose of the conducted research was to determine the microbiological quality of digestion leachates from municipal wastewater treatment plants and to determine the parameters of their hygienization. The number of bacteria in raw leachate is indicative of a sanitary risk in the case they are used in agriculture as fertiliser. Heating the leachate at 60°C for 15 minutes produces an effect comparable to that achieved by heating the leachate to 70°C. The sonication process itself did not affect the better temperature effect. Heating the leachate for 20 minutes after prior sonication for 20 minutes does not result in the complete elimination of microflora.

Leachates from pyroplastics alter the behaviour of a key ecosystem engineer

As plastic pollution is increasing rapidly, novel forms of plastic litter have been lately described. One of most recently described type of plastic litter is pyroplastic, i.e. an amorphous matrix derived from the burning of manufactured plastics. We surveyed 12 locations along northern French shores where mussel reefs are a predominant feature. We recorded pyroplastic items at six sites (average weight of 3.34g) mainly made of polyethylene. We then tested the effects of exposure to raw and beached pyroplastic leachates on adaptive behavioural traits of the mussel Mytilus edulis, a key ecosystem engineer. The ability of mussels to move and aggregate were significantly affected by pyroplastic leachates, particularly those from beached pyroplastics. Additionally, the strength of the effects was polymer-dependent, with PE having a more pronounced effects than PP. Our results provide the first evidence that pyroplastics have more severe impacts on living organisms than those triggered by non-burnt plastics.