Leachate Research Articles

Development of an integrated fixed-film activated sludge (IFAS) reactor treating landfill leachate for the biological nitrogen removal through nitritation-denitritation

The current work investigated the performance of an Integrated Fixed-Film Activated Sludge Sequencing Batch Reactor (IFAS-SBR) for Biological Nitrogen Removal (BNR) from mature landfill leachate through the nitritation-denitritation process. During the experimental period two IFAS-SBR configurations were examined using two different biocarrier types with the same filling ratio (50%). The dissolved oxygen (DO) concentration ranged between 2 and 3 mg/L and 4–6 mg/L in the first (baseline-IFAS) and the second (S8-IFAS) setup, respectively. Baseline-IFAS operated for 542 days and demonstrated a high and stable BNR performance maintaining a removal efficiency above 90% under a Nitrogen Loading Rate (NLR) up to 0.45 kg N/m3-d, while S8-IFAS, which operated for 230 days, was characterized by a limited and unstable BNR performance being unable to operate sufficiently under an NLR higher than 0.20 kg N/m3-d. It also experienced a severe inhibition period, when the BNR process was fully deteriorated. Moreover, S8-IFAS suffered from extensive biocarrier stagnant zones and a particularly poor sludge settleability. The attached biomass cultivated in both IFAS configurations had a negligible content of nitrifying bacteria, probably attributed to the insufficient DO diffusion through the biofilm, caused by the low DO concentration in the liquid in the baseline case and the extensive stagnant zones in the S8-IFAS case. As a result of the high biocarrier filling ratio, the S8-IFAS was unstable and low. This was probably attributed to the mass transfer limitations caused by the biocarrier stagnant zones, which hinder substrate and oxygen diffusion, thus reducing the biomass activity and increasing its vulnerability to inhibitory and toxic factors. Hence, the biocarrier filling fraction is a crucial parameter for the efficient operation of the IFAS-SBR and should be carefully selected taking into consideration both the media type and the overall reactor configuration.

Statistical investigation of climate and landfill age impacts on Kupferberg landfill leachate composition: one-way ANOVA analysis

This study investigated seasonal variations in the physico-chemical properties of leachate from the Kupferberg landfill site, examining the influence of landfill age and climatic factors. Data provided by the Windhoek Municipality during the years 2017 to 2022 facilitated the exploration of critical concerns related to groundwater protection and human health. Guided by two research questions and anchored in hypotheses tested at a 95% confidence level, the study employed Statistical Packages for Social Scientists (SPSS) for analysis.Significant temperature variations were observed across years [F (5, 21) = 4.493, p < 0.05], indicating a substantial relationship between landfill age and seasonal variations in leachate physico-chemical properties. Further ANOVA tests revealed temperature trends impacting leachate parameters, such as organic content and pH. While COD displayed a declining trend with landfill age, inorganic components like Cl- and alkalinity exhibited no distinct age-related pattern.Wet seasons demonstrated higher EC and Cl--mean values than dry seasons, correlating with elevated COD levels. The study underscored the incremental rise in parameter values over time and during the rainy season, attributed to solid waste degradation and rainwater percolation. Notably, climatic conditions significantly influenced seasonal variations in leachate physico-chemical properties (p < 0.05). Based on this outcome, null hypothesis 1 was rejected. The second null hypothesis was also rejected because climatic conditions do influence the seasonal variations in physico-chemical properties. These findings are crucial for emphasizing the need for effective leachate management strategies and providing valuable insights for arid regions. Future research can expand on a national scale, employing one-way ANOVA tests on other landfills in Namibia, and engaging local communities for comprehensive data collection on cross-contamination.

Combined treatment of domestic wastewater with landfill leachate using aerobic moving bed bioreactor (AeMBBR)

In this study, the treatment of landfill leachate (LFL) and domestic wastewater using an aerobic moving bed biofilm reactor (AeMBBR) was investigated. AeMBBR was filled with 30 % (v:v) biocarrier material (Kaldnes K1). The effect of different hydraulic retention times (HRTs) (6- 24 h) at a constant dissolved oxygen (DO) of 3.2 mg/L was investigated for system optimization. AeMBBR was successfully operated for LFL and domestic wastewater treatment corresponding to 94 %, and 78 % ammonium nitrogen (NH4-N) and total organic carbon (TOC) removals, respectively. Additionally, Proteobacteria (66%) have been identified as the predominant culture in the biofilm layer, which plays an important role in the co-treatment of domestic wastewater and LFL. Considering the results obtained; it was found that a significant amount of NH4-N was successfully removed.

Ammonium oxidation from concentrated synthetic wastewater and landfill leachate using partial nitritation in sequencing batch reactor.

Partial nitritation (PN) is a novel treatment for nitrogen removal using aerobic ammonium oxidation with reduced oxygen requirements compared to conventional nitrification. This study evaluated the performance of the PN process and the factors influencing nitrogen removal from landfill leachate. During the reactivation of biomass, the results showed 70% ammonium removal, but only 20% total nitrogen removal. Further analysis showed that low nitrite accumulation and high nitrate production promoted the growth of nitrite-oxidizing bacteria (NOB). The ammonium removal activity after soaking the cultivated biomass in synthetic water and leachate was measured to be 0.57, 0.1, 0.17, and 0.25 g N•g VSS-1•d-1 for synthetic wastewater and leachate soaking for synthetic wastewater, 12 h, 3days, and 7days, respectively. The study found abundant ammonium-oxidizing bacteria (AOB) and NOBs in biomass soaked in synthetic wastewater. However, soaking in leachate promoted AOB growth and inhibited NOB growth making leachate suitable for PN. PRACTITIONER POINTS: The study found that with a longer leachate-soaking period for biomass, ammonium removal activity increases, which in turn increases ammonium conversions during the PN process. Ammonium-oxidizing bacteria (AOB) can acclimate to landfill leachate substrate and grow with a longer soaking period. Nitrite-oxidizing bacteria (NOB) were inhibited by landfill leachate substrate, which is beneficial for nitrite accumulation. Anabolized DO can convert nitrite to nitrate rapidly, which results in higher nitrate accumulation compared to nitrite accumulation. Hence, the DO level has to be sufficiently low to prevent nitrite oxidation and nitrate accumulation.

Recent Advances in Biofiltration for PPCP Removal from Water

As emerging pollutants, pharmaceuticals and personal care products (PPCPs) in water have attracted more and more attention because of their harmfulness to the ecosystem and human health. Due to the perpetual input from sewage/wastewater effluents, landfill leachates, urban/agricultural runoff, etc., PPCPs in the aquatic environment are generally “pseudo-persistent”. Conventional filtration in the water treatment process cannot effectively remove PPCPs, while biofiltration, a synergistic combination of adsorption and biodegradation, is an effective upgrade method that has received great attention and application in recent years. This paper systematically reviewed the principle of biofiltration and its efficiency in the removal of PPCPs. The important operational parameters influencing biofiltration performance such as filter media, temperature, backwash conditions, empty bed contact time, etc. were summarized. In addition, the limitations and prospects of the current research on biofiltration were also pointed out.

Antibiotic Indexing and Heavy Metal Reduction Potential of Four Multi-metal Tolerant Bacterial Strains in Real-Time Sanitary Landfill Leachate Matrix.

Sanitary leachate from urban landfills is known to be contaminated with multi-metals and residual antibiotics. Current research edges on exploring the multi-metal and antibiotic sensitivity profile of four indigenous strains, "Brevibacillus spp. Leclercia spp. Pseudescherichia spp., and Brucella spp." isolated from the leachate of a sanitary landfill in a tropical region. Indigenous isolates were observed to be antibiotic-resistant and have high tolerance against eight of the ten tested metals except Cu & Co. It was observed that interaction with multi-metals in laboratory conditions significantly altered the cell morphology of bacterial strains, as depicted by Scanning Electron Microscope. Metal adsorption onto the microbial surface was deciphered through Electron Dispersive Spectrometer analysis and elemental mapping. Application of isolated strains into real-time leachate matrix exhibits a complete reduction of Ag and Zn and for other tested metals. Their response to these toxicants may facilitate their application in bioremediation-based treatment technologies for urban landfill leachate.

Analysis of the Influence of Tambakrigagadung Landfill Leachate Characteristics on Water Quality and Heavy Metal Contamination of Reservoirs, Tikung District, Lamongan Regency

The Final Disposal Site (TPA) of Tambakrigadung Village, Lamongan Regency, implements a semi-sanitary landfill system in which waste processing still piles up piles of waste with soil for a certain period, causing a foul odor due to the leachate that collects. Leachate that is not managed correctly is feared to flow into reservoirs as irrigation and productive land that is used by local communities for rice fields or ponds around the Tambakrigadung TPA so that it can disrupt workers, reduce the quality and yield of rice fields, and affect the development of pond fish around the Tambakrigadung landfill. This research aims to test the quality of reservoir water, which refers to the leachate water quality standards of PermenLHK RI No. P.59 Tahun 2016. It analyzes the influence of leachate on reservoir water around Tambakrigadung. The method used in this research is grab sampling. Analysis of pH, BOD, COD, and TSS parameters using simple linear regression quantitative analysis. Quantitative parameter analysis shows that TPA Tambakrigadung leachate influences the pH and TSS parameters of reservoir water in Tikung District, Lamongan Regency, which is indicated by a significance value of &lt;0.05. The analysis of heavy metal parameters shows that the leachate does not meet quality standards, with a total N of 187.7 ppm and cadmium of 0.15 ppm. The mercury parameter meets quality standards, namely 0.00065 ppm. Meanwhile, heavy metal parameters in reservoir water have met quality standards based on PP No. 22 of 2021.

Integrated Heterogeneous Electro-Fenton Process and Constructed Wetland for the Treatment of Stabilized Landfill Leachate

Treatment of stabilized landfill leachate is a great challenge due to its poor biodegradability. Present study made an attempt to treat this wastewater by combining electro-Fenton (E- Fenton) and constructed wetland (CW). E-Fenton treatment was applied prior to Constructed wetland process to enhance the biodegradability of leachate, which will be beneficial for the subsequent biological process. This study also investigates the efficiency of Magnetite (Fe3O4) nanoparticles as a heterogeneous catalyst in E-Fenton process. The objectives of this study are to synthesize chitosan to obtain magnetite nanoparticles via iron ions assembly and to characterize the synthesized nanoparticles using SEM, XRD and FTIR analysis to assess its nature. The effects of initial pH, catalyst dosage, applied voltage and electrode spacing on Chemical Oxygen Demand (COD) removal efficiency were analysed to determine the optimum conditions. Heterogeneous E-Fenton process gave 84.29% COD removal at catalyst dosage of 50 mg/L, pH 2, electrode spacing 3 cm, voltage 5 V and electrode area 25 cm2. The proficiency of utilizing eggshells as a media in constructed wetlands was evaluated for the treatment of wastewater previously subjected to electro-Fenton treatment. And it was found that combined E-Fenton and biological treatment (CW) resulted in overall COD removal of 95.79%, bringing down the final COD to 292 mg/L. Thus, the combination of the E-Fenton process followed by a biological process is efficient for complete mineralization with lower operational cost.

A multi-criteria approach to test and evaluate the efficiency of two composting systems under two different climates

ABSTRACT The selection of the appropriate composting system, climate conditions, and duration of the composting process are important parameters for municipal solid waste composting. Therefore, this research aimed to design, test, and evaluate two different static composting systems under two different climate regions, Palestine and India, following a multi-criteria approach. A forced-aeration composting system was designed for use in Palestine, and a naturally aerated one was used in India. Three experiments were conducted, two of them in Palestine and one in India. The operational parameters were controlled and monitored during the composting process, while the physio-chemical and biological parameters were tested to evaluate the compost end quality. The results showed that both systems provide good efficiency toward formation of final compost (39–43 days in Palestine, and 31 days in India), and the average materials’ volume reduction was almost 60%. The physio-chemical analysis showed that most of the parameters comply with the threshold limits specified by the Palestinian Standards Institution (PSI) and Indian Fertilizer Control Order (FCO) except for minor deviations. Both systems provided a high fertility index (4.3, 4.7, and 4.8), and a high clean index (4.6, 5.0, and 4.7). However, the results of the biological parameters showed that all the experiments met PSI, but none of them met FCO, suggesting that the outer edges of the composting system didn’t heat enough to inactivate pathogenic microbes, therefore, developing the system by adding turning option could overcome this shortcoming. It was concluded that the forced aeration system is suitable for Palestine, while the natural aeration system is suitable for India. Implications: Municipal solid waste management is facing technical and financial challenges worldwide due to the increasing generation of solid waste following the population growth. The current improper management of this waste stream through landfilling is adding pressure on the environment as a result of methane emissions and landfill leachate. Therefore, composting of the organic fraction through selection of an appropriate composting system can solve many waste management problems and contribute to environmental sustainability. This research focuses on design, test and evaluate two composting systems in two regions with different climatic conditions, Palestine and India as both are facing waste management problems. The outcome of this research optimized the composting process which can be replicated and scaled up in other countries worldwide with similar climatic conditions.

Microplastics Biodegradation by Estuarine and Landfill Microbiomes

Plastic pollution poses a worldwide environmental challenge, affecting wildlife and human health. Assessing the biodegradation capabilities of natural microbiomes in environments contaminated with microplastics is crucial for mitigating the effects of plastic pollution. In this work, we evaluated the potential of landfill leachate (LL) and estuarine sediments (ES) to biodegrade polyethylene (PE), polyethylene terephthalate (PET), and polycaprolactone (PCL), under aerobic, anaerobic, thermophilic, and mesophilic conditions. PCL underwent extensive aerobic biodegradation with LL (99 ± 7%) and ES (78 ± 3%) within 50–60 days. Under anaerobic conditions, LL degraded 87 ± 19% of PCL in 60 days, whereas ES showed minimal biodegradation (3 ± 0.3%). PE and PET showed no notable degradation. Metataxonomics results (16S rRNA sequencing) revealed the presence of highly abundant thermophilic microorganisms assigned to Coprothermobacter sp. (6.8% and 28% relative abundance in anaerobic and aerobic incubations, respectively). Coprothermobacter spp. contain genes encoding two enzymes, an esterase and a thermostable monoacylglycerol lipase, that can potentially catalyze PCL hydrolysis. These results suggest that Coprothermobacter sp. may be pivotal in landfill leachate microbiomes for thermophilic PCL biodegradation across varying conditions. The anaerobic microbial community was dominated by hydrogenotrophic methanogens assigned to Methanothermobacter sp. (21%), pointing at possible syntrophic interactions with Coprothermobacter sp. (a H2-producer) during PCL biodegradation. In the aerobic experiments, fungi dominated the eukaryotic microbial community (e.g., Exophiala (41%), Penicillium (17%), and Mucor (18%)), suggesting that aerobic PCL biodegradation by LL involves collaboration between fungi and bacteria. Our findings bring insights on the microbial communities and microbial interactions mediating plastic biodegradation, offering valuable perspectives for plastic pollution mitigation.

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.

Deteksi Konsentrasi Fe, Cu, Zn dan Pb Air Sungai dan Ikan yang Tercemar Air Lindi di Bandar Lampung Dengan Menggunakan SSA

Leachate is a pollutant produced by landfills which can pollute the aquatic environment. This will have an impact on fish that live in waters contaminated with leachate and if consumed by the public it will harm health. The toxic effects of leachate are caused by the content of toxic chemicals, one of which is heavy metals. The aim of this research was to determine the concentrations of Fe, Cu, Zn and Pb in Bakung landfill leachate, Sukamaju river water and fish meat. Bakung landfill leachate samples were taken from two outlet points. The fish sampling location was carried out in the Sukamaju River. The physical factors of water measured are temperature, pH, salinity, turbidity, DO, COD and BOD. Fe, Cu, Zn and Pb concentrations were measured using the Atomic Absorption Spectrophotometry (AAS) method. The results show that the physicochemical parameters in leachate and river water exceed the threshold. The contents of Zn, Cu, Fe and Pb in the leachate at both outlet points exceeded the threshold value with values of 2.48 mg/L and 2.80 mg/L; 16.55 mg/L and 17 mg/L; 0.078 mg/L and 0.113 mg/L; 3.26 mg/L and 3.01 mg/L. The concentration of heavy metals Pb and Fe in river water is 0.083-0.162 mg/L and 2.68-2.97 mg/L which are above the quality standard value, while the heavy metal Fe content in fish meat exceeds the specified threshold value, namely 0.557 mg/100 g and 0.564 mg/100 g.

Constructed Wetlands for Municipal Solid Waste Landfill Leachate Treatment with Different Macrophytes in Hot Cimate Regions: A Review

Constructed wetland is a natural, economical and environment friendly option for leachate treatment. The aquatic plants and microorganisms are the main players for the treatment of leachate and are conspicuous favoring feature for any wetland due to their contaminant treatment efficiency. There are several other features which limit or enhance the performance of wetlands. Temperature is one of the factors which influence the performance of any wetland and can improve overall efficiency of the constructed wetland. Deep study of oxygen function reveals that accumulation of oxygen to the liquid or soil of the wetland either by photosynthesis or direct from atmosphere. Organic mailer and nitrification process made possible by transfer of oxygen to rhizosphere through macrophytes and macrophytes grow well in growing season in the presence of sunlight and temperature. The argument is well supported through facts revealed by scientific observations. The natural process of photosynthesis only occurs in the presence of sunlight. Hence main performance of macrophytes depends upon their biomass production and fixation of oxygen to the rhizosphere in growing season, which ultimately enhances the efficiency of wetlands for contaminant removal. This review is to establish the fact that Typha latifolia, Phragmites australis and Scripus Validus are main hydrophytes depict best results in biogeochemical process for contaminant removal from wetlands in hot season except for the Total Suspended Solid (TSS) which does not show considerable difference due to the climate. This fact reveals that the macrophytes are more productive in the warm climate in comparison to cold one. The Typha latifolia, Phragmites australis and Scripus validus are the most common species of macrophytes which are very much affective in contamination removal process especially in temperate or tropical region where climate is above 30oC. The available data of different research papers establishes the fact that wetlands are the low-cost, eco-friendly and efficient solution for majority of contaminants removal. It has also been established that the Tropical and temperate regions enhance efficiency of all parameters up to 10% due to higher temperature.

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.

Characterization and spatiotemporal variations of fluorescent dissolved organic matter in leachate from old landfill-derived incineration residues and incombustible waste.

Dissolved organic matter (DOM) influences the bioavailability and behavior of trace metals and other pollutants in landfill leachate. This research characterized fluorescent dissolved organic matter (FDOM) in leachate from an old landfill in Japan during a 13-month investigation. We employed excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC) to deconvolute the FDOM complex mixture into three fluorophores: microbial humic-like (C1), terrestrial humic-like (C2), and tryptophan-like fluorophores (C3). These FDOM components were compared with findings from other studies of leachate in landfills with different waste compositions. The correlations among EEM-PARAFAC components, dissolved organic carbon (DOC) concentration, and ultraviolet-visible and fluorescence indices were evaluated. The FDOM in leachate varied spatially among old and extended leachate collected in the landfill and leachate treatment facility. The FDOM changed temporally and decreased markedly in August 2019, November 2019, and April 2020. The strong positive correlation between HIX and %C2 (r = 0.87, ρ = 0.91, p < 0.001)) implies that HIX may indicate the relative contribution of terrestrial humic-like components in landfill leachate. The Fmax of C1, C2, and C3 and the DOC concentration showed strong correlations among each other (r > 0.72, ρ > 0.78, p < 0.001) and positive correlations with leachate level (r > 0.41, p < 0.001), suggesting the importance of hydrological effects and leachate pump operation on FDOM.

Investigation of the impact of municipal solid waste disposal site leachate on surface water resources in Hosanna Town, Ethiopia.

Surface water resources are the most precious, yet they are also the most vulnerable to pollution. Consequently, maintaining the sustainability of water supplies is critical for livestock support to achieve SDG goals. Landfill leachate poses a significant threat to water resources in developing countries. This study aims to determine how the Hosanna town landfill site affects the Jewie River by analysing the quality of the Alela and Ajew streams and the landfill leachate in both wet and dry seasons. Furthermore, assess the suitability of the water quality for agricultural purposes. The leachate pollution index (LPI), Canadian Council Member of the Environment Water Quality Index (CCMEWQI), and irrigation water quality indices (IWQI) were computed for both seasons using two composite leachate samples and five flow-pace composite river samples. In the wet season, the leachate pollution indices for L1 and L2 ranged from 20.87 to 22.47, respectively. During the dry season, the leachate pollutant index of L1 and L2 was found to be 24.42 and 27.98. Only the Ajew River stream was affected during the dry season because the landfill site is only 46m away. Both the Ajew and Alela River streams are infested during the rainy season. Irrigation index concentrations revealed that the river water is suitable for cultivation. The early stages of landfill waste maturation are evident from the LPI results. Relocating the dump site is necessary to safeguard water resources because leachate has entered the river streams.

Kinetic, Isotherm, and Thermodynamic Studies of the Removal of Dissolved Chemical Oxygen Demand (dCOD) from Landfill Leachate by Iron Oxide Nanoparticles (IONPs)

Kinetic, Isotherm, and Thermodynamic Studies of the Removal of Dissolved Chemical Oxygen Demand (dCOD) from Landfill Leachate by Iron Oxide Nanoparticles (IONPs)

Design and application of artificial multicellular systems for nitrogen removal from wastewater

Excessive accumulation of nitrogen is a major cause of water eutrophication. Developing an inexpensive and efficient nitrogen removal technology is therefore essential for wastewater purification. The microbial technology for nitrogen removal has been widely used for its low cost, high efficiency, and strong environmental adaptability. Most recently, with the advances in synthetic biotechnology, artificial multicellular systems have been sufficiently developed and exhibited unique definability and controllability. Compared with those in the natural microbial consortia, the nitrogen removal pathways and environmental response mechanisms are easy to be clarified in the artificial multicellular systems, which allow for efficient nitrogen removal under low cellular metabolic loading. Therefore, artificial multicellular systems demonstrate great application potential in the purification of wastewater, including landfill leachate, industrial wastewater, seawater aquaculture wastewater, and domestic sewage. We focused on the design, building, and application of artificial multicellular systems for nitrogen removal from wastewater. Specifically, we summarized the functional microorganisms and their nitrogen removal mechanisms, introduced the design principles and building methods of artificial multicellular systems, illustrated the application of artificial multicellular systems with examples, and prospected the future research trend in nitrogen removal from wastewater. The conclusion is expected to provide new insights and efficient strategies for optimizing the microbial nitrogen removal from wastewater.

Full-Scale Demonstration of Nitrogen Removal from Mature Landfill Leachate Using a Two-Stage Partial Nitritation and Anammox Process

The excessive discharge of nitrogen leads to water eutrophication. The partial nitritation and anammox (PN/A) process is a promising technology for biological nitrogen removal in wastewater treatment. However, applying it to mature landfill leachate (MLL) faces challenges, as the toxic substances (e.g., heavy metal) within MLL inhibit the activity of anammox bacteria. Therefore, most previous studies focused on diluted, pretreated, or chemically adjusted MLL. This study demonstrated at full scale that the two-stage PN/A process can treat raw MLL. Initially, the operational issue of sludge floatation resulted in rapid biomass loss with overflow discharging, which selectively suppresses nitrite-oxidizing bacteria (NOB), promoting the achievement of nitrite accumulation. After that, the NOB suppression was self-sustained by the high in situ free ammonia concentration, i.e., 26.2 ± 15.9 mg N/L. In the subsequent anammox tank, nitrogen removal primarily occurred via the anammox process, complemented by denitrification, achieving total nitrogen removal efficiency exceeding 72%. In addition, the nitrogen removal capacity of this system was significantly influenced by temperature with the nitrogen-loading rate above 0.4 kg N/m3/d at 38 °C and approximately 0.1 kg N/m3/d at 21 °C. The optimization of system operation, such as gradually increasing MLL content, remains necessary to enhance nitrogen removal capacity further.

Research Progress of Chromophoric Dissolved Organic Matter (CDOM) in Landfill Leachate by Electrochemical Method

Over the years, industry, agriculture and other human activities have discharged large amounts of organic pollutants into landfills. Among them, color-resistant dissolved organic pollutants have attracted great attention. In order to achieve the safe discharge of wastewater, a variety of treatment technologies have been used to effectively eliminate CDOM in water. In this paper, the most promising electrochemical oxidation (EO) techniques are reviewed, their basic principles are introduced, and the research progress and application status of electrode materials and electrochemical reactors are introduced. At the same time, the substance composition and detection method of CDOM are discussed. Finally, the performance of EO technology to remove CDOM is summarized. However, we should note that electrode optimization has always been the core of EO technology improvement, and the combination of updated electrode material iteration and treatment process has broad prospects for the wide application of EO technology.