Search Results (47)

The study evaluated the feasibility of using the activated sludge process to treat real wastewater from used oil installations containing petroleum hydrocarbons, boron (B), and adsorbable organic halides (AOX). The aim was to determine the maximum ratio of this wastewater that could be added to the influent without impairing treatment efficiency. Tested shares ranged from 0.50% to 1.90%. An initial 1.30% of the tested share caused process instability, reflected in the elevated total nitrogen (TN) levels in treated wastewater. After reducing the share to 0.50%, an adaptation of the activated sludge was observed, manifested by a decrease in TN concentration to below 15.0 mg N/L. For the most favorable share of 1.60% (0.38 ± 0.10 kg_BOD5/kg_MLSS d, 0.51 ± 0.14 kg_COD/kg_MLSS d), the removal efficiencies of chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), TN, and total phosphorus (TP) were 95.0% ± 1.5, 99.1% ± 0.2, 89.3% ± 2.7, and 94.0% ± 5.0, respectively. Increasing the share to 1.90% decreased treatment efficiency and exceedances of COD, BOD₅, TN, and TP occurred. At this ratio, an increase in ammonium nitrogen (NH4⁺-N) and TN concentrations was observed, indicating the inhibition of nitrification. However, the average concentrations of mineral oil index, AOX and B in the treated wastewater remained within permissible levels throughout the study. Full article

Municipal wastewater (MWW) was treated using a microalgal–bacterial consortium without mechanical aeration. An inoculum for the reactor was prepared by acclimatizing Chlorella vulgaris to MWW and supplementing with a small amount of activated sludge. The hydraulic retention time (HRT) and solids retention time (SRT) were progressively reduced from 6.67 to 1.17 d and from 10 to 6.67 d, respectively, to test the process robustness under realistic MWW operation. The COD removal efficiency was 88% at 0.23 kg-COD/m³/d. Mass balance suggested the major nitrogen and phosphorus removal mechanism as assimilation. A high percentage (80%) of oxidized nitrogen indicated an efficient nitrification at all HRTs. Inorganic carbon (IC) balance calculation explained the observed IC dynamics. The chlorophyll a-to-mixed liquor volatile suspended solids (MLVSS) ratio and percentage of nitrite responded to IC limitation and supplementation. The mixed liquor exhibited excellent settleability (sludge volume index: 42 mL/g) with dense algal–bacterial flocs. An increased organic loading rate, however, reduced daytime dissolved oxygen, suggesting limitation under non-aerated conditions. These findings demonstrate the potential of microalgal–bacterial systems to achieve efficient COD removal and nitrification at realistic HRTs without aeration while emphasizing the importance of IC management. Full article

Chemical contaminants in drinking water represent a widespread threat to human health, making water quality monitoring an essential mitigation measure. This study aimed to assess the quality of drinking water by conducting comprehensive multi-year seasonal monitoring at seven distribution points in central Romania, determining the spatial and temporal trends of relevant physical parameters (pH and electrical conductivity) and chemical contaminants (NO₂, NO₃, NH₄, Cl, and SO₄). The pollution degree was evaluated using the pollution index and the overall pollution assessment index. The principal component analysis attributed over 60% of water quality variance to NO₂, NO₃, and NH₄ pollution, linked to incomplete nitrification or external loading, such as agricultural practices. Additionally, a human health risk assessment was performed according to U.S. EPA guidelines, calculating the chronic daily intake, hazard quotient, and hazard index for nitrogen compounds via oral and dermal exposure pathways for both adults and children. The results showed significant seasonal fluctuations in nitrogen compounds and electrical conductivity. The pollution indices classified the water bodies across a spectrum from “light” to “significant” pollution degrees. The health risk assessment revealed that NO₃ was the primary risk driver, with hazard index values exceeding the threshold of one in specific locations and seasons, indicating potential adverse health effects, particularly for children. Full article

The coal mining subsidence area constitutes a distinct ecotone in the transition from agricultural soil to sediment, yet the microbially mediated nitrogen cycle within it remains inadequately understood. This investigation comprehensively analyzed physicochemical properties, microbial communities, functional genes, and co-occurrence networks along a 0–6500 mm depth gradient. Results indicated that pH transitioned from acidic to alkaline, while TN, TP, OM, and NH₄⁺–N accumulated with depth. NO₃⁻–N decreased rapidly within 1000 mm and then stabilized. Alpha-diversity showed an S-shaped increase in richness, with Shannon index peaking at 1500 mm. Beta-diversity shifted along PC1, and the shallow subsidence area (SS) influenced by NO₃⁻–N; the transition zone (TZ) regulated by OM, TN, and NH₄⁺–N; deep subsidence area (DS) was constrained by TP and pH. Microbial communities transitioned from aerobic/facultative to strictly anaerobic phyla, yet Pseudomonadota remained dominant (24–32%) across depths. With increasing depth, gene abundances for denitrification, assimilatory nitrate reduction to ammonium (ANRA), and nitrate assimilation declined, while those for dissimilatory nitrate reduction to ammonium (DNRA) and nitrification increased; nitrogen fixation remained weak. Co-occurrence networks shifted from highly connected, short-pathlength, and clustered in TZ to highly modular and long-pathlength in DS, with Aminicenantes, Syntrophus, and Methanoregula as key taxa. Overall, the thick and stable reducing zone in the subsidence area restructured the nitrogen cycle, shifting terminal products from N₂ removal to NH₄⁺ retention. These findings advance the understanding of nitrogen transformation in soil-sediment ecotones and provide a mechanistic framework for nitrogen cycling in mining-affected ecosystems. Full article

Substituting chemical fertilizers with organic alternatives represents an effective strategy for mitigating soil nitrogen (N) loss and reducing chemical fertilizer use. However, the efficacy of organic substitution in regulating soil N fertility and rice growth requires further investigation, and mechanistic studies elucidating how organic fertilizers affect soil N transformation processes and availability are still deficient. To address this, we conducted a three-year field experiment from 2021 to 2023, comparing three rice fertilization regimes: (1) chemical fertilizer as the control (CK), (2) substitution with organic fertilizer (OF), and (3) substitution with biochar-based organic fertilizer (BF). Both organic substitution treatments were applied as basal fertilizer, and the rice plants received equivalent topdressing applications. The soil N availability, gross and net N transformation rates, and soil microbial activity were analyzed, and the rice growth index and yield were determined. The results showed that organic substitution (OF and BF) significantly increased the soil total carbon content, stimulated microbial biomass growth and enhanced enzymatic activity associated with soil C and N cycling. However, the limited N input from organic substitution significantly decreased the soil gross N mineralization rate by 28.30% (OF) and 58.14% (BF), compared to chemical fertilization (CK). It also reduced the gross N nitrification rate by 38.30% (OF) and 36.17% (BF). These suppressed N transformation processes ultimately led to 11.97% (OF) and 14.72% (BF) lower soil mineral N contents. The soil N deficiency during critical early vegetative growth stages substantially constrained rice development, resulting in significant yield reductions in the OF and BF treatments compared to chemical fertilization (CK). These results indicate that complete organic substitution compromises rice yields due to insufficient N availability; therefore, we recommend integrated organic–mineral fertilization as an optimal strategy to achieve both crop productivity and environmental benefits. Full article

The rapid development of marine recirculating aquaculture systems (RASs) worldwide offers an efficient and sustainable approach to aquaculture. However, the slow start-up of the nitrification process under low-temperature conditions remains a significant challenge. This study evaluated multiple start-up strategies for moving bed biofilm reactors (MBBRs) operating at 13–15 °C. Among them, the salinity-gradient (SG) strategy exhibited the best performance, reducing the start-up time by 38 days compared to the control, with microbial richness (Chao1 index) reaching 396 and diversity (Shannon index) of 4.89. Inoculation with mature biofilm (MBI) also showed excellent results, shortening the start-up period by 26 days and achieving a stable total ammonia nitrogen (TAN) effluent concentration below 0.5 mg/L within 132 days. MBI exhibited the highest microbial richness (Chao1 index = 808) and diversity (Shannon index = 5.55), significantly higher than those of the control (Chao1 index = 279, Shannon index = 3.90) and other treatments. The hydraulic retention time-gradient (HRT) strategy contributed to performance improvement as well, with a 24-day reduction in start-up time and a Chao1 index of 663 and a Shannon index is 4.69. In contrast, nitrifying bacteria addition (NBA) and carrier adhesion layer modification (CALM) had limited effects on start-up efficiency or microbial diversity, with Chao1 indices of only 255 and 228, and Shannon indices were both 3.24, respectively. Overall, the results indicate that salinity acclimation, mature biofilm inoculation, and extended HRT are effective approaches for promoting microbial community adaptation and enhancing MBBR start-up under low-temperature marine conditions. Full article

Soil erosion-prone areas require effective microbial treatments to improve soil bacterial communities and functional traits. Understanding the driving effects of different microbial interventions on soil ecology is essential for restoration efforts. Single and combined microbial treatments were applied to soil. Bacterial community structure was analyzed via 16S IRNA high-throughput sequencing, and functional groups were predicted using FAPROTAX. Soil microbial carbon, nitrogen, metabolic entropy, and enzymatic activity were assessed. Microbial Carbon and Metabolic Activity: The Arbuscular mycorrhizal fungi (AMF) and Bacillus mucilaginosus (BM) (AMF.BM) treatment exhibited the highest microbial carbon content and the lowest metabolic entropy. The microbial carbon-to-nitrogen ratio ranged from 1.27 to 3.69 across all treatments. Bacterial Community Composition: The dominant bacterial phyla included Firmicutes, Proteobacteria, Acidobacteria, Bacteroidetes, and Actinobacteria. Diversity and Richness: The AMF and Trichoderma harzianum (TH) (AMF.TH) treatment significantly reduced diversity, richness, and phylogenetic diversity indices, while the AMF.BM treatment showed a significantly higher richness index (p < 0.05). Relative Abundance of Firmicutes: Compared to the control, the AMF, TH.BM, and TH treatments decreased the relative abundance of Firmicutes, whereas the AMF.TH treatment increased their relative abundance. Environmental Correlations: Redundancy and correlation analyses revealed significant correlations between soil organic matter, magnesium content, and sucrase activity and several major bacterial genera. Functional Prediction: The AMF.BM treatment enhanced the relative abundance and evenness of bacterial ecological functions, primarily driving nitrification, aerobic ammonia oxidation, and ureolysis. Microbial treatments differentially influence soil bacterial communities and functions. The AMF.BM combination shows the greatest potential for ecological restoration in erosion-prone soils. Full article

The benefits of partially substituting inorganic fertilizers with organic fertilizers have been extensively acknowledged. However, the key mechanisms behind nutrient transformation and supply for stable crop yields are still not fully understood. Based on an 11-year field experiment with a wheat–maize rotation system, this study explored the advantages of combined straw and manure substitution under various organic substitution regimes. These regimes included an unfertilized control (CK), inorganic nitrogen, phosphorus, and potassium fertilizers (NPK), NPK substituted with straw (NPKS), NPK substituted with manure (NPKM), and NPK substituted with both straw and manure (NPKSM). Compared to NPK and NPKS, NPKM and NPKSM significantly improved wheat yield by 12.8% and 13.8%, respectively. Bulk soil organic carbon (SOC), total nitrogen (TN), available superphosphate (AP), β-glucosidase (βG), urease (URE), and alkaline phosphatase (ALP) were all higher in the NPKM treatment than in the NPKSM treatment. However, compared to NPKM, NPKSM significantly decreased the potential nitrification rate by 31.0% and increased the soil NH₄⁺-N content. Correspondingly, the functional genes of nitrification were also found to be decreased in the NPKSM treatment. In the rhizosphere, most soil factors increased compared to bulk soil, but treatment differences were smaller. However, the differences among treatments were reduced in the rhizosphere. The high amount of manure applied in the NPKM treatment caused excessive soil phosphorus accumulation, reaching over 46.7 mg/kg, resulting in lower N/P and C/P ratios. The soil quality index (SQI), based on soil nutrients, enzymes, functional genes, and C:N:P stoichiometry, was 9.9% higher in NPKSM than in NPKM. Bulk soil SQIs showed stronger correlations with wheat yields than rhizosphere SQIs, highlighting that bulk soil was superior to rhizosphere in predicting crop yield. Partial least squares path modeling showed that C/N, N/P, and C/P ratios strongly influenced SQIs. The NPKSM treatment, which improved soil nutrients, biological factors, and balanced C:N:P stoichiometry, is an effective strategy for sustainable agriculture. Future practices should focus on maintaining stoichiometric balance to sustain soil quality and crop yields. Full article

Urban landscape lakes are increasingly at risk of nitrogen-induced eutrophication. Microbial nitrogen transformation plays a crucial role in reducing nitrogen levels in these lakes. However, the relationships between microbial communities, nitrogen functional genes, and nitrogen dynamics in water and sediment, along with their underlying mechanisms, remain unclear. In this study, we systemically investigated the spatial distributions of physicochemical indicators in the overlying water and sediment in a typical urban landscape lake, Zizhuyuan Park, and the microbial communities and nitrogen cycling genes in the surface sediments of the lake connection (CO), side (SI), and center (CE) were evaluated via macrogenetic sequencing technology to analyze their relationships with environmental factors. The results revealed that the concentrations of TN, NO₃⁻, and NH₄⁺ in the lake water were within the ranges of 1.36~2.84, 0.98~1.92, and 0.01~0.29 mg·L⁻¹, respectively. The concentrations of TN, NO₃⁻, and NH₄⁺ in the sediments ranged from 1.17~3.47 g·kg⁻¹, 0.88~1.94 mg·kg⁻¹, and 5.61~10.09 mg·kg⁻¹, respectively. The contents of NH₄⁺ in water, TN and NO₃⁻ in sediments were significantly different in spatial distribution (p < 0.05). At the CE site, the Shannon diversity index was the highest and differed significantly from the values at the SI and CO sites (p < 0.01).The sediments of Central Lake contained a total of 36 phyla and 1303 genera of microorganisms. Proteobacteria (62.88–64.83%) and Actinobacteria (24.84–26.62%) accounted for more than 85% of the microorganisms. Nitrospirae, Ignavibacteriae, and Bacteroidetes were significantly different (p < 0.05) at the CE, and Planctomycetes were significantly different (p < 0.05) at the CO. The functional gene nrfA exhibited the highest abundance, followed by napA, nosZ, nirS, hao, ureC, norB, nifH, nirK, hdhA, nifB, and amoA. The abundances of hao and nifH differed significantly at various locations in Central Lake (p < 0.05). The key nitrogen transformation processes in the sediments, ranked by contribution rate, were DNRA, denitrification, nitrification, ammoniation, nitrogen fixation, and anammox. The six nitrogen processes showed significant differences (p < 0.01) in spatial distribution. The pH, TN, NO₃⁻, NH₄⁺, C/N ratio of the sediment, and NH₄⁺ in the lake water impact the microbial community and nitrogen conversion process. The sediment should be cleaned regularly, and the water cycle should be strengthened in urban landscape lakes to regulate microorganisms and genes and ultimately reduce nitrogen and control eutrophic water. This study can provide a reference for improving and managing lake water environments in urban landscapes. Full article

The removal of nitrogen compounds in wastewater has been successfully developed with various activated sludge-based processes. Microorganisms immobilized in media would enhance biological efficiency by the increase in biomass concentration; however, the microbial community composition in media has not been revealed. Attached microbial communities on immobilization media were analyzed after the operation of the wastewater treatment process, comparing aerobic and anoxic reactors. A modified Ludzack–Ettinger (MLE) process was operated with immobilized media with polyvinyl alcohol and polyethylene glycol. The mixed liquor suspended solid (MLSS) concentration in an aerobic reactor was maintained at 50,000 mg/L and 40,000 mg/L in an anoxic reactor by the media. A maximum of 99% of ammonium nitrogen from the influent was calculated to be oxidized; however, the organic nitrogen produced from microbial growth reduced the overall oxidation rate. The denitrification rate increased with the addition of glucose to adjust the carbon-to-nitrogen (C/N) ratio. Based on the total nitrogen concentration, the nitrogen removal efficiency was calculated to be 48.2% following the adjustment of the C/N ratio. A phylogenetic analysis of the microbial community in immobilized media using next-generation sequencing (NGS) revealed the dominance of nitrifying and denitrifying microorganisms in the aerobic and anoxic reactors, respectively. Sequences amplified using V3–V4 region primers of the 16S rRNA gene yielded 531,188 base pairs (bp) and 396,844 bp reads from the aerobic and anoxic reactors, respectively. Operational taxonomic units (OTUs) were identified at both the phylum and genus levels, with a total of 594 from the aerobic reactor and 375 from the anoxic reactor. Proteobacteria was the dominant phylum in both the aerobic and anoxic reactors, comprising 39.7% of the aerobic reactor and 65.9% of the anoxic reactor. The dominant genera in the aerobic reactor were Nitrospira and Povalibacter. Forty-five percent of the total number of OTUs consisted of known nitrification-related genera in the aerobic reactor. In contrast, the dominant genera in the anoxic reactor were Desulfomicrobium, Desulfobulbus, and Methyloversatilis. A total of 63% of the genera associated with denitrification, including Dechloromonas and Flavobacterium, were found in the anoxic reactor. The population of microorganisms in each reactor was compared in terms of diversity by the QIIME 2 algorithm. The Chao1 index values of α-diversity were 606.05 for the aerobic reactor and 415.53 for the anoxic reactor, indicating greater population diversity in the aerobic reactor compared to the anoxic one. The widespread distribution of nitrification activities among various groups has led to diverse population characteristics in the aerobic environment, particularly within the attached community. The microbiological community present in immobilized aerobic and anoxic media will contribute to future microbial studies on wastewater treatment processes. Full article

Certain plant species have developed the ability to express biological nitrification inhibition (BNI), suppressing the activity of nitrifying microbes and thereby reducing the conversion of ammonium to nitrate. This study assessed the BNI capacity and the rhizosphere ammonia-oxidizing microbiome of two grass species: the endemic Australian Barley Mitchell grass (Astrebla pectinata) and the introduced koronivia grass (Urochloa humidicola), using soils from both agricultural land and native vegetation. In agricultural soil, koronivia grass exhibited significantly higher BNI capacity compared with Barley Mitchell grass. However, in native soil, this trend was reversed, with Barley Mitchell grass demonstrating a significantly greater BNI capacity than koronivia grass (52% vs. 38%). Koronivia grass significantly altered the composition of the ammonia-oxidizing bacteria community in its rhizosphere, leading to a decrease in the Shannon index and bacteria number. Conversely, Barley Mitchell grass reduced the Shannon index (1.2 vs. 1.7) and population size (3.28 × 10⁷ vs. 7.43 × 10⁷ gene copy number g⁻¹ dry soil) of the ammonia-oxidizing archaea community in its rhizosphere to a greater extent. These findings suggest that Australian Barley Mitchell grass may have evolved mechanisms to suppress soil archaeal nitrifiers, thereby enhancing its BNI capacity and adapting to Australia’s nutrient-poor soils. Full article

The impact of climate change on methane (CH₄) emissions from rice production systems in the Coimbatore region (Tamil Nadu, India) was studied by leveraging field experiments across two main treatments and four sub-treatments in a split-plot design. Utilizing the closed-chamber method for gas collection and gas chromatography analysis, this study identified significant differences in CH₄ emissions between conventional cultivation methods and the system of rice intensification (henceforth SRI). Over two growing seasons, conventional cultivation methods reported higher CH₄ emissions (range: from 36.9 to 59.3 kg CH₄ ha⁻¹ season⁻¹) compared with SRI (range: from 2.2 to 12.8 kg CH₄ ha⁻¹ season⁻¹). Experimental data were subsequently used to guide parametrization and validation of the DeNitrification–DeComposition (DNDC) model. The validation of the model showed good agreement between the measured and modeled data, as denoted by the statistical tests performed, which included CRM (0.09), D-index (0.99), RMSE (7.16), EF (0.96), and R² (0.92). The validated model was then used to develop future CH₄ emissions projections under various shared socio-economic pathways (henceforth SSPs) for the mid- (2021–2050) and late (2051–2080) century. The analysis revealed a potential increase in CH₄ emissions for the simulated scenarios, which was dependent on specific soil and irrigation management practices. Conventional cultivation produced the highest CH₄ emissions, but it was shown that they could be reduced if the current practice was replaced by minimal flooding or through irrigation with alternating wetting and drying cycles. Emissions were predicted to rise until SSP 370, with a marginal increase in SSP 585 thereafter. The findings of this work underscored an urgency to develop climate-smart location-specific mitigation strategies focused on simultaneously improving current water and nutrient management practices. The use of methanotrophs to reduce CH₄ production from rice systems should be considered in future work. This research also highlighted the critical interaction that exists between agricultural practices and climate change, and emphasized the need to implement adaptive crop management strategies that can sustain productivity and mitigate the environmental impacts of rice-based systems in southern India. Full article

In order to increase nutrient input and alleviate the poor growth of blueberry (Vaccinium corymbosum L.) in neutral soil with strong nitrification, the application of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) as an enhanced efficiency fertilizer is a strategy to reduce nitrogen (N) loss and improve N supply. However, few studies have systematically investigated the effect of DMPP application on blueberry and its soil condition in detail so far. In this study, a pot experiment was conducted to elucidate the effect of DMPP at four gradient levels including 0.5% (w/w applied-N) DMPP (DL), 1% DMPP (DM), 2% DMPP (DH), and no DMPP (CK) on the dynamics of soil mineral N (NH₄⁺-N and NO₃⁻-N), soil chemical properties, as well as the agronomic characteristics and physiological indexes of blueberry plants in the neutral soil–blueberry system. The addition of DMPP significantly increased the retention of soil ammonium nitrogen and the content of total mineral nitrogen. qPCR analysis showed that DMPP inhibited the ammoxidation process mainly by reducing the abundance of the ammonia-oxidizing bacteria (AOB) amoA gene rather than the ammonia-oxidizing archaea (AOA) amoA gene. No significant inhibitory effect of DMPP was observed for the nitrite dehydrogenase gene nxrA and nitrite reductase gene nirS. Soil NH₄⁺-N and available phosphorus content were both enhanced with the DMPP application rates both in bulk and rhizosphere soil. Applying 1% DMPP to the neutral soil for blueberry was sufficient to safely inhibit soil nitrification, not only increasing ammonium nitrogen content by 10.42% and 26.79%, but also enhancing available phosphorus content by 9.19% and 22.41% compared with CK in bulk and rhizosphere soil, respectively. Moreover, 1% DMPP addition increased the nitrogen and phosphorus concentration of blueberry leaves by 12.17% and 26.42%, respectively, compared with CK. The total branch length and the dry weight of blueberry plant were also increased by 16.8% and 33.1%, respectively. These results provide valuable agronomic information for the application of DMPP in blueberry cultivation. Fertilization applied with 1% DMPP has great economic potential to improve both nitrogen and phosphorus absorption of blueberry so as to promote the vegetative growth of blueberry. Full article

Nitrification is the core step of the soil nitrogen cycle and directly affects the nitrogen use efficiency in agricultural systems. Biochar and gypsum are two important soil amendments widely used in coastal saline farmland. However, little is known about their effects on nitrification and ammonia-oxidizing microorganisms. A one-year pot experiment with three treatments including biochar application (BC), gypsum application (SG), and no amendment (CK) was conducted, and the responses of the nitrification rate, amoA gene copies, and the diversity and community structure of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to biochar and gypsum were evaluated. The results indicated that biochar and gypsum application both resulted in alterations to the soil properties. They both had inhibiting effects on nitrification and AOB amoA gene copies, whereas they had no significant effect on AOA amoA gene copies. Biochar had no significant effect on the diversity indexes of AOA, but it significantly reduced the Shannon index of AOB. Meanwhile, gypsum had no significant influence on the diversity indexes of both AOA and AOB. Biochar and gypsum did not significantly affect the community structure of AOA but did induce changes in that of AOB. In detail, biochar significantly enhanced the relative abundance of the dominant cluster Nitrosospira, whereas gypsum led to a notable increase in the relative abundance of unclassified_o_Nitrosomonadales. The Shannon index of AOB had a significant negative correlation with soil TOC, TN, and NH₄⁺ content, and soil pH was the first primary environmental factor that affected the AOB community structure. In conclusion, biochar and gypsum inhibited nitrification by suppressing the activities of AOB and changed the diversities and community structure of AOB by altering related soil properties. Full article

Electrochemical methods for the treatment of municipal and industrial wastewater are used either independently or in conjunction with biological methods for pretreatment or posttreatment of biologically treated wastewater. In our work, the combination of these processes was studied, where pre-electrolysis was used to produce dissolved iron before the activation process. Electrolysis was also directly introduced into the activation using either iron or carbon electrodes. The surface of one iron electrode was 32.2 cm², voltage at the electrodes was 21 V, and current was 270 mA. The surface of one carbon electrode was 7.54 cm², current was 82.5 mA, and voltage at the electrodes was 21 V. Laboratory research on synthetic municipal wastewater treatment using a combination of electrolysis and activation processes showed that the use of iron electrodes increases the efficiency of phosphorus removal compared to its precipitation with iron salts. Electrolysis has shown a positive effect on the sedimentation properties of sludge and the destruction of filamentous microorganisms. Even though it negatively affected the respiration rates of activated sludge and the denitrification efficiency, it did not have a negative impact on the nitrification activity of sludge. Full article