Biological Wastewater Treatment Research Articles

Tailoring microbial redox with alternating current for efficient mineralization of refractory organic nitrogen compounds in wastewater

Traditional biological wastewater treatment struggles to efficiently remove refractory organic nitrogen compounds (RONCs). This study demonstrates the potential of alternating current (AC)-driven bioelectrodes for deep mineralization of nitrobenzene (NB) by coupling in situ reduction and oxidation reactions. Sine-wave AC bioelectrodes overcome the limitations of direct current (DC) systems, achieving 97.6% NB reduction, 90.9% intermediate mineralization, and 80.8% total nitrogen removal while reducing energy consumption by 22.3%. AC stimulation enhances biofilm formation and bidirectional electrocatalytic activity, leading to higher biomass and electron utilization efficiency. Multi-omics analysis shows enrichment of functional microbial consortia involved in NB reduction, aromatic compound oxidation, ammonia oxidation, nitrate/nitrite reduction, and electron transfer, with upregulated enzyme gene expression. Carbon metabolites from catechol meta-cleavage support nitro-reduction, denitrification, and cell viability without external carbon sources. Nitrification-denitrification is the primary pathway for inorganic nitrogen removal. This AC bioelectrode offers an efficient, low-carbon solution for RONC mineralization in wastewater.

Coupling Driving Force–Pressure–State–Impact–Response–Management Framework with Hydrochemical Data for Groundwater Management on Sithonia Peninsula, Greece

Water scarcity in coastal tourist areas constitutes a critical environmental and socioeconomic sustainability issue. Hence, it is crucial to implement an integrated water resource management and protection plan. In this research, the DPSIR framework is coupled with hydrochemical data on groundwater resources in the fractured aquifer of the Sithonia Peninsula in Chalkidiki, North Greece. Geographical and demographic data, together with morphology, geology, hydrology, and groundwater quality data, were collected and evaluated to categorize the hydrosystem’s driving forces, pressures, states, impacts, and responses. The main pressures that affect groundwater quality in the study area are tourism, geological formation, and land use. Based on the analysis of the DPSIR framework, the absence of a landfill site, the inadequate operation of sewage treatment plants and biological wastewater treatment systems, and tourist activity contribute significantly to the degradation of groundwater quality. Additionally, the fractured rock aquifer develops preferential flow paths to pollutants through preexisting faults, which influence groundwater quality. The hydrochemical analysis of groundwater indicates seawater intrusion in the coastal area. The combination of DPSIR analysis and a water quality index based on ion ratios of groundwater samples identifies high-risk areas of seawater intrusion. Thus, it is essential to reinforce groundwater resources by implementing managed aquifer recharge, limiting unnecessary use of groundwater during the tourist season, and storing surface water during the wet period.

Microelectricity enhances aerobic granular sludge granulation and sulfamethazine degradation: Performance, mechanism, antibiotic resistance genes and microbial community.

With the widespread use of typical antibiotics such as sulfamethazine (SMT), it leads to their accumulation in the environment, increasing the risk of the spread of antibiotic resistance genes (ARGs). Aerobic granular sludge (AGS) has shown great potential in treating antibiotic wastewater. However, the long cultivation period of AGS, the easy disintegration of particles and the poor stability of degradation efficiency for highly concentrated antibiotic wastewater are still urgent problems that need to be solved, and it is important to explore the migration and changes of ARGs and microbial diversity in AGS systems. In this study, a microelectrically enhanced pelletizing reactor (MEPR) was innovatively constructed using a microbial electrolysis cell (MEC) coupled with an AGS system, and a comparative study was carried out using a conventional sequential batch reactor (SBR). The results showed that the AGS obtained from MEPR culture was smooth white spherical, with rich internal microbial phase and good sludge activity. The microelectric condition shortened the AGS culture cycle by 10 days, with smaller AGS particle size, denser structure, and better pollutant degradation ability, and the average removal rate of SMT by MEPR (74.3 %) was much higher than that of SBR (3.13 %). The microelectrical properties reduced the sludge pressure to a certain extent, induced the reasonable secretion of extracellular polymeric substances (EPS), and kept the MEPR in a strong stable state. High-throughput sequencing and detection of ARGs indicated that MEPR had a richer microbial community structure, which significantly controlled the enrichment of ARGs. This study provides a theoretical reference for enhanced sludge granulation and biological treatment of high concentration antibiotic wastewater.

Microbial Coadaptation Drives the Dynamic Stability of Microecology in Mainstream and Sidestream Anammox Systems Under Exposure of Progesterone

Microbial cooperation determines the efficacy of wastewater biological treatment, and the adaptability of microorganisms to environmental stresses varies. Recently, extensive use of hormones results in their inevitable discharge into aquatic environment. Therefore, mainstream and sidestream anammox reactors were constructed in this study to evaluate their removal performance of progesterone and nitrogen simultaneously, the adaptability of anammox consortia to progesterone stress and the corresponding regulation mechanism. Both anammox processes had the resilience to progesterone stress, with the average nitrogen removal efficiency exceeding 90%. At the same time, progesterone removal efficiency also exceeded 70%. In contrast, microbial community in the mainstream reactors was more susceptible to progesterone interference. The adaptation of anammox consortia mainly depended on microbial cooperation and molecular regulation. Initially, bacteria secreted more extracellular polymeric substances to detain progesterone. Biodegradation also contributed to mitigating the side effect of progesterone, which was demonstrated by the proliferation of potential degrading bacteria such as Bacillus salacetis, Bacillus wiedmannii and Rhodococcus erythropolis. In addition, the enhancement of microbial interaction intensity drove their cooperation to enhance adaptability and maintain stable performance. Combined with metagenomic and metatranscriptomic analyses, such microbial adaptability was enhanced through molecular regulations, including the energy redistribution for amino acid synthesis and alteration of key metabolic pathways. Related functional gene expressions and microbial interactions were, in turn, regulated by quorum sensing. This work verifies the feasibility of anammox process in hormone-containing wastewater treatment and provides a holistic understanding of molecular mechanism of microbial interaction and coadaptation to stress.

Application of algae and zeolite in wastewater treatment: Effects on maize properties and soil fertility

ABSTRACT As a consequence of fresh water shortage, non-conventional water resources have become increasingly demandable in semi-arid and arid areas due to the increase in population and urbanization. In Egypt, the reuse of drainage water provides a demanding supplement to irrigation water. This research aims to present natural treatment process for drainage wastewater to be reused in irrigation to support water resources and water quality control. Two biological and chemical wastewater treatment techniques (Algae and Zeolite), under different conditions, were applied to allow the reuse of wastewater to be utilized in the agriculture of very economically important crop which is maize, and comparing the production and the chemical components of the crop with the one irrigated by fresh Nile water. Water, soil and plant analyses were performed. Zeolite was characterized by XRD, SEM and FTIR. Enzymes activities were assigned also (dehydrogenase, phosphatase and nitrogenase activities) and finally the statistical analysis was determined by CoStat software. The treated wastewater chemical and biological analyses showed much better results than El-Rahawy drain wastewater analyses. The plants growth parameters results showed the higher ones with plants subjected to the chemical and biological treatments. Protein and carbohydrate levels, which are the most important plant quality indicators, showed higher concentrations in the treated ones than that irrigated with Nile water. NPK concentration of both seeds and leaves also recorded better levels. The results of the enzymes activities in cases of T4, dehydrogenase, phosphatase, and nitrogenase enzyme activity were 127.66, 40.89, and 79.58, respectively, which increased when compared with control treated with Nile water which were (112.44, 28.4, and 41.39) for dehydrogenase, phosphatase and nitrogenase enzymes respectively.

Mass and heat transfer at spiral tube internal used as a heat exchanger and catalyst support in a continuous bubble column reactor

ABSTRACT Slurry bubble columns find extensive applications in three-phase reactions, including biological wastewater treatment, fermentation, and hydrotreating, among others. Despite their merits, these reactors suffer from drawbacks such as high back mixing and challenges in product-catalyst separation. This study introduces a novel approach to address these issues by employing a horizontally placed spiral tube within the column, serving as both a catalyst support and a heat exchanger. The study investigates the impact of two-phase flow on mass transfer at the outer surface of the spiral tube using the limiting current based electrochemical technique. The experimental setup involves varying spiral tube diameter and pitch, as well as distances between successive spiral tubes. The results showed that the mass transfer coefficient increases with increasing superficial gas and solution velocities but decreases with increasing spiral tube diameter and pitch. An array of three separated horizontal spiral tubes was also tested, and the mass transfer coefficient was found to be slightly lower than that of a single spiral tube by an amount ranged from 4 to 19%. The study provides valuable insights into optimizing reactor design for improved efficiency, offering a potential solution to challenges in slurry bubble column reactors.

Disinfection of Activated Sludge by Combination of the Fenton Reagent and Physical Treatment

Biological wastewater treatment plants could serve as an important alternative to renewable biological nitrogen mines, which are locally available and have a low carbon footprint. Recent progress in Fenton processes has revealed their potential use for sludge treatment to decrease organic contamination and pathogens. The aim of this study was to determine the optimal concentrations of metal catalyst Fe(II) and hydrogen peroxide H2O2 for activated sludge (AS) disinfection using the Fenton process at near-neutral pH, alone and in combination with thermal treatment and UV radiation. The efficiency of the 48 h treatment was evaluated by log reduction, fluorescein diacetate (FDA) hydrolysis activity, concentration of pharmaceuticals, changes in antimicrobial resistance, and ecotoxicity. Using the desirability function approach, a combination of 239 mM H2O2 and 8.6 mM Fe(II) was found to be optimal in frames of the chosen concentrations of reagents. The FDA hydrolysis activity correlated with log reduction at 287 mM H2O2 and different Fe(II) concentrations. Sludge treatment resulted in the removal of ciprofloxacin by 65.5%. The sets with the highest log reduction, i.e., additionally treated by heating and UV, were accompanied by increasing ecotoxic effects on crustaceans, Thamnocephalus platyurus. The Fenton process shows prospective ways on sludge stabilization for its application as a fertilizer.

Application of fertigation using biotreated agro-industrial wastewater (with Bacillus paramycoides MT477810) on the growth of two vegetables Capsicum annuum (var. Astra) and Lycopersicon esculentum (var. Kristina)

ABSTRACT This research explored the use of the fertigation technique with treated agro-industrial wastewater to enhance the growth of Capsicum annuum (var. Astra) and Lycopersicon esculentum (var. Kristina). The wastewater, collected from Bajwa Agro Industries in Lahore, was biotreated using the bacterial strain Bacillus paramycoides MT477810, with a 10% inoculum incubated at 37 °C for 48 h. The bacterial strain achieved an 87% decolorization of the wastewater. Physicochemical analysis before and after biotreatment showed reductions in pH (60%), EC (22%), salinity (16%), turbidity (48%), COD (40%), BOD (73%), TDS (62%), and TSS (25%). The two vegetable varieties were fertigated with both biotreated and untreated wastewater to assess their effects on seed germination and plant growth. Results indicated a significant reduction in phytotoxicity (over 50%) in plants grown with biotreated wastewater. Additionally, plants irrigated with biotreated wastewater showed a 9–30% increase in fresh and dry weights compared to those irrigated with untreated wastewater. Nutritional analysis revealed that crops irrigated with treated wastewater had 12–48% higher nutrient content. These findings emphasize the effectiveness of biological wastewater treatment and fertigation in reducing pollutants and enhancing nutrient availability for vegetable crops.

Influence of technological parameters of biological wastewater treatment using lemnaceae on the degree of antibiotic removal

The article is devoted to the study of the effectiveness of the removal of chloramphenicol, a broad-spectrum antibiotic that is often found in the wastewater of pharmaceutical and medical institutions. The aim of the study was to evaluate the efficiency of chloramphenicol removal from model solutions using Lemna minor (duckweed) depending on the initial concentration of the antibiotic, time of cleaning and specific biomass of duckweed. Model solutions of chloramphenicol with concentrations of 2, 5, 10 and 20 mg/L were used in the study. The cleaning time ranged from 1 to 72 hours, and the chloramphenicol content was determined by liquid chromatography. It was established that the efficiency of cleaning depends not only on the time and initial concentration of the antibiotic, but also on the specific biomass of L. minor. In particular, the greatest efficiency was observed in the interval from 24 to 48 hours, after which the removal of the antibiotic markedly decreased, and the content remained stable until the end of the 72-hour period. At chloramphenicol concentrations of 2 and 5 mg/L with a specific duckweed biomass of 36 g/L, the cleaning efficiency gradually increased and reached maximum values in 72 hours of 23.2% and 26.8%, respectively. For a larger biomass – 50 g/L – these indicators were 17% and 19%, which indicates the possible optimization of the cleaning process when reducing the specific biomass of duckweed. At higher initial concentrations of chloramphenicol (10 and 20 mg/L), the use of duckweed with a specific biomass of 36 g/L provided the maximum antibiotic removal of 33.0% and 29.5%, respectively, in 72 hours of purification. As the biomass increased to 50 g/L, the efficiency decreased and amounted to 23.6% and 21% for these concentrations, which indicates the dependence of the process on the amount of L. minor. The results confirm that the use of Lemna minor is promising for the removal of chloramphenicol from wastewater. The highest efficiency was achieved with a process time of 48 hours and a specific duckweed biomass of 36 g/L, which ensured a decrease in the concentration of chloramphenicol to 29.4% at the initial level of 10 mg/L. The use of duckweed contributes to reducing the environmental burden and reduces the risk of the spread of antibiotic resistance in natural waters.

Effect of Differentially Charged Polystyrene Nanoplastics on the Performance of Biological Denitrification in Wastewater Treatment

Nanoplastics are widely distributed in the environment and can accumulate in organisms. Increasing attention has been paid to the toxic effects of nanoplastics in wastewater biological treatment processes. In this study, polystyrene nanoplastics with different charges were synthesized and used in sequencing batch activated sludge reactors for short-term nanoplastic exposure experiments. Both positively and negatively charged nanoplastics inhibited the nitrogen removal efficiency and gene expressions of nitrification and denitrification-related genes of activated sludge. The inhibiting effect on nitrification of both nanoplastics was enhanced with increasing concentration. The study further evaluated the molecular mechanisms by which differently charged nanoplastics affect denitrification efficiency using the model denitrifying bacterium Pseudomonas stutzeri （P. stutzeri）. The results showed that both positively and negatively charged nanoplastics affected the efficiency of biological denitrification by P. stutzeri, mainly including the promotion of NO3- to NO2- conversion and the significant acceleration of N2O production. Meanwhile, negatively charged nanoplastics inhibited the growth of P. stutzeri and disrupted the cell membrane of the bacterium； however, no change was observed in the expression of denitrification-related functional genes and the nanoplastics might have affected the enzymatic activities of Nir and Nos, which in turn affected the bioprocessing efficiency. This study can provide a certain reference for the evaluation of the biosafety of nanoplastics and provide a certain support for the stable operation of wastewater treatment plants.

APPROXIMATE CALCULATION OF N2O FORMATION IN HETEROTROPHIC DENITRIFICATION PROCESSES OF WASTEWATER DURING BIOLOGICAL TREATMENT

This article addresses the important ecological issue of quantitatively determining greenhouse gas emissions – nitrous oxide – from municipal wastewater treatment facilities, which is a factor in global climate change. Data from scientific research indicate that deep biological treatment of nitrogen compounds at wastewater treatment facilities significantly contributes to the gross emissions of nitrous oxide from industrial facilities. Direct measurements of nitrous oxide emissions from biological treatment facilities in Ukraine have not been conducted. The aim of this study is to assess the potential emissions of the greenhouse gas N2O during the biological treatment of municipal wastewater in aeration tanks operating under the traditional, non-zoned scheme in Ukraine, which ensures deep nitrification. The study was conducted at municipal wastewater treatment facilities equipped with 3-channel aeration tanks. The process of wastewater treatment in aeration tanks operating under the traditional non-zoned scheme is fully aerobic and characterized by deep nitrification. Measurements of hydrochemical indicators of wastewater composition (BOD5, N–NH4, N–NO2, and N–NO3, Kjeldahl nitrogen) were carried out using certified methods in an accredited laboratory. It was found that biological treatment of municipal wastewater exclusively under aerobic conditions does not effectively remove nitrates from the wastewater. The nitrogen balance in incoming and treated wastewater was calculated, and the formation of N2O in the processes of suppressed denitrification was quantitatively determined. The consumption of nitrogen for the formation of excess activated sludge biomass, the efficiency of nitrification to nitrates, and the probable formation of N2O as a result of inhibition of the final heterotrophic denitrification reaction (reduction of N2O to N2) were calculated. The results showed that the maximum value of the N2O emission coefficient (the ratio of formed N2O to the concentration of total nitrogen entering the treatment process) at the studied facility could range from 3.24 % to 6.47 %, which is consistent with direct measurement data conducted at operating treatment facilities by foreign scientists. The study results confirm that modern technologies for deep biological wastewater treatment should consider not only effective removal of biogenic elements but also the minimization of greenhouse gas emissions.

Biological treatment of methyl orange dye and textile wastewater using halo-alkaliphilic bacteria under highly alkaline conditions.

As the textile wastewater is highly saline and has high pH it is important to employ extremophilic microbes to survive in harsh conditions and provide effective bioremediation of textile dyes. This study aims to find a sustainable solution for dye removal by investigating the potential of an indigenously isolated bacterium, Nesterenkonia lacusekhoensis EMLA3 (halo-alkaliphilic) for treatment of an azo dye, methyl orange (MO) and textile effluent. MO dye decolorization studies were conducted using mineral salt media (MSM) by varying incubation time (0-120h), initial dye concentration (50-350mg/L), pH (7.0-12.0), inoculum dose (3-10%), agitation (stationary, 100rpm and 200rpm), and temperature (20-55°C). Dye removal by the bacterium for 50mg/L of dye was > 97.0% within 72h of incubation at pH 11.0 in stationary condition. Bacterium had excellent reusability i.e. > 97% dye removal for up to 5 cycles. Moreover, bacterium has the potential for co-removal of chromium (VI) (3.5-28mg/L), and also almost complete dye removal in presence of high amount of NaCl. Liquid chromatography-mass spectrometry showed degradation as the mechanism of dye removal. Application of the bacterium to MO dye spiked real textile wastewater showed excellent dye removal. Phyto-toxicity assessment conducted on Vigna radiata and Triticum aestivum seeds, showed 100% germination of biotreated textile wastewater indicating its reuse potential.

Development of cost functions for wastewater treatment by sequential batch reactor

Sequential batch reactor is widely used for industrial wastewater treatment. To consider sequential batch reactor for biological treatment of wastewater at a specific site, it is essential to ensure economy and sustainability. An approach for scrutiny of economic aspects may be based upon use of cost functions to compare sequential batch reactor and other technologies. Such approach will enable to conduct prudent analysis and select the most economic treatment scheme for a particular project. In most of published studies, the cost functions for conventional wastewater treatment systems are described with historic or some other data available to the investigators. No detailed engineering exercise related to cost functions for sequential batch reactor is cited in earlier research studies. In this document the novel and appropriate methodology has been presented to develop cost functions based on engineering, estimation and statistical approach to forecast cost for sequential batch reactor based wastewater treatment system.

Removal of nutrients from synthetic wastewater by different Brazilian chlorophyte strains in batch bioreactors under various light regimes.

With the increase in pollution and improper waste disposal, aquatic ecosystems are experiencing escalating degradation leading to various detrimental effects, including eutrophication and adverse impacts on the health of the population reliant on these water resources. Consequently, microalgae have demonstrated efficacy in nutrient removal, minimal environmental disruption, and superior cost-effectiveness in comparison to traditional treatment methods. Thus, this study aimed to investigate wastewater treatment in an aerobic batch system, using two strains of non-axenic mixotrophic chlorophytes, Chlorella sp. and Desmodesmus sp., across distinct light regimes: continuous light exposure for 24h, a photoperiod of 12h light and 12h darkness, and complete absence of light for 24h. The Desmodesmus sp. strain exhibited superior efficiency in the proposed biological treatment, yielding more favorable nutrient removal results across all conditions, except for total nitrogen removal under the 24-h continuous light condition in which Chlorella sp. removed 0.199 ± 0.02% by biomass. In other parameters, Desmodesmus sp., remediated by biomass 0.408 ± 0.013% of inorganic phosphorus in 24h light, 0.372 ± 0.011% of COD and 0.416 ± 0.004% of carbohydrate in 24h dark. While Chlorella sp. removed 0.221 ± 0.01% of inorganic phosphorus in 24h light, 0.164 ± 0.02% of COD in 24h light and 0.214 ± 0.002% of carbohydrates in 24h dark. Nevertheless, both strains displayed potential as viable alternatives for wastewater biological treatment, indicating that nutrient removal is achievable across all tested light conditions, albeit with variations in efficiency depending on the specific nutrient type.

Biological Wastewater Treatment Using Higher Aquatic Plants

This article presents the results of research on the biological treatment of various industrial and domestic wastewater using higher aquatic plants. The experiments examined the possibility of biological treatment of mining wastewater on a semi-industrial scale using <i>Eichhornia crassipes </i>Solms, <i>Pistia stratiotes</i> L. <i>Azolla</i> <i>caroliniana </i>and <i>Lemna minor </i>and their features in biological treatment are identified. Eichhornia and pistia plants are important because they show high efficiency in wastewater treatment due to their high adsorption properties, with frequent renewal of biomass in ponds, the phytoremediation capacity of higher aquatic plants is 51% per day due to the adsorption properties of plants, based on calculations, it is possible to propose cleaning pools with a volume of 1000 cubic meters of water for 5 days, through the renewal of plant culture every 1-3 days. The use of purification methods in this way recommends the construction of additional structures. In this case, depending on the volume of wastewater from the plant, it is necessary to build additional bioponds, create a water transfer system, and also build additional bioponds for the purpose of growing biomass or increasing plants. Only then can the biological purification method we recommend be used on an industrial scale or at an industrial enterprise to purify wastewater in an environmentally safe and cost-effective manner.

Electrochemically Coupled Anaerobic Membrane Bioreactor Facilitates Remediation of Microplastic-Containing Wastewater

Ubiquitous microplastics (MPs) severely affect the efficiency of anaerobic membrane bioreactors (AMBR) for wastewater treatment and energy recovery by inhibiting the metabolic activity of anaerobic microorganisms. The electrochemical system can not only accelerate waste metabolism but also improve microbial resistance by promoting interspecies electron transfer within the system, which has broad application potential in the remediation of MPs wastewater. This paper attempts to evaluate the effect of electrical stimulation on the efficiency of biological wastewater treatment processes containing MPs employing an electrochemical system coupled to an anaerobic membrane bioreactor (ECAMBR). The results showed that although MP exposure inhibited methanogenic performance, electrical stimulation effectively alleviated this inhibitory effect. Further analysis showed that microplastics increased cell damage and affected enzyme activity, but electrical stimulation could affect the stress response of microorganisms, leading to changes in their cell viability and enzyme activities. The 16S-rRNA sequencing indicated that the highest abundance of hydrolytic–acidogenic bacteria Firmicutes and Bacteroidota was found at the phylum level, whereas at the genus level, it was Christensenellaceae_R-7_group, and methanogens were dominated by Methylomonas, Methyloversatilis, and Methylobacter. Functional prediction analysis indicated that carbohydrate metabolism, amino acid metabolism, and energy metabolism were the dominant metabolic pathways and that electrical stimulation could enhance their activities. This study demonstrated the important role of electrochemical stimulation in the remediation of wastewater containing high concentrations of MPs.

Microbial removal of phenol and ammonium from acidic wastewater using recycled polyurethane: Performance and mechanism

Using solid waste as fortifying agent can improve the efficiency of biological treatment of wastewater and solve the problem of difficult treatment of solid waste. In this study, the waste polyurethane was used as the immobilized carrier of strain, and the repair effect of the immobilized system on acidic phenol-containing wastewater was investigated under different conditions and the mechanism of microbial degradation and acid resistance enhanced by the carrier was discussed. The results showed that polyurethane immobilization improved microorganisms' resistance to harsh environments, strain growth, and pollutant removal efficiency in wastewater. Optimizing the culture conditions of the immobilized system increased the average removal efficiency of phenol and NH4+ by 68.77 % and 135.12 %, respectively, compared to the free strain. Additionally, immobilization enhanced the strain's tolerance to phenol, achieving efficient removal of high-concentration phenol-containing wastewater (2200 mg L−1) that free bacteria could not handle. In the MBBR reactor, the immobilized polyurethane-strain Hly3 system operated stably for 20 cycles, removing 95 % of 2000 mg L−1 phenol and 65 % of 100 mg L−1 NH4+. The mechanism by which the carrier improved microbial degradation and acid resistance was studied. It was found that carrier protection, accelerated material transfer, enhanced strain resistance, and increased activity of the acid-resistant reaction system were the main reasons for the improved acid resistance and degradation ability of strain Hly3. From an environmental and economic perspective, recycling polyurethane buffer materials as carriers to immobilize microorganisms offers a cost-effective wastewater treatment solution, also addressing the challenge of difficult solid plastic waste treatment.

A novel Zobellella endophytica W14 strain for nitrogen removal from hypersaline wastewater through simultaneous nitrification and denitrification

To address the challenges associated with biological treatment of high-salinity wastewater, a novel salt-tolerant strain, Zobellella endophytica W14, was isolated. This strain exhibited heterotrophic nitrification-aerobic denitrification (HN-AD) capabilities. Strain W14 could grow and remove ammonium in high-salinity environments with salinity levels ranging from 0 to 11% (w/v). At 5% salinity, strain W14 demonstrated high removal efficiencies for nitrite, ammonium, and nitrate (100%, 99.58%, and 98.85%, respectively), when these compounds were provided as the single source of nitrogen. In cases of mixed nitrogen sources, total nitrogen removal efficiency of strain reached 95.22%. The nitrogen balance analysis confirmed the utilization of nitrogen sources by strain W14 through both assimilation and dissimilation. Through the amplification of functional genes involved in nitrogen metabolism (i.e., hao, napA, nirS, and nosZ), the nitrogen metabolism pathway of strain W14 was predicted to be: NH₄⁺ → NH₂OH → NO₂⁻ → NO₃⁻ → NO₂⁻ → NO → N₂O → N₂. The study reveals that the novel W14 strain can efficiently remove total nitrogen from high-salinity wastewater and has significant potential for biological treatment of such wastewater.

Influence of bisphenol A concentration on organic matter removal and nitrification in biological wastewater treatment

Microplastics and plastic additives have become ubiquitous in our environment, posing a major challenge to wastewater treatment processes. This study investigated the impact of Bisphenol A (BPA), a common plastic additive, on the efficiency of organic matter removal and nitrification in biological wastewater treatment. The obtained results indicated that a BPA concentration of 10 mg·L−1 in the influent affected the Chemical Oxygen Demand (COD) in the effluent. In comparison, concentrations of 1 or 5 mg·L−1 did not show such noticeable differences. Additionally, an increase in BPA load inhibited the nitrification process, resulting in a high concentration of nitrogen in its ammoniacal form in the effluent when the BPA concentration was increased to 10 mg·L−1. In fact, the microbial community analysis revealed a considerable reduction of Nitrosomonas in the reactor fed with wastewater containing 10 mg·L−1 of BPA. Despite compromising the nitrification process, this situation did not deprive the biomass of its ability to remove BPA from the system, as this component was not detected in the effluent once the microorganisms completed their adaptation process. 16 S rRNA gene sequencing showed that the predominant phyla across all samples were associated with Proteobacteria, Bacteroidota, Patescibacteria and Actinobacteriota, similar to previous studies.

Enhanced anaerobic reduction of nitrobenzene under hypersaline fluctuation: Glycine betaine metabolism and microbial osmoadaptation mechanisms

High salinity, particularly large fluctuations in salinity, poses a significant threat to the biological treatment of high-salt industrial wastewater, while glycine betaine (GB) is commonly used for osmotic pressure balance. However, the GB metabolism mechanism and the effect of GB addition on microbial osmoadaptation responding to salt perturbations are still unclear. This study investigated the effect of GB on the stability of anaerobic process in nitrobenzene reduction under various salt perturbations and further explored the microbial osmoadaptation and metabolism mechanism. The nitrobenzene reduction was observably improved with GB addition (R+), and the microbial resilience increased due to repeated salt shocks. The generation of acetic acid showed a 46.21 % decrease in R+ compared to that without GB addition (R-) at 3 % salinity. Meanwhile, the intracellular GB concentration reached 10.76 mg L−1 to 54.76 mg L−1 with salinity increasing from 1.5 % to 6 %. 16S rRNA analysis revealed that the osmoadaptation period was shortened in R+ through the rapid osmoadaptation of salt-intolerant microorganisms (such as Propionibacteriaceae and SBR1031) and the massive enrichment of salt-tolerant microorganisms (such as Glutamicibacter). Besides, the resistance to hypersaline disturbance improved by the increasing size and complexity of the microbial community network. Moreover, the metagenomic analysis revealed that the abundance of genes involved in microbial metabolism was significantly enhanced in R+, indicating a more efficient metabolic efficiency and electrons transfer with GB addition under high-salt environments. This study provides vital insights into GB metabolism and microbial osmoadaptation responding to salt perturbations in long-term high-salt wastewater biotreatment.