Biological Wastewater Treatment Processes Research Articles

Microbiome structure and function in parallel full-scale aerobic granular sludge and activated sludge processes.

Aerobic granular sludge (AGS) and conventional activated sludge (CAS) are two different biological wastewater treatment processes. AGS consists of self-immobilised microorganisms that are transformed into spherical biofilms, whereas CAS has floccular sludge of lower density. In this study, we investigated the treatment performance and microbiome dynamics of two full-scale AGS reactors and a parallel CAS system at a municipal WWTP in Sweden. Both systems produced low effluent concentrations, with some fluctuations in phosphate and nitrate mainly due to variations in organic substrate availability. The microbial diversity was slightly higher in the AGS, with different dynamics in the microbiome over time. Seasonal periodicity was observed in both sludge types, with a larger shift in the CAS microbiome compared to the AGS. Groups important for reactor function, such as ammonia-oxidising bacteria (AOB), nitrite-oxidising bacteria (NOB), polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs), followed similar trends in both systems, with higher relative abundances of PAOs and GAOs in the AGS. However, microbial composition and dynamics differed between the two systems at the genus level. For instance, among PAOs, Tetrasphaera was more prevalent in the AGS, while Dechloromonas was more common in the CAS. Among NOB, Ca. Nitrotoga had a higher relative abundance in the AGS, while Nitrospira was the main nitrifier in the CAS. Furthermore, network analysis revealed the clustering of the various genera within the guilds to modules with different temporal patterns, suggesting functional redundancy in both AGS and CAS. KEY POINTS: • Microbial community succession in parallel full-scale aerobic granular sludge (AGS) and conventional activated sludge (CAS) processes. • Higher periodicity in microbial community structure in CAS compared to in AGS. • Similar functional groups between AGS and CAS but different composition and dynamics at genus level.

Efficient nitrogen removal by microalgal-bacterial granular sludge-marimo coupling process

Current biological wastewater treatment processes usually have a drawback of insufficient nitrogen (N) removal, contributing to the ubiquitous eutrophication of aquatic ecosystems globally. To address such a challenging situation, this study explored an innovative microalgal-bacterial granular sludge-marimo (MBGS-MA) coupling process. The process removed 83.4 % of N with the effluent N concentration of 4.0 mg/L. With the growth of MBGS, there was a shift towards genes associated with nitrification and denitrification, and away from ammonia assimilation genes, revealing internal mechanism of the shift of N removal pathway. Contrarily, MA could use gaseous N2 with the N fixing genes in MA enriched, and the genes abundance related to assimilatory nitrate reduction were also raised under the mutualistic interactions between Proteobacteria and Cyanobacteria, which was beneficial to achieve efficient N removal. These findings may open a new horizon for developing innovative hybrid microalgal-bacterial processes with the aim of high-efficiency N removal from wastewater.

Ultrasound, Hydrogen Peroxide, and Persulfate in Hybrid Advanced Oxidation Processes(AOPs): A Comparative Study for the Reuse of Sewage Treatment Effluent

Objectives : As the variety and quantity of recalcitrant pollutants such as pharmaceuticals, pesticides, endocrine disruptors, and cosmetic products discharged into water bodies steadily increase, the need for AOPs following biological wastewater treatment processes is growing. In this study, we compared the Total Organic Carbon (TOC) removal capabilities of conventional AOPs, ultrasound, hydrogen peroxide, and persulfate-based multiple AOPs on the final effluent of S wastewater treatment plant. The study also evaluated the feasibility of wastewater reuse by examining the optimal operating conditions of the applied AOPs.Methods : The removal characteristics of TOC were investigated based on reaction time, US frequency, and oxidant dosage for the following conditions: ultrasound (US) alone, individual treatments with hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) and persulfate (PS) as oxidants, combined US/H<sub>2</sub>O<sub>2</sub> and US/PS dual AOPs, and a US/PS/H<sub>2</sub>O<sub>2</sub> multi-AOPs system.Results and Discussion : Only US oxidation treatment at 80 kHz for 60 minutes resulted in a 14.4% TOC removal efficiency. Individual treatment with H<sub>2</sub>O<sub>2</sub> at 174 mM showed 69.2% removal efficiency, while persulfate oxidation treatment at 43.5 mM showed 13.8%. The PS/H<sub>2</sub>O<sub>2</sub> oxidation treatment showed 68.5% removal efficiency at 174 mM H<sub>2</sub>O<sub>2</sub> and 0.52 mM PS, and an 85.3% removal efficiency at 2.08 mM PS and 350 mM H<sub>2</sub>O<sub>2</sub> conditions. Under the same 80 kHz ultrasound conditions, the combined US and other oxidant treatment resulted in an increased TOC removal efficiency: 87.8% for US/H<sub>2</sub>O<sub>2</sub> at 174 mM H<sub>2</sub>O<sub>2</sub>, and 81.9% for US/PS at 43.5 mM PS. Additionally, the multi-treatment with US, PS, and H<sub>2</sub>O<sub>2</sub> showed a removal efficiency of 87.0% at 2.08 mM PS and 350 mM H<sub>2</sub>O<sub>2</sub>, and 91.1% at 174 mM H<sub>2</sub>O<sub>2</sub> and 0.52 mM PS conditions.Conclusion : In this study, among the AOPs, the oxidation treatment with US/PS/H<sub>2</sub>O<sub>2</sub> exhibited the highest TOC removal efficiency at 91.1%. The integration of chemical oxidants with US demonstrated significant improvement in TOC removal capabilities, with PS showing superior performance at the same concentration conditions among the utilized chemical oxidants in the multi-AOPs. Although H<sub>2</sub>O<sub>2</sub> also displayed commendable TOC removal abilities, its oxidation efficiency was lower at low concentration injections, whereas higher concentrations of H<sub>2</sub>O<sub>2</sub> injections proved to be more effective in oxidation.

Global occurrence of organic micropollutants in surface and ground water: Highlighting the importance of wastewater sanitation to tackle organic micropollutants

The occurrence, fate and distribution of organic micropollutants (OMPs) in different water matrices is of increasing concern due to the negative effects towards flora, fauna and human health. This metadata study provides an updated picture of the global occurrence of OMPs in freshwater and wastewater in five geographical regions, and illustrates how socioeconomic factors are key elements that influence the concentration of these OMPs in the different water matrices. The study also aims to provide a collated database of OMPs removal efficiencies achieved by the different biological treatment technologies. Our findings demonstrated that OMPs like acetaminophen, ibuprofen, and triclosan are present globally in freshwater (> 500 ng/L) and wastewater (> 10, 000 ng/L), and at relatively higher concentrations than the other evaluated OMPs. Significant correlations between OMPs concentration in wastewater versus freshwater demonstrated wastewater to be a potential source of certain OMPs to the freshwater environment. This was further confirmed through correlation between OMPs concentration and socioeconomic factors like infrastructure index and governance index in both wastewater and freshwater. These results highlighted the importance of wastewater sanitation to control and reduce OMPs dissemination in the environment. Thus, various types of biological wastewater treatment processes including activated sludge processes, biofilm processes, wetland and lagoon, and membrane bioreactor were analyzed for their OMP’s removal efficiencies. Findings demonstrated that advanced processes like membrane bioreactors (MBR) may not always outperform other low-costs biotechnologies in the treatment of OMPs (e.g., bisphenol A removal by activated sludge with anoxic and oxic zone, AS-AAO was 93% versus MBR at 89%). But rather, the removal efficiency will depend on pollutant properties and certain operational parameters such as hydraulic retention time, treatment capacity, and removal efficiency of total suspended solids.

A Modeling Analysis of Wastewater Heat Recovery Effects on Wastewater Treatment Plant Nitrification

A global shift towards renewable energy production, driven primarily by the challenges posed by climate change, is currently underway. In this context, the utilization of heat recovery from municipal wastewater emerges as a promising green technology. Notably, the advantage of implementing energy recovery in sewers, as opposed to wastewater treatment plants (WWTPs), lies in the higher temperature of the wastewater and its proximity to potential heat users. Despite these benefits, concerns arise regarding the potential adverse effects on biological wastewater treatment processes downstream of the heat recovery section, particularly during colder seasons. This paper seeks to assess the impact of a heat recovery system along the sewer network on the efficiency of biological wastewater treatment processes. The methodology involves a modeling analysis of a real sewage network in Italy. Under typical northern Italy climate conditions, the results demonstrate the feasibility of heat recovery in sewers for WWTPs designed with a sludge residence time under aerobic conditions (SRTaer) greater than 13 days. In such cases, the nitrification process remains relatively unaffected. However, for lower SRTaer values, a case-specific feasibility assessment is recommended to evaluate the overall process efficiency comprehensively.

An identification algorithm of switched Box-Jenkins systems in the presence of bounded disturbances: An approach for approximating complex biological wastewater treatment models

This paper focuses on the development of linear Switched Box–Jenkins (SBJ) models for approximating complex dynamical models of biological wastewater treatment processes. We discuss the adaptation of these processes to the SBJ framework, showing the model's generality and flexibility as a class of switched systems that can offer accurate predictions for complex and nonlinear dynamics. This approach of modeling enables real-time data reconciliation from experiments and allows the design of model-based control strategies. Through the extension of the Outer Bounding Ellipsoids (OBEs) algorithm, the paper introduces an online two-stage parameter identification algorithm that effectively handles bounded disturbances for SBJ models. Using the OBE method relaxes the stochastic assumptions on disturbances, which may not be satisfied in practice, particularly for biological and environmental fluctuations. The proposed decomposed OBE algorithm separately identifies the switching patterns and parameters of linear submodels, conducting parameter identification in two distinct phases for input/output and disturbance/output submodels. The efficacy of this approach is shown via simulation results validated against both ADM1 and PBM models, demonstrating the proposed algorithm's capability to accurately predict outputs from different biological wastewater treatment models.

Mathematical Model of Oxygen Regime Analysis in a Bioreactor

Purpose. Today, aeration tanks are widely used to treat industrial and municipal wastewater. Assessing the efficiency of water treatment in aeration tanks under different operating conditions is an important task. To solve this problem, it is necessary to have mathematical models that allow to quickly obtain data on the effect of treatment in aeration tanks. The main objective of this work is to develop a numerical box model to determine the efficiency of wastewater treatment in an aeration tank. Methodology. For mathematical modeling of the biological wastewater treatment process in a bioreactor, zero-dimensional material balance equations are used, which are written in relation to the concentration of substrate, activated sludge, and dissolved oxygen in wastewater. The Monod model is used to calculate the substrate oxidation process. The Euler method is used to integrate the modeling equations. A simplified model of biological water treatment in a bioreactor is considered, which makes it possible to obtain an analytical solution to the problem. The obtained analytical expression makes it possible to quickly determine the change in the concentration of dissolved oxygen in wastewater depending on the change in the concentration of activated sludge in the bioreactor. The constructed numerical model makes it possible to determine the dynamics of changes in the concentration of contaminants, activated sludge and oxygen in wastewater during their stay in the bioreactor. Findings. A tool for theoretical evaluation of the efficiency of biological wastewater treatment in an aeration tank is proposed. A numerical model has been built that allows determining the concentration of dissolved oxygen, substrate and activated sludge at the outlet of the aeration tank. Originality. An effective numerical model has been developed that allows to quickly calculate the dynamics of wastewater treatment in a bioreactor and, based on this information, to evaluate the efficiency of the reactor. Practical value. The constructed mathematical model can be useful in the reconstruction of biological wastewater treatment facilities, as well as at the design stage of bioreactors to take into account their operation under different operating conditions. A computer program has been developed that implements the constructed numerical model. The results of a computer experiment are presented.

Research of the process of biological wastewater treatment under conditions of uneven load of the treatment system

The main purpose of the article is to develop a multifactorial model for rapid assessment of the efficiency of biological wastewater treatment reactors. A mathematical model of the process of biological wastewater treatment has been developed based on: changes in the concentration of organic contaminants in the bioreactor over time, taking into account the uneven flow of wastewater to the treatment plant, the process of substrate entering the bioreactor (different amounts may enter at different times). The software implementation of the proposed algorithm for solving the corresponding model problem in Python is carried out. The results of computer experiments on the study of the efficiency of wastewater treatment in biological treatment reactors for different operating conditions of facilities are presented. In particular, such processes were considered with taking into account the unevenness of the load, because the maximum cleaning loads are in the morning and in the evening. The task was solved to simulate a real situation and show how cleaning takes place at the maximum load at a certain time of the day. The results obtained will be useful for calculations in the design of biological treatment facilities or in the reconstruction of existing bioreactors for their prospective operation under new operating conditions.

Advances in Biological Wastewater Treatment Processes: Focus on Low-Carbon Energy and Resource Recovery in Biorefinery Context.

Advancements in biological wastewater treatment with sustainable and circularity approaches have a wide scope of application. Biological wastewater treatment is widely used to remove/recover organic pollutants and nutrients from a diverse wastewater spectrum. However, conventional biological processes face challenges, such as low efficiency, high energy consumption, and the generation of excess sludge. To overcome these limitations, integrated strategies that combine biological treatment with other physical, chemical, or biological methods have been developed and applied in recent years. This review emphasizes the recent advances in integrated strategies for biological wastewater treatment, focusing on their mechanisms, benefits, challenges, and prospects. The review also discusses the potential applications of integrated strategies for diverse wastewater treatment towards green energy and resource recovery, along with low-carbon fuel production. Biological treatment methods, viz., bioremediation, electro-coagulation, electro-flocculation, electro-Fenton, advanced oxidation, electro-oxidation, bioelectrochemical systems, and photo-remediation, are summarized with respect to non-genetically modified metabolic reactions. Different conducting materials (CMs) play a significant role in mass/charge transfer metabolic processes and aid in enhancing fermentation rates. Carbon, metal, and nano-based CMs hybridization in different processes provide favorable conditions to the fermentative biocatalyst and trigger their activity towards overcoming the limitations of the conventional process. The emerging field of nanotechnology provides novel additional opportunities to surmount the constraints of conventional process for enhanced waste remediation and resource valorization. Holistically, integrated strategies are promising alternatives for improving the efficiency and effectiveness of biological wastewater treatment while also contributing to the circular economy and environmental protection.

Modeling greenhouse gas emissions from biological wastewater treatment process with experimental verification: A case study of paper mill

Wastewater treatment plants (WWTPs) have been regarded as the main sources of greenhouse gas (GHG) emissions. This study compares the influent characteristics of industrial wastewater represented by the WWTP of paper mill and that of domestic sewage represented by the Benchmark Simulation Model No. 1 (BSM1) under stormy weather. The various sources of GHG emissions from the two processes are calculated, and the contribution of each source to the total GHG emissions is assessed. Firstly, based on the mass balance analysis and the recognized emission factors, a GHG emission calculation model was established for the on-site and off-site GHG emission sources from the WWTP of paper mill. Simultaneously, a GHG emission experimental model was established by determining the dissolved concentrations of carbon dioxide (CO2) and nitrous oxide (N2O) in the papermaking wastewater, to verify the accuracy of the developed GHG calculation model. Subsequently, an optimum aeration rate for the paper mill was investigated to comply with the discharging norms. Under the optimum aeration rate of 10 h−1, the obtained calculation accuracies of CO2 and N2O emissions were 94.6 % and 91.1 %, respectively. The mean total GHG emission in the WWTP of paper mill was 550 kg CO2-eq·h−1, of which 44.6 % came from the on-site emission sources and 55.4 % from the off-site emission sources. It was also uncovered that the electrical consumption for aeration was the largest contributor to the total GHG emissions with a proportion of 25.2 %, revealing that the control strategy of the aeration rate is highly significant in reducing GHG emissions in WWTP of paper mills.

Comparative analysis of Greenhouse Gas Emissions from Biological Wastewater Treatment Processes: A Case Study in Gyeongsangbuk-do, Korea

Objectives:This study compared greenhouse gas emissions from various biological treatment processes at wastewater treatment plants in City A, Gyeongsangbuk-do. Methods:Four wastewater treatment plants were selected by size and treatment process, and flow rate and water quality parameters from 2020 to 2022 were used. The amount of greenhouse gases such as methane, nitrous oxide, and carbon dioxide generated was calculated according to the IPCC and Ministry of Environment calculation formulas. Results and Discussion:Regardless of the biological wastewater treatment processes, the greenhouse gas emissions of all plants were higher according to the Ministry of Environment standards than the IPCC method. However, this may be because it was not applied to variables that are difficult to confirm, such as correction coefficients. Among biological treatment processes, the greenhouse gas emissions of A2O were higher than those of SBR.Conclusion:The results of this study can be used to calculate greenhouse gas emissions from biological wastewater treatment processes and prepare their reduction plans.

Dynamic Modelling, Process Control, and Monitoring of Selected Biological and Advanced Oxidation Processes for Wastewater Treatment: A Review of Recent Developments.

This review emphasizes the significance of formulating control strategies for biological and advanced oxidation process (AOP)-based wastewater treatment systems. The aim is to guarantee that the effluent quality continuously aligns with environmental regulations while operating costs are minimized. It highlights the significance of understanding the dynamic behaviour of the process in developing effective control schemes. The most common process control strategies in wastewater treatment plants (WWTPs) are explained and listed. It is emphasized that the proper control scheme should be selected based on the process dynamic behaviour and control goal. This study further discusses the challenges associated with the control of wastewater treatment processes, including inadequacies in developed models, the limitations of most control strategies to the simulation stage, the imperative requirement for real-time data, and the financial and technical intricacies associated with implementing advanced controller hardware. It is discussed that the necessity of the availability of real-time data to achieve reliable control can be achieved by implementing proper, accurate hardware sensors in suitable locations of the process or by developing and implementing soft sensors. This study recommends further investigation on available actuators and the criteria for choosing the most appropriate one to achieve robust and reliable control in WWTPs, especially for biological and AOP-based treatment approaches.

A new understanding on the prerequisite of antibiotic biodegradation in wastewater treatment: Adhesive behavior between antibiotic-degrading bacteria and ciprofloxacin

The extensive exploration of antibiotic biodegradation by antibiotic-degrading bacteria in biological wastewater treatment processes has left a notable gap in understanding the behavior of these bacteria when exposed to antibiotics and the initiation of biodegradation processes. This study, therefore, delves into the adhesive behavior of Paraclostridium bifermentans, isolated from a bioreactor treating ciprofloxacin-laden wastewater, towards ciprofloxacin molecules. For the first time, this behavior is observed and characterized through quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy. The investigation further extends to identify key regulatory factors and mechanisms governing this adhesive behavior through a comparative proteomics analysis. The results reveal the dominance of extracellular proteins, particularly those involved in nucleotide binding, hydrolase, and transferase, in the adhesion process. These proteins play pivotal roles through direct chemical binding and the regulation of signaling molecule. Furthermore, QCM-D measurements provide evidence that transferase-related signaling molecules, especially tyrosine, augment the binding between ciprofloxacin and transferases, resulting in enhance ciprofloxacin removal by P. bifermentans (increased by ∼1.2-fold). This suggests a role for transferase-related signaling molecules in manipulating the adhesive behavior of P. bifermentans towards ciprofloxacin. These findings contribute to a new understanding of the prerequisites for antibiotic biodegradation and offer potential strategies for improving the application of antibiotic-degrading bacteria in the treatment of antibiotics-laden wastewater.

CONTROL MODEL OF THE WASTEWATER TREATMENT PROCESS

The main stages of biological wastewater treatment are studied, existing models and control of these processes are analyzed, methods for solving the system of differential equations and the disadvantages of each model when used for control purposes are shown. To find the optimal mode using models of the biological treatment process, various criteria are used. The parameters and variables of the process of biological wastewater treatment by microorganisms in aeration tanks are determined - control and exciting influences, as well as input and output quantities, and a system of differential equations connecting them is established. The feasibility of using MatLAB software for building an analytical model and its solution, and Simulink for visual modeling is shown. Keywords: wastewater, model, aero tank, biological treatment, management.

Differential biotransformation of micropollutants in conventional activated sludge and up-flow anaerobic sludge blanket processes

We report differential micropollutant biotransformations in a conventional activated sludge (CAS) process and a pilot-scale up-flow anaerobic sludge blanket (UASB) process operating in parallel at the same wastewater treatment plant.

Short-term influence of polytetrafluoroethylene micro/nano-plastics on the inhibition of copper and/or ciprofloxacin on the nitrifying sludge activities based on concentration addition and independent action models

Short-term influence of polytetrafluoroethylene micro/nano-plastics (PTFE-MPs/NPs) on the inhibition of copper (Cu2+) and/or ciprofloxacin (CIP) on the nitrifying sludge activities was explored based on concentration addition (CA) and independent action (IA) models. The half maximal inhibitory concentration (IC50) of Cu2+, CIP, PTFE-MPs (3 μm), and PTFE-NPs (800 nm) on the specific ammonium oxidation rate (SAOR) of nitrifying sludge was 64.57, 51.29, 102.33 and 93.33 mg L−1, respectively, while those on the specific nitrite oxidation rate (SNOR) of nitrifying sludge were 77.62, 32.36, 104.70 and 97.72 mg L−1, respectively. Among the five binary mixtures and two ternary mixtures composed by Cu2+, CIP, and/or PTFE-MPs/NPs, it was found that the two joint inhibitory actions from ternary mixtures on the SAOR and SNOR of the sludge showed time-dependent characteristics by analyzing of CA and IA models, while the five combined inhibitory effects from different binary mixtures did not all have time-dependent features. The two joint inhibition actions from diverse ternary mixtures on the SAOR at the exposure time of 60 min and on the SNOR at 90 min showed always concentration-dependent features, while the combined inhibitions with concentration-dependent characteristics had never been observed in the binary Cu2+ and PTFE-NPs mixtures at different exposure time. The Cu2+, CIP, and PTFE-MPs mixtures (or Cu2+, CIP, and PTFE-NPs mixtures) had synergistic actions on the SAOR at 90 min and antagonistic effects on the SNOR at 60 min based on CA and IA models, and these combined inhibitions did not exhibit concentration-dependent characteristics. In contrast, the joint inhibitory effects (on the SAOR and SNOR) with concentration-dependent features were found in the binary mixtures of CIP and PTFE-MPs at different exposure time, and the join inhibition changed from synergism to antagonism as the increasing concentration of mixed CIP and PTFE-MPs. This study provides novel perspectives for understanding the combined influence of plastic particles with different sizes, antibiotics, and heavy metals on the biological wastewater treatment process.

Combined biological and chemical-physical processes for domestic wastewater treatment

The present study aims to investigate the possibility of domestic wastewater treatment using biological system combined with chemical-physical processes, including Upflow Sludge Blanket Filtration (USBF) technology and PolyAluminium Chloride (PAC). Experimental results showed that the added PAC content played an essential role in improving the treatment efficiency and reached National Technical Regulation on domestic wastewater QCVN 14:2008/BTNMT (Column A) for BOD5. With Jar-test results, the optimal pH of 7.0 and the PAC dosage of 170 mg/L were recorded with the highest removal efficiencies for suspended solids and organic matter. In the modified USBF bioreactor, the findings illustrated the pollutant removal efficiencies such as Biochemical Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), and Suspended Solids (SS) were equal to 96.2 ± 1.4%, 85.8 ± 4.4% and 99.3 ± 2.1%, respectively. In the future, this USBF-based advanced technology has the potential to play a significant role in addressing water scarcity through wastewater reclamation and reuse.

Recent advances in remediation strategies for mitigating the impacts of emerging pollutants in water and ensuring environmental sustainability

The proliferation of emerging pollutants (EPs), encompassing a range of substances such as phthalates, phenolics, pharmaceuticals, pesticides, personal care products, surfactants, and disinfection agents, has become a significant global concern due to their potential risks to the environment and human well-being. Over the past two decades, numerous research studies have investigated the presence of EPs in wastewater and aquatic ecosystems, with the United States Environmental Protection Agency (USEPA) categorizing these newly introduced chemical compounds as emerging contaminants due to their poorly understood impact. EPs have been linked to adverse health effects in humans, including genotoxic and cytotoxic effects, as well as conditions such as obesity, diabetes, cardiovascular disease, and reproductive abnormalities, often associated with their estrogenic action. Microalgae have shown promise in the detoxification of both inorganic and organic contaminants, and several large-scale microalgal systems for wastewater treatment have been developed. However, the progress of algal bioremediation can be influenced by accidental contaminations and operational challenges encountered in pilot-scale research. Microalgae employ various processes, such as bioadsorption, biouptake, and biodegradation, to effectively remediate EPs. During microalgal biodegradation, complex chemical compounds are transformed into simpler substances through catalytic metabolic degradation. Integrating algal bioremediation with existing treatment methodologies offers a viable approach for efficiently eliminating EPs from wastewater. This review focuses on the use of algal-based biological remediation processes for wastewater treatment, the environmental impacts of EPs, and the challenges associated with implementing algal bioremediation systems to effectively remove emerging pollutants.

STUDY OF URBAN WASTEWATER TREATMENT PROCESSES IN THE SYSTEM OF BIOLOGICAL TREATMENT FACILITIES “AERATION TANK-MIXER – SECONDARY SEDIMENTATION TANK”

The paper examines the features of the biological purification process in the “aeration tank-mixer – secondary settling tank” system. Factors influencing the course of processes were determined, and an experimental study of this process was carried out. After processing the results, models are proposed that describe the course of the activated sludge regeneration process and directly the process of biological wastewater treatment. The results of the calculation were analyzed, the mutual influence of individual factors on the course of the biological purification process was investigated and analyzed. The models obtained in the work allow, without conducting additional experiments, to study the process of regeneration of activated sludge depending on the concentration of sludge and its consumption, as well as to study the process of wastewater treatment taking into account its characteristics (costs, concentrations of pollutants), the dose of sludge coming from the regenerator, concentrations dissolved oxygen. It is advisable to use the proposed models for the analysis of the process of biological wastewater treatment in the system “aeration tank-mixer – secondary settling tank” and for quick response to changes occurring in the treatment process. This will prevent insufficiently treated wastewater from entering the reservoir and reduce its negative impact on the environment.

Assessing the impact of low organic loading on effluent safety in wastewater treatment: Insights from an activated sludge reactor study

In this study, an organic loading (OL) of 300 mg/(L d) was set as the relative normal condition (OL-300), while 150 mg/(L d) was chosen as the condition reflecting excessively low organic loading (OL-150) to thoroughly assess the associated risks in the effluent of the biological wastewater treatment process. Compared with OL-300, OL-150 did not lead to a significant decrease in dissolved organic carbon (DOC) concentration, but it did improve dissolved organic nitrogen (DON) levels by ∼63 %. Interestingly, the dissolved organic matter (DOM) exhibited higher susceptibility to transformation into chlorinated disinfection by-products (Cl-DBPs) in OL-150, resulting in an increase in the compound number of Cl-DBPs by ∼16 %. Additionally, OL-150 induced nutrient stress, which promoted engendered human bacterial pathogens (HBPs) survival by ∼32 % and led to ∼51 % increase in the antibiotic resistance genes (ARGs) abundance through horizontal gene transfer (HGT). These findings highlight the importance of carefully considering the potential risks associated with low organic loading strategies in wastewater treatment processes.