Biochemical Treatment Processes Research Articles

Deciphering the core bacterial community structure and function and their response to environmental factors in activated sludge from pharmaceutical wastewater treatment plants

Pharmaceutical wastewater is recognized for its heightened concentrations of organic pollutants, and biological treatment stands out as an effective technology to remove these organic pollution. Therefore, a comprehensive exploration of core bacterial community compositions, functions, and their responses to environmental factors in pharmaceutical wastewater treatment plants (PWWTPs) is important for understanding the removal mechanism of these organic pollutants. This study comprehensively investigated 36 activated sludge (AS) samples from 15 PWWTPs in China. The results revealed that Proteobacteria (45.41%) was the dominant phylum in AS samples, followed by Bacteroidetes (19.54%) and Chloroflexi (4.13%). While the dominant genera were similar in both aerobic and anaerobic treatment processes, their relative abundances exhibited significant variations. Genera like HA73, Kosmotoga, and Desulfovibrio were more abundant during anaerobic treatment, while Rhodoplanes, Bdellovibrio, and Hyphomicrobium dominated during aerobic treatment. 13 and 10 core operational taxonomic units (OTUs) were identified in aerobic and anaerobic sludge, respectively. Further analysis revealed that core OTUs belonging to genera Kosmotoga, Desulfovibrio, Thauera, Hyphomicrobium, and Chelativorans, were associated with key functions, including sulfur metabolism, methane metabolism, amino acid metabolism, carbohydrate metabolism, toluene degradation, and nitrogen metabolism. Furthermore, this study highlighted the crucial roles of environmental factors, such as COD, NH4+-N, SO42−, and TP, in shaping both the structure and core functions of bacterial communities within AS of PWWTPs. Notably, these factors indirectly affect functional attributes by modulating the bacterial community composition and structure in pharmaceutical wastewater. These findings provide valuable insights for optimizing the efficiency of biochemical treatment processes in PWWTPs.

Towards low-carbon papermaking wastewater treatment process based on Kriging surrogate predictive model

Papermaking wastewater contains a diverse range of organic carbon, nitrogen and other pollutants, which could lead to the emission of greenhouse gases (GHG) during biochemical treatment process. Despite the importance of decarbonizing the papermaking wastewater treatment process, the mechanisms underlying the generation of greenhouse gases remain elusive and no models currently exist to describe the process. To address this issue, this study employed benchmark simulation model No. 1 (BSM1) to simulate, the papermaking wastewater treatment process, and applied the steady-state output value of simulation to calculate the GHG emissions. Kriging surrogate model was applied to establish the emission model for GHG in the papermaking wastewater treatment process. The model provides a reference for the control and optimization of GHG emission reduction and a high accuracy was achieved with determination coefficient (R2) of above 96%. Further analysis of the parameter impact of process control on GHG emissions and the optimization effects of controllable variables contributes to the goal of reducing GHG emissions in the papermaking wastewater treatment process.

Investigation with ESI FT-ICR MS on sorbent selectivity and comprehensive molecular composition of landfill leachate dissolved organic matter.

Molecular characterization of landfill leachate dissolved organic matter (LDOM) is essential for developing effective processing techniques. However, the molecular selectivity of extraction method and ionization modes often leads to the bias of molecular characterization of LDOM. Here, seven representative sorbents were selected and electrospray ionization negative ion mode (ESI (-)) and positive ion mode (ESI (+)) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to investigate the molecular composition of different LDOM samples. Obvious sorbent selectivity during extraction procedure was observed, resulting in the underestimation of molecular diversity of LDOM from 32.7% to 69.3%. Totally, 14,000-18,000 unique molecules were obtained in a single sample, indicating the unprecedented molecular diversity of LDOM. Lignins, proteins and lipids are three major molecular groups in LDOM, and N or S containing molecules occupied 83%. Although much of total organic carbon was removed during biochemical treatment process, the molecular diversity of LDOM was not reduced because a considerable of bio-recalcitrant molecules was produced. The results uncover the sorbents selectivity and ionization modes selectivity in LDOM analysis and provided a comprehensive change of LDOM molecular composition during biochemical treatment, which benefits the development of accurate methods to remove organic carbon in landfill leachate.

Simultaneous degradation of microplastics and sludge during wet air oxidation

Microplastics (MPs) generated from daily life are commonly collected by urban sewage pipe networks and then transfer to sludge in wastewater treatment plants. Conventional biochemical treatment processes cannot degrade MPs effectively, causing an ecological risk via sludge land use. Wet air oxidation (WAO) is a promising sludge treatment technology with a strong ability to decompose complex organic matter, but its potential for the removal of MPs in sludge was unclear. In this study, three common MPs (polyethylene, polystyrene, and polyethylene terephthalate, which are called PEMPs, PSMPs, and PETMPs) were added into the sludge samples (1 g MP in 180 mL sludge), to test the effects of WAO on sludge and MPs. The results showed that WAO simultaneously degraded sludge and the PEMPs, and the two degradation processes were relatively independent when oxygen was supplied adequately. The dissolution of PSMPs and organic matter in sludge was not affected by each other, but the degradation rate was slowed down due to the interaction of ketones and benzene compounds. The hydrolysis of sludge and PETMPs was accelerated, while the hydrolyzed products such as terephthalic acid were oxidized without interfering with each other. No obvious MPs remained in the effluent, and volatile fatty acids (VFAs) were the main components, among which acetic acid accounted for 90%. When the sludge was treated with PEMPs, PSMPs, or PETMPs, the concentration of acetic acid finally accounted for 45%, 21%, and 18% of DOC. Overall, MPs can be degraded or even mineralized during sludge WAO, and humic acid derivatives, acetate, and other small molecules of alcohols, ketones, or aldehydes were the typical intermediates.

Phthalate esters in municipal sewage treatment plants: occurrence level, removal rate and optimum combination technology

The concentrations, and removal rates of five phthalate esters (PAEs) (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), diisobutyl phthalate (DiBP) and di (2-ethylhexyl) phthalate (DEHP)) in the five representative sewage treatment plants of Chaohu catchment were investigated by season in this study. Our results showed that five PAEs were ubiquitous contaminants in the five sewage treatment plants. Thereinto, the contents of DiBP were significantly higher than that of the other four kinds of PAEs, and the total concentrations of PAEs in the influents in summer (17.51–33.93 μg L−1) were significantly higher than those in winter (10.14–24.08 μg L−1). Different PAEs showed different removal efficiencies in sewage treatment plants, and the orders of individual removal rates was as follows: DMP > DEP > DBP > DiBP > DEHP. The total concentration of PAEs in the effluent was relatively low in Chaohu catchment. The biochemical treatment section of the sewage treatment plant contributed the most to the removal of total PAEs, while the pretreatment and advanced treatment sections contributed less. In addition, environmental temperature had an obvious effect on the biochemical treatment process. Appropriate combined treatment processes could efficiently improve the removal effect of PAEs in sewage treatment plants.

Cumulative effects and metabolic characteristics of aromatic compounds in microbial cells during the biochemical treatment process of coal chemical wastewater

This study aimed to investigate the effectiveness of a biochemical treatment system for coal chemical wastewater (CCW) in degrading aromatic compounds. The study examined the degradation sequence of different compounds, including benzene series (BTEX), phenols, polycyclic aromatic hydrocarbons (PAHs), and nitrogen heterocyclic compounds (NHCs), in the system. The study also analyzed the metabolic characteristics of accumulated aromatic organic compounds in the cells of microorganisms. The results showed that the aromatic compounds were first adsorbed from water by extracellular polymers (EPS) before entering the cells. The removal rates of COD and TOC in CCW reached 95% after system operation for 8 h. BTEX and NHCs were completely degraded outside the cells within 2 h, whereas PAHs and some phenols accumulated inside the cells. The metabolic characteristics of the accumulated compounds were analyzed and found to be gradually degraded through the action of catechol dioxygenase. The study findings not only demonstrate the potential for achieving efficient biodegradation of aromatic compounds in CCW but also provide the essential theoretical underpinning for the regulation and environmentally benign treatment of such wastewater within a biochemical treatment system.

Automated machine learning-based models for predicting and evaluating antibiotic removal in constructed wetlands

Machine learning models can improve antibiotic removal performance in constructed wetlands (CWs) by optimizing the operation process. However, robust modeling approaches for revealing the complex biochemical treatment process of antibiotics in CWs are still lacking. In this study, two automated machine learning (AutoML) models achieved good performance with different sizes of the training dataset (mean absolute error = 9.94–13.68, coefficient of determination = 0.780–0.877), demonstrating the ability to predict antibiotic removal performance without human intervention. Explainable analysis results (the variable importance and Shapley additive explanations) revealed that the variable substrate type was more influential than the variables of influent wastewater quality and plant type. This study proposed a potential approach to comprehensively understanding the complex effects of key operational variables on antibiotic removal, which serve as a reference for optimizing operational adjustments in the CW process.

Microbial metabolism regulation on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale

At present, the common problems of biochemical treatment systems of coal chemical wastewater were the poor system stability and the difficulty in reaching COD discharge standards. Aromatic compounds were the main contributors to COD value. The effective removal of aromatic compounds was an urgent problem in the biochemical treatment systems of coal chemical wastewater. In this study, the dominant microbial strains that could degrade phenol, quinoline, and phenanthrene were isolated respectively and inoculated into the pilot scale biochemical tank of coal chemical wastewater. The regulation effect and mechanism of microbial metabolism on the efficient degradation of aromatic compounds were studied. The results indicated that the various aromatic compounds were significantly removed under the regulation of microbial metabolism, the removal efficiencies of COD, TOC, phenols, benzenes, N-CHs, and PAHs were increased by about 25%, 20%, 33%, 25%, 42%, and 45%, respectively, and their biotoxicity was also drastically reduced. Moreover, the abundance and diversity of microbial community, and the microbial activity were obviously improved, as well as the various functional strains were selectively enriched, suggesting that the regulation system could resist environmental stresses with high substrate concentration and toxicity, which could lead to more enhanced performance for aromatic compounds removal. In addition, the microbial EPS content was significantly increased, implying the formation of microbial hydrophobic cell surfaces, which could improve the bioavailability of aromatic compounds. Furthermore, the enzymatic activity analysis revealed that the relative abundance and activity of key enzymes were all obviously improved. In conclusion, multiple lines of evidence were provided to clarify the regulation mechanism of microbial metabolism on the efficient degradation of aromatic compounds for biochemical treatment process of coal chemical wastewater in pilot scale. The results laid a good foundation for realizing the harmless treatment of coal chemical wastewater.

Stabilization and strengthening of chromium(VI)-contaminated soil via magnesium ascorbyl phosphate (MAP) and phytase addition

Cr(VI) contamination of soil threatens the environment and reduces soil strength. Therefore, both Cr(VI) stabilization and soil reinforcement should be considered in site remediation for future construction. This study investigated a biochemical treatment process using magnesium ascorbyl phosphate (MAP) and phytase. MAP was hydrolyzed via phytase catalysis to produce ascorbic acid (AA) and MgHPO4·3H2O precipitation. The AA reduced Cr(VI) into low-toxic Cr(III), which precipitated as Cr(OH)3 and CrPO4. More than 90% of the 500 mg/kg Cr(VI) in soil was reduced by 5% MAP (wt% of soil) and 1% phytase (vol/vol of soil water) doses at the geotechnically optimal soil moisture content of 16.8%. The MgHPO4·3H2O precipitates filled soil pores and enhanced the unconfined compression strength of treated soil by more than two times. This research reports a novel and practical enzymatically induced phosphate precipitation process for the remediation of Cr(VI)-contaminated soil.

Revealing the effects of acute exposure of polystyrene nanoplastics on the performance of Anammox granular sludge

The widespread use of plastic products has led to large amounts of micro/nano plastics in sludge, affecting the performance of biochemical treatment processes. Anammox is a cost-effective biological nitrogen removal process. However, the effect of micro/nano plastic exposure on the nitrogen removal performance and structural stability of Anammox sludge is unclear. In this study, the ability of Anammox granular sludge (AnGS) to cope with nanoplastic exposure was investigated by an acute exposure test, and the related mechanism was revealed. The effect of acute exposure to nanoplastics on the performance of AnGS showed a dose effect. The SAANH4+-N and SAANO2-N decreased by 26.1% and 19.3%, and structural stability reduced 42.9% after acute exposure with 0.5 mg/mL polystyrene nanoplastics (PS-NPs). The elevated oxidative stress increased the dead bacteria, decreasing the nitrogen removal performance of the sludge. The decrease in the structural stability of AnGS was attributed to the decrease in zeta potential and sludge hydrophobicity. The structural research provides a theoretical basis for assessing the effect on the Anammox process.

Biodegradation time series characteristics and metabolic fate of different aromatic compounds in the biochemical treatment process of coal chemical wastewater

In this study, the biochemical treatment system of coal chemical wastewater (CCW) was constructed to degrade aromatic compounds. The biodegradation time series characteristics of 8 benzene series (BTEX), 6 phenols, 10 polycyclic aromatic hydrocarbons (PAHs), and 3 nitrogen heterocyclic compounds (NHCs) were detected. The aim was to clarify the storage characteristics and dynamic transformation in water, EPS, and cells of these aromatic compounds. The results showed that BTEX and NHCs were more easily degraded than PAHs and phenols. Furthermore, aromatic compounds were initially adsorbed into EPS from water by microorganisms. Then, some were degraded, and others were transferred into the cell. Finally, they were completely degraded. The percentage of surplus content with them in EPS and cells were PAHs > phenols > NHCs = BTEX. The study could lay a theoretical foundation for the regulation and harmless treatment of the CCW in the stable operation of the biochemical treatment system.

An Intelligent Optimization-Based Particle Filter for Fault Diagnosis

It is very important to implement the fault diagnosis technology in industrial processes to make the process more reliable. In this paper, an improved particle filter (PF) method based on a modified beetle swarm antennae search (BSAS) algorithm is proposed and verified in a doubly fed induction generator (DFIG) fault diagnosis application. Firstly, the search strategy of BSAS is improved to ensure its global search ability. Secondly, it is introduced to the traditional PF algorithm to improve the particle diversity and impoverishment drawbacks. Finally, the fault diagnosis algorithm is verified by combining the DFIG state space model. The simulation experimental of fault detection and isolation results show that the proposed method is simple and effective, and it can effectively monitor the occurrence of faults. For the fault diagnostic application, the method proposed in this paper could be implemented in other model based processes, including chemical process, biochemical wastewater treatment process, etc.

The Strategy of Hospital Wastewater Treatment to Reduce the Risk of Virus Transmission and Environmental Pollution under COVID-19 based on Big Data

The novel coronavirus (COVID-19) is sweeping the world starting in 2019. According to the analysis based on big data technology, the wastewater generated by hospitals hosting SARS-CoV-2 infected patients is complex in origin and composition, and contains a large number of pathogenic microorganisms and drugs, etc. Without effective treatment, it will become an important pathway for the spread of the epidemic and a source of environmental pollution, so wastewater treatment processes more effective for degrading organic matter and inactivating viruses are required. This paper investigates the improvement measures adopted for hospital wastewater treatment systems in response to COVID-19. For instance, reinforced septic tanks and fine grilles with smaller grids were used for wastewater treatment. Besides, the Moving-bed Biofilm Reactor (MBBR) process and the flocculation slant plate process were widely used for biochemical treatment and sedimentation processes. It is critical to increase the dosage of disinfectant since coronaviruses can be transmitted through water bodies and pose a threat to the environment and human health. Finally, a high-temperature anaerobic digestion and incineration disposal scheme can effectively inactivate sludge pathogenic bacteria and viruses for sludge generated from hospital wastewater treatment. In addition, we propose recommendations for the shortcomings and risks in this treatment system, which are important for improving the efficiency of medical wastewater containing the SARS-CoV-2 virus and stopping further virus transmission.

Minimization of greenhouse gas emissions from extended aeration activated sludge process

AbstractOne of the greenhouse gas (GHG) emission resources is industrial wastewater treatment plants. In this study, on-site and off-site greenhouse gas emissions of an extended aeration activated sludge process in a meat processing wastewater treatment plant were estimated using a new developed approach based on the IPCC method. On-site emissions were regarded as the emissions related to the biochemical treatment process and microbial activity in the wastewater. On-site emissions were estimated from organic materials removal from wastewater and microbial mass activity. Biological oxygen demand (BOD) and chemical oxygen demand (COD) removal were considered as pollutant resources of carbon dioxide (CO2) and methane (CH4), respectively. Off-site emission was estimated from electricity consumption, chemical use and the sludge stabilization process. This paper aimed to determine and reduce on-site and off-site emissions for the extended aeration process in an industrial wastewater treatment plant. Modification of operating conditions was applied to reduce GHG emissions. The results revealed that electricity consumption was the major source of the greenhouse gas emissions for this process with a value of 6,002.77 kg CO2e/d. The minimization of total GHG emissions reached up to 17.1% by modifying the treatment process conditions.

Research on the Impact and Mechanism for the Inhibition of Micrococcus Catalase Activity by Typical Tetracyclines.

As potential inhibitors target to biological enzymes, antibiotics may have certain impacts on the biochemical treatment process. With micrococcus catalase (CAT) served as the target molecule, the impact and inhibition mechanism for typical tetracyclines (TCs) were evaluated. Toxicity experiments showed that TCs had significant inhibition on CAT in the sequence of tetracycline>chlortetracycline>oxytetracycline>doxycycline. To clarify the inhibition mechanism between TCs and CAT which was explored with the assistance of fluorescence spectroscopy and MOE molecule simulation. According to fluorescence analysis, TCs quenched the fluorescence signal of CAT by the mode of static quenching. Combined with toxicity data, it could be presumed that TCs combined with the catalytic active center and thus inhibited CAT. Above presumption was further verified by the molecular simulation data. When TCs combined with the catalytic center of CAT, the compounds have increased combination areas and prominent energy change (compared with the compounds formed by TCs and noncatalytic center recommend by MOE software). IBM SPSS statistics showed that TC toxicity positively correlated with the hydrogen bonds such as O13→Glu252, O1←Arg195, and O6→Asp249, but negatively correlated with the hydrogen bonds such as O10→Pro363, O10→Lys455, and O12 → Asn127. TC toxicity also positively correlated with the ion bonds ofN4-Glu252, but negatively correlated with the ion bonds of N4-Asp379. Hydrogen bonds and ion bonds for above key sites were closely related to the inhibition effect of TCs on CAT.

Wastewater Treatment Plant: Modelling and Validation of an Activated Sludge Process

The aim of the present paper is to develop a reliable and accurate model of the wastewater biochemical treatment process and to explore the behaviour through a general dynamic simulation environment, namely the INtegrated Simulation Environment Language (INSEL), for the analysis of the energy demand of the whole wastewater treatment plant. In particular, the presented model pays special attention to the chemical kinetics involved in the activated sludge process for the reduction of nitrogen and carbon compounds. According to the best practices, the plant configuration considered in this work includes the denitrification-nitrification process, performed by completely mixed reactors. In particular, the process analysed in this paper is based on the Ludzak-Ettinger process. The biological process is simulated according to the well-known method widely used in the literature, namely the Activated Sludge Model No 1 (ASM1). The model includes a set of equations for the calculation of aerobic growth of heterotrophs, anoxic growth of heterotrophs, aerobic growth of autotrophs, decay of autotrophs, ammonification of soluble nitrogen, hydrolysis of entrapped organics, and hydrolysis of entrapped organic nitrogen. All these equations, along with energy and mass balances, are solved by the explicit Euler method. The developed model is validated using literature data, showing a great accuracy (deviation below 1%). As for the temperature, results show that, between 15 and 25 °C, in the initial part of the process, transport effects dominate the consumption ones. When the temperature is higher than 30 °C, nitrate consumption is so fast that biomass growth is limited by this effect. Conversely, in case of low temperatures (5–10 °C), biomass growth is not limited by nitrate availability. Finally, results also showed that temperature significantly affects the denitrification process, whereas the effect on the oxygen is lower.

Reduksi Energi Pengolahan Air Limbah di Kawasan Industri Dengan Implementasi Teknologi Food Chain Reactor (Studi Kasus : Kawasan Industri Jababeka Bekasi)

Biological-aerobic process is a technology that is often chosen to treat wastewater in industrial areas, especially industries related to food industries. Compared to chemical treatment and advanced treatment, biological treatment is relatively more efficient in the costs required. However, in conventional biological treatment the amount of energy consumption in the process is a major cost component that it becomes one of the challenges in implementing this technology. This paper contains a review of the implementation of the Food Chain Reactor (FCR) technology in treating industrial area wastewater, focusing on an overview of energy consumption compared to conventional biological-aerobic treatment of oxidation ditch (OD). FCR is a wastewater treatment plant (IPAL) that combines Integrated Fixed Film Activated Sludge (IFAS) technology and technology that resembles Constructed Wetland, thus enabling the simultaneous physical, biological and biochemical treatment processes within the reactor. In this case study, the implementation succeeded in showing a reduction in energy consumption by 46.4% while maintaining an efficiency decrease in BOD by 83% and efficiency in decreasing ammonia by 82%. As with the OD process, in this FCR study showed that the denitrification process has not been successful.

Deep Dehalogenation of Florfenicol Using Crystalline CoP Nanosheet Arrays on a Ti Plate via Direct Cathodic Reduction and Atomic H.

Efficient elimination of antibacterial activity of halogenated antibiotics by dehalogenation pretreatment is desired for a biochemical treatment process. In this study, crystalline cobalt phosphide nanosheet arrays on a Ti plate (C-CoP/Ti) are fabricated by a simple electrodeposition and phosphorization process. The crystalline structure greatly promotes atomic hydrogen (H*) generation. Moreover, the nanosheet arrays can provide abundant active sites and accelerate electron transfer and mass transport. As a result, the dehalogenation rate of florfenicol (FLO, an emerging organic pollutant) on C-CoP/Ti is 11.1, 2.97, and 13.6 times higher than that on amorphous CoP/Ti, Pd/Ti, and bare Ti, respectively. The C-CoP/Ti electrode achieves 97.4% dehalogenation of FLO (20 mg L-1) within 30 min at -1.2 V (vs Ag/AgCl). Nearly 100% of Cl and 20% of F are broken away within 120 min, showing the highest electrocatalytic defluorination efficiency reported so far. Both experimental results and theoretical calculations reveal that the dehalogenation of FLO on C-CoP/Ti is synergistically accomplished via direct reduction of electron transfer and indirect reduction of H*. This study develops a highly efficient non-noble metal electrode material for dehalogenation of halogenated organic compounds.

Biotoxicity assessment and toxicity mechanism on coal gasification wastewater (CGW): A comparative analysis of effluent from different treatment processes

Even though coal gasification wastewater (CGW) treated by various biochemical treatment processes generally met the national discharge standard, its potential biotoxicity was still unknown. Therefore, in this study, bioassay with Tetrahymena thermophila (T. thermophila) was conducted to comprehensively evaluate the variation of biotoxicity in raw CGW and the treated effluent from lab-scale micro-electrolysis integrated with biological reactor (MEBR), single iron-carbon micro-electrolysis (ICME) and conventional activated sludge (CAS) processes. The results illustrated that raw CGW presented intensive acute toxicity with 24 h EC50 value of 8.401% and toxic unit (TU) value of 11.90. Moreover, it performed significant cell membrane destruction and DNA damage even at 10% dilution concentration. The toxicant identification results revealed that multiple toxic polar compounds such as phenolic, heterocyclic and polycyclic aromatic compounds were the main contributors for biotoxicity. Furthermore, these compounds could accelerate oxidative stress, thereby inducing oxidative damage of cell membrane and DNA. As for treated effluent, TU value was decreased by 90.58% in MEBR process. An effective biotoxicity reduction was achieved in MEBR process owing to high removal efficiency in polar organic toxicants. In contrast, effluent from ICME and CAS processes presented relatively high acute toxicity and genotoxicity, because various heterocyclic and polycyclic aromatic compounds were difficult to be degraded in these processes. Therefore, it was suggested that MEBR was a potential and feasible process for improving CGW treatment and minimizing ecological risk.

Discussion on Wastewater Treatment Process of Coal Chemical Industry

Coal chemical wastewater has such characteristics as high concentration of oil, ammonia nitrogen and COD. In this paper, treatment process of coal chemical industry is described mainly, such as pretreatment process, biochemical treatment process and polishing process. Through the recovery of phenol and ammonia and the treatment of wastewater from abroad, the new technology of wastewater treatment in coal chemical industry was expounded. Finally, The development of coal chemical wastewater treatment technology is prospected, and the pretreatment technology is emphasized. According to the diversification and utilization of water, zero discharge of coal chemical wastewater will be fulfilled.