Biofilm Reactor Research Articles

Enhanced microplastics removal from sewage effluents via CTAB-modified magnetic biochar: Efficacy and environmental impact

Sewage treatment plants (STPs) are identified as a significant pathway of microplastics (MPs) re-entry into the environment through effluent discharge, thereby emphasizing the need for reliable and efficient treatment methods. This study investigated MPs removal from sewage effluents using cetyl trimethyl ammonium bromide (CTAB)-modified magnetic biochar (RH-MBC-CTAB) as an adsorbent. Biochars from different biomass were synthesized, surface modified, characterized, and compared for their MPs removal efficacy from aqueous matrices. Batch adsorption studies were initially conducted on synthetic water with 1 μm sized polystyrene (PS) MPs using different MP concentrations (1–10 mg/L) and varying adsorbent dosages (1–10 mg/50 mL) to assess the effect of different process parameters, viz. pH (2–10), humic acid (6–25 mg/L), and competitive ions (0.01–0.2 M). The maximum MPs removal (98%) was achieved at the favorable conditions: initial MPs concentration: 10 mg/L, RH-MBC-CTAB dose: 7 mg/50 mL, pH 4, mixing speed: 180 rpm, and contact time: 3 min. Electrostatic attraction and hydrogen bonding were likely to remove MPs while the MPs adsorption was best fitted by the pseudo-second-order kinetics model (R2 = 0.91) and Langmuir isotherm model (R2 = 0.94) with the maximum adsorption capacity of 247.52 mg/g. Further, the application of RH-MBC-CTAB on the real-time sewage effluents from sequencing batch reactor (SBR) and moving bed biofilm reactor (MBBR)-based STPs spiked with MPs showed up to 96% MPs removal. The reusability results revealed that developed RH-MBC-CTAB could maintain good stability for up to three reusability cycles, therefore offering extensive potential for the removal of MPs from sewage effluents.

Evaluation of a pilot-scale anaerobic biofilm reactor for the treatment of slaughterhouse effluents in rural areas

ABSTRACT Rural slaughterhouses often lack strict effluent treatment rules, resulting in inadequate treatment prior to release into water bodies. Slaughterhouse wastewater (SWW) is a high-strength effluent, posing risks of contamination to ecosystems and human health. To tackle the need for suitable technologies in these areas, this study evaluated a 215 L pilot-scale fixed-bed biofilm reactor (FBBR), known for its simplicity in implementation, operation, and maintenance. During the operation, an initial startup period, with the liquid fraction of fruit and vegetable waste (LF-FVW) was conducted, followed by a gradual transition to SWW, creating a co-digestion period during the substrate transition. Organic load variations (1.59, 3.35, and 4.00 kgCOD/m3·d), corresponding to flow rates of 50, 75, and 120 L/d, respectively, were implemented to address potential alterations in effluent concentration and composition in authentic rural settings. Removal rates of up to 83.69, 91.81, 87.00, and 92.00% were achieved for COD, sCOD, TS, and VS, respectively, with an average removal of 32.00% for TN, and biogas production exceeded 300 L/h at 4.00 kgCOD/m3·d. These results suggest that FBBR implementation in rural areas effectively confronts SWW treatment challenges by reducing contamination, generating biogas, and adapting to rural conditions.

In vitro Tolerance of Staphylococcus haemolyticus and Candida albicans Biofilms to Dalbavancin and Anidulafungin

Background: Concerns about infections resulting from bacterial biofilm formation in invasive devices such as catheters and prostheses are becoming widespread in the public health domain. Staphylococcus haemolyticus, a coagulase-negative bacterium, and Candida albicans, a yeast, have become recurrent pathogens of these diseases because their presence in these devices enhances the likelihood of infection. It is believed that these microorganisms produce biofilms, which complicate treatment and slow the patient´s recuperation. Dalba-vancin is a semisynthetic, lipoglycopeptide-class antibiotic utilized as an anti-infective agent to break down gram-positive bacteria biofilms. Anidulafungin is an echinocandin class anti-fungal medication that works very well against resistant yeast strains and removes biofilms. Objective: This study aims to examine the anti-infective agents´ tolerance to the biofilms of Staphylococcus haemolyticus and Candida albicans. Methods: Polymicrobial biofilms were grown in a CDC Biofilm Reactor (CBR) for use in in vitro experiments. Results: When dalbavancin maintained its antibiotic activities against Staphylococcus hae-molyticus in comparison with their activity against the sessile forms, the antifungal anidula-fungin lost efficacy in eliminating Candida albicans. Conclusion: The planktonic forms of microbes are examined in relation to the tolerance to these anti-infective drugs.

Carbon chain elongation characterizations of electrode-biofilm microbes in electro-fermentation

The higher efficiency of electro-fermentation in synthesizing medium-chain fatty acids (MCFAs) compared to traditional fermentation has been acknowledged. However, the functional mechanisms of electrode-biofilm enhancing MCFAs synthesis remain research gaps. To address this, this study proposed a continuous flow electrode-biofilm reactor for chain elongation (CE). After 225 days of operation, stable electrode-biofilms formed and notably improved caproate yield by more than 38 %. The electrode-biofilm was enriched with more CE microorganisms and electroactive bacteria compared to the suspended sludge microorganisms, including Caproicibacterium, Oscillibacter and Pseudoramibacter. Besides, the upregulated CE pathways were evaluated by metagenomic analysis, and the results indicated that the pathways such as acetyl-CoA and malonyl-[acp] formation, reverse beta-oxidation, and fatty acid biosynthesis pathway were all markedly enhanced in cathodic biofilm, more than anodic biofilm and suspended microorganisms. Moreover, microbial community regulated processes like bacterial chemotaxis, flagellar assembly and quorum sensing, crucial for electrode-biofilm formation. Electron transfer, energy metabolism, and microbial interactions were found to be prominently upregulated in the cathodic biofilm, surpassing levels observed in anodic biofilm and suspended sludge microorganisms, which further enhanced CE efficiency. In addition, the statistical analyses further highlighted key microbial functions and interactions within the cathodic biofilm. Oscillospiraceae_bacterium was identified to be the most active microbe, alongside pivotal roles played by Caproiciproducens_sp._NJN-50, Clostridiales_bacterium, Prevotella_sp. and Pseudoclavibacter_caeni. Eventually, the proposed microbial collaboration mechanisms of cathodic biofilm were ascertained. Overall, this study uncovered the biological effects of the electrode-biofilm on MCFAs electrosynthesis, thereby advancing biochemicals production and filling the knowledge gaps in CE electroactive biofilm reactors.

Two-stage partial nitrification-denitrification and anammox process for nitrogen removal in vacuum collected toilet wastewater at ambient temperature

Vacuum collected toilet wastewater (VCTW) contains high and fluctuating contents of organics and nitrogen, which exerts technological challenges to biological treatment processes. A partial nitrification–denitrification and anammox (PND-AMX) process was developed in sequencing batch reactor (SBR) and moving bed biofilm reactor (MBBR) to achieve effective nitrogen removal in VCTW at low ambient temperature. Stable PND was achieved, and nitrogen removal efficiency in SBR could be manipulated by adjusting influent COD/N ratios. As temperature ≥18 °C, 91.0% nitrogen was removed in PND-AMX process. In spite of the decreased anammox activity at 13–18 °C, more than 90% nitrogen removal could be obtained by adjusting SBR influent COD/N to 2.43 ± 0.32 with methanol. In MBBR reactor, Candidatus Kuenenia was the dominant anammox bacteria and contributed to more than 90% nitrogen removal capacity. Co-existing anammox and denitrifying bacteria synergistically contributed to the removal of ammonium, nitrite, nitrate, and COD in MBBR.

The Valorization of Fruit and Vegetable Wastes Using an Anaerobic Fixed Biofilm Reactor: A Case of Discarded Tomatoes from a Traditional Market

Tomato waste, characterized by high organic matter and moisture content, offers a promising substrate for anaerobic digestion, though rapid acidification can inhibit methanogenic activity. This study investigated the performance of a 10.25 L anaerobic fixed biofilm reactor for biogas production using liquid tomato waste, processed through grinding and filtration, at high organic loading rates, without external pH control or co-digestion. Four scouring pads were vertically installed as a fixed bed within a fiberglass structure. Reactor performance and buffering capacity were assessed over three stages with progressively increasing organic loading rates (3.2, 4.35, and 6.26 gCOD/L·d). Methane yields of 0.419 LCH4/gCOD and 0.563 LCH4/g VS were achieved during the kinetic study following stabilization. Biogas production rates reached 1586 mL/h, 1804 mL/h, and 4117 mL/h across the three stages, with methane contents of 69%, 65%, and 72.3%, respectively. Partial alkalinity fluctuated, starting above 1500 mg CaCO3/L in Stage 1, dropping below 500 mg CaCO3/L in Stage 2, and surpassing 3000 mg CaCO3/L in Stage 3. Despite periods of forced acidification, the system demonstrated significant resilience and high buffering capacity, maintaining stability through hydraulic retention time adjustments without the need for external pH regulation. The key stability indicators identified include partial alkalinity, effluent chemical oxygen demand, pH, and one-day cumulative biogas. This study highlights the effectiveness of anaerobic fixed biofilm reactors in treating tomato waste and similar fruit and vegetable residues for sustainable biogas production.

Treatment of Anaerobic Digester Liquids via Membrane Biofilm Reactors: Simultaneous Aerobic Methanotrophy and Nitrogen Removal.

Anaerobic digestion (AD) produces useful biogas and waste streams with high levels of dissolved methane (CH4) and ammonium (NH4+), among other nutrients. Membrane biofilm reactors (MBfRs), which support dissolved methane oxidation in the same reactor as simultaneous nitrification and denitrification (ME-SND), are a potential bubble-less treatment method. Here, we demonstrate ME-SND taking place in single-stage, AD digestate liquid-fed MBfRs, where oxygen (O2) and supplemental CH4 were delivered via pressurized membranes. The effects of two O2 pressures, leading to different O2 fluxes, on CH4 and N removal were examined. MBfRs achieved up to 98% and 67% CH4 and N removal efficiencies, respectively. The maximum N removal rates ranged from 57 to 94 mg N L-1 d-1, with higher overall rates observed in reactors with lower O2 pressures. The higher-O2-flux condition showed NO2- as a partial nitrification endpoint, with a lower total N removal rate due to low N2 gas production compared to lower-O2-pressure reactors, which favored complete nitrification and denitrification. Membrane biofilm 16S rRNA amplicon sequencing showed an abundance of aerobic methanotrophs (especially Methylobacter, Methylomonas, and Methylotenera) and enrichment of nitrifiers (especially Nitrosomonas and Nitrospira) and anammox bacteria (especially Ca. Annamoxoglobus and Ca. Brocadia) in high-O2 and low-O2 reactors, respectively. Supplementation of the influent with nitrite supported evidence that anammox bacteria in the low-O2 condition were nitrite-limited. This work highlights coupling of aerobic methanotrophy and nitrogen removal in AD digestate-fed reactors, demonstrating the potential application of ME-SND in MBfRs for the treatment of AD's residual liquids and wastewater. Sensor-based tuning of membrane O2 pressure holds promise for the optimization of bubble-less treatment of excess CH4 and NH4+ in wastewater.

To Analysis the Necessity of Advance Sewage Treatment Plant (STP) Waste Management In Primary Health Care Centers (A Review)

The effluent from medical facilities poses a serious risk to human health because of how vulnerable people are to certain diseases. Additionally, the COVID-19 pandemic has called for a global awareness of the need to monitor infections and other resistant organisms in hospital wastewater and remove them. Apart from that, the presence of various resistant organics, pharmaceutically active compounds (PhACs), etc., creates a complicated pollution stack that affects biological systems and water resources. This survey has provided information on the occurrence, persistence, and removal of drug-resistant microbes, infectious diseases, and other micropollutants. The implementation of several pilot/full-scale measures has been evaluated with respect to the removal of pathogens, PhACs, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), etc. Many organic forms, including constructed wetlands, actuated slime handles, and film bioreactors, were discovered to provide more than 80% evacuation of BOD, COD, TSS, etc. Nevertheless, some stubborn natural toxins are not as amenable to such treatments and necessitate the use of tertiary drugs such adsorption, UV treatment, ozone treatment, and so forth. Following the treatment of clinic wastewater, antibiotic-resistant bacteria and illnesses were discovered to be very persistent, necessitating high dosages of chlorination or UV therapy to render them inactive. This project involves the Govthospital exectting STP supplanted by modern innovation STP.

Pre-anoxic electro-stimulation enhanced simultaneous nitrification–denitrification in single-stage electrolysis-integrated sequencing batch biofilm reactor

Simultaneous nitrification–denitrification (SND) is a promising nitrogen removal process. However, total nitrogen (TN) removal is limited due to unsatisfactory denitrification. This study demonstrated that short-time (1 h) pre-anoxic electro-stimulation significantly enhanced SND efficiency in the aerobic phase by promoting the proliferation of mixotrophic and heterotrophic denitrifiers. SND and TN removal efficiencies at the optimal electric current (EC) (0.02 A) were 85.6 % and 93.9 %, which were 39.1 % and 17.2 % higher than control. Microbial community analysis indicated that the abundance of mixotrophic and heterotrophic denitrifiers significantly increased. H2 generated in the electro-stimulation process induced the proliferation of mixotrophic denitrifiers. The weak EC (0.02 A) promoted the activity and growth of heterotrophic denitrifiers by accelerating electron transfer. They concurrently mediated heterotrophic denitrification to enhance SND efficiency. PICRUSt2 analysis revealed that the abundance of denitrifying genes dramatically surged. This study provides new insights into applying electrolysis to achieve advanced SND while minimizing electricity consumption.

Simultaneous removal of ammonia nitrogen, sulfamethoxazole, and antibiotic resistance genes in self-corrosion microelectrolysis-enhanced counter-diffusion biofilm system

A self-corrosion microelectrolysis (SME)-enhanced membrane-aerated biofilm reactor (eMABR) was developed for the removal of pollutants and reduction of antibiotic resistance genes (ARGs). Fe2+ and Fe3+ formed iron oxides on the biofilm, which enhanced the adsorption and redox process. SME can induce microorganisms to secrete more extracellular proteins and up-regulate the expression of ammonia monooxygenase (AMO) (0.92 log2). AMO exposed extra binding sites (ASP-69) for antibiotics, weakening the competition between NH4+-N and sulfamethoxazole (SMX). The NH4+-N removal efficiency in the S-eMABR (adding SMX and IC) increased by 44.87 % compared to the S-MABR (adding SMX). SME increased the removal performance of SMX by approximately 1.45 times, down-regulated the expressions of sul1 (−1.69 log2) and sul2 (−1.30 log2) genes, and controlled their transfer within the genus. This study provides a novel strategy for synergistic reduction of antibiotics and ARGs, and elucidates the corresponding mechanism based on metatranscriptomic and molecular docking analyses.

Effects of gradual increase of ciprofloxacin and cefotaxime on nitrogen and phosphorus removal and microbial community in moving bed biofilm reactor

To clarify the effects of trace amount of antibiotics in wastewater on biofilm reactor, this study explored the effects of gradual increase of ciprofloxacin (CIP) and cefotaxime (CTX) ranging from 100 to 1000 ng·L−1 on the nitrogen and phosphorus removal and microbial community in a moving bed biofilm reactor (MBBR). Under different phases of CIP and CTX gradual increase, the resilience of culturable functional bacteria including ammonifying bacteria, nitrite oxidizing bacteria, aerobic denitrifying bacteria and phosphorus accumulating organisms in the biofilm was analyzed. High-throughput sequencing analysis was used to reveal the microbial community structure and species composition of functional bacteria. The results indicated that the treatment performance of MBBR was temporarily affected by trace CIP and CTX and returned to its original level within 1–2 days. Ammonifying bacteria exhibited strong resilience in trace CIP and CTX stress environments. Trace CIP and CTX altered the microbial community structure in biofilm, but the performance of nitrogen and phosphorus removal in MBBR was slightly affected. This might attribute to the rapid proliferation of Thauera, Dechloromonas and Candidatus_Accumulibacter on the carrier biofilm. The research results help to deepen the understanding of the impact of trace antibiotics on the MBBR and to provide a reference for the development of microbial germplasm resources for biological nitrogen and phosphorus removal from wastewater under antibiotic stress conditions.

A biologically driven model for rural wastewater management: feasibility and efficiency of algal-bacterial biofilm reactors for combined treatment and algae farming

A biologically driven model for rural wastewater management: feasibility and efficiency of algal-bacterial biofilm reactors for combined treatment and algae farming

Integration of batch assays and microbial community analysis for partial nitritation and anammox process monitoring

This study investigates the feasibility of using batch assays combined with microbial community analysis to control the partial nitritation/anammox (PN/A) process. A Moving Bed Sequencing Batch Biofilm Reactor (MBSBBR) was operated over 130 days with varying ammonia influent concentrations. The highest anammox activity (22.4 mg N/gVSS∙h) was observed at an influent concentration of 200 mg N-NH4/L, correlating with high total inorganic nitrogen (TIN) removal efficiency. However, increasing the ammonia influent concentration to 340 mg N/L led to decreased anammox and nitrifying bacteria activities and reduced TIN removal efficiency. Sequencing revealed Candidatus Brocadia as the predominant genus, with its abundance correlating with TIN removal performance. High correlation coefficients (above 0.76) among batch tests highlighted the interdependence of key bacterial activities in the PN/A, emphasizing the need for a balanced microbial community for effective nitrogen removal. Batch assays provided immediate data on metabolic activities, while sequencing offered comprehensive insights into microbial community structure. Integrating these methods allowed for a holistic understanding of the microbial dynamics and their impact on process stability. This approach enhances the accuracy of wastewater treatment monitoring, aiding in the development of effective management strategies for optimizing PN/A processes.

Hybrid modelling of nitrogen removal by biofiltration using high-frequent operational data

ABSTRACT In this research, a parallel hybrid model is presented for the simulation of nitrogen removal by submerged biofiltration of a very large-size wastewater treatment plant. This hybrid model consists of a machine learning model and a mechanistic model that are combined to produce accurate predictions of water quality variables. The models are calibrated/validated using detailed and quality-controlled operational data collected over a period of 3.5 months in 2020. The mechanistic model applied is a modified activated sludge model that describes the biological, physical and chemical processes taking place in a biofilm reactor based on the domain knowledge of these processes. A three-layer feed-forward artificial neural network with a rectified linear activation function that aims to reduce the mechanistic model's residual error and then correct its output. The results show how the hybrid model outperforms and significantly reduces the size of the mechanistic model's prediction errors of the effluent nitrate concentration from a relative mean error of 12% for the mechanistic model to 2% for the hybrid model during training. The error on nitrate simulations increases to 8% during hybrid model testing, still significantly lower than the error of the mechanistic model. These results support future operational applications of hybrid biofilm models.

Formation mechanism of high biofilm phosphorus storage capacity and its effect on phosphorus uptake-release and carbon source consumption

Phosphorus recovery from wastewater is an effective method to alleviate the shortage of phosphorus resources. The biofilm phosphorus recovery process can realize simultaneous removal and enrichment of phosphorus in wastewater. In this study, a sequencing batch biofilm reactor was constructed to study the rapid phosphorus release and slow phosphorus release stages in the phosphorus recovery cycle. The relationship between high biofilm phosphorus storage capacity (Pbiofilm), phosphorus recovery solution concentration, phosphorus uptake-release behavior and carbon source consumption were explored. The increase in phosphorus recovery solution concentration promotes the elevation of Pbiofilm, which, conversely promotes phosphorus release in the next recovery cycle. In addition, the distinct phosphorus uptake-release characteristics of extracellular polymeric substances and cells were illustrated. This study provides a theoretical foundation to elevate the phosphorus recovery efficiency and reduce carbon source consumption in biofilm phosphorus recovery process.

How does CO2 supply shape the biofilm microenvironment in denitrifying H2-based membrane biofilm reactor: A modeling study

CO2 supply to a hydrogen-based membrane biofilm reactor (H2-based MBfR) is an imperative approach for maintaining its performance. The supply modes (via bulk liquid or membrane) and dosages of CO2 can largely determine the efficiency of H2-based MBfR, but their effects on the biofilm microenvironment remain unclear. To bridge this knowledge gap, a denitrifying H2-based MBfR equipped with an in-situ pH microsensor was constructed, and an expanded model was developed by incorporating the modified denitrification kinetic algorithm, based on the measured pH gradients in the biofilm. Results showed that the greatest NO3− removal was achieved at an influent CO2 concentration of 50 mg/L and a CO2 fraction of 20 %. The carbon source constituted a decisive factor, limiting the denitrification activity in the inner and outer layers of the biofilm when CO2 was supplied below the optimum dosage (50 mg/L or 20 %) via bulk liquid and membrane, respectively. Increasing the CO2 dosage to 100 mg/L or 30 % enabled the sufficient carbon source, but led to low-pH inhibition in the entire biofilm. The outcomes of this research provided mechanistic insights into the denitrification behaviors of H2-based MBfR, and the developed model could help devise CO2 supply strategies for the management of the reactor.

Evaluating the role of high N2O affinity complete denitrifiers and non-denitrifying N2O reducing bacteria in reducing N2O emissions in river

Freshwater rivers are hotspots of N2O greenhouse gas emissions. Dissolved organic carbon (DOC) is the dominant electron donor for microbial N2O reduction, which can reduce N2O emission through enriching high N2O affinity denitrifiers or enriching non-denitrifying N2O-reducing bacteria (N2ORB), but the primary regulatory pathway remains unclear. Here, field study indicated that high DOC concentration in rivers enhanced denitrification rate but reduced N2O flux by improving nosZ gene abundance. Then, four N2O-fed membrane aeration biofilm reactors inoculated with river sediments from river channel, estuary, adjacent lake, and a mixture were continuously performed for 360 days, including low, high, and mixed DOC stages. During enrichment stages, the (nirS+nirK)/nosZ ratio showed no significant difference, but the community structure of denitrifiers and N2ORB changed significantly (p < 0.05). In addition, N2ORB strains isolated from different enrichment stages positioned in different branches of the phylogenetic tree. N2ORB strains isolated during high DOC stage showed significant higher maximum N2O-reducing capability (Vmax: 0.6 ± 0.4 ×10−4 pmol h−1 cell−1) and N2O affinity (a0: 7.8 ± 7.7 ×10−12 L cell−1 h−1) than strains isolated during low (Vmax: 0.1 ± 0.1 ×10−4 pmol h−1 cell−1, a0: 0.7 ± 0.4 ×10−12 L cell−1 h−1) and mixed DOC stages (Vmax: 0.1 ± 0.1 ×10−4 pmol h−1 cell−1, a0: 0.9 ± 0.9 ×10−12 L cell−1 h−1) (p < 0.05). Hence, under high DOC concentration conditions, the primary factor in reducing N2O emissions in rivers is the enrichment of complete denitrifiers with high N2O affinity, rather than non-denitrifying N2ORB.

Insights into the azo dye decolourisation and denitrogenation in micro-electrolysis enhanced counter-diffusion biofilm system

In this study, electron transport pathways were activated and diversified by coupling counter-diffusion biofilms with micro-electrolysis for Alizarin yellow R (AYR) denitrogenation. Due to the binding of AYR to two residues of EC 4.1.3.36 with higher binding energy, the expression of EC 4.1.3.36 was down-regulated, causing the EC 3.1.2.28 and EC 2.5.1.74 for menaquinone synthesis (redox mediator) undetectable in Membrane aerated biofilm reactors (MABR). Spontaneous electron generation in the micro electrolysis-coupled MABR (ME-MABR) significantly activated two enzymes. Activated menaquinone up-regulated decolourisation related genes expression in ME-MABR, including azoR (2.12 log2), NQO1 (2.97 log2), wrbA (0.45 log2), and ndh (0.47 log2). The diversified electron flow pathways also promoted the nitrogen metabolism coding genes up-regulation, accelerating further inorganic nitrogen denitrogenation after AYR mineralisation. Compared to MABR, the decolourisation, mineralisation, and denitrogenation in ME-MABR increased by 25.80 %, 16.53 %, and 13.32 %, respectively. This study provides new insights into micro-electrolysis enhanced removal of AYR.

Heavy metals biosorption in unary, binary, and ternary systems onto bacteria in a moving bed biofilm reactor

Toxic and heavy metals cause direct and indirect damage to the environment and ultimately to humans. This study involved the isolation of indigenous bacteria from heavy metal-contaminated environments that have the ability to bioabsorb heavy metals such as cadmium, nickel, and lead. The bioabsorption process was optimized by varying parameters such as temperature, metal concentration, number of bacteria, pH, and more. The bacterial isolates were investigated in terms of morphology, biochemistry, and phylogeny, with 12 strains chosen in the initial stage and one strain chosen in the final stage. It should be remembered that the metal uptake capacity of all isolates was approximately calculated. A box and reactor were designed to house these optimized microorganisms. Based on biochemical, morphological, and molecular results, the isolated strain was found to be closely related to the Bacillus genus. In the first five steps of testing, the ideal pH for removing lead alone, lead with cadmium, lead with nickel, and lead ternary (with cadmium and nickel) by Bacillus bacteria was found to be 7, 6, 5.5, and 6.5, respectively. The absorption efficiencies for single lead (unary), lead together with nickel, cadmium (binary), and ternary (lead with cadmium and nickel) were found to be 0.36, 0.25, 0.22, and 0.21 mmol/g, respectively. The ideal temperature for lead removal was around 30 °C. The adsorption isotherm for each lead metal in different states was found to be similar to the Langmuir isotherm, indicating that the surface absorption process is a single-layer process. The kinetics of the process follow the second-order kinetic model. The amount of Bacillus bacteria biomass obtained during this process was approximately 1.5 g per liter.

Graywater Treatment Efficiency and Nutrient Removal Using Moving Bed Biofilm Reactor (MBBR) Systems: A Comprehensive Review

Using wastewater in response to water-related challenges from climate variation has gained significance. Various sophisticated technologies have been developed to meet the demand for wastewater treatment and reuse. Graywater, an intrinsic component of wastewater, is acknowledged for its practical potential in the context of reuse. Decentralized wastewater treatment systems, exemplified by Moving Bed Biofilm Reactors (MBBRs), have emerged as efficient alternatives in urban settings. By comparing the physicochemical analyses conducted in the three treatment units and evaluating the treatment efficiency of each unit, we will first establish the validity of the MBBR system for treating and recycling graywater, achieving up to 98% elimination rates for BOD5. Subsequently, the possibility of optimizing the system will be explored by evaluating the different treatment stages of MBBR reactors.