Influent Chemical Oxygen Demand Concentration Research Articles

NOB suppression by organic pollutants in mainstream single-stage partial nitrification/anammox (PN/A) process: Experimental evidence and modelling investigation

Effectively and stably suppressing nitrite oxidizing bacteria (NOB) under mainstream conditions is difficult for the wide application of the partial nitrification/anammox (PN/A) process. In this work, a continuous-flow single-stage PN/A reactor experiencing nitrate accumulation was restored by increasing the influent chemical oxygen demand (COD) concentrations. Experimental results showed that the total nitrogen removal efficiency quickly increased from 70 ± 2.54 % to 84 ± 1.21 % while effluent nitrate concentrations dropped from 30 ± 4.07 mg N/L to 10 ± 3.18 mg N/L following increasing the influent COD concentrations. A modified and calibrated mathematical model was employed to quantify the nitrogen conversion process and microorganism distributions under various influent COD levels. The detailed nitrogen metabolism network was calculated by labeling the source and sink of nitrite and nitrate. Simulation results revealed that influent COD suppressed NOB activity and enhanced anammox bacteria (AMX) activity in a short-term dynamic state while leading to the elimination of NOB and enrichment of the AMX under long-term pseudo-steady state. N-metabolism simulation results indicated that more nitrite (from 46.62 mg N/L to 55.05 mg N/L) was diverted to AMX with the assistance of heterotrophic bacteria (HET). NOB was outcompeted due to the dual pressure of competing with HET and AMX for oxygen and nitrite, respectively. Microbial analysis solidly supported these findings, showing that Candidatus_kuenenia, Thauera and Denitratisoma were enriched, while the relative abundance of Nitrospira decreased after COD addition. These findings demonstrate the potential of using organic pollutants to suppress and eliminate NOB, thereby enhancing the stability and efficiency of mainstream PN/A reactors.

Real-time prediction of the chemical oxygen demand component parameters in activated sludge model using backpropagation neural network

Activated sludge models are increasingly being adopted to guide the operation of wastewater treatment plants. Chemical oxygen demand (COD) is an indispensable input for such models. To ensure that the activated sludge mathematical model can adapt to various water quality conditions and minimize prediction errors, it is essential to predict the parameters of the COD components in real-time based on the actual influent COD concentrations. However, conventional methods of determining the components' contributions are too intricate and time-consuming to be really useful. In this study, the chemical oxygen demand in the actual waste water treatment plant was disassembled and analyzed. The research involved determining the proportions of each COD component, assessing the reliability of the measurement parameters, and examining potential factors affecting measurement accuracy, including weather conditions, pipeline conditions, and residents' habits. Then, a backpropagation neural network was developed which can deliver real-time predictions for five important contributors to COD in real time. In addition, using the receiver operating characteristics curve and prediction accuracy to evaluate the performance of the prediction model. For all five components, which SS, XS, SI, XA, and XH, the prediction accuracy of model was more than 80 %. The maximum deviation values of these parameters fall within the range of the actual detected values, suggesting that the model's predictions align well with real-world observations, and demonstrated prediction performance adequate for practical application in wastewater treatment. This article can provide research basis for the engineering application of activated sludge model and help for the intelligent upgrading of waste water treatment plants.

Anaerobic treatment of fruit and vegetable wastewater using EGSB: From strategies for regulating over-acidification to microbial community

Fruit and vegetable waste (FVW) are characterized by high-water content. Solid-liquid separation of FVW by crushing-extrusion physical pre-treatment provides fruit and vegetable wastewater (FVWW), and then for anaerobic biological treatment to recover methane, which is considered a cost-effective approach. However, anaerobic treatment of FVWW faces difficulties with low methane productivity and over-accumulation of volatile fatty acids (VFAs). In this study, the expanded granular sludge bed (EGSB) reactor was used for the anaerobic treatment of FVWW and the regulatory strategy to alleviate over-acidification was proposed. When the influent chemical oxygen demand (COD) concentration was 10000 mg/L, the hydraulic retention time (HRT) was 2 days, the organic loading rate (OLR) reached 5 g COD/L/d, the maximum methane productivity reached 301.14 ± 2.32 mL/g COD with a COD removal rate of 96 % ± 2 %. Lower VFAs accumulation was observed when decreasing the influent COD concentration to the same OLR compared with extending HRT, resulting in 38.5 % higher methane productivity. Decreasing the influent COD concentration not only benefited the enrichment of acetogens and hydrogenotrophic methanogens but also specifically enriched syntrophic bacteria. The enhanced syntrophic acetogenesis and hydrogenotrophic methanogens maybe the main reasons for promoting the degradation of propionate and butyrate and improving the methane productivity.

Performance evaluation of species varied fixed bed biofilm reactor for wastewater treatment of Dhobi Khola outfall, Setopul, Kathmandu, Nepal

The sustainability of wastewater treatment plants poses significant challenges for developing countries, necessitating substantial investment for operation and maintenance. Biofilm reactors seeded with specific species of microorganisms were investigated under controlled environmental conditions. However, the performance evaluation of such reactors under natural conditions remains largely underexplored. This study investigated wastewater treatment capabilities of bench-scale fixed bed biofilm reactors, employing various species (Wastewater Microbes, Pseudomonas, Algae, and a co-culture of Algae and Pseudomonas). The reactors (Treatments and Control) were filled with 28 mm nominal-size local aggregates as packing media, operated under different contact times, and subjected to varying concentrations of heavy metals (Zn, Cd). To assess the reactor performances, the Bland-Altman Plot and Chemical Oxygen Demand (COD) removal kinetics were evaluated.The results revealed that the reactor initiated with a co-culture exhibited the optimal COD removal efficiency, reaching 84 ± 1 %. The reactor initially seeded with wastewater microbes exhibited the highest heavy metal elimination, achieving 94 ± 1 % and 88 ± 1 % removal for Zn and Cd respectively. The wastewater-seeded reactor demonstrated the zero-order COD removal kinetic coefficient (k) of 46.41 mg/L/h at an average influent COD concentration of 558 mg/L at 10 h contact time. While Pseudomonas-seeded reactor demonstrated k = 0.73 mg/L/h at 20 h contact time with 69 mg/L influent COD and heavy metal concentrations Zn = 26 mg/L and Cd = 3.57 mg/L.The findings of this study suggest that variations in environmental conditions, contact time, and heavy metal concentration have minimal impact on the pollutant removal efficacy of the reactors, and provide robust evidence for their viability as a sustainable alternative in municipal wastewater treatment. The study also identifies the possibility of treating specific wastewater characteristics by altering the dominant species in the reactors, paving the way for further research on the efficacy of other microbial genomes in fixed bed biofilm reactors.

Introduction of Plug-flow Anaerobic Sludge Blanket (PASB) reactor for wastewater treatment

Plug-Flow Anaerobic Sludge Blanket Reactor (PASB) was used as the experimental reactor for the treatment as a replacement for Up-flow Anaerobic Sludge Blanket Reactor (UASB). The novelty of this study is to analyse the applicability of a novel post-treatment for anaerobically treated water by modifying UASB reactor which might be cost-effective, sustainable, and time-saving in the field of anaerobic treatment. Low-strength and high-strength (Leachate) wastewater (WW) were anaerobically treated under ambient temperature (28ºC-32ºC) with different Hydraulic Retention Time (HRT) values using a PASB and UASB setup. Chemical Oxygen Demand (COD) removal efficiency, biogas production rate, and gas composition were recorded and analysed. The average influent COD concentration of the low-strength wastewater was about 2070 ± 70 mg/L during the operation period of the reactor, and the COD removal efficiency of PASB was 90 ± 0.2 % which was 16 % enhancement at 10 h (hrs) HRT compared to UASB. The maximum biogas production recorded at this HRT was 13.72 ± 0.16 mL/h/L, which was 30.7 % higher than UASB. For leachate, COD concentration was about 6270 ± 220 mg/L, and COD removal efficiency was 97.2 ± 0.2 %. It is about a 23 % increase compared to UASB, at 8 hrs HRT and the maximum biogas production rate obtained for leachate treatment was 71.57 ± 1.53 mL/h/L and it was 30 % escalation than UASB. Hence, the PASB Reactor seems to be a desirable technique in compared with UASB to reach a comprehensive treatment efficiency, with efficient biogas exploitation to meet goals of renewable energy especially in tropical nations where less reactor heating is needed.

Analysis on Operation and Water Quality Characteristics of Centralized Wastewater Treatment Plants of Industrial Parks in Yellow River Basin, China

The Yellow River basin serves as an important economic belt and industrial base in China, featuring numerous industrial parks. However, alongside its economic significance, the basin struggles with significant water environmental challenges. This study analyzed the operational status, influent water quality, and energy consumption of 63 centralized wastewater treatment plants (WWTPs) from 54 major industrial parks in the Yellow River basin. The scale of these WWTPs was primarily within the range of 1 × 104~5 × 104 m3/d, with an average hydraulic loading rate of 53.8%. Aerobic treatment processes are predominant. The influent concentrations of chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP) in the WWTPs exhibited a right-skewed distribution. The BOD/COD ratio of the WWTPs fluctuated between 0.1 and 1.6, and 75% of the WWTPs showed a COD/TN ratio lower than eight. The average BOD5/TN was 2.7, and the probability of influent BOD5/TP > 20 was 84.6%. A significant linear correlation exists between the influent BOD and COD concentrations, while moderate linear relationships are also observed among NH3-N, TN and TP, emphasizing the importance of maintaining appropriate nitrogen and phosphorus levels for efficient pollutant removal. The average electricity consumption of WWTPs in the Yellow River basin in 2023 was 1.1 kWh/m3. It is important to upgrade these WWTPs and reduce their energy consumption. Further strengthening the construction of industrial wastewater collection and treatment facilities based on regional characteristics is recommended to promote the high-quality development of industrial wastewater treatment in the Yellow River basin.

Análise de desempenho dos sistemas de esgotamento sanitário do Sul do Brasil

ABSTRACT This study assesses the influent and effluent characteristics and the removal efficiency of 56 wastewater treatment plants (WWTPs) operating in Brazil’s southern region, in the Rio Grande do Sul state. The analysis encompasses the main secondary wastewater treatment processes used in the country, such as septic tank and anaerobic filter, activated sludge with sequencing batch reactor and with extended aeration, upflow anaerobic sludge blanket reactor followed by trickling filter, anaerobic and facultative ponds, and the combination of anaerobic, facultative, and maturation ponds. The parameters evaluated were biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammoniacal nitrogen (NNH3), total phosphorus (TP), total suspended solids (TSS), and Escherichia coli. The influent concentrations of BOD, COD, and TSS were considerably lower than other values reported in studies in Brazil, indicating that the analyzed WWTPs operate with a diluted influent, with respective average ranges of 38–189, 203–416, and 75–242 mg∙L−1. The effluent concentrations were also lower than the reference values, although the differences were not as pronounced as in the influent. No significant distinctions were observed between the removal efficiencies obtained and other results in the literature, except for TSS, which had a weaker performance. Concerning the technologies, lower performance was observed for BOD, COD, and TSS removal in the septic tank and higher removal rates of TP for the activated sludge systems. This study represents the first comprehensive dataset on the performance of WWTPs in Brazil’s southern region, contributing to the understanding of wastewater management practices in the country by indicating potential points for improvement.

Performance Analysis of Anaerobic Digestion Coupled with Simultaneous Nitrification and Denitrification Process for Treating Alcohol Precipitation Wastewater of Chinese Patent Medicine

The alcohol precipitation wastewater discharged from the production of Chinese patent medicine (CPM) has an extremely high chemical oxygen demand (COD) and poor biodegradability. In this study, the biological treatment method of anaerobic digestion coupled with simultaneous nitrification and denitrification (SND) was adopted to investigate its efficiency and to explore the mechanism of pollutant degradation in this process. The results showed that after 220 days of debugging, the coupled process operated stably. The influent COD, total nitrogen (TN), ammonium (NH4+-N), and lignin concentrations were 21,000 mg/L, 400 mg/L, 200 mg/L, and 1800 mg/L, respectively. The removal efficiencies of COD, TN, NH4+-N, and lignin were 97%, 85%, 96%, and 75%, respectively. Spectral detection technology analysis revealed that the wastewater contained alkanes, olefins, phenols, alcohols, unsaturated organics, aromatic compounds, and humic acids. After the treatment by each unit of the process, the three-dimensional fluorescence intensity decreased by 86%; the standard volume of fluorescence area integration declined by 78%; the stretching vibration band of aromatic compounds showed peak splitting; and the molecular weight parameter value in the ultraviolet region increased. These findings demonstrated that the humic acid substances in the wastewater were degraded, and the effect of removal of the macromolecular organic matter was remarkable.

Maximizing Bio-Hydrogen Production from an Innovative Microbial Electrolysis Cell Using Artificial Intelligence

In this research work, the best operating conditions of microbial electrolysis cells (MECs) were identified using artificial intelligence and modern optimization. MECs are innovative materials that can be used for simultaneous wastewater treatment and bio-hydrogen production. The main objective is the maximization of bio-hydrogen production during the wastewater treatment process by MECs. The suggested strategy contains two main stages: modelling and optimal parameter identification. Firstly, using adaptive neuro-Fuzzy inference system (ANFIS) modelling, an accurate model of the MES was created. Secondly, the optimal parameters of the operating conditions were determined using the jellyfish optimizer (JO). Three operating variables were studied: incubation temperature (°C), initial potential of hydrogen (pH), and influent chemical oxygen demand (COD) concentration (%). Using some measured data points, the ANFIS model was built for simulating the output of MFC considering the operating parameters. Afterward, a jellyfish optimizer was applied to determine the optimal temperature, initial pH, and influent COD concentration values. To demonstrate the accuracy of the proposed strategy, a comparison with previous approaches was conducted. For the modelling stage, compared with the response surface methodology (RSM), the coefficient of determination increased from 0.8953 using RSM to 0.963 using ANFIS, by around 7.56%. In addition, the RMSE decreased from 0.1924 (using RSM) to 0.0302 using ANFIS, whereas for the optimal parameter identification stage, the optimal values were 30.2 °C, 6.53, and 59.98 (%), respectively, for the incubation temperature, the initial potential of hydrogen (pH), and the influent COD concentration. Under this condition, the maximum rate of the hydrogen production is 1.252 m3H2/m3d. Therefore, the proposed strategy successfully increased the hydrogen production from 1.1747 m3H2/m3d to 1.253 m3H2/m3d by around 6.7% compared to RSM.

Prediction and optimization of the performance in an osmotic microbial fuel cell for water purification and bioelectricity production using a developed process model

To better understand and mathematically express the process of osmotic microbial fuel cells (OsMFCs), a model describing the integration of electrogen growth kinetics and osmotic mass transfer was developed and validated in this study. Low root mean square error (RMSE) and mean relative error (MRE) were obtained for simulated water flux, voltage generation, and chemical oxygen demand (COD) removal, which revealed a reasonable accuracy of the developed model. The local sensitivity analysis indicated that operating parameters such as draw solution concentration, anode hydraulic retention time (HRT) and influent COD concentration played important roles in influencing the key performance of OsMFCs. At the benchmark settings of anode HRT (4 h), influent COD (880 mg L−1), and external resistance (3000 Ω), a voltage increment of approximately 9.4% was predicted with an increased draw solution concentration from ∼0 to 3.0 mol L−1 (sodium chloride, NaCl), revealing the merit brought by the combined effects of water flux-facilitated proton advection and the high conductivities of electrolytes in OsMFCs. Shortening the anode HRT from 14 to 0.5 h at a fixed draw solution concentration of 0.5 mol L−1 was able to achieve approximately 9.3% increment in voltage output, whereas, the COD removal compromised from 99.2% to less than 20%. High COD removal rate of over 95% was obtained when the examined influent COD was as low as approximately 300 mg L−1. The optimization of combined parameters indicated that the optimized operation was at a draw solution concentration of ∼1.0 mol L−1 (NaCl), anode HRT ranging between 4 and 8 h, and a low influent COD of ∼300 mg L−1 at the model settings.

Landfill leachate treatment by graphite engineered anaerobic membrane bioreactor: Performance enhancement and membrane fouling mitigation

Low efficiency of anaerobic digestion and membrane fouling, treating landfill leachate, are big barriers in the application of anaerobic membrane bioreactor (AnMBR). Anaerobic digestion enhancement and membrane fouling mitigation of AnMBR with graphite addition, treating landfill leachate, were investigated in this study. The effect of graphite on organics removal, biogas production, methane content in biogas, membrane fouling, microbial responses and foulant compositions were analyzed. With the graphite addition, chemical oxygen demand (COD) removal of 78% was achieved for influent COD concentration of 3000 mg/l, which was significantly higher than the stage without graphite addition (65%) for influent COD concentration of 2000 mg/l. Similarly, methane content in biogas with graphite addition was 56%, while without graphite addition it was 46%. These digestion improvements were due to the promotion of organics degradation, facilitated by direct interspecies electron transfer (DIET) mechanism via graphite addition in AnMBR. The graphite addition prolonged membrane cleaning cycle from 13 days to 30 days. Protein content in loosely bound extracellular polymeric substance (LB-EPS) was the main fouling agent, which decreased with the graphite addition. The main mechanism behind membrane fouling mitigation was the protein content reduction in LB-EPS, which was biodegraded by Trichococcus being increased in relative abundance with the graphite addition. Furthermore, abundance of Denitratisoma decreased in anaerobic sludge and its accumulation reduced on membrane surface, subsequently membrane fouling was mitigated. Overall, graphite addition in AnMBR is a potential eco-innovative approach that efficiently removes pollutants from landfill leachate, enhances biogas quality and mitigates membrane fouling.

Contribution of nitrification and denitrification to nitrous oxide turnovers in membrane-aerated biofilm reactors (MABR): A model-based evaluation

As a novel and sustainable technology, membrane-aerated biofilm reactors (MABR) performing simultaneous nitrification and denitrification face the challenge of undesirable nitrous oxide (N2O) emission. Thereby, a comprehensive analysis of N2O turnover pathways and the affecting parameters in MABR are demanded for N2O mitigation strategies. In this work, a mathematical model describing three N2O turnovers pathways was studied to uncover the underlying mechanisms and the impacts of operational conditions on N2O turnovers in MABR system performing simultaneous nitrification and denitrification. The modeling results demonstrate that higher oxygen surface loading, longer hydraulic retention time (HRT) and lower influent chemical oxygen demand (COD) significantly induce higher N2O production factor (0.18%–3.3%). N2O turnovers are mainly regulated by the hydroxylamine (NH2OH) pathway and heterotrophic bacteria (HB) denitrification, accounting for 76%–87% and 10%–21%, respectively. In contrast, the thicker biofilm (i.e., 400–600 μm) causes lower N2O production factor (<0.13%), due to the shift of N2O turnover pathways to the ammonium oxidizing bacteria (AOB) denitrification pathway (7.1%–9.3%) and HB denitrification (90.7%–92.9%). Meanwhile, the result of in-biofilm N2O conversion rates shows that the NH2OH pathway and HB denitrification become the predominant N2O production pathway at the inner zone (0–160 μm) and the outer zone (290–350 μm) of the biofilm in MABR, respectively. The biofilm thickness at 160–280 μm can thus be regarded as an optimal zone to reduce N2O production in MABR, due to more electrons preferentially used for N2O reduction. The relatively low N2O production factor (<0.5%) together with >80% total nitrogen (TN) removal in MABR can be achieved by controlling the oxygen surface loading (1.821–3.641 g/m2/d) and influent COD concentrations (285–500 mg/L) within a certain range.

Effect of Increasing C/N Ratio on Performance and Microbial Community Structure in a Membrane Bioreactor with a High Ammonia Load.

Herein, the responses of the operational performance of a membrane bioreactor (MBR) with a high ammonium-nitrogen (NH4+-N) load and microbial community structure to increasing carbon to nitrogen (C/N) ratios were studied. Variation in the influent C/N ratio did not affect the removal efficiencies of chemical oxygen demand (COD) and NH4+-N but gradually abated the ammonia oxidization activity of sludge. The concentration of the sludge in the reactor at the end of the process increased four-fold compared with that of the seed sludge, ensuring the stable removal of NH4+-N. The increasing influent COD concentration resulted in an elevated production of humic acids in soluble microbial product (SMP) and accelerated the rate of membrane fouling. High-throughput sequencing analysis showed that the C/N ratio had selective effects on the microbial community structure. In the genus level, Methyloversatilis, Subsaxibacter, and Pseudomonas were enriched during the operation. However, the relative abundance of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) involved in nitrification declined gradually and were decreased by 86.54 and 90.17%, respectively, with influent COD increasing from 0 to 2000 mg/L. The present study offers a more in-depth insight into the control strategy of the C/N ratio in the operation of an MBR with a high NH4+-N load.

Adsorption of organic matter from papermaking wastewater by CoFe2O4-coated sand in batch and fixed-bed systems

The secondary treated effluents of pulp and paper mills contain high chemical oxygen demand (COD) that is associated with organic matter. Therefore, this study explores the adsorption of substances contributing to COD using CoFe2O4 and quartz sand-coated CoFe2O4 in batch and fixed-bed column experiments. X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy were used to characterize the adsorbents. The quartz sand-loaded CoFe2O4 exhibited a larger pore volume and average pore size. Batch experiments revealed that adsorption on CoFe2O4 closely fit the pseudo-second-order model. To explore the effects of bed depth, feed flow rate, and initial solution pH on the breakthrough characteristics of CoFe2O4-coated sand, fixed-bed column experiments were conducted, and the breakthrough curves were drawn from the ratio of influent COD concentration to effluent COD concentration. The breakthrough time decreased with an increase in the feed flow rate and initial pH but increased with the bed depth. According to the X-ray photoelectron spectroscopy analysis, CoFe2O4-coated sand showed excellent stability due to negligible leaching of metallic elements. These findings have important implications for the advanced treatment of industrial wastewater.

The operation characters of biocathode microbial electrochemical system with microbial separator for domestic wastewater treatment: Power generation, long-term stability, and organic removal

Biocathode microbial electrochemical system (MES) is considered as a sustainable and eco-friendly technology for wastewater treatment. With domestic wastewater, the anode/cathode matching ratios of biocathode MES are optimized to match the anodic respiration and cathodic oxygen reduction rates. One anode module matched with two identical cathode modules obtains the highest power density. The long-term stability of MES is examined for one year with optimized architecture. Stable power generation and organic removal performance are achieved. A low effluent chemical oxygen demand (COD) is obtained at 36 ± 14 mg L−1 with a COD removal of 89 ± 4%. To meet the discharge standard in China (COD<50 mg L−1), the required hydraulic retention time (HRT) shows a linear relationship with influent COD concentration, and the COD removal rates fluctuant from 0.80 ± 0.05 to 1.13 ± 0.04 kg m−3 day−1. In the view of stable electrode function and current generation, the influent COD range of 200–800 mg L−1 is the stable range for biocathode MES. The bio-diversities of electrode and microbial separators are changed with influent COD. High influent COD reduces the relative abundance of exoelectrogens on the anode and introduces heterotrophic bacteria on the cathode.

Isolation of two salt-tolerant strains from activated sludge and its COD degradation characteristics from saline organic wastewater

The efficient biological treatment of saline wastewater has been limited by the low activities of microorganisms under saline conditions. High salinity poses unbalance osmotic stress across the cell wall and even leads to cell plasmolysis. In this work, we aim to isolate salt-tolerant bacterial strains from activated sludge, and apply them for degrading chemical oxygen demand (COD) of saline organic wastewater. Two salt-tolerant strains were screened and isolated from activated sludge, which was domesticated with salty water for over 300 days. The two strains were identified as Bacillus cereus (strain A) and Bacillus anthracis (strain B) through 16S rRNA sequencing. The degradation characteristics of strain A were explored. The results showed the relative membrane permeability of strain A remained stable under high salt stress, which glycine and proline play an important role to maintain cell osmotic. The protein and soluble sugar amounts of strain were increased by higher salt concentrations. In simulating saline wastewater, the optimum culture temperature, pH, salinity, influent COD concentration and inoculation amount of strain A were 35 °C, 9, 4%, 8000 mg L−1, 6%, respectively. Optimal conditions could provide guidance for the treatment of practical saline wastewater. The linear regression model of each impact factor built based on the result PB experiment revealed that cross-linking time has the most significant influence on COD removal for salt-tolerant strains. It will provide theoretical basis for biological treatment of saline organic wastewater.

Application of isolated halophilic microorganisms suspended and immobilized on walnut shell as biocarrier for treatment of oilfield produced water

Salinity expressed as total dissolved solids (TDS), is the most challenging parameter in bioremediation of produced water which may inhibit the microbial activities and cause sedimentation problems. The present study explores the feasibility of using walnut shell as an inexpensive and accessible adsorbent-carrier for the immobilization of isolated halophilic microorganisms for treatment of synthetic oilfield produced water. The moving bed biofilm reactor (MBBR) was examined with influent chemical oxygen demand (COD) concentrations from 900 to 3600 mg L−1, TDS concentrations from 35,000–200,000 mg L−1, and cycle times from 24 to 72 h. Comparison of the MBBR with the conventional sequencing batch reactor (SBR) indicated that both systems operated at lower influent COD and TDS concentrations satisfactorily; but at higher TDSs (above 150,000 mg L−1) the MBBR was more resistant to the shocks of toxicity (salinity) and organic load relative to the SBR. Also, the effluent turbidity was lower and the free sludge settling property was more favorable in the MBBR with average sludge volume index (SVI) of 38.8 mL g−1 compared to the SBR with SVI of 98.09 mL g−1. Microbial identification confirmed the presence of eight dominant halophilic species which were hydrocarbon degraders and/or denitrifiers.

Evaluating the performance of a sequencing batch reactor for sanitary wastewater treatment using artificial neural network

AbstractIn this work, the performance of a sequencing batch reactor (SBR) was studied for treating sanitary wastewater of Yazd power plant, Iran. For this purpose, at the first, a pilot system was designed, installed, and started up. Then the effects of retention time, pH, temperature, influent chemical oxygen demand (COD) concentration, and air flow rate were investigated on the effluent concentration of COD. In SBR reactor used in the Yazd power plant, the microalga was not used for the wastewater treatment. In this case, the COD effluent output was, at the best conditions, approximately 92 mg/L. In the studied SBR system, we used the Chlorella vulgaris microalgae and microorganisms, simultaneously. In this case, the COD level reached 34 mg/L. An artificial neural network (ANN) was developed by applying Levenberg‐Marquardt training algorithm to predict the effluent concentration of COD. The optimum conditions were obtained at pH = 8, temperature of 30°C, influent COD concentration of 600 mg/L, and air flow rate of 50 L/min. ANN predicted results were in good agreement with the experimental data with a validation coefficient of determination (R2) and validation mean square error of 0.962 and 0.0015, respectively.

Feasibility of Adjusting the S2O32-/NO3- Ratio to Adapt to Dynamic Influents in Coupled Anammox and Denitrification Systems.

In this study, anammox, sulfur-based autotrophic denitrification, and heterotrophic denitrification (A/SAD/HD) were coupled in an expanded granular sludge bed (EGSB) reactor to explore the feasibility of enhancing denitrification performance by adjusting the S2O32−/NO3− (S/N) ratio to accommodate dynamic influents. The results indicated that the optimal influent conditions occurred when the conversion efficiency of ammonium (CEA) was 55%, the S/N ratio was 1.24, and the chemical oxygen demand (COD) was 50 mg/L, which resulted in a total nitrogen removal efficiency (NRE) of 95.0% ± 0.5%. The S/N ratio regulation strategy was feasible when the influent COD concentration was less than 100 mg/L and the CEA was between 57% and 63%. Characterization by 16S rRNA sequencing showed that Candidatus Jettenia might have contributed the most to anammox, while Thiobacillus and Denitratisoma were the dominant taxa related to denitrification. The findings of this study provide insights into the effects of CEA and COD on the performance of the A/SAD/HD system and the feasibility of the S/N ratio regulation strategy.

Removal of organics from shale gas fracturing flowback fluid using expanded granular sludge bed and moving bed biofilm reactor

ABSTRACT Shale gas fracturing flowback fluid contains various degradation difficulty organic compounds after hydraulic fracturing. A hybrid treatment method was developed for treating flowback and produced water (FPW) using pre-treatment (NaClO) followed by the expanded granular sludge bed (EGSB) and moving bed biofilm reactor (MBBR). Gas chromatography–mass spectrometry (GC-MS) was employed to detect organic composition in the FPW, the pre-treated FPW, EGSB and MBBR effluent. FPW had high chemical oxygen demand (COD) (3278 mg/L) and the majority of organic compounds in the FPW composed of alkanes and heteroatomic compounds with polymers and polarity. 20% COD removal was achieved after adding 5 g/L of NaClO in FPW (pH = 7, stirring for 20 mins) as pre-treatment and > C30 alkanes in FPW were decomposed a lot in the pre-treatment process. The pre-treated FPW was diluted (volumetric ratio of 20%/50%) with synthetic wastewater/pure water. In the final stage of operation, Cl− and COD concentration of influent to EGSB-MBBR system was around 7000 ± 100 mg/L and 3000 mg/L. EGSB-MBBR system achieved 93.84% COD removal rate, in which EGSB dominated COD removal (>80%). According to the GC-MS results, EGSB had an increase of C11-C30 compounds and a decrease of less C1-C10 content due to the consumption of > C30 compounds and low molecular weight (LWM) compounds. Meanwhile, aerobic microorganisms in MBBR metabolized LWM organics which contributed a lot to the COD removal (25.06∼68. 22%). The results indicated that the pre-treatment and biological EGSB-MBBR system could be an efficient option used for FPW treating.