Influent Substrate Concentration Research Articles

Accurate evaluation for the biofilm-activated sludge reactor using graphical techniques

A complete graphical solution is obtained for the completely mixed biofilm-activated sludge reactor (hybrid reactor). The solution consists of a series of curves deduced from the principal equations of the hybrid system after converting them in dimensionless form. The curves estimate the basic parameters of the hybrid system such as suspended biomass concentration, sludge residence time, wasted mass of sludge, and food to biomass ratio. All of these parameters can be expressed as functions of hydraulic retention time, influent substrate concentration, substrate concentration in the bulk, stagnant liquid layer thickness, and the minimum substrate concentration which can maintain the biofilm growth in addition to the basic kinetics of the activated sludge process in which all these variables are expressed in a dimensionless form. Compared to other solutions of such system these curves are simple, easy to use, and provide an accurate tool for analyzing such system based on fundamental principles. Further, these curves may be used as a quick tool to get the effect of variables change on the other parameters and the whole system.

Computational Modelling of Large Scale Phage Production Using a Two-Stage Batch Process.

Cost effective and scalable methods for phage production are required to meet an increasing demand for phage, as an alternative to antibiotics. Computational models can assist the optimization of such production processes. A model is developed here that can simulate the dynamics of phage population growth and production in a two-stage, self-cycling process. The model incorporates variable infection parameters as a function of bacterial growth rate and employs ordinary differential equations, allowing application to a setup with multiple reactors. The model provides simple cost estimates as a function of key operational parameters including substrate concentration, feed volume and cycling times. For the phage and bacteria pairing examined, costs and productivity varied by three orders of magnitude, with the lowest cost found to be most sensitive to the influent substrate concentration and low level setting in the first vessel. An example case study of phage production is also presented, showing how parameter values affect the production costs and estimating production times. The approach presented is flexible and can be used to optimize phage production at laboratory or factory scale by minimizing costs or maximizing productivity.

Nitrogen removal performance and microbial community structure in the start-up and substrate inhibition stages of an anammox reactor

In this study, the nitrogen removal performance and microbial community structure were investigated during the start-up, instability, and recovery stages of an anaerobic ammonium oxidation (anammox) reactor loaded with compound carriers (shale ceramsite and suspended ball carrier). The results indicated that the anammox reactor successfully started up on 116th d when the nitrogen loading rate (NLR) reached 0.72±0.05kgNm-3d-1. The anammox reactor ran well with free ammonia (FA) at 13.65±2.69mg/L and free nitrous acid (FNA) at 39.49±10.95μg/L, indicating that its tolerance for FA and FNA was higher than that of granular sludge anammox reactors. The anammox system was inhibited when FA and FNA reached 29.65mg/L and 77.02μg/L, respectively. The tolerance of anammox bacteria towards FA and FNA decreased after this inhibition. The nitrogen removal performance could be efficiently recovered by decreasing the influent substrate concentration and increasing the hydraulic retention time (HRT). Candidatus Brocadia and Candidatus Jettenia, two genus-level anammox bacteria, were detected in this reactor using a high-throughput sequencing technique. After high substrate shock, the abundance of Candidatus Brocadia decreased while that of Candidatus Jettenia increased, which might be due to the competition between Candidatus Jettenia and Candidatus Brocadia. The relationships between anammox communities and operational factors were investigated via redundancy analysis (RDA), which showed that FA was the principal factor affecting the microbial community structure during the operation stage.

Bio-immobilization of dark fermentative bacteria for enhancing continuous hydrogen production from cornstalk hydrolysate

Mycelia pellets were employed as biological carrier in a continuous stirred tank reactor to reduce biomass washout and enhance hydrogen production from cornstalk hydrolysate. Hydraulic retention time (HRT) and influent substrate concentration played critical roles on hydrogen production of the bioreactor. The maximum hydrogen production rate of 14.2mmol H2L−1h−1 was obtained at optimized HRT of 6h and influent concentration of 20g/L, 2.6 times higher than the counterpart without mycelia pellets. With excellent immobilization ability, biomass accumulated in the reactor and reached 1.6g/L under the optimum conditions. Upon further energy conversion analysis, continuous hydrogen production with mycelia pellets gave the maximum energy conversion efficiency of 17.8%. These results indicate mycelia pellet is an ideal biological carrier to improve biomass retention capacity of the reactor and enhance hydrogen recovery efficiency from lignocellulosic biomass, and meanwhile provides a new direction for economic and efficient hydrogen production process.

Heterotrophic Ammonia and Nitrate Bio-removal Over Nitrite (Hanbon): Performance and microflora

A novel Heterotrophic Ammonia and Nitrate Bio-removal Over Nitrite (Hanbon) process, combining Short Nitrate Reduction (SNR) with Anaerobic Ammonia Oxidation (Anammox), was developed in a lab-scale continuous up-flow reactor. The substrate effects were investigated to characterize the performance of Hanbon process, and the corresponding microflora information was also revealed. Our results showed that the optimal substrate ratio of NH4+-N:NO3−-N:COD for the Hanbon process was 0.65:1:2.2. The volumetric nitrogen removal rate was up to 9.0 ± 0.1 kgN·m−3·d−1 at high influent substrate concentrations of NH4+-N 375 mg L−1, NO3−-N 750 mg L−1 and COD 1875 mg L−1, which was superior to the reported values of analogous processes. Moreover, the effluent total nitrogen concentration was able to meet the strict discharge standard (less than 10 mg L−1) at low influent substrate concentration of NH4+-N 26 mg L−1, NO3−-N 40 mg·L−1and COD 88 mg L−1. Illumina-based 16S rRNA gene sequencing results showed that Halomonas campisalis and Candidatus Kuenenia stuttgartiensis were the dominant bacteria in the SNR section and Anammox section at high substrate concentration condition. However, Halomonas campaniensis and Candidatus Brocadia brasiliensis were raised significantly at low substrate concentration condition. Hanbon process provided in the present work was flexible of treating wastewater with various nitrogen concentrations, deserving further development.

Simultaneous COD and VFA unmeasured process inputs estimation in actual anaerobic wastewater treatment processes

A Virtually Controlled Observer (VCO) was proposed to estimate both, the unmeasured states and the unknown inputs (influent substrate concentrations: Chemical Oxygen Demand (DCO) and Volatile Fatty Acids (VFA) in a 1m3 up-flow fixed-bed anaerobic digestion (AD) pilot plant. The VCO is developed without the full knowledge of the AD kinetics and consists of an asymptotic observer and an output feedback controller, in which, one of the observer inputs (the hypothetical -unmeasured- influent substrate concentration) is updated by a feedback control law, which is devised to regulate the estimation error of a measured output. Results show that the proposed observer is robust in the face model mismatch, load and operating conditions changes and sensor faults as it was able to reconstruct the influent substrate concentration.

A coupled system of half-nitritation and ANAMMOX for mature landfill leachate nitrogen removal

ABSTRACTA coupled system of membrane bioreactor-nitritation (MBR-nitritation) and up-flow anaerobic sludge blanket-anaerobic ammonium oxidation (UASB-ANAMMOX) was employed to treat mature landfill leachate containing high ammonia nitrogen and low C/N. MBR-nitritation was successfully realized for undiluted mature landfill leachate with initial concentrations of 900–1500 mg/L and 2000–4000 mg/L chemical oxygen demand. The effluent concentration and the accumulation efficiency were 889 mg/L and 97% at 125 d, respectively. Half-nitritation was quickly realized by adjustment of hydraulic retention time and dissolved oxygen (DO), and a low DO control strategy could allow long-term stable operation. The UASB-ANAMMOX system showed high effective nitrogen removal at a low concentration of mature landfill leachate. The nitrogen removal efficiency was inhibited at excessive influent substrate concentration and the nitrogen removal efficiency of the system decreased as the concentration of mature landfill leachate increased. The MBR-nitritation and UASB-ANAMMOX processes were coupled for mature landfill leachate treatment and together resulted in high effective nitrogen removal. The effluent average total nitrogen concentration and removal efficiency values were 176 mg/L and 83%, respectively. However, the average nitrogen removal load decreased from 2.16 to 0.77 g/(L d) at higher concentrations of mature landfill leachate.

Data-driven Control of the Activated Sludge Process: IMC plus Feedforward Approach

<p>In the work presented in this paper, data-driven control is used to tune an Internal Model Control. Despite the fact that it may be contradictory to apply a model-free method to a model-based controller, this methodology has been successfully applied to a Activated Sludge Process (ASP) based wastewater treatment. In addition a feedforward controller over the influent substrate concentration was also computed using the virtual reference feedback tuning and applied to the same wastewater process to see the effect over the dissolved oxygen and the substrate concentration at the effluent.</p>

Towards a continuous two-phase partitioning bioreactor for xenobiotic removal

The removal of a xenobiotic (4-chlorophenol) from contaminated water was investigated in a simulated continuous two-phase partitioning bioreactor (C-TPPB), fitted with coiled tubing comprised of a specifically-selected extruded polymer, Hytrel 8206. Wastewater flowed inside the tubing, the pollutant diffused through the tubing wall, and was removed in the aqueous bioreactor phase at typical biological removal rates in the C-TTPB simulated by varying aqueous phase throughput to the reactor. Operating over a range of influent substrate concentrations (500–1500mgL−1) and hydraulic retention times in the tubing (4–8h), overall mass transfer coefficients were 1.7–3.5×10−7ms−1, with the highest value corresponding to the highest tubing flow rate. Corresponding mass transfer rates are of the same order as biological removal rates, and thus do not limit the removal process. The C-TPPB showed good performance over all organic and hydraulic loading ranges, with removal efficiencies of 4CP in the tubing wastewater stream always ≥96%. Additionally, the presence of the Hytrel tubing was able to buffer increases in organic loading to the hybrid system, enhancing overall process stability. Biological testing of the C-TPPB confirmed the abiotic test results demonstrating even higher 4-chlorophenol removal efficiency (∼99%) in the tubing stream.

Continuous-flow combined process of nitritation and ANAMMOX for treatment of landfill leachate

Due to the difficulty in removing nitrogen from landfill leachate, a combined continuous-flow process of nitritation and anammox was applied to process mature leachate. The transformation rate of ammonia and nitrite accumulation ratio in A/O reactor were kept above 95% and 92% respectively through associated inhibition of free ammonia (FA) and free nitrous acid (FNA) to NOB. The total nitrogen volumetric load of anammox in an UASB reactor was brought up from 0.5kg/(m3·d) to 1.2kg/(m3·d) by gradually increasing influent substrate concentration and reducing hydraulic retention time (HRT). The results show that COD from mature leachate did not bring obvious inhibition effects to anammox. Under concentrations of influent ammonia and COD which were respectively 1330mg/L and 2250mg/L, the removal efficiencies of TN and COD reached 94% and 62% respectively. In the quantitative PCR reactions, the proportions occupied by AOB, NOB and anammox in A/O were 11.39%, 1.76% and 0.05% respectively; and proportions of those in UASB were 0.35%, 4.01% and 7.78% respectively.

Design and Development of Operational Diagram for Controlling the Performance of Activated Sludge Process with a Case Study

AbstractThis paper describes the design and development of an operational diagram that was developed based on the solids flux theory and connects the process operational parameters, namely, mixed-liquor suspended solids, flow, volume, area, and recycle ratio in an unified graphical form to facilitate the design and operation of secondary clarifiers for an Indian pulp and paper industry. A control strategy was developed based on steady-state control methods by utilizing the batch settling data generated in stationary phase complimented with artificial neural network models. These diagrams evaluate the operating strategies in response to changes in flow rate or settleability of solids. These operational diagrams developed based on steady-state control analysis, can be used for controlling the performance of the activated sludge process subjected to long term variations in the influent flowrate and substrate concentration. The plant operator can make a rational decision on his own to control the process usin...

Biomethane production and microbial community response according to influent concentration of molasses wastewater in a UASB reactor

This study aimed to investigate the interaction between methane production performance and active microbial community dynamics at different loading rates by increasing influent substrate concentration. The model system was an upflow anaerobic sludge blanket (UASB) reactor using molasses wastewater. The active microbial community was analyzed using a ribosomal RNA-based approach in order to reflect active members in the UASB system. The methane production rate (MPR) increased with an increase in organic loading rate (OLR) from 3.6 to 5.5g COD·L(-1)·day(-1) and then it decreased with further OLR addition until 9.7g COD·L(-1)·day(-1). The UASB reactor achieved a maximum methane production rate of 0.48L·L(-1)·day(-1) with a chemical oxygen demand (COD) removal efficiency of 91.2% at an influent molasses concentration of 16g COD·L(-1) (OLR of 5.5g COD·L(-1)·day(-1)). In the archaeal community, Methanosarcina was predominant irrespective of loading rate, and the relative abundance of Methanosaeta increased with loading rate. In the bacterial community, Firmicutes and Eubacteriaceae were relatively abundant in the loading conditions tested. The network analysis between operation parameters and microbial community indicated that MPR was positively associated with most methanogenic archaea, including the relatively abundant Methanosarcina and Methanosaeta, except Methanofollis. The most abundant Methanosarcina was negatively associated with Bifidobacterium and Methanosaeta, whereas Methanosaeta was positively associated with Bifidobacterium.

On-line heuristic optimization strategy to maximize the hydrogen production rate in a continuous stirred tank reactor

This work presents a simple heuristic approach to maximize the hydrogen production rate (HPR) using an on-line optimization strategy in a continuous stirred tank reactor. An initial investigation of the relationship between the organic loading rate (OLR) and HPR was used to propose the objective function of a nonlinear optimization problem, subject to a limited range of hydraulic retention times (HRTs) and a maximum productivity standard deviation. The inlet flow was the optimized variable while the influent substrate concentration was fixed at a constant value. The results showed a maximum HPR of 25.4L H2/(Ld), reached for an optimal OLR of approximately 100g COD/(Ld) and an HRT of approximately 4h. Following the optimization strategy, the specific HPR was increased from 7.52 to 16.35L H2/(gVSSd). The hydrogen yield increased from 1.8 to 2.32mol H2/mol glucose, representing an improvement of 29%. Finally, during the optimization period, the specific hydrogen production rate increased from 3.3 to 16.35L H2/(gVSSd), which suggested that the substrate was used by hydrogen-producing biomass rather than by other competing microorganisms.

Enhanced photo-H₂ production by unsaturated flow condition in continuous culture.

A biofilm photobioreactor under unsaturated flow condition (BFPBR-U) is proposed using a polished optical fiber as the internal light source for photo-H2 production in continuous culture. The main chamber was filled with spherical glass beads to create the reaction bed and the cells were immobilized to form a biofilm under unsaturated flow condition obtained by pumping substrate solution over a packing bed at a rate to create a thin fluid film and injecting the argon to maintain the gas phase space. The effects of operational conditions, including flow rate and influent substrate concentration, on the photo-H2 production performance were investigated. The unsaturated flow conditions eliminated the inhibition caused by high organic loading rate and enhanced light transmission efficiency, leading to an improvement in the photo-H2 production performance.

Optimization of process performance in a granule-based anaerobic ammonium oxidation (anammox) upflow anaerobic sludge blanket (UASB) reactor

In this study, the individual and interactive effects of influent substrate concentration (TNinf), hydraulic retention time (HRT) and upflow velocity (Vup) on the performance of anaerobic ammonium oxidation (anammox) in a granule-based upflow anaerobic sludge blanket (UASB) reactor were investigated by employing response surface methodology (RSM) with a central composite design. The purpose of this work was to identify the optimal combination of TNinf, HRT and Vup with respect to the nitrogen removal efficiency (NRE) and nitrogen removal rate (NRR). The reduced cubic models developed for the responses indicated that the optimal conditions corresponded to a TNinf content of 644–728mgNL−1, an HRT of 0.90–1.25h, and a Vup of 0.60–1.79mh−1. The results of confirmation trials were similar to the predictions of the developed models. These results provide useful information for improving the nitrogen removal performance of the anammox process in a UASB reactor.

Continuous Process Design Model Simulation for the Anaerobic Digestion of Vegetable Oil Wastewater

Simulation of a mathematical model for the design of steady-state continuous reactors required for the anaerobic digestion of wastewaters was carried out. This was obtained so as to make the design of continuous stirred tank reactor (CSTR) that would be used for the anaerobic digestion of vegetable oil wastewater (VOW) possible. The model considered the kinetics of the process which has been previously determined during the batch digestion of the wastewater. The hydraulic retention time (HRT) and solid retention time (SRT) which are important parameters required for the design were estimated by varying different model parameters such as efficiency of reactor, influent substrate concentration (So) and biomass concentration (X) at various food-microorganism ratios (F/M). The HRT was calculated for different reactor efficiency (E) varying in the range of 70-95% at a constant influent substrate concentration. It was observed that the HRT increased with increase in efficiency ranging between 1.10 to 7.06 days. HRT also increased as the biomass concentration increased. SRT at constant influent substrate concentration and biomass concentration were observed to increase as the reactor efficiency increased. The effect of different substrate concentration on HRT to attain a targeted efficiency in the CSTR under steady state condition was also studied. It was observed that HRT linearly increased with increase in influent substrate concentration at constant reactor efficiency and biomass concentration. HRT also increased with decrease in biomass concentration and constant reactor efficiency for a particular substrate concentration. There was also an increase in HRT as reactor efficiency increased at constant biomass and influent substrate concentrations. SRT calculated at E1 (70%) and E2 (80%) efficiencies were observed to decrease with increase in influent substrate concentration. As the efficiencies of the reactor increased, SRT was also observed to increase. With the information obtained from the model simulation, a continuous stirred tank reactor that would treat VOW by anaerobic digestion could be designed.

Performance of the ANAMMOX process using multi- and single-fed upflow anaerobic sludge blanket reactors

The performance of the ANAMMOX process was investigated in two identical laboratory-scale multi- and single-fed upflow anaerobic sludge blanket (UASB) reactors (denoted R1 and R0) at different hydraulic residence times (HRTs) varying from 2.06 to 1.52 h and NH4(+)-N inf concentrations ranging from 70 to 266 mg L(-1). The substrate removal efficiencies of both reactors decreased as HRT decreased and NH4(+)-N inf increased. The kinetics of these reactions were analyzed, and the Stover-Kincannon model was appropriate to describe the process kinetics of the reactors. In addition, an empirical model incorporating the influent substrate concentration and HRT adequately described R1. Shock experiments were conducted in which the reactors were subjected to transient shock loads. The results showed that the operation of R1 was more stable than that of R0, especially in response to the substrate shocks. Subsequently, the properties of the ANAMMOX granules and the effects of the feeding protocol on those properties were investigated.

Application of dynamic models to estimate greenhouse gas emission by wastewater treatment plants of the pulp and paper industry

Greenhouse gas (GHG) emission in wastewater treatment plants of the pulp-and-paper industry was estimated by using a dynamic mathematical model. Significant variations were shown in the magnitude of GHG generation in response to variations in operating parameters, demonstrating the limited capacity of steady-state models in predicting the time-dependent emissions of these harmful gases. The examined treatment systems used aerobic, anaerobic, and hybrid-anaerobic/aerobic-biological processes along with chemical coagulation/flocculation, anaerobic digester, nitrification and denitrification processes, and biogas recovery. The pertinent operating parameters included the influent substrate concentration, influent flow rate, and temperature. Although the average predictions by the dynamic model were only 10 % different from those of steady-state model during 140 days of operation of the examined systems, the daily variations of GHG emissions were different up to ± 30, ± 19, and ± 17 % in the aerobic, anaerobic, and hybrid systems, respectively. The variations of process variables caused fluctuations in energy generation from biogas recovery by ± 6, ± 7, and ± 4 % in the three examined systems, respectively. The lowest variations were observed in the hybrid system, showing the stability of this particular process design.

Correlating microbial community structure and composition with aeration intensity in submerged membrane bioreactors by 454 high-throughput pyrosequencing

For understanding of the microbial community structure and composition under different aeration intensities, 454 high-throughput pyrosequencing was applied to analyze the 16S rRNA gene of bacteria in two submerged membrane bioreactors (MBRs) under low (RL) and high aeration (RH) conditions. In total, 7818 (RL) and 9353 (RH) high-quality reads were obtained, and 1230 (RL) and 924 (RH) operational taxonomic units (OTUs) were generated at 3% cutoff level, respectively. 454 pyrosequencing could also reveal the minority bacteria that were hardly detected by the conventional molecular methods. Although the core populations were shared with highly functional organization (>80%), clear differences between the samples in the two MBRs were revealed by richness–diversity indicators and Venn analyses. Notably, microbial diversity was decreased under high aeration condition, and the evolution of the populations was observed mainly in the shared OTUs. Moreover, specific comparison down to the class and genus level showed that the relative abundances of β-Proteobacteria and γ-Proteobacteria in the RH community were respectively decreased by 41.5% and 66.6%, consistent with the observed membrane fouling mitigation during the reactor operation. It was also found that Nitrospira and Nitrosomonas, being nitrite oxidizing bacteria (NOB) and ammonium oxidizing bacteria (AOB), were the dominant phylogenetic groups at the genus level of both reactors, and that the high ratio of NOB to AOB populations well supported the complete ammonium oxidation performance in the two reactors. Although some populations of NOB and AOB decreased with the increase of aeration intensity, the functional stability of the nitrification process was less affected, probably due to the low influent substrate concentration and the high level of functional organization.

Simultaneous anaerobic sulfide and nitrate removal coupled with electricity generation in Microbial Fuel Cell

Two-chamber Microbial Fuel Cells (MFC) using graphite rods as electrodes were operated for simultaneous anaerobic sulfide and nitrate removal coupled with electricity generation. The MFC showed good ability to remove substrates. When the influent sulfide and nitrate concentrations were 780mg/L and 135.49mg/L, respectively, the removal percentages of sulfide and nitrate were higher than 90% and the main end products were nitrogen and sulfate. The MFC also showed good ability to generate electricity, and the voltage went up with the rise of influent substrate concentrations. When the external resistance was 1000Ω, its highest steady voltage was 71mV. Based on the linear relationship between the electrons released by substrates and accepted by electrode, it was concluded that the electricity generation was coupled with the substrate conversion in the MFC.