Real Wastewater Treatment Plant Research Articles

Critical Factors Facilitating Candidatus Nitrotoga To Be Prevalent Nitrite-Oxidizing Bacteria in Activated Sludge.

Nitrite oxidation is the primary pathway that generates nitrate in engineered systems. However, little is known about the role of a novel nitrite-oxidizing bacteria (NOB) genus Candidatus Nitrotoga in activated sludge systems. To elucidate key factors that impact NOB community composition, laboratory-scale sequencing batch reactors (SBRs) were designed and operated under the same conditions as real wastewater treatment plants to achieve considerable nitrogen removal and similar community; then, different conditions including temperature (T), dissolved oxygen (DO), free nitrous acid (FNA), and free ammonia (FA) were applied. The 16S rRNA gene-based PCR and sequence analysis illustrated that Ca. Nitrotoga were abundant even at ambient temperature, thus further challenging the previous conception of them being solely cold-adapted. Ca. Nitrotoga are less competitive than Nitrospira during oxygen deficiency, indicating its lower affinity to dissolved oxygen. Ca. Nitrotoga are the dominant nitrite oxidizers under regular exposure to FNA and FA due to their relatively higher resistance than other NOB toward these two effective biocides. Therefore, this study demonstrates that Ca. Nitrotoga can play an important role in biological nitrogen removal and also highlights the need for multiple strategies for NOB suppression for the next-generation, shortcut nitrogen removal.

A techno-economic assessment of implementing power-to-gas systems based on biomethanation in an operating waste water treatment plant

The aim of the present study is to assess the techno-economic viability of integrating biomethanation into power to gas systems in a real waste water treatment plant (WWTP). The research is the first attempt to assess the viability of several scenarios based on the biomethanation technology that include both in- and ex-situ biomethanation as well as utilisation of on-site renewable electricity and grid electricity in a transient mode.Five scenarios were designed and evaluated and the calculated LCOE lies between 127.8 and 159.8 £/MWh. The consideration of existing policy mechanisms and revenues from by-products reduces the LCOEs to 31.4–68.1 £/MWh. The execution of a sensitivity analysis exposed that the electricity price and the electrolyser cost are the main cost contributors in all the scenarios. Future techno-economic advances along with imposing appropriate policy incentives can create the proper framework for two scenarios to generate profits. The study concludes that current and future power to gas application should focus on utilising on-site generated electricity.

Modeling of a real industrial wastewater treatment plant based on aerated lagoon using a neuro-evolutive technique

Aerated lagoons are biological systems used for the treatment of different types of wastewaters and many operating parameters influence the performance of these systems. Thus, in the current study, an industrial aerated lagoon system was modeled in terms of the operating parameters with the goal of predicting its performances under different operating conditions in order to highlight possible bottlenecks or potential improvements. For this purpose, a neuro-evolutive approach, combining differential evolution (DE) algorithm and artificial neural networks (ANN), was employed. Two DE variants based on opposition-based learning and of chaos theory were used to determine the optimal models and to perform a process optimization. Multiple models in various configurations (simple or organized in stacks, with single or multiple outputs) were determined. The mean squared error of the best solutions were in the order of 10−4, illustrating a good agreement between the model predictions and experimental data and demonstrating the effectiveness and reliability of the developed models.

Hydroxyl and sulfate radical advanced oxidation processes: Application to an agro-industrial wastewater

In this study, the effectiveness of a UV-A LEDs system, transition metal activators (Fe and Co) and different oxidants (hydrogen peroxide, H 2 O 2 ; peroxymonosulfate, PMS and persulfate, PS) were evaluated in the degradation of an elderberry wastewater. Several oxidation processes can be applied using the pointed out oxidants, UV radiation and transition metals, which can be classified as hydroxyl radical advanced oxidation processes (HR-AOPs) and sulfate radical advanced oxidation processes (SR-AOPS). The initial trials achieved 99% of TOC removal in UV-A LED/H 2 O 2 (with multi-step additions)/Fe 2＋ and with PMS (single addition)/Co 2 + processes, which were afterwards optimized for metal activator dosage. The UV-A LED/H 2 O 2 (multi-step addition)/Fe 2＋ process demonstrated a lower TOC removal when the Fe 2＋ concentration was reduced (50 mg/L – 99% removal and 25 mg/L only 75%). On the other hand, PMS (single step addition)/Co 2 + process still presented 99% of TOC removal, even when the Co 2 + concentration decreased from 50 to 25 mg/L. Bearing in mind this performance, the Co 2 + concentration was optimized achieving the following optimal operational conditions: [PMS] = 45 mM; [Co 2 + ] = 7.5 mg/L; pH = 3 and reaction time = 120 min. In addition, PMS/Co 2 + process allows to increase the biodegradability (BOD 5 /COD) ratio from 0.30 to 0.53 mg O 2 /L of treat water. Hence, the PMS/Co 2 + oxidation process can be considered a promising technology for application in real scale agro-food wastewater treatment plants, since it shows a very good compromise in terms of TOC removal and reduced carbon footprint. • Hydroxyl and sulfate radicals-based AOPs in elderberry wastewater treatment. • Radical generation by UV-A LEDs, transition metals and oxidants (H 2 O 2 , PMS and PS). • Influence of single and multiple additions of oxidants. • UV-A LED/H 2 O 2 (multi-additions)/Fe(II) and PMS(single addition)/Co(II) reach 99% TOC removal. • PMS/Co(II) optimal conditions: [PMS] = 45 mM; [Co(II)] = 7.5 mg/L; pH = 3 and 120 min.

Upgrading fluidized bed bioelectrochemical reactors for treating brewery wastewater by using a fluid-like electrode

Anaerobic digestion has historically shown critical operational limitations for treating industrial wastewater. Our work aims to evaluate the resilience capacity of a novel concept so-called microbial electrochemical fluidized bed reactor (ME-FBR) for treating real brewery wastewater under continuous operation mode over one year period. All assays were run in parallel using a conventional anaerobic fluidized bed reactor (AFBR). The resilience tests were designed attending to the most typical operational problems showed by the AFBR technology in real brewery wastewater treatment plants. Four different stress situations were tested: i) pollutants overloading (as high as 51.2 kgCOD/m3 d), ii) presence of an active biocide in the fed stream (5% Vbiocide/Vreactor), iii) operation of the reactors after long starvation periods (16 days) and iv) operation at low temperature (<25 °C). Our pre-pilot scale ME-FBR outperformed traditional AFBR for wastewater treatment capacity under all stress test regarding COD removal rate, total nitrogen (TN) removal rate and bioenergy recovery (bioelectrochemical-assisted hydrogen generation). Among all stress test, low temperatures and long starvation periods deeply decrease the robustness of both technologies.

Activated sludge and other aerobic suspended culture processes.

This paper provides an overview of activated sludge related to suspended growth processes for the year 2019. The review encompasses process modeling of activated sludge, microbiology of activated sludge, process kinetics and mechanism, nitrogen and phosphorus control, design, and operation in the activated sludge field. The fate and effect of xenobiotics in activated sludge, including trace organic contaminant and heavy metal xenobiotics, which had influence on the growth of suspended sludge, are covered in this review. Compared to past reviews, many topics show increase in activity in 2019. These include, biokinetics process of aerobic granular sludge formation, pyrolysis kinetic mechanism of granular sludge. These topics are referred to formation and disintegration of granular sludge. Other sections include activated sludge settling model, toxicity resistant microbial community, nitritation-anammox processes for nitrogen removal, and respirometry used in the operation of real wastewater treatment plant are especially highlighted in this review. PRACTITIONER POINTS: Biokinetics process of aerobic granular sludge formation Toxicity resistant microbial community in activated sludge Nitritation-anammox processes for nitrogen removal in activated sludge.

Microbial fuel cell for effluent treatment and sustainable power generation

ABSTRACT Microbial Fuel Cell (MFC) is an attractive and sustainable option for the conversion of effluent organics into bioelectricity. In the present study, vertically configured MFC reactors have been designed to simulate a real wastewater treatment plant so that enhanced degradation of effluent organics and sustained electrical power generation could be achieved. Anaerobic biomass and tannery effluent was used as anolyte, KMnO4 (39 mM) in phosphate buffer (700 mM) was used as catholyte. The concept of diligent mechanical disintegration has been introduced to increase the microbial activity, intended to enhance both degradation of effluent organics and generation of electricity. The operating parameters of MFC were optimized by RSM, implemented in batch studies and further extended for continuous operation. In batch studies the COD removal of 72% and 85%, with a power generation of 0.21 and 0.32 mW was achieved in 20 days HRT, whereas in continuous studies the COD removal was 57% and 72.5% in HRT of 1 day, and the power generation was 0.34 and 0.57 mW for control and experimental runs, respectively. Thus, the continuous mode of operation was beneficial than batch mode. Further, the generated power, illumination of LEDs could be demonstrated.

Techno-economic optimization of biogas-fueled micro gas turbine cogeneration systems in sewage treatment plant

The aim of this paper is to investigate the feasibility of a combined cooling, heating, and power generation system with a micro turbine using biogas as the fuel to supply the heat and electricity demands in a real wastewater treatment plant. The plant is optimized using the system’s total cost rate and the amount of the produced biogas as objective functions. The anaerobic digester is modeled using the ADM1 model. The optimization variables include digester hydraulic retention time, compressor pressure ratio, isentropic compressor efficiency, recuperator pinch time temperature, turbine isentropic efficiency, turbine input temperature, and the number of micro turbines. In the first scenario (business as usual), the optimal values of the system’s total cost rate and the amount of the produced biogas are 0.02561 $/s and 12.6235*103m3/day, respectively. In the environmental scenario, the optimum values of the total cost rate and the biogas flow rate are 0.0652 $/sand 12.6901*103m3/day, respectively. Scenario 1 has lower values of total cost rate and levelized cost of electricity and higher CO2 emissions than scenario 2. The surplus of electricity from the plant may be exported to the grid in the first scenario. However, some electricity will be imported from the grid in scenario 2. Finally, the effects of some important parameters have been assessed on the total cost rate using Sobol sensitivity analysis. Hydraulic retention time, power purchase price, and discount rate have the highest impacts on the system’s total cost rate by 15% while AD temperature has the lowest effect on total cost rate by 6%. In general, the results of this paper could be employed as a decision support tool for policy makers in energy sector as well as wastewater treatment plant managers to supply the energy demand of their plant.

Identification and Localization of Hydrodynamic Anomalies in a Real Wastewater Treatment Plant by an Integrated Approach: RTD-CFD Analysis

The presence of hydrodynamic anomalies (HAs) in biological reactor reduces pollutants removal yields and increases management costs. This work aims to study the hydrodynamic behaviour of biological reactors of a real wastewater treatment plant (WWTP) in order to detect the presence of hydrodynamic anomalies (dead volume and bypass). The identification and the localization of these anomalies were conducted by an integrated residence time distribution (RTD) analysis - computational fluid dynamic (CFD) numerical analysis. From the results of the RTD analysis a dead volume of 30% was quantified without bypass. The three-dimensional CFD model revealed a dead volume inside the oxidation/nitrification tank equal to 10% located downstream of the baffle wall. Employing the RTD-CFD integrated analysis approach, the size of dead volume located in the denitrification reactor was quantified as equal to 60%. RTD analysis allowed for the quantification of the HAs while CFD analysis provided for the position of the HAs with reliable accuracy. RTD-CFD integrated approach is a preparatory tool for planning any corrective actions in a focused way in order to use all the volume of the reactor, maximizing the efficiency of the treatment processes, minimizing management costs and reducing the consumption of energy.

Fe3+-NTA as iron source for solar photo-Fenton at neutral pH in raceway pond reactors

This work presents, for the first time, a kinetic study of the solar photo-Fenton process at neutral pH mediated by the Fe3+-NTA complex (molar ratio 1: 1) applied to remove contaminants of emerging concern (CECs). To this end, wastewater treatment plant (WWTP) secondary effluents were treated in a raceway pond reactor (RPR) at pilot plant scale with 0.1 mM Fe3+-NTA and 0.88 mM H2O2 under average solar UVA irradiance of 35 W/m2. Sulfamethoxazole and imidacloprid, at 50 μg/L of initial concentration each, were selected as model CECs. Up to 40% of the sum of both model CECs was removed from simulated WWTP effluent by the Fe3+-NTA Fenton-like process, and >80% was removed by solar photo-Fenton. The effect of liquid depth in the reactor was evaluated, showing an increase of the treatment capacity from 12 mg CEC/m2·h to 18 mg CEC/m2·h when liquid depth increased from 5 to 15 cm. Afterwards, these results were validated with real WWTP effluents and compared with the results obtained with the Fe3+-EDDS complex under the same operating conditions. The same CEC removal rates were obtained with Fe3+-NTA and Fe3+-EDDS at 5 cm of liquid depth (kinetic constants of 0.110 min−1 and 0.046 min−1 for sulfamethoxazole and imidacloprid, respectively). Conversely, at 15 cm of liquid depth, the degradation rates were lower with Fe3+-NTA (kinetic constants of 0.034 min−1 for sulfamethoxazole and 0.017 min−1 for imidacloprid), whereas with Fe3+-EDDS the values were 0.076 min−1 and 0.047 min−1 for sulfamethoxazole and imidacloprid, respectively. Regarding process cost estimation, the use of NTA as iron chelate for solar photo-Fenton at neutral pH at pilot plant scale resulted very cost-effective (0.13–0.14 €/m3) in comparison with the use of EDDS (0.46–0.48 €/m3) at the two liquid depths tested.

Biomethane production using an integrated anaerobic digestion, gasification and CO2 biomethanation process in a real waste water treatment plant: A techno-economic assessment

The biomethanation of CO2 from anaerobic digestion within the power to gas concept has recently emerged as a promising technology to upgrade biogas, to decarbonise the domestic and industrial heat sector, provide long term energy storage and deliver grid balancing services. In addition, the utilisation of the digestate, through a process such as gasification, offers a circular economy approach and has the potential to enhance the deployment of power to gas systems. To this direction, the study focuses on exploring the techno-economic feasibility of coupling biomethanation with digestate gasification for the wastewater industry. The study constitutes the first endeavour to assess the viability of such an integrated energy system. Four different scenarios have been designed and assessed. The energy efficiency of the concepts lies between 26.5% and 35.5% while the minimum selling price (MSP) of biomethane is in the range of 135–183 £/MWh. The implementation of appropriate policy mechanisms and the inclusion of by-products revenues reduces the MSPs by approximately 32%–42%. The conduction of a typical sensitivity analysis has identified the electricity price as the prime cost driver and this is followed by the cost of the electrolyser or the gasification plant depending on the scenario. Finally, a 2030 analysis, that incorporates projected techno-economic advances, has been carried out and revealed that under certain circumstances profits can be generated.

Energy saving for air supply in a real WWTP: application of a fuzzy logic controller.

An unconventional cascade control system, for the regulation of air supply in activated sludge wastewater treatment plants (WWTPs), was tested. The dissolved oxygen (DO) set point in the aeration tank was dynamically calculated based on effluent ammonia concentration, following a fuzzy logic based approach. First, simulations were conducted, according to the BSM2 protocol, for a general comparison with more conventional control strategies. It turned out that the effluent quality could be improved by 7-8%, based on the EQI parameter. Moreover, the aeration energy requirement could be reduced up to 13%. Subsequently, the system was installed in a full-scale WWTP. While stably complying with the ammonia effluent standard (10 mg/L), excess air supply was prevented, and a reduction of the specific power consumption (kWh/kgCODremoved) of 40-50% was recorded with respect to the previously installed PID controller (fixed DO set point).

Detection and evaluation of microbeads and other microplastics in wastewater treatment plant samples.

Microplastics (MPs) are ubiquitously spread in water environment and have raised global concerns due to their adverse effect to biological and ecological systems. Wastewater treatment plants have been reported to be an important route of releasing MPs into the environment. As a great source of MPs in number in wastewater, the characteristics of microbeads have hardly been studied. In this study, the variation of the characteristics of microbeads prior to and after incubating in wastewater samples has been identified. Reported digestion methods of acid, alkaline, enzymatic, and wet preoxidation digestion were subsequently applied to assess their efficacy for digesting microbeads from the wastewater, and enzymatic digestion has shown the optimal efficacy. Finally, enzymatic digestion was applied to evaluate microbeads and other MPs in real wastewater treatment plant samples. It is shown that the sequential treatment of fine screen, grit chamber, and improved sequencing batch reactor activated sludge processes were able to remove 72% pellets in number and 43% MPs in total, while a large portion was still remaining after the secondary treatment. This study set a base for understanding the characteristics and occurrence of MPs, especially microbeads in wastewater samples.

Simultaneous removal of BOD, N and P in a single continuous flow real scale activated sludge reactor with cyclic aeration

Abstract The present study evaluates the performance of a real scale domestic wastewater treatment plant (WWTP), operating under continuous flow conditions with ‘extremely high sludge age’, designed to remove organic matter and perform nitrification-denitrification within a single reactor under cyclic aeration. Composite samples were withdrawn from the reactor for one week and their analysis results compared satisfactorily with the calculations of the design models. The WWTP is operating under stable conditions with a BOD5 removal of 86%, COD removal of 87%, TKN removal of 73% and, unexpectedly, a stable removal of 55% of total phosphorus. The design of the WWTP is simple and consists of a single aeration tank with a kinetic selector and a secondary sedimentation tank, operating under cyclic conditions in the aeration tank, with 45-minute aeration on (oxic environment) and 15 minutes aeration off (anoxic environment). The system can be applied to upgrade WWTP from secondary to tertiary treatment with only small modifications. A phosphorus removal mechanism is also proposed.

Data-driven decision-making for wastewater treatment process

Membrane fouling has become a serious issue for the safe operation of wastewater treatment process (WWTP). To deal with this problem, this paper proposes a data-driven decision-making method to reduce the incidence of membrane fouling in WWTP. The main novelties of this proposed data-driven decision-making method are threefold. First, a long-term prediction method, based on a self-organizing deep belief network (SDBN) and the multi-step prediction strategy, is developed to predict the membrane permeability. Second, a multi-warning method, based on an independent component analysis-principal component analysis (ICA-PCA) algorithm, is proposed to detect and warn membrane fouling with multiple indicators. Third, a multi-category diagnosis method, based on the kernel function, is designed to diagnose membrane fouling for providing the decision support. Finally, an intelligent decision-making system, consisting the above methods and required sensors, is developed for some real wastewater treatment plants. The experimental results demonstrated the efficiency and effectiveness of the proposed data-driven decision-making method.

Effective removal of Cu(II) from aqueous solution over graphene oxide encapsulated carboxymethylcellulose-alginate hydrogel microspheres: towards real wastewater treatment plants.

In the current study, the graphene oxide (GO) encapsulated carboxymethyl cellulose-Alginate (CMC-Alg) hydrogel microspheres were prepared via ionotropic gelation method and characterized using FTIR, TGA, SEM-EDS and surface charge by determining pHpzc. The adsorption of Cu2+ ions from aqueous solution on the graphene oxide embedded CMC-Alg was studied under different experimental conditions, and the results showed that embedded beads had high adsorption capacity compared with pure CMC-Alg beads due to synergetic effect between functional groups GO and CMC-Alg matrix. Adsorption capacities at equilibrium were calculated experimentally as 22.10, 39.96, 41.72 and 64mg/g for pure CMC-Alg, CMC-Alg/GO 1%, CMC-Alg/GO 3% and CMC-Alg/GO 5%, respectively. The adsorption kinetics were found to follow the pseudo-second-order, and the equilibrium data fitted well with the Langmuir adsorption isotherm. Moreover, the intraparticle diffusion model has been inspected pointing that the adsorption process was found to be sequence of surface adsorption and intraparticle diffusion (IPD). The results suggest that graphene oxide embedded CMC-Alg bead matrix can be efficiently used as an adsorbent for metal ions removal from wastewater.

Enhanced photocatalytic removal of amoxicillin with Ag/TiO2/mesoporous g-C3N4 under visible light: property and mechanistic studies.

In present study, an efficient ternary Ag/TiO2/mesoporous g-C3N4 (M-g-C3N4) photocatalyst was successfully synthesized through depositing Ag nanoparticles (NPs) on the surface of TiO2/M-g-C3N4 heterojunction. Ag/TiO2/M-g-C3N4 nanocomposite displayed the highest degradation efficiency for amoxicillin (AMX) compared to TiO2/M-g-C3N4 heterojunction, M-g-C3N4, and bulk-g-C3N4 (B-g-C3N4). The removal efficiency of AMX in real situation, surface water (SW), hospital wastewater (HW), and waste water treatment plant (WWTP) also were studied to illustrate the effectiveness of Ag/TiO2/M-g-C3N4 photocatalysts. The vulnerable atoms in AMX structure were revealed through DFT calculation. Additionally, the dominating active groups produced in time of the photocatalytic procedure were determined on account of free radical trapping experiments and ESR spectra. The mechanism of photocatalytic degradation was proposed and verified. The transfer of the electrons and the inhibition of the recombination of photogenerated electron-holes were enhanced effectively under the synergistic effect of the Ag NPs and TiO2. As a consequence, the catalytic activity of the composite was improved under visible light.

Predicting the Capability of Carboxylated Cellulose Nanowhiskers for the Remediation of Copper from Wastewater Effluent Using Statistical Approach

This study focused on remediation of spiked Cu(II) from wastewater effluent obtained from a real wastewater treatment plants (WWTPs) using oxidised cellulose nanowhisker (CNW) adsorbents. Response surface methodology (RSM) and artificial neural network (ANN) were used to develop an approach for the remediation of spiked Cu(II) from wastewater effluent. As remediation processes from wastewater are often complicated due to the variation in wastewater compositions, results obtained from the benchmark experiments are included as one of the independent variables for ANN modelling. This novel approach and the outcomes are allowed for the first time, since most studies do not consider matrix variability and its impact when evaluating the efficiency of an adsorbent. Moreover, to confirm the model suitability, additional 10 unseen experiments, which were not used in developing both models, were chosen to represent the system of conditions both inside and outside the system. This study found that the ANN model accounting for wastewater variability was superior to the RSM model and to the ANN model not including wastewater variability, in terms of the coefficient of determination (R2), the absolute average deviation (AAD) and root mean squared error (RMSE) when predicting the efficiency of Cu(II) removal from the wastewater matrix.

Simultaneous removal of hydrogen sulfide and volatile organic sulfur compounds in off-gas mixture from a wastewater treatment plant using a two-stage bio-trickling filter system

Simultaneous removal of hydrogen sulfide (H2S) and volatile organic sulfur compounds (VOSCs) in off-gas mixture from a wastewater treatment plant (WWTP) is difficult due to the occasional inhibitory effects of H2S on VOSC degradation. In this study, a two-stage bio-trickling filter (BTF) system was developed to treat off-gas mixture from a real WWTP facility. At an empty bed retention time of 40 s, removal efficiencies of H2S, methanethiol, dimethyl sulfide, and dimethyl disulfide were 90.1, 88.4, 85.8, and 61.8%, respectively. Furthermore, the effect of lifting load shock on system performance was investigated and results indicated that removal ofboth H2S and VOSCs was slightly affected. Illumina Miseq sequencing revealed that the microbial community of first-stage BTF contained high abundance of H2S-affinity genera including Acidithiobacillus (51.43%), Metallibacterium (25.35%), and Thionomas (8.08%). Analysis of mechanism demonstrated that first stage of BTF removed 86.1% of H2S, mitigating the suppression on VOSC degradation in second stage of BTF. Overall, the two-stage BTF system, an innovative bioprocess, can simultaneously remove H2S and VOSC.

Comparison of Biodegradation of Fats and Oils by Activated Sludge on Experimental and Real Scales

Fats and oils are the most common pollutants in wastewater, and are usually eliminated through physical processes in wastewater treatment plants, generating large amounts of fats and residual oils that are difficult to dispose of and handle. The degradation of fatty wastewater was studied in a real wastewater treatment plant and a laboratory scale treatment unit. The wastewater treatment plant, located in Chile, was designed for a population of 200,000 inhabitants. It includes an aerobic digester that receives fat and oils retained in a degreaser and treats the fats and oils together with biomass. The biodegradation of fats and oils was analyzed in both wastewater treatment systems. Key parameters were monitored such as the concentration of fats and oils in the influents and effluents, mass loading, and the efficiency of biodegradation. The mass loading range was similar in both wastewater treatment systems. In the experimental activated sludge plant, the biodegradation of fats and oils reached levels in the range of 64% to 75%. For the wastewater treatment plant with an aerobic digester, the levels of biodegradation of fats and oils ranged from 69% to 92%. Therefore, considering the efficiency of the elimination of fats and oils, the results indicated that physical treatment should be replaced with biological treatment so that the CO2 generated by the biodegradation will be incorporated into the carbon cycle and the mass of fats and oils in landfills will be reduced.