Anaerobic Wastewater Treatment Plants Research Articles

Performance of wastewater treatment plants in emission of greenhouse gases

The present work has estimated greenhouse gas emissions in aerobic and anaerobic Wastewater Treatment Plants in Southern Italy. Greenhouse gases emissions from each treatment unit were calculated based on emission factors related to Chemical Oxygen Demand removal for biogenic CO2 and CH4 assessment and on Nitrogen removal for N2O. N2O, biogenic CO2, and CH4 emissions vary for aerobic and anaerobic-based WWTPs respectively from 73 kgCO2eq/PE*y for anaerobic plants to 91 kgCO2eq/PE*y for aerobic plants. In aerobic and anaerobic digestion systems WWTPs the contributions to CO2eq total emissions from N2O, CH4, biogenic CO2, and fossil CO2 are 30 %–33 %, 20 %–29 %, 22 %–25 %, and 26 %–16 %, respectively. N2O emissions from biological processes were found the most contributing sources of greenhouse gases while in the physical processes higher contribution is indirect carbon dioxide related to energy consumption. Compensatory measures are reported to reduce greenhouse gases emissions.

Biological degradation of 2,4,6-trichlorophenol using anaerobic sequencing batch reactor equipped with a rotating biological bed

2, 4, 6-Triclorphenol is a halogenated aromatic compound with toxic, volatile, and odor properties. The anaerobic processes are superior to aerobic processes due to better dehalogenation of 2, 4, 6-Triclorphenol and easier control of releasing this toxic and odorous chemical compound into the air. However, anaerobic processes have lower reaction rates than aerobic processes. In this study, a rotating biological bed was used in an anaerobic sequencing batch reactor to increase the rate of anaerobic reactions. The anaerobic sequencing batch reactor equipped with a rotating biological bed removed more than 99% of the 2, 4, 6-Triclorphenol, 96% of total phenolic compounds, and more than 86% of its chemical oxidation demand in 2, 4, 6-Triclorphenol concentration of 430 mg/L and hydraulic retention time of 12 h. With the biological degradation of the 2, 4, 6-Triclorphenol by an anaerobic sequencing batch reactor Equipped with a rotating biological bed, more than 92% of the chlorine atoms in the structure of this compound were released into the effluent. Therefore, almost complete dehalogenation of 2, 4, 6-Triclorphenol is performed by this process. By removing the rotating biological bed from the anaerobic sequencing batch reactor equipped with a rotating biological bed, the bioreactor efficiency declined rapidly and progressed to failure. The role of rotating biological bed in dehalogenation (32%), biological degradation (10%), and mineralization (83%) of 2, 4, 6-Triclorphenol are very important. Therefore, a rotating biological bed has a significant role in promoting an anaerobic sequencing batch reactor. The anaerobic sequencing batch reactor equipped with a rotating biological bed can remove higher concentrations of 2, 4, 6-Triclorphenol at a lower hydraulic retention time than previously studied processes. Thus, the rotating biological bed can be an appropriate option for promoting anaerobic wastewater treatment plants that receive wastewater containing volatile, toxic, and complex organic compounds.

DNN model development of biogas production from an anaerobic wastewater treatment plant using Bayesian hyperparameter optimization

Deep neural networks have been regarded as accurate models to predict complex fermentation processes due to their capacity to learn from a high number of data sets via artificial intelligence. To enhance the performance of these models the main challenge is to select the appropriate hyperparameters, such as neural network architecture (number of hidden layers and hidden units), activation function, optimizer, learning rate, and others.This study aims to use a hybrid Bayesian optimization with tree-structured Parzen estimator (BO-TPE) to predict biogas production from real wastewater treatment plant data using deep neural network machine learning (DNN) with optimized hyperparameters. Due to the high number of missing sample measurement records, the data preprocessing process has been performed in three sequential steps: the first step is to remove columns with a high percentage of missing values. The second step concerns removing rows with a high number of missing values. The remaining missing values in the dataset were removed in the third step using the dropna function from Pandas' library. Then, on the remaining data, three normalization techniques (MinMaxScaler, RobustScaler, and StandardScaler) were used for 16 relevant features of the anaerobic digestion process (AD) and compared with Non-Normalized data. The RobustScaler technique demonstrated good prediction capabilities of biogas volume produced. The maximum predicted volume was 2236.105 Nm3/d, with the coefficient of determination (R2), the mean absolute error (MAE), and the root mean square error (RMSE) values of 0.712, 164.610, and 223.429, respectively. This value remains slightly higher than the actual biogas volume produced in the wastewater treatment plant, which was 2131 Nm3/d. Adopting StandardScaler, MinMaxScaler, and Non-Normalized data provided statistical performance indicator values of (0.690; 170.518; 231.519), (0.679; 180.575; 235.648), and (0.647; 183.403; 247.203), respectively. These findings offer an autonomous strategy to monitor the effective operational variables of a large-scale digester, ensuring the stability of the complex fermentation process as well as the long-term sustainability and economic viability of the renewable energy approach in the sector of waste treatment.

Evaluation of greenhouse gas emissions from aerobic and anaerobic wastewater treatment plants in Southeast of Italy

An evaluation of the operative functioning data of 183 Wastewater Treatment Plants (WWTPs) in Apulia (Southeast of Italy) has been carried out aimed to assess their Green House Gases (GHGs) emissions and the level for which the use of anaerobic sludge treatment should be more convenient in terms of electricity consumption and of GHGs emissions. Out of the 183 studies WWTPs, 140 are practicing aerobic digestion of sludge, while the remaining 43 are practicing anaerobic digestion of sludge. WWTPs in Apulia are serving about 4,81 million PE (Population Equivalent), yielding approximately 600,000-ton equivalent CO2 per annum. The production of GHGs emissions has been estimated by evaluating the contribution of CO2 deriving from: a) electric energy consumption (fossil CO2), b) biogenic CO2, c) N2O and d) CH4 emissions. The present study investigates a number of technical measures for upgrading the existing WWTPs, so to reduce GHGs emissions through the amelioration of CH4 production and capture in the anaerobic step, and through reducing the production of biogenic N2O and CO2 emissions in the aerated basin. The methodology employees artificial intelligence-based control for upgrading the aerobic oxidation of the organic carbon and the nitrification-denitrification steps. As a result, GHGs emissions are expected to be reduced by approximately: 71% for CH4, 57% for N2O, 20% for biogenic CO2 and 15% for fossil derived CO2.

Techno-economic assessment of microbial electrohydrogenesis integration to the fruit processing industry for hydrogen production

A hypothetical facility connected to a fruit processing plant is created to investigate the techno-economic potential of H2 production from residues and wastewater via electrohydrogenesis in a microbial electrolysis cell (MEC), using mixed microbial consortium obtained from the anaerobic wastewater treatment plant. Thermal pretreatment converts cellulose in the substrate into glucose, and deactivates methanogens present in the consortium. A Rhinohide membrane separates the cathode chamber from the anode chamber of the MEC, which requires an external power supply of 0.6 V. In this study, we determine an economically optimal utilization option for H2 and the by-product CO2 by investigating 6 scenarios. Of the 6 scenarios, the option involving the combustion of H2 in a gas engine to produce electricity and CO2 sale is the most financially feasible. Several economic analyses were performed to identify the cost drivers of the H2 production in the economically optimal scenario. Depending on the electricity cost and CO2 selling price, the financial feasibility of electrohydrogenesis-based H2 production process can be further improved.

Modeling biogas production from anaerobic wastewater treatment plants using radial basis function networks and differential evolution

This study presents a new method for modeling biogas production obtained from anaerobic digestion treatment plants with increased accuracy. The method is based on artificial neural networks (ANNs) and more specifically on the efficient architecture of radial basis function (RBF) networks. A novel RBF training scheme is proposed, based on the non-symmetric fuzzy means (NSFM) algorithm, which has been shown to offer increased accuracy compared to other ANN methods, but cannot handle efficiently a large number of input variables. As this is the case in biogas production modeling, the algorithm is enhanced with an optimizer based on differential evolution (DE), which helps to properly tune the algorithm, ultimately boosting the accuracy of the produced models. The proposed approach is applied for modeling the biogas production on a real world, full-scale operational wastewater treatment plant. A comparison study shows the superiority of the proposed model, compared to different machine learning approaches.

Energy consumption in anaerobic and aerobic based wastewater treatment plants in Italy

Abstract The aim of this study is to carry out an experimental investigation on electricity consumption in wastewater treatment plants in Italy based on aerobic and anaerobic digestion wastewater treatment plants (WWTP). The data refer to plants managed by two major water resources management companies in Italy, Hera and Acquedotto Pugliese (AQP). The survey makes use of statistical tools for data analysis of 202 urban wastewater treatment plants. In order to extend the reliability of the survey, electricity consumption data were analysed through three specific energy demand indicators: kWh/m3, kWh/PE•year, kWh/kgCODremoved referred to each plant. The results show that anaerobic systems are advantageous in terms of electricity consumption per m3 as they achieve more than 50% saving with values ranging from 1.02 kWh/m3 for aerobic plants, instead of 0.43 kWh/m3 for the anaerobic ones. Differences have been found in terms of anaerobic digestion efficiency between the data concerning the plants in northern Italy – Hera Company with an average of 0.33 kWh/m3- and those in Apulia – AQP company with an average of 0.53 kWh/m3. Aerobic systems showed more energy consumption also for HERA-managed WWTP. If anaerobic digestion were implemented on all the AQP WWTP, energy savings should be of approximately 16% and approximately 42% if related to HERA anaerobic-based WWTP average performance.

Occurrence and removal of micropollutants in full-scale aerobic, anaerobic and facultative wastewater treatment plants in Brazil

This study aims to evaluate micropollutant occurrence and removal in a low-middle income country (LMIC) by investigating the occurrence of 28 chemicals from different classes (triclosan, 15 polycyclic aromatic hydrocarbons (PAHs), 4 estrogens and 8 polybrominated diphenyl ether (PBDE) congeners) in three technologically diverse full-scale Brazilian wastewater treatment plants (WWTPs). These chemicals were detected at concentrations similar to those reported in other low-middle income countries (LMICs) and high-income countries (HICs) (0.1–49 μg/L) indicating their widespread use globally and the need for more studies in LMICs that are typically characterized by relatively inadequate wastewater treatment barriers. Among the three different WWTPs investigated for removal of these chemicals, the least energy intensive system, waste stabilization ponds (WSPs), was the most effective (95–99%) compared to the activated sludge (79–94%), and Up-flow sludge blanket reactor (UASB) with trickling filters system (89–95%). These results highlight the potential of WSPs for micropollutant removal-especially in warm climates. However, the effluent from all three WWTP could pose a risk to aquatic organisms when discharged into the receiving waters as the effluent concentrations of triclosan, some estrogens, PAHs and BDE 209 were above European environmental quality standards (EQS) or predicted no effect concentration (PNEC values), indicating that receiving water bodies could benefit from further treatment. In combination, these results help to further understand prevailing concentrations of micropollutants globally and fate in current wastewater treatment systems.

Perceptions and Potential Reuse of the Effluent from Anaerobic Wastewater Treatment Plant (WWTP) Treated Tofu Wastewater

Perceptions and Potential Reuse of the Effluent from Anaerobic Wastewater Treatment Plant (WWTP) Treated Tofu Wastewater

Anaerobic-Based Water Resources Recovery Facilities: A Review

The concept of water resources recovery facilities (WRRFs) has gained more attention as a more sustainable substitute for the conventional activated sludge-based wastewater treatment plant (CAS-WWTPs). Anaerobic treatment is advantageous due to its lower energy use, limited sludge production, and higher recovery of the soluble chemical oxygen demand (sCOD) from the received wastewater. In this article, a critical review of the proposed scheme for the anaerobic-based WRRF (An-WRRFs) is presented which is preceded with discussion of CAS-WWTPs limitations. In addition, the evolution of anaerobic treatment from being viewed as wastewater treatment plant (WWTP) to WRRF is demonstrated. It is attained that, even though anaerobic WWTPs (An-WWTPs) have simple and low energy mainline and very limited sludge handling process, its limited removal and recovery capacity have been widely reported, especially in cold weather. On the other hand, in the An-WRRF, higher energy expenditures are employed by using membranes, dissolved methane recovery unit, and primary treatment (extra sludge handling). Yet, energy recovery in the form of biogas is notably increased, as well as the removal efficiency under moderate residence times. The three key challenges to be overcome are the low value of biogas, reducing the energy use associated with membranes, and maintaining high performance in full-scale, especially in cold weather.

Methanogens Diversity during Anaerobic Sewage Sludge Stabilization and the Effect of Temperature

Anaerobic sludge stabilization is a commonly used technology. Most fermenters are operated at a mesophilic temperature regime. Modern trends in waste management aim to minimize waste generation. One of the strategies can be achieved by anaerobically stabilizing the sludge by raising the temperature. Higher temperatures will allow faster decomposition of organic matter, shortening the retention time, and increasing biogas production. This work is focused on the description of changes in the community of methanogenic microorganisms at different temperatures during the sludge stabilization. At higher temperatures, biogas contained a higher percentage of methane, however, there was an undesirable accumulation of ammonia in the fermenter. Representatives of the hydrogenotrophic genus Methanoliea were described at all temperatures tested. At temperatures up to 50 °C, a significant proportion of methanogens were also formed by acetoclastic representatives of Methanosaeta sp. and acetoclastic representatives of the order Methanosarcinales. The composition of methanogens in the fermenter significantly changed at 60 °C when typically thermophilic species, like Methanothermobacter marburgensis, appeared. A decrease in the diversity of methanogens was observed, and typical hydrogenotrophic methanogenic archaea isolated from fermenters of biogas plants and anaerobic wastewater treatment plants represented by genus Methanoculleus were no longer present.

Diverse Microbial Community Profiles of Propionate-Degrading Cultures Derived from Different Sludge Sources of Anaerobic Wastewater Treatment Plants

Anaerobic digestion (AD) has been used for wastewater treatment and production of renewable energy or biogas. Propionate accumulation is one of the important problems leading to an unstable system and low methane production. Revealing propionate-degrading microbiome is necessary to gain a better knowledge for alleviation of the problem. Herein, we systematically investigated the propionate-degrading cultures enriched from various anaerobic sludge sources of agro-industrial wastewater treatment plants using 16S rRNA gene sequencing. Different microbial profiles were shown even though the methanogenic activities of all cultures were similar. Interestingly, non-classical propionate-degrading key players Smithella, Syntrophomonas, and Methanosaeta were observed as common prevalent taxa in our enriched cultures. Moreover, different hydrogenotrophic methanogens were found specifically to the different sludge sources. The enriched culture of high salinity sludge showed a distinct microbial profile compared to the others, containing mainly Thermovirga, Anaerolinaceae, Methanosaeta, Syntrophobactor, and Methanospirillum. Our microbiome analysis revealed different propionate-degrading community profiles via mainly the Smithella pathway and offers inside information for microbiome manipulation in AD systems to increase biogas production corresponding to their specific microbial communities.

Long-term performance of denitrifying anaerobic methane oxidation under stepwise cooling and ambient temperature conditions

Nitrate-dependent anaerobic methane oxidation (N-DAMO), a bioprocess that couples the oxidation of green gas and the removal of nitrogen oxides in a microbial group, has gained much attention as a potential economical method of biological removal of nitrates and methane from wastewater. Low-temperature (20 °C) operation of N-DAMO would be beneficial to utilize the methane dissolved in the effluent and thus decrease the cost of maintaining the bioreactor temperature in wastewater treatment. Here, the long-term (>350 days) operational activities of N-DAMO were evaluated to assess the performance of N-DAMO from stepwise cooling (30–20 °C) to ambient temperatures (13–38 °C). Under stepwise cooling conditions, the activity of the N-DAMO community was first inhibited and then rapidly adjusted. Notably, a similar N-DAMO activity was observed at 30 °C and 20 °C. Under ambient temperature conditions, the highest nitrate removal rate observed at the beginning of the test was 7.14 mg-N/L/d, which was 5.3 times higher than that recorded at the end of the test. This indicates that the long-term temperature fluctuation irreversibly inhibited N-DAMO activity. 16S rRNA gene sequencing analyses found that the functional archaea were ANME-2D, which has been deemed as the dominant culture in the N-DAMO process. The abundance of ANME-2D on the last day at stepwise cooling temperature conditions was much higher than on day 0, but disappeared after a long period of operation at ambient temperature. It was assumed that N-DAMO would stabilize at stepwise cooling temperature conditions, but not at ambient temperature. Our findings could offer a promising technology for anaerobic wastewater treatment plants (WWTPs) in temperate and warm climate zones.

The effect of hydraulic retention time on thermophilic dark fermentative biohydrogen production in the continuously operated packed bed bioreactor

The main objective of the study is to investigate the effect of hydraulic retention times on continuous dark fermentative biohydrogen production in an up-flow packed bed reactor (UPBR) containing a novel microorganism immobilization material namely polyester fiber beads. The hydrogen producing dark fermentative microorganisms were obtained by heat-pretreatment of anaerobic sludge from the acidogenic phase of an anaerobic wastewater treatment plant. Glucose was the sole carbon source and the initial concentration was 15 ± 1 g/L throughout the continuous feeding. UPBR was operated under the thermophilic condition at T = 48 ± 2 °C and at varying HRTs between 2 h and 6 h. The hydrogen productivity of continuously operated UPBR increased with increasing HRT. Hydrogen production volume varied between 4331 and 6624 ml/d, volumetric hydrogen production rates (VHPR) were obtained as 3.09–4.73 L H2/L day, and hydrogen production yields (HY) were 0.49 mol/mol glucose-0.89 mol/mol glucose depending on HRT. Maximum daily hydrogen volume (6624 ml/d), the yield (0.89 mol/mol glucose) and VHPR (4.73 L H2/L day) were obtained at HRT = 6 h. The production rate and the yield decreased with increasing organic loading rate due to substrate inhibition.

Determination of linear and cyclic volatile methyl siloxanes in biogas and biomethane by solid-phase microextraction and gas chromatography-mass spectrometry

A new method based on solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for the analysis of seven linear (L2 – L5) and cyclic (D3 – D5) volatile methyl siloxanes (VMS) in biogas and biomethane, directly collected into Tedlar® bags (Tedlar SPME) from anaerobic digesters and wastewater treatment plants. The method was employed to monitor VMS content in biomethane produced by biogas upgrading with a pilot-plant membrane unit and provided adequate limits of quantification (< 0.05 mg m−3) to detect trace siloxane impurities. Tedlar SPME was validated against a standard procedure based on indirect sampling of gas streams with sorbent tubes followed by solvent extraction and GC-MS. Method precision (RSD) on total and individual VMS concentrations was lower than 10%, while RSD values of the standard procedure were higher than 20%. Tedlar SPME suitably revealed high VMS levels, expressed as total volatile silicon (> 1 mgSim−3), in wastewater biogas and provided a more efficient sampling of heavier VMS in comparison to the sorbent tubes method. At low values (< 0.1 mgSim−3) typical of wood waste biogas and biomethane, no statistically significant differences were observed between the two methods. Overall, Tedlar SPME simplified the analytical procedure by reducing the procedural steps, avoiding the use of solvents and demonstrated its applicability for testing the quality of biomethane as advanced biofuel.

Co digestion for biogas production from tapioca industrial wastewater and septage

In this study, a combination of substrate rich carbon with substrate rich nitrogen was carried out. The experiments were conducted in batches process by varying the C/N ratio and types of anaerobic microbial sludge of the cow rumen, anaerobic microbial sludgefrom wastewater treatment plant (WWTP) of septage and anaerobic sludge from WWTP of tapioca industry. Practically in the range of C/N ratio 20-30 didn’t give a significant effect on the biogas production.The C/N 30 ratio provides the most biogas production rate, while the microbe derived from the cow rumen gives the most biogas production rate.Adaptation phase occurred up to 11th days, growth phase occurred lasted until day 24st, stationary phase occurred in the range of day 24th-31st and death phase occurred after day 31st. Biogas yield (by cow rumen) is 1,127 liters per kg of COD removed or 161 liters per kg of COD per day.

CO Digestion for Biogas Production from Tapioca Industrial Wastewater and Septage

In this study, a combination of substrate rich carbon with substrate rich nitrogen was carried out. The experiments were conducted in batches process by varying the C/N ratio and types of anaerobic microbial sludge of the cow rumen, anaerobic microbial sludgefrom wastewater treatment plant (WWTP) of septage and anaerobic sludge from WWTP of tapioca industry. Practically in the range of C/N ratio 20-30 didn’t give a significant effect on the biogas production.The C/N 30 ratio provides the most biogas production rate, while the microbe derived from the cow rumen gives the most biogas production rate.Adaptation phase occurred up to 11th days, growth phase occurred lasted until day 24st, stationary phase occurred in the range of day 24th-31st and death phase occurred after day 31st. Biogas yield (by cow rumen) is 1,127 liters per kg of COD removed or 161 liters per kg of COD per day.

THE IMPROVEMENT OF ANAEROBIC WASTEWATER TREATMENT WITH STRUCTURED MEDIA GROWTH SYSTEM

The anaerobic domestic wastewater treatment plant at communal scaleare seen not be sustainable and the process s to be improve by anaerobic and aerobic process - structured media growth system, in regard with still high water source quality degradation and water reuse development.This paper aims to research the improvement of communal wastewater treatment system through anaerobic –aerobic of structured media growth system which had applied in some urban areas. The treatment system applied the anaerobic baffled reactor (ABR),submerged media growth system and rotating biological contactor system has low area requirement and has to concern optimization energy. The treatment system applied the hybrid upflow anaerobic sludge blanket - submerged media growth system and hybrid sub surface of constructed wetland has low cost operation and maintanence Both of the system have many advantages and could consider as improvement of the anaerobic communal wastewater treatment plant. The evaluation of performance these systems show the treated water an meet effluent standard and can be reused as non potable source in urban areas. Article DOI: https://dx.doi.org/10.20319/mijst.2017.32.533545 This work is licensed under the Creative Commons Attribution-Non-commercial 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc/4.0/ or send a letter to Creative Commons, PO Box 1866, Mountain View, CA 94042, USA.

Scaling-up of a zero valent iron packed anaerobic reactor for textile dye wastewater treatment: a potential technology for on-site upgrading and rebuilding of traditional anaerobic wastewater treatment plant.

Anaerobic digestion (AD) is a cost-effective technology for the treatment of textile dye wastewater with clear environmental benefits. However, the need to improve process feasibility of high treatment efficiency as well as to shorten hydraulic retention time has raised interest on several intensification techniques. Zero valent iron (ZVI) packed anaerobic digesters have the potential to become an on-site upgrading wastewater treatment technology through building a ZVI bed in a traditional AD plant. However, the experiences and knowledge of scale-up are limited. In this study, a pilot-scale ZVI packed upflow anaerobic sludge bed (ZVI-UASB) was built up and operated for actual dye wastewater treatment in a textile dye industrial park. Results showed that the treatment performance of this digester is higher than that of a traditional AD plant in terms of chemical oxygen demand (COD) removal and color removal. During 90 days of operation, the average COD removal and color removal in ZVI-UASB was maintained at around 19% and 40%, respectively, while it was only 10% and 20%, respectively, in the traditional AD plant.

Economic and CO2 avoided emissions analysis of WWTP biogas recovery and its use in a small power plant in Brazil

An anaerobic wastewater treatment generates at the end of its process an anaerobic biomass, also known as anaerobic sludge, and a major sub product, the biogas, composed mainly by methane (CH4) and carbonic gas (CO2). The biogas needs to be collected in order to be flared or used in another process, especially because it cannot be released directly into the atmosphere due to methane gas and its high global warming potential. Nevertheless, when this gas is burnt, an energy vector for micro generation is discarded. In the present work was designed a thermal power plant using the biogas produced in an anaerobic wastewater treatment plant (WWTP) through an implementation methodology that considers the population growth according to a southeast ordinary Brazilian city. The energy production potential, avoided CO2 emissions due to the biogas burnt and the possibility of using this energy to supply the WWTP’s internal demand consumption were analyzed, as well as the project’s economic viability and the arising benefits from carbon credits, calculated in three scenarios. The data of calculus were based on the Brazilian sales tariffs obtained from Brazilian National Electric Energy Agency – ANEEL, where: i) T1=64.9[US$/MWh] (average tariff on Brazilian energy auction A-5); ii) T2=86.47[US$/MWh] (average tariff for thermal power plants in the same auction), and iii) the third scenario, in which the energy produced would be consumed by the WWTP’s internal demand. The economic viability was only achieved in second and third scenarios, being intensified in the scenario that WWTP’s internal demand is supplied using the energy generated in the biogas plant.