Aeration Energy Consumption Research Articles

Enhancement in the partial nitrification of wastewater sludge via low-intensity ultrasound: Effects on rapid start-up and temperature resilience

The partial nitrification process can reduce the aeration energy consumption in bioreactors by 25%. Low-intensity ultrasound (0.25 W·mL−1) was applied during the partial nitrification process to evaluate its effects on start-up and temperature resilience. Ultrasound application led to rapid start-up of the partial nitrification process (within 18 d) with a nitrite accumulation ratio of above 80% at 18 °C. Moreover, when the temperature was increased to 28 °C, the partial nitrification process was effectively maintained with a nitrite accumulation ratio of above 80%. Ultrasonic treatment for a long duration had a positive effect on ammonia oxidizing bacteria of the genus Nitrososphaera, whereas the population of nitrite oxidizing bacteria, Nitrospira, decreased. The temperature resilience of Nitrososphaera was also enhanced. These findings indicate that ultrasound induces rapid start-up of the partial nitrification process and enhances the temperature resilience of Nitrososphaera.

Towards advanced nitrogen removal and optimal energy recovery from leachate: A critical review of anammox-based processes

Anaerobic ammonium oxidation (anammox), a promising technology for bio-nitrogen removal, has been a research hotspot in the field of leachate treatment. However, the inhibitory effect of organic matter and high-strength nitrogen on anammox bacteria and the limitation of the theoretical total nitrogen removal efficiency of anammox (<90%) are obstacles to its wider application. The mechanisms of the inhibitory effects of organic matter, ammonium, and nitrite on anammox bacteria, and the corresponding control strategies are summaries. The anammox-based processes developed for advanced nitrogen removal (ANR) in recent years, including anammox-based heterotrophic denitrification, anammox-based partial denitrification, and anammox-based constructed wetlands are systematically discussed. An integrated anaerobic system of simultaneous denitrification and methanogenesis (anaerobic membrane bioreactor) + anammox-based processes was proposed for the ANR and optimal energy recovery from leachate. This process showed a 16% increase in biogas yield, a 64% decrease in aeration energy consumption, and the decrease in the external carbon source is expected to be 100% compared to conventional leachate treatment processes such as anoxic/oxic-membrane bioreactors. Finally, a few research perspectives on leachate treatment using anammox-based processes are reviewed. The conclusions drawn from the studies presented herein provide guidance for further research and engineering applications in the field of leachate treatment.HighlightsAnMBR pretreatment is proposed for energy recovery and elimination of inhibition of anammox bacteria by organics.Anammox-based heterotrophic denitrification, partial denitrification, and anammox-based constructed wetlands are discussed for ANR.SDM is proposed for ANR from leachate via anammox effluent recirculation.An SDM(AnMBR)+anammox based process is proposed for energy saving and recovery.

Aeration Process in Bioreactors as the Main Energy Consumer in a Wastewater Treatment Plant. Review of Solutions and Methods of Process Optimization

Due to the key role of the biological decomposition process of organic compounds in wastewater treatment, a very important thing is appropriate aeration of activated sludge, because microorganisms have to be supplied with an appropriate amount of oxygen. Aeration is one of the most energy-consuming processes in the conventional activated sludge systems of wastewater treatment technology (may consume from 50% to 90% of electricity used by a plant), which makes it the most cost-generating process incurred by treatment plants. The paper presents the construction of aeration systems, their classification as well as parameters and factors that significantly affect the aeration process e.g., oxygen transfer efficiency, diffuser fouling, methods of dealing with diffuser fouling, diffuser selection. Additionally, there are briefly presented “smart control” systems in wastewater treatment and effect of application control strategy based on Supervisory Control and Data Acquisition system connected with the decrease in the energy consumption for aeration of bioreactors with activated sludge. It is noted that before the process is optimized, the system should be equipped with suitable metering devices. Only when relevant data is available, the improvements can be carried out. However, it’s important, that the operator should regularly maintain good condition and high efficiency of diffusers.

How does greywater separation impact the operation of conventional wastewater treatment plants?

Source separation has thus far been addressed mainly within the context of decentralization in new development areas; centralized approaches for resource-oriented sanitation remained, however, largely disregarded. By means of inhabitant-specific load and volume flow balances, based on typical reference values for municipal wastewater in Germany, a stepwise transition towards on-site greywater recycling was investigated for a model wastewater treatment plant (WWTP). Up to 17% transition (separation of greywater from 17% of the total inhabitants), greywater separation was proven to benefit plant operation by reducing energy consumption for aeration. From 17% transition onwards, however, unfavorable carbon to nitrogen ratios (C/N) were reported, as less biodegradable carbon reaches denitrification, thus shifting C/N ratios negatively. Therefore, nitrogen recovery/removal from N-rich sludge sidestreams would be required. At 35% transition, a 50% N recovery from sludge liquor was proven to be sufficient in order to ensure full denitrification; combined with greywater separation, nutrient recovery yielded 14% reduction in power demand for aeration (on the actual state). Additionally, extensive mainstream process changeovers could be avoided by separating N-rich urine alongside greywater from the main wastewater stream. Urine separation was proven to maintain denitrification stability as well as reduce power demand for aeration. The calculations show that, under consideration of specific boundary conditions, existing WWTP can be successfully integrated in transition concepts for resource-oriented sanitation.

Ammonia-based aeration control with optimal SRT control: improved performance and lower energy consumption.

Ammonia-based aeration control (ABAC) is a cascade control concept for controlling total ammonia nitrogen (NHx-N) in the activated sludge process. Its main goals are to tailor the aeration intensity to the NHx-N loading and to maintain consistent nitrification, to meet effluent limits but minimize energy consumption. One limitation to ABAC is that the solids retention time (SRT) control strategy used at a water resource recovery facility (WRRF) may not be consistent with the goals of ABAC. ABAC-SRT control is a strategy for aligning the goals of ammonia-based aeration control and SRT control. A supervisory controller is used to ensure that the SRT is always optimal for ABAC. The methodology has the potential to reduce aeration energy consumption by over 30% as compared to traditional dissolved oxygen (DO) control. Practical implementation aspects are highlighted for implementation at full scale, such as proper selection of the set point for the supervisory controller, proper calculation of the rate of change in sludge inventory, using a mixed liquor suspended solids (MLSS) controller, and tuning of the controllers. In conclusion, ABAC-SRT is a promising approach for coordinated control of SRT, total ammonia nitrogen, and dissolved oxygen in the activated sludge process that balances both treatment performance and energy savings.

Effects of Cotton Seed Powder as the Seed Medium Nitrogen Source on the Morphology and Pneumocandin B0 Yield of Glarea lozoyensis.

Pneumocandin B0 is an important antifungal drug precursor produced by filamentous fungus Glarea lozoyensis. The high broth viscosity of cultures of this organism results in lower oxygen solubility and higher energy consumption for agitation and aeration, which mostly caused by the morphologies of filamentous fungi in submerged culture. In this study, the effects of different seed medium nitrogen sources on morphology and fermentation behavior of G. lozoyensis were investigated, and cotton seed powder resulted in small, compact pellets. Moreover, pneumocandin B0 yield in Erlenmeyer flasks were increased by 22.9%. Furthermore, pneumocandin B0 yield in a 50-L fermenter reached 2,100 mg/L and the dissolved oxygen maintained above 30%. Additionally, activities of phosphofructokinase (PFK), isocitrate dehydrogenase (ICDH), glucose 6-phosphate dehydrogenase (G6PDH), and malic enzyme (ME) were increased by 87.5, 50, 41.6, and 10.7%, respectively. This study demonstrates the feasibility and advantages of using cotton seed powder for controlling the fungal morphology and improving the product yield in pneumocandin fermentations.

Оценка эффективности металлических силосов по удельным расходам электроэнергии на вентилирование зерна различных культур

Оценка эффективности металлических силосов по удельным расходам электроэнергии на вентилирование зерна различных культур

Dynamic air supply models add realism to the evaluation of control strategies in water resource recovery facilities.

This paper introduces the application of a fully dynamic air distribution model integrated with a biokinetic process model and a detailed process control model. By using a fully dynamic air distribution model, it is possible to understand the relationships between aeration equipment, control algorithms, process performance, and energy consumption, thus leading to a significantly more realistic prediction of water resource recovery facility (WRRF) performance. Consequently, this leads to an improved design of aeration control strategies and equipment. A model-based audit has been performed for the Girona WRRF with the goal of providing a more objective evaluation of energy reduction strategies. Currently, the Girona plant uses dissolved oxygen control and has been manually optimised for energy consumption. Results from a detailed integrated model show that the implementation of an ammonia-based aeration controller, a redistribution of the diffusers, and the installation of a smaller blower lead to energy savings between 12 and 21%, depending on wastewater temperature. The model supported the development of control strategies that counter the effects of current equipment limitations, such as tapered diffuser distribution, or over-sized blowers. The latter causes an intermittent aeration pattern with blowers switching on and off, increasing wear of the equipment.

Cost minimization in a full-scale conventional wastewater treatment plant: associated costs of biological energy consumption versus sludge production.

Energy consumption and sludge production minimization represent rising challenges for wastewater treatment plants (WWTPs). The goal of this study is to investigate how energy is consumed throughout the whole plant and how operating conditions affect this energy demand. A WWTP based on the activated sludge process was selected as a case study. Simulations were performed using a pre-compiled model implemented in GPS-X simulation software. Model validation was carried out by comparing experimental and modeling data of the dynamic behavior of the mixed liquor suspended solids (MLSS) concentration and nitrogen compounds concentration, energy consumption for aeration, mixing and sludge treatment and annual sludge production over a three year exercise. In this plant, the energy required for bioreactor aeration was calculated at approximately 44% of the total energy demand. A cost optimization strategy was applied by varying the MLSS concentrations (from 1 to 8 gTSS/L) while recording energy consumption, sludge production and effluent quality. An increase of MLSS led to an increase of the oxygen requirement for biomass aeration, but it also reduced total sludge production. Results permit identification of a key MLSS concentration allowing identification of the best compromise between levels of treatment required, biological energy demand and sludge production while minimizing the overall costs.

Contribution to optimize decision parameters in activated-sludge process using ANFIS model

The monitoring of activated sludge processes is difficult because of their slow dynamics, the complexity of their behavior. To obtain the desired level of performance in an activated sludge system, a proper balance must be maintained between aeration (energy consumption) and the quantity of sludge recirculation. The objective of this study is to determine the necessary amount of recirculated sludge in activated sludge process in the aim to reduce the energy consumption with respect of environmental standards. To achieving this objective, a comparative study between three models was performed. In order to reduce the complexity of activated-sludge process, the first is a linear model based on principal component analysis method (PCA), the second is an Adaptive Neural Fuzzy Inference System model (ANFIS), while the third is based on coupling of those two approaches. The best values of validation criterion obtained with the last method show the high performance of the hybrid model proposed…

Strategies for achieving energy neutrality in biological nutrient removal systems - a case study of the Slupsk WWTP (northern Poland).

The paper presents a model-based evaluation of technological upgrades on the energy and cost balance in a large biological nutrient removal (BNR) wastewater treatment plant (WWTP) in the city of Slupsk (northern Poland). The proposed upgrades include chemically enhanced primary sludge removal and reduction of the nitrogen load in the deammonification process employed for reject water treatment. Simulations enabled to estimate the increased biogas generation and decreased energy consumption for aeration. The proposed upgrades may lead the studied WWTP from the energy deficit to energy neutrality and positive cost balance, while still maintaining the required effluent standards for nitrogen. The operating cost balance depends on the type of applied coagulants/flocculants and specific costs of electric energy. The choice of the coagulant/flocculent was found as the main factor determining a positive cost balance.

Developing of effective treatment technology of the phenolic wastewater

It is found that a high degree of purification from emulsified coal tar is achieved in the phenolic wastewater treatment using 88 mg/dm 3 of sodium bentonite with the addition of 8 mg/dm 3 of cationic flocculant in conditions the closest to industrial. This innovative method of phenolic wastewater treatment is cost­effective because of the low cost of bentonite. It is shown that the deposit formed during the wastewater treatment with bentonite floats to the liquid surface and can be separated by a scraper device for further utilization in construction. The process of biological treatment of phenolic wastewater in the combined aerator­clarifier unit is shown. It is determined that the optimum time for efficient phenol extraction from wastewater is 6 hours. It is experimentally proved that the use of this unit makes the biological treatment process 4 times faster giving significant economic benefits by reducing energy consumption for aeration. The flow diagram of complex wastewater purification from coal tar and phenol is developed. The use of it at coke and chemical plants will significantly increase the treatment efficiency and product profitability.

Analysis of greenhouse gas emissions and the energy balance in a model municipal wastewater treatment plant

Municipal wastewater treatment plants (WWTPs) with multi-stage activated sludge technology generate significant amounts of greenhouse gases (GHG) in the form of nitrous oxide N2O, methane (CH4) and carbon dioxide (CO2). Although the exact magnitudes of the specific emissions are difficult to estimate, they strongly affect the energy balance of a plant. This article presents a simulation study carried out on a model municipal WWTP. The research aimed to analyse the potential for the reduction in GHG emissions through the operational optimization of some core operational parameters and its effects on the plant’s energy balance. The results showed that the combined effect of optimization of the dissolved oxygen concentration in the aerobic zone, the solids retention time and the ratio of chemical oxygen demand to total nitrogen (COD:TN) in the influent may lead to a reduction in the N2O emissions by 1,103 kg CO2 eq/d and also a slight reduction in the CO2 and CH4 emissions, by 256 and 87 kg CO2 eq/d, respectively. This was coupled with an improvement in the plant’s net energy balance by 34 kW through the reduction in energy consumption for aeration of the activated sludge by 18 kW and the increased energy production from biogas by 16 kW.

A Feasibility Analysis Methodology for Decentralized Wastewater Systems – Energy‐Efficiency and Cost

Centralized wastewater treatment, widely practiced in developed areas, involves transporting wastewater from large urban areas to a large capacity plant using a single network of sewers, whereas decentralization is the concept of wastewater collection, treatment and reuse at or near its point of generation. Smaller decentralized plants can achieve extensive reclamation and wastewater management with energy-efficient reclaimed water pumping, modularized expansion and lower capital investment. We devised a methodology to preliminarily assess these alternatives using local constraints and conducted a feasibility analysis for each option. It addressed various scenarios using the pump-back energy consumption, sewer and treatment plant construction and capacity expansion cost. We demonstrated this methodology by applying it to the Hollywood vicinity (California). In this study, the decentralized configuration was more economical and energy-efficient than the centralized system. The pump-back energy consumption was about 50% of the aeration energy consumption for the centralized option.

Reducing aeration energy consumption in a large-scale membrane bioreactor: Process simulation and engineering application

Reducing the energy consumption of membrane bioreactors (MBRs) is highly important for their wider application in wastewater treatment engineering. Of particular significance is reducing aeration in aerobic tanks to reduce the overall energy consumption. This study proposed an in situ ammonia-N-based feedback control strategy for aeration in aerobic tanks; this was tested via model simulation and through a large-scale (50,000 m3/d) engineering application. A full-scale MBR model was developed based on the activated sludge model (ASM) and was calibrated to the actual MBR. The aeration control strategy took the form of a two-step cascaded proportion-integration (PI) feedback algorithm. Algorithmic parameters were optimized via model simulation. The strategy achieved real-time adjustment of aeration amounts based on feedback from effluent quality (i.e., ammonia-N). The effectiveness of the strategy was evaluated through both the model platform and the full-scale engineering application. In the former, the aeration flow rate was reduced by 15–20%. In the engineering application, the aeration flow rate was reduced by 20%, and overall specific energy consumption correspondingly reduced by 4% to 0.45 kWh/m3-effluent, using the present practice of regulating the angle of guide vanes of fixed-frequency blowers. Potential energy savings are expected to be higher for MBRs with variable-frequency blowers. This study indicated that the ammonia-N-based aeration control strategy holds promise for application in full-scale MBRs.

Full-scale implementation of an advanced control system on a biological wastewater treatment plant

The implementation of a multivariable control package for the real-time control and supervision of a biological wastewater treatment plant is reported and discussed. The goal is to improve the plant operation in terms of effluent quality and operational costs. A dynamic matrix control algorithm is put into operation for controlling the ammonia concentration at the end the biological reactor in the activated sludge process. The status of the plant instrumentation is continuously monitored by multivariate statistical technology based on moving windows principal component analysis. Results of the first six months of continuous operation show the ability of the designed predictive control in reducing the aeration energy consumption whilst keeping the ammonia concentration in the effluent within the limits.

Modeling effects of DO and SRT on activated sludge decay and production

The effect of dissolved oxygen (DO) on the endogenous decay of active heterotrophic biomass and the hydrolysis of cell debris were studied. With the inclusion of a hydrolysis process for the cell debris, mathematical models that are capable of quantifying the effects of DO and sludge retention time (SRT) on concentrations of active biomass and cell debris in activated sludge are presented. By modeling the biomass cultivated with unlimited DO, the values of endogenous decay coefficient for heterotrophic biomass, the hydrolysis constant of cell debris, and the fraction of decayed biomass that became cell debris were determined to be 0.38 d−1, 0.013 d−1, and 0.28, respectively. Results from modeling the biomass cultivated under different DO conditions suggested that the experimental low DO (∼0.2 mg/L) did not inhibit the endogenous decay of heterotrophic biomass, but significantly inhibited the hydrolysis of cell debris with a half-velocity constant value of 2.1 mg/L. Therefore, the increase in sludge production with low DO was mainly contributed by cell debris rather than the active heterotrophic biomass. Maximizing sludge production during aerobic wastewater treatment could reduce aeration energy consumption and improve biogas energy recovery potential.

Full-scale validation of an air scour control system for energy savings in membrane bioreactors

Membrane aeration represents between 35 and 50% of the operational cost of membrane bioreactors (MBR). New automatic control systems and/or module configurations have been developed for aeration optimization. In this paper, we briefly describe an innovative MBR air scour control system based on permeability evolution and present the results of a full-scale validation that lasted over a 1-year period. An average reduction in the air scour flow rate of 13% was achieved, limiting the maximum reduction to 20%. This averaged reduction corresponded to a decrease in energy consumption for membrane aeration of 14% (0.025 kWh m−3) with maximum saving rates of 22% (0.04 kWh m−3). Permeability and fouling rate evolution were not affected by the air scour control system, as very similar behavior was observed for these variables for both filtration lines throughout the entire experimental evaluation period of 1 year.

Treating low carbon/nitrogen (C/N) wastewater in simultaneous nitrification-endogenous denitrification and phosphorous removal (SNDPR) systems by strengthening anaerobic intracellular carbon storage

A novel simultaneous nitrification denitrification and phosphorous removal-sequencing batch reactor (SNDPR-SBR) enriched with PAOs (phosphorus accumulating organisms), DPAOs (denitrifying PAOs), and GAOs (glycogen accumulating organisms) at the ratio of 2:1:1 was developed to achieve the simultaneous nutrient and carbon removal treating domestic wastewater with low carbon/nitrogen ratio (≤3.5). The SNDPR system was operated for 120 days at extended anaerobic stage (3 h) and short aerobic stage at low oxygen concentration (2.5 h) with short sludge retention time (SRT) of 10.9 d and hydraulic retention time (HRT) of 14.6 h. The results showed that at the stable operating stage, the average effluent chemical oxygen demand (COD) and PO43−–P concentrations were 47.2 and 0.2 mg L−1, respectively, the total nitrogen (TN) removal efficiency was 77.7%, and the SND efficiency reached 49.3%. Extended anaerobic stage strengthened the intracellular carbon (mainly poly-β-hydroxybutyrate, PHB) storage, efficiently utilized the organic substances in wastewater, and provided sufficient carbon sources for denitrification and phosphorus uptake without external carbon addition. Short aerobic stage at low oxygen concentration (dissolved oxygen (DO): 1 ± 0.3 mg L−1) achieved a concurrence of nitrification, endogenous denitrification, denitrifying and aerobic phosphorus uptake, and saved about 65% energy consumption for aeration. Microbial community analysis demonstrated that P removal was mainly performed by aerobic PAOs while N removal was mainly carried out by denitrifying GAOs (DGAOs), even though DPAOs were also participated in both N and P removal.

Life cycle costs for the optimized production of hydrogen and biogas from microalgae

Despite the known advantages of microalgae compared with other biomass providers or fossil fuels, microalgae are predominately produced for high-value products. Economic constraints might limit the commercial energetic use of microalgae. Therefore, we identify the LCCs (life cycle costs) and economic hot spots for photoautotrophic hydrogen generation from photoautotrophically grown Chlamydomonas reinhardtii in a novel staggered PBR (photobioreactor) and the anaerobic digestion of the residual biomass to obtain biogas. The novel PBR aims at minimizing energy consumption for mixing and aeration and at optimizing the light conditions for algal growth.The LCCs per MJ amounted to 12.17 Euro for hydrogen and 0.99 Euro for biogas in 2011 for Germany. Market prices per MJ of 0.02 Euro for biogas and 0.04 Euro for hydrogen are considerably exceeded. Major contributors to operating costs, about 70% of total LCCs, are personnel and overhead costs. The investment costs consist to about 92% of those for the PBR with a share of 61% membrane costs. The choice of Madrid as another production location with higher incident solar irradiation and lower personnel costs reduces LCCs by about 40%. Projecting LCCs to 2030 with experience curves, the LCCs still exceed future market prices.