Modeling reactor-focused energy balances for multi-stage CSTR anaerobic digestion systems

2020 ◽  
Vol 12 (6) ◽  
pp. 065502
Author(s):  
M. Abdalah
Keyword(s):  
Anaerobic Digestion ◽  
Multi Stage ◽  
Energy Balances

Biological nutrient removal wastewater treatments and sewage sludge anaerobic mesophilic digestion performances

2002 ◽  
Vol 46 (10) ◽  
pp. 199-208 ◽  
Author(s):  
D. Bolzonella ◽  
L. Innocenti ◽  
F. Cecchi
Keyword(s):  
Anaerobic Digestion ◽  
Sewage Sludge ◽  
Economic Assessment ◽  
Gas Production ◽  
Anaerobic Digester ◽  
Biological Nutrient Removal ◽  
Energetic Balance ◽  
Mesophilic Digestion ◽  
The Difference ◽  
Energy Balances

The paper deals with the performances of the mesophilic anaerobic digestion treatment of sewage sludge from a full scale BNR process without primary settling (nominally 300,000 PE). A relation between the activated sludge observed yields, Yobs, and the anaerobic digester performance was preliminarily found: for values of Yobs of 0.25 kgVSS/kgCOD the anaerobic digester specific gas production showed the best performances (0.22 m3/kgVSfed). This has to be confirmed with wider future studies. It was also shown the level of sludge pre-thickening to be reached for the self-sustaining warming of the digester also in wintertime. According to the energetic balance and to a comparison with an aerobic stabilisation process, it was pointed out as when a co-generation unit for heat and energy production was introduced about 3.4 kWh/PE y of energy were produced in the anaerobic digestion process. On the other hand, 4.3 kWh/PE y were spent if an aerobic stabilisation process was applied. The economic assessment, carried out on the basis of the energy balances, showed that the anaerobic digestion is always economically advantageous if compared to aerobic stabilisation processes, also for small WWTPs. According to the energetic evaluations an environmental balance was assessed, in terms of CO2 emissions. The difference between anaerobic and aerobic processes was about 5.3 kgCO2/PE y in favour of anaerobic processes application.

scholarly journals Mass and Energy Balances of Dry Thermophilic Anaerobic Digestion Treating Swine Manure Mixed with Rice Straw

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Sheng Zhou ◽  
Jining Zhang ◽  
Guoyan Zou ◽  
Shohei Riya ◽  
Masaaki Hosomi
Keyword(s):  
Anaerobic Digestion ◽  
Rice Straw ◽  
Swine Manure ◽  
Rice Production ◽  
Methane Yield ◽  
Manure Treatment ◽  
Thermophilic Anaerobic Digestion ◽  
Forage Rice ◽  
Energy Balances ◽  
Mass And Energy Balances

To evaluate the feasibility of swine manure treatment by a proposed Dry Thermophilic Anaerobic Digestion (DT-AD) system, we evaluated the methane yield of swine manure treated using a DT-AD method with rice straw under different C/N ratios and solid retention time (SRT) and calculated the mass and energy balances when the DT-AD system is used for swine manure treatment from a model farm with 1000 pigs and the digested residue is used for forage rice production. A traditional swine manure treatment Oxidation Ditch system was used as the study control. The results suggest that methane yield using the proposed DT-AD system increased with a higher C/N ratio and shorter SRT. Correspondently, for the DT-AD system running with SRT of 80 days, the net energy yields for all treatments were negative, due to low biogas production and high heat loss of digestion tank. However, the biogas yield increased when the SRT was shortened to 40 days, and the generated energy was greater than consumed energy when C/N ratio was 20:1 and 30:1. The results suggest that with the correct optimization of C/N ratio and SRT, the proposed DT-AD system, followed by using digestate for forage rice production, can attain energy self-sufficiency.

scholarly journals A Review on Anaerobic Co-Digestion with a Focus on the Microbial Populations and the Effect of Multi-Stage Digester Configuration

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1106 ◽  
Author(s):  
Anahita Rabii ◽  
Saad Aldin ◽  
Yaser Dahman ◽  
Elsayed Elbeshbishy
Keyword(s):  
Anaerobic Digestion ◽  
Microbial Population ◽  
System Stability ◽  
Microbial Consortia ◽  
Microbial Populations ◽  
Stage Versus ◽  
Two Stage ◽  
Waste Sludge ◽  
Multi Stage ◽  
Mode A

Recent studies have shown that anaerobic co-digestion (AnCoD) is superior to conventional anaerobic digestion (AD). The benefits of enhanced bioenergy production and solids reduction using co-substrates have attracted researchers to study the co-digestion technology and to better understand the effect of multi substrates on digester performance. This review will discuss the results of such studies with the main focus on: (1) generally the advantages of co-digestion over mono-digestion in terms of system stability, bioenergy, and solids reduction; (2) microbial consortia diversity and their synergistic impact on biogas improvement; (3) the effect of digester mode, i.e., multi-stage versus single stage digestion on AnCoD. It is essential to note that the studies reported improvement in the synergy and diverse microbial consortia when using co-digestion technologies, in addition to higher biomethane yield when using two-stage mode. A good example would be the co-digestion of biodiesel waste and glycerin with municipal waste sludge in a two-stage reactor resulting in 100% increase of biogas and 120% increase in the methane content of the produced biogas with microbial population dominated by Methanosaeta and Methanomicrobium.

Towards energy self-sufficiency in wastewater treatment by optimized sludge treatment

2011 ◽  
Vol 6 (4) ◽  
Author(s):  
M. E. Arnold ◽  
E. S. Merta
Keyword(s):  
Wastewater Treatment ◽  
Anaerobic Digestion ◽  
Wastewater Sludge ◽  
Sludge Treatment ◽  
Gas Emissions ◽  
Green House ◽  
Sludge Incineration ◽  
Green House Gas ◽  
Energy Balances ◽  
Green House Gas Emissions

The role of sludge in renewable energy production and the final disposal of sludge are topical issues. The cost of sludge treatment account for a significant share of the total running costs of a WWTP. By increasing the efficiency of sludge treatment, significant savings can be achieved. Savings can be gained e.g. by more efficient energy utilisation of sludge, combined with optimised wastewater treatment processes. In addition to cost efficiency, environmental sustainability of the applied solutions is crucial. The energy balance and green house gas emissions can be used as tools to evaluate the sustainability of sludge treatment options. This paper presents a case-based comparison of energy balances, green house gas emissions and costs of municipal wastewater sludge process chains based on anaerobic digestion or incineration. Information from existing plants was used for conducting the study. Several utilisation options were covered for biogas energy as well for energy from sludge incineration. Based on the results, sludge incineration was the most expensive option of the studied scenarios, but justified if the heat generated can be fully utilised e.g. in district heating. Based on costs and energy balances as well as green house gas emissions it is most preferable in anaerobic digestion chains to feed the generated biogas to a gas engine to produce electricity and heat. Moreover, thermophilic anaerobic digestion can improve the overall economy of a WWTP provided that the biogas yield is sufficiently higher than in a mesophilic process. However increased odour is a risk in thermophilic digestion. The study showed that the most energy efficient process modifications are always very case bound. However the tools developed in this study are generally applicable to waste water treatment plants for similar analyses.

scholarly journals ENHANCED PERFORMANCE OF MULTI-STAGE ANAEROBIC DIGESTION OF TOFU WASTEWATER: ROLE OF RECIRCULATION

2019 ◽  
Vol 10 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Hanny Vistanty ◽  
Rizal Awaluddin Malik
Keyword(s):  
Anaerobic Digestion ◽  
Ph Value ◽  
Anaerobic Reactors ◽  
Multi Stage ◽  
Recirculation System ◽  
In Series ◽  
And Performance ◽  
Anaerobic System

Continuous three-stage anaerobic reactors with recirculation system were employed to treat real tofu wastewater. The system consists of 3 reactors connected in series and effluent of the last reactor was partly returned as feed of the first reactor along with fresh wastewater. The recirculation system was conducted on four variations of recirculation ratio (RR)s of 0, 1.0, 1.3, and 1.5 to evaluate the influence of recirculation on stability and performance of anaerobic system. Results showed that recirculation improved the performance of anaerobic digestion. COD was fluctuated without recirculation and gradually decreased to 373 and 298 mg/L at RR 1.3 and 1.5, respectively. Likewise, pH value was dropped to 6.5 at RR 0, and started to increase to approximately 8.0 upon employing recirculation. In addition, the system also showed excellent toleration against rise in ammonia loading, with effluent ammonia approximately 4.678 mg/L. The findings showed that the system employed had excellent efficiency and stability in treating tofu wastewater. 

scholarly journals Phase Separation in Anaerobic Digestion: A Potential for Easier Process Combination?

2021 ◽  
Vol 3 ◽  
Author(s):  
Eike Janesch ◽  
Joana Pereira ◽  
Peter Neubauer ◽  
Stefan Junne
Keyword(s):  
Phase Separation ◽  
Anaerobic Digestion ◽  
System Integration ◽  
Energy Use ◽  
Biogas Production ◽  
Renewable Energy Sources ◽  
Economic Feasibility ◽  
Monitoring And Control ◽  
Multi Stage ◽  
And Control

The flexibilization of bioenergy production has the potential to counteract partly other fluctuating renewable energy sources (such as wind and solar power). As a weather-independent energy source, anaerobic digestion (AD) can offer on-demand energy supply through biogas production. Separation of the stages in anaerobic digestion represents a promising strategy for the flexibilization of the fermentative part of biogas production. Segregation in two reactor systems facilitates monitoring and control of the provision of educts to the second methanogenic stage, thus controlling biogas production. Two-stage operation has proven to reach similar or even higher methane yields and biogas purities than single-stage operation in many different fields of application. It furthermore allows methanation of green hydrogen and an easier combination of material and energy use of many biogenic raw and residual biomass sources. A lot of research has been conducted in recent years regarding the process phase separation in multi-stage AD operation, which includes more than two stages. Reliable monitoring tools, coupled with effluent recirculation, bioaugmentation and simulation have the potential to overcome the current drawbacks of a sophisticated and unstable operation. This review aims to summarize recent developments, new perspectives for coupling processes for energy and material use and a system integration of AD for power-to-gas applications. Thereby, cell physiological and engineering aspects as well as the basic economic feasibility are discussed. As conclusion, monitoring and control concepts as well as suitable separation technologies and finally the data basis for techno-economic and ecologic assessments have to be improved.

Effects of Thermal Pretreatment of Sewage Sludge on Anaerobic Digestion

1989 ◽  
Vol 21 (4-5) ◽  
pp. 97-108 ◽  
Author(s):  
J. Pinnekamp
Keyword(s):  
Anaerobic Digestion ◽  
Energy Balance ◽  
Sewage Sludge ◽  
Electricity Generation ◽  
Treatment Plant ◽  
Economic Advantage ◽  
Thermal Pretreatment ◽  
Sludge Treatment ◽  
Additional Advantage ◽  
Energy Balances

The study examines the constraints on thermal pretreatment of sludge at temperatures in excess of 100 °C and its effects on subsequent anaerobic digestion. The table below summarizes the maximum measured increase rates and the corresponding optimum pretreatment temperatures as a function of the type of sludge tested. The influence of the sludge type is considerable.Sludge TypeGas Yield without/with PretreatmentMaximum increase RateOptimum Pretreatment Temperaturel/kg VSinfl%°CDigested Sludge60.4223.0+ 269.2180Excess Sludge SLR = 0.03124.7278.1+ 123.0135Excess Sludge SLR = 0.15314.7546.7+ 73.7170Excess Sludge SLR = 2.00234.7334.2+ 42.4135Primary Sludge259.0326.6+ 20.3170Excess Sludge SLR = 0.60596.8600.0+ 0.5135 Calculation of detailed energy balances for various sludge treatment systems with and without thermal pretreatment revealed a clear economic advantage for thermal pretreatment. The excess heat for an overall system composed of thermal pretreatment, anaerobic stabilisation and digester-gas electricity generation is significantly higher than that for a system without pretreatment. Sludge pasteurisation represents an additional advantage of thermal pretreatment. In general, it may be stated that, provided certain conditions are satisfied, thermal pretreatment of sewage sludge prior to anaerobic stabilisation can positively affect the energy balance of the treatment plant.

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