Sharif Digital Repository

According to the results, anaerobic co-digester appeared to be feasible with the loading rate of 3.0 kg VS/ m 3.d at 34°C and biogas production rate of 44.8 1/d, which can be used as a fuel resource. It should be mentioned that more heat input is required to achieve the correct operational temperature. This increase in energy may not be outweighed by the increase in the outputs of biogas from the system. Therefore, it is important to consider an energy balance for these systems  

Anaerobic digestion (AD) is a green technology that has been applied for many years. One of the main problems in this process is controlling these bioreactors to maximize methane production. A supervisory control strategy has been proposed to improve the methane production rate in an anaerobic digestion process while minimizing the risk of process failure in the presence of several drastic feedstock changes. The inner loop consisted of a feedback control that manipulated the feed flow rate for achieving the desirable methane production rate. A rule based control strategy was used as supervisory control loop. This controller received the total volatile fatty acids concentration in the reactor... 

Pilot scale experiments were performed on the digestion of dairy cow manure in a semi-continuous process using a mixed plug flow reactor (MPFR) to determine the effects of organic loading rate (OLR), temperature and mixing levels on production biogas and methane yield. Response surface methodology (RSM) was applied for the design and analysis of experiments with the optimization of OLR, temperature and mixing level during the biogas production process. Experiments were designed as per the central composite design technique. Four cubic mathematical models were derived for prediction of the responses. The optimization study has been carried out to identify the highest yields achievable when... 

Anaerobic digestion processes and the conductive electron transfer approach were used to describe the bioenergy production processes in a microbial fuel cell (MFC), respectively. The present model is a far more completed form of conduction-based modeling which is able to predict performance of an MFC fed with complex substrates and inoculated with multi-population culture. One-dimensional spatial distributions of the different microorganisms, as biocatalysts of processes and intermediates produced in the different steps of the anaerobic digestion processes in the biofilm, as well as the dynamic behavior of the anolyte including syntropic interactions among different groups of microorganisms... 

In the present work, a fuzzy supervisory control approach combined with an adaptive model predictive controller (AMPC), has been proposed to maximize the productivity of an anaerobic digestion (AD) process, while keeping the operation stable. In the proposed hierarchal control strategy, the set-point of the inner loop is provided by a supervisory controller. In the inner loop an AMPC has been applied to achieve the desired methane production rate by manipulating the feed flow rate. The AMPC is designed based on the auto-regressive moving average (ARMA) model whose parameters are updated at each sampling time to make the controller more robust against uncertainties and external loads. In the... 

A modelling study on the anaerobic digestion process of a synthetic medium-strength wastewater containing molasses as a carbon source was carried out at different influent conditions. The digestion was conducted in a laboratory-scale hybrid anaerobic baffled reactor with three compartments and a working volume of 54L, which operated at mesophilic temperature (35°C). Two different kinetic models (one model was based on completely stirred tank reactors (CSTR) in series and the other an axial diffusion or dispersion model typical of deviations of plug-flow reactors), were assessed and compared to simulate the organic matter removal or fractional conversion. The kinetic constant (k) obtained by... 

Purpose: Anaerobic digestion is a promising technology for simultaneous treatment of biodegradable organic matter of municipal solid waste (MSW) and production of renewable energy. Mixing modes and temperature have influences on biogas production in anaerobic digesters treating MSW. Therefore, in this study, digester was operated at different modes of mixing and temperatures to obtain design criteria. Methods: The experiments were carried out in a semi-continuous digester. In the first part of the investigation, temperature was set at 25, 28, 31 and 34 °C. During this step, digester content was mixed in an intermittent mode by mechanical mixers. In the second part of the study, mixing... 

The purpose of this study is to evaluate an anaerobic system (ABR) cultured by chemoautotrophic bacteria for biodesulfurization of natural gas. In this study anaerobic baffled reactor with five compartments and active volume of 10 l was used. For increasing solid retention time, reactor was packed by pumice with 0.5-2 cm diameter which active volume decreased to 9 l. Inoculation was performed by activated sludge from municipal sewage treatment, which was kept in anaerobic condition for 1 year. The synthetic wastewater which contains S2O32- ion was used in start-up and S -2 for running of ABR. Performance of the reactor was evaluated at three equivalent hydraulic retention times (HRT) of 50,... 

The objective of this study was to construct a novel model to be applied in a general manner to simulate microbial electrochemical cells (MXCs); for both microbial fuel cell (MFC) and microbial electrolysis cell (MEC). The liquid bulk was modeled based on the organic matters degradation to acetate via the anaerobic digestion process. Biofilm simulation was established based upon one-dimensional distribution and the dynamical electron transfer was completed by means of the conduction-based mechanism. We, for the first time, introduced biofilm local potential modeling for MEC simulation with general and simplified linear boundary conditions. The MFC-related part of the model was evaluated... 

Nanotechnology is gaining more attention in biotechnological applications as a research area with a huge potential. Nanoparticles (NPs)can influence the rate of anaerobic digestion (AD)as the nano-sized structures, with specific physicochemical properties, interact with substrate and microorganisms. The present work has classified the various types of additives used to improve the AD processes. Nanomaterials as new additives in AD process are classified into four categories: Zero-valent metallic NPs, Metal oxide NPs, Carbon based nanomaterials, and Multi-compound NPs. In the following, application of nanomaterials in AD process is reviewed and negative and positive effects of these materials... 

Lignocellulosic materials are recalcitrant to bioconversion, due to their rigid physiochemical structure. In this work, the effects of Fe2O3–TiO2 and NiO–TiO2 nanoparticles (NPs) and FeCl3 and NiCl2 salts, on the anaerobic digestion (AD) of wheat straw have been investigated. For this purpose, metal oxide-TiO2 NPs were synthesized and fully characterized. Results showed that addition of 0.252 mg of NiO–TiO2/g total solids (TS) to batch assays resulted in increase of soluble chemical oxygen demand (COD) and 67% increase in volatile fatty acids (VFAs) concentration compared to control tests during the first 4 days of experiments. These results indicate that hydrolysis and acidogenesis rates... 

Sufficient quantity of trace metals is essential for a well performing anaerobic digestion (AD) process. Among the essential trace elements in active sites of multiple important enzymes for AD are iron and nickel ions. In the present study, iron and nickel in the form of Fe2O3 and NiO were coated on TiO2 nanoparticles to be used in batch and continuous operation mode. The effect of TiO2, Fe2O3–TiO2, and NiO–TiO2 nanoparticles on each step of AD process was assessed utilizing simple substrates (i.e. cellulose, glucose, acetic acid, and mixture of H2–CO2) as well as complex ones (i.e. municipal biopulp). The hydrolysis rate of cellulose substrate increased with higher dosages of the coated...