Sharif Digital Repository

Nitrogen compounds are becoming increasingly important in wastewater management, because of the many effects that nitrogenous material can have on the environment that need nitrogen removal. In this study, the performance of a submerged fixed bed reactor in nitrogen removal, constructed two anoxic and aerobic sections under Modified Ludzack-Ettinger process was investigated. Laboratory experiments were conducted at a constant COD concentration of 350 mg/lit, hydraulic retention times of 8, 12 and 18 hours and influent ammonia loading rate between 0.128 and 0.955 g NH3/m2.day. Nitrogen removal efficiency was obtained between 80.4 and 97.3%, and COD removal efficiency was achieved between 88.9... 

According to the environmental lows and standards, wastewater of petroleum industries such as refineries and petrochemical that include many petroleum compounds like aromatic and aliphatic hydrocarbons, must be treated up to desirable limit, before entering the collecting network. Using microorganisms is one of the fundamental ways of biodegradation of these polluted compounds. Since phenolic compounds are the main components of raw petroleum, strains that are capable of tolerating phenol and usage of this poisonous hydrocarbon are specifically important. Therefore, in this study the potentiality of the indigenous thermophilic bacterium Nocardia otitidiscaviarum strain TSH1, for degradation... 

One of the most undesirable compounds present in various crude oil cuts are sulfur compounds That creates a lot of problems in different stages of refining and when consumed. In this study, the hydro-desulfurization process that is the most common method of treating oil cuts in the refinery industry and in terms of economic and environmental special place in the oil industry and related industries, has been discussed. In hydro-desulfurization process, sulfur compounds under high pressure and temperature, are converted to hydrogen disulfide in a catalytic reactor. In this study, the catalytic reactor may be simulated with the utmost care. In this context, Euler-Euler two-phase model that is... 

Nitrogen compounds are becoming increasingly important in wastewater management. Due to several adverse effects which nitrogenous materials can have on the environment, there is a significant need for nitrogen removal. In this study, the biological nitrogen removal process from a wastewater with low COD was investigated in a submerged fixed bed reactor, constructed two anoxic and aerobic sections under Modified Ludzack-Ettinger process. Volume of each section was 10 liters. About 60% of each section was occupied with pumice stone.Experiments were conducted in 9 runs, for hydraulic retention times of 8, 6 and 4 hours, influent ammonia concentrations of 180, 90 and 30 mg/lit and recyle ratios... 

In this study, the use of a fixed bed of the Kaldnes commercial carrier in the activated sludge system has been investigated. In this way, at zero time, a submerged fixed bed of Kaldnes was placed into a completely mixed activated sludge reactor and its various parameters were investigated during the time. During the experiment, the fixed bed (Kaldnes carriers enclosed in a lace) with 20, 35 and 50 percentage of volumes were compared to regular activated sludge reactors (without any carriers). The studied parameters are COD, DO, MLSS, and P-PO43-. Input COD was changed at concentrations of 1200 and 400 mg/L, and the reactor hydraulic time was adjusted to 10 and 16 hours. It was observed that... 

Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural... 

An industrial scale reactor for light olefinsproduction was modelledusing the oxidative dehydrogenation (ODH) of light paraffinsin a multi-tubular reactor system involving 10000 small diameter tubes immersed in a shell with proper liquid-cooled flows. Here a theory-based pseudo-homogeneous 1-D model describing the operation of a fixed bed reactor for the ODHparaffinstoolefins over a Ni-Nb-O mixed oxide catalyst (for ethane) and over a V2O5/γ-Al2O3catalyst (for Propane),was employed. The paraffin and oxygen conversions, gas process and coolant temperatures, as well as other parameters affecting the reactor performance, including pressure, were examined. Furthermore, the applied model showed... 

Bio-desulfurization is the sulfur removal process from organosulfur compounds by the action of microorganisms (which are capable of removing sulfur). Too many studies have been carried out in the use of biocatalysts for BDS process. In this project, we have used data obtained from a previous experiment in which a trickle bed reactor (diameter: 0.066 m, height: 0.6 m) and a Rhodococcus sp. 12891 starin immobilized on bed particles are used to produce diesel with low sulfur content. Sulfur concentration of inlet diesel is between 200ppm to 540 ppm. parameters of process are recycle Ratio , volumetric flow rate and sulfur content of inlet diesel.
A mathematical model for trickle bed... 

Nowadays, with respect to environmental pollution and energy supply, producing gasoline from methanol or syngas is one of the most interesting research subjects. Gasoline production from methanol is a catalytic process that produces high-quality gasoline with minimum unwanted compounds. So this gasoline is a clean fuel and it can be replaced to petroleum gasoline. Because of that, it can be a valuable process in the petrochemical industry. One of the most important aspects of this process is catalyst deactivation with respect to time on stream. Catalyst deactivation is usually caused by poisoning, sintering, blocking pores, and coking. In this research, material and energy balance equations... 

Bisphenol A is one of Endocrine Disturbing Chemicals. Enzymatic removal of bisphenol A is an interesting and green method. However, application of enzymes has been hampered due to lower operational stability and lots of difficulties in recovery and recycling. Enzyme immobilization can ba an innovative approach to circumvent these drawbacks. Laccase from Trametes hirsuta used for Bisphenol A removal. Firstly, magnetic nanoparticles were synthesized by coprecipitation method and aminofunctionalized by (3-aminopropyl)-mmethoxysilane. Subsequently, laccase was precipitated with i-propanol in the presence of aminofunctionalized nanoparticles and followed by addition of glutaraldehyde to the final...