Morteza Shakeri,; Hossein Ganjidoust; Bita Ayati
Volume 9, Issue 3 , April 2012
Abstract
The purpose of this study was to determine the efficiency of the USBFprocess for biological nitrogen removal and achieving the optimal hydraulic retention time according to the maximum nitrogen removal in the system. The synthetic wastewater which was used in this research, was a compound of glucose ...
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The purpose of this study was to determine the efficiency of the USBFprocess for biological nitrogen removal and achieving the optimal hydraulic retention time according to the maximum nitrogen removal in the system. The synthetic wastewater which was used in this research, was a compound of glucose and urea as a carbon and nitrogen source with the COD/N ratio remaining around 10, while the N concentration based on the sum of nitrite and nitrate ions was approximately 50 mg/L. The investigation was carried out over two phases of start up with inoculation, and the operation at differing hydraulic retention times with flow rates of 0.8, 1, 1.2, 1.4, 1.6, 1.8 and 2 lit per hour. The experimental results showed the increasing efficiency of the system in nitrogen removal with increased flow rates, such that 89.4, 92 and 95.1 percent of the initial phosphorus concentrate in the wastewater was removed at flow rates of 0.8, 0.1 and 0.12, respectively; however, at flow rates of 1.4, 1.6, 1.8 and 2 lit per hour, the mean nitrogen removal efficiency was reduced to 93, 88, 83 and 80 percent, respectively. At the end, the hydraulic retention time for the biological nitrogen removal in this process, was determined at 40 hours in the whole system which is equivalent to 5 hours hydraulic retention time in the clarifier. USBF, as an advanced biological process, had an appropriate removal efficiency for the biological treatment of nitrogen.
Nadia Sharifzadeh; Bita Ayati; Hossein Ganjidoust
Volume 8, Issue 4 , July 2011
Abstract
Companies need to design engineering software to obtain emission limits before construction and commissioning the plants to control air pollutants. During the design of plants, all emissions should be studied and measured. Since some emissions are lighter or higher than air, there are different methods ...
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Companies need to design engineering software to obtain emission limits before construction and commissioning the plants to control air pollutants. During the design of plants, all emissions should be studied and measured. Since some emissions are lighter or higher than air, there are different methods for their modeling. These models are used for reviewing the effect of gases on the environment and the best model is the one that can design an accident before dispersion. In this research three software packages, namely PHAST, CIRRUS and SHELL FRED, were compared with a newly-created software for measuring the ground level concentration of H2S and SO2. The software packages were based on the Gaussian model for point sources. In these models, for simplicity, some assumptions were made based on one point source above the ground. According to the results, the new software was similar to CIRRUS in D stability of the air that can be used instead.
Hamid Raftari; Hamid Moazami; Hossein Ganjidoust; Bita Ayati
Volume 8, Issue 3 , April 2011
Abstract
Lead and copper are heavy metals that are applied in different industries. Their standard limits in drinking water are 0.05 and 1.3 mg/L, respectively. Since natural absorbents are inexpensive and may be achieved without any cost and they are usually found in abundance in nature, absorption of solute ...
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Lead and copper are heavy metals that are applied in different industries. Their standard limits in drinking water are 0.05 and 1.3 mg/L, respectively. Since natural absorbents are inexpensive and may be achieved without any cost and they are usually found in abundance in nature, absorption of solute ions by these materials is a proper method for eliminating heavy metals from polluted waters and industrial wastewaters. In this study, tea leaves and wheat straw wastes were used to absorb lead while sawdust and rice hull were applied to absorb copper from a polluted solution under batch and continuous conditions. The experiments have been carried out at different concentrations and times with an optimum pH of 5 and 5.5 for lead and copper, respectively. According to the batch experimental results, the equilibrium time has been found to be within the range of two hours. By increasing the concentration of absorbed material, the absorption efficiency has been diminished. The results of the batch experiments coincided with Langmuir and Freundlich isotherms but did not agree with BET and Linear isotherms. Continuous experiments have been accomplished with the use of an absorption column and a high up-flow rate of 0.35 L/min. In general, absorption efficiency has a decreasing trend over time. Based on the results of the continuous column system, the percentage maximum sorption of lead for tea leaves and wheat straw wastes came to be 99.5. This value for copper by sawdust and rice husk was found to be 95 and 63 percent, respectively.
Rohaolah Noori; Bita Ayati; Hossein Ganjidoust
Volume 5, Issue 4 , July 2008
Abstract
Moving Bed Biofilm Reactor has been taken less attention in treatment of surfactants. In this research with consideration of its advantages and suitable efficiency in industrial wastewater treatment, three 5L-reactors at different retention times were used to investigate the removal efficiency of sodium ...
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Moving Bed Biofilm Reactor has been taken less attention in treatment of surfactants. In this research with consideration of its advantages and suitable efficiency in industrial wastewater treatment, three 5L-reactors at different retention times were used to investigate the removal efficiency of sodium dodecyle benezene sulfonate (SDBS), sodium dodecyle sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB). The results indicated that the best removal efficiency in batch loadingsystem with filling ratio of 50% of the reactor volume by LECA (Light Expanded Clay Aggregate) was 90, 95, and 93 percent for SDBS (COD=900 mg/l),SDS (COD=1200 mg/l)and CTAB (COD=1200 mg/l), respectively. NMR test results confirmed biodegradation ability of compounds in MBBR. In the study of filling ratio effect in the reactors, the volumes of the carriers were decreased to 30% and the removal efficiency were improved by 2% for SDBS and CTAB systems but no change was observed for SDS system. In the study of temperature effect no considerable change has been observed in the removal efficiency. Finally, biological modeling of the reactors using Stover-Kinkannon, first order and Grau models have shown that the reactors followed both Stover-Kinkannon and Grau ones.
