Utilization of Corn Residues for Water Filtration at Fish Tanks

Filtration has been widely used in re-circulating aquaculture system to remove waste. However, the study of some agricultural residues （corn） usage as the filter medium has not yet been studied. Therefore, the aim of this study is to construct a filter made from inexpensive and readily available corn residues and to analyze its effectiveness in controlling suspended solids that directly impact health of fish through abrasion of gill tissues or indirectly through water quality deterioration. The performance evaluation procedure was carried out in an aquaculture system with production in glass tanks located indoor in laboratory at Faculty of Agriculture, Damietta University, Egypt. The evaluation included three concentrations of total suspended solids （450, 900 and 1,350 mg/L）; four residues particle size distribution （3.35, 9.53, 12.7 mm and ascending order to mentioned sizes from bottom to top）; and four thicknesses of filter layer （9, 21, 33 and 45 cm）. The effectiveness of this filter was measured by determining filter efficiency （ηf）, % and filtration rate （FR）, mL/min. It was observed that the maximum value of （ηf）, % was achieved at 450 mg/L concentration of total suspended solids, ascending order to sizes from bottom to top and 45 cm thickness of filtration layer. The maximum value of filtration rate was achieved at 450 mg/l concentration of total suspended solids, 12.7 mm particle size distribution and 9 cm thickness of filter layer. Results indicated that this filter is efficient enough to remove suspended solids. Therefore, this milled corn residues filter can be used in aquaculture systems for Nile tilapia, Oreochromis niloticus culture system.

Theoretical analysis of polarization control for the stable output of multi-carrier source based on a re-circulating frequency shifter

Fluctuating polarization state-of-light in the optical loop is an important factor that seriously influences the output performance of a multi-carrier source based on re-circulating frequency shifter （RFS）. The reason for output spectrum instability when no polarization controller （PC） is present in the loop is analyzed theoretically. Numerical simulations for the output spectra of the multi-carrier source with and without PC are conducted, and the trajectories of the several frequency components polarization states on the Poincare sphere with and without PC are compared. The results show that the performance of multi-carrier source based on a RFS can be improved effectively by adjusting the PC in the configuration properly.

A comprehensive evaluation of re-circulated bio-filter as a pretreatment process for petroleum refinery wastewater

Conventional biological treatment process is not very efficient for the treatment of petroleum refinery wastewater （PRW） that contains high-concentration of organic contaminants. Prior to biological treatment, an additional pretreatment process for PRW is required for the effluent to meet the discharge standards. While re-circulated bio-filter （RBF） has been applied as a pretreatment process in several PRW treatment plants, its effects have not been comprehen- sively evaluated. In this study, the parameters of operation, the changes in pollution indexes and contaminant composition in an engineered RBF have been investigated. We found that mainly highly active de-carbonization bacteria were present in the RBF, while no nitrification bacteria were found in the RBF. This indicated the absence of nitrification in this process. The biodegradable organic contaminants were susceptible to degradation by RBF, which decreased the Biological Oxygen Demand （BODs） by 83.64% and the Chemical Oxygen Demand （CODcr） by 54.63%. Consequently, the alkalinity and pH value of RBF effluent significantly increased, which was unfavorable for the control of operating parameters in subsequent biological treatment. Along with the decrease of CODcr, the RBF effluent exhibited a reduction in biodegradability. 834 kinds of recalcitrant polar organic contaminants remained in the effluent; most of the contaminant molecules having complex structures of aromatic, polycyclic and heterocyclic rings. The results of this study showed that RBF could efficiently treat PRW for biodegradable organic contaminants removal; however, it is difficult to treat bio-refractory organic contaminants, which was unfavorable for the subsequent biological treatment process operation. An improved process might provide overall guarantees for the PRW treatment.

Computational Analysis of a Variable Ejector Flow

The present study addresses a variable ejector which can improve the ejector efficiency and control the re-circulation ratio under a fixed operating pressure ratio. The variable ejector is a facility to obtain specific recirculation ratio under a given operating pressure ratio by varying the ejector throat area ratio. The numerical simulations are carried out to provide an understanding of the flow characteristics inside the variable ejector. The sonic and supersonic nozzles are adopted as primary driving nozzles in the ejector system, and a movable cone cylinder, inserted into a conventional ejector-diffuser system, is used to change the ejector throat area ratio. The numerical simulations are based on a fully implicit finite volume scheme of the compressible, Reynolds-Averaged Navier-Stokes equations. The results show that the variable ejector can control the recirculation ratio at a fixed operating pressure ratio.