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Today, the lack of drinking water has caused severe crises in many countries. One of the ways to deal with water shortages is to treat wastewater. Petrochemical industries are among the factories that produce significant wastewater. These industries cause a lot of damage to the ecosystem. The use of nanomaterials can play a significant role in the removal of wastewater pollutants. The use of nano-packing in the filtration structure has not been investigated in previous literature. In this research, a gravity filtration unit was used to treat the outlet wastewater from the Fajr petrochemical desalination unit. This unit is filled with titanium dioxide nano-packings. The results of this research show that the turbidity of the effluent discharged from the gravity filtration bed is reduced by about 39 %. This research shows that nano-packing has a significant effect on reducing total dissolved solids and organic carbon. This study shows that the amount of total dissolved solids and organic carbon in treated wastewater is equal to 1 % and 17.1 %, respectively. This research shows that the use of a gravity filtration unit has a significant role in reducing petrochemical effluent pollutants.

Abstract Wastewater can be contaminated with all kinds of microorganisms and small organisms, including bacteria, parasites, fungi and viruses. Therefore, it can be said that biological pollution is one of the most dangerous pollutions. These types of pollution can endanger human health and the environment. In this study, industrial wastewater disinfection has been investigated in a laboratory pilot. In this study, ultraviolet waves have been used for wastewater disinfection. In this research, treatment indicators such as wastewater pH, phosphate, nitrate, biological oxygen and chemical oxygen, organic carbon, and wastewater turbidity have been investigated. The results of this research show that if 4.5 g of dry ice is added to the wastewater entering the disinfection unit, the pH of the wastewater will decrease to about 7.9. The results presented from the disinfection unit show that the amount of chemical oxygen demand and biological oxygen demand have decreased by about 35% and 20.3%, respectively. The results of this unit show that the amount of phosphate and nitrate has decreased by 61.3 and 71.9%, respectively. Laboratory results show that the TDS of wastewater has decreased from 600 to 451 mg/l.

Using transfer-matrix and stationary phase methods, we study the tunneling time (group delay time) in a ferromagnetic monolayer graphene superlattice. The system we peruse consists of a sequence of rectangular barriers and wells, which can be realized by putting a series of electronic gates on the top of ferromagnetic graphene. The magnetization in the two ferromagnetic layers is aligned parallel. We find out that the tunneling time for normal incident is independent of spin state of electron as well as the barrier height and electron Fermi energy while for the oblique incident angles the tunneling time depends on the spin state of electron and has an oscillatory behavior. Also the effect of barrier width on tunneling time is also investigated and shown that, for normal incident, the Hartman effect disappears in a ferromagnetic graphene superlattice but it appears for oblique incident angles when the x component of the electron wave vector in the barrier is imaginary.