Contaminant transport using MODFLOW and MT3D-USGS

[Prince Kumar]

Hello All,

I am a new user of MODFLOW and MT3D-USGS and I am using ModelMuse as GUI. 

For one of my research projects, I am trying to model contaminant (propylene glycol) flow through groundwater. The contaminant source is for a fixed time, not a continuous source. I am considering flow through saturated (below groundwater) and unsaturated (above groundwater) soil. In the fate and transport of glycol, advection, dispersion, and biodegradation process are predominant. 

The following are my questions:

1. The selection of solver type for MT3D depends on the Peclet number and the Peclet number depends on the grid size. So, how do we decide the grid size for a particular problem?

2. I did not find the calculation for the time step for MT3D. How do we fix the time step?

3. I want to inject contaminant at different depths using well. For this, a well will be installed in that particular layer using "number of Z formulas"; Is it right?

4. I want to consider 1st order reaction to simulate biodegradation. For this, the input will be provided into the "Reaction rate dissolved phase"; Is it right?

  

Please help me in solving the above problems. It will be a great help in my research. Any advice will be appreciated. 

Thank you all!

Regards,

Prince