1. Using smaller granules, which gives greater contact surface,
e.g., 0,4 – 0,85 mm.

2. A slower filtration speed (HSV), to give longer contact time.
The filtration speed can be controlled by:

1. Selecting the carbon grain size

2. Packing the carbon in the pipe

3. Impeding the flow
 

 

If you are using carbon with a larger grain size, e.g., 0.4-1.4 mm, change to one that is smaller. Tap on the pipe to pack as much carbon in as possible. Be careful not to pack the peat carbon (0.25-1 mm) too hard, or it will block the pipe.
Impeding it mechanically can also slow the rate of speed. This has to take place at the end of the pipe, never at the top, or you would get air in the pipe. You can apply more or denser filter papers, or build and attach a tap or similar device. A rubber bung with a
length of tubing and an aquarium tap is one example. You must use food-grade materials with alcohol tolerance, which do not give off-flavors to the alcohol for the impeding process.

A short MTZ means you can purify larger volumes through the carbon. If you cannot get a suitably short MTZ, you must extend the pipe.