Abstract: A process for activating a hydrogenation catalyst in a hydrogenation system having multiple reaction stages by sulfurization comprising sulfurizing the hydrogenation catalyst in each reaction stage with a sulfur-containing hydrocarbon oil and a hydrogen-rich gas containing less than 1000 ppm (by volume) of hydrogen sulfide, successively in the order of from the final reaction stage thereof to the first reaction stage thereof.

Abstract: On treating a waste water with activated sludge, an appropriate amount of sea water is added to the waste water.

Abstract: A loop-style continuous ion exchange unit having a liquid treating section, a material weighing and transfer section, a regeneration section, a washing section and a back-washing section, all of which are connected together in a closed loop. The back-washing section is above the liquid treating section to enable material to fall by gravity into the liquid treating section. The liquid treating section is located above the material weighing and transfer section so that material can fall by gravity into the material weighing and transfer section. The washing area has an outlet located above the back-washing area so that washed material may flow by gravity to the back-washing area. Further, an expansion space is provided above the washing area to compensate for expansion of the material when it is washed.