It somewhat depends on the system and the water being treated. That said the most advanced systems these days for high pressure RO have pressure recovery devices to minimize the energy requirement so that the reject exits the system at a low pressure. The efficiency of these devices can be > 90%.
for 40000ppm seawater, what is the pressure of the reject without the recovery devices.
It depends on factors such as the water recovery (since the osmotic pressure increases with recovery) and the limits of the membrane, and how hard you drive the system to get high flux. My knowledge is somewhat dated, but as of 10 years or so ago, installed systems like this were roughly be 40% recovery or so and 50 atm of pressure as I recall. The emerging systems were pushing recoveries closer to 60% and pressures up to 80 atm. Your best bet for a more precise answer may be to look at the specs for recently installed plants. Sorry I can't be more specific.
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