Lye can be dried back into a solid form, but honestly it's probably safer and easier for everyday people to dispose of it.
I don't know how much liquid-y lye you have. If you have a lot, you might see if you could take it to your local waste disposal agency and dispose of the lye there as hazardous waste. I live in the USA, and our county solid waste disposal facility will accept hazardous waste by appointment. Not every county will do that, however, so it's something a person would have to check out.
Please, please don't put lye in the regular trash. That is just creating the potential for a terrible accident to an unsuspecting animal, child, or garbage collector.
If you only have a small amount of lye, I would wash it very, very slowly down the drain while running LOTS of COLD water from the tap. Run the COLD water for 5-10 minutes after all the lye is gone -- keep washing and diluting and cooling the lye as it travels through your sewer system. Do not use warm or hot water -- the lye will make heat on its own, so don't make things worse by adding even more heat.
Hope this helps!
