this depends on how much and what the volume of alcohol consumed was and also it can vary from person to person... (etc how much you weigh, your height, age) usually no longer than 24 hours unless you have alcohol poisoning... also if you drink alot of water it can be flushed out of your system alot quicker... water and bread is the way to go
Alcohol is oxidized at the rate of about one ounce per hour in the liver. Drinking water or coffee does not make the process go faster. Breathing pure oxygen will make the process faster. Drinking alot of water will lessen the chance of a hangover.