Sometimes you see something just so...Wizard! - you wonder why this hasn't shown up before. In my recent 12 part manual for a DIY Disaster kit, I note that field hygiene, or lack there of, has killed more people in the world than battlefield fighting. Hand washing is a big part of field hygiene - esp if you are using an outdoor Loo (latrine, slit trench or pit toilet.)... The video linked at the top shows how to build a 5 gallon hand washing sink with integrated fresh water storage and gray water catchment. With a pump. In a word - simply Wizard. Total cost in minimal, convenience is maximal and the boon is even little kiddos can easily wash their hands after using the toilet, before eating and so on. Disposal of gray water can be down the same pit toilet used or some distance from the camp. It doesn't take much of a leap to see this 'system' could be incorporated into a camp table used for food prep and wash-up. The same would apply for home use where running water may be problematic.