Described herein are methods and devices for treating water, wastewater, and organic wastes. The methods and devices are mixed by using hydraulic surge mixers. This surge mixer is driven by gas and can provide occasional surges of water using large bubbles which are able to move great volume of liquid while minimizing dissolved oxygen transfer to the surrounding liquid. Use of the devices and processes herein provides a simple, eloquent approach to water and wastewater treatment with less operation and maintenance costs than conventional devices and/or processes. The same surge lifting device can also be installed in other reactors to mix the tank content and enhance reaction with reduced energy use and maintenance needs.