Described herein are methods and devices for biologically treating water and/or wastewater. The methods and devices for treating wastewater may be enhanced using an surge lifting device which moves water and/or solids using volumes of air (for liquid transfer and mixing) and the automatic sludge return mechanism, combined with alternating aeration on and off operation to achieve comprehensive nitrogen and phosphorus removal. This surge lifting device 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 wastewater treatment with less operation and maintenance costs than conventional devices and/or processes. The same surge lifting device can also be installed in an anaerobic digester, and use the biogas generated below the device to automatically mix the digester, without external energy input.
