| 摘要 |
<p>Wastewater is treated by circulating it around a system comprising a downcomer (1) and a riser (2) communicating with each other at their lower ends, the level of the wastewater in the downcomer being above the level of the wastewater in the riser and providing a hydrostatic pressure head (2) which causes circulation of the wastewater around the system, supplying a gas containing free oxygen to the wastewater as it passes through the downcomer, and pumping the wastewater up from or from near, the top of the riser to a part of the downcomer, at or near the top thereof, which has, for at least a part of its length, a cross-sectional area which is less than the cross-sectional area of the remainder of the downcomer below the said part.</p> |
