Saito M, Magara Y
Department of Urban Environmental Engineering, Graduate School of Engineering, Hokkaido University, Sapporo, Japan.
Water Sci Technol. 2002;46(9):137-45.
Polluted water is abandoned or stored untreated in many places. Especially, small water bodies such as ditches, ponds, wastewater tanks, etc. have not yet well been considered. The self-purification stabilizes the wastewater, but oxygen supply limits the biodegradation process. In the natural environment, approximately 3 g oxygen can be dissolved per m2 per day if the water is completely deprived from dissolved oxygen; this is the magnitude of self-purification capacity. To improve the quality of polluted water with higher oxygen demand than natural reaeration capacity, enhanced aeration is required. The laboratory experiment disclosed that water trickling onto the water surface or shallow stirring of water less than 10 mm in depth increased the mass transfer rate significantly. At the same time, the methods were found more efficient than bubbling aeration of large-scale treatment plant in terms of energy input against oxygen supply. Though it is an efficient method, elaborate application will be necessary since the mass transfer rate is not as high as bubbling aeration.
在许多地方，污水未经处理就被丢弃或储存起来。特别是像沟渠、池塘、废水池等小型水体尚未得到充分考虑。自我净化可使废水稳定，但氧气供应限制了生物降解过程。在自然环境中，如果水中完全没有溶解氧，每平方米每天大约可溶解3克氧气；这就是自我净化能力的大小。对于需氧量高于自然复氧能力的污水，为提高其水质，需要强化曝气。实验室实验表明，水从水面滴下或对深度小于10毫米的水进行浅搅拌可显著提高传质速率。同时，就能量输入与氧气供应而言，这些方法比大型处理厂的鼓泡曝气更有效。尽管这是一种有效的方法，但由于传质速率不如鼓泡曝气高，所以仍需精心应用。
