| 摘要 |
<p>During the process of purifying sewage by means of activated sludge, in which the coarser matter is removed by rake grids, and the sedimentation tanks are followed by settling out and sludge densification, these last two operations are replaced by filtration through filter beds planted with reeds (phragmites cuminis) or English rice grass (spartina Townsendii); the fluid drawn from the last activated sludge tank being distributed over the filter beds in a sequence providing a drying-out time five to fifteen times the length of the irrigation time. For pref. the filter beds are irrigated for one day and allowed to stand for from 8 to 12 days. A cheaper and more efficient method of coping with sewage in fluctuating amounts, with peak volumes coming in from time to time.</p> |
