TANKS.
Under this heading are included a large number of tanks of various types and systems, for each of which some particular advantage is claimed in ordinary circumstances, or some peculiar suitability for special conditions. All are, however, ostensibly designed for the purpose of arresting the organic matters in suspension, in order to prepare the sewage for the subsequent stage of oxidation in contact beds, on percolating filters or on land.
Types and Capacities of Ordinary Tanks.—In addition to detritus tanks described in the preceding chapter, the Royal Commission on Sewage Disposal, in its fifth Report, has dealt with five different methods of tank treatment in detail. These are:—
1. Septic tanks, having a total capacity of about 24 hours’ dry-weather flow.
2. Continuous-flow settlement tanks without chemicals, having a total capacity of about 15 hours’ dry-weather flow.
3. Continuous-flow settlement tanks with chemicals, having a total capacity of about 8 hours’ dry-weather flow.
4. Quiescent settlement tanks without chemicals.
5. Quiescent settlement tanks with chemicals.
The two last-mentioned have each a total capacity of about 24 hours’ dry-weather flow.