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V.— TABULATION OF INFORMATION RESPECTING THE BACTERIAL OR
NATURAL TREATMENT OF SEWAGE AT VARIOUS CENTRES
THROUGHOUT THE COUNTRY.
The information set forth in the following tables has been courteously supplied by the various
local authorities throughout the country, who have used bacteria beds in connection with the treatment
of sewage or sewage effluent, either in a permanent installation or in an experimental form.
In consequence of the necessarily complicated nature of any attempt to arrange in systematic
order the results of such work carried out under very varying conditions, some explanation of the
tables and of their arrangement is necessary.
The information has been placed in two main divisions, one dealing with the bacteria beds
and the other dealing with the septic tanks; there is also an additional column for remarks.
The division dealing with the bacteria beds is divided into three tables, as follows—
Table 1.—Particulars of the bacteria beds.
Table 2.—Particulars as to the working of the bacteria beds.
Table 3.—Particulars as to the capacity of the bacteria beds, and as to the loss of
capacity during working.
The division dealing with the septic tanks is divided into two tables, as follows—
Table 4.—Particulars of the septic tanks (if used).
Table 5.—Particulars as to the working of the septic tanks.
Table 1 is a record of the details of the construction of the various beds used by the different
local authorities. In some instances, more especially in centres where reports have been published
of the work which has been carried out in the bacterial treatment of sewage, the details of the various
beds are very full, and in these cases each bed is dealt with separately. In other instances, principally
where the treatment is of a permanent character and the beds are frequently uniform in size and
structure, the groups of beds only are described.
In the column "Material and size of the material of which the beds are composed," the size is
determined by the mesh of the sieves used in screening the material, unless otherwise stated. Thus,
½ inch to 1/16 inch means that the material is such as would pass through a screen of ½ inch mesh and
would not pass through a screen of 1/16 inch mesh.
Table 2 is a record of the different experiments which have been carried out at the various
centres, but in many instances the records are insufficient to justify the results being set out separately
in the table. In such instances only the general details of the manner in which the beds have been
worked are recorded. In the case of permanent installations, where the beds have been uniformly
dealing with the same class of liquid for some years, only the more recent results are given in the
table.
It was found convenient to insert the columns under the heading "Particulars of the
settling and of the detritus tanks" in this table, although they do not afford any information as to the
working of the bacteria beds.
The figures in the column "Quantity of sewage treated in 24 hours per acre of bed one foot
deep" have been calculated from data given, in order that the quantities dealt with by the various
beds at a uniform depth, may be seen at a glance.
Table 3.— The importance of information bearing on the capacity of the beds and on the loss
of capacity noticed in the working of the beds, rendered it necessary to devote a table to this subject.
The records in this table are not intended to correspond with the experiments detailed in the previous
table; they are merely such records as have been made of the variations in the capacity of beds. In
some instances the records furnished were too extensive to insert in these tables; in such instances
extracts have been made from the data supplied.
In the column "Capacity, when empty, of the tank containing the bed" figures are given
representing the capacity of the tank before the coke was placed in it. In such cases, where the
whole depth of the tank is not occupied by the material of which the bacteria bed is composed, the
capacity is given only of that portion of the tank which is occupied by the material.
The original water-capacity of the bed in the tank means the liquid capacity of the bed after
the material of which it is formed has been thoroughly soaked. The original water-capacity therefore
does not mean the quantity of liquid which could be poured into the bed in its dry condition, but
rather the quantity which could be drained from the working bed during the specified time of
emptying.
Since the capacity of a bed alters considerably during a lengthened period of rest, the returns
have usually included measurements which have been made after such rest periods. Such measurements
have not always been made from the first filling after a rest period, and in such instances a
draining period is generally recorded as well as the number of fillings since the rest period.
Table 4 furnishes details concerning the septic tanks used at the various centres.
Table 5 is a record of the working of the septic tanks.
The information in these tables has been brought up to 30th April, 1902.