ACTION OF DIBDIN CONTACT BEDS 
6 
STORM WATER PLOT & BEDS— WEST DERBY SEWAGE FARM 
In April, 1896, the then City Engineer obtained authority from the Works 
Committee to form banks about 3 feet high round plot L, which is about 20 acres 
in area and reasonably level. The object of this was to impound storm water from 
the western outfall sewer, and to gradually run it off into the ' Alt ' through a special 
coke screening chamber, which was constructed on the intake to the 24-inch pipes 
which provided the outlet to the ' Alt.' This arrangement was much improved 
subsequently by providing a 15-inch pipe at a higher level than the 24-inch outlet 
pipes from the screening chamber ; and this 1 5-inch pipe discharged on to the surface 
of a burned ballast filter bed about ^ acre in extent, and thence into the ' Alt.' A 
much clearer effluent was thus obtained than through the coke screens only. 
A considerable amount of sludge was deposited all over plot L, although there 
was only 1 part of sewage in each 36 of storm water, and, as no crops could be raised 
on any part of this plot, authority was obtained in January, 1897, to form three sludge 
beds, each rather over 1 acre in area, which should discharge alternately into a 
common channel and through the coke screening chamber. The effect of these beds 
was to concentrate the sludge, and to enable a paying crop to be raised on half of 
the remaining area of plot L. The other half remainder (about 8 acres) was to be 
devoted to storage of storm water. These two plots of about 8 acres have been 
changed about each year, being one year under cultivation and next year under water. 
The cost of the sludge beds was about £2 50 
BACTERIOLOGICAL FILTER BEDS 
In the year 1898 the Corporation of Liverpool decided to put down filter 
beds, with the object of assisting the irrigation area of the West Derby Sewage Farm. 
The original proposal was to construct four coarse and four fine beds of a cheap 
construction, the excavations being out of the solid clay, and the floors and sides 
being faced with concrete. Owing, however, to difficulties in connection with levels, 
and other local conditions, the number of beds was reduced to, six in three series. The 
first contact beds in each series had also to be built above the natural surface of the 
ground, the secondary beds only being in the solid ground. The beds in use, and 
which comprise three systems, are numbered 1, la, 2, 2a, 3, 3a. 
BEDS Nos. 1 and ia. 
In this pair, the first contact bed (No. 1) was made up of burnt clay to a 
depth of about 2 ft. 8 in., and the second contact bed (No. \a) has burnt clay in the 
bottom to a depth of about 14 inches, and on the top of this coke broken to about 
the size of the ballast, making a total depth of 2 ft. 8 in. 
