346 
Sewage Disposal and Rivers Pollution. 
The sewage from Dantzig has been utilised by irrigation on what was 
originally useless sandy land on the coast, the subsoil water rising to within 
5 feet of the surface. The sewage liquid, when applied to the land, forces 
out any air from it in bubbles, and then sinks rapidly into the subsoil, 
lea-ring on the surface and in the pores of the soil both the suspended and a 
portion of the dissolved matters. The land, originally let at 4 \d. per acre, 
was subsequently leased to a contractor for 30 years at a rental of 1/. 11s. 6c/. 
per acre. The whole affair, I am informed, has technically, financially, and 
otherwise proved a complete success. The depth of humus or vegetable soil 
has been increased, by the continued irrigation. The quantity of sewage 
applied is equal to about 5,500 gallons per acre per day. Analyses of the 
effluent water showed that it came within the standard requirement laid 
down by the Rivers Pollution Commissioners. 1 
The checks to the universal spread of broad irrigation have, 
however, been serious, though of simple character. In some places 
there is no land suitable for sewage filtration, in others the sewage 
is not suitable to be placed upon the land. Some land, actually 
used for sewage farms, will take only 2,000 gallons per acre per 
day, 2 and does not deal effectually with this, whilst some few lands 
will purify easily 5,500 gallons as at Dantzig, and in England the 
gravelly soil of the Rugby Sewage Farm is made to take over 6,000 
gallons, and the free soil of Croydon over 11,500 gallons. By the 
combination of intermittent filtration with irrigation, that is by 
laying out a portion of the land as filtration areas, the quantity of 
sewage that can be dealt with is still more extended, and this is the 
plan now generally adopted in the most successful sewage farms. 
In this way at Kendal the farm takes an average of 37,500 gallons 
per acre daily, and at Forfar (17 acres irrigation, 7 intermittent 
filtration) an average of 20,000 to 25,000 gallons per acre. When the 
filtration areas are used alone, as is often the case for weeks 
together, they will take 70,000 gallons to the acre. The provision 
of filtration areas as adjuncts to land intended for irrigation is a 
positive advantage, too, from the farming point of view ; for one of 
the main difficulties in sewage farming is the necessity of dealing 
with the regular daily and nightly flow, whether the land and the 
crops require it or not. Intermittence is one of the conditions of 
success in the day-by-day application of sewage to land, whilst it is 
obvious that land for cropping can deal with much larger quantities 
in the spring and summer than in the winter, and that there are 
periods — for example, when the land is frost-bound — when it is 
desirable to keep the sewage off altogether, since the only result of 
applying it would be for it to run off - the surface unpurified. 
On the filtration areas frost is seldom an impediment to treat- 
ment, the large quantity of (comparatively) warm sewage with 
which they are constantly flooded effectually preventing the ground 
from becoming frost-bound. At Leeds “ about two years ago an 
attempt was made by flooding one of the areas to make a skating- 
' Min. Proceed. Inst. C.E., Yol. XL1V. 
2 This is equivalent to about seventy persons per acre. 
