House and Garden 
attention if the doses are flushed automatically. 
High Rate Streaming Filters .—These are coining 
into favorable notice. The Friern Barnet type, 
where sewage is intermittently spread over and 
percolates through sandy soil, thoroughly mixed 
with comparatively large and porous material, has 
proved to give excellent results. Great care must 
however be exercised in keeping a six inch top coat¬ 
ing of sandy soil in proper condition, by raking, etc. 
to insure satisfactory results. This type has been 
little used in this country as yet, owing to the fact 
that in New England, (whose inhabitants have been 
the pioneers in sewage purification), suitable sand, 
can usually be found and made use of in its natural 
position. 
Contact Beds .—These are water-tight reservoirs, 
66% of the holding capacity of which is occupied by 
broken stone, coke, or other material of comparative¬ 
ly large size. 1 he outlets from these beds are closed 
while the sewage is fed to them. The liquid, if well 
distributed over the top, passes downward over the 
surfaces of the material inhabited by bacteria. Col¬ 
lecting in the bed it “rests in contact” so as to permit 
of the polluting matters both in solution as well as 
those in suspension, gravitating to the pieces of bro¬ 
ken stone or other material, and adhering to them by 
“mass action.” When the outlet is opened, the 
sewage water passes out of the contact bed, leaving 
behind it impurities to be consumed and mineralized 
by countless millions of bacteria, which are active 
during the hours in which the bed “rests empty” 
and aerates. The size of the material used allows 
of the passages between the pieces being sufficient to 
insure the subsequent drainage away of the mineral¬ 
ized particles. This is one of the varieties of what 
are termed “high rate methods,” for it is capable of 
producing a nonputrescible effluent on i- 50 th the 
area requisite in land treatment, for dealing with an 
equal volume of sewage. The certainty, where re¬ 
liable devices are employed, for automatically open¬ 
ing and closing the inlets and outlets to these beds, 
that sewage will be equally distributed throughout 
the whole bulk of the material, without danger of 
channels gradually forming, through which it may 
pass away untreated, has caused this to be the first 
high rate method to be widely used and which use, 
for certain practical reasons, is likely to continue in 
numerous cases and especially in cold climates, in 
the face of a preference by some for later types of 
oxidizing filters. 
Percolating Filters .—This name is usually 
employed in England for designating beds com¬ 
posed of large material, through which sewage 
is continually percolating and passing in thin films 
over the surface of the material, and always in the 
presence of air. They are rapidly claiming atten¬ 
tion, on account of requiring only i-ioth% of the 
area required by sand filters. The success of this 
method is naturally dependent upon the manner in 
which the sewage is sprinkled, which must be in suf¬ 
ficiently fine streams to insure that it passes over 
the surfaces of the pieces of material from top to 
bottom, in so finely divided a state, that it does not 
flood the air passages. There are two methods of 
accomplishing this, one of which is, to spray the 
sewage through numerous fixed sprinklers. This 
is effective, but may prove objectionable if in close 
proximity to dwellings. The other method is to 
sprinkle by means of mechanically operated travel¬ 
ling distributors, which pass backward and forward 
over the filter bed, or where circular beds are con¬ 
structed to revolve slowly, in this way, although sew¬ 
age is continually being sprinkled, only a small por¬ 
tion of each filter is fed at one time, the remainder 
resting for about seven minutes, until the next turn 
of the distributor. 
It will be seen therefore, that there are a number 
of distinct ways of successfully furnishing food to 
sewage consuming bacteria. 
Neither chemical treatment, nor the most elabo¬ 
rate system of strainers, can do more than partially 
purify sewage water. Considering, therefore, that 
an average of from thirty to one hundred gallons of 
this water is daily contributed by every inhabitant 
using private and public sewers, and in view of the 
continually increasing need of guarding all drinking 
water supplies from contamination, it assuredly be¬ 
hooves us all to see to it, that sewage is not permitted 
to go untreated, but that the laws governing the 
work of these kindly agents, which nature has pro¬ 
vided for our use in such liberal numbers, be pains¬ 
takingly complied with. Thus may we facilitate 
the accomplishment of their life purposes in the im¬ 
provement of our water courses, and the protection 
of our homes. To do less than this is morally 
wrong, if not legally criminal. 
190 
