16 
NORTH SHORE BREEZE 
SEWERAGE FOR MANCHESTER 
Continued from page 3 
1. As to Chemical Precipitation. 
This method, which is still in use in 
London, consists in precipitating the 
solid matter in the sewage by the use of 
different chemicals, but the expense is 
great and the Fesults not satisfactory, as 
the sludge (the precipitated solids) has to 
be disposed of afterwards, and the sew- 
age is not thoroughly purified, therefore 
I will not dwell on it. 
The four other methods depend for 
their efficiency on using the good germs 
to eat up the bad ones. 
II. Sewage Farming has been and 
still is very extensively carried on in 
Europe and works very well. We know 
what a wonderfully purifying effect earth 
has. We have all seen fields heavily 
manured in the autumn and found all of it 
practically absorbed in the spring. This 
principle has been made use of by the 
world for hundreds of years, but it is 
only comparatively recently that we have 
known that the reason the earth is such 
‘a great purifier is because all the little 
spaces between the particles of soil are 
filled with hungry bacteria, which eagerly 
eat up any food given them, and happily 
for us these bad germs serve as their 
food. Berlin has the largest sewage 
farms in the world, but the process is a 
slow one and the amount of land re- 
quired to purify the sewage is very large. 
In some communities, like our dry West, 
this system may be very desirable; her 
in the East the saving of the value of 
the organic materials in the waste by 
using them in this way as manure, seems 
to be more than offset by the expense of 
the method. (S. R. L., page 29.) 
The remaining three methods are at- 
tempts to improve on the old sewage 
farming and to adapt the principle to 
thickly settled communities, giving the 
good bacteria a better chance to get at 
the sewage, and making a small amount 
of land able to do not only the same 
work but to do it better. 
Although many experiments were 
made in Europe the true nature of 
sewage purification as a bacterial oxi- 
dation was really proved by the work 
of the Massachusetts State Board of 
Health—work which has become clas- 
sic—at its Experiment Station in Law- 
rence, established in 1887. 
A very interesting discovery about the 
sewage devouring organisms is that there 
is another class of virtuous bacteria which 
live in water, they are called anzrobic 
bacteria, and those that live in dry earth 
are called zrobic. By letting sewage 
stand for a time in a tight cesspool, 
or septic tank, as it is called, before it is 
otherwise treated, these anzerobic_ bacte- 
ria are given a chance to do their work, 
and many experimenters have thought 
that sewage which has stood in this way 
can be more quickly purified and on a 
smaller area than sewage treated only by 
means of the zrobic bacteria. It is cer- 
tain, however, that it should not stand 
too long. “The anzrobic bacteria, how- 
ever, never do more thana part of the work 
of purification and therefore, sewage can 
never be properly purified in wet soil. 
The tight cesspool, or septic tank, can 
be used with any of the three methods 
left to consider. 
III. Contact Beds are water tight 
compartments, where the sewage can be 
held and kept in contact with the bacte- 
ria long enough to allow them time to 
eat this objectionable matter. The beds 
are made of small pieces of coke, stone, 
brick, slate, clinker,*or of any hard sub- 
stance, and the particles vary in size 
from + of an inch to several inches—the 
important thing being to allow surfaces 
on which the bacteria can collect and 
cracks through which the sewage can 
pass, the bacteria gobbling it up as it goes 
by. 
They have been tried with and. with- 
out the septic tank and in what is called 
singe and double contact, which means 
putting the sewage through only one bed 
or through a second one after the first. 
Many experiments have been made with 
them and the best treatment would seem 
to be to keep the sewage a short time 
either in a septic tank, or merely to al- 
low it to settle and form a sediment; and 
then subject it to double contact—the 
second bed being of smaller material than 
the first. “They must be used intermit- 
tently to allow the bacteria time to muster 
their forces for their next meal. In 
England and our own West they will 
doubtless be of much use, because sand 
is there scarce and therefore expensive, 
but though they partly purify the sewage 
very quickly, it is not done so completely 
as by sand filters of the glacial drift sand, 
which we have so abundantly here in 
New England. 
IV. The Trickling Filter is a system 
of disposing of sewage over beds of 
somewhat the same material as the Con- 
tact Beds, either continuously or at very 
frequent intervals without allowing it to 
stand on the beds, and seems to be de- 
decidedly better than the contact bed, as 
it is more rapid and purifies the sewage 
better. It also can be used with: or 
without the septic tank. As yet tried it 
does not work as well, however, as the 
remaining method we have to consider. 
V. This system of Intermittent Sand 
Filtration seems to be the most  satisfac- 
tory yet discovered where the soil is suit- 
able---sand of not too fine quality---with 
or without the septic tank. ‘The recent 
investigations made by the Institute of 
Technology point to the fact that with 
this system the sewage is better purified 
without the use of a septic tank, but that 
the care of the surface of the beds is 
greater, yet with regard to its desirability 
the Report of the Experiment. Station 
says that ‘‘ with a small plant, receiving 
very fresh sewage from a small town or 
institution, it is of great use in breaking 
up masses of fecal matter.’ 
At Lawrence they tried tanks filled 
with all kinds of soil and found that 
whereas the heavy soil, (loam, clay or 
peat) clogged badly, the “‘beds of sands 
worked to admiration, yielding a clear, 
bright spring water below,’’ (Winslow, 
page 7) andthose same tanks have op- 
erated from the dates of their installation 
to the present time---17 years. The re- 
sults of these experiments have been that 
first Framingham, then Stockbridge, 
Worcester, Brockton, and many other 
towns have followed with sand filter beds, 
until now 23 plants are in operation in 
the state. The report of the State Board 
of Health of Massachusetts on the work, 
says (S..R.‘L., page.39) ‘“‘The- ready 
availability of sand and gravel areas, nat- 
urally adapted for the purification’ of 
sewage, the simplicity of the process, 
and the small cost of maintenance, have 
made this method of purification the 
most advantageous for adoption in prac- 
tically all the cases in which sewage- 
purification works have been found 
necessary, and the resulting effuents 
turned into the stream have been satis- 
factory in all cases where the works are 
of sufhicient capacity and have received 
proper care.”” ‘The beds asa rule are 
one acre in area, and where the soil is 
suitab!e they are very simple to make. 
It is only necessary to remove the soil 
and sub-soil, which can be used for 
making the divisions between the beds, 
to dig up the sand at intervals in order to 
lay the under-drains to carry off the efflu- 
ent (the purified water ) to level the sur- 
face of the beds again and to put on them 
some simple distributer like branched 
wooden carriers or troughs of sizes so 
varied as to secure approximately uniform 
distribution. This latter is of much ‘im- 
portance, as too much sewage in any 
one place produces poor results. It 
seems from the investigations of the 
Massachusetts Institute of Technology 
that sewage could be applied to sand 
filter beds in four daily doses, greatly in- 
‘creasing the efficiency of the beds over 
what had been previously been thought 
possible. “These experiments have gone 
to prove that beds work best if dosed 
sufficiently often, but not with too great 
frequency for, as we have already seen, 
their efficiency being due to bacteria, 
good bacteria, the beds must have rest to 
allow the germs to accumulate, but not 
too much, or some will die of starvation. 
No other method so far as I can find 
out, purifies the sewage so completely as 
this of Intermittent Sand Filtration, nor 
do I believe that for us could any other 
system be so cheap. 
There would have to be in any method 
of purification an enclosed basin to col- 
