112 
THOMPSON YATES LABORATORIES REPORT 
2. CLOSED SEWAGE TANK 
Gu. Lichterfelde (near Berlin).* (Extracted from Official Report). 
This experimental installation was worked for over a year and then dismantled. 
It was merely a modification of Cameron's system, and the effluent was run on to a 
contact bed. The investigation was conducted by Government officials, and the 
inventor was subsidised. The bacteriological and chemical analyses extended over 
nearly the whole of the working period. The results do not differ essentially from 
those obtained elsewhere. The alteration in quantity of solids in suspension in the 
effluent is not recorded ; the total solids increased rather than diminished. 
On dismantling the closed tank it was found that sludge had accumulated 
to the extent of 13.32 cbm., the total capacity of the tank being 90 cbm. The sludge 
did not differ chemically from that obtained from fresh sewage. Consequently no 
' mineralisation ' bad occurred. The dilute nature of the sewage accounted for the 
sludge not having made itself very evident during the working period. In another 
installation the sludge had to be removed twice within six months from the tank. 
The experiment showed the possibility of dealing with the sludge of a dilute 
sewage for a certain time without nuisance ; and the system may be useful for 
hospitals, barracks, &c. 
These results are hardly so good as those obtained in England. But they all 
point in the same direction, viz., that, except to avoid smell, the closed presents no 
advantage over the open sewage tank, whilst it is considerably more expensive, and it 
does not in many cases dispose of the sludge in the effectual way that was expected 
and affirmed. 
3. THE LIGNITE PROCESS (Rothe-Degener Patent) 
Potsdam and Tegel 
I do not know of any similar process in use in this country. The sewage 
is first mixed with crushed lignite and then precipitated with ferric sulphate. The 
sludge settles and the effluent is drawn up into a Rothe-Roeckner tower. The 
former is drawn off from below, pressed, and finally used as fuel in the boiler furnace ; 
the latter is mixed with a small quantity of bleaching powder, and, thus sterilised, is 
run into the river. The free chlorine can, if desired, be easily removed by filtering 
through a shallow bed of coke or gravel. 
* Op. cit. pp. 288 et seq. ; also 1898, Suppl., pp. 99 et seq. 
