EXPERIMENTS ON SEWAGE DISPOSAL IN GERMANY in 
The conclusions which the Government experts who made the investigations 
arrived at may be stated as follows : — * 
(1) Gravel, or gravel with brick breeze, is not an efficient medium ; coke of a 
definite size seems to be the best. 
(2) Two hours is the best period for contact. 
(3) Settling for 24 hours for ' septic' action is of no import. 
(4) Cold ( — io° C.) does not interfere with the action of the beds. 
(5) Aeration is necessary. 
(6) The reduction in the number of bacteria is of no appreciable importance. 
Consequently the effluents, if they are to enter streams, require similar precautions and 
treatment to merely settled sewage. 
Whilst the conclusions seem quite correct, it is evident from the protocols 
of the experiments that these filters were not so efficient as they can be made. 
Taking, for example, an experiment from the sand and coke bed after it had been 
working three months (Experiment III), the following numbers were obtained on 
analysis : — 
Ammoniacal 
(Nitrogen in 
Organic 
mgr. p. litre) 
Nitrate 
Nitrite 
O absorbed 
Mgr. p. litre 
Crude Sewage 
Effluent (after two hours) ... 
7 3 
14 
•3 
0 
O 
2 

O 
present 
H5 
2 3 
The absence of organic nitrogen was quite exceptional, and, although in this 
case the effluent was clear, it was by no means always so ; and occasionally it was 
putrescible. 
No. of bacteria 
Ordinary gelatine 
Kl-gelatine 
Crude Sewage... 
2,700,000 
2 10,000 
Effluent (after two hours) 
225,000 
10,000 
In many cases the plates of ordinary gelatine had liquefied (through insufficient 
dilution) ; the Kl-gelatine is used to indicate the numbers of B. coli. 
