PROCEEDINGS OF SECTION H. 681 
process combining crude cake alum, blood, and clay, generally 
known as the A.B.C. system. More recently experiments have 
been made with a process combining milk of lime and herring- 
brine. Of the various processes enumerated, Jime, in conjunction 
with sulphates of iron and alumina, has, according to latest 
accounts, given good results as far as a precipitating agent, but 
no claim has been set up as a purifying agent; it has, however, 
been claimed by the patentees of the process known as lime 
combined with herring-brine, that a high standard of purity, as 
well as efficient precipitation, has been obtained. 
In a paper* read by W. J. Dibden, Esq., F.C.8., of the Metro- 
politan Board of Works, on the disposal of sewage sludge, he 
states that “the use of an excessive quantity of lime, whilst 
having a temporary antiseptic action, is objectionable, by in- 
creasing the quantity of putrescible matters in solution in the 
effluent. One object claimed for the use of an excessive quantity 
of lime, and also for some other substances, is that they destroy 
the living organised bodies, such as bacteria, &c., which give rise 
to the phenomena known as putrefaction.” Mr. Dibden considers 
this question of such importance that he discusses it at some 
length ; and as it opens up fruitful ground for consideration, his 
opinions are given as recorded. Mr. Dibden states the researches 
of Warringtont have demonstrated that the process known as 
nitrification of the complex nitrogenous bodies existing in sewage 
during its filtration through land is brought about by definite 
organisms, who in their life processes feed upon the sewage 
matters and evolve the nitrogen in the form of nitric acid. 
As with the nitrogen, so it is with the carbon, which is 
absorbed as food and evolved as carbonic acid. Without these 
life processes, whether they be of an animal or of vegetable 
nature, no destruction of the objectionable matters can take 
place. As the very essence of sewage purification is the ultimate 
destruction or resolution into other combinations of the unde- 
sirable matters, it is evident that an antiseptic process is the very 
reverse of the object to be aimed at. If a preservative process be 
required, a receptacle should be provided for the preserved 
matters, and in order to ensure that the antiseptic process should 
be a continuous one any subsequent treatment or method of 
disposal must avoid the destruction of the antiseptic employed. - 
In the case of lime, which in strong solutions is a solvent of 
organic structures, what time will elapse before its neutralization 
by absorption of carbonic acid, and consequent loss of antiseptic 
properties, after the discharge of the effluent into running water ? 
Obviously, only a very limited period, after which the growth of 
organisms so zealously destroyed will recommence, by reason of 
the numerous spores in the water of the river and with the air 
* Volume LXXXVIII.; Minutes of Proceedings of the Institution of Civil Engineers. 
+ Journal of the Chemical Society, Vol. XLV., 1884. Transactions, p. 637. 
