Sewage Disposal and Rivers Pollution. 
345 
For the Metropolitan Board of Works had fallen into the hands 
of the advocates of purification by chemical precipitation, and 
between these and the advocates of some form of irrigation or 
filtration through land — broadly speaking, between the chemists 
whose services might be required to advise on chemical treatment, 
and the engineers who find their account in laying out sewage farms 
and filtration areas — has long raged a bitter though highly 
unreasonable warfare — profitable, no doubt, to the combatants, but 
certainly hampering to the progress of sanitation. The unreason 
is now beginning to be felt on both sides, for the process of trial 
and error above alluded to has shown that the rival recommend- 
ations are not so much antagonistic as supplementary. On both 
sides similar extravagant expectations have been held out, which 
time has shown to be illusory. The advocates of irrigation claimed 
that the application of excretory matter to land was the natural 
and only perfect method of rendering it harmless, and therefore 
the only way of preventing the pollution of our rivers ; that 
the throwing away into the sea of the fertilising ingredients of 
millions of acres was a shameful waste ; and that by the restoration 
of these to the land a profit could, and ought to be, obtained. Even 
on this question of waste there is a pro and con. For experts 
interested in the sale of artificial manures were not long in dis- 
covering that, although too much sewage in our rivers may kill 
fish, the fish at sea have claims on our bounty, and that sludge or 
sewage carried out to sea is literally bread cast on the waters, 
returning to us after many days ! 
The position taken by the chemists was that irrigation could 
never be made to pay ; that in addition it was often a nuisance or a 
failure ; and that by chemical precipitation alone an effluent could 
be procured sufficiently pure for discharge into any river, whilst the 
hope was held out that by the sale of the precipitated sludge 
sufficient of the manurial value of the sewage might be recovered to 
render chemical treatment the least costly method of dealing with 
sewage. 
Experience, now considerable, of both methods has left neither 
position intact, whilst allowing some truth to each. Filtration of 
sewage through soil, when that operation can be secured, has, 
indeed, held its ground as the most perfect means of purification. 
No precipitant, or combination of chemical nostrums, has been 
successful in securing as sweet and pure an effluent as that which 
has really passed through the pores of the soil. And there are 
many instances, especially in the case of small towns in agricultural 
districts, where simple broad irrigation, 1 intelligently managed, has 
proved both adequate and economical. Where a large acreage of 
suitable land, otherwise worthless, can be secured, it has even 
proved a financial success on a large scale. As a case we may quote 
Dantzig, with a daily sewage flow of over 3]- million gallons per 
24 hours, disposed of on “dune sand ” : — 
1 Better with a preliminary screening through a layer of very coarse 
material. 
