MODERN METHODS OF WATER PURIFICATION. 325. 



Stance we were indebted to American work, and as the Ameri- 

 can rivers have so much more turbidity than English rivers, 

 I made up my mind to make use of my leave, not merely to 

 see what I could see in Britain and Europe, but to go to the 

 United States, and there I found exactly similar water precipi- 

 tation problems to those with which we have to contend, and 

 being from year to year tackled more and more successfully, 

 and with progress all the time. 



Where so important a matter as securing greater purity of 

 our water supply is concerned, and with the best approved and 

 most efficient methods combined with economy, it was my 

 endeavour to gather knowledge to further that object in all 

 lands, and particularly in the United States where so much 

 ability and energy is being devoted to new methods by some of 

 the foremost water engineers and scientists in America, 

 possibly in the world. There is a greater diversity of water 

 in the United States than is found in Britain, and the waters 

 in the North — in New England — are not very like ours, the 

 Modder River, as they flow through glaciated' sandy regions. 

 But the Ohio, Mississippi, Missouri, Susquehanna and, to a 

 less extent, the Potomac, carry, just as the Modder River does, 

 a quantity of finely-divided clay, in such colloid suspension 

 that it can be said of them, as of the Modder's turbidity, that 

 at times it wdll. practically, never clear by simple sedimenta- 

 tion in tanks and sand filtration. After what I have seen in 

 the United States, I am more convinced than ever tnat there 

 is-one known method, and only one, by which the water of the 

 Modder River, with its extremely fine clay particles, can be 

 cleared and purified, and that is by chemical precipitation as 

 the first step in the treatment. 



This is the opinion held of similar waters by such great 

 authorities in America as Hazen. Fuller, etc.. the former of 

 whom, in the course of a very instructive and interesting" con- 

 versation 1 had with him in New York, said: " There is only 

 one way to deal with such water — ^chemical precipitation. 

 Without that, no amount of filtration — single, double, or multiple 

 — will do it, and with that properly carried out, the simplest 

 system of filtering will render the water pure." This is the 

 opinion of a man whose opinion is so valued that he was called 

 from America to Australia to advise on water purification. 

 Mr. George W. Fuller, another famous American water ex- 

 pert, says : With coagulation (chemical .precipitation) we can 

 use the most rapid mechanical filter and get pure water, with- 

 out it, in the case of turbid rivers, purification is most difficult. 

 Hazen and Fuller are not alum merchants, but eminent water 

 experts. They occupied (one succeeding" the other) the post 

 of Experiment Director at Lawrence, Mass., w^here the monu- 

 mental work on sand filters was done, and therefore started 

 as sand filter men. 



Of course there are different classes of experts, and also 

 all authorities do not hold identical opinions, but the men 

 quoted hold these opinions, and they are men to follow, as 

 their experience has lain with waters of the character of the 

 Modder River, but with great rivers instead of small, and bisf 



