The Dorset County Express and Agricultural Gazette.
Dorchester, Dorset, England, 1885-03-17 00:00:00

SEWAGE TREATMENT BY INTERMITTENT
FILTRATION.

The Builder of Saturday last contained an article on
Mr. Denton's whene of sewage treatment by Inter
mitterit Fi!intim and which has mosived • favourable
report from the Royal Oommlestooses, on the ground
first that the proems has gnat scientific merit, and
offers valuable practical &debate's' for the disposal
c±Lemin situations whs. Mood irrigation is ice-
and where land suitable for filtration can
oblat;d.
Intermittent filtration is explained by Mr. Denton
to he "not crowding sewage ototlationsly on porous
land in the conies' manner often adopted to gst cid
of sewage, but it. oommetration an regulated lot-realm
on as few acres of land as wCI absorb and ri wise it
without preventing the production of veretstion. It ,
Is by this means that the satimilatlvi powers of
growing plants are brought to bear on the fertilising '
elements of the sewage at the fame time that the pm,
oolation of the sewage through the soil brings it in
waterOt with the atcompharia air pervading the soil,
and renders it harmless by oxidation."
In this it is distinguished from what is termed
broad or surface irrigation, which °lodate rath-r In
the distribution of sewage over ae many sores as it will
wet without supereaturstion, baying In view a
in 'riotous plant growth.
Mr. Denton olaims for his proems the advantages
of : —l. That when adopted sepiretely it will, by
mialmking the quantity of lend required, ensure the
purification of .wa e at the least oast to the rats.
psywr ; and 2.—When eysts maticallhadopted in °ow
bination with surface irrigation. It may be made the
MOMS of removing tb• greatest drawbacks experienced
by the sewage farmer, sad thus afford • tangible
benefit t agriculture. In hist thyr Tydfil the return
obtained front 336 agree over and above the expend!.
tare was £452 Sr. 7. In Ablagdon toe whole of the
farm was let for Et 104. per acre. In Forfar, after
charging 4 per cent. on £4,000, the parchaw-money of
the lent as well as on £1,500, the exp.. of the
engineerineworks, there w..& net profit of El 131. 61.
per acts. In Great Malvern the district amounts for
last ye show that there was a balsam, in favour of
the farm at £162 15.. IcL, which was carried to the
°relit of lb* district rate. On the other hand, at
Watford, in Hertfordshire, there hes not been the
: same financial sumws, owing. it II atatod, not g., any
fault in the aystem, but to the candied mo le in which
It was carried out, olteckieg the miiration due to tits
wider-1r.., and to tie sewage heel( h swing bee.
atirlied without the required intermittency. Toe
car tinsl points to be observed in the promos are ex-
plain, I to be :-1. The preparation and f irmation
of the Iliad which is intended to receive the esiwage,
"nth precision. Irregular surfaces sod steep slopes
are to be ay.dds I seen more carrfolly than eay soils.
2 —lnter.nittency of application and regulation of
quantity, the former Laing positively essential to
some a cootioued gms.l effluent. 3.—The nodist•
drainage of the filtration arras should be laid out as
o irefully as practical science will 'opted, so as to
'Enure drawing the Iquid 'wage clown from the
surfaci4 only through the prepare! ground. With •
view to prove ite financial soundness, a Leila is given
showing the oompa-ative expenses of laud treatment
and chemical preoipitatioo, in the asses of Abingdon
and Habit...ad on the one band, and Aylesbury and
; Hertford on the other, from which it appears that in
the last two town. the annual charge on the ret-payers
la 14.7 I. awl 2.. 111. per bead. while in the tar., others
it is only la. 01i. and Si. per bead of the popuLtioc.
So far, then, mays the Builder, the press' of lister-
mitt .nt downward filtration scoots to afford a pract'cial
solution of the disposal of sewage as far as combioing
efficiency with economy. Why, then, it will naturally
be asked, is there any hesitati on to recommend its
adoption In the c.a. of the metropolis 7 The Royal
Commiesloners evidently think well of it, though they
have pronounced rather in favour of II Combination
of chemical with lend treatment—that is, of precipi-
tation supplemented by application to lent—as the
plan which offers the most feasible opals of solving
the difficulty.