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Remarks on the Analyses of the Sewage and Effluent Water from the
North Farm.-In 100,000 parts. Samples taken in the proportion of T
The sewage from the main, while containing a comparatively small amount of total solid matter in solution, contains a very large proportion of "actual"ammonia, and also of "albuminoid" ammonia, when both the suspended and dissolved matters are taken into account; it is a rich sewage whether the proportion of nitrogenous matters to the total solids or to the bulk of the sewage itself be considered. The chlorine is in fair average amount.
The analysis of the average effluent water shows that while the total solids are diminished in amount, the diminution is due to the retention by the soil and vegetation of the more volatile constituents, as the weight of ash left after ignition of the solid matters was greater in the case of the effluent water than in that of the sewage. This may be due to (1) concentration by the evaporation which takes place from the sewage of the soil and from the plants, or (2) to solution of salts already in the soil: that the latter cause is more probably the true one, we see from the diminished amount of chlorine, which, although it may not necessarily indicate dilution with ordinary subsoil water to a great extent, still would certainly not lead us to conclude that any concentration had taken place. That dilution with underdrainage water actually does take place has been already pointed out.
The amount of ammonia in the effluent water is too high, amounting to more than one seventh of that in the same volume of sewage, while albuminoid ammonia still remains to the extent of one fifth of the original amount; and the almost total absence of nitrates and nitrites in the effluent water shows the want of conditions favourable to oxidation; so that the purification of the sewage here, although considerable, is not so satisfactory as could be wished, or as might be effected by making filtration through the soil an essential feature in the process.
South Farm.-In 100,000 parts. Samples taken in the proportion of 1000 part of the flow per minute, by a measure graduated to of a gallon.
Sewage from main)
sewer at high rocks before entering the tanks on the 6th and 7th July, 1871 (temp. 62° F.), Effluent water from
field of mangolds and two fields of meadow-land, all
mixed, 7th and 8th July (average temperature 62°.5 F.)...) Water from the stream outside the farm-boundary above all the effluent drains, taken 8th July (tempera
ture 63° F.)
The results attained on the southern farm are, as shown by the above analyses, very unsatisfactory, and at the same time very reliable, as the slight diminution of the chlorine in the effluent water would lead us to believe that the loss of water due to evaporation had been about balanced by the influx of underdrainage water, so that no great amount, at any rate, of concentration had taken place.
We notice at once the large amount of "actual" and of " albuminoid " ammonia which escapes unoxidized in the effluent water. No less than four ninths of the "actual" ammonia and more than one third of the "albuminoid" ammonia, in the same volume of sewage, escapes in the effluent water, while the amount of nitrates and nitrites is very small; the effluent water is very impure indeed.
The analyses show distinctly that at these two farms, as at present man
aged, more sewage is applied than can be purified by the surface-flow, even when that takes place through thick vegetation (as in the case of the samples from the fields of Italian rye-grass on the northern farm), and much more than can be purified under less advantageous conditions (as in the case of the samples from the field of mangolds on the southern farm, although the water from this field was mixed with that from two of meadow-land); and they show, too, that the valuable matters that are not utilized are not only thrown away, but are thrown away in their crude condition, not having been subjected to the oxidizing action necessary to convert them into innocuous nitrates and nitrites.
Lastly, we must notice the fact that the temperature of the effluent water of the northern farm is only slightly (less than one degree Fahr.) below that of the sewage, while the effluent water of the southern farm is actually half a degree Fahr. warmer than the sewage. This clearly shows that the sewage has not been subjected to the cooling which percolation through soil entails.
(b) Observations on the Sewage-Farm at Earlswood designed for the
This sewage-farm consists of about 70 acres of Earlswood Common, of which, it was stated, about 50 acres abutting on a tributary of the river Mole have been laid out for irrigation. It is intended very shortly to add more land to that already prepared from properties adjacent.
The soil is for the most part a clayey loam. The higher ground next the Common is rather freer in character, while the lower part appears to increase in density as it nears the outfall.
The surface, which has rather a steep fall in its higher part, gradually becomes more level as it descends, and has a very slight fall indeed as it approaches the outfall.
Before the sewage is delivered to the land for irrigation it passes through one of Latham's patent extractors, an ingenious invention for the separation of the solid from the liquid parts. The liquid sewage is delivered from the extractor by covered conduits, from which it is directed right and left into the highest carrier. The land laid out for irrigation is divided into three series of beds or slopes separated by roadways, on the upper side of each of which is a surface-drain to receive the effluent liquid as it passes off the beds above, and on the lower a main carrier to deliver the sewage for distribution to the series of beds below. The three series are divided rectangularly into nearly equal-sized blocks, to be again subdivided by minor or inner carriers, laid out partly on the catchwater and partly on the ridge-and-furrow form. The surface of the highest land of the uppermost series of beds is about 24 feet above the surface of the lowest land in proximity to the outfall-stream. None of the land is underdrained, and the lowermost beds appear to be incapable of underdrainage at a sufficient depth unless the stream receiving the water to be discharged is appropriately deepened at very considerable cost. In answer to inquiries, it was stated that after heavy rains the lowest portions of the irrigated lands are swamped by the backing of the water which collects on their surface when the soil itself is in a state of complete saturation. At the time of the inspection by the Committee (July 11th), the sewage had collected in pools on the surface of the irrigated beds in a manner injurious to the crop under treatment. The work of irrigation is designed so that the sewage applied to the higher land may be reapplied on the sur
face of lower lands with a view to its further purification. The sewage as it passed off the first surface was observed to be far from clear to the eye, and it was not perfectly so when leaving the second surface. When it was ultimately discharged at the outfall it was still cloudy, but this was partly accounted for by the heavy rains of the previous day. The analyses of samples of effluent water taken at different points, hereafter referred to, will show the extent of purification effected.
Though the land had not been drained, it gave indications of a natural capability of drainage in the escape of the sewage from the sides of the carriers or drains, which are from 10 to 14 inches deep. The line of saturation was clearly shown in those shallow cuts to be nearly identical with their depth, and the liquid was seen oozing out of the land at some parts in a clarified condition, and at others accompanied by a slimy matter, some specimens of which have been microscopically examined by Mr. M. C. Cooke, M.A., whose report is here given.
Microscopical Examination of Slime and Mud from Bottom and Sides of Carriers at Earlswood Farm.
The fluid specimen of deposit sent to me for microscopical examination was the only one in a fit condition to report upon as to "the insects and animalcula to be found therein." Obviously dried mud would give no satisfactory result as to living animals, since the majority of them would be dead and shrivelled beyond all power of determination.
I have examined the wet deposit by the aid of the microscope, and find it to contain a few Diatoms belonging to several genera and species, but in a comparatively small proportion to the volume of material. The Desmidiacea were also represented by a species of Closterium, of which I detected but a few individuals. Confervoid threads were also but sparingly scattered through the mass. Altogether there was a smaller percentage of unicellular Algae than I expected to have found. Living vegetable matter was comparatively rare.
The animal inhabitants of the mud were numerous, especially of certain kinds. There were a few examples of that common Thysanurous insect, Achorutes aquaticus, sometimes so plentiful in the liquid draining from heaps of manure. The larvæ and pupa of small Diptera I am unable to name in those stages, but their proportion was not large. Of Euglena viridis there was no lack; and any stagnant puddle, especially in the neighbourhood of farmyards, would have yielded an equal proportion. Infusorians were scarce; a few solitary individuals of Vorticella microstoma, and one or two specimens of Paramecium, were about all that I observed. But there was one group of animal organisms most abundantly represented, and these were the Annelids. When the mud was exposed to the light and sun, the surface became active with these creatures; about the diameter of a piece of cotton-thread, and from half an inch or less to nearly 2 inches in length, they wriggled over the whole surface. Some white, others pink, and a few of a deep blood-red were mingled together like eels, wriggling and scriggling in every drop that could be taken up and placed on a slide for examination. Skins without inhabitants were almost as plentiful; and it seemed to be impossible to get a drop of the material in the field of the microscope without either the worms themselves or empty skins. (Signed) M. C. COOKE, M.A.
It appears to the Committee that the existence of the exuded matter described by Mr Cooke is mainly, if not wholly, due to the fact that the subsoil is kept in a saturated condition by the want of underdraining; and they desire to add their belief that with land thus saturated with sewage certain atmospheric conditions exist which may be attended by malaria more or less injurious to health. It need hardly be said that if the effluent liquid passing from a sewage-farm at a time when vegetation is in a luxuriant state, and when evaporation is more than ordinarily active (which was the case when
the Committee viewed the land), is not clear to the eye nor sufficiently pure to be admitted into rivers, there must be times when it may become exceedingly objectionable.
It is to be remarked in this case, moreover, that there was (on July 15th, 1871) more liquid passing off the land at the outfall than there was sewage delivered to it for application, due possibly to the passage of the recent rainfall through the porous soil of the higher part of the farm. This fact would, in the absence of the analyses of Dr. Russell, have led to the conclusion that the effluent liquid was purer than usual.
Observations on the Analyses of Sewage and Effluent Water from the
In 100,000 parts. Samples taken 14th and 15th July, 1871, in the pro-
This is decidedly a weak sewage, as it does not contain one third of the quantity of "actual" ammonia, nor one fourth of that of "albuminoid" ammonia that the samples of Tunbridge Wells (North Farm) contain; the