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FIG. 74.-Magnetic Filters, Messrs Allsopp's Brewery, Darwen.

untreated liquors, for from the very fact of atmospheric contact this must arise, as is shown by the following experiments by Dr G. H. Moritz :-*

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'Samples were taken in sterilised flasks, at different stages, of a brew of a light mild ale, with hops in the copper at the rate of 2.22 lbs. per barrel, as follows:

A. Directly from the mash-tub taps, at a temperature of 154° F. (grav. 1041·1). B. Directly from the copper, 15-30 minutes after the wort broke through (grav. 1078.7).

C. Directly from the copper after 2-2 hours' boil, and immediately before the coppers were let go (grav. 1087'6).

D. After the worts had been exposed on the coolers and refrigerators for some time. All the samples were forced at 80 to 85° F., and examined from time to time with the following results :

At the end of forty-eight hours

A. Swarming with bacilli and bacteria.

B. No trace of organisms.

C. No trace of organisms.

D. Fermenting briskly, and the sediment showed Sacch. apiculatus Pastorianus, and ellipsoideus forms, together with bacteria and micrococci.

At the end of ten days

A. As before, the organisms were sporulating freely.

B. No trace of organisms.

C. No trace of organisms.

D. Still fermenting briskly, with various forms of yeast and bacteria. The liquid contained 2 per cent. by volume of alcohol.

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D. Still fermenting slightly; 7.04 per cent. of alcohol present.

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D. Still fermenting slightly; 7.79 per cent. of alcohol present.

"The experiment was interrupted at this point, and a small quantity of wort, fresh from the mash tun, was added to each flask of Band C; in fortyeight hours all the flasks contained a large number of bacilli and bacteria.

"We learn from this experiment, firstly, that the wort as it left the mash tun contained a large number of organisms and spores capable of development; secondly, that fifteen minutes' boiling in the copper was sufficient to arrest the growth of these organisms; and thirdly, that the wort, before entering the fermenting vessels, contained a vast number of germs capable of development in hopped wort."

The application of brewery waste or distillery waste to land was recommended by the Rivers Pollution Commissioners, 1868, and when applied in only small quantities the natural bases of the soil will no doubt in a large measure neutralise the acidity. But when applied in large quantities, as at Burton-on-Trent, even the addition to the soil of lime as an additional base has not resulted in either a satisfactory effluent or freedom from nuisance. Laboratory Club Transactions, vol. iii. No. 2.

*

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The results given by the Commissioners (page 152) of the examination of distillery waste both before and after successful treatment on land are interesting only where there is an abundance of such land.

Now when wine is just beginning to sour, to the annoyance of the vintner, it is often remedied by the addition of sugar, and fermentation started afresh. That is to say, the activity of one micro-organism is arrested by the introduction of media suitable for the rapid development of other competitive forms.

On this principle the author patented and put in practice a method of treating this class of waste. Putrid sewage, or sewage sludge, is introduced, the active anaerobic organisms in which come into competition with the acid producing bacteria, and in a short time the action of the latter ceases; moreover, the ammonia and other unstable compounds in the sewage neutralise the acids if already present, the resulting putrid liquid becoming quite amenable to treatment on bacterial filters.

The treatment as a whole is similar to the septic treatment, but the 'septic' tank is in this case not used for the purpose of liquefying sludge, but for that of rendering inert the acid forming organisms. It is therefore better described as an anti-souring tank.

A small scale trial was first made with about forty gallons of pot ale, the following results being obtained :

RESULTS FROM TREATMENT OF POT ALE IN ANTI-SOURING TANK
AND BACTERIAL FILTER.

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*

As described by the author in a paper presented to the Inst. C. E., Feb. 1902.

The crude distillery waste was then passed through the same filter without a previous mixing with sewage, but no real purification took place. A decomposition and sedimentation, accompanied by a souring, continued right up to the fifteenth or sixteenth filtration, but at the end it was black and offensive. It appeared evident, therefore, that the presence of the bacteria in putrid sewage had some effect in preventing acidification, as in the case of the vinous secondary fermentation, and a trial was then made with starch paste only. About twenty pounds of starch were mixed with ten pounds of water, forming a paste. Half of this was mixed with putrid sewage sludge and allowed to stand one day and then examined. After the expiration of five days a further sample was examined and the mixture then passed through a bacterial filter previously matured by means of sewage only. From the table of results it will be observed that after one day's standing the difference in the composition of the mixture is little more than that due to the dilution or experimental error. After the expiration of five days, however, the change is decided. The copper oxide reduced amounts to less than one half, as does also the rotary angle. There had been, there fore, a decomposition of starch to the extent of one half or more. The remaining portion of the paste, unmixed with sewage, was unchanged in appearance, and gave practically the same figures on immersion as on the first day, but smelled offensive.

After passing the mixture, five days old, slowly through the filter once, the copper oxide was reduced to less than one-tenth and the rotatory angle to less than one-half. The albuminoid ammonia, due of course to the added sewage, was then estimated for the first time and stood at 16. The liquid was filtered again up to the fifth time, the operation extending over about two working days, and the table shows the changes in each successive filtration.

The other portion of the paste had now become sour and stinking, but otherwise thick, slimy and grey, as at first, and was passed into the filter; but up to the twenty-first filtration a satisfactory effluent was not obtained, and the activity of the filter impaired if not destroyed. The effluent was turbid, soured on standing, and gave a blue coloration with iodine, indicative of unchanged starch.

About this time Mr John Stanning, the general manager of the Bleachers' Association, Ltd., was anxious to improve the condition of the effluent at the Leyland works of the company (the purification plant at which is described in Chapter VI.), for the purpose of re-using all the effluent within the works.

The author, on the success of the experiment before described, suggested treating the worse liquors only in the same manner, and an attempt was made with kier liquors. These only amount to about 20,000 gallons per diem, but as they are produced by boiling the raw cloth first with lime and. afterwards with soda, they are very foul and concentrated, apart from the

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