Specification of Henry Young Darracott Scott : treating sewage water.

  • Scott, H. Y. D.
Date:
1872
Catalogue details

Licence: Public Domain Mark

Credit: Specification of Henry Young Darracott Scott : treating sewage water. Source: Wellcome Collection.

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    Scott's Improvements in Treating Sewage Water. in consequence of the large volumes that will have to be dealt with, and their unceasing flow in most cases from the sewers, and the processes alluded to have not extracted a sufficient quantity of ammonia to justify the expense of the treatment. The mode of operation which I adopt is this :—I take phosphate of 5 magnesia in a fine state of division (by preference in the form of a paste and prepared in any convenient manner) and agitate the ammoniacal liquid to be treated with it in tank No. 3. The result is that the phos¬ phate of magnesia removes from the liquid the ammonia with which it is brought in contact. 10 The conditions necessary to ensure success are (first) that the phos¬ phate of magnesia shall be in the hydrated and not the anhydrous condition, as this salt, after ignition, shews so little tendency to unite with the ammonia as to be practically inefficient; second, that the phosphate of magnesia shall be present in sufficient quantity and in such 15 excess as to render the whole liquid treated what may be termed milky, for if introduced in sufficient quantity only to combine chemically with the ammonia present in the charge under treatment, the amount of ammonia extracted will, with any feasible amount of stirring or oppor¬ tunity for subsidence, be insufficient to repay the cost of the process. 20 This will be readily understood, for although substances capable of forming new chemical compounds will at once unite when mixed together in a state of solution in their proper combining proportions, this result is hardly to be expected when one of the substances is in a solid form, and in order to secure anything like an efficient removal of the ammonia 25 from its dilute solutions it is necessary that the liquid should be crowded (so to speak) with active particles of the solid substance. Even when such a superabundance of the phosphate salt is present the whole of the ammonia will not be extracted in one, nor indeed will every trace of it be removed by several operations similar to that above described, and 30 therefore where possible it is better to employ a second, or even a third phosphate tank, which I may call No. 3a and 3b, wherein the effluent from No. 3, after the solid particles of ammoniacal phosphate of magnesia and the unused (if I may so express myself) phosphate of magnesia have subsided, may be agitated with a fresh charge of the magnesian phos- 35 phate. After these tanks have been refilled and emptied several times, the waste of the magnesian phosphate being made up by fresh additions of that salt introduced from time to time, the deposit is to be collected,