THE DRAINAGE QUESTION.

Globe, Volume XXIII, Issue 2249, 13 May 1881, Page 3

THE DRAINAGE QUESTION.

The following letter from Dr Nedwell will be laid before the Drainage Board at its next meeting : The Chairman, Board of Health. Sir, —It is quite clear that there is a good deal of difference ef opinion among the ratepayers of the Christchurch Drainage District on the merits of the water carriage versus the pan system of excreta removal, although one might have thought that Mr Clark had settled this for ns three years ago. I have no new ideas to bring forward, and write only with the hope of confining the controversy within legitimate limits, stating facts and avoiding theories, having no particular bias one way or the other. Mr Clark advocated the water carriage of excreta for the district, and went so thoroughly into the subject that I trust his report will be re-read by the public. Deep sewers, Mr Clark said, were necessary to carry away our refuse water, and for the disposal of this liquid filth he recommended filtration and irrigation over the Sandhills to the east ef Christchurch. To carry it so far out into the deep sea as would prevent its being washed back and becoming a nuisance, was a plan, he said, too expensive, and it could not be taken to the Estuary for the simple reason that it would there be generally agreed that in small communities and for isolated houses nothing can be better than the dry earth system of night soil removal. Wo have a pan system certainly in Christchurch, but it is of such an imperfect character that to continue its use we must go to a good deal of expense.

While very much can bo said in favor of this system, it is only fair to hear what the Rivers Pollution Commissioners say about it. Remember “the difficulties of the plan when not fifty but 50,000 householders have to be provided with the necessary appliances, and induced to work * them properly, and we can have no hesitation in pronouncing the dry earth system, however suit- * able for institutions, villages, and camps, where 0 personal or official regulations can be enforced, 1 entirely unfitted to the circumstances of large i towns.” But the earth system of excrement a removal does not supersede the necessity . for an independent means of removing 1 slops, _ rain water, and soil water. The j questions now arise is excreta to be admitted to our sewers when we have them, and is our sewage to be deported at the_ sandhills? Let the ratepayers answer both questions in the j negative if they like, but let them be aware of what can be said on the other side. Dr. Buck, writing in his work on " Hygiene and Pnblio Health,” says with regard to the admission of excreta —“ The difficulty really resolves itself into the treatment of aa increased volume of sewage required where water-closets are in use. It is simply a question of additional expense, which, as an objection, falls, when the cost of a separate system for excrement removal is taken into consideration. If all the details of the system are thoroughly carried out under the best engineering skill, sewers cannot bo hurtful, even with the addition of solid excreta, which do not materially increase the impurity of the sewage.” With regard to the disposal of our liquid filth, with or without night soil, let us see what can be said on the subject of filtration and irrigation at the Sandhills. Dr. Corfield, Professor of Hygiene and Public Health at University College, London, says—" That by careful and wellconducted sewage irrigation—especially with the application of moderate quantities per acre, the purification of the whole liquid refuse of a town is practically perfect, and has been ensured in cases where it was not at all the object of the ' agriculturist; and that it is the only process ' known by whi h purification can be effected on a large or small scale,” “ That perfectly worth- i less land, blowing sea sand for instance, can bo ; be made in this way to support large and valuable crops,” Mr Rawlinson, chief engineering inspector to the Local Government B mrd of England says— 1 “ With respect to the injurious charges brought ( against sewage farming inquiry, experiment and j experience disprove them. With respect to the t milk and butter obtained from cows fed on 3 sewage grass, chemical analyses and continued use prove that both the milk and butter are good in quality. Vegetable produce from a sewage J farm differs in no way from that grown under ' so called solid manures, other than by being 1 more abundant and in somerespects better. There 1 are plenty of sewage farms now in active opera- ] tion which answer the objections and again, t “ Continued irrigation with foul, corrupt sewage e in excessive volume for very many years, aa at ( the Cragintinney meadows near Edinburgh, has failed to produce a sewage swamp, to corrupt the soil, or to produce malaria injurious to health.” Dr. Buck, before quoted, says there is ® “no well-substantiated proof that such diseases as ' cholera, typhoid fever, dysentery and allied affec- 1 tions are produced by effluvia from these farms.” t De Chaumont, editor of “ Parkea’ Hygiene,” I asserts in the light of present experience, “ that t the effluvia from a well managed sewage farm do t not produce typhoid fever or dysentery or any ] affection of the kind.” 1 Amongst other important experiments carried J out under the Rivers’ Pollution Commissioners, c it was found that in the filtration of sewage t through sand “ the suspended matters were en- * tirely removed, and that the organic carbon c and nitrogen were greatly reduced,” and it is known that for filtering purposes 0 soils composed of “sand, or a mixture ’ of sand and chalk are very effectual.” p According to the report of the Commissioners t “ those experiments also show that the process o of purification is essentially one of oxidation, the organic matter being to a large extent con- Q verted into carbonic acid, water, and nitric B acid. Dr. Cobbold thought at one time that entozoa might be conveyed to man through cows feeding on sewage farms, but he J now says his fears were groundless. Dr. ” Wilson, one of the most eminent sanitarians b of the day, thus expresses himself on the sub- t ject in his work on “Hygiene”:—“ It is now a generally conceded that this is the only process t which fully meets all the requirements attaching g to the disposal of sewage ; in other words, it is f the only one which, while it purifies the sewage, fl efficiently realises the highest profits, and may j be carried on without creating any nuisance or detriment to the health of the neighboring in- , habitants.” “ Yonrs, &e., * Courtney Nedwili,. e