Land Treatment of Sewasre. 



partially separate, and all the storm water reaching 

 the sewers is dealt with on the farm. As the volume 

 of this is at times very considerable, it is obvious 

 that the regular working of the farm must be mate- 

 rially interfered with, and this may account for the 

 fact that the effluents varied in quality to a consider- 

 able extent. We are of opinion that 57,100 gallons 

 per acre per twenty -four hours (9,500 per acre of 

 the total irrigable area) is too large a volume of 

 even a medium-strength sewage to be treated by 

 screening and surface irrigation even over such a 

 porous soil. The volume of sewage dealt with per 

 acre of the ' working ' daily irrigable area was very 

 large, owing to the ' resting ' area being five times 

 the ' working ' area. The bacteriological results 

 were, generally speaking, less satisfactory than the 

 chemical. The fact of the Beddington soil and sub- 

 soil being fairly comparable in quality with those at 

 Nottingham and Cambridge, taken together with the 

 filtration results obtained from the ' special experi- 

 ment,' leaves no room for doubt that the above- 

 mentioned volume of sewage could be satisfactorily 

 treated if Beddington were laid out as a filtration 

 farm." (Part I., page 87.) 



LATER WORK. 



In 1901-2 a pumping station was erected to deal 

 with the dry-weather flow only from the Norbury 

 sewer. The sewage was directed into seven bac- 

 teria beds, each 226 ft. by 56 ft., filled with coarse 

 gravel to a depth of 4 ft. They were worked upon the 

 contact principle, and were fitted with automatic 

 gear for filling and discharging. In 1902 two tanks 

 were added, each 125 ft. by 22 ft. by 12 ft. deep, and 

 subsequently a further tank was built, 125 ft. by 

 56 ft. by 12 ft. deep. The sewage flowed con- 

 secutively through these tanks before reaching the 



contact beds. In 1904 these arrangements were 

 condemned, and their failure was attributed in large 

 measure to the improper method of working. A 

 small experimental continuous filter, one half of 

 which was gravel and the other half clinker, has 

 been in use for some little time. The population 

 has considerably augmented, and at the present 

 time the sewage from over 85,000 persons is dealt 

 with at the Croydon outfall and over 35,000 at the 

 Norbury outfall. The works at the Norbury outfall 

 are in course of reconstruction. The beds are being 

 divided into four sections each, and twenty-eight 

 sprinklers will be employed to distiibute the sewage 

 after passing through the tanks, which will be 

 worked more or less on the septic principle, being 

 cleaned out about once a month. A new 15-in. cast- 

 iron main will be laid to an area of 44 acres, not 

 previously irrigated, at a distance of Ij miles. 



The following works have been planned for the 

 treatment of the sewage from the Croydon outfall : 

 A diversion of the main outfall sewer to a screening- 

 house ; three tanks (for the ordinary flow) of a total 

 combined capacity of 600,000 gallons ; twenty- four 

 continuous filters, each 80 ft. diameter by 6 ft. deep, 

 to be filled with gravel and clinker ; a main to 

 convey the sludge to various fields on the farm ; the 

 utilisation of about 45 acres of additional land ; and 

 three tanks, also 600,000 gallons capacity, to deal 

 with storm water, which after passing through them 

 would return to the old culvert and be treated as 

 heretofore. 



A large number of dairy cows is kept, and in this 

 manner the bulk of the rye-grass can be disposed of. 

 Formerly there was a good market for this typical 

 sewage farm product, but of late years it has steadily 

 declined. 



34 



