Cambridgre. 



Treatment 

 and Cropping:. 



Treatment. — The farm is divided 

 into plots of a convenient size, 

 ranging from about 3 acres to 

 6 acres each, and they are laid out perfectly level, 

 the carrier embankments forming an enclosure on 

 three sides and the remaining side being banked up 

 or fendered to retain the sewage, which is only 

 treated once through the land. " The practice 

 followed in irrigating is to flood the sewage on to 

 the plots from the carrier outlets, running it on 

 continuously night and day for about four days to a 

 week, the plots then being allowed to dry as long as 

 possible. In the case of two fields (Nos. 4 and 11) 

 which are used as natural filter-beds, manholes and 



is used and only a portion of a plot utilised 

 for sewage." (Part IV., page 45.) Cropping. — 

 Very few crops are grown on the farm ; kohl-rabi, 

 mangolds and horse-corn are cultivated and the 

 produce is sold. A large portion of the farm is 

 always uncropped — i.e., the soil is mainly used as a 

 bacterial filter. 



The sewage is rather weak and 



Analyses— arrives at the farm well broken 



' up. Although there is only about 



half an hour's settlement in the 



one tank at the farm, some 35 tons of sewage sludge 



are obtained each week. The chief Ohemical results 



CHKMICAL ANALYSES (PARTS PER 100,000 BY WEIGHT). 



Total nitrogen 



Ammoniacal nitrogen . . , 

 Total organic nitrogen 



Albuminoid nitrogen ... 



Oxygen absorbed 4 hours at 80 deg. Pahr. 



Nitric and nitrous nitrogen 



Chlorine (in water supply 1*91, and in subsoil 

 water 1-60) 



Incubator test as judged by smell 



Solids in suspension (hourly samples only) 



Sewage.* 



4-60 

 2-94 

 1-51 



0-73 

 8-15 



715 



26-5 



Effluent. 

 (17-18 samples.) 



2-09 

 0-65 

 0-21 



0-09 



0-81 

 1-26 



7-55 



86'6 per cenf) 



purification f 



(average) ) 



89-75 percent^ 



purification f 



(average) ^ 



94 per cent 



passed 

 (18 samples) 



Stream. 

 (2 samples.] 



0-61 (?) 



0-025 



0-085 



0-035 



0-475 

 0-5 

 206 (1 sample) 

 Sweet 



' Approximate averages of three sets of samples drawn in eqnal quantities per hour for twenty-four hours and of five chance samples. 



penstocks are provided by means of which the 

 sewage can be held in contact with the soil for 

 some hours. These plots are sewaged continuously 

 for about six hours a day. Some plots which have 

 been sewaged longer than others will not pass so 

 much sewage owing to the scum formed on the 

 surface, and therefore the sewage has to be shut off 

 sooner from them, and other plots with less scum 

 receive the surplus sewage. The surface scum has 

 a beneficial effect, by checking filtration when the 

 plot is becoming sludged up and so preventing the 

 land from becoming sewage sick. When the land is 

 sufficiently dry to admit of it, a light spring scarifier 

 has been found of great assistance in breaking up 

 this surface skin of sludge. Occasionally a stank* 



* By stank is meant a small embankmant, or fender, to retain the 

 Beware within certain limits. 



" The effluents were partly clear and colourless, 

 and with no sediment, these being as a rule the 

 effluents from special plots ; partly slightly opales- 

 cent and of a brownish tinge, with a little red, brown 

 or grey flocculent matter, and in two cases with a 

 considerable green deposit ; partly rather turbid, 

 this turbidity being no doubt mostly due to the 

 separation of carbonate of lime from solution. The 

 dimness was not, however, a criterion of purity or 

 otherwise. Samples Nos. 204 and 205 were both 

 dim, but the first was good and the second bad. All 

 of them had a clean smell when they came to be 

 analysed, though in two cases it was fishy, and in 

 five others slightly fishy. The reaction was alkaline. 

 Two effluents were tested for lime in solution, and, 

 as was to be expected, a very large quantity of this 

 was found to be present, together with a consider- 



25 



