888 EXPERIMENT STATION RECORD. 



Sewage treatment in small communities where a sewerage system is not 

 available, P. Ha>-.sex (/?/. Health News, n. set:, 1 (1915), No. 11, pp. 179-18^, 

 fiijs. 5). — This article describes and diagrammatically illustrates a type of com- 

 mon settling tank, a small Emscher double-deck or two-chamber tank, and a 

 tile absorption system for the disposal of residential or farm sewage. 



"Xo part of a subsurface drainage system should be within 200 ft. of any 

 well, assuming an ordinary gi*avelly or sandy soil. If limestone is near the 

 surface, the danger to wells is infinitely increased. However, the subsurface 

 irrigation system is of far less danger to wells than is the ordinary leaching 

 cesspool. This device is an abomination that should not be permitted in any 

 built-up community, for it is almost impracticable to keep them at a safe dis- 

 tance from shallow wells." 



Economy of deep percolating fi.lters, H. W. Clabk {Surveyor, 48 {1915), Xo. 

 12^5, pp. 5^0, 541, figs. 2). — Recent experiments made at the Lawrence, Mass., 

 experiment station on the efficiency of four trickling filters 4, 6. 8, and 10 ft. 

 deep, respectively, are reported, each filter being operated at rates of 500,000, 

 800,000, 1,000,000, 1,.500,000. and 2,500,000 gal. per acre per day. Salt was 

 added to the sewage as an indicator of the filter activity. 



With the 1,000.000-gal. flow rate " 50 per cent of the sewage applied to the 

 4-ft. filter reaches the filter outlet mingled with 50 per cent oi the held sewage 

 12 minutes after its application, while with the 10-ft. filter 125 minures elapse 

 before 50 per cent of the applied salt sewage reached the filter outlet mingletl 

 with 50 per cent of the held sewage." With the other rates of flow " the applied 

 and held .sewage were about equally intermingled and hence were about equal 

 periods of time in passing through each filter." 



These results are taken to indicate the great economy of deep trickling filters 

 as compared with shallow trickling filters. 



The oxidation of sewage without the aid of filters, II, E. Ardebx and W. T. 

 LocKKTT {Jour. Sac. Clicm. Imluf>.. 33 {1914), ^'0. 23, pp. 1122-1124).— A con- 

 tinuation on a larger scale of the experiments previously reported (E. S. R., 

 32, p. 387), using the continuous flow and fill and draw methods, is reported. 



" The effluents obtained throughout this series of exjieriments were extremely 

 well clarified and in general were superior to those yielded by the best type of 

 bacterial filters. The outstamling feature of these results is the fact that by 

 employing diffused air the necessity for intermediate aeration and consequent 

 manipulation of sludge was entirely removed and at the same time much better 

 effluents were obtained than those yielded by plain pipe aeration when working 

 with a similar aeration period. 



The effluents obtained in the earlier laboratory experiments, when working 

 with a six hours' plain pipe aeration period, were liable to absorb an undue 

 proportion of dissolved oxygen. ... In the series of outdoor experiments 

 . . . the dissolved oxygen absorption of the effluents was remarkably low. 

 This low dissolved oxygen absorption, being coincident with a very low free 

 ammonia content, appears to support the theory previously advanced, that the 

 stage to which nitrification has proceetled is not without influence on the 

 amount of dissolved oxygen absorbed." 



The oxidation of sewage without the aid of filters, III, E, Abdern and 

 W. T. LocKETT {Jour. Soc. Chein. Itidus.. 34 {1915), No. 18, pp. 937-943, figs. 2; 

 Surveyor, 48 {1915). No. 124I, pp. 45O-454, figs. 2). — A third contribution to the 

 subject gives the results obtained to date regarding " (1) the initial produc- 

 tion of activated sludge; (2) the volume of air essential for the successful 

 working of the purification process; and (3) the most advantageous proportion 

 of activated sludge to employ; together with a description of certain exi>eri- 

 ments relating to the purification of a dilute domestic sewage." 



