XX. J. M. SMAIL. 



3. Filters must be so constructed that samples of the effluent 

 of any one of them can be taken at any desired time for 

 bacteriological examination. 



5. The person entrusted with the carrying out of the bacterial 

 examinations, must present a certificate that he possesses the 

 necessary qualifications, and wherever possible he shall be a 

 regular employee of the waterworks 



7. Every single filter must be so built that when an inferior 

 effluent results which does not conform to the standard, it 

 can be disconnected from the pure water pipes and the filtrate 

 allowed bo run to waste ; this wasting should take place, so 

 far as the arrangement of the works will permit ( I ) imme- 

 diately after scraping a filter, and (2) after replacing the sand 

 to its original depth. 



8. The best sand filtration requires a liberal area of filter surface, 

 allowing pi* nty of reserve, to secure under all local conditions 

 a moderate rate of filtration adapted to the character of the 

 raw water 



15. The thickness of the sand layer shall be so great that under 

 no circumstances shall it be reduced by scraping to less than 

 30 centimetres (12 inches), and it is desirable so far as local 

 conditions allow to increase this minimum limit Special 

 attention must be given to the upper layer of sand, which 

 must be arranged and continually kept in the condition most 

 favourable for filtration. For this reason it is desirable that, 

 after a filter has been reduced in thickness by scraping and 

 is about to be re-filled, the sand below the surface as far as 

 it is discoloured should be removed before bringing in new 

 sand. 



16. Every city in the German Empire, using sand-filtered water, 

 is required to make a quarterly report of its working results, 

 especially of the bacterial character of the water before and 

 after filtration to the Imperial Board of Health. 



