New Britain herald., 1914-07-09

in which this humus' matter is de- posted and removed from time to time. I advise the use of coarse ma- terial for the sprinkling filters at New Britain with final settling tanks.
 Imhoff Tanks.
 Regardless of the type of filter to be adopted it will be important to subject the sewer to sedimentation so as to remove, prior to the application of the sewage to the filters. as much of the coarse suspended matter as practicable. This is best done in sedimentation tanks of the two-story type, familiarly called 'Imhoff' tanks. In tanks of this type the upper com partment with its sloping bottom baf- fles is of size to allow the sewage on an average to remain for about two hours during its course through this settling compartment. At the bottom of the sloping baffles is a slot through which solid matters deposited from the flowing sewage pass to a digestion chamber below. In the latter the sludge or solid matter is allowed to accumulate for six months or so, dur ing which time it is bacterially de- composed to a point where it no longer has any odor. Furthermore, the decomposed sludge can be applied readily to thin beds of coarse sand or gravel and have its water removed by this draining operation. After 1t has been drained this sludge can be readily spaded and removed to any convenient place of deposit or used for fertilizing purposes if so desired. The material closely resembles garden soil in appearance and texture.
 Odor Question.
 "Imhoff tanks and sprinkling filters are perfectly capable of treating a sewage as fresh as Is the sewage re- ceived at the New Britain works, and giving an effluent which will not pu- trefy. Immediately at the nozzles 1t is probably that odors will be notice- able, but they will rarely, if ever, be noticeable beyond the limits of the plant. This is the experience of more than six years at Reading, Pa., where a fresh sewage has been treat ed and the same experience has ob- tained at two plants at Atlanta. Ga., to say nothing of small plants at numerous places elsewhere.
 1T want to emphasize here the nec- essity of keeping the sewage in a fresh condition as it is thrown as T spray from the sprinkler nozzles. as this is vitally' important to guard against the odors which have been noted at some places where the sew age has reached .putrefying condi- tion before it has arrived at the sew age treatment works.
 Flies.
 "Sprinkling filters depend for their efficiency not only upon the oxida- tion which the spray receives as it comes in contact with the air at the top of the filter, and the bacterial agencies acting within it. but they also depend upon the removal of or ganic matter by various forms of life larger than bacteria. Frequently flies and worms abound in the pores of the broken stone. I mention the fly question in particular because they frequently are driven by the wind for 100 or 200 yards from the beds. It is perfectly feasible to control this feature by the use of suitable ger micide. @
 Location.
 "Tn my opinion the best location for sprinkling filters and Imhoff tanks would be on the north side of the westerly section of the existing plant.
 Estimates of Cost.
 'In carrying out the above recom- mendations for a disposal plant to treat six million gallons of sewage substantially as analysed on June 30, and July 1, 1914, or to take care of the strictly domestic wastes of city of S0,000 people, construction works would be required as follows: Imhoff tanks ..............$ 91, 900 Siudge beds ............,.. 11,000 Sprinkling filters .......... 77,000 Final settling tanks ........ 30,000 Pumping station ........... 18,000 Miscellaneous ............ 10000
 $337,0 900 Engineering and contingent cies, IS per cent. ........ 51,000