Ontario Provincial Board of Health Annual Report, 1913
Reports of the the work done in the Laboratory of the Provincial Board of Health, pg. 85
Report Re: Septic Tank Capacity at Berlin, Ontario
Toronto, March 10th 1913
During the summer months of 1912, a series of experiments were carried on with reference to the various methods of sewage treatment at Berlin, Ontario. At this time the daily flow approximated 375,000 gallons. The Berlin sewage on account of the large amount of a special kind of tannery waste in it has a character quite different from most other municipal sewages. Eighteen hour treatment gave a reduction of 45 per cent, in the organic matter. Twenty-four hours gave 55 per cent, and this over a period of five months. This 10 per cent, on the top end was considered such an advantage that when the present plant was decided on a twenty-four hour treatment was installed, with the full knowledge that eight hours had been shown to be quite as good as sixteen and twenty four hours in some other places. This Berlin sewage is a special one. and has probably not materially changed in composition.
The Imhoff method now so generally coming into use is on a different principle. The sludge only is septicized in the trapped under chamber. The upper chamber is simply a sedimentation one and should not be of greater capacity than one hour.
The Berlin tank was designed for a twenty-four hour holding of 150,000 gallons. The second chamber was simply intended as a reservoir to hold the effluent from the septic tank for such time as it would be convenient to put the pumps into commission. (When the city power consumption was below peak.) Another reason for the second tank was that as the quantity of the sewage in the future would increase and the capacity of the first be overtaken, half of the second could then be used as a septic tank, the rest still as a receiving reservoir, and as the quantity grew that the third portion could be used as a septic tank, thus making both original septic tank and reservoir a septic tank system for 900,000 gallons. It is quite probable that that time has now been reached. It was also intended when this full capacity was reached that a small receiving reservoir be constructed
to take up the work of the one constructed into a septic tank. Of course, pumping will now have to be done over a longer period of time than formerly.
Also it was intended that the filter beds should never be called on to do more than 75,000 gallons per acre on an average per day throughout the year. I am afraid they are being already worked much beyond this capacity. If so and this is continued, there will soon he trouble with them of a serious nature.
So unless some other system of preliminary treatment is to be adopted twenty-four hour treatment should be continued and the number of beds increased so that not more than 75,000 gallons be forced through them.