Ontario Provincial Board of Health Annual Report, 1909
By M. Ferguson, B. Sc., C.E. pg. 95
Report on Proposed Improvement of the Sewage Disposal Plant of the City of Stratford
I beg to submit plans for the improvements to the sewage disposal plant and an estimate of the cost of same.
The first question which had to be considered was which method of purification should be adopted.
Sand filtration and chemical precipitation are both impracticable, the first as there is no sand in the neighbourhood and we have not sufficient land at our disposal, the second on account of the cost.
This narrows the question down to contact beds and percolating filters. Contact beds have been in operation here for some time and have not been a success; to continue with this system we would require to increase the area of the present contact beds nearly three times. In recommending the sprinkling system I am not recommending an experiment, but one that has been thoroughly tested and has been found to give the necessary purification.
The present tanks have the necessary capacity, but need to be repaired. The smaller tank No. 1 at the south end will be used as a pump well. This will necessitate the inlet being closed and a syphon put in from No. 2 tank. The object is to keep the sludge at the bottom from being stirred up and entering the pump. From this pump well the liquid will be pumped through an I8-inch pipe to a storage tank shown on the plan from which it will be distributed by gravity to the different beds. The capacity of storage tank will be 104,707 gallons, or 2 1/2 hours’ flow. The bottom of the storage tank will be at an elevation of 61, the tank is ten feet high, the sewage will be delivered to the distributors in the filter at an elevation of 61, with a 4 1/2-foot rise, thus giving 11 foot of head. At the tank there are three gates, one to each of the pipes leading to the beds, so that any of the beds can be shut off and given the necessary rest.
There are three main distributors from the storage tank to the beds. Each of these main distributors has five laterals on each side, ten in all per bed, each of which is controlled by a valve, so that the head to the sprinklers can be increased or decreased, and thus giving more equal distribution over the filtering material. The sprinklers have a 4 1/2 foot rise with a nozzle; they are placed 1.5 feet apart. The filters will be working at the rate of 140.6 gallons of sewage per 24 hours per cubic yard of filtering material. The beds all have a slight fall towards the centre, to allow of the effluent being carried off readily. The lateral collector is underneath the distributor, and they will both be built in concrete.
To prevent clogging the lateral distributors are carried to the surface, so they can be flushed out. A pipe line from the river is laid as shown, and to the hydrant a hose can be attached for flushing purposes.
In regard to tertiary treatment I have made allowance in the estimate for a settling basin or tank for chlorine, which can be put in later should we not get the necessary purification.
The system as proposed will treat one and a half million gallons. The present flow is about 950.000 gallons, and in our plans we have figured 25% more than is necessary at present; this will allow for increased population up to 20,000.
To overcome the effects of severe winter weather on the sprinklers I propose to carry pipes from the boiler to the storage tank and allow the exhaust steam to be carried around the tank; in this way the liquid can be heated 10° to 15°, so that it will go through the sprinklers warm and prevent any freezing around the nozzle.
Estimate of Cost
| Concrete Floors and Walls in Filter Beds | $4,083.20 |
| Tank | 1,414.00 |
| Walks | 469.00 |
| Excavation | 1,009.40 |
| Broken Stone | 12,444.25 |
| Piping, Sprinklers and Drainage | 2,095.95 |
| Boiler | 600.00 |
| Pump | 500.00 |
| Pump House | 800.00 |
| Excavation and Extras | 500.00 |
| $23,915.80 |
Ontario Provincial Board of Health Annual Report, 1913
Reports of the Provincial Sanitary Engineer, pg. 51
Stratford, August 13th.
In company with Dr. McNally, and upon instructions from Dr. McClullough, arising out of the threatened litigation against the City of Stratford re the pollution of the River Avon, a visit was made to that place. The findings in connection with this investigation were as follows:
- Indifferent management of the sewage disposal works has existed, and, when convenient, raw sewage is bye-passed directly into the river.
- The present pumping equipment is inadequate, both as to size and equipment.
- The sedimentation tanks are in a bad state of repair and will need replacement in four or five years. The design of the tanks is bad and the sludge is being constantly thrown into suspension by gas from the bottom.
- Under the existing arrangement, the sedimentation tanks cannot be cleaned without sending the sewage into the river; this operation takes from five days to two weeks.
- The humus from the sprinkler beds is not intercepted in any way and is carried to the creek with the effluent, creating a black sludge therein; this sludge destroys vegetation on account of producing anaerobic conditions in its vicinity and creates a nuisance in shallow parts of the stream.
The following modifications were suggested as being necessary to fulfil the requirements of the Public Health Act and to prevent successful litigation:
- Improved pumping equipment, making the pumps more nearly automatic, with the addition of an auxiliary which would provide power in the event of the electric pumps failing and which would also be available during storms to assist the electric pumps during maximum storm water flow, the pumping equipment to be of a capacity adequate to handle the maximum flow of sewage.
- The construction of a humus tank of the double chamber type with a capacity for at least 20 minutes storage at maximum hourly flow from the sprinkler beds.
- Replacement of a portion of the present sedimentation tanks by a modern double chamber type, of capacity for 30 minutes at maximum flow, the sludge chamber arrangement to be such that sludge could be removed without interfering with the operation of the tanks; the tanks to be provided with grit chambers and a screen.
- A chlorination plant suitably heated to be provided for the treatment of the sprinkler effluent in order to protect the cattle using the stream lower down from undue presence of pathogenic organisms. This latter modification would assist very materially, in the event of a storm or other untoward circumstance, in the handling of raw sewage and would permit of its being byepassed for short intervals subject to heavy’ chlorination from the settling tank into the stream.
I am pleased to further report in this connection that the City of Stratford has submitted plans for the suggested modifications and anticipate the construction of a portion of these works in 1914.