NEW STERILIZATION PLANT AT MILWAUKEE
The new sterilization plant installed in Milwaukee, Wis., during the past year, is described and illustrated in the annual report of the city’s water works for the year ending December 31, 1913, prepared by Superintendent H. P. Bohmann. The report recites that up to a few years ago the purity of the city’s water, which is supplied from Lake Michigan, was never questioned. However, in time the ever increasing volume of sewage discharged into the lake began to contaminate the watet supply at times when the direction of the wind carried the contaminated water in the bay towards the intake. In 1910 a continued high death rate from typhoid cast suspicion on the water supply and, at the recommendation of the health commissioner, the water department took immediate steps toward sterilizing the water supply with hypochloride of lime. No time was lost, for the first outfit, consisting of an iron tank in which the solution was mixed, was placed in service and the treatment began within 48 hours from the time the decision to treat the water was made. This was on June 21, 1910, and eight days later three cypress tanks, which had been built for the purpose, were placed in service. These tanks were located in the open immediatly over the shore shaft of the intake tunnel and the outfit had to be abandoned as soon as cold weather set in. The result was that a more permanent plant was built in a room adjacent to the north boiler house of the pumping station. This plant consisted of two concrete dilution tanks, each having a capacity of 2,310 gallons, and a concrete mixing tank of 200 gallons capacity. The stirring device in the tank was operated by hand and a float gauge regulated the flow. It being decided to make the treatment a permanent feature, contracts were entered into on January 18, 1913, for the construction of a separate building and the installing of apparatus that the sterilization might be done in a more satisfactory and scientific manner. This building, measuring 30×60 feet, is situated about 200 feet east of the North Point pumping station. it was completed and the new plant was placed in operation on September 29 last. The building is a twostory brick structure, and the total cost of the building, together with the apparatus was $8,-091.95. Since this up-to-date plant was placed in service far greater efficiency of this method of treating water has been achieved; the mechanical operation of all stirring devices and the absolute regulation of flow by means of orifice boxes with calibrated gauges, giving results which could not be obtained with the old hand-operated plant. On the first floor all three reinforced concrete dilution tanks, having an average capacity of 2,638 gallons each. Connected to these tanks are three orifice boxes, used to maintain the solution at a constant head. A large room for storing the bleaching powder is on this floor. Two mixing tanks, each having a capacity of 328 gallons, and constructed of reinforced concrete, are located on this floor and elevated so that the tops are flush with the second story floor. The motor and machinery necessary to operate the stirring and mixing devices are all located on the second floor. Separate laboratories, one for water analyzes and the other for testing coal and other analytical work are also located on the second floor. A chemist, who has charge of the plant, supervises the water treatment and daily makes chemical and bacteriological examinations of the city’s water supply. The cost of the treatment, including depreciation and interest, based on a daily pumpage of 50,000.000 gallons and 6 pounds of bleaching powder per million gallons, is 25 cents pet million gallons. The amount of chemical applied has varied from 3 to 8 1/2 pounds per million gallons. The report recites that Milwaukee’s typhoid death rate in 1913 was 11 per 100,000 of population, the lowest in 39 years.
The report gives the total pumpage for the year as 17,493,257,940 gallons. The cost ot operation was $288,138.20 and the revenue for water only was $871,878.71. Based on the calculation that the department received revenue on 80.57 per cent, of the total pumpage, the revenue per thousand gallons was .06185, or .04984 per 1,000 gallons of the total pumpage.
The operating expenditures for 1913, excluding depreciation, were $288,138.20 and are $10,721.09 in excess of the expenditures of 1912. This was due to the salary raises which went into effect January 1st, 1913, and to additional positions created in order to grant all department employes 15 days’ vacation in place of 10 days as heretofore as ordered by the Common Council. Leaving out the increase due to salary raises and additional help on account of vacations, the operating expenses are about $3,000.00-less than those of 1912, notwithstanding the enlargement of the plant, which gives us more mains, hydrants, valves, etc., to maintain, all of which adds to the cost of operation. Furthermore the cost of repairing leaks is becoming more expensive each year on account of the putting down of permanent pavements making the cost of opening a street very expensive. For these reasons it must be expected that with the growth of the department there will also be a corresponding increase in the cost of operation. The Milwaukee water works are owned by the city and were originally constructed in 1872-1874. The present population is estimated at 410,000 and the mode of supply is pumping. It is estimated that 430,000 people, including those in the suburbs, are supplied with water. The mains extend 51,233 lineal feet and 523 lineal feet by annexation. Two thousand one hundred and eighty-one taps were added during the year.