WHITING FILTERS AND AERATION REMOVE OILY TASTE FROM WATER
Contact with a flocculent coagulant was found at the experimental filter plant at Whiting, Ind., to eliminate oily tastes and odors from Lake Michigan water, if followed by filtration, according to a writer in the Engineering News-Record. Aeration is desirable at times, and under certain lake conditions the aeration assists in the removal of the oil odor and permits operation with a smaller amount of chemical. At other times the air contains oil in a gaseous state, which the spray collects. These are the conclusions of Langdon Pearse and S. A. Greeley, consulting engineers for this oil refinery city of 8,200 people. In a preliminary report submitted in March aeration coagulation and filters were recommended, but to study the coagulant and aeration factors a simple testing station costing about $300 was installed. The second report has recently been made and the city has decided to go ahead with the design of a 1,500,000-gallon rapid filter plant. Whiting’s needs arise from badly polluted water and an extremely high consumption, 425 gallons per capita per day. The pollution is by sewage discharged from various municipalities and by the industrial wastes from large manufacturing establishments. The industrial sewage has an important bearing upon the treatment of water supplies from the lake. Frequently the water is decidedly turbid and occasionally is infested with substantial growths of micro-organisms which impart their characteristic tastes and odors. It was concluded, therefore, that turbidity can be removed only by filtration, and this process, coupled with proper auxiliary treatment, can also be used to remove the tastes and odors due to the industrial sewages and the microscopic organisms. The present water supply of Whiting is taken through a 66-inch brick tunnel extending approximately 2,400 feet from the pumping station to water approximately 20 feet deep. The end of the intake is approximately 1,600 feet from shore and 1,900 feet from the discharge of the main sewer of the Standard Oil plant. The intake used is of ample size to serve the needs of the city. Troubles from anchor ice are comparatively infrequent. After passing through the 66-inch brick intake the raw water enters a suction well designed to retain floating oil. This suction well comprises a circular portion 9 feet in diameter and 71 feet deep to the tunnel. A rectangular portion 6×40 feet and 26 feet deep extends to the north. Seven suction pipes lead out of this, each taking water from several feet below the surface. It is apparent, however, according to the report, that the well can have no very great effect on the removal of the oil taste from the water. Pitometer tests were made to check up the pump displacements, and from past records the average pumpage per capita for the years 1913 to 1916, inclusive, were calculated as follows: 295, 302, 304, 321 and 425 gallons. Investigations indicate that meters in Whiting wotdd probably reduce the consumption to 100 gallons per capita per day. Leaks in the distribution system probably account for the difference between Whiting and the cities of Evanston and East Chicago, where there are few meters, but the distribution systems are in comparatively good condition, it was concluded that it was desirable to make a determined effort to reduce the consumption to 200 gallons by overhauling the distribution system, thus reducing the size of filter plant required. Raw water to be tested was taken front the main factory supply line and was not treated with chlorine. It passed first to a standard aerating nozzle. The purpose of the aeration was to break the water into fine drops, thus exposing a large surface to the air and facilitating the escape of any gases or oils. A hopper-shaped galvanized-iron basin collected the aerated water, whence it flowed by gravity to a stilling box fitted with an overflow weir, the height of which regulated the amount of water flowing to the two coagulating tanks and a rapid filter. The nozzle was screwed on the top of a 1 1/4-inch pipe entering the bottom of the hopper through the center of the 6-inch collecting pipe. Comparatively minute quantities of coagulatant were required. Five-gallon bottles were inverted over ordinary pails to give a constant head. Through the bottom of the pails extended a ⅜-inch glass rod or copper pipe with a small hole in the side near the bottom of the pail. Adjustment of rate was made by moving the rod up or down through the rubber stopper in the bottom of the pail and measuring the flow. The filter was of the Harrisburg type, with a set of perforated pipe underdrains. Analyses of the composite samples of the aerated water indicated a reduction in the intensity of the oil odor due to aeration. Observations at the plant showed that at times certain oil substances were washed out of the air by the fine spray. These appeared as an oily scum on the surface of the water in the stilling box and coagulating tanks. Later on the plant was operated without aeration, and the coagulating tanks were arranged to run in series. In this way the period of contact between the alumn precipitate and the water was increased, due to the more rapid velocity. It was found that with this arrangement the oil odor was removed as well as with the aeration. Conclusions as to aeration were, therefore, that it was desirable to arrange for its use at times of favorable atmospheric conditions. At times during the investigation it was found difficult for the chemists while in Whiting to fix the intensity of oil odor in the raw water because of the odors in the air. Virtually all the tests at Whiting were positive, but in Chicago some negative results in the raw water were obtained. Tests on the filtered water, however, were virtually always negative.
New meter rates established at Batavia, Ill., are as follows. For 400 cubic feet or less per quarter, $3; for excess over 400 feet, per quarter, 12 cents per 100 cubic feet.