IRON-REMOVAL PLANTS IN OPERATION.
Iron-removal plants are now in use at Amsterdam and The Hague in Holland, at Copenhagen in Denmark, at Kiel, Charlottenburg, Leipzig, Halle, and many other places in Germany; at Reading, Mass.; Far Rockaway, L. I.; Red Bank, Asbury Park, Atlantic Highlands, and Keyport, N. J.
Among the earliest plants for the removal of iron were the filters constructed at Amsterdam and The Hague in Holland. At Amsterdam the water is derived from open canals in the dunes draining a large area. The water has its origin in the rain-water falling upon the sand. The sand is very fine and contains organic matter in sufficient amount so that the ground-water is impregnated with iron. In flowing to a central point in the open canals the water becomes aerated and the iron oxidized. There are also algæ growths in the water which perhaps aid the process. Sand filters of ordinary construction are used, and remove both the iron and the algæ, and the rate of filtration is not higher than is usually used in the treatment of river-waters, although it could probably be largely increased without detriment to the supply.
The works at The Hague are very similar to those at Amsterdam, but covered collectors are used to supplement the open canals. Both of these plants were built before much was known about iron in ground-waters and the means for its removal, but they have performed their work with uniformly satisfactory results. In the more recent German works various aerating devices are employed, and filters similar in general construction to ordinary sand filters, but with larger connections suited to very high rates of filtration, are employed.
The plant at Asbury Park was the first of importance constructed in America. The water is raised from wells from 400 to 1100 feet deep by compressed air by a Pohle lift. It is delivered into a square masonry receiving-basin holding some hours’ supply. The aeration of the water by this means is very complete. It is afterwards pumped through Continental pressure filters direct into the service-pipes. The reservoir for the aerated water was not a part of the original plant, but was added afterwards to facilitate operation, and to give more complete aeration before filtration.
At Far Rockaway, L. I., the water is lifted from wells by a Worthington Pump, and is discharged over the bell of a vertical 16-inch pipe, from which it falls through the air to the water in a receiving chamber around it. The simple fall through the air aerates the water sufficiently. From the receiving-chamber the water is taken to either or both of two filters, each with an area of 20,000 square feet. These filters are open, with brick walls and concrete bottoms, three feet of sand and one foot of gravel, and the underdrains are of the usual type. The water flows through regulator-chambers to a well 25 feet in diameter and 12 feet deep, from which it is pumped to a stand-pipe in the town. The plant was built to treat easily three million gallons per day, and has occasionally treated a larger quantity. Either filter yields the whole supply while the other is being cleaned. The rate of filtration in this case was made lower than would have otherwise been necessary, as there was an alternate supply, namely, the water from two brooks, which could be used on occasions, and to purify which a lower rate of filtration was regarded necessary, than would have been required for the well-water. The removal of iron is complete.
Fig. 25.
The plant of the Rumson Improvement Company at Red Bank, N. J., is quite similar to that at Far Rockaway, but is much smaller. The outlet is a 6-inch pipe perforated with 1⁄4-inch holes which throws the water out in a pine-tree shape to the receiving-tank, thoroughly aerating it. Each of the two filters has 770 square feet of area. The filtering material is three feet of beach sand. From the regulator-chamber the water flows to a circular well 18 feet in diameter, covered by a brick dome and holding 17,000 gallons, from which it is pumped to the stand-pipe. Either of the filters will treat ten thousand gallons of water per hour, which is equal to the capacity of the pumps; and as the consumption is considerably less than this figure, they are only in use for a part of each day, the number of hours depending upon the consumption. These filters are shown by the accompanying plan. The cost of the work was as follows:
| Filters and pure-water reservoir, with piping and drains complete | $3,799.47 |
| New pump and connections | 492.68 |
| Engineering and superintendence | 992.91 |
| Total cost of plant | $5,285.06 |