FILTRATION FOR CROTON WATER.
Nelson P. Lewis, chief engineer of the board of estimate and apportionment of New York and Coniptroler Metz have before them for approval the plans of the city’s water department for the construction of filterbeds to cost from $8,000,000 to $11,000,000. If the plans are approved, these will be built in the unfinished part of Jerome Park reservoir, and, on their completion, within two years, every drop of Croton water opening into the city will be filtered before it is delivered through the mains for domestic use. The two officials above mentioned are said to favor the project, and there seems to be a well-founded expectation that in a few weeks Commissioner John F. O’Brien, of the water department, will be given authority to proceed with the work. The department is now making experiments with a small filtration plant at the Jerome Park reservoir, under an appropriation of $25,000 set apart for the purpose, and it is said that the results so far tend to bear out the calculations of the engineers that an acre of sand will filter 10,000,000 gals, of Croton water a day. As soon as the speed of filtration is determined, an appropriation of $8,000,000 will be asked for to build the filterbeds, which will cover forty-five acres in the die of the 135-acre tract composing that ern halt, or unfinished portion of the reservoir. As the Croton supply is about 400,000,000 gals a day, it is calculated that this plant will he adequate to filter the whole inflow. A11 additional expense will be incurred in covering the storage reservoir. This will be a costly work, as the excavations at Jerome Park were made in the solid rock. It may, therefore, be that the reservoir, with the filterbeds, will cost $20,000,000. One question arises as to building the filterbeds, and that is, Does the Croton water need to be lit tered? Up to the present, i( is insisted that at present such a necessity does not exist; but there is always a possibility that it will turn up to be so because by reason of the state of the water shed or the seepage of impure water into the aqueduct. Sometimes, also, the Croton water is dirty and .yellow, and has a peculiar taste, and although, it is claimed that there is nothing unwholesome about these features; yet, as people prefer clear, pure water, and (especially by the hotels) considerable expense is incurred in the purchase of spring, filtered or distilled water— now a general practice—it is insisted that filtration isa necessity, unless the city owns the entire watershed and protects it properly from end to end. As to the speed of the filtration plant, Chief Fngineer Lewis says that, after consultation with the “foremost experts of the country,” their verdict, one apparently borne out by the experiments so far made, is that beds covering forty-five acres at the Jerome Park reservoir will filter the whole Croton supply—or 400,000,000 gals, a day. For the filterbeds can be utilised the unfinished part of Jerome Park reservoir. I he beds can be laid over a basin, which can be used to store the filtered water, and that part of the reservoir now used for storage can be roofed over for similar use, if necessary. The aqueduct runs between the two parts, and the turning of the water into the filterbeds and drawing it off into the mains will be possible with the minimum of difficulty and expense.