feet, it would require 32 of these applied to softening water to effectually deal with 2,000,000 gallons per 24 hours; this, at the lowest estimate for filters alone, would be L8,000, and, using the same figures, L5,000 for lime mixing tanks, etc., as referred to in the “Slack and Brownlow” purifier, would bring the total cost up to L13,000, and the working expense would not be less than that required to work the Porter-Clark process, and would probably be very much greater.  This filter press is not in use anywhere for dealing with large quantities of water in connection with a town water supply.

A process which has been working for a long time at Southampton is the Atkins system, which also includes the use of filter presses.  The pumping station and softening works are situated at Otterbourne, eight miles from Southampton, and were built together as one scheme.  The mixing room has two slaking lime tanks, with agitators driven by steam power.  The mixture is then run as cream of lime into a tank 20 ft. square and is then pumped into the lower ends of two lime water producing cylinders.  The agitation is here obtained by pressure from a small cistern placed above them with a 12 ft. head, the pipe from which is attached to the lower ends of the cylinders.  This has been found by experiment to be the most satisfactory means of obtaining the proper degree of agitation necessary; the clear lime water is then drawn off at the top of the cylinders, and flows by gravity into a mixer, where it comes in contact with the hard water.  Both flow together into a distributing trough, from which it overflows into a small softening reservoir, having a capacity of one hour’s supply, a weir being placed along the lower end, over which the water flows to 13 filter presses.  The clear water from the filters is then conveyed to a small well, from which the permanent engines raise it to the first of a series of high level covered service reservoirs.

In the filter press there are 20 hollow disks representing a filtering area of 250 square feet, or a total of 3,250 square feet.  The water to be filtered passes into the body of the filter and then through a filtering medium of cloth laid on a thin perforated zinc plate, into the inner side of the disks, from whence it is conveyed through the hollow shaft, to which the disks are attached, to the high level pumps.

The filter cloths are cleaned three times every 24 hours, without removal, by jets of softened water from the main, having a pressure of 60 pounds to the square inch.  During cleaning operations the disks are made to revolve slowly; this only occupies a space of five minutes for each cleaning.  The cloths last from six to eight months without being renewed.  They also occasionally use for further cleaning the cloths a jet of steam injected upon the center of the disks in order to remove by partial boiling the insoluble particles engrained in the cloths.  This has been found to make the cloths last longer.  This cloth is obtained from Porritt Bros. and Austen, Stubbing Vale, Ramsbottom, and costs 131/2d. per lineal yard of a width to suit the disks.