UTILIZING CHIMNEY GASES FOR CARBONIZATION OF SOFTENED WATER
How Columbus, Ohio, Water Works Uses Gases from the Pumping Station Chimneys—Driven Through Scrubber and Dryer—Type of Diffuser
THE softening of hard water by the addition of lime brings about after-reactions including deposits found in the sandgrains in the filter and also in the depositions in the distribution system. The following paper suggests a method of overcoming these difficulties.
At the last meeting of the Ohio conference on water purification, which occurred in Columbus, 1922, two papers were read on carbonation, on by H. C. Campion, superintendent of water works, Defiance, Ohio, and the other by the speaker. At Defiance the carbon dioxide gas is produced by burning coke in a brick furnace, and is then introduced into the carbonation chamber under filtrose plates, or more recently, through perforated pipes submerged under twelve feet of water, and the bubbles of gas, rising through the water are absorbed.
In my paper last year a description of the experimental plant at Columbus was given. The object of these experiments, as was pointed out, was to highly carbonate a portion of the water and then feed this highly carbonated portion to the balance of the supply. On account of the large quantity of water required, however, this process was thought to be impracticable and the experiments were discontinued.
Experiments in Use of Chimney Gases
During the past year experiments have been made on the use of chimney gases from the water works pumping station as a source of carbon dioxide gas. These gases are drawn from the boiler through a scrubber and dryer by means of an air compressor and are forced into the water through diffusers located near the outlet of the settling basins.
Sulphur dioxide is about fifty times as soluble as carbon dioxide, so that it can be easily washed out of the gas. Carbon dioxide is about fifty times as soluble as carbon monoxide, and when the low partial pressure of the carbon monoxide in the chimney gases is taken into consideration, for ail practical purposes, the carbon monoxide can be considered insoluble. Therefore, in view of the ease with which the sulphur dioxide can be removed from the gases, and further in view of the non-solubility of the carbon monoxide, scrubbed chimney gases are sufficiently pure for the carbonation of softened water.
Type of Diffuser Used
The type of diffuser used is shown in the accompanying sketches. It is made by surrounding a perforated pipe with cemented sand, the cemented sand being made from twelve parts of coarse screened sand and one part of cement. The base and top are made from rich concrete in order to give strength to the leaner mixture.
The cemented sand diffuser is copied somewhat from the cemented gravel used in the Toronto filters at Toronto, Canada, where trouble was caused by too rapid back washing of the filters, resulting in the displacement of the gravel, so the gravel as ordinarily placed in a filter, was taken out and replaced with six inches of cemented gravel, using 15 parts of gravel passing a three mesh screen and retained on a five mesh screen, held together by one part of cement.
(From a paper read before the Ohio Conference on Water Purification).