_In a paper read before the Engineering Society of China, on Tuesday, Mr. C. D. Pearson described the methods adopted and the problems encountered in the purification of water for public supplies, more especially where, as in Shanghai, a turbid and highly polluted river water has to be dealt with. The Huangpu, be said, differs from almost all otherwise similar sources of supply in being tidal, the tides causing a considerable hourly variation in the amount and nature of the sediment in suspension in the water. In addition, the river is subjected to considerable pollution and to large temperature variations, Mr. Pearson pointed out that, although a less polluted water is obtainable from lakes situated within 50 miles of Shanghai, the cost of conveying the water and possible political difficulties would render such a sour'ee unsuitable. With modern purification methods efficiently controlled, the water engineer is able to render hygienically safe a water of very poor quality. Huangpu water is fortunately free from abnormal quantities of dissolved, impurities, the hardness is low—a satisfactory feature from the domestic and industrial standpoint—and, although the river is tidal, the salt content has not, in the last 20 years, been sufficiently high to cause anxiety.
The water purification works in Shanghai are consequently emploved in removing suspended. impurities, consisting of sediment, colloidal matter, microscopic plant life and bacteria. The paper described the methods adopted to carry out the removal of suspended impurities, viz., storage, settlement, filtration and sterilization.
Text read from the printed page and cleaned; old type leaves the occasional error.