Pollution Prevention in Distribution Systems in Britain

Abstract

question of the precautions to be taken to prevent pollution of potable water supplies has received very close attention in Britain during recent years. It is fully appreciated that every undertaking has its own particular problems based on local conditions and that these naturally vary, but it is hoped that some of the points enumerated in this article will prove of general interest. The Sutton District Water Co. supplies a population of approximately 325,000 in a compact area of 40 sq.mi., the greater part of which lies within the London Metropolitan Police Area. The water is pumped from deep wells in chalk and softened below 9.0 g.p.g.* by the lime process. It is believed that the Sutton District Water Co. was one of the early water suppliers to institute the practice of sterilization of new mains in Britain, the system being started in 1932. At first, the sterilization was carried out by use of a chlorinated soda solution which was introduced into the main through a hydrant or ferrule connection by pouring it down a 'or f-inch standpipe provided with a funnel. The amount of soda solution used was calculated to give a concentration of about 10 p. p.m. chlorine in the section of main to be sterilized, but this strength was later increased. Experience has shown that this method did not permit an even distribution of the sterilizing liquid in the section of the main to be treated, particularly when the main had been laid on undulating ground. The method was therefore discontinued. Portable chlorinators using liquid chlorine from cylinders are now used to sterilize all new mains. Heavily chlorinated water is in-