The reasons for poor operation are various. One is a shortage of qualified operators, based on a need for better salaries, more training programs, and rigid mandatory State certification of operators' abilities. Another reason can be a pinchpenny attitude on the part of municipal authorities toward sewage treatment. It is one sizable expenditure whose results cannot easily be pointed out with pride to local taxpayers at election time, for its main effect is usually downstream from the municipality itself. Thus the big encompassing reason for bad plant operation--cutting corners, refusing to spend what needs to be spent, failing to supervise--has to be called philosophical. It comes from a failure on the part of local operators and authorities and much of the public to comprehend the immorality of deliberate avoidable pollution, and it may mean that municipal operation of treatment plants is itself often a major source of trouble. A clear example of this philosophical deficiency is one large Basin treatment plant that was reported to have "handled"--i.e., properly disposed of--a third less sewage sludge in 1965 than it had in 1960, despite a large increase in the population it serves. The unhandled sludge, of course, went straight into the local river for reasons of convenience, economy, and callous indifference. For the most part, large private industry demonstrates more responsibility in this respect than the Basin's municipalities or Federal installations. There are some miserable exceptions where individual industries dominate a locality's economy and take casual advantage of that fact. But responsible industry is concerned with public relations, and knows that a fish kill or a gray-blue stretch of blighted water downstream from its outfalls is the poorest kind of public relations to be had. To be able to say precisely how much bad plant operation is adding to pollution in the Potomac will require exhaustive and continuous sampling and analysis of a kind that may be expected now that the Water Quality Act of 1965 is about to make itself felt through application of new State water quality standards. But experienced observers in INCOPOT and elsewhere feel strongly that bad operation does much more damage than do over-aged or outgrown facilities, though these play a big part too. Bacterial pollution--the category of most interest from a public health standpoint--fluctuates a great deal in the Basin's flowing streams, but is heavy in most of them by current standards during times of normal flow. It may come from raw waste discharges, from treatment plants that skimp on chlorination of their effluent, or from storm runoff and natural drainage off the land and urban pavements. But before anyone can confidently say how dangerous it is to swimmers and others who make intimate use of rivers and creeks, water scientists are going to have to learn more about its measurement and classification than they presently know. [Illustration]