Turbidimetric Control of Filter Effluent Quality

THE use of high filtration rates increases the need for an accurate, sensitive device to monitor the quality of filter effluent continuously and instantaneously. The filter influent of surface water treatment plants that practice prechlorination and the filter influent of ground water treatment plants are relatively free of bacteria. In these treatment plants, the effluent turbidity is frequently the best index of filter performance; bacterial evaluation is a secondary index. Degradation of effluent turbidity results in a corresponding degradation in bacterial quality in those waters containing a significant bacterial population. An accurate, sensitive turbidimeter that continuously reads and records data should be of great value to the water supply industry. Such an instrument * has been recently developed. The low-range turbidimeter has been used extensively in plant scale and pilot plant research on high-rate filtration at Iowa State University, Ames, Iowa, and at the Ames treatment plant. It has great potential value in filter control.