PARTICLE COUNTER AND TURBIDITYMETER ANALYSIS OF RECLAIMED SECONDARY EFFLUENT

These are the results of a study to understand the turbidities observed in the secondary effluent supplied by Hyperion Treatment Plant (HTP) of City of Los Angeles (CLA) for reclamation. These turbidities are higher than desired, and appear to be the main reason for the frequent occasions when the reclaimed water exceeds the 2 NTU limit specified by Title 22. Simultaneous data from a Laser Particle Counter (LPC) and the turbidity meter at the HTP pumping station have been tabulated from March 11 to March 23, 1999, and subjected to several forms of analysis that show clearly that the observed turbidities are caused by a particle population covering the size range from about 7 μm to more than 15 μm. Another population was also discovered to be present, in the size range from 2 μm to around 5 μm. This population was not detected by the turbidity meter, and its concentration is often, but not always, anticorrelated with the density of the larger particles or turbidities. This study is an example of the opportunities for using particle counters to gain detailed understanding of secondary clarifier and tertiary filter behavior that would be difficult to observe in any other way. Other applications of particle will also be presented, for example, water, air and hydraulic oil.