Operator tests for managing an activated sludge plant - what are the 'best' tests to run for daily operation - Part 1
Often operators perform tests and enter numbers onto a sheet or computer once a shift. In addition to the number, many of the tests have observational components that may or may not be noted. And, don't discount the power of observation in normal management of an ASU. Unlike calculated data such as F/M or MCRT, test observations and data are real time actionable items that can be used to keep the system in the ideal treatment range. Here are the field tests that I run and like to see in activated sludge systems.
Microscopic Exam - Here you want to note floc size & density, bacteria in free solution, protozoa, metazoa (rotifers), filamentous bacteria, non-filamentous bulking (India Ink test). Changes in floc and protozoa are the first indicators of changes - daily observation helps you know what is normal and spot potential problems early on.
SV30 & SVI - Settling tests give great information on floc quality entering the secondary clarifier. Look beyond just the 30 minute number - note settling rates, supernatant turbidity, let it settle for an additional time to more simulate your clarifier (2 - 4 hours), floating solids after longer settling, and a shaggy appearance caused by filamentous organisms. It is important to use the same vessel for the SV30 test each time - wall effects in cylinders and settleometers can change results.
Oxygen Uptake Rates - aerobic biological waste treatment microbes use oxygen to treat influent pollution. The OUR or DOUR test saturates a sample of MLSS with oxygen and you read oxygen consumption over a short time period. Report results in mg O2/L/hr. If you divide the OUR result by MLSS or MLVSS in grams - you have the standardized oxygen uptake rate - just make sure that you use MLSS or MLVSS as the divisor each time. As with all tests, be consistent.
Erik Rumbaugh has been involved in biological waste treatment for over 20 years. He has worked with industrial and municipal wastewater facilities to ensure optimal performance of their treatment systems. He is a founder of Aster Bio (www.asterbio.com) specializing in biological waste treatment.
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