Entech Design, Inc. manufactures interface level analyzers for a variety of municipal and industrial process applications. Systems in the wastewater treatment industry provide measurement of sludge blanket levels in primary and secondary clarifiers and gravity thickeners.
The West Point Wastewater Treatment Plant (WWTP) in King County, Wash., recently used an Entech BinMinder 9300 ultrasonic sludge level analyzer to investigate improvements to sludge wasting in primary clarifiers. After confirming accurate and reliable measurements, West Point WWTP used the instrument to determine whether its existing sludge-wasting scheme was achieving stated goals. According to Hien Nguyen, process analyst for West Point, “The plant was looking for a reliable blanket-level measurement to help control sludge-wasting from their PLC [programmable logic controller] system.”
Out with the old
West Point currently measures sludge level over the sludge sump area in its rectangular clarifiers to maximize wasting. The blanket level is measured manually twice each day. From this information, plant personnel adjust pumping operation. The strategy is to maintain 2-ft sludge levels in primary clarifiers by increasing or decreasing the pump operation according to the infrequent manual measurements.
According to Nguyen, “If the blanket level is above 2 ft, pump operation is increased by 5%.
If the blanket level is below 2 ft, pump operation is decreased by 5%. No adjustments are made if the blanket level is 2 ft.”
In with the new
Five weeks of data from the new analyzer illustrated an obvious diurnal pattern, with the blanket level varying from a low of 2 ft to a high of 8 ft. It is fair to conclude that the current pump control routine does not effectively maintain the blanket level near the desired target level, presumably as a result of the infrequency of manual measurements and corresponding infrequency in adjusting pump operation.
By using BinMinder 9300, the plant found a cost-effective and reliable solution to problems associated with infrequent and otherwise unreliable manual sludge level measurements at West Point WWTP. The plant continues to explore more effective ways to waste sludge in conjunction with the sludge level analyzer.