COMBINED CONTROL OF SEWER AND TREATMENT-PLANT DURING RAINSTORM

The use of flow predictions and on-line nutrient sensors in BNR plants has given the basis for introduction of radical operational changes. Because of the detailed monitoring, the control actions are allowed to go closer to critical process limits while balancing between hydrauli c and biological capacities. One of the new modes of operation, settli ng in the aeration tanks as an active control, is documented below. Th is new operation, Aeration Tank Settling (ATS) has been tested at full scale and shows a great potential for storm water control. With ATS c ontrol the hydraulic capacity is increased 25-75% on existing plants w ithout reducing the organic capacity in periods ranging from 2 hours t o 2 weeks. ATS control can be initiated directly by raising the inlet flow to the treatment plant, but even better by 1/2 - 1 hour predictio n of the inlet flow. These predictions of flow are achieved from stati stical grey-box handling of data from on-line rain gauges and measured inlet flow pattern during normal and stormwater conditions. Hourly pr edictions of concentrations in the inlet to the plant and selected poi nts in the sewer system during dry weather and storm situations will i mprove the combined system control efficiency radically. Copyright (C) 1996 IAWQ. Published by Elsevier Science Ltd.