Method for maintaining accurate and precise surface wasting flow conditions using an automated overflow weir

A method for a wasting of a mixed liquor in an activated sludge wastewater treatment system using an automated overflow weir, said method comprising the steps of:

• a) continuously measuring and recording an aeration surface elevation of an aeration basin within the activated sludge wastewater treatment system;
• b) continuously measuring and recording a crest point elevation of the automated overflow weir;
• c) telemetering the aeration surface elevation of the aeration basin as a surface process variable input into a microprocessor-based controller;
• d) telemetering a crest elevation of the automated overflow weir as a crest point process variable input into the microprocessor-based controller;
• e) computing a first derivative of the rate of change of the aeration surface elevation with the microprocessor-based controller;
• f) computing a second derivative of the rate of change of the aeration surface elevation with the microprocessor-based controller;
• g) continuously measuring and calculating an elevation differential, as the difference between the aeration surface elevation in the aeration basin and the crest elevation of the automated overflow weir;
• h) accurately and precisely maintaining the elevation differential with an actuator mechanism of the automated overflow weir, the automatic actuator mechanism as controlled by an elevation control algorithm within the microprocessor-based controller;
• and
• i) withdrawing a mixed liquor surface waste as a thin layer under a laminar flow condition, into the automated overflow weir.