Aeration System

Ejector and Jet Mixers system for Aeration Process

Aeration System

The aeration tank being provided with air inlet, ejectors, liquid mixing jets, air blowers, recycle pumps, control system & interconnecting piping.

The operation of the system is controlled by pneumatic actuators connected with PLC and DO transmitter. The aeration system after stabilization is operated for nitrogen removal also. Based on the DO present in the waste water the anoxic process being operated with help of liquid mixing jet nozzles

To remove nitrogen, anoxic process is operating with liquid jet mixers. When the DO value is above the set point the air blowers are switched off & aerators stops working the pumps will supply effluent to liquid jet mixers. Respective control valves are closed as per P&I Diagram & PLC specs. When the DO value drops below the set point, once again aeration system will start & liquid jet mixers will stop working.

Pumps are operated along with air blowers to supply effluent and air to the aerators inside the tank. During aeration the liquid jet mixers are in closed position. As per reading of DO from DO sensor the aerators are operated for mixing air & water. This will reduce COD & BOD present in the effluent. After stabilization optimum DO value is maintained in tank.

Jet Ejectors

Advantages of Ejectors

  1. Maintenance-free no moving elements
  2. High oxygen efficiency - Fine bubbles create large contact surfaces between air and water and high turbulence renews these contact surfaces.
  3. No deposits - The intensive jet flow directed towards the tank floor prevents deposits of biomass.
  4. Straightforward control of oxygen supply
  5. Non-clogging construction - The nozzle diameter defines the narrowest flow cross-section.
  6. No sealing problems - When the plant is inactive, water can enter the air pipeline without negative effects and when’re-started, the ejector’s entraining effect expels any liquid in the pipe

Anoxic Process

The aeration tank is operated as anoxic system to remove nitrogen. Observe the COD, BOD & DO values regularly during commissioning & Stabilization. Analyze the outlet effluent from aeration tank for ammoniacal nitrogen.

The anoxic process operates on set values of DO & recycle ratio of effluent. When DO in effluent increases above 2.5 mg/l the aeration process is stops.

The jet mixers (18 No’s) provided at bottom of tank are operated for mixing of recycled effluent. During this period the DO starts depleting, which is consumed by the anoxic biomass for reducing ammoniacal nitrogen, when DO value in Aeration Tank drops below 0.3 mg/l, the Aeration System Starts.

Jet mixers are stopped as per the function & command received from PLC, measure nitrogen content in the outlet effluent at aeration tank during anoxic process. The process shall be optimized for maximum removal of nitrogen & range of DO values. If required during commissioning small quantity of raw effluent shall be added in the aeration tank to maintain required carbon value.