United States of America
I. Kruger Inc.

4001 Weston Pkwy
Cary, NC 27513

Phone: (919) 677-8310
Fax: (919) 677-0082

Activated Sludge Technologies

With over 80 installations in the United States, wastewater treatment facilities can rely on Veolia's extensive biological experience and proven oxidation ditch technologies. Veolia offers a multitude of processes, including our signature Phased Isolation Ditch (PID) and A/O®, A2/O, and An/O systems, providing flexibility in meeting the diverse requirements of plants. Veolia's biological treatment technologies efficiently achieve today's stringent effluent requirements.

Veolia's biological processes can be adapted to a wide range of treatment requirements from basic secondary treatment to advanced nutrient removal.In addition, Veolia has the capability to upgrade or retrofit existing systems.

Phased Isolation Ditch (PID) Technologies

A Phased Isolation Ditch system is a continuous flow activated sludge process in which the main treatment phases of the process are isolated into separate oxidation ditches. The process conditions within the oxidation ditches will alternate or phase between oxic, anoxic and/or settling. Phased Isolation Ditch can be designed to operate with or without external clarifiers. These processes include the Double Ditch (D-Ditch), BIO-DENITRO and BIO-DENIPHO.


Double Ditch (D-Ditch)

  • Ideal solution for plants with future growth plans or stricter nutrient limits
  • Ease of future expansion and upgrade for increased nitrogen removal or flow by adding secondary clarifiers and another ditch
  • Reduced plant maintenance, secondary settling tanks are not required
  • Achieves exceptional effluent quality of BOD and TSS <10 mg/L by alternating between aerobic (nitrification) and settling phases

3.0 MGD


  • Separation of mixing and aeration combined with automatic dissolved oxygen control, ensuring energy efficiency and stable operation
  • Simple process configuration; no internal recycle pumping or separate anoxic reactors
  • Automated control system with preprogrammed operational modes, easing operation
  • Easily adaptable to load and seasonal variations; process flexibility afforded by the capability to vary the effective process volumes allocated for aerobic and anoxic treatment

12.0 MGD with Secondary Anoxic Zones


  • Expansion of the BIO-DENITRO, utilizing a similar configuration and mode of operation with the addition of a Block and Hong Anaerobic Selector
  • Biological phosphorus removal achieving TP <1 mg/L, resulting in highly efficient BNR system

Additional Biological Treatment Solutions

6.3 MGD An/O

Veolia's additional biological treatment solutions are superior alternatives to other multi-stage BNR systems. Veolia has adapted the A/O® and A2/O processes for oxidation ditch layouts.With minor modifications, these processes can be applied to existing oxidation ditch plants resulting in significantly improved performance.

A/O® (Anaerobic/Oxic)

Veolia's A/O Ditch process utilizes the Block and Hong Anaerobic Selector for biological phosphorus removal followed by a single or multiple oxidation ditches.

A2/O (Anaerobic/Anoxic/Oxic)

Veolia's A2/O process incorporates an anoxic zone between the anaerobic selector and oxic zones for nitrate reduction.For more stringent TN limits, a secondary anoxic zone can be added for additional denitrification.

Process Control Features

Veolia's biological treatment systems are equipped with a PLC based control panel for enhancing the plant's daily operation.The PLC based control panel is provided of preprogrammed operational modes for ease of operation. Veolia also offers customized plant-wide SCADA systems.The SCADA system monitors and controls the process while storing relevant data that can be used to compute and report plant performance, allowing the operators to gain valuable insight into the operation of the plant. As a result, operators become more confident in the plant's capabilities and are able to optimize the plant's performance.

Veolia's Biological Process Engineers work side by side with our Instrument and Controls Engineers on each project. Therefore, expert process knowledge goes into every Veolia integrated process control system provided.

  • Customizable PLC based control
  • SCADA system including 2-D and 3-D rendered graphics
  • Use of open architecture software
  • Point-and-click navigation and control
  • 24-hour alarm monitoring and notification
  • Systems certified integrators

STAC (Superior Tuning and Control)

Veolia's Phased Isolation Ditch technologies can be design or upgraded with dynamic phase control, optimizing energy usage and TN removal.

  • Dynamically control ditch phase lengths in response to incoming loading, providing real time operation
  • Improving total nitrogen (TN) removal by 2-4 mg/L than with a fixed phase length system
  • Resulting in energy savings from optimization of operation of ditch aeration equipment