Ovivo® Digestivore™ Sidestream Treatment System

The Ovivo® Digestivore™ sidestream treatment system is a physical and biological process that allows wastewater treatment plants to thicken the waste activated sludge (WAS) generated by their activated sludge system, while simultaneously removing ammonia present in the sidestream, generated by their dewatering equipment.

The Ovivo® Digestivore sidestream treatment system addresses four key issues of the wastewater treatment process.

  1. Our technology virtually eliminates ammonia present in the dewatering sidestream, thus improving NPDES permit compliance.
  2. Operating and maintenance costs are lower due to lower energy and chemical consumption at the facility.
  3. The permeate that is returned to the head of the plant can be high in nitrates, which helps prevent H2S formation at the primary clarifiers.
  4. BOD treatment capacity is increased in the aeration basins due to the reduction in oxygen demand for nitrification of sidestream ammonia.
  • Eliminates polymer for thickening
  • Retrofits into existing tanks
  • Robust process requiring little operator attention
  • Flexible design criteria based on owners needs
  • Small footprint

The Ovivo® Digestivore sidestream treatment system is a new process that incorporates two well established technologies namely – nitrification and membrane thickening.

Ovivo has over 30 years of experience with biological nutrient removal. In that time we have built plants that are able to meet the strictest nitrogen and phosphorus limits in the industry. The Ovivo Digestivore system leverages that body of experience to provide the most efficient and effective means for dealing with sidestream ammonia.

Membrane thickening is a rapidly growing application with Ovivo’s oldest installation approaching 10 years in operation. Ovivo has over 30 installations in the US including the largest membrane thickening system in the world which is able to handle the waste activated sludge from a 25 MGD wastewater plant. This experience provides Ovivo with the ability to optimize the design of the membrane thickening system so that owners get the greatest value from their limited capital budgets.

What is membrane thickening? Quite simply, membrane thickening can be thought of as a coffee filter. We leave solids on one side of the membrane while pulling clean water through to the other. We can increase the concentration the solids within the system 4-5 times more than other membranes without the need of any polymer or coagulants. The permeate removed from the solids is of superior quality with characteristics similar to permeate from an MBR.

What is sidestream treatment? Wastewater treatment is similar to any industrial production line in that it receives certain inputs while generating certain outputs. Within this system, some of the processes used produce waste streams that must be managed. One of the unique aspects of wastewater is the fact that most of the waste streams are sent back to the front of the system for re-processing. This re-processing ultimately lowers throughput capacity by consuming energy and resources that would normally be available for managing current inputs. Sidestream treatment addresses this by targeting the constituents within the waste stream, effectively minimizing their impacts on downstream processes.

Below is a process flow diagram for a typical WWTP using anaerobic digestion:

Below is the process flow diagram showing the Ovivo® Digestivore system:

As can be seen from the above diagram, our technology treats both the WAS coming from the secondary clarifiers as well as the filtrate coming from the dewatering equipment. The Ovivo Digestivore system utilizes membranes to thicken the WAS to a suitable concentration while using the microbial population within the WAS to convert the ammonia in the filtrate stream into nitrate.

This conversion is important for two reasons. First, in the typical WWTP process flow, the filtrate with its high ammonia concentration would be sent back to the front of the plant. This ammonia load can have significant impacts on the performance of the aeration basin and can limit a wastewater treatment plants ability to meet permit requirements. By converting the ammonia to nitrate, the process removes this load from the aeration basin allowing the plant to treat nitrogen more effectively. This feature is a critical point for those plants that are in areas with tight nitrogen limits in their permits. Secondly, nitrate is an effective chemical for odor control. By sending a permeate stream rich in nitrate to the headworks of the plant, the Ovivo Digestivore system will lower or eliminate the amount of chemicals the plant needs to purchase for odor control.

Why do you use two membrane thickening tanks?
At Ovivo we’ve found that once your solids concentration reaches a certain point, you need to lower your flux rates to prevent premature fouling. Thickening in two stages allows us to minimize the number of membranes by varying the flux rate depending on the thickening stage.

 

What if I have a TN limit instead of an NH3 limit?
For those plants that have a total nitrogen limit as opposed to an ammonia limit, we will minimize the nitrate present in the permeate through DO control. This will allow all of the nitrate in the permeate to be removed before it reaches the anoxic basins of the BNR process.

 

How much ammonia can the Digestivore sidestream treatment system remove?
Based on our pilot testing experience, the Digestivore system is capable of removing over 95% of the incoming ammonia.

 

What if I already have WAS thickening equipment at my plant?
The Ovivo Digestivore system can still be an effective and efficient means of treating sidestream ammonia. For those plants already possessing thickening equipment, we recommend doing a single stage system that will take the solids up to 2% while removing over 85% of the incoming ammonia. This approach minimizes the amount of thickening polymer an owner must purchase while maximizing the life cycle for their existing equipment.

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