Clean-water facilities face increasingly strict permit requirements, most notably for nitrogen and phosphorus. The cost to comply can be substantial.

Now Kruger, a Veolia business unit, offers the AnoxKaldnes Hybas process for sequencing batch reactors (SBRs). The company says the retrofit technology can enhance ammonia and total nitrogen removal in existing SBRs within the original system footprint.

The process is an innovative application of the company’s proven AnoxKaldnes fixed-film technology. It uses engineered moving bed media to grow and foster nitrifying bacteria, even at low solids retention times and low reactor temperatures. The process enhances nitrification capacity for ammonia removal.

With the addition of a recirculation process, the technology allows for both nitrification and denitrification to meet total nitrogen effluent limits, according to the manufacturer. Chris Thomson, product manager, talked about the process in an interview with Treatment Plant Operator.

What was the key reason behind bringing this offering to market?

Thomson: The real market driver was knowing that, given the current age of many SBR installations and the continuing evolution of nutrient regulations, a time would come when communities would face the need to upgrade their systems for ammonia or total nitrogen removal. For us, the question was how to apply our existing AnoxKaldnes technology to existing SBR systems to meet that need.

In simple terms, what is the AnoxKaldnes process?

Thomson: AnoxKaldnes has been around since the late 1980s and early 1990s. Anox based in Sweden was one company; Kaldnes based in Norway was another. Those two companies are now one and are part of the Veolia family. The technology takes the fixed-film biological treatment process and deploys it in a moving bed bioreactor (MBBR).

We add polyethylene media to a reactor, and instead of being fixed, the media is constantly moving. That allows nitrifying bacteria to grow on the media. The media has a very highly protected surface area, so the nitrifiers can grow without being washed out hydraulically. With this process we can achieve nitrification, and with some additional separation of tankage we can achieve denitrification, all in a very small footprint.

What is new and different about this latest offering?

Thomson: We have installed a number of MBBR and what we call IFAS (integrated fixed-film activated sludge) systems where we add media to achieve nitrification. What is new is the application of this technology to SBRs, where it has never been used before. In essence, we are applying a tried and true technology to the SBR process.

What if the facility’s need is for total nitrogen removal, as opposed to ammonia?

Thomson: If the need is for nitrification and denitrification, we can install a partition to segment off a non-media free anoxic zone where they can denitrify. That zone is constructed inside the existing tank, so it does not add to the footprint of the system.

How would you describe the fixed-film media used in this process?

Thomson: We use 100 percent virgin polyethylene for its durability. The media looks almost like pasta wheels, about the size of a quarter. It has a very high surface area. For example, K5 media, which we use most often, has 800 square meters of surface area for every cubic meter of media we supply. There are multiple ridges and surfaces where the biofilm can grow. That’s where the nitrifiers develop and reside. They are protected almost like snails in their shells. With constant agitation and movement, the biomass does slough off, so that prevents clumping and the development of septic conditions.

How does the technology work in the SBR environment?

Thomson: Our typical polyethylene media has a specific gravity less than 1, so it floats. For SBRs, we developed a new media that uses our existing geometry but has a specific gravity greater than 1. That allows the media, instead of floating, to sink with the biomass during the SBR’s settle cycle. We added a stainless steel screen to retain the media in the SBR tank.

Does the process require upgrade or replacement of existing SBR controls?

Thomson: Yes. We have instrumentation and controls specialists on staff who would be involved in any SBR retrofit. We provide a complete solution in which we do the design and install the capital equipment, instrumentation and controls. We provide a performance guarantee on the process.

How would you summarize the benefits of this process for an existing SBR?

Thomson: This process is designed for retrofitting SBR systems that have reached or are nearing their capacity for ammonia or total nitrogen removal. We can increase that capacity by up to 30 percent and do it in the same footprint. So for agencies thinking about expanding their facility by adding tankage to meet more stringent ammonia or total nitrogen limits, this process can be an appealing alternative.

Can this process enable facilities to increase absolute treatment capacity in the event nitrogen or ammonia removal is not a critical need?

Thomson: The chief driver of this process is nitrification/denitrification. It is not tailored for additional BOD removal.

What has been done to demonstrate the viability of the process in SBRs?

Thomson: We have completed pilot testing at the North Durham Water Reclamation Facility in Durham, North Carolina. We proved the concept there and also developed the proper loading rates and parameters for treatment. We have also validated the basic treatment concept on municipal wastewater. We’ve installed more than 50 municipal AnoxKaldnes systems in the United States and about 600 worldwide, in multiple geometries — circular tanks, long-flow reactors and square reactors. SBRs are just another treatment mode in which we can retrofit the AnoxKaldnes media.

How would you assess the size of the market for this technology?

Thomson: Our research indicates that there are more than 500 existing SBRs in the United States and Canada and more than 1,300 in total worldwide. A number of these are industrial systems. They are generally smaller systems, about 1 mgd and less.