Sludge Liquor Nitritation using advanced Biocatalysts: PRESENTATION ONLY

Nair, A., Microvi Biotech, UK


Conventional biological ammonia removal relies upon the growth of Ammonia Oxidising Bacteria (AOB) and Nitrite Oxidising Bacteria (NOB) to convert ammonia to nitrate. This process is energy intensive requiring 4.6 mg/l oxygen per mg of ammonia oxidised.

Ammonia shortcut pathways can significantly reduce this energy consumption by avoiding the conversion of nitrite to nitrate and/or using a partial conversion to nitrite followed by simultaneous ammonia and nitrite conversion to nitrogen gas. Not only does this reduce energy, but it also reduces the carbon required to meet total nitrogen consents.

To achieve shortcut pathways, careful system control is required to suppress the growth of NOBs.  This can result in complex control systems and a heavy reliance on instrumentation.

Microvi have created the disruptive MicroNiche Engineering (MNE™) platform technology which is used to create specific habitats in which to retain especially selected organisms.  This use of biomimicry improves process performance and flexibility of application by naturally altering microorganism behaviour.

Piloting of Microvi’s Aerovi™ biocatalyst in high strength digestor liquors has demonstrated an intrinsic control of nitrate formation, achieving 90% conversion of Ammonia entirely to Nitrite without the requirement for any control of solids, redox, sludge age or flow.  This has the potential to significantly improve the process reliability of shortcut pathway processes.

The process piloted was a single pass reactor with aeration via fine bubble diffused aeration, no DO control or pre-treatment for solids management.  The simplicity of the system coupled with the high performance led to the Oro Loma Sanitary Department (OLSD) converting a disused concrete basin into a fullscale liquor treatment process.

This is the first fullscale installation of Microvi MNE in this application, and it provides OLSD with increased protection of their new Total Nitrogen limit plus reduced aeration and carbon requirements.

Whilst aiming to achieve full nitritation on the main plant, operating at higher ammonia loading rates would allow partial conversion to nitrite providing a perfect enabling process for shortcut nitrogen removal without extensive control or upfront conditioning requirements.  The Microvi MNE process has the potential to improve upon the economics of ammonia removal is a simple treatment process.

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