Simultaneous nitrification and denitrification in biofilters with real time aeration control

Abstract

The aim of this article is to present a new biological aerated filter (BAF) for nitrogen removal based on simultaneous nitrification and denitrification. Contrary to the systems which integrate both an aerated and a non-aerated zone to allow complete nitrogen removal in one compact or two different units (pre-denitrification and nitrification), this upflow BAF system is based on the principle of simultaneous nitrification and denitrification since the filter is completely aerated. The denitrification process is possible due to the diffusion effect which dominates biofilm processes. The real time aeration control allows us to maintain a low dissolved oxygen value (0.5 to 3 mg O2/l). In this case, the biofilm will not be fully (or less) penetrated with oxygen and denitrification will be carried out in a large part of the biofilm. Therefore, nitrification and denitrification is running simultaneously in different depths of the biofilm. By using 50% less air this BAF gave the same results (less than 20 mg TN/l) on pilot plant as a classical nitrification and denitrification BAF (Toettrup et al., 1994). Less recirculation was necessary to achieve the same denitrification.

Biological nitrogen and phenol removal from saline industrial wastewater by submerged fixed-film reactor

“…Similarly, authors such as Punzava et al [25], who combined processes of nitrification and denitrification in the same biofilm reactor, observed that denitrification occurred in spite of the presence of oxygen.…”

Treatment of dairy wastewater with a membrane bioreactor

“…Nevertheless, this phenomenon may occur due to a reduced efficiency of oxygen transfer provided by a high concentration of biomass and high viscosity of the medium. In this manner, the inner regions of the biological flocs possibly did not receive oxygen and became anoxic zones, thereby providing favorable conditions for denitrification (Puznava et al, 2000). Moreover, since sludge growth was high, part of the total nitrogen removal may result from a higher nutrient uptake.…”

A wastewater treatment using a biofilm airlift suspension reactor with biomass attached to supports: a numerical model

“…In the wastewater treatment systems that use an attached biomass, the total balance of the nitrogen in the liquid phase is often not satisfied because anoxic conditions can occur in the deeper areas of the biofilm, allowing for the denitrification even if dissolved oxygen is still present in the liquid phase (Walters et al 2009;Okabe et al 1996;Satoh et al 2004). In addition, Pochana and Keller (1999) and Puznava et al (2001) show that the simultaneous nitrification and denitrification (SND) could occur as a consequence of the DO concentration gradients within microbial flocs or biofilms. Nitrifiers will develop on the surface of the biofilm where there are rather high DO levels, whereas denitrifiers will be present inside the biofilm due to the low levels or absence of oxygen.…”