Distribution of Nitrifying Bacteria Under Fluctuating Environmental Conditions

Abstract

Engineered systems that mimic tidal wetlands are ideal for point-of-source treatment of wastewater due to their low energy requirements and small physical footprint. In this study, vertical columns were constructed to mimic the flood-and-drain cycles of tidal wetland treatment systems (TWTS) in order to study how variations in the

Effect of Tidal Cycling Rate on the Distribution and Abundance of Nitrogen-Oxidizing Bacteria in a Bench-Scale Fill-and-Drain Bioreactor

“…Two parameters were manipulated in this study: N load (high vs. low) and cycling frequency (24,16,8, and 4 fill-and-drain events per day). Unfortunately, because of the relatively large size of these reactors and the considerable infrastructure necessary to control flow, it was not feasible to maintain multiple reactors of each N × cycling-frequency combination.…”

“…For example, after the samples for the "24 cycles per day" treatment were collected, cycling was changed to 16 per day and allowed to equilibrate for 4 weeks prior to collecting the "16 per day" microbial samples. The reset period of 4 weeks was chosen based on preliminary studies described in Battistelli [24], which demonstrated that this amount of time was adequate for effluent water chemistry (specifically NH 4 + , NO 2 − , and NO 3 − concentrations) to stabilize following disturbances associated with both increases (e.g., 4 cycles to 24 cycles) and decreases (24 to 16) in cycling frequency.…”

“…The vertical distribution of abundance for each bacterial group under each set of cycling conditions was compared, and Figure 2 shows representative graphs for the fastest (24) and slowest (4) cycling rates. When the high-N reactor was operated at 24 cycles day −1 (Figure 2a), a significant increase in abundance was observed with depth for total bacteria, AOB, and NOB (Table 1); a similar change in AOB and NOB was evident in the low-N reactor (Figure 2b).…”