Achieving stable nitrogen removal performance of mainstream PN-ANAMMOX by combining high-temperature shock for selective recovery of AOB activity

How to Provide Nitrite Robustly for Anaerobic Ammonium Oxidation in Mainstream Nitrogen Removal

“…Specifically, applying high temperature to suppress NOB can only be more feasible in WWTPs in tropical zones (e.g., Singapore) than in other areas where temperature seasonally varies. , Likewise, high FA and FNA are considered as the most effective factors to stress NOB for ammonium-rich wastewater. , The FA and FNA concentrations of 5–20 mg N/L of and 0.02–0.2 mg N/L could achieve effective inactivation of NOB, while the half inhibition concentration of FA and FNA to AOB are high at 210 mg N/L and 0.2 mg N/L, respectively. , So, AOB have displayed a quicker recovery rate than NOB when are inhibited by FA and FNA. , It was previously thought that this selective inhibition could be easily achieved in high-strength ammonium wastewater treatment (such as anaerobic digestion (AD) liquor) and would be difficult for mainstream treatment, as the high ammonium and nitrite concentrations are necessary to produce relatively high FA and FNA concentrations with pH 7.5–8.6 at 20–35 °C. ,, The threshold of FA in the mainstream-like wastewater can be achieved by maintaining high temperature, whereas the adjustment of the temperature of wastewater seems unfeasible given the huge volume of daily treatment. Currently, in situ FNA inhibition of NOB in an acidic PN process (pH < 5.0) proved feasible for mainstream wastewater treatment. ,, In practice, acidic conditions could be obtained by decreasing the influent alkalinity through the use of ferric salt in CEPT .…”

“…43,45 It was previously thought that this selective inhibition could be easily achieved in high-strength ammonium wastewater treatment (such as anaerobic digestion (AD) liquor) and would be difficult for mainstream treatment, as the high ammonium and nitrite concentrations are necessary to produce relatively high FA and FNA concentrations with pH 7.5−8.6 at 20−35 °C. 14,61,70 The threshold of FA in the mainstream-like wastewater can be achieved by maintaining high temperature, 30 whereas the adjustment of the temperature of wastewater seems unfeasible given the huge volume of daily treatment. Currently, in situ FNA inhibition of NOB in an acidic PN process (pH < 5.0) proved feasible for mainstream wastewater treatment.…”

“…The previous studies on NOB suppression strategies in mainstream PN mostly rely on using single-parameter control based on kinetic selection mechanisms (i.e., decreasing growth kinetic or increasing decay kinetic due to substrate limitations or inhibition). 7 The typical single-parameter control strategies include NOB washout by short SRT, 38 differentiating the activity of AOB from NOB by high temperature, 30 oxygenlimited operation, 85 and nitrite starvation, 86 as well as inactivating NOB by inhibitors and biocidal factors, selectively. 61,87 However, so far, there is no consensus on the effective NOB suppression and robust nitrite supply in a pilotscale mainstream treatment.…”

“…Indeed, although more than 200 full-scale partial nitrification-anammox (PN/A) facilities have been applied worldwide in treating nitrogenous wastewater to date, such as digestate, reject water, and landfill leachate, − only rare instances of pilot- or full-scale anammox engineering implementations have been reported in treating mainstream characterized by a low-strength (20–50 mg N/L), high flow rate (360 billion m 3 /year, globally), and large nitrogen discharge amount (9.25–23.13 billion kg ammonium/year, globally). ,,, Researchers and practitioners are wondering whether PN/A is suitable for mainstream treatment, because the low ammonium concentrations and low temperatures of a mainstream would generally reduce the biological activity of anammox bacteria (AnAOB) and restrict the effective washout of nitrite-oxidizing bacteria (NOB). − Nevertheless, AnAOB have been widespread found in WWTPs, and have shown adaptation to low temperature (10–20 °C) in WWTPs of nontropical regions. ,, Also, the prevalence of the warm side stream anammox treatment would favor mainstream anammox by providing substantial amounts of active anammox biomass. ,, Therefore, it might be the unstable nitrite supply rather than anammox biomass availability that had greatly limited the implementation of mainstream anammox.…”

“…Extensive advancements have been made in partial nitrification (PN) under laboratory conditions, and a fixed mind-set has been established to suppress NOB by hostile environments or stressful factors, such as low dissolved oxygen (DO), , short sludge retention time (SRT), , high temperature, nitrite starvation, , acidic condition, , free ammonia (FA), , free nitrous acid (FNA), , residual ammonium, or light irradiation . However, the adaptation of NOB to these stressful factors had been frequently reported. , Especially, the NOB genus varies when encountering the stressful factors. , In WWTPs, Nitrobacter , Nitrospira , and Candidatus ( Ca .)…”