Effect of influent substrate ratio on anammox process was studied in sequencing batch reactor. Operating temperature was fixed at 35 ± 1 °C. Influent pH and hydraulic retention time were 7.5 and 6 h, respectively. When influent NO-N/NH-N was no more than 2.0, total nitrogen removal rate (TNRR) increased whereas NH-N removal rate stabilized at 0.32 kg/(m d). ΔNO-N/ΔNH-N increased with enhancing NO-N/NH-N. When NO-N/NH-N was 4.5, ΔNO-N/ΔNH-N was 1.98, which was much higher than theoretical value (1.32). The IC of NO-N was 289 mg/L and anammox activity was inhibited at high NO-N/NH-N ratio. With regard to influent NH-N/NO-N, the maximum NH-N removal rate was 0.36 kg/(m d), which occurred at the ratio of 4.0. Anammox activity was inhibited when influent NH-N/NO-N was higher than 5.0. With influent NO-N/NH-N of 2.5-6.5, NH-N removal rate and NRR were stabilized at 0.33 and 0.40 kg/(m d), respectively. When the ratio was higher than 6.5, nitrogen removal would be worsened. The inhibitory threshold concentration of NO-N was lower than NH-N and NO-N. Anammox bacteria were more sensitive to NO-N than NH-N and NO-N. TNRR would be enhanced with increasing nitrogen loading rate, but sludge floatation occurred at high nitrogen loading shock. The Han-Levenspiel could be applied to simulate nitrogen removal resulting from NO-N inhibition.

As an efficient and cost-effective nitrogen removal process, anaerobic ammonium oxidation (ANAMMOX) could be well operated at suitable pH condition. However, pH shock occurred in different kinds of wastewater and affected ANANNOX process greatly. The present research aimed at studying the performance and kinetics of ANAMMOX granular sludge with pH shock. When influent pH was below 7.5, effluent NH -N deviated from theoretical value. Longer recovery time from pH 9.0 than from pH 6.0 indicated that alkaline surroundings inhibited anaerobic ammonium oxidizing bacteria (AAOB) greater. The sludge settling velocity was 2.15 cm/s at pH 7.5. However, it decreased to 2.02 cm/s when pH was 9.0. Acidic pH had little effect on sludge size, but disintegration of ANA-MMOX granule was achieved with pH of 9.0. The Bell-shaped (A) model and the Ratkowsky model were more applicable to simulate the effect resulting from pH shock on ANAMMOX activity (R 2 [ 0.95), and both could describe ANAMMOX activity well with pH shock. They indicated that q max was 0.37 kg DNH þ 4 -N/(kgMLSSÁd) at the optimum pH value (7.47) in present study. The minimum pH during which ANAMMOX occurred was 5.68 while the maximum pH for ANAMMOX reaction was 9.26. Based on nitrogen removal performance with different pH, strongly acidic (pH B 6.5) or alkaline (pH C 8.5) inhibited ANAMMOX process. Besides, ANA-MMOX appeared to be more susceptible to alkaline wastewater. Compared to extremely acidic condition (low pH), extremely alkaline condition (high pH) affected ANAMMOX granules much more.Electronic supplementary material The online version of this article

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Anaerobic ammonium oxidation (anammox) has been regarded as an efficient process to treat high-strength wastewater without organic carbon source. To investigate nitrogen removal performance of anammox in presence of organic carbon source can broaden its application on organic wastewater treatment. In this work, effect of carbon source on anammox process was explored. Operating temperature was set at 35 ± 1°C. Influent pH and hydraulic retention time were 7.5 and 6 h, respectively. Effluent [Formula: see text] was affected little with COD no more than 480 mg/L. Independent of carbon source content, nitrite removal rate was around 99%. The variation of [Formula: see text] lagged behind [Formula: see text] at high COD content, and pH could be used as an indicator for [Formula: see text] removal. Specific anammox activity dropped from 0.39 to 0.19  [Formula: see text] at COD=720 mg/L. The remodified logistic model was quite appropriate for describing the nitrogen removal kinetics and predicting the performance of anammox process in presence of carbon source.

BACKGROUND Simultaneous anammox and denitrification (SAD) can remove carbon and nitrogen. However, its performance is suppressed under saline surroundings. In this work, mannitol was used to enhance a SAD process treating saline wastewater. RESULTS The optimum carbon and nitrogen removal was achieved at 0.2 mmol L−1 mannitol, during which ammonium removal efficiency (ARE), nitrite removal efficiency (NRE) and chemical oxygen demand (COD) removal efficiency were 96.95%, 93.70% and 90.05%, respectively. The maximum ammonium removal rate (ARR), nitrite removal rate (NRR) and the specific anammox activity (SAA) were increased by 25.49%, 55.84% and 33.83% with optimum addition (0.2 mmol L−1 mannitol) respectively. The diameter of sludge was enlarged with the addition of mannitol (≤0.2 mmol L−1). The Tseng‐Wayman model was more suitable to simulate the whole SAD process. The modified logistic model, the modified Boltzman model and the modified Gompertz model were all appropriate to describe nitrogen removal in a typical cycle with the addition of mannitol. CONCLUSION Mannitol was effective in enhancing a SAD process treating saline wastewater, and maximum nitrogen removal was achieved at mannitol = 0.2 mmol L−1. The Tseng‐Wayman model satisfactorily predicted the whole SAD process treating saline wastewater with mannitol addition. © 2018 Society of Chemical Industry