Haiyuan Ma

Process stability and the recovery control associated with inhibition factors in a UASB-anammox reactor with a long-term operation.

A UASB-anammox reactor was operated for 900 days to study its process stability. The negative effects of free ammonia (FA) and free nitrous acid (FNA) were investigated over three separate inhibitions and recoveries. The IC10, IC50 and IC90 (inhibitory concentration/a 10%, 50% and 90% activity loss) of FNA and FA responding to the NH4(+)-N, NO2(-)-N and TN removal efficiency were evaluated. In the 1st inhibition, the average FNA-IC10 observed was 0.67 μg L(-1) and the FA-IC10 for TN removal was 4.85 mg L(-1). In the 2nd inhibition, an FNA-IC10 of 0.44μ g L(-1) and an FA-IC10 of 3.56 were found. In the 3rd inhibition, however, both the FNA-IC10 and FA-IC10 were found to have increased, with values of 0.50 μg L(-1) and 4.42 mg L(-1), respectively. A clear control region was established for multiple inhibitions and the recoveries, which followed (pH 7.5-8.5, FA below 10mg/100mg NH4(+)-N and an FNA below 0.005 mg/100 mg NO2(-)-N) for the purpose of optimizing the operation conditions of the UASB-anammox reactor.

Long-term operation performance and variation of substrate tolerance ability in an anammox attached film expanded bed (AAFEB) reactor.

An anammox attached film expanded bed (AAFEB) reactor was operated to study the long-term performance and the variation of substrate tolerance ability. The results indicated that the nitrogen loading potential (NLP) was significantly enhanced from 13.56gN·(L·d)(-)(1) to 20.95gN·(L·d)(-)(1) during the stable operation period. The inhibitory concentration of 10% (IC10) for free ammonia (FA), free nitrous acid (FNA) and SNinf (diluted substrate concentration) increased from 18mg/L, 12μgL(-1) and 370mgNL(-)(1) to 31mg/L, 19μgL(-1) and 670mgNL(-)(1), respectively. However, the substrate shock of 2500mgNL(-)(1) for 24h terribly weakened the treatment performance and substrate tolerance ability of the reactor. The results of batch tests indicated that the existence of lag phase made the AAFEB reactor more vulnerable to substrate variation. The SNinf was accurate to be used to monitor the reactor performance and should be maintained below 320mgNL(-)(1) to ensure the absolute stable operation.

Substrate inhibition and concentration control in an UASB-Anammox process

An UASB-Anammox reactor was operated for more than one year to study the process performance variations respond to the nitrogen loading rate (NLR) and substrate concentration. The IC10 (451.1mg/L), IC50 (725.3mg/L) and the prospected threshold of influent total nitrogen (TN) concentration were simulated. A stable TN removal efficiency was obtained when the TN influent was controlled. The disequilibrium distribution of the substrate following the plug flow with the height of the reactor resulted in significant variations in specific Anammox activity from the bottom to the top of the reactor (348→3mgN/gVSS/d). With long term acclimation, the nitrogen removal capacity of Anammox sludge varied significantly, with the most activated sludge obtained in the bottom part a 100 times capacity greater than that of the top. A stable performance with high removal efficiency in the constructed UASB-Anammox reactor was obtained when the influent TN concentration was below 451.1mg/L.

The Treatment Performance and the Bacteria Preservation of Anammox: A Review

Because of the low energy costs in the absence of the need for aeration, the non-requirement of a carbon source and alkali, and the reduced production of excess sludge, anaerobic ammonia oxidation (Anammox) has been extensively studied as an alternative to the conventional nitrification–denitrification pathway for biological nitrogen removal from wastewater. However, many challenges remain which need to be overcome to prepare the process for engineering application. These include the long doubling time of Anammox bacteria/autotrophic ammonia-oxidizing bacteria (AAOB), the low tolerance capacity to substrate concentration, and high sensitivity to various environmental factors. This review article focuses on the main drawbacks of the Anammox process and evaluates the progress made to date with regard to the enrichment of AAOB and the treatment performance of the Anammox process itself. The factors affecting the nitrogen removal performance of the Anammox process, such as substrate concentration, organic matters, and variation of temperature, are also reviewed and discussed. Finally, the need for the development of long-term storage methods for AAOB is addressed.

Effects of soluble microbial products (SMP) on the performance of an anammox attached film expanded bed (AAFEB) reactor: Synergistic interaction and toxic shock

The accumulation of soluble microbial production (SMP) in an anammox attached film expanded bed (AAFEB) and its effect on the reactor performance were investigated in this study. During the long-term experiment, an extended HRT resulted in the accumulation of SMP and the change of treatment performance. When the SMP increased from 10.5±1.5mgL-1 to 31.7±6.4mgL-1 with the increase of influent TN concentration from 313mgL-1 to 2500mgL-1, the TN removal efficiency was stable. However, when the influent TN concentration was 3500mgL-1, the SMP concentration increased higher than 100mgL-1, the reactor soon became inhibited. Bath tests indicated that both the specific anammox activity (SAA) and the substrate tolerance ability decreased during the stable operation phases, whereas the specific denitrification activity (SDA) was significantly enhanced. In addition, N2O emissions in the anammox-denitrifier symbiotic system were greater than in the conventional nitrogen removal process.

Stoichiometric variation and loading capacity of a high-loading anammox attached film expanded bed (AAEEB) reactor

The nitrogen loading rate (NLR) of an anammox attached film expanded bed (AAFEB) reactor was increased from 5.0 to 60.0 gN/L/d. During the stable operational period, the TN removal efficiency maintained at 87.3 ± 2.5%, and a maximum nitrogen removal rate (NRR) of 44.9 ± 0.3 gN/L/d was achieved. Overload resulted in the sharp deterioration of reactor performance, the ratio of (Food/Microorganism)/SAA should be maintained at lower than 66 ± 7% to ensure the stable operation of the AAFEB reactor. New stoichiometric equations for the anammox process under the low NLR condition (5.0 gN/L/d) and the high NLR condition (50.0 gN/L/d) were proposed. The quantitative SAA-cytochrome heme C relationship was established for the first time that providing a simple way for monitoring the reactor performance. Substrate tolerance ability was significantly increased that proving the stability of the AAFEB reactor was continuously enhanced during the stable operational periods.

Effects of substrate shock on extracellular polymeric substance (EPS) excretion and characteristics of attached biofilm anammox granules

Environmental stresses are assumed to significantly impact the content and concentration of produced extracellular polymeric substances (EPS) and therefore influence the performance of an ananmmox attached film expanded bed (AAFEB) reactor. In this study, a transient high substrate concentration of 2500 mg N L−1 (calculated as the sum of NN4+–N and NO2−–N) for 24 hours stimulated abundant EPS excretion as well as deterioration of anammox granules. The results indicated that a high EPS concentration of 89.6 ± 48.3 mg g−1 VSS resulted in 35.0 ± 0.8% decrease in the granule settling properties and 30.5 ± 0.9% reduction in the total VSS amount. The production of EPS was reasonably attributed to the impact of utilization-associated and stress-associated effects by the substrate. The results of a series of batch experiments indicated that a rapid increase of loosely-bound EPS (LB-EPS) from 41.2 to 114.6 mg g−1 VSS occurred when the substrate concentration steadily increased from 400 to 1000 mg N L−1, in contrast, the tightly-bound EPS (TB-EPS) remained stable at 32.5 ± 2.8 mg g−1 VSS. Thus, the LB-EPS was considered the key factor for the deterioration of granule stability and the substrate concentration should be controlled below 400 mg N L−1 to avoid triggering the accumulation of LB-EPS. Furthermore, the formation and disintegration mechanisms of attached film anammox granules were also elucidated in this study.

A new process for simultaneous nitrogen removal and phosphorus recovery using an anammox expanded bed reactor

Phosphorus recovery from wastewater is an important approach for sustainable phosphorus use. In this work, a process combining anammox and hydroxyapatite (HAP) precipitation in an expanded bed reactor for simultaneous nitrogen removal and phosphorus recovery was developed by applying specific Ca/P ratio and pH control. A high phosphorus removal rate (0.14 ± 0.01 kg-P/m3/d) was obtained while a stable nitrogen removal efficiency (87.4 ± 2.9%) maintained with an effluent recirculation system applied. Average 13.4% phosphorus (30.7% in P2O5) accumulation in the dry sludge and a Ca/P ratio very close to HAP was observed by quantitative elemental analysis. In this work, different analysis revealed the two layers structure with anammox biofilm attached to inorganic core of the granules. Different spectral analysis determined the major phase of the inorganic content as hydroxyapatite. With proper Ca/P ratio and pH control, anammox expanded bed reactor was transformed into an efficient process to simultaneously remove nitrogen and recover phosphorus.

Nutrient recovery technologies integrated with energy recovery by waste biomass anaerobic digestion

Anaerobic digestion widely considered as a promising waste biomass disposal treatment approach, is attracting increasing interest in all corners of the globe. However, due to the specific features of different types of waste biomass, the bioenergy conversion efficiency of this process is not ideal. Another problematic aspect of anaerobic digestion is that the nutrient rich effluent sometimes needs to be treated before discharge. This review presents the recent achievements of waste biomass digestion from the perspective of energy recovery and nutrient recovery. In this work, the anaerobic treatment characteristics of common types of waste biomass are summarized and compared. With a focus of nutrient recovery and post treatment issues, the challenges and technical hurdles encountered in the anaerobic digestion of waste biomass are critically reviewed. Finally, an integrated system of anaerobic digestion, anaerobic ammonia oxidation (anammox) and phosphorus recovery is proposed for efficient energy and nutrient recovery from waste biomass.