The enrichment characterisation of Nitrospira under high DO conditions.

Nitrite-oxidizing bacteria (NOB) are crucial to nitrification and nitrogen elimination in wastewater treatment. Mass reports exist on the links between NOB and other microorganisms, for instance, ammonia-oxidizing bacteria (AOB). However, a few studies exist on the enrichment characterisation of NOB under high dissolved oxygen (DO) conditions. In this study, NOB was designed to be enriched individually under high DO conditions in a continuous aeration sequencing batch reactor (SBR), and the kinetic characterisation of NOB was evaluated. The analysis revealed that the average NO2--N removal rate was steady above 98%, with DO and NO2--N being 3-5 mg L-1 and 50-450 mg L-1, respectively. The NO2--N removal efficiency of the system was significantly enhanced and better than in other studies. The high-throughput sequencing suggested that Parcubacteria_ genera_incertae_sedis was the first dominant genus (21.99%), which often appeared in the NOB biological community with Nitrospira. However, the dominant genus NOB was Nitrospira rather than Nitrobacter (8.49%). This result suggested that Nitrospira was capable of higher NO2--N removal. But lower relative abundance indicated that excessive NO2--N had an adverse effect on the enrichment and activity of Nitrospira. In addition, the nitrite half-saturation constant (KNO2) and the oxygen half-saturation constant (KO) were 1.71 ± 0.19 mg L-1 and 0.95 ± 0.10 mg L-1, respectively. These results showed that the enriched Nitrospira bacteria had different characteristics at the strain level, which can be used as a theoretical basis for wastewater treatment plant design and optimisation.

Achieving partial nitrification: A strategy for washing NOB out under high DO condition.

This study investigated the effect of high DO concentrations on PN. The experimental setup involved operating at high DO concentrations (1.5-2.5 mg/L) and environmental temperatures (15-20 °C) over a period of 180 days. Through a sludge enrichment process, the kinetic parameters of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) were determined. Surprisingly, contrary to conventional reports, it was observed that NOB exhibited a stronger affinity for DO compared to AOB. As a result, high DO concentrations were necessary to provide favorable conditions for the growth of AOB. In order to establish PN, strategies including intermittent aeration, free ammonia (FA), and controlled sludge retention time (SRT) were employed. The successful PN was achieved with a specific ammonia oxidation rate of 24 mg N/g MLVSS/h and a specific nitrite oxidation rate below 0.10 mg N/g MLVSS/h. The nitrite accumulation rate (NAR) was maintained at 100% during stable operation. The abundance of Nitrosomonas, a typical genus of AOB, was found to be 68.62%, which surpasses previous studies in similar research. A slightly higher DO concentrations may increase energy consumption, but achieve higher efficiency and stability in PN. This study provided new insights into the application of PN in wastewater treatment.

Migration and adsorption of naphthalene in road-deposited sediments from stormwater runoff: Impact of the particle size.

In this study, we explored the impact of RDS particle size on the migration dynamics of RDS and naphthalene through rigorous wash-off experiments. The results illuminated that smaller RDS particles showed higher mobility in stormwater runoff. On the other hand, RDS particles larger than 150 µm showed migration ratios below 2 %, suggesting that naphthalene adsorbed on larger RDS primarily migrated in dissolved form. Furthermore, we investigated the migration behaviors of RDS and naphthalene under varied conditions, including rainfall intensity, duration, and naphthalene concentrations. Larger rainfall intensity promoted the naphthalene release from RDS, while long rainfall duration (≥10 min) impeded the migration velocities (≤2.91 %/5 min for RDS, and ≤3.32 %/5 min for corresponding naphthalene) of RDS and naphthalene. Additionally, higher naphthalene concentrations in RDS diminished migration ratios of dissolved naphthalene. Significantly, the maximum uptake of naphthalene on RDS was 6.02 mg/g by the adsorption Langmuir isotherm. Importantly, the adsorption process of naphthalene in RDS is primarily governed by the physical adsorption, as demonstrated by the successive desorption experiments, which showed the desorption rate of up to 87.32 %. Moreover, advanced characterizations such as XPS, FTIR and Raman spectra further confirmed the physical nature of the adsorption process. These findings may help the understanding of the migration behavior of other pollutants in urban surface particulates.

Influencing factors on the activity of an enriched Nitrospira culture with granular morphology.

Nitrospira is a common genus of nitrite-oxidising bacteria (NOB) found in wastewater treatment plants (WWTPs). To identify the key factors influencing the composition of NOB communities, research was conducted using both sequencing batch reactor (SBR) and continuous flow reactor under different conditions. High-throughput 16S rRNA gene sequencing revealed that Nitrospira (18.79% in R1 and 25.77% in R3) was the dominant NOB under low dissolved oxygen (DO) and low nitrite (NO2--N) concentrations, while Nitrobacter (21.26% in R2) was the dominant NOB under high DO and high NO2--N concentrations. Flocculent and granule sludge were cultivated with Nitrospira as the dominant genus. Compared to Nitrospira flocculent sludge, Nitrospira granule sludge had higher inhibition threshold concentrations for free ammonia (FA) and free nitrous acid (FNA). It was more likely to resist adverse environmental disturbances. Furthermore, the effects of environmental factors such as temperature, pH, and DO on the activity of Nitrospira granular sludge were also studied. The results showed that the optimum temperature and pH for Nitrospira granular sludge were 36°C and 7.0, respectively. Additionally, Nitrospira granular sludge showed a higher dissolved oxygen half-saturation constant (Ko) of 3.67 ± 0.71 mg/L due to its morphological characteristics. However, the majority of WWTPs conditions do not meet the conditions for the Nitrospira granular sludge. Thus, it can be speculated that future development of aerobic partial nitrification granular sludge may automatically eliminate the influence of Nitrospira. This study provides a theoretical basis for a deeper understanding of Nitrospira and the development of future water treatment processes.

Recovery of value-added products by mining microalgae.

Microalgae blooms are always blamed for the interruption of the aquatic environment and pose a risk to the source of drinking water. Meanwhile, microalgae as primary producers are a kind of resource pool and could benefit the environment and contribute to building a circular economy. The lipid and polyhydroxybutyrate (PHB) in the cells of microalgae could be alternatives to fossil fuels and plastics, respectively, which are the culprits of global warming and plastic pollution. Besides, some microalgae are rich in nutrients, such as proteins and astaxanthin, which make themselves suitable for feed additives. As wastewater is rich in nutrients necessary for microalgae, thus, value-added product recovery via microalgae could be an approach to valorizing wastewater. However, a one-size-fits-all approach deploying various wastewater for the above products cannot be summarized. On the contrary, specific technical protocols should be tailored regarding each product in microalgae biomass with various wastewater. Thus, this review is to summarize the research effort by far on wastewater-cultivated microalgae for value-added products. Wastewater type, regulation methods, and targeted product yields are compiled and discussed and are expected to guide future extrapolation into a commercial scale.

[Accelerated Degradation of Aqueous Recalcitrant Iodinated Contrasting Media Using a UV/SO32- Advanced Reduction Process].

Based on the formation of free radical-hydrated electrons by the activation of sulfite (SO32-), the UV/SO32- process is an advanced reduction process that can reduce pollutants. This study investigated the degradation kinetics, mechanism, influencing factors, and degradation pathways of sodium diatrizoate (DTZ), an iodinated contrasting media, during the UV/SO32- process. The degradation kinetics of DTZ were well fitted by the pseudo-first-order model, the degradation rate of which was higher than that of UV only and UV/H2 O2. The degradation rate of DTZ during the UV/SO32- process was positively correlated with the initial SO32- concentration. Weakly alkaline and alkaline conditions promoted the degradation of DTZ, while organic matter inhibited degradation during the UV/SO32- process. The degradation mechanism included direct photolysis and free radical attack, whereby free radical attack played a more important role than direct photolysis. Sulfite radicals dominated DTZ degradation efficiency, and hydrated electrons controlled the deiodination efficiency. The degradation pathways of DTZ during the UV/SO32- process included substitution, decarboxylation-hydroxylation, and amide bond cleavage.

Simultaneous control of soil erosion and arsenic leaching at disturbed land using polyacrylamide modified magnetite nanoparticles.

Rapid urbanization and human disturbance of land often results in serious soil erosion and releases of fine sediments and soil-bound toxic metals/metalloids. Yet, technologies for simultaneously controlling soil erosion and metals/metalloids leaching have been lacking. This study developed a new class of polyacrylamide-dispersed magnetite (PAM-MAG) nanoparticles and tested the effectiveness for simultaneous control of soil erosion and arsenic leaching from a model soil. Two parallel box test setups (L × W × H: 91.4 × 30.5 × 7.6 cm) were constructed to test the releases of sediments and soluble pollutants from the surface soil under simulated rainfall conditions (intensity = 11.15 cm/hr). A sandy loam soil from a local quarry mining site was used as the model soil, and arsenate As(V) as a prototype leachable metalloid. A stable dispersion of PAM-MAG was prepared with 0.3 wt% of PAM and 0.1 g/L as Fe of magnetite. The results indicated that treating the soil with 5.985 g/m2 of PAM-MAG was able to decrease cumulative soil mass loss in the runoff by 90.8% (from 254.50 ±â€¯0.10 g to 23.35 ±â€¯3.19 g), or turbidity of the runoff by 79.9% (from 244.5 ±â€¯27.5 NTU to 49.2 ±â€¯22.5 NTU). Compared to PAM only, the PAM-MAG suspension showed a 30% reduction of viscosity, allowing for easier application and transport of the nanoparticles in soil. Concurrently, the PAM-MAG treatment also immobilized 82.5% of water-leachable arsenate compared to untreated controls. Fourier-transform infrared (FTIR) spectroscopy analyses revealed that arsenate was immobilized by magnetite nanoparticles through inner sphere surface complexation (Fe-O-As). Overall, the PAM-MAG based technology holds the promise for simultaneously controlling soil erosion and metal/metalloid releases from disturbed land.

Impact of an Extreme Winter Storm Event on the Coagulation/Flocculation Processes in a Prototype Surface Water Treatment Plant: Causes and Mitigating Measures.

Climate change has often caused failure in water treatment operations. In this study, we report a real case study at a major surface water treatment plant in Alabama, USA. Following a severe winter storm, the effluent water turbidity surged to >15.00 Nephelometric Turbidity Units (NTU), far exceeding the 0.30 NTU standard. As a result, the plant operation had to be shut down for three days, causing millions of dollars of losses and affecting tens of thousands of people. Systematic jar tests were carried out with sediment samples from 22 upstream locations. The coagulation and settleability of sediment particles were tested under simulated storm weather conditions, i.e., low temperature (7 °C) and in the presence of various types and concentrations of natural organic matter (NOM) that was extracted from the local sediments. Experimental results proved that elevated NOM (6.14 mg·L-1 as Total Organic Carbon, TOC) in raw water was the root cause for the failure of the plant while the low temperature played a minor but significant role. Pre-oxidation with permanganate and/or elevated coagulant dosage were found effective to remove TOC in raw water and to prevent similar treatment failure. Moreover, we recommend that chemical dosages should be adjusted based on the TOC level in raw water, and a reference dosage of 0.29 kg-NaMnO4/kg-TOC and 19 kg- polyaluminum chloride (PACl) /kg-TOC would be appropriate to cope with future storm water impacts. To facilitate timely adjustment of the chemical dosages, the real time key water quality parameters should be monitored, such as turbidity, TOC, Ultraviolet (UV) absorbance, pH, and color. The findings can guide other treatment operators to deal with shock changes in the raw water quality resulting from severe weather or other operating conditions.

[Operation Characteristics of the Biofilm CANON Reactor During the Temperature Reduction Process].

The focus of this paper, was low temperature, high ammonia nitrogen wastewater. The operation characteristics of the biofilm CANON process during the temperature reduction process were determined, by continuously adjusting different operating conditions. The aim was to explore the methods needed for the CANON process to obtain stable shortcut nitrification and a good nitrogen removal effect, when the influent NH4+-N concentration is high and the temperature low. The results showed that, ① compared with the biofilm CANON reactor temperature changing from medium to low temperature directly (30℃±1℃→19℃), it was more conducive to adapt the nitrogen-removing bacteria to the low-temperature environment, while the temperature was gradually lowered. Moreover, the extent of each reduction should be minimized. Besides, the operating conditions should be adjusted to ensure the nitrogen removal effect. ② The temperature was gradually reduced to about 19℃ after 25 d, and then decreased to about 15℃ after another 18 d. The NH4+-N and TN removal rates could be respectively stable at 90% and 70% over a long period of time. The TN removal rate and removal load could still reach 72.52% and 0.78 kg·(m3·d)-1, respectively, even when the temperature dropped to 12℃. ③ When adapting biological CANON sludge during the temperature reduction process, shortcut nitrification should be given priority. A stable shortcut nitrification effect should be obtained by maintaining a certain concentration of residual NH4+-N, and by strictly controlling the DO concentration to restrain NOB activity.

Adsorption of myo-inositol hexakisphosphate in water using recycled water treatment residual.

Dissolved organic phosphorus (DOP) in rainwater runoff or other contaminated waters can cause or aggravate eutrophication of water bodies. Water treatment residual (WTR) containing spent coagulant has been shown to provide excellent adsorption capacity for inorganic phosphorus such as orthophosphate, but little information has been available on adsorption of DOPs by WTR. In this study, the adsorption characteristics of myo-inositol-1,2,3,4,5,6-hexakisphosphate (IHP), a prototype DOP in soil and stormwater, by WTR were investigated through batch adsorption equilibrium and kinetic experiments. The influences of pH and various size fractions of WTR on the adsorption capacity were tested and analyzed, and the adsorption mechanism was elucidated based on Fourier-transform infrared spectroscopy (FTIR) analysis. The experimental results showed that WTR can effectively adsorb IHP from simulated rainwater, and the IHP uptake was favored under neutral and acidic conditions. Moreover, the 1.0-2.0-mm fraction of the WTR particles was most suitable for practical application because of the well-balanced adsorption rate and capacity. The classical Langmuir isotherm model well described the equilibrium adsorption data and the pseudo-second-order kinetic model adequately interpreted the rate data. Thermodynamic analysis revealed that the adsorption is a spontaneous, endothermic, and entropy-driven reaction. The FTIR analysis indicated that adsorption of IHP on WTR is associated with the formation of ≡Al-PO3- groups and the release of -OH from WTR. A comparison of the adsorption capacities of orthophosphate and IHP on WTR suggested that binding one IHP may take two times more sites than for orthophosphate, indicating that two of the six phosphate groups in IHP were bound to WTR. This work shows that recycled WTR may be used as a low-cost adsorbent for effective removal of organic phosphate in gray water and wastewater.

[Optimization of the Nitrogen Removal Performance on the CANON Process in a Biofilm Reactor: From FBBR to MBBR].

To optimize the performance of completely autotrophic nitrogen removal over nitrite (CANON), a CANON process with modified polyethylene as carriers was operated in a moving-bed biofilm reactor (MBBR), using synthetic inorganic ammonia-rich wastewater (NH4+-N about 400 mg ·L-1) as influent at 30℃±1℃. With an HRT of 6 h, pH at 7.8, and filling rate of 35%, the average removal rate of NH4+-N and TN reached 74.28% and 87.93%, respectively, and the highest removals reached 84.68% and 98.82%, respectively, while the value of ΔNO3-/ΔTN was 0.12, which was close to the theoretical value of 0.127. This suggested that CANON sludge gradually adapted to the environment in the MBBR and began to enter the stable stage. Compared with a fixed-bed biofilm reactor (FBBR) under the same influent and operating conditions, the mean square error of MBBR and FBBR in terms of NH4+-N removal rate, TN removal rate, and TN removal load were 8.31% and 14.06%, 7.09% and 1.79%, 0.17 kg ·(m3 ·d)-1 and 0.27 kg ·(m3 ·d)-1, respectively, the former are lower than the latter. Moreover, while DO concentrations of MBBR and FBBR were 1.96 mg·L-1 and 3.09 mg ·L-1, respectively, their TN removals of per liter carriers were 0.53 kg ·(m3 ·d)-1 and 0.37 kg ·(m3 ·d)-1. Therefore, it was concluded that:① MBBR had a more stable nitrogen removal performance than did of FBBR, and ② MBBR had a higher TN removals of per liter carriers than did FBBR in addition to the higher utilization rate of oxygen.

[Impact of C/N Ratio on Nitrogen Removal Performance and N2O Release of Granular Sludge CANON Reactor].

To Explore a suitable C/N ratio for efficient nitrogen removal and simultaneously achieving N2O release reduction, ammonia-rich wastewater with sodium acetate as an organic carbon source in a granular sludge completely autotrophic nitrogen removal over nitrite (CANON) reactor under different C/N water conditions were studied to determine the reactor's nitrogen removal performance and N2O release. The results showed that the total nitrogen (TN) removal rate and the removal load tended to increase gradually with the increase of C/N, ranging from 0 to 2.0. When C/N=0, the TN removal rate was 56.50 mg·L-1 in 7 h; the highest TN removal efficiency was 49%. When C/N=2.0, the highest TN removal rate was 71.42 mg·L-1 in 7 h; the highest TN removal efficiency was 59.52%, and the contribution of CANON to nitrogen removal gradually decreased, whereas the denitrification contribution gradually increased. When △NO3--N/△TN=0.086, the contribution of CANON nitrogen removal was only 51.48% and that of denitrification was 48.52%. The N2O release volume and release ratio decreased with increasing C/N. When C/N=0, the N2O release volume and rate were the highest, namely 3.60 mg and 2.13%, respectively. The lowest N2O release volume and rate were 1.61 mg and 0.75%, respectively, when C/N=2.0.

[Optimization of the Mainstream Anaerobic Ammonia Oxidation Process and Its Changes of the Microbial Community].

The completely autotrophic ammonium removal over nitrite(CANON)biofilm reactor acclimated by high-strength ammonia wastewater was used to treat low-strength ammonia wastewater. The treatment can be divided into three stages:① the nitrogen removal efficiency of anaerobic ammonia oxidation was low during the continuous aeration stage with inorganic wastewater as raw water (0-59 d) and with an aeration amount of 30 mL·min-1 and ammonia concentration of 80 mg·L-1 (until day 56), the TN removal load was only 0.13 kg·(m3·d)-1; ② during the continuous aeration stage with domestic wastewater as raw water (60-110 d), the addition of organic carbon improved the TN removal load to 0.22 kg·(m3·d)-1 on day 79; the removal rate of NH4+-N then reached 100% when the aeration volume improved to 100 mL·min-1 on day 103; however, the TN removal efficiency and TN removal load decreased to 42.36% and 0.14 kg·(m3·d)-1, respectively. ③ To increase both the NH4+-N and TN removal efficiency during the intermittent aeration stage with domestic wastewater as raw water (110-160 d), the aeration amount was increased to 50 mL·min-1, while aeration was continued for 30 min and was stopped for the next 30 min; on day 131, the NH4+-N removal efficiency increased to 86.34%, the TN removal efficiency and removal load reached 85.87% and 0.3 kg·(m3·d)-1 respectively; on day 141, the aeration was increased to 100 mL·min-1 and the removal efficiency of NH4+-N reached 100%, while the removal efficiency and removal load of TN were 64.28% and 0.22 kg·(m3·d)-1, respectively, indicating that the intermittent aeration strategy effectively improves the nitrogen removal performance of the CANON reactor. To analyze the variation of the microbial community during different stages, the samples of three stages (0, 56, and 152 d) were analyzed using high-throughput sequencing technology. The results show that:① Candidatus Brocadia is less affected than Candidatus Kuenenia during the low-strength ammonia stages with inorganic and domestic wastewater as raw water; ② Nitrosominas and Nitrospira were the dominant bacteria of AOB(ammonia oxidizing bacteria) and NOB (nitrite oxidizing bacteria), respectively. Domestic wastewater had a greater impact on Nitrosomonas than on Nitrospira; ③ Denitrifying bacteria were present during the whole stage; Pseudomonas and Paracoccus were the most adaptable, even though their relative abundances during each stage were below 0.5%.

[Analysis of Precipitation Formation in Biofilm CANUN Reactor and its effect on Nitrogen Removal].

A CANON reactor with polymeric sponge as carrier was started by incubating sludge from another CANON reactor using synthetic inorganic ammonia-rich wastewater as raw water, and was operated at 30 degrees C +/- 1 degree C, pH 6.92-8.52. The precipitation on the surface of carriers was studied in this paper, including influence on nitrogen removal efficiency, causes for formation and composition. The results showed that: (1) the precipitation could influence the distribution of substrate to undermine the performance of CANON reactors; (2) the precipitation was calcium carbohydrate; (3) the production of precipitation may be a common result of four effects that were the regulatory effect of microorganisms on pH value, stripping effect, the role of extracellular polymers, adsorption of sponge and simultaneous chemical, biological reactions; (4) once the precipitation formed, it was difficult to recover to normal. Therefore, some measures are necessary to avoid precipitation, including: (1) raw water pretreatment to reduce the concentrations of Ca2 and Mg2. (2) ensuring short-cut nitrification stable, which could avoid increase of pH because of reduction of DO; (3) we can choose other carriers to reduce precipitation, which must ensure the optimal total nitrogen removal performance and stable short-cut nitrification.

[Effects of Hydraulic Retention Time and Dissolved Oxygen on a CANON Reactor with Haydite as Carrier].

One Completely Autotrophic Nitrogen Removal Over Nitrite ( CANON) reactor with haydite as carrier was investigated to study the effects of different hydraulic retention time ( HRT) and dissolved oxygen (DO) on CANON reactors by seeding sludge from another mature CANON reactor and using synthetic inorganic ammonia-rich waste water as influent. During the experiment, the concentration of influent ammonia nitrogen was basically unchanged, the HRT of the reactor were 9, 7, 5 h in turn and the range of DO was 1.16-3.20 mg x L(-1). The results showed that: (1) When DO was 1.20-1.75 mg x L(-1), despite the increase of DO can improve AOB's activity and matrix mass transfer in the system, NH4(+) -N and TN removal efficiency were still fell with the shortening of HRT for the CANON reactor, especially when DO was higher than 2.50 mg x L(-1), TN removal efficiency dropped sharply; (2) Under the condition that DO was 1.20-1.75 mg x L(-1), with the shortening of HRT, partial nitritation tended to be stable in the CANON process, and when DO was higher than 1.75 mg x L(-1), even if HRT was shorter, partial nitritation was still severely damaged; (3) Under the condition that DO was 1.20-1.75 mg x L(-1) and HRT was 7 h, for the CANON reactor, partial nitritation and total nitrogen removal efficiency kept well. Hydraulic retention time and dissolved oxygen both are important operational parameters for biological wastewater treatment process, which could directly affect the effect of biological treatment and effluent quality, so to choose appropriate hydraulic retention time and dissolved oxygen coordinately is very important to improve the effect of treatment of ammonium-rich wastewater by CANON process.

[Start-up by inoculation and operation of a CANON reactor with haydite as the carrier].

A CANON reactor with haydite as the carrier was started by incubating sludge from another CANON reactor and using synthetic inorganic ammonia rich wastewater as the raw water. Both start-up and operation were studied. The result showed that haydite can be a suitable carrier for CANON reactor. With this carrier, start-up of CANON reactor can be completed in 60 days with total nitrogen removal load up to 0.79 kg x (m3 x d)(-1), when the reactor was equipped with a water jacket to maintain the water temperature at 30 degrees C +/- 1 degrees C, and pH at 7.00-8.08, hydraulic retention time of 9 hours. The critical range of dissolve oxygen for CANON reactor was 1.12-1.69 mg x L(-1), and both characteristics of short-cut nitrification and ANAMMOX were stable. However, the CANON reactor can be instable if dissolve oxygen concentration increased above this range. Although the ratio of nitrate variation to total nitrogen variation (deltaNO3(-) -N/deltaTN) was 0.150-0.204, which deviated a little from its theoretical value, 0.127. The performance of CANON reactor kept relatively stable. The total nitrogen removal efficiency was up to 75.56% while total nitrogen removal load was 0.97 kg x (m3 x d)(-1), which means the temperature for CANON reactor can be decreased to 25 degrees C at least.