Total Nitrogen Removal Rate Research Articles

Enhancement of anammox bacterial activity by sodium glutamate

In this paper, the enhancement of sodium glutamate (SG) on activity of anaerobic ammonia oxidizing (anammox) bacteria was investigated by batch tests. The results illustrated that SG played an important role in enhancing anammox bacterial activity when the SG dosage ranged from 0.50 to 1.25mM, and the optimal SG concentration was 1.00mM. The performance of anammox was the best and the total nitrogen removal rate (TNRR) was 138.2mgN g-1·VSS·d-1 when the concentration of SG was 1.00mM. The results of EPS and anammox bacterial biomass measurement indicated that protein (PN), polysaccharide (PS), total EPS and the bacterial abundance reached the maximum of 1.00mM SG addition. Compared to the control tests, the EPS content and bacterial abundance increased by 38.2% and 75.8%, respectively. In addition, the cloning results showed that the community structure of anammox bacteria evolved in species level of Candidatus Brocadia genus under the condition of SG enhancement.

Co-culture of Chlorella and wastewater-borne bacteria in vinegar production wastewater: Enhancement of nutrients removal and influence of algal biomass generation

Vinegar is an important seasoning and its annual output continues to increase in China. Vinegar production is accompanied by a large amount of wastewater which contains many nutrients, including acetic acid, nitrogen and phosphorus. In this study nutrients removal during the co-culture of Chlorella and wastewater-borne bacteria (Bacillus firmus and Beijerinckia fluminensis), as well as Chlorella biomass accumulation, pigment and lipid production in vinegar production wastewater were investigated. The removal rates for chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were significantly improved after the addition of the bacteria. At the end of the cultivation, the highest COD, TN and TP removal rates were improved by 22.1%, 20.0%, and 18.1%, respectively, compared with the control group without adding bacteria. The mean growth rates of the algae in most goups decreased slightly during the co-culture with the bacteria. The wastewater-borne bacteria Beijerinckia fluminensis effectively enhanced the pigment content of Chlorella sp. The chlorophyll a, b, and carotenoids concentrations were increased by >35.7%, 20.9% and 11.2%, respectively. This study demonstrated an efficient microalgae and wastewater-borne bacteria co-culture system that can be potentially used for vinegar production wastewater treatment and also the recovery of high-value byproducts of algal pigment may offset the decrease in algal biomass.

Intensified nutrients removal in a modified sequencing batch reactor at low temperature: Metagenomic approach reveals the microbial community structure and mechanisms.

To achieve efficient biological nutrients removal at low temperature, a modified sequencing batch reactor (SBR) was developed at 10°C by extending sludge retention time (SRT), shortening aerobic stage and compensating anoxic stage. The average removal rates of ammonium (NH4+-N), total nitrogen (TN) and total phosphorus (TP) were 98.82%, 94.12% and 96.04%, respectively. Variation of carbon source in a typical cycle demonstrated the maximum synthesis of poly-β-hydroxybutyrate (PHB) (60mg/L) occurred after feast period. Furthermore, the TP in sludge reached 50.4mg/g mixed liquor suspended solids (MLSS) (78.4% was inorganic phosphorus and 21.6% was organic phosphorus) after 120 days of operation, indicating an excellent P-accumulating capacity was achieved in this system. Ammonia oxidizing bacteria (AOB) activity inhibition test verified both AOB and ammonia oxidizing archaea (AOA) were involved in ammonia-oxidizing process and the latter accounted for 17%-19%. Metagenomic-based taxonomy revealed the dominant genera were Candidatus Accumulibacter (12.18%), Dechloromonas (7.54%), Haliangium (6.69%) and Candidatus Contendobacter (3.40%). As described from the denitrifying genes perspective, with the exception of nitrite reduction (performed by denitrifiers), denitrifying phosphorus-accumulating organisms (DPAOs) played a leading role in denitrification pathway, showing that poly-β-hydroxyalkanoates (PHA)-driven nutrients removal was the dominate process.

Improving denitrification in an aquaculture wetland using fish waste - a case study

Cost-efficient, end-of-pipe, nitrate removal techniques are called for by the commercial aquaculture industry. This case study examined how simple flow manipulations improved the denitrification performance of a 19,007 m2 (13,305 m3) constructed, free water surface (FWS) wetland treating aquaculture effluent. The wetland consisted of two separate streams with a common outlet: one stream treating nitrate-rich but carbon deficient effluent from the production unit at a hydraulic retention time (HRT) of 1.5 days (wetland stream 1); and a second stream treating carbon-rich, fish sludge-based effluent at a HRT of 41.0 days (wetland stream 2). During the course of the study (May–July 2017), three increasing proportions (40, 49 and 56%) of nitrate-rich effluent were re-directed from wetland stream 1 to the sludge-fed wetland stream 2 aiming at improving heterotrophic denitrification conditions in wetland stream 2 and consequently nitrogen removal in the wetland as a whole. Inlet C/N ratio in wetland stream 2 decreased from 1086 ± 57 to an average of 234 ± 56 (p < .05), and the area-based, total nitrogen (TN) removal rate in this wetland section increased significantly from 0.1 ± 0.01 to 8.4 ± 1.4 g/m2/d at the highest manipulated flow. In comparison, the flow manipulations had no effect on TN removal rates in wetland stream 1 averaging 1.4 ± 0.2 g/m2/d throughout the study. For the wetland as a whole, the TN removal rate increased from 1.4 ± 0.2 to 3.9 ± 0.8 g TN/m2/d. The flow manipulations furthermore improved the removal rates of total phosphorous and dissolved organic matter in the wetland as a whole. The study demonstrates that denitrification in a constructed aquaculture wetland may be improved by combining sludge-based and nitrogen-rich effluents in right proportions and leading it through an anoxic section of the wetland.

Effects of biomass and environmental factors on nitrogen removal performance and community structure of an anammox immobilized filler

In order to reduce the loss of anaerobic ammonia oxidation (anammox) sludge and stabilize the reaction microenvironment, polyvinyl alcohol - polypropylene (PVA-PP) was used to encapsulate anammox bacteria on a filler. The influence of different inoculation amounts (2, 4, 6 and 8%) on the overall nitrogen removal process was first compared and then the anammox characteristics of the immobilized filler under the influence of different environmental factors were evaluated through batch experiments. The results show that the biomass only affected the growth rate of the activity during the logarithmic phase, while the total nitrogen removal rate (NRR) tended to be similar after 99 d of culture. The NRR reached 1.83 kg·(m3·d)-1 on day 140, which was 9.4 times that of suspended sludge before encapsulation, and the structure of embedding filler was complete without shedding. Scanning electron microscopy (SEM) showed that the internal porous network structure formed channels and a large number of anammox bacteria were observed around. Microbial community analysis of the 16S rDNA gene showed that the diversity was maintained in the entrapped carrier. Furthermore, the effective enrichment of the anammox functional bacteria Candidatus Kuenenia (AF375995.1) increarsed from 11.06% to 32.55%. The PVA-PP immobilized filler fit well with the biological nitrogen removal kinetic model and could also achieve coupling of anammox and denitrification. The inhibition effect of the organic carbon source interference and starvation on anammox bacteria was significantly weakened.

Correlations of nitrogen removal and core functional genera in full-scale wastewater treatment plants: Influences of different treatment processes and influent characteristics

The denitrification process is crucial for biological nitrogen removal in wastewater treatment plants (WWTPs). In this study, the nitrogen removal efficiency in full-scale WWTPs with different treatment processes and influent characteristics was investigated. The results indicated that the average total nitrogen removal rate (NRR) and denitrification rate in the A/O or A2/O systems were 67.5% and 2.08 mg N h−1 gMLVSS−1, respectively. However, cyclic activated sludge systems (CASSs) showed more efficient nitrogen removal with an average NRR and denitrification rate of 79.6% and 9.89 mg N h−1 gMLVSS−1, respectively. The microbial communities in WWTPs with similar influent compositions were similar and mainly shaped by BOD5. Candidatus Competibacter, Caldilineaceae and Anaerolineaceae were the functional genera closely associated with nitrogen removal based on high-throughput sequencing and correlation analysis. This study provides new insights into the regulation and amelioration of full-scale WWTPs to meet the increasingly stringent nitrogen discharge standard.

The effect of different denitrification and partial nitrification-Anammox coupling forms on nitrogen removal from mature landfill leachate at the pilot-scale

The effects on nitrogen removal from landfill leachate were compared between the denitrification (DN) direct coupling in Partial nitrification (PN)-Anammox (DN+(PN-Anammox)) and pre-DN followed by PN-Anammox (DN-PN-Anammox). Both processes can achieve coupling and high nitrogen removal. However, the DN+(PN-Anammox) process was not conducive to the treatment of high-COD wastewater. The total nitrogen removal rate (TNRR) and total nitrogen removal efficiency (TNRE) were stable at 0.31 kg/(m3·d) and 76.3%. When UASB was added to denitrification and transform the process into DN-PN-Anammox, the influent NH4+-N and COD concentrations were increased to 2230 and 2612 mg/L, TNRR and TNRE reached 0.45 kg/(m3·d) and 96.7%, respectively. The DN-PN-Anammox process not only was able to make full use of degradable COD in wastewater to realize the NO3−-N removal, but also benefited the growth of autotrophic bacteria. The DN-PN-Anammox reduced the oxygen supply and was more conducive to the treatment of highly-concentrated mature landfill leachate.

Evaluation of filamentous heterocystous cyanobacteria for integrated pig-farm biogas slurry treatment and bioenergy production

The study evaluates 36 filamentous heterocystous cyanobacteria for the treatment of biogas slurry from pig farm and the accumulation of biomass for bioenergy production. The results showed that only the strains B, J, and L were able to adapt to a 10% biogas slurry. The removal rates of ammonia nitrogen, total nitrogen, and total phosphorus for strains J and L were 92.46%–97.97%, 73.79%–79.90%, and 97.14%–98.46%, respectively, higher than that of strain B. Strain J had the highest biomass productivity and lipid productivity. Based on the biodiesel prediction results, it was concluded that strains J and L are more suitable for biodiesel production. The estimation of theoretical methane potential suggests that the algal biomass of strain J also have the desirable possibility of biogas generation. In summary, algal strain J (Nostoc sp.) offers great potential for biogas slurry treatment and for the production of bioenergy.

Screening and Diversity Analysis of Aerobic Denitrifying Phosphate Accumulating Bacteria Cultivated from A2O Activated Sludge

The aerobic denitrifying phosphate accumulating bacteria (ADPB) use NO3− as an electron acceptor and remove nitrate by denitrification and concomitant uptake of excessive phosphorus in aerobic conditions. Activated sludge was collected from the A2O aerobic biological pool of the sewage treatment plant at Hezuo Town, Chengdu City. The candidate ADPB strains were obtained by cultivation in the enriched denitrification media, followed by repeated isolation and purification on bromothymol blue (BTB) solid plates. The obtained candidates were further screened for ADPB strains by phosphorus uptake experiment, nitrate reduction test, metachromatic granules staining, and poly-β-hydroxybutyrate (PHB) staining. The 16 sedimentation ribosome deoxyribonucleic acid (16 S rDNA) molecular technique was used to determine their taxonomy. Further, the denitrification and dephosphorization capacities of ADPB strains were ascertained through their growth characteristics in nitrogen-phosphorus-rich liquid media. The results revealed a total of 25 ADPB strains screened from the activated sludge of the A2O aerobic biological pool of the sewage treatment plant at Hezuo Town. These strains belonged to two classes, four orders, and five genera. Among them, the strain SW18NP2 was a potentially new species in the Acinetobacter genus, while the strain SW18NP24 was a potential new species in the Pseudomonas genus at the time of their characterization. The Acinetobacter was the dominant genus. The obtained ADPB strains demonstrated a rich diversity. The ADPB strains had significant variations in denitrification and dephosphorization capacities. Twenty-three strains exhibited a total phosphorus removal rate of above 50%, and 19 strains exhibited a total nitrogen removal rate of above 50%. The strain SW18NP2 showed the best denitrifying phosphorus removal (DPR) capacity, with a dephosphorization rate of 82.32% and a denitrification rate of 73.73%. The ADPB in the A2O aerobic biological pool of the sewage treatment plant at Hezuo Town demonstrated a rich diversity and a strong DPR capacity.

Start-up of the Simultaneous Nitrification, Anammox, and Denitrification (SNAD) Reactor and Efficacy of a Small Amount of Organic Carbon

In perspective of the issue of how to begin simultaneous nitrification, anammox, and denitrification (SNAD) rapidly, the sequencing batch biofilm reactor (SBBR) was adopted to enrich ammonia-oxidizing bacteria (AOB) and anammox bacteria (AnAOB) rapidly and to inhibit nitrite-oxidizing bacteria (NOB) after three phases (67 days) of culture, and the impacts of different low carbon-nitrogen ratios (COD/N) on denitrification performance of the process were investigated. The results showed that preventing the accumulation of nitrite (NO2−-N) was the key to start SNAD successfully. The removal efficiencies of ammonia nitrogen (NH4+-N) and total nitrogen (TN) in the system can reach more than 99% and 90%, respectively. Corresponding to COD/N = 0, 1 and 2, removal efficiencies of NH4+-N were 99.6%, 99.5%, and 98.5% respectively and removal efficiencies of TN were 93.8%, 97.2%, and 98.1%, respectively; the total nitrogen removal rate (TNRR) was greater than 0.29 kg N m−3 day−1. It indicates that the presence of a small amount of COD is beneficial to the denitrification of NO3−-N without affecting the effect of simultaneous nitrification and anaerobic ammonium oxidation, which further improves the efficiency of nitrogen removal. High-throughput sequencing analysis showed that the ratios of AOB, AnAOB, and denitrifying bacteria were 7.3%, 20.1%, and 7.66%, respectively. Candidatus Kuenenia was the only genus of the SNAD reactor with anaerobic ammonium oxidation. AOB, Anammox, and heterotrophic denitrifying bacteria were present in the system, while ammonia oxidation and anaerobic ammonium oxidation played a dominant role in the denitrification process.

Start-up of a Three-stage PN/A Granular Sludge Reactor for Treating Wastewater with High Concentrations of Ammonia

In order to apply partial nitritation-ANAMMOX (PN/A) technology to treat wastewater with high concentrations of ammonia, autotrophic nitrogen-removing granular sludge was crushed and inoculated into a three-stage continuous flow reactor. The nitrogen loading rate (NLR), dissolved oxygen (DO) concentration, and free ammonia (FA) levels in each compartment of the reactor were controlled over a 106-day period. Results showed that the nitritation process occurred with the inoculated granules during the initial phase. A limited aeration strategy was employed in the reactor at relatively high NLRs. Given the effective suppression of nitrite-oxidizing bacteria and the prevention of ANAMMOX bacteria from high DO conditions, the compact structure and nitrogen-removal activity of the granules could be improved. When the ammonia-nitrogen concentration was increased in the influent to 350 mg·L-1, the adverse impacts of high FA concentrations on the functional microbe activity in the first compartment should be eliminated. This occurs by reducing the influent pH and alkalinity dosage. This occurs by reducing the influent pH and degree of alkalinity. As a result, a total nitrogen removal rate of 7.2 kg·(m3·d)-1 was achieved in the reactor, which is 50 to 100 times higher than that of conventional activated sludge systems. The consistent improvement in the nitrogen-removal activity of the granules was demonstrated by batch testing at different aeration intensities. This showed that activity was greatest in the first compartment, which showed the highest granular maturity. In addition, a clear linear correlation (R2>0.97) was observed between the amount of extracellular polymeric substance and the specific nitrogen removal rate. This indicated that the dense granules played a positive role in enhancing the performance of the reactor.

Correlation analysis of sewage removal rate and microbial quantity in plateau environment

Based on A2O process in plateau environment, the correlation between the removal rate of chemical oxygen demand (COD), the total phosphorous (TP), total nitrogen (TN) and ammoniacal nitrogen (NH4+-N) in anaerobic tank, anoxic tank and aerobic tank and the quantity of indicator microorganisms was analyzed with temperature, dissolved oxygen (DO) and the hydraulic retention time (HRT) as working conditions, and the curve regression model of water removal rule and the optimal working conditions were obtained through SPSS analysis. The results showed that the removal rates of COD, TN, TP and NH4+-N were positively and negatively correlated with some indicator microorganisms. The three sets of curve regression models passed the significance test. The DO and COD were cubic models, HRT and COD were quadratic models, HRT and NH4+-N were S curve models. When DO is 2∼3 mg/L, the removal rate of COD can reach 87%. When HRT is 30∼40 h, the removal rate of COD can reach more than 90%, and the removal rate of NH4+-N can reach more than 50%.

A novel synergistic denitrification mechanism during supercritical water oxidation

Nitrogen transformation processes have an important impact on human life. In this work, the synergistic denitrification mechanism in the process of supercritical water oxidation (SCWO) was studied. N-containing organic compounds had better denitrification effects than the inorganics because they could produce more active radicals. Nitroaniline had higher total nitrogen (TN) removal rates than those of compounds containing only amino or nitro group due to the intramolecular synergistic denitrification. Meanwhile, intermolecular synergistic denitrification was found between nitro and amino/N-heterocyclic compounds, but its denitrification efficiency was not as good as intramolecular synergistic denitrification. The reaction mechanism of synergistic denitrification was proposed, which was similar to anaerobic ammonia oxidation. In addition, the overall equilibrium process of intermolecular synergistic denitrification was established. It included the rapid reduction of org-N at the early stage of SCWO process, as well as the limiting step of slow denitrification rate of NH4+ and NO3− in the late stage. The relationship between TN removal rate of mixture (kMIX-TN) and monomer compound (kNO2-TN or kNH2-TN) could be expressed by an equation, that was kMIX-TN = 3.3698 kNO2-TN·kNH2-TN + 0.0901, with R2 of 0.7788, which demonstrated that kMIX-TN was linearly related to kNO2-TN·kNH2-TN. All these works provided theoretical basis for nitrogen removal in water by SCWO technology.

Effects of cultivation strategies on the cultivation of Chlorella sp. HQ in photoreactors

The effects of cultivation strategies (including autotrophic cultivation (AC), heterotrophic cultivation (HC), fed-batch cultivation (FC), heterotrophic + autotrophic two-stage cultivation (HATC), and heterotrophic + mixotrophic two-stage cultivation (HMTC)) on the growth and lipid accumulation of Chlorella sp. HQ and its total nitrogen (TN) and total phosphorus (TP) removal in secondary effluent were investigated in column photoreactors. The results showed that the TN and TP removal rates ranged between 93.72%–95.82% and 92.73%–100%, respectively, under the five different strategies. The microalgal growth potential evaluated by the maximal growth rate (Rmax) was in the order of HMTC>HC>FC>AC>HATC. The values of biomass, total lipid yield, triacylglycerols (TAGs) yield, and total lipid content of the microalga cultivated in the last 5 d increased significantly, but the TAGs productivities of the five strategies were lower than those in the first 7 d. Compared with all the other cultivation strategies, the TAGs productivity and yield after 12 d of cultivation under the heterotrophic condition reached the highest values accompanying the highest level of intracellular reactive oxygen species (ROS), in which the TAGs yield reached 40.81 mg/L at the end of the cultivation period. The peaks in TAGs yield and ROS level suggested that HC was beneficial for lipids accumulation via regulating the cellular redox status and exerting ROS stress on microalgal cells. In summary, HMTC was the best cultivation strategy for improving the microalgal biomass and HC was the best strategy for microalgal TAGs accumulation to produce biodiesel.

Simultaneous nitrification and denitrification in the bio-cathode of a multi-anode microbial fuel cell

ABSTRACT A multi-anode microbial fuel cell (MA-MFC) was developed to investigate simultaneous nitrification and denitrification (SND) in the bio-cathode. As the chemical oxygen demand to nitrogen (COD/N) ratio of the cathode was increased from 0 to 4.5, the electricity-producing quantity ranged between 498 and 543 C and the attained total nitrogen (TN) removal rate reached 12.07 g TN·m−3·d−1, resulting in a TN removal efficiency of 78.8% under the target COD/N ratio of 3.5. The removal of pollutants in series and parallel, open-circuit and closed-circuit were compared, respectively. The removal rates of TN, , and cathode and anode COD were all higher in the parallel connection configuration than in the series configuration. In parallel connection, the TN removal rate reached 14.4 g TN·m−3·d−1, which was 1.9 times that in series connection. Compared with the open-circuit system, the removal rate of TN in the closed-circuit system was improved by 17.8%, which could be ascribed to electrochemical denitrification. The results of high-throughput sequencing confirmed and clarified the presence of autotrophic denitrification and heterotrophic denitrification, including aerobic denitrification, when the MA-MFC had been operated for 18 months.

Overlooked pathways of denitrification in a sulfur-based denitrification system with organic supplementation

Elemental sulfur-driven autotrophic denitrification (SADN) is a cost-effective approach for treating secondary effluent from wastewater treatment plants (WWTPs). Additional organics are generally supplemented to promote total nitrogen (TN) removal, reduce nitrite accumulation and sulfate production, and balance the pH decrease induced by SADN. However, understanding of the impacts of organic supplementation on microbial communities, nitrogen metabolism, denitrifier activity, and SADN rates in sulfur-based denitrification reactors is still limited. Here, a sulfur-based denitrification reactor was continuously operated for 272 days during which six different C/N ratios were tested successively (2.7, 1.5, 0.7, 0.5, 0.25, and 0). Organic supplementation improved TN removal and decreased NO2− accumulation, but reduced the relative abundance of denitrifiers and the contribution of autotrophic nitrate-reducing bacteria (aNRB) to TN removal during the long-term operation of reactor. Predictive functional profiling showed that nitrogen metabolism potential increased with decreasing C/N ratios. SADN was the predominant removal process when the C/N ratio was ≤0.7 (achieving 60% contribution when C/N = 0.7). Although organic supplementation weakened the dominant role of aNRB in denitrification, batch tests for the first time demonstrated that it could accelerate the SADN rate, attributed to the improvement of sulfur bioavailability, likely via the formation of polysulfide. A possible nitrogen removal pathway with multiple electron donors (i.e., sulfur, organics, sulfide, and polysulfide) in a sulfur-based denitrification reactor with organic supplementation was therefore proposed. However, supplementation with a high level of organics could increase the operational cost and effluent concentrations of sulfide and organics as well as enrich heterotrophic denitrifiers. Moreover, microbial community had substantial changes at C/N ratios of >0.5. Accordingly, an optimal C/N ratio of 0.25–0.5 was suggested, which could simultaneously minimize the additional operating cost associated with organic supplementation and maximize TN removal and SADN rates.

Feasibility and safety of papermaking wastewater in using as ecological water supplement after advanced treatment by fluidized-bed Fenton coupled with large-scale constructed wetland

Reuse of pulp-and-paper industry wastewater as reclaimed water is an effective way to mitigate water resource shortage. In this study, the feasibility and safety of papermaking wastewater for the use as ecological water supplement after the treatment by fluidized-bed Fenton (FBF) coupled with constructed wetland (CW), were investigated from laboratory-scale to large-scale field. The optimum pH, H2O2, H2O2/Fe2+ ratio and hydraulic retention time (HRT) of FBF were 3.5, 0.93 mL/L, 4 and 60 min, respectively, based on reduction of both total organic carbon (TOC) and genotoxicity. Furthermore, the safety of effluent was evaluated using SOS/umu assay and 8-hydroxy-2-deoxyguanosine (8-OHdG) in zebrafish. Results showed FBF followed by CW improved the conventional water quality indicators and reduced the toxicity. Average removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN), total phosphorus (TP) and colority were 87.3%, 93.59%, 51.73%, 84.75% and 95.86%, respectively. The equivalent concentration of 4-nitroquinoline 1-oxide (4-NQO-EQ) decreased from 30.6 ± 1.6 μg/L in influent to 12.4 ± 1.0 μg/L after treated by FBF, then decreased to 5.9 ± 0.4 μg/L after treated by CW and to 3.2 ± 0.3 μg/L after 12-km downstream self-purification. The chronic survival rates of 21-d zebrafish significantly increased from 0.0% in influent to 58.8 ± 4.0% in effluent of CW and gradually increased to 68.8 ± 2.6% after 12-km downstream self-purification. Similarly, 8-OHdG level in zebrafish decreased from 120.0 ± 19.3 ng/L in effluent of ecological oxidation pond to 94.0 ± 7.5 ng/L in effluent of CW and gradually decreased to 42.0 ± 3.0 ng/L after 12-km downstream self-purification. The study concluded that FBF-CW is an efficient detoxication and water quality improvement technology for papermaking wastewater to be used as an ecological water supplement.

Efficient denitrification and removal of natural organic matter, emerging pollutants simultaneously for RO concentrate based on photoelectrocatalytic radical reaction

Reverse osmosis (RO) concentrate becomes a new knotty problem in water treatment for its high concentrated salts and complex pollutants. In this study, we presented a photoelectrocatalytic (PEC) chloride-radical (Cl) system to efficiently remove its pollutants including total nitrogen, natural organic matter and emerging pollutants simultaneously in taking advantage of pre-existing chloride and sulfate salts as electrolytes. NH4+-N, humic acid and emerging pollutants of nitrosodiethylamine and bisphenol A were used as model pollutants. A WO3|[Pd- Cu/NF] electrode couples were used in the PEC system. HO and Cl radicals were generated on the surface of WO3 photoanode. Organics including humic acid and emerging pollutants were degraded by HO, and NH4+-N was efficiently oxidized to N2 with the selective reaction of Cl and NH4+. NO3−-N overoxidized from NH4+-N was selectively reduced to N2 on [Pd-Cu/NF] cathode. The results showed that the total nitrogen (TN) and total organic carbon (TOC) removal rate were 99.90% and 50.95% in 180 min for the model RO concentrate with 28 mg/L NH4+-N and 20 mg/L humic acid. The emerging pollutants including nitrosodiethylamine and bisphenol A performed removal rates of almost 100%. This study offers a novel, efficient and eco-friendly PEC system for deep purification of RO concentrate.

Rapid Cultivation of Anaerobic Ammonium Oxidation Granular Sludge and Inhibition Kinetics of Granular Sludge

For the rapid cultivation of anaerobic ammonium oxidation (ANAMMOX) granular sludge (AGS), a small amount of flocculent ANAMMOX sludge (FAS) was taken as the research object, and a bio-flow separate ball was used as the filler in an up-flow anaerobic sludge bed (UASB) to rapidly begin ANAMMOX and to cultivate granular sludge. In addition, the substrate inhibition kinetic characteristics of the AGS were investigated by using the Haldane model. The results showed that start-up of the ANAMMOX was successfully achieved. The total nitrogen removal rate was more than 85%, and the volume load of total nitrogen was 0.72 kg·(m3·d)-1. AGS with diameters of 1.0-3.0 mm were cultured within 127 days using the Bio-flow Separate Ball. The kinetic studies showed that the maximum reaction rates for ammonia and nitrite of granular sludge were 1.46 kg·(kg·d)-1 and 1.76 kg·(kg·d)-1, with half inhibition constants of ammonia and nitrite at 852.2 mmol·L-1 and 108.2 mmol·L-1, respectively. Compared with FAS, AGS can withstand higher concentrations of ammonia and nitrite and can maintain a higher reaction rate. The placement of the filler has positive significance for starting ANAMMOX and rapidly culturing AGS.

Setup and Microbial Community Analysis of ANAMMOX System for Landfill Leachate Treatment Coupling Partial Nitrification-Denitrification Process

In order to upgrade the current shortcut nitrification and denitrification process for landfill leachate treatment and to stimulate nitrification-denitrification coupled with anaerobic ammonia oxidation (ANAMMOX) at a landfill, an ANAMMOX process was started using an up-flow anaerobic sludge bed (UASB) reactor seeded with nitrification and denitrification sludge. The performances of the reactor were investigated, including the nitrogen loading and nitrogen removal rates. Moreover, Illumina Miseq sequencing was conducted to analyze the microbial community dynamics under long-term operation on a molecular level. The results showed that the ANAMMOX reactor was successfully started in 149 days. The total nitrogen loading rate reached 4000.00 mg·(L·d)-1, and the total nitrogen removal rate reached 3885.76 mg·(L·d)-1 after stable operation. The average ammonium and nitrite removal efficiencies were more than 95%. In 250 days, the Planctomycetes in the reactor experienced rapid growth, and its abundance reached 54.94%. The abundance of Candidatus Kuenenia reached 49.66%. The upgrading process of landfill leachate treatment by coupling ANAMMOX based on short-cut nitrification and denitrification was confirmed to be feasible.