Adaptation of the anammox process for high ammonium photovoltaic wastewater treatment.

Tunnel Oxide Passivating Contacts (TOPcon) battery in the photovoltaic industry generates high ammonium wastewater during the production process, the adaptability of using the anaerobic ammonia oxidation (Anammox) process for photovoltaic wastewater (PVW) treatment is a research hotspot. Based on the analysis of photovoltaic wastewater quality, the effectiveness of nitrogen removal, sludge characteristics and microbial communities were examined. The results showed that when the influent NH4+-N concentration of PVW was lower than 150 mg·L-1, the nitrogen removal efficiency (NRE) was almost 100 %. In addition, the NRE decreased from 74 % sharply to 20 % when the NH4+-N concentration was increased from 175 mg·L-1 to 200 mg·L-1. The extracellular polymeric substances (EPS) content increased with elevated ammonium concentration in the influent, indicating that microorganisms secreted more EPS to resist elevated nitrogen loading. The main functional populations were Candidatus Kuenenia (0-24 %). The influent ammonium concentration is recommended to be < 200 mg·L-1.

Synergetic association of hydroxyapatite-mediated biofilm and suspended sludge enhances resilience of partial nitrification/anammox (PN/A) system treating high-strength anaerobic membrane bioreactor (AnMBR) permeate.

A single-stage partial nitrification/anammox (PN/A) system with biocarriers was used to treat the permeate from an anaerobic membrane reactor (AnMBR) processing organic fraction of municipal solid wastes. The suitable Ca/P ratio and high pH in the AnMBR permeate facilitated hydroxyapatite (HAP) formation, enhancing the biofilm attachment and the settleability of suspended sludge. This maintained sufficient biomass and a stable microbial structure after flushing to mitigate the free nitrous acid inhibition. Robust anammox bacteria in the biofilm and ammonia-oxidizing bacteria in the suspended sludge ensured that the PN/A system achieved an 87.3 % nitrogen removal efficiency at an influent NH4+-N concentration of 1802 mg/L. This study demonstrates that AnMBR permeate with high Ca, P and NH4+-N content is suitable for single-stage PN/A system with biocarriers due to the high resilience enhanced by HAP, offering a reference for the treatment of high-strength AnMBR permeate.

The stable operation of nitritation process with the continuous granular sludge-type reactor and microbial community analysis.

The nitritation step is the fundament for the biological nitrogen removal regardless of the traditional nitrification and denitrification process, the nitrite shunt process or the anammox process. Thus, exploring the effective nitritation performance is an important aspect of biological nitrogen removal. This study explored the upper limit of nitritation rate by increasing hydraulic residence time with the well-mixed and continuous granular sludge-type reactor characterized with low complexity and easy operation. The results showed that with the nitrogen loading rate of 1.0 kg/m3/d, the nitrite production rate could reach up to 0.65 kg/m3/d with the nitrite production efficiency of 63.49%, which is remarkable compared to that in the previously similar research. The microbial analysis indicated that ammonia-oxidizing bacteria was successfully enriched (13.27%) and genus Nitrosomonas was the dominant bacteria type. Besides, the activity of ammonium oxidizing bacteria in the continuous flow reactor was higher than that of other reactor types. The growth of vorticella on the sludge was also found in the reactor. The test of specific sludge activity and the microbe analysis both indicated that the nitrite-oxidizing bacteria was well inhibited during the whole experiment, which indicated the strategy of simply adjusting the dissolved oxygen is effective for running of nitritation process. The phosphorus removal performance was also achieved with a removal efficiency of 23.53%. The functional composition of the microbial community in the samples was predicted and finally transformation mechanism of nitrogen in sludge was drawn. In sum, this study indicated the superior performance of the granule sludge-type nitritation process and give a reference for the application of biological nitrogen removal technology.

Biogeochemical and physical controls on ammonium accumulation on the Chukchi shelf, western Arctic Ocean.

Spatial variability of ammonium concentrations along repeat transects were examined on the Chukchi shelf during 2012-2018. Two distinct near-bottom high ammonium pools (>1 µmol/kg) near 67.5°N and 72.5°N of the transects were identified in all years. The accumulation of ammonium in the regions is driven primarily by a combination of biogeochemical processes (e.g., dynamic bacterial remineralization of organic matter) and physical controls (e.g., strong density-contrast barrier limits upward mixing of ammonium). The ammonium pool on the shelf may became larger in the expectation of the stronger bacterial remineralization following elevate primary production, and may have potential impact on the structure and productivity of ecosystem on the Chukchi shelf.

Wastewater management in Motor Rest Area - A review article.

Due to the constantly developing road network, a large number of new Motor Rest Area facilities are being built. The aim of the work is a critical assessment of the current wastewater management in the MRA and the proposal of appropriate solutions capable of purifying wastewater. The analysis of the current state of the MRA facilities was carried out on the basis of maps, own observations and an assessment of interest in the subject recently by reviewing publication resources. For this purpose, analyzes of the frequency of occurrence of keywords describing the issue were used. The solutions used so far are ineffective. This is mainly due to the perception of wastewater produced in MRA facilities as domestic wastewater. This assumption leads to the selection of inappropriate solutions, which in the long run can lead to an ecological disaster by introducing untreated sewage into the environment. The authors point to the possibility of introducing a circular economy in these places to relieve their environmental impact. Since, wastewater generated in MRA facilities, due to its specificity, is very difficult to treat. They are characterized by uneven inflow, a lack of organic matter, a low C:N ratio and very high concentration of ammonium nitrogen. Conventional activated sludge methods cannot cope with this. The need for changes and the use of solutions suitable for the treatment of wastewater with a high content of ammonium nitrogen has been demonstrated. The authors presented solutions that have the potential to be used in MRA facilities. The application of the proposed solutions from that moment will undoubtedly change the impact of MRA facilities on the environment and solve the problem of wastewater management on a large scale. There is still a lack of research on this thematic scope, which is a challenge authors have taken up.

Nitrogen burial characteristics of Quaternary sediments and its controls on high ammonium groundwater in the Central Yangtze River Basin.

As the strata sedimentary process proceeds, considerable amounts of nitrogen (N) is buried in sediments, which controls the sources and fate of N in the "groundwater-sediment" system. However, there is little concern regarding N burial characteristics in continuous sediment profiles from surface layer to deep aquifer thus far. In this study, lithology, grain size, geochronology, exchangeable N contents and geochemical proxies of sediments were analyzed to reveal the controlling mechanisms of N burial characteristics in Quaternary sediments and to interpret the enrichment of N in groundwater of central Yangtze River Basin. The results demonstrated a similar distribution trend for buried N in two sedimentary cores, which were high in the surface layer and decreased to stable in the deep aquifer. Excessive exchangeable N (EX-N) contents in sediments were mainly attributed to geologic origin. The N burial characteristics were controlled by the evolution of depositional environment: sedimentary facies determined the concentrations of total organic nitrogen (TON), further affecting the mineralization capacity of sediments; while paleoclimate regulated the intensity of the N transformation processes, ultimately influencing the actual concentrations of EX-N in sediments. In addition, due to the fast accumulation of alluvial deposits after Last Glacial Maximum and rapid development of Jianghan Lake Groups during Holocene, abundant organic matter (with high TON contents) was buried in sediments, which were still able to produce more ammonium or nitrate, and further posing continuous threats to groundwater quality. This study provided a new interpretation for the formation of high-ammonium aquifer in terms of depositional evolution.

Food waste hydrolysate as a carbon source to improve nitrogen removal performance of high ammonium and high salt wastewater in a sequencing batch reactor.

The high ammonium and high salt (HAHS) wastewater generated from the anaerobic digestate of food waste is usually difficult to be treated by biological process because of its low C/N ratio. Herein, food waste hydrolysate (FWH) is rich in readily biodegradable organic matter, was utilized as carbon source to enhance the nitrogen removal of HAHS in the activated-sludge system. Results showed that compared with the control average total nitrogen removal efficiency increased from 73.4% to 94.9% and effluent declined from 281.4 mg/L to 53.9 mg/L by adding FWH at the C/N ratio of 6, satisfying the sewage discharge standard regulated by China. Besides, FWH utilization led to higher selectivity of the species responsible for nitrogen removal in related to glucose-adding group, which were dominated by Flavobacteriaceae, Melioribacteraceae, PHOS-HE36, and Rhodobacteraceae after a long-term operation. In general, FWH is an alternative carbon source to enhance nitrogen removal in HAHS wastewater treatment.

Nitrogen removal performance of high ammonium and high salt wastewater by adding carbon source from food waste fermentation with different acidogenic metabolic pathways.

Food waste fermentation liquid components, mainly lactate and volatile fatty acids (VFAs), can be used as alternative carbon sources to improve the nitrogen removal efficiency. To investigate the effects of carbon sources generated from food waste (FW) fermentation liquid on nitrogen removal for the treatment of high ammonium and high salt wastewater (HAHS), the lactate, acetate, propionate, butyrate, and their mixtures were added in activated sludge systems operating over 130-days. Lactate and butyrate inhibited nitrifiers by enriching polyphosphate accumulating organisms (PAOs), thus deteriorated nitrogen removal after a long-term period. When fed with acetate or propionate, the dominant glycogen accumulating organisms (GAOs) groups simultaneously realized nitrification and denitrification. The mixed carbon source enhanced microbial community robustness and the transformation of Polyhydroxyalkanoate (PHA), advancing nitrogen removal efficiency. Mixed carbon source of acetate-propionate was preferred, in which the coexisting groups of GAOs and PAOs enhanced the denitrification rate of denitrifiers and kept balancing with nitrifiers, where the highest denitrification rate (DNR) was 1.05 mg N/(h·g VSS) and the average TN removal efficiency was above 98% under the maximum nitrogen load of 0.48 kg N/(kg VSS·d). In addition, the primary pathways of nitrogen removal were heterotrophic nitrification and denitrification, since the autotrophic nitrifiers were inhibited by the free ammonium and salinity. This study illustrated the differences of nitrogen removal performance and mechanisms with fermentation liquid components as carbon sources processing of HAHS wastewater.

Performance and nitrogen removal mechanism in a novel aerobic-microaerobic combined process treating manure-free piggery wastewater.

A novel combined sequencing batch reactor (SBR) - up-flow microaerobic sludge reactor (UMSR) process was developed to treat manure-free piggery wastewater characterized by low COD/TN ratio and high NH4+-N. The front-end SBR was designed to get an effluent with COD/TN ≤ 1 by removing COD, allowing the back-end UMSR to practice anammox for the simultaneous removal of TN and NH4+-N. Fed with the raw piggery wastewater, the combined SBR-UMSR process was started up at 27℃ with a reflux ratio of 15:1 in the UMSR. After 230-days running, the removal of COD, TN, and NH4+-N in the combined SBR-UMSR process reached 78.41%,85.05%, and 92.21%, respectively. 50.22% of COD in the wastewater was removed in the SBR, while 87.11% of NH4+-N and 79.69% of TN were removed in the UMSR. Stoichiometry and bacterial function analysis revealed that the partial nitrification - anammox process was the dominant nitrogen removal approach in the UMSR.

Sulfidation forwarding high-strength Anammox process using nitrate as electron acceptor via thiosulfate-driven nitrate denitratation.

A single up-flow thiosulfate-driven nitrate denitratation coupled with the sulfurized Anammox (TDSA) with the core-shell structure (S0@ Anammox granules) provided a chemical/energy-saving way for the removal of high-content ammonium with nitrate as electron acceptor. Approximately 83.66% total nitrogen removal efficiency (TNRE) could be achieved by the sulfurized Anammox encrusted by S0/Sn2- at a high loading rate (2.6 kg-N/(m3·d)) via resisting high concentration of free ammonia (FA) (22.35 mg/L), mainly through S2O32-, S0/Sn2- -driven partial denitrification-Anammox (PDN-Anammox) process. Moreover, S0/Sn2--PDN-Anammox was largely restricted when intermittently aerated, but still resulting in 74.47% TNRE due to the partial nitrification-Anammox (PN-Anammox). The sequencing analysis revealed that Anammox bacterium (Candidatus_Kuenenia) and sulfur-oxidizing bacterium (Thiobacillus) coexisted, in which Anammox process occurred mainly via NO instead of NH2OH. This study provided a new perspective for high concentration nitrogen wastewater removal in engineering applications.

Mixotrophic Chlorella pyrenoidosa as cell factory for ultrahigh-efficient removal of ammonium from catalyzer wastewater with valuable algal biomass coproduction through short-time acclimation.

To achieve ultrahigh-efficient ammonium removal and valuable biomass coproduction, Chlorella-mediated short-time acclimation was implemented in photo-fermentation. The results demonstrated short-time acclimation of mixotrophic Chlorella pyrenoidosa could significantly improve NH4+ removal and biomass production in shake flasks. After acclimation through two batch cultures in 5-L photo-fermenter, the maximum NH4+ removal rate (1,400 mg L-1 d-1) were achieved under high NH4+ level (4,750 mg L-1) in batch 3. In 50-L photo-fermenter, through one batch acclimated culture, the maximum NH4+ removal rate (2,212 mg L-1 d-1) and biomass concentration (58.4 g L-1) were achieved in batch 2, with the highest productivities of protein (5.56 g L-1 d-1) and total lipids (5.66 g L-1 d-1). The hypothetical pathway of nutrients assimilation in mixotrophic cells as cell factory was proposed with detailed discussion. This study provided a novel strategy for high-ammonium wastewater treatment without dilution, facilitating the algae-based "waste-to-treasure" bioconversion process for green manufacturing.

Nitrogen removal characteristics of a novel heterotrophic nitrification and aerobic denitrification bacteria, Alcaligenes faecalis strain WT14.

Alcaligenes faecalis strain WT14 is heterotrophic nitrification and aerobic denitrification bacterium, newly isolated from a constructed wetland, and its feasibility in nitrogen removal was investigated. The result showed sodium citrate was more readily utilized by WT14 as a carbon source. The response surface methodology model revealed the highest total nitrogen removal by WT14 occurred at 20.3 °C, 113.5 r·min-1, C/N 10.8, and pH 8.4. Under adapted environmental conditions, up to 55.9 mg·L-1·h-1 of ammonium nitrogen (NH4+-N) was removed by WT14, and its NH4+-N tolerance ability reached 2000 mg·L-1. In addition to the reported high NH4+-resistance of Alcaligenes faecalis, WT14 multiplied fast and had strong nitrate or nitrite removal capacity when high strength nitrate or nitrite was provided as the single nitrogen source; which differed from other Alcaligenes faecalis species. These results show WT14 is a novel strain of Alcaligenes faecalis and its nitrogen removal pathway will be carried out in the further study.

Endogenous ABA alleviates rice ammonium toxicity by reducing ROS and free ammonium via regulation of the SAPK9-bZIP20 pathway.

Ammonium (NH4+) is one of the principal nitrogen (N) sources in soils, but is typically toxic already at intermediate concentrations. The phytohormone abscisic acid (ABA) plays a pivotal role in responses to environmental stresses. However, the role of ABA under high-NH4+ stress in rice (Oryza sativa L.) is only marginally understood. Here, we report that elevated NH4+ can significantly accelerate tissue ABA accumulation. Mutants with high (Osaba8ox) and low levels of ABA (Osphs3-1) exhibit elevated tolerance or sensitivity to high-NH4+ stress, respectively. Furthermore, ABA can decrease NH4+-induced oxidative damage and tissue NH4+ accumulation by enhancing antioxidant and glutamine synthetase (GS)/glutamate synthetasae (GOGAT) enzyme activities. Using RNA sequencing and quantitative real-time PCR approaches, we ascertain that two genes, OsSAPK9 and OsbZIP20, are induced both by high NH4+ and by ABA. Our data indicate that OsSAPK9 interacts with OsbZIP20, and can phosphorylate OsbZIP20 and activate its function. When OsSAPK9 or OsbZIP20 are knocked out in rice, ABA-mediated antioxidant and GS/GOGAT activity enhancement under high-NH4+ stress disappear, and the two mutants are more sensitive to high-NH4+ stress compared with their wild types. Taken together, our results suggest that ABA plays a positive role in regulating the OsSAPK9-OsbZIP20 pathway in rice to increase tolerance to high-NH4+ stress.

Microbial ecology dynamics of a partial nitritation bioreactor with Polar Arctic Circle activated sludge operating at low temperature.

A lab-scale partial nitritation SBR was operated at 11 °C for 300 days used for the treatment of high-ammonium wastewater, which was inoculated with activated sludge from Rovaniemi WWTP (located in Polar Arctic Circle) in order to evaluate the influence the temperature on the performance, stability and dynamics of its microbial community. The partial nitritation achieved steady-state long-term operation and granulation process was not affected despite the low temperature and high ammonia concentration. The steady conditions were reached after 60 days of operation where the granular biomass was fully-formed and the 50%-50% of ammonium-nitrite effluent was successful achieved. Inoculation with cold adapted inoculum showed to yield bigger, denser granules with faster start-up without necessity of low temperature adaptation period. Next-generation sequences techniques showed that Trichosporonaceae and Xanthomonadaceae were the dominant OTUs in the mature granules. Our study could be useful in the implementation of full-scale partial nitritation reactors in cold regions such as Nordic countries for treating wastewater with high concentration of ammonium.

Stable and efficient partial nitritation granular sludge reactor treating domestic sewage at low temperature.

The success of combined partial nitritation (PN) and anammox process treating low-strength domestic wastewater depends on achieving a stable and efficient PN. In this study, desirable PN for domestic sewage with low temperature of 11.8-16.9 °C was achieved in a granular sludge reactor operated in anaerobic/aerobic (A/O) mode. Average nitrite accumulation ratio of 97.3% was obtained with an effluent nitrite/ammonium ratio of 1.2 for influent ammonium of 39.3-78.7 mg·L-1. Quantitative microbial analysis and activity batch test showed that nitrite oxidizing bacteria (NOB) were effectively suppressed, while ammonium oxidizing bacteria (AOB) were dominant. For the efficient suppression of NOB, A/O mode, aerobic phosphorus uptake and granular sludge could play important roles. Furthermore, high AOB activity was obtained with an average ammonium oxidation rate of 11.6 mg N·L-1·h-1, which could be due to the abundant psychrotolerant microorganisms, increased content of extracellular polymeric substances and relatively high dissolved oxygen condition of the reactor.

Hybrid algal photosynthesis and ion exchange (HAPIX) process for high ammonium strength wastewater treatment.

A hybrid algal photosynthesis and ion exchange (HAPIX) process was developed that uses natural zeolite (chabazite) and wild type algae to treat high ammonium (NH4+) strength wastewater. In the HAPIX process, NH4+ is temporarily adsorbed from the liquid, which reduces the free ammonia (FA) concentration below the inhibitory level for algal growth. The slow release of adsorbed NH4+ subsequently supports the continuous growth of algae. In this study, a HAPIX reactor reduced NH4+-N concentrations in centrate from an anaerobic digester from 1180 mg L-1 to below 10 mg L-1 without dilution. Chabazite doses of 60 g L-1 produced more algal biomass, with higher protein and starch contents, than doses of 150 g L-1 and 250 g L-1. Approximately 67-70% of fatty acids in the algal biomass harvested from HAPIX reactors were unsaturated. A mathematical framework that couples a homogeneous surface diffusion model with a co-limitation algal kinetic growth model reasonably predicted the algal biomass production and NH4+-N concentrations in the HAPIX reactors. The HAPIX process has the potential to serve a two-fold purpose of high NH4+-N strength wastewater treatment and agricultural or commercial biopolymer production.

Nitrogen removal from low COD/TN ratio manure-free piggery wastewater within an upflow microaerobic sludge reactor.

An upflow microaerobic sludge reactor (UMSR) was constructed in treating manure-free piggery wastewater with high ammonium concentration and a COD/TN ratio as low as 0.84. The UMSR offered an outstanding removal of NH4(+)-N and TN at 35°C and hydraulic retention time 8h subsequent to inoculated sludge acclimation. A short NO2(-)-N accumulation phase was observed whenever there was a considerable increase in TN loading rate (NLR), but decreased rapidly along with an evident increase in TN removal. Fed with raw wastewater at a NLR of 1.10 kg/(m(3)d), the average COD, NH4(+)-N and TN removal reached 0.72, 0.76 and 0.94 kg/(m(3)d), respectively. Inference drawn from stoichiometry based on the potential nitrogen removal pathways and the C/N ratio required by denitrification indicated that anammox was the main mechanism for NH4(+)-N and TN removal in the UMSR.

Partial nitrification in an air-lift reactor with long-term feeding of increasing ammonium concentrations.

The partial nitrification (PN) performance under high ammonium concentrations was evaluated in an airlift reactor (ALR). The ALR was operated for 253days with stepwise elevation of ammonium concentration to 1400mg/L corresponding nitrogen loading rate of 2.1kg/m(3)/d. The ammonium removal rate was finally developed to 2.0kg/m(3)/d with average removal efficiency above 91% and nitrite accumulation percentage of 80%. Results showed that the combined effect of limited DO, high bicarbonate, pH and free ammonia (FA) contributed to the stable nitrite accumulation substantially. The biomass in the ALR was improved with the inception of granulation. Precipitates on biomass surface was unexpectedly experienced which might improve the settleability of PN biomass. Organic functional groups attached to the PN biomass suggested the possible absorbability to different types of pollutant. The results provided important evidence for the possibility of applying an ALR to treat high strength ammonium wastewater.