Rapid start-up of mainstream partial denitrification /anammox and enhanced nitrogen removal through inoculation of precultured biofilm for treating low-strength municipal sewage.

This study investigated the rapid start-up of mainstream partial denitrification coupled with anammox (PD/A) and nitrogen removal performance by inoculating precultured PD/A biofilm. The results showed mainstream PD/A in the anaerobic-anoxic-aerobic (A2O) process was rapidly established within 30 days. Nitrogen removal efficiency (NRE) improved by 23.8 % contrasted to the traditional A2O process. The mass balance showed that anammox contribution to total nitrogen (TN) removal were maintained at 37.9 %∼55.7 %, and reducing hydraulic retention time (HRT) strengthened simultaneously denitrification and anammox activity. The microbial community showed that the dominant bacteria such as denitrifying bacteria (DNBs) and glycogen accumulating organisms (GAOs) both in biofilm and flocculent sludge (floc), integrating with anammox bacteria (AnAOB) in biofilm might lead to enhanced nitrogen removal. Overall, this study offered a fast start-up strategy of mainstream PD/A with enhanced nitrogen removal, which are valuable for upgradation and renovation of existed municipal wastewater treatment plants (WWTPs).

[Systematic Evaluation of Low-carbon Operation of Typical A2O Processes in Municipal Sewage Plant].

Under the "Carbon Peak, Carbon Neutral" goal, the systematic evaluation of the carbon emission equivalent (CO2eq) and its compositions of the typical A2O process has important guiding significance for the low-carbon operation of most municipal sewage plants in China. Based on the operational data on the first municipal sewage plant of Jiaozuo in 2020 and the methods presented in "2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, " a systematic evaluation of the CO2eq of the typical A2O process was established, including direct emissions that were built on the Arrhenius model introducing the water temperature factor and indirect emissions from the three aspects of electricity consumption, agent addition, and sludge transportation. The results showed that the daily emission intensities of CH4 and N2O were (115±56) kg·d-1 and (30±18) kg·d-1, respectively. Additionally, indirect carbon emissions from electricity consumption and agent addition accounted for 48.4% and 51.3% in the biochemical treatment section, respectively. In 2020, CO2eq amounts of total research plant and per unit sewage were 2.17×104 t and (0.63±0.07) kg·m-3, respectively. The magnitude of the proportion of different carbon emission compositions was as follows:sewage electricity (36.5%)>sewage agent (26.6%)>N2O direct (15.4%)>sludge agent (9.6%)>sludge electricity (6.7%)>CH4 direct (4.9%)>sludge transportation (0.3%). System import/export fluxes of carbon and nitrogen elements were calculated, followed by the carbon to nitrogen mass ratio in the sewage plant. Direct carbon emission characteristics of CH4 and N2O and their influencing factors were discussed, respectively. Based on the balance theory of carbon and nitrogen elements in the system, it is proposed that the selective introduction of industrial wastewater may become an important reference measure for the low-carbon operation of municipal sewage plants in the future.

Characteristics of the colony structure of A2O processes under different ultraviolet conditions in plateau areas.

In this text, a laboratory-scale A2O was performed in Linzhi City at a 3000-m altitude. During the test operation, the UV irradiation was carried out in oxic tank for 0, 5, 10, 30, and 180 min. The 16SrRNA gene sequencing was performed on the activated sludge in anaerobic, anoxic, and oxic tanks, and the colony structure characteristics of phyla, genera, and species classification levels in the sludge were analyzed. There were significant differences in the numbers of genera and species (p ≤ 0.05). The community richness, uniformity, diversity, and other indicators differed to some degree compared with those of other regions. The analysis of composition of bacterial colonies revealed different levels. The significance test of the difference between the groups, the significance of the dominant species, and the mechanism of UV was analyzed. A CCA diagram was used to verify that UV is an important factor in the colony structure composition, and the correlation heatmap diagram was used to analyze the microorganisms that are significantly related to UV. A sample hierarchical cluster analysis showed that the time of UV exposure can be divided into two categories, and the effects of UV exposure increase sequentially as the time of exposure increases. A comprehensive analysis found that the enhancing and inhibitory effects of UV affect the composition of the colony structure in the sample, and the time of irradiation will affect the enhancing or inhibitory effect, that is, the colony structure from the samples that were irradiated for different amounts of time differs greatly.

Removal of nitrogen from municipal wastewater by denitrification using a sulfur-based carrier: A pilot-scale study.

In the present study, to improve nitrate removal rate, a sulfur-based carrier was applied for autotrophic denitrification, and the removal rate was evaluated for advanced wastewater treatment without adding any external organic carbon source. Based on the results, an increased PAC concentration affected the removal efficiency of NO3--N, and the optimal concentration of PAC was at 15 wt%. During the 60 d operation of a pilot process with a capacity of 1 m3/d, the removal of T-N was 81.2% and 50.2% in reactors with and without sulfur-based carrier, respectively. The removal efficiency of NO3--N exhibited a similar trend to that of T-N. According to the results, the removal of T-N and NO3--N was noticeably enhanced to approximately 30% by adding a sulfur-based carrier to the A2O pilot system. In addition, microbial community in both reactors was dominated by Thiobacillus, which is an autotrophic microorganism, displaying a dominant denitrification status. The present study compared the relative efficiencies of nitrate removal in A2O pilot reactors with and without sulfur-based carriers for its successful application in real-scale autotrophic denitrification.

Removal efficiency of organic micropollutants in successive wastewater treatment steps in a full-scale wastewater treatment plant: Bench-scale application of tertiary treatment processes to improve removal of organic micropollutants persisting after secondary treatment.

The goal of this study was to investigate the occurrence and removal of 52 organic micropollutants (OMPs) during each wastewater treatment step in a full-scale wastewater treatment plant (WWTP). Pharmaceuticals such as metformin, acetaminophen, caffeine, ibuprofen, cimetidine and naproxen were found with high average concentrations in the influent. Most OMPs were not affected by the primary treatment (removal <10%), while secondary biological treatment contributed the most to overall removal of the OMPs. Among the three lanes of the secondary treatment of the WWTP, a combined anaerobic-anoxic-oxic process followed by a membrane bioreactor (A2O-MBR) process effectively facilitated removal of the OMPs (96%) using a different redox: a conventional activated sludge (CAS) process exhibited removal of approximately 85% of total concentrations of the OMPs, while a Modified Ludzack-Ettinger (MLE) process achieved approximately 92.1% removal. Removal of more than 50% of the concentrations of 13 targeted OMPs was observed in the secondary effluent (except for metformin showing only 3.8% removal) via adsorption with powdered activated carbon (PAC) as additional tertiary treatment. Metformin, inadequately removed by additional tertiary treatments, was effectively removed by a biological activated carbon (BAC) process, reaching a removal efficiency of 90.5%. To increase the removal of the amounts and types of OMPs with various physico-chemical properties, hybrid processes through a combination of diverse advanced treatment should be tailored to WWTPs.

[Construction and Denitrification Performance of A2/O Based on Partial Nitrification Coupled with an ANAMMOX System].

To resolve the issue of existing municipal wastewater treatment plants (WWTPs) in China with an insufficient influent carbon source, a bench-scale A2/O process based on partial nitrification coupled with ANAMMOX was constructed by controlling aeration partition ratio, dissolved oxygen (DO) concentration, and sludge retention time (SRT). In this study, the nitrogen removal performance, nitrogen removal pathway, and microbial community structure of the system under different conditions were investigated. The results showed that the system had excellent nitrogen removal efficiency at low-C/N influent (C/N=5). The A2/O reactor had experienced the co-culture stage (Phase 1), screening stage (Phase 2-3), and enrichment stage (Phase 4) successively during the 140-day experiment, and the nitrogen removal pathway changed from nitrification and denitrification to partial nitrification coupled ANAMMOX in the end. The optimal removal efficiencies of 97.69% for NH4+-N and 87.83% for TN were obtained in the enrichment stage (Phase 4), and the effluent concentration of NH4+-N and TN were 1.20 mg·L-1 and 7.03 mg·L-1, respectively. Illumina MiSeq sequencing results showed that the enrichment of AOB including Nitrosomonas and Nitrosospira and the elimination of NOB including Nitrospira, Nitrococcus, and Nitrobacter were the main causes of achieving partial nitrification in the system. The enrichment of AnAOB including Candidatus Kuenenia and Candidatus Jettenia was the key point for the occurrence of ANAMMOX in the system, and thus, played an important role in the achievement of advanced nitrogen removal.

Iron-carbon galvanic cells strengthened anaerobic/anoxic/oxic process (Fe/C-A2O) for high-nitrogen/phosphorus and low-carbon sewage treatment.

The treatment of sewage with high-nitrogen/-phosphorus and low-carbon remains a challenge. A novel iron-carbon galvanic cells strengthened anaerobic/anoxic/oxic process (Fe/C-A2O) was developed for high-nitrogen/-phosphorus and low-carbon sewage treatment. The cost-effective iron-scraps (ISs) was recycled as Fe(0)-source under the mediation of Fe/C galvanic cell reaction to develop effective Fe(0)-oxidizing autotrophic-denitrification and -dephosphorization. Utilizing practical high-nitrogen/-phosphorus and low-carbon sewage as target wastewater, the performance, impact factors, contribution of Fe/C galvanic cell reactions, microbial characteristics, strengthening mechanisms, and application potential of Fe/C-A2O process were investigated. The Fe/C-A2O process achieved high TN and TP removal efficiencies of 92.0 ± 1.3% and 97.2 ± 0.9% with removal loads of 0.176 ± 0.002 kg TN/(m3·d) and 0.017 ± 0.002 kg TP/(m3·d), respectively. Optimal HRT of 12 h, DO of 4.0-4.5 mg/L, and reflux-ratio of 4:1 were obtained, and no sludge-reflux was required. Autotrophic-denitrification and -dephosphorization supported by the Fe/C galvanic cell reactions contributed 63.1% and 75.3% of TN and TP removal, respectively. Microbial characterization revealed the dominance of autotrophic denitrifiers (e.g., Thiobacillus), AOB (e.g., Nitrosomonas), NOB (e.g., Nitrospira), and heterotrophic denitrifiers (e.g., Zoogloea). The mechanism analysis demonstrated that Fe/C galvanic cells strengthened nitrogen removal by raising Fe2+/H2-supported autotrophic denitrification; and strengthened dephosphorization by introducing Fe3+-based PO43--precipitation and enhancing the denitrifying phosphate-accumulation by denitrifying phosphate-accumulating organisms (DPAOs). Based on the efficiency and cost evaluation, the ISs-based Fe/C-A2O process showed significant application potential as an upgrade strategy for traditional A2O process in advanced high-nitrogen/phosphorus and low-carbon sewage treatment.

Effect of microbial community structure of activated sludge in an Anaerobic-anoxic-oxic process with Actinic reaction enzyme system start-up / 生物工程学报

In order to explore the microbial communities and functions of activated sludge in an Anaerobic-anoxic-oxic (A²/O) process under the start-up of Actinic reaction enzyme system (ARES) system and to understand the impact of the ARES system in domestic sewage treatment process, the activated sludge microbial community structure in the A²/O process system before and after ARES system start-up was analyzed by Illumina-HiSeq 2000 high-throughput sequencing platform. By combining with the main parameters related to the effect of sewage treatment, we analyzed the environmental functions of the microbial communities. The microbial community structure of activated sludge was significantly different before and after the ARES system start-up. There were 9 main bacterial phyla in the system (average relative abundance ≥1%), accounting for 96%-98% of the total bacteria sequenced. After the ARES system was started, the relative abundance of Betaproteobacteria and Chlorobi increased by 3.45%-3.85% and 0.45%-2.61%, respectively. In the anaerobic unit, the relative abundance of Bacteroidetes increased by 12.97%, while the Actinobacteria and Firmicutes decreased by 9.60% and 1.45%, respectively. At the genus level of bacteria, the relative abundance of Denitratisoma increased by 0.80%-3.27%, while the Haliangium and Arcobacter decreased by 3.36%-4.52% and 1.48%-3.45%, respectively. The relative abundance of bacteria was significantly different before and after the ARES system start-up. There were 7 abundant fungi phyla (average relative abundance ≥1%) in the system. After the ARES system was started, the relative abundance of Rozellomycota decreased by 42.71%-46.77%. In the anaerobic unit, the relative abundance of Ascomycota decreased by 13.39%, while the relative abundance of Glomeromycota increased by 13.86%. At the genus level of fungi. The relative abundance of Entomophthoraceae sp. and Glomcromycota sp. increased by 31.35%-36.50% and 6.27%-13.84%, respectively, while the Rozellomycota sp. and Xylochrysis lucida decreased by 42.71%-46.77% and 3.67%-5.54%, respectively. Our results showed that the application of ARES system caused the response of the microbial community to environmental changes, especially for the fungi communities, in the meanwhile, improved the effluent quality, especially the removal rate of total nitrogen.

[Effect of microbial community structure of activated sludge in an Anaerobic-anoxic-oxic process with Actinic reaction enzyme system start-up].

In order to explore the microbial communities and functions of activated sludge in an Anaerobic-anoxic-oxic (A²/O) process under the start-up of Actinic reaction enzyme system (ARES) system and to understand the impact of the ARES system in domestic sewage treatment process, the activated sludge microbial community structure in the A²/O process system before and after ARES system start-up was analyzed by Illumina-HiSeq 2000 high-throughput sequencing platform. By combining with the main parameters related to the effect of sewage treatment, we analyzed the environmental functions of the microbial communities. The microbial community structure of activated sludge was significantly different before and after the ARES system start-up. There were 9 main bacterial phyla in the system (average relative abundance ≥1%), accounting for 96%-98% of the total bacteria sequenced. After the ARES system was started, the relative abundance of Betaproteobacteria and Chlorobi increased by 3.45%-3.85% and 0.45%-2.61%, respectively. In the anaerobic unit, the relative abundance of Bacteroidetes increased by 12.97%, while the Actinobacteria and Firmicutes decreased by 9.60% and 1.45%, respectively. At the genus level of bacteria, the relative abundance of Denitratisoma increased by 0.80%-3.27%, while the Haliangium and Arcobacter decreased by 3.36%-4.52% and 1.48%-3.45%, respectively. The relative abundance of bacteria was significantly different before and after the ARES system start-up. There were 7 abundant fungi phyla (average relative abundance ≥1%) in the system. After the ARES system was started, the relative abundance of Rozellomycota decreased by 42.71%-46.77%. In the anaerobic unit, the relative abundance of Ascomycota decreased by 13.39%, while the relative abundance of Glomeromycota increased by 13.86%. At the genus level of fungi. The relative abundance of Entomophthoraceae sp. and Glomcromycota sp. increased by 31.35%-36.50% and 6.27%-13.84%, respectively, while the Rozellomycota sp. and Xylochrysis lucida decreased by 42.71%-46.77% and 3.67%-5.54%, respectively. Our results showed that the application of ARES system caused the response of the microbial community to environmental changes, especially for the fungi communities, in the meanwhile, improved the effluent quality, especially the removal rate of total nitrogen.

[Enhanced Nutrient Removal and Microbial Community Structure in a Step-feed A2/O Process Treating Low-C/N Municipal Wastewater].

To resolve the issue of insufficient influent carbon sources in existing municipal wastewater treatment plants (WWTPs) in China, a pilot-scale step-feed A2/O process was used to treat low-C/N (C/N<5) municipal sewage with five different inflow distribution ratios. In this study, the effects of influent flow distribution on the removal efficiencies of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were investigated. The results showed that optimal removal efficiencies of 89.41% for COD, 95.30% for NH4+-N, 83.00% for TN, and 90.09% for TP were obtained at an inflow QPA:QAN:QA distribution ratio of 0.1:0.2:0.3. The activated sludge exhibited excellent settleability characteristics, showing a sludge volume index (SVI)<120 mL·g-1 with an average volatile suspended solids (VSS) total suspended solids (TSS) ratio of 0.84 (Phase 5), and no filamentous bacteria bulking occurred during the 120-day experiment. Moreover, the microbial community structure in the oxic zone was detected by high-throughput sequencing. The results demonstrated that excellent nutrient removal and sludge settling performance of the system were closely related to the enrichment of six types of heterotrophic bacteria, four types of denitrifying bacteria, five types of polyphosphate-accumulating organisms (PAOs), and two types of zoogloea and the elimination of three types of filamentous bacteria.

Removal Efficiency and Risk Assessment of Polycyclic Aromatic Hydrocarbons in a Typical Municipal Wastewater Treatment Facility in Guangzhou, China.

The loading and removal efficiency of 16 US EPA polycyclic aromatic hydrocarbons (PAHs) were examined in an inverted A²/O wastewater treatment plant (WWTP) located in an urban area in China. The total PAH concentrations were 554.3 to 723.2 ng/L in the influent and 189.6 to 262.7 ng/L in the effluent. The removal efficiencies of ∑PAHs in the dissolved phase ranged from 63 to 69%, with the highest observed in naphthalene (80% removal). Concentration and distribution of PAHs revealed that the higher molecular weight PAHs became more concentrated with treatment in both the dissolved phase and the dewatered sludge. The sharpest reduction was observed during the pretreatment and the biological phase. Noncarcinogenic risk, carcinogenic risk, and total health risk of PAHs found in the effluent and sewage sludge were also assessed. The effluent BaP toxic equivalent quantities (TEQBaP) were above, or far above, standards in countries. The potential toxicities of PAHs in sewage effluent were approximately 10 to 15 times higher than the acceptable risk level in China. The health risk associated with the sewage sludge also exceeded international recommended levels and was mainly contributed from seven carcinogenic PAHs. Given that WWTP effluent is a major PAH contributor to surface water bodies in China and better reduction efficiencies are achievable, the present study highlights the possibility of utilizing WWTPs for restoring water quality in riverine and coastal regions heavily impacted by PAHs contamination.

Occurrence, fate, and mass balance of different classes of pharmaceuticals and personal care products in an anaerobic-anoxic-oxic wastewater treatment plant in Xiamen, China.

In this study, the occurrence and fate of 49 pharmaceuticals and personal care products (PPCPs) were investigated in an anaerobic-anoxic-oxic (A2/O) wastewater treatment plant (WWTP) for seven consecutive days using 24-h composite sampling technique. Special emphasis was placed to understand the distribution of PPCPs in dissolved and adsorbed phase, and to evaluate PPCP fate in different treatment units. Among the 49 PPCPs, 40 PPCPs in influent, 36 in effluent, 29 in sludge and 23 in suspended solids were detected at least once during sampling. Non-steroidal anti-inflammatory drugs (NSAIDs) and a stimulant were predominant PPCPs in influent whereas antibiotics were predominant in sludge, effluent and suspended solids. Removal efficiencies from the aqueous phase based on the dissolved PPCPs showed variable contribution in removing different PPCPs under screen and grit chamber, anaerobic treatment, anoxic treatment, oxic treatment and sedimentation-UV treatments, with the highest removal percentage by anaerobic process in terms of both individual and overall treatment. Mass load analysis showed that 352 g PPCPs enter the WWTP daily while 14.5 g and 58.1 g were discharged through effluent and excess sludge to the receiving sea water and soil applications, respectively. Mass balance analysis based on both aqueous and suspended PPCPs showed 280 g (79.4%) mass of influent PPCPs was lost along the wastewater treatment processes, mainly due to degradation/transformation.

Occurrence, behavior and removal of typical substituted and parent polycyclic aromatic hydrocarbons in a biological wastewater treatment plant.

Wastewater treatment plant (WWTP) effluent is the major source for substituted polycyclic aromatic hydrocarbons (SPAHs) to the receiving rivers, as well as the parent PAHs. Some of the SPAHs showed higher toxicities and levels than their parent PAHs. The occurrence and behavior of typical SPAHs were investigated in a representative biological WWTP in Beijing, China. Methyl PAHs (MPAHs) (149-221 ng/L in the influent; 29.6-56.3 ng/L in the effluent; 202-375 ng/g in the activated sludge), oxygenated PAHs (OPAHs) (139-155 ng/L; 69.9-109 ng/L; 695-1533 ng/g) and PAHs (372-749 ng/L; 182-241 ng/L; 2402-3321 ng/g) existed, but nitrated PAHs (NPAHs) were not detected. 2-Methylnaphthalene, anthraquinone, 9-fluorenone and 2-methylanthraquinone were the predominant SPAHs. OPAHs were deduced to be formed from PAHs especially during summer, based on the ratios variation and removal efficiencies of the two seasons, and the surplus mass in the outflows. Low molecular weight compounds (2-3 rings) might be mainly removed by mineralization/transformation and adsorption in the anaerobic unit, and by volatilization in the aerobic unit. High molecular weight compounds (4-6 rings) might be mainly removed by adsorption in the anaerobic unit. The total outflows of SPAHs and PAHs were 66 g/d in summer and 148 g/d in winter from the WWTP to the receiving river. The percentage of OPAHs was higher in summer than in winter.