Nutrient Removal Performance Research Articles

Enhanced nutrient removal from mainstream sewage via denitrifying dephosphatation, endogenous denitrification and anammox in a novel continuous flow process

It is a challenging subject to realize nitrogen and phosphorus elimination synchronously from limited-carbon sewage through conventional biological processes. Herein, a novel continuous flow anaerobic/oxic/anoxic/oxic (AOA-O) process, which integrated denitrifying dephosphatation, endogenous denitrification and anammox in the anoxic zone, was developed to enhance nutrient elimination from low carbon/nitrogen sewage (3.4 in average). After the long-term operation (280 days), a satisfactory nutrient removal performance (effluent PO43--P: 0.2 mg P/L, total inorganic nitrogen (TIN):8.9 mg N/L) was obtained. Mass balance indicated that anammox contributed to 26.1% TIN removal and denitrifying dephosphatation contributed to 25.6% phosphorus removal, respectively. The cooperation of anammox bacteria retained in biofilms and endogenous denitrifying bacteria in flocculent sludge was responsible for the enhanced nutrient removal in the anoxic zone. Dechloromonas carried out phosphorus uptake both under oxic conditions and anoxic conditions. This study can broaden the application prospect of mainstream anammox.

Biological nutrients removal performance under starvation stress: Efficacy deterioration and recovery

Biological nutrients removal performance affected by starvation stress was investigated via the addition of pre-anoxic stage to SBR. COD removal efficiency maintained at around 90% regardless of the starvation stress. Starvation stress presented significant impact on nitrogen and phosphorus removal, with noticeable reduction of TN removal and remarkable deterioration of TP removal as prolonging the pre-anoxic time, which was mainly attributed to the integrative effect of carbon source competition, depression of denitrification and invalid P release as well as the variation of microbial community. It was notable that starvation stress exerted distinct evolution on microbial community. The improvement in relative abundance of the certain genera relating to denitrification was the main reason for the partial recovery of nitrogen removal after eliminating stress starvation. The promotion of P uptake capacity accompanied with the relief of invalid P release and the enriched DPAOs accounted for the complete recovery of phosphorus removal.

Free-draining two-stage microbial fuel cell integrated constructed wetlands development using biomass, construction, and industrial wastes as filter materials: Performance assessment

This study reports organic, nutrient, and coliform removal performances in free-draining, three parallel two-stage microbial fuel cell (MFC)-based wetlands that were filled with organic, construction, industrial waste materials and planted with Canna indica. Two hydraulic load rates, i.e., 260 (Phase I) and 520 mm/d (Phase II), were employed. Mean ammoniacal nitrogen (NH4-N), total nitrogen (TN), total phosphorus (TP), coliform removal percentages of the organic, construction, industrial waste materials packed two-stage MFC-based wetland systems ranged between 88 and 96%, 83 and 94%, 59 and 78%, 72 and 100%, respectively, throughout the two operational periods. Chemical oxygen demand (COD) removal percentage in construction, industrial waste materials packed systems ranged between 66 and 79%. The organic waste media packed system achieved low COD removal (33%) during the first operational period that improved substantially (84%) during the last phase. Wastewater organic, nutrient removals were achieved by plant uptake, media-based adsorption, and microbial transformation. Nitrogen, phosphorus accumulation percentages in the plants tissue (with respect to total removal) ranged between 0.3 and 64%, 0.2 and 6%, respectively. Nitrogen, phosphorus concentration in the used media ranged between 0.4 and 13.5 g/kg, 0.7 and 1.1 g/kg, respectively. Maximum voltage and power density production across the construction waste jhama brick packed MFC-based wetland (i.e., 119 mV and 86 mW/m2, respectively) exceeded the bioenergy production of organic, industrial waste materials packed wetlands. Input organic load increment adversely impacted voltage production across all MFC-based wetlands. The carbon composition of the waste media partially supported electrochemical removal mechanisms. This study demonstrates a relatively stable pollutant removal performance of the free-draining construction, industrial waste media packed two-stage MFC-based wetlands despite input pollutant load increment.

Comparative evaluation of different operation scenarios for a full-scale wastewater treatment plant: Modeling coupled with life cycle assessment

All inputs and outputs of a technical system can be interpreted from an environmental point of view and some modifications, that are less harmful to the environment, can be incorporated into the system by using the life cycle assessment (LCA) approach. The energy footprint of wastewater treatment plants (WWTPs) is one of the most important environmental indicators. The sustainability of wastewater treatment systems can be evaluated in terms of energy consumption based on LCA. The aim of this study was to determine the environmental performance of a biological nutrient removal (BNR) plant in conjunction with mathematical modeling and the LCA approach based on three scenarios, which would reduce the net electricity consumption of the treatment plant by 10%. Three scenarios were constructed by the combinations of different values in dissolved oxygen (DO) concentration, sludge retention time (SRT) and internal recirculation (IR) parameters. A mathematical modeling study was carried out in order to determine the values of those parameters that decreased the net electricity consumption by 10%. Scenario 0 was developed based on a reference WWTP with default DO concentration, SRT and IR. The pairs of SRT and IR; SRT and DO; IR and DO were analyzed in Scenario 1, 2 and 3, respectively. The results showed that the global warming impact category has approximately the same values in Scenario 0 and Scenario 1 and these scenarios have the best performances in this category. Scenario 0 is also the best environmental performing with respect to marine eutrophication, while it has the highest environmental loads in terrestrial ecotoxicity and fossil resource scarcity categories. In freshwater eutrophication, Scenario 1 has the best environmental performance while the highest environmental burden in marine eutrophication is occurred in Scenario 1. Moreover, Scenario 1 and Scenario 2 have the same values and the worst environmental performances in the terrestrial acidification impact category. Scenario 1 and 2 have much better performances in fossil resource scarcity impact than in other scenarios while Scenario 2 is the worst environmental performing with respect to the global warming besides terrestrial acidification. Scenario 3 has a worse environmental performance in the freshwater eutrophication category in comparison to other scenarios, while it has the best environmental performances in the terrestrial acidification and terrestrial ecotoxicity categories. Scenario 1, 2 and 3 have better environmental performances in energy-related impact categories compared to the baseline scenario.

Seasonal Hydroclimatic and Soil Biogeochemical Drivers of N and P Availability in a Constructed Stormwater Wetland

Constructed stormwater wetlands are green stormwater infrastructure (GSI) practices with potential to treat stormwater nutrient pollution. GSI nutrient removal performance is controlled by GSI soil nutrient cycles, which depend on soil hydrologic and biogeochemical conditions. The objective of this study was to characterize spatial and temporal patterns in soil dissolved nutrients, and their relationships with soil conditions, at a constructed stormwater wetland in Milwaukee, Wisconsin. Ion exchange membranes were used to measure soil nutrient availability, which was combined with precipitation, air and soil temperature, soil moisture, and soil oxygen data. Nitrate was intermittent: 17% and 25% of the study period accounted for 50% and 67% of the total nitrate availability in the Upland and Lowland, respectively. Time-series data suggest this intermittency resulted from summertime N mineralization. Orthophosphate was higher in the well-aerated Upland than in the periodically anoxic Lowland with a larger contributing area. Regression results indicate that relationships between nutrient availability and environmental drivers depended on the nutrient and landscape position. Modeling spatiotemporal variability of GSI soil nutrient dynamics may improve system performance and prediction.

Nutrient removal performance within the biological treatment of the Marrakech wastewater treatment plant and characterization of the aeration and non-aeration process

Nutrient removal performance within the biological treatment of the Marrakech wastewater treatment plant and characterization of the aeration and non-aeration process

Can we use mine waste as substrate in constructed wetlands to intensify nutrient removal? A critical assessment of key removal mechanisms and long-term environmental risks

The utilization of natural ores and/or mine waste as substrate in constructed wetlands (CWs) to enhance nutrient removal performance has been gaining high popularity recently. However, the knowledge regarding the long-term feasibility and key removal mechanisms, particularly the potential negative environmental effects of contaminants leached from mine waste is far insufficient. This study, for the first time, performed a critical assessment by using different CWs with three mine waste (coal gangue, iron ore and manganese ore) as substrates in a 385-day experiment treating wastewater with varying nutrient loadings. The results showed that the addition of mine waste in CWs increased removal of total phosphorus (TP) by 17-34%, and total nitrogen (TN) by 11-51%. The higher removal of TP is mainly attributed to the strong binding mechanism of phosphate with the oxides and hydroxides of Mn, Fe and/or Al, which are leached out of mine waste. Moreover, integration of mine waste in CWs also significantly stimulated biofilm establishment and enriched the relative abundance of key functional genes related to the nitrogen cycle, supporting the observed high-rate nitrogen removal. However, leaching of heavy metals (Fe, Mn, Cu and Cr) from the beded mine waste in the experimented CWs was monitored, which further influenced cytoplasmic enzymes and created oxidative stress damage to plants, resulting in a decline of nutrient uptake by plants.

Growth and nutrients removal characteristics of attached Chlorella sp. using synthetic municipal secondary effluent with varied hydraulic retention times and biomass harvest intervals

Advanced nutrients removal from low strength municipal secondary effluent is of urgent need, while microalgae-based approaches can achieve satisfactory effluent polishing without extra chemicals and energy consumption, and the obtained biomass could be processed into value-added products. Conventional suspended systems are either faced with algae-water separation issue, or with the requirement of membrane modules and low scale-up probability. The widely applied attached systems for water remediation such as Algal Turf Scrubbers can resolve the algae-water separation issue, but the biofilm is often dominated by filamentous microalgae, which are of high ash content and low commercial value. Attached systems dominated by selected microalgal strains, however, are mostly fed with high strength wastewater, and the growth and nutrients removal characteristics of these microalgae using low strength effluent is so far unclear. This study explored the potential of using attached Chlorella sp. for synthetic municipal secondary effluent polishing and biomass production, and investigated the effects of hydraulic retention time (HRT) and biomass harvest interval on microalgal growth, extracellular polymeric substances (EPS) content, harvested biomass composition, and nutrients removal. When only HRT was concerned, highest microalgal growth rate (0.77 g/m2/d) and EPS content (80.8 mg/g dry cell weight, DCW) were found at HRT = 2 d, meanwhile total nitrogen and total phosphorus were respectively reduced to 1.2 mg/L and 0.1 mg/L. Attached microalgal growth increased to more than 1.2 g/m2/d at 4 d harvest interval, generating biomass with 27.9–35.2% protein, 20.6–23.4% polysaccharides, and 21.6–26.4% lipid. The biomass EPS content was significantly positively correlated to biomass productivity, reaching highest level (156.8 mg/g DCW) at 4 d harvest interval. Nutrients removal performances, however, were inferior to those without biomass harvest. The mismatch between attached microalgal growth and nutrients removal highlighted the need to balance biomass production and effluent polishing performances when using low strength effluent as culturing medium.

Enhancing the formation of simultaneous nitrification and denitrification (SND) biofilm and nitrogen removal performance using two-units IFFAS process filled with surface-modified carriers

Moving-bed biofilm reactor (MBBR) and integrated floating-film activated sludge (IFFAS) are considered as well-established technologies for simultaneous nitrification and denitrification (SND). However, SND biofilm formation and nutrient removal performance are generally limited by the innate physico-chemical properties of conventional suspended carriers and/or insufficient carbon source available for denitrification. In this study, novel surface-modified carriers were developed via introducing mixed functional materials (natural zeolite, cationic polyquaternium-10, insoluble biodegradable organic polybutylene succinate/bamboo powder) into polyethylene. The modified carrier revealed enhanced hydrophilicity, positive surface charge, higher surface free energy and carbon source slow release capacity. Biofilm growth feature showed that the surface-modification resulted in more biofilm formation and more polysaccharide and protein in extracellular polymeric substances (EPS), which was structural and functional beneficial for substrate capture, transfer and intercellular interactions between nitrifiers and denitrifiers. IFFAS reactor filled with novel modified carriers was upgraded by dividing into two vertical units, where alternate feeding and aeration was conducted to create an anoxic unit to enhance the utilization of influent carbon source for denitrification as well as an aerobic unit to strengthen nitrification. The two-units IFFAS reactor exhibited highly efficient SND performance with TN removal efficiency of 59.9–65.9%, increased by 12.3–13.5% compared with control group. This study proposed an approach towards enhancement of functional biofilm formation and SND performance, and had fascinating potential in actual applications.

Acute exposure effects of tetracycline, ampicillin, sulfamethoxazole, and their mixture on nutrient removal and microbial communities in the activated sludge of air-scouring and reciprocation membrane bioreactors

The fate of antibiotics, their effects on non-target species, and the spread of antibiotic resistance in wastewater treatment systems have been of concern in recent years. Despite its importance, the effects of these antibiotics on biological nutrient removal in WWTPs have not been completely elucidated. To evaluate the effects of antimicrobial compounds on nutrient removal performance and microbiome, batch experiments were performed using activated sludge samples taken from two distinct membrane bioreactor systems (reciprocation MBR vs. air-scouring MBR). We exposed the activated sludge to 0 mg/L, 0.1 mg/L, and 1.0 mg/L of tetracycline (TET), ampicillin (AMP), sulfamethoxazole (SUL), and their mixture. The mixture of antibiotics significantly decreased ammonia removal efficiency in the reciprocation MBR (rMBR) and air-scouring MBR (AS MBR) by 5% and 12%, respectively. A significant reduction (p < 0.05) in the amoA-AOB gene was observed in AS MBR, while this gene remained unaffected in the rMBR. Interestingly, the gene abundance of amoA from comammox Nitrospira increased from 2.8 × 108 gene copies per gram sludge (0 mg/L) to 5.0 × 108 gene copies per gram sludge (1.0 mg/L) in the setup with antibiotics in the mixture. Correlation analysis of the relative abundance of prevalent taxa and antibiotic concentrations showed that the microbial communities of the AS MBR were more susceptible to TET and MXD antibiotics than the rMBR microbiome.

Metagenomic insights into the effects of various biocarriers on moving bed biofilm reactors for municipal wastewater treatment

Preferable biocarrier is vital for start-up and operation of moving bed biofilm reactor (MBBR). Effects of three separate biocarriers - PPC, PU, and PP on MBBRs were systematically investigated including nutrients removal performances, biomass attachment, microbial community, and relevant functional genes. Results showed that three biocarriers achieved similar removal efficiencies for chemical oxygen demand (COD) and total phosphorus (TP), though much higher biomasses were found attached onto PPC and PU carriers. PPC and PU performed better than PP for ammonia nitrogen (NH4+-N) removal. However, PPC exhibited the greatest and most reliable denitrifying efficiency, mainly due to stronger simultaneous nitrification and denitrification during better micro-anoxic-environment created within PPC carriers than others. Further studies by 16S rRNA gene and metagenomic sequencing analysis uncovered the bacterial diversity and structures, and relevant functional genes for nitrogen-transformation and pathways of nitrogen metabolisms, which laid the biological basis for the best performances via biocarrier PPC. This study inspired a feasible approach for municipal wastewater treatment through PPC filled MBBR.

Performance of basalt fiber-periphyton in deep-level nutrient removal: A study concerned periphyton cultivation, characterization and application

Nutrients in centralized discharge area of treated sewage can cause high ecological risks to aquatic systems, thus a deep-level nutrient removal is necessary. Recently, periphyton has attracted increasing interests for its excellent performance in nutrient removal. In this study, the suitability and durability of basalt fiber (BF) as a new green carrier of periphyton was evaluated, and development process of basalt fiber-periphtyon (BFP) was tracked with bacterial community succession and physiological indicators. Then, well-developed BFP was applied to deeply purify water containing the same concentration of nutrient as the treated sewage. Results showed the periphyton could adapt to BF and formed in large quantities. In addition, the tensile strength of BF after being used as a carrier was still strong. Bacterial community and physiological indicators indicated that BFP was well developed in 40–50 days. LEfSE and random forest analysis revealed that Deinococcus-Deinococci, Spartobacteria and Chlamydiia at class-level, Rhizobiales and Rhodobacterales at order-level were the biomarkers for development of BFP. Moreover, application results showed BFP efficiently removed nitrogen and phosphorus from water and promoted the transformation of ammonia to nitrate. The concentration of ammonia and phosphorus severely decreased from 4.90 ± 0.11 mg/L to 0.51 ± 0.20 mg/L, from 0.66 ± 0.016 mg/L to 0.023 ± 0.013 mg/L, respectively. The efficient nutrient removal was attributed to accumulation of nitrogen and phosphorus metabolism related organisms in BFP as well as favorable water physic-chemical conditions created by BFP. These results suggest that BF is a suitable and durable green carrier of periphyton, and BFP could efficiently reduce ecological risk to aquatic systems receiving treated sewage.

Effect of zero-valent iron and granular activated carbon on nutrient removal and community assembly of photogranules treating low-strength wastewater

Traditional wastewater treatment processes with high energy consumption and greenhouse gas emissions are not suitable for rural areas with low sewage strength and wide distribution. In this study, a microalgae-bacteria synergistic photogranules system was developed under the impetus of green chemical additives to address these challenges. The results showed that zero-valent iron (ZVI) or granular activated carbon (GAC) addition made successful photogranulation treating low-strength wastewater with excellent settleability and stability performance (settling velocity: 14–22 m h−1; integrity coefficient: 0.81–6.62%), while systems without light or additives failed due to the bio-granules disintegration caused by the overgrowth of predators or phototrophic species. A better nutrient removal performance (TN < 15 mg L−1, TP < 0.4 mg L−1) was observed in photogranules systems, and stoichiometric and biological analysis found that the divisions of nitrogen removal by microalgae and bacteria were different for photogranules between GAC and ZVI additions. As a physical enhancer, GAC can be used as the nucleus of photogranules regenerating after granules disintegration rather than affecting the community succession process. However, ZVI addition strengthened the sedimentation ability and stability of photogranules through chemical and biological effects, focusing on enhancing bacterial community diversity, enriching biofilm formation bacteria and inhibiting the overgrowth of filamentous cyanobacteria. Notably, the photogranules process with ZVI addition could be operated under non-aeration conditions without compromising removal efficiency. There existed an ideal distribution of microalgae and bacterial functional species in the photogranules, which seemed to be essential for its self-sustained synergistic symbiosis and stability. Consequently, this work might provide engineering alternatives for realizing carbon neutrality and environmental sustainability of the decentralized wastewater treatment process for low-strength wastewater in rural areas.

Strengthening anoxic glycogen consumption in SNEDPR-CW as a strategy to control PAO–GAO competition under carbon limited condition

Cooperation between Phosphate and Glycogen Accumulating Organisms (PAOs and GAOs) plays a pivotal role in nutrients removal in simultaneous nitrification endogenous denitrification and phosphorous removal (SNEDPR) systems. Recent findings have expanded the application of SNEDPR from activated sludge system to constructed wetland (CW). However, how to regulate competition between PAOs and GAOs in SNEDPR-based CW is still unclear. Here we showed that, GAOs could easily gain dominance over PAOs in SNEDPR-CW under alternating anaerobic/aerobic (A/O) operational mode. Shortening aerobic hydraulic retention time (HRT) at low oxygen concentration was benefit for simultaneous nitrification endogenous denitrification (SNED) and denitrifying dephosphatation but would reduce the overall phosphorus uptake rate and lead to high phosphorus effluent concentrations. Extended aerobic HRT promoted the proliferation of aerobic GAOs over PAOs, decreasing both enhanced biological phosphorus removal (EBPR) and SNED performance. Surprisingly, by switching the operation of system to alternating anaerobic/aerobic/anoxic (A/O/A) mode, an extraordinary nutrients removal performance with mean nitrogen and phosphorus removal efficiency of 84.57% and 89.37% was achieved under carbon sources limited condition. Stoichiometric analysis demonstrated that adding anoxic stage strengthened the intracellular glycogen oxidization of GAOs for denitrification which compromised its subsequent anaerobic carbon sources uptake and PHA storage and provided sufficient carbon sources for PAOs. Microbial community analysis showed that numerical ratio of GAOs to PAOs decreased from 6.67 under A/O to 4.89 under A/O/A mode, which further indicated strengthening glycogen denitrification of GAOs should be an effective way to regulate microbial competition in order to obtain a desired nutrients removal performance in SNEDPR-CW.

Biochar addition into activated sludge mitigate antibiotic toxicity on nitrification performance

This work examined the effects of biochar (BC) and a plastic carrier (PC) on nitrification of activated sludge (AS) in the presence of antibiotic ciprofloxacin (CIP). It was found that 5 mg/L CIP significantly inhibited both ammonium and nitrite oxidation by >75%. While the addition of PC into a reactor showed no effects on the fate of CIP, the addition of BC substantially decreased CIP concentrations in the reactor, thereby significantly reducing the CIP-mediated inhibition on the nitrification performance. 16S rRNA gene-based community profiling revealed a significant change in the structure of the nitrifying community in the presence of CIP. While Nitrosomonas oligotropha and Nitrospira sp. were significantly inhibited by CIP, they recovered with the BC addition. Batch experiments were performed to determine removal routes of CIP in the BC-dosed reactor. While no significant removal of CIP occurred via abiotic routes such as volatilization, photolysis, and hydrolysis, CIP was removed primarily by adsorption to BC and co-metabolic biodegradation by the nitrifying community. The first-order removal rate constant of CIP was 0.63 d−1 in the nitrifying condition, which was increased to 0.86 d−1 with the BC addition. Overall, this study suggests that BC can be a promising additive into environmental bioprocesses for mitigating antibiotic toxicity and enhancing nutrient removal performance in the presence of high antibiotic loads.

Hydraulic and nutrient removal performance of vegetated filter strips with engineered infiltration media for treatment of roadway runoff

As a new strategy for treating excess nutrients in roadway runoff, a self-filtering roadway could be accomplished by including engineered infiltration media within a vegetated filter strip (VFS) located in the roadway shoulder. However, nutrient removal performance will depend on the design to effectively infiltrate roadway runoff and the capacity of subsurface media to sequester or remove nutrients from infiltrated runoff. The objective of this study is to test hydraulic and nutrient removal performance of a roadside VFS over varied rainfall-runoff event sizes and filter widths. Two identical 1:1 scale physical models of roadway shoulders and embankments, one containing engineered media (Treatment model) and the other without (Control model), were tested with simulated rainfall and runoff from 1- and 2-lane roadways. Overall, 32 paired hydraulic experiments and 28 paired nutrient removal experiments were completed to assess performance across frequent and extreme rainfall-runoff events. The results indicate that scalability of performance with filter width varied by parameter. Runoff generation scaled predictably with filter width, as runoff generated close to the pavement and total infiltration increased with filter length. A 6 m-wide VFS containing the engineered media infiltrated all rainfall-runoff except during the most extreme storm events (1-h storms of 76.2 mm and 50.8 mm), where respectively 35% and 22% of rainfall-runoff did not infiltrate and left the system as surface runoff. A majority of phosphorus was retained within a 1.5 m filter while nitrate removal was not observed until 6 m. The Treatment model strongly outperformed the Control model with respect to nitrate (arithmetic mean ± standard deviation of 94 ± 6% reduction vs. 23 ± 64% increase, p < .001) and total nitrogen removal (80 ± 5% vs. 38 ± 23% reduction, p < .001) due to higher rates of microbially-mediated denitrification in the Treatment model. The two models performed comparably with regard to phosphorus reduction (84 ± 9% vs. 82 ± 12% reduction). A minimum 6 m filter width is recommended to ensure sufficient infiltration of runoff and nitrogen removal. Results of this study address uncertainty regarding nutrient removal performance of VFS in urban runoff applications and highlight a potential strategy for standardizing VFS performance across varied soil properties by including engineered media within the filter.

Acclimation of an algal consortium to sequester nutrients from anaerobic digestate

The objective of this research was to investigate the growth, community composition, and digestate treatment performance of a local algae consortium that was adapted to bacteria-pretreated digestate. The approach was to subculture a local consortium on pretreated dairy manure digestate and then municipal wastewater sludge digestate, allowing the community to adapt before assessing its performance. The adapted consortium was then tested for growth and nutrient removal performance on the digestates and compared to the model organism, Chlorella sorokiniana. Dramatic restructuring of the consortium took place when subcultured on the digestates with Scenedesmaceae and Chlorellaceae almost completely replacing Euglena. The consortium was consistently less productive than C. sorokiniana (184 vs. 248 mg/L/d in dairy digestate and 32 vs. 48 mg/L/d in municipal digestate, P < 0.01). Pretreatment increased growth by 81% and 500% for C. sorokiniana and the consortium, respectively, in dairy digestate (P < 0.01), and allowed for algal growth in municipal digestate.

Evaluating Long-Term Treatment Performance and Cost of Nutrient Removal at Water Resource Recovery Facilities under Stochastic Influent Characteristics Using Artificial Neural Networks as Surrogates for Plantwide Modeling

Evaluating Long-Term Treatment Performance and Cost of Nutrient Removal at Water Resource Recovery Facilities under Stochastic Influent Characteristics Using Artificial Neural Networks as Surrogates for Plantwide Modeling

Effects of Dissolved Oxygen on Nutrient Removal Performance and Microbial Community in Low Carbon/Nitrogen Municipal Wastewater Treatment Process

To explore the effects of dissolved oxygen (DO) on the treatment of low carbon/nitrogen municipal wastewater, this study examined the characteristics of the microbial community in a low carbon source environment. The treatment process was conducted with the aeration area having DO concentrations of 2-3, 1-2, and lower than 1 mg·L-1. The results demonstrated that reduced DO concentration in the aeration area increased the efficiency of the nitrogen removal process by 20.23% and 80.54%, for external and internal carbon sources, respectively. Similarly, the efficiency of internal carbon source utilization in the phosphorus removal process increased by 13.89%, thus enhancing the nutrient removal efficiency of the low carbon/nitrogen wastewater treatment system. High-throughput sequencing and RDA analysis showed that reduced oxygen concentration motivated an adjustment in microbial community structure, causing functional microorganisms (i.e., Dechloromonas) to become dominant. In addition, the upregulation of genes associated with energy production and conversion, signal transduction, substrate transport, and metabolism provided favourable nutritional conditions for the proliferation of functional microorganisms in low carbon source conditions. This study provides a theoretical basis for improving the growth of microorganisms involved in the nutrient removal process when treating low carbon/nitrogen municipal wastewater.

Stability and nutrients removal performance of a Phanerochaete chrysosporium-based aerobic granular sludge process by step-feeding and multi A/O conditions

A Phanerochaete chrysosporium-based aerobic granular sludge (PC-AGS) was developed by inoculating fungal mycelial pellets into a lab-scale aerobic granular sequencing batch reactor (AGSBR). A strategy using step-anaerobic feeding coupled with multi A/O conditions was adopted. The results showed that the removal efficiencies for total phosphorus (TP) and total inorganic nitrogen (TIN) were 94.56 ± 2.92% and 75.20 ± 7.74%, respectively, under relatively low aeration time. Compared with original AGS, the content of extracellular proteins for PC-AGS obviously increased from 18.61 to 41.44 mg/g MLSS by the end of phase I. Moreover, the mature granules had a larger size and better stability during the 100 days operation. Furthermore, the analysis of microbial diversity detected many key functional groups in PC-AGS granules that were beneficial to nutrients removal. This work demonstrated that the addition of fungal pellets not only enhanced the removal performance, but also improved the stability of the AGS system.