Ammonia Removal Efficiency Research Articles

Study of the key biotic and abiotic parameters influencing ammonium removal from wastewaters by Fe3+-mediated anaerobic ammonium oxidation (Feammox)

The release of ammonia (as NH4+) into water bodies causes serious environmental problems. Therefore, the removal of ammonia from wastewater effluents has become a worldwide concern. New autotrophic biological alternatives for ammonia removal could reduce the limitations of conventional organic carbon-dependent nitrification-denitrification methods. Here, the potential of anaerobic ammonium oxidation coupled to Fe3+ reduction (a process known as Feammox) is studied in wastewater treatment plants of the yeast and beer production industry, not related to ammonium or iron treatment. This process is presented as a viable option to improve the efficiency of ammonia removal from wastewater. The results of this study show that enrichments under Feammox conditions achieved removals of 28.19–32.25% of the total NH4+. The highest rates of ammonium removal and Fe3+ reduction were achieved using FeCl3 as iron source and pH = 7.0. Different environmental conditions for the enrichments were studied and it was found that the use of sodium acetate as a carbon source and an incubation temperature of 35 °C presented higher rates of iron reduction and higher increase in nitrate concentration, related to ammonium oxidative processes. Likewise, the presence of relevant species of the iron and nitrogen cycles as Ferrovum myxofaciens, Geobacter spp, Shewanella spp, Albidiferax ferrireducens and Anammox was verified, supporting the findings of this study. These results provide information that may be relevant to the potential applicability of Feammox to treat wastewater with high ammonia load and could help develop cost-effective and environmentally friendly methods for ammonium removal in wastewater treatment plants.

Responses of halophilic microbial communities to changes in salt composition: Comparison between autotrophic nitrification and heterotrophic ammonia assimilation biosystems

The concentration and proportion of chlorine (Cl−) and sulfate ions (SO42−) in actual high salinity wastewater exhibit significant fluctuations due to their diverse sources. This study compared the response of halophilic autotrophic nitrification (AN) and heterotrophic ammonia assimilation (HAA) sludges to changes in salt composition. The results demonstrated that both the AN and HAA systems maintained high ammonia removal efficiency even when exposed to mixed salt ions or pure sulfate conditions. Increasing the concentration of SO42− resulted in an increase in extracellular polymeric substances content, sludge settleability, sludge hydrophobicity, and the relative abundance of Nitrosomonas in the AN system (from 2.3% to 10.4%). The dominant heterotrophic bacteria in the HAA system underwent turnover in response to changes in salt composition conditions. The robustness and the cooperation between microorganisms of the HAA system surpassed those of the AN system. This study provides scientific foundation for treating multi-ion high salinity wastewater.

Microalgal-bacterial aerobic granular sludge for old leachate treatment: Development, performance, and lipid production

A lab-scale photo bio sequencing batch reactor (PSBR) was used to develop microalgal-bacterial aerobic granular sludge (MB-AGS) for old leachate treatment by seeding activated sludge, while indigenous microalgae were allowed to grow naturally. Upon 100 days of experiment, mature MB-AGS was successfully developed with an average diameter of 2.5 ± 1.5 mm and excellent settling properties, with a settling velocity of 39 ± 24 m/h. The biochemical oxygen demand (BOD), chemical oxygen demand (COD), ammonia (NH4+-N), total nitrogen (TN), and total phosphorus (TP) removal efficiencies were 80 ± 14%, 95 ± 2%, 88 ± 14%, 56 ± 16%, and 57 ± 14%, respectively. The shift in microbial populations were also examined, in which the abundant EPSs producing bacteria in the system could be one of the reasons behind the successful transformation of activated sludge flocs to mature MB-AGS. Furthermore, lipid was able to be extracted from the MB-AGS, in which the lipid production was 9.35 ± 1.1 mg/g-SS, accounting 0.56 ± 0.07 mg/L.d of lipid productivity.

The responding mechanism of indigenous bacteria in municipal wastewater inoculated with different concentrations of exogenous microalgae

Indigenous bacteria popularly exist in real wastewater. Therefore, the potential interaction between bacteria and microalgae is inevitable in microalgae-based wastewater treatment systems. It is likely to affect the performance of systems. Accordingly, the characteristics of indigenous bacteria is worth serious concerning. Here we investigated the response of indigenous bacterial communities to variant inoculum concentrations of Chlorococcum sp. GD in municipal wastewater treatment systems. The removal efficiency of COD, ammonium and total phosphorus were 92.50%–95.55%, 98.00%–98.69%, and 67.80%–84.72%, respectively. The bacterial community responded differently to different microalgal inoculum concentrations, which was mainly affected by microalgal number, ammonium and nitrate. Besides, there were differential co-occurrence patterns and carbon and nitrogen metabolic function of indigenous bacterial communities. All these results indicated that bacterial communities responded significantly to environmental changes caused by the change of microalgal inoculum concentrations. The response of bacterial communities to different microalgal inoculum concentrations was beneficial for forming a stable symbiotic community of both microalgae and bacteria to remove pollutants in wastewater.

Microalgae Cultivation Using Municipal Wastewater and Anaerobic Membrane Effluent: Lipid Production and Nutrient Removal

Microalgae cultivation using wastewater is a combined process for pollutant removal and lipid production that has been widely studied in recent years. In this study, the effects of anaerobic membrane effluent (AME) and municipal wastewater (MW) ratios on microalgae growth and pollutant removal processes were investigated, and the lipid production properties were also explored. Results show that microalgae can grow in all AME/WW ratios, and a 40% AME content is the optimal condition for microalgal biomass accumulation (52.9 mg/L·d) and lipid production (0.378 g/L). Higher AME addition would inhibit microalgae growth. In addition, high ammonia (approximately 97%) and phosphate (around 90%) removal efficiencies can be achieved in all AME/WW ratio conditions, while the total nitrogen removal efficiencies decreased with the addition of AME. Total nitrogen and phosphate are the limiting factors in treating water to meet the requirements of the integrated wastewater discharge standard. This study provided a new method for anaerobic digestion and municipal wastewater treatment and also realized green energy production based on the sustainable development principles.

Nanobubble aeration enhanced wastewater treatment and bioenergy generation in constructed wetlands coupled with microbial fuel cells

Artificial aeration is a widely used approach in wastewater treatment to enhance the removal of pollutants, however, traditional aeration techniques have been challenging due to the low oxygen transfer rate (OTR). Nanobubble aeration has emerged as a promising technology that utilise nano-scale bubbles to achieve higher OTRs owing to their large surface area and unique properties such as longevity and reactive oxygen species generation. This study, for the first time, investigated the feasibility of coupling nanobubble technology with constructed wetlands (CWs) for treating livestock wastewater. The results demonstrated that nanobubble-aerated CWs achieved significantly higher removal efficiencies of total organic carbon (TOC) and ammonia (NH4+-N), at 49 % and 65 %, respectively, compared to traditional aeration treatment (36 % and 48 %) and the control group (27 % and 22 %). The enhanced performance of the nanobubble-aerated CWs can be attributed to the nearly three times higher amount of nanobubbles (Ø < 1 μm) generated from the nanobubble pump (3.68 × 108 particles/mL) compared to the normal aeration pump. Moreover, the microbial fuel cells (MFCs) embedded in the nanobubble-aerated CWs harvested 5.5 times higher electricity energy (29 mW/m2) compared to the other groups. The results suggested that nanobubble technology has the potential to trigger the innovation of CWs by enhancing their capacity for water treatment and energy recovery. Further research needs are proposed to optimise the generation of nanobubbles, allowing them to be effectively coupled with different technologies for engineering implementation.

Ammonia Air Stripping from Different Livestock Effluents Prior to and after Anaerobic Digestion

Livestock digestate provides nutrients and organic matter to the soil while increasing agricultural sustainability. Nevertheless, nitrogen (N) losses due to the nutrient surplus in regions characterized by intensive animal farming activities still represent an unsolved issue. For this purpose, digestate needs proper treatment and management to avoid N losses in the environment. In the livestock farming context, anaerobic digestion (AD) can be accompanied by an ammonia stripping (AS) process for N recovery. This paper aims to investigate the feasibility AS prior to and after AD of the manure, focusing on two different livestock farms, representative of dairy cattle and pig breeding in southern Italy. AS was performed at a lab scale by injecting microbubbles of air, which allowed the pH to increase, and thus the removal of ammonia. The results show that treating a dairy raw slurry with high intermediate alkalinity (IA) (6707 mg CaCO3 L−1) with AS may not be convenient in terms of total ammonia nitrogen (TAN) reduction. As a matter of fact, the loss of buffering capacity during the stripping process resulted in a pH never exceeding the value of 9, which could not promote free ammonia volatilization, whereas integrating AD with AS allowed us to obtain a 34% higher TAN reduction under the same stripping conditions at a temperature (T) of 38 °C and a gas-to-liquid ratio (G/L) of 1:1. Therefore, the AS removal efficiency strongly depends on the characteristics (mainly IA) of the treated matrix. High IA values suggest a possible high concentration of volatile fatty acids, which hinders pH increases and, thus, enables ammonia stripping. Despite the initial matrix origin, a low IA compared to the total alkalinity (TA) (&lt;20% of TA) ensures a greater ammonia removal efficiency, which could be similar between digestate and raw manure in the same operative process conditions. Nonetheless, the amount of ammonia stripped is related to the initial TAN concentration of the specific matrix.

Effect of biocarriers on the nitrification and microbial community in moving bed biofilm reactor for anaerobic digestion effluent treatment

The performance of a moving bed biofilm reactor (MBBR) depends largely on the type of biofilm carrier used. However, how different carriers affect the nitrification process, particularly when treating anaerobic digestion effluents, is not completely understood. This study aimed to evaluate the nitrification performance of two distinct biocarriers in MBBRs over a 140-d operation period, with a gradually decreasing hydraulic retention time (HRT) from 20 to 10 d. Reactor 1 (R1) was filled with fiber balls, whereas a Mutag Biochip was used for reactor 2 (R2). At an HRT of 20 d, the ammonia removal efficiency of both reactors was >95%. However, as the HRT was reduced, the ammonia removal efficiency of R1 gradually declined, ultimately dropping to 65% at a 10-d HRT. In contrast, the ammonia removal efficiency of R2 consistently exceeding 99% throughout the long-term operation. R1 exhibited partial nitrification, whereas R2 exhibited complete nitrification. Analysis of microbial communities showed that the abundance and diversity of bacterial communities, particularly nitrifying bacteria such as Hyphomicrobium sp. And Nitrosomonas sp., in R2 was higher than that in R1. In conclusion, the choice of biocarrier significantly impact the abundance and diversity of microbial communities in MBBR systems. Therefore, these factors should be closely monitored to ensure the efficient treatment of high-strength ammonia wastewater.

Efficient ammonia removal promoted in a bifunctional system constructed with NiCu–S/DSA electrodes

Currently, the treatment of ammonia in wastewater, one of the main causes of eutrophication in water bodies, has received widespread attention. In this work, a novel electrocatalytic bifunctional system was constructed to achieve efficient degradation of ammonia. It consists of Ni1Cu0.25-S/DSA electrodes with both anode and cathode, which is prepared by a combination of electrodeposition and electrochemical tuning strategies. The crystalline phases and oxidation states of the nano-textured particulate metal oxides were determined by using a series of physical characterizations. The Ni1Cu0.25-S/DSA electrode with the best electrocatalytic performance was screened by electrochemical analysis, which has good stability and reliability when processing ammonia nitrogen. The efficiency of electrodes for ammonia removal was verified by running denitrification of synthetic and real wastewater. The results showed that the NH4+-N removal efficiency could approach up to 99%. Kinetically, compared with the monofunctional system, the bifunctional system obtained a higher NH4+-N degradation rate of 45.5 mg L−1 h−1, increased the rate of N2 generation by more than 10 times, and reduced the rate of NO3−-N and NO2−-N generation by one-third on average. The possible reaction mechanism of anodic ammonia oxidation and cathodic nitrate reduction in the bifunctional system was proposed.

Negative-pressure gas-diffusion electrode for effective ammonia recovery in bioelectrochemical systems

Recovery of ammonia from wastewater attracts increasing attentions as a sustainable way of nitrogen treatment. Here a novel gas-diffusion electrode membrane with negative-pressure extraction was developed in bioelectrochemical systems, achieving the highest ammonia recovery rate of 178 gNH3–N/(m2·d) with a low energy consumption (2.41 kW h kgNH3–N−1). The conjugate acid–base conversion of ammonium consumed OH− near the cathode, enhanced current density by decreasing overpotential which in turn facilitated the ammonia recovery. With an optimized thickness of 0.5 mm, the membrane electrode achieved ammonia removal and recovery efficiencies of 83% and 77% at 0.03 MPa, and the performance was highly repeatable after 20 recovery cycles. Modeling prediction exhibited a better performance under a higher vacuum, where the back-diffusion effect can be effectively mitigated. The membrane electrode can be fabricated at a low cost of 13.5 $ m−2, showing a potential usage in ammonia recovery from wastewater.

Pilot Study of Oxic–Anoxic Process under Low Dissolved Oxygen for Nitrogen Removal from Low COD/N Tropical Wastewater

Conventionally, nitrification in biological nitrogen removal (BNR) requires high dissolved oxygen (DO) concentrations (&gt;2 mg L−1), making the process energy intensive. Recent studies have shown that efficient ammonium removal and energy reduction can be realized by operating the nitrification at low DO concentrations (&lt;1 mg L−1). In this study, the low-DO oxic anoxic (low-DO OA) process was operated in a pilot-scale sequencing batch reactor (SBR) over 218 days to evaluate the feasibility of nitrogen removal from low chemical oxygen demand-to-nitrogen ratio (COD/N) tropical municipal wastewater. The results revealed that the low-DO OA process attained high removal efficiency for ammonium (97%) and total nitrogen (TN) (80%) under an average DO concentration of 0.6 mg L−1. The effective TN removal efficiency is attributed to the occurrence of simultaneous nitrification–denitrification (SND) under low DO conditions. Further batch tests revealed that slowly biodegradable COD (sbCOD) in tropical wastewater can support denitrification in the post-anoxic phase, resulting in a high TN removal rate. Compared with high DO concentrations (2 mg L−1), low DO conditions achieved 10% higher TN removal efficiency, with similar ammonium and COD removal efficiency. This study is crucial in promoting the energy efficiency and sustainability of wastewater treatment plants treating low COD/N wastewater.

Impact of Dissolved Oxygen on the Performance and Microbial Dynamics in Side-Stream Activated Sludge Hydrolysis Process

Dissolved oxygen (DO) plays an important role in the performance of biological wastewater treatment systems. This study investigated the effect of the DO concentration on nutrient removal performance and microbial community structure in side-stream activated sludge hydrolysis (SSH) and conventional anaerobic/anoxic/aerobic (A2O) processes. The results showed that the change in DO had little effect on the removal performance of chemical oxygen demand (COD), and the removal efficiencies were about 90% for both reactors. Compared with the high DO level (4.1–6.9 mg/L), the A2O and SSH reactors had better nitrogen removal performance at low (0.5–2.2 mg/L) and moderate (2.2–3.9 mg/L) DO levels, with ammonia (NH4+-N) removal efficiencies of 88–89% and 89–91%, respectively, and total nitrogen (TN) removal efficiencies of 74–76% and 75–81%, respectively. Directly reducing the DO concentration from high to low reduced the phosphate removal efficiencies of the A2O and SSH reactors from 80.2% and 86.2% to 63.1% and 70.6%, respectively, while re-elevating the DO concentration to moderate levels significantly improved the phosphate removal efficiencies to 94.6% and 96.0%, respectively. Compared to the A2O reactor, the SSH reactor had more stable and better nutrient removal performance under different DO conditions, partly due to the additional carbon sources produced through the sludge fermentation in the side-stream reactor. The decrease in the DO concentration resulted in a decrease in the relative abundance of Acinetobacter but an increase in the relative abundance of Competibacter, potentially leading to the deterioration in phosphorus removal.

Impact of zero-valent iron on nitrifying granular sludge for 17α-ethinylestradiol removal and its mechanism

Aerobic granulation of nitrifying activated sludge could enhance the removal of 17α-ethinylestradiol (EE2) via abiotic nitration induced by reactive nitrogen species, cometabolism by ammonia-oxidizing bacteria and biodegradation by heterotrophic bacteria. Zero-valent iron (ZVI), a promising and low-cost material, has previously been applied to effectively enhance biological wastewater treatment. The impact and the effect mechanism of ZVI on nitrifying granular sludge (NGS) for EE2 removal was investigated in this study. The results showed that the addition of ZVI achieved better EE2 removal, though ZVI was not conducive to the accumulation of nitrite in NGS which reduced the abiotic transformation of EE2. Moreover, ZVI enriched heterotrophic denitrifying bacteria such as Arenimonas, thus changing the EE2 removal pathway and improving the degradation and mineralization of EE2. In addition, ZVI reduced the emission risk of the greenhouse gas N2O and strengthened the stability of the granules. Metagenomic analysis further revealed that the functional genes related to EE2 mineralization, nitrite oxidation, N2O reduction and quorum sensing in NGS were enriched with ZVI addition. This study provides meaningful guidance for ZVI application in the NGS process to achieve efficient and simultaneous removal of ammonia and emerging contaminants.

Performance of simultaneous carbon, nitrogen, and phosphorus removal from vegetable oil refining wastewater in an aerobic-anoxic sequencing batch reactor (OA-SBR) system by alternating the cycle times

Carbon (C), nitrogen (N), and phosphorus (P) pollutants are among the most common environmental contaminants in different types of industrial wastewater, and they are a pollution factor that causes the eutrophication of receiving aquatic systems. An aerobic-anoxic sequencing batch reactor (O/A-SBR) system was studied to enhance the efficiency of vegetable oil refining wastewater treatment (VORW). Reactors were exploited with a total cycle period of 24 h (20 min filling, 17 h aeration, 4 h anoxic, 2 h settling, 20 min draw, and 20 min idle). SBR efficiency was evaluated by measuring pH, turbidity, chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and nutrients such as nitrate, ammonium, and phosphate. The results showed better performance from the start of operation with COD (83%), BOD5 (94%), turbidity (80%), nitrate (93%), ammonium (96%), and phosphate (91%) removal efficiencies. As industrial wastewater treatment is an important and complicated issue regarding environmental pollution, SBR can provide a better solution. The O/A-SBR system is a promising option that the VOR industry may adopt as a pre-treatment due to its more effective, inexpensive, and simple operation for organic matter and nutrient removal.

From black water to flushing water: potential applications of chlorine-mediated indirect electrooxidation for ammonia removal

Removing ammonia from black water is one of the most urgent issues before it can be recycled as flushing water. In this study, an electrochemical oxidation (EO) process with commercial Ti/IrO2-RuO2 anodes to treat black water could remove 100% of different concentrations of ammonia by adjusting the dosage of chloride. Through the relationship between ammonia, chloride, and corresponding the pseudo-first-order degradation rate constant (Kobs), we could determine the chloride dosage and predict the kinetics of ammonia oxidation based on initial ammonia concentration in black water. The optimal N/Cl molar ratio was 1:1.8. The difference between black water and the model solution in terms of ammonia removal efficiency and oxidation products was explored. A higher chloride dosage was beneficial for removing ammonia and shortening the treatment cycle, but it also led to the generation of toxic by-products. Especially HClO and ClO3- generated in black water were 1.2 and 1.5 times more than the synthesized model solution under 40mAcm-2. Through SEM characterization of electrodes and repeated experiments, the electrodes always maintained a high treatment efficiency. These results demonstrated the potential of the electrochemical process as a treatment method for black water.

Fish waste capped and colloidal nanosilver and its valorization as natural zeolite conjugates for application in aquaculture

The synthesis of silver nanoparticles has gained interest due to their diverse applications in various fields. It is very essential to use capping agents to avoid loss of nanosized characteristics due to agglomeration of AgNPs. In the present investigation, a simple and environmentally viable protocol to synthesize a wide range of concentrations of non-agglomerated and colloidal AgNPs using extracts of discarded wastes (gills and intestine) of Tilapia (Oreochromis mossambicus) in three different aqueous media without the requirement of any additional stabilizing and capping agent is described. The size of most of AgNPs ranged from 2 to 20 nm, followed by sizes of 20–40 nm and some with sizes of 40–50 nm. Zeta potential was in the range of −31.1 to −52.8 mV and −33.3 to −53.6 mV, and surface plasmon resonance ranged from 405 to 410 nm for gill and intestine extracts respectively. HR-TEM images indicated that Phosphate buffer saline is the best suitable for synthesizing non-agglomerated AgNPs capped with biomolecules. Valorization has been achieved by trapping Ag NPs into two different forms of natural zeolites namely stilbite and mordenite and their ammonia removal efficiency have been evaluated. In addition, the antimicrobial activity of synthesized AgNPs and their valorized products exhibited potent inhibitory activity against test bacteria such as Escherichia coli and Aeromonas hydrophila. This study not only establishes a simple and environmentally viable protocol for the synthesis of AgNPs and valorized products for environmental and disease management but also adds to the utilization of fish wastes in solid waste management.

Effect of plant-self debris on nitrogen removal, transformation and microbial community in mesocosm constructed wetlands planted with Myriophyllum aquaticum

Aquatic macrophytes debris decomposition could release pollutants and nutrients into the water of constructed wetlands (CWs), but their role in nitrogen removal and transformation remains poorly understood. The present study investigated the effects of plant-self debris on nitrogen removal and microbial communities in mesocosm CWs planted with Myriophyllum aquaticum. During the 68-day operation, the plant debris addition did not change the mean removal efficiency of ammonium (NH4+-N) and total nitrogen (TN) of CWs but showed significant differences over the operation time. The NH4+-N and organic nitrogen released from the plant debris decomposition affected the nitrogen removal. The plant debris decreased the effluent nitrate concentration and N2O emission fluxes of the CWs with the increased abundance of denitrifying bacterial genera, indicating that plant debris decomposition increased the denitrification activities via dissolved organic carbon release. High-throughput sequencing indicated that the plant debris altered the distribution and composition of the microbial community in the sediments. Proteobacteria was the dominant phylum (28–52%), and the relative abundance of denitrifying bacteria genera was significantly higher in the sediments with debris addition (37–40%) than in the non-addition (6.6–7.7%). The present study provided new insights into the role of macrophytes in pollutant removal and the plant management strategy of CWs.

Microalgal Growth and Nutrient Removal Efficiency in Non-Sterilised Primary Domestic Wastewater

Microalgae biomass can produce high quantities of biochemicals that can be used in various applications such as biodiesel, biogas, and aquaculture feed. The potential of sterilizing wastewater for microalgae-based wastewater treatment on a lab scale is well introduced. However, the operation cost for large-scale microalgae cultivation in wastewater treatment plants is high if using sterilising wastewater as the growth medium. The present study aimed to evaluate the growth of Scenedesmus sp., Chlorococcum aquaticum, Ankistrodesmus augustus, and Haematococcus pluvialis in non-sterilised domestic wastewater and their potential for pollutant removal in wastewater. The microalgae were cultivated in different concentrations of non-sterilised domestic wastewater, collected from a primary wastewater plant of a national sewerage company in Malaysia. Each species’ capacity for growth and the removal of pollutants were assessed. The results showed that the cell density, maximum biomass productivity, and biomass concentration of H. pluvialis, Scenedesmus sp., and C. aquaticum in 100% wastewater were significantly higher than the standard medium. Higher biomass concentration was obtained from H. pluvialis and C. aquaticum in 100% wastewater (815 g/L and 775.83 mg/L); nevertheless, Scenedesmus sp. in 100% wastewater yielded the highest specific growth rate (0.798 d−1) and the maximum biomass productivity (99.33 mg/L/day). Scenedesmus sp. in 100% wastewater also achieved better removal efficiency of total nitrogen (TN), total phosphorus (TP), and ammonia (N-NH4) with more than 90%. All tested microalgae species successfully remove nitrogen, ammonium, and phosphorus and reach the concentration limits set by the Department of the Environment, Malaysia. This study demonstrated that microalgae can grow well in non-sterilised domestic wastewater while simultaneously removing nitrogen and phosphorus effectively.

A novel integrated industrial-scale biological reactor for odor control in a sewage sludge composting facility: Performance, pollutant transformation, and bioaerosol emission mechanism

In order to remove multiple pollutants in the sewage sludge (SS) composting facility, a novel integrated industrial-scale biological reactor based on biological trickling filtration and fungal biological filtration (BTF-FBF) was developed. This study examined bioaerosol emission, odour removal, pollutant transformation mechanism, and project investment. At an inlet flow rate of 7200 m3/h, the average removal efficiencies of hydrogen sulfide (H2S), ammonia (NH3), and volatile organic compounds (VOCs) during the steady stage were 97.2 %, 98.9 %, and 92.2 %. The BTF-FBF separates microbial phases (bacteria and fungi) of different modules. BTF removed most hydrophilic compounds, while FBF removed hydrophobic ones. Moreover, the reactor could effectively remove pathogens or opportunistic pathogens bioaerosols, such as Escherichia coli (61.9%), Salmonella sp. (85%), and Aspergillus fumigatus (82.1%). The pollutant transformation mechanism of BTF-FBF was proposed. BTF-FBF annualized costs were 324,783 CNY/year at 15 years. In conclusion, BTF-FBF provides new insights into composting facility bioaerosol, odour, and pathogen emission control.

Study of Ammonia Removal Efficiency and Process Regulation Strategy of Biological Aerated Filter in Treating Low-Temperature Micropolluted Urban Landscape Water

To explore the treatment performance of a biological aerated filter (BAF) for exogenous pollutants in low-temperature landscape water, a laboratory and pilot system were constructed in urban rivers in the alpine region of northern China, and the key influencing factors such as pH, hydraulic load, air–water ratio, and temperature were studied. The results showed that the operation parameters of the BAF need to be controlled to achieve good nitrogen removal effect. Based on the hazard identification of ammonia nitrogen in landscape water effluent, the critical control points of the BAF process were determined, and corresponding control strategies were formulated. By adjusting operation parameters and other measures, hazards can be identified and overcome with reasonable accuracy. Therefore, the effluent ammonia nitrogen and concentration can be kept within the limits of the law. Double-layer aerated organisms can operate stably at normal temperature, in a transition period, and at low temperature period. The average removal rate of ammonia nitrogen in the three periods can reach 83.29%, 68.53%, and 56.55%, respectively, and the effluent quality can meet the requirements of landscape water during operation.