Ammonia Stripping Research Articles

Post-hydrolysis ammonia stripping as a new approach to enhance the two-stage anaerobic digestion of poultry manure: Optimization and statistical modelling

Post-hydrolysis ammonia stripping was investigated as a new approach to enhance the methane potential of high ammonia substrates, such as poultry manure. The objective of the proposed approach is to address some of the noticeable disadvantages in the existing ammonia-stripping techniques i.e., treatment of raw samples and side-stream stripping. Poultry manure (PM) and a co-substrate (mixed wastes from a cheese factory and a coffee house, referred to as MS) characterized by a high carbon-to-nitrogen ratio were mixed at five different ratios: PM:MS of 100:0, 75:25, 50:50, 25:75, and 0:100. Samples were hydrolyzed for six days to promote ammonia conversion from organic nitrogen and then the samples with higher ammonia levels (>2000 mg NH3–N/L) were stripped with air at initial pH values of 9 and 10 and temperatures of 40 and 55 °C. Biochemical methane potential (BMP) test results showed that post-hydrolysis ammonia stripping had alleviated ammonia inhibition and improved methane potential up to 200% when compared with untreated samples. The ammonia removal efficiency was mostly affected by pH. On the other hand, methane potential was highest in the samples treated at a higher temperature as their biodegradability was enhanced when compared with the samples treated at lower temperatures. Post-BMP characterization showed that the proposed approach had also limited the increase of ammonia in the digestate which ensured proper growth of methanogenic microorganisms.

Efficient treatment of aged landfill leachate containing high ammonia nitrogen concentration using dynamic wave stripping: Insights into influencing factors and kinetic mechanism

Aged landfill leachate is challenging to treat owing to its extremely high ammonia concentration and poor biodegradability. We constructed pilot-scale dynamic wave stripping equipment to separate ammonia from landfill leachate and achieved excellent results. To further expand the usage of pilot-scale equipment in actual water treatment process and implement it in a sewage plant, we established the mass transfer kinetic physics and mathematical model of the dynamic wave stripping process based on the surface renewal theory and the traditional stripping method. The surface renewal theory and the traditional stripping method are employed to analyze the mechanism of various experimental parameters affecting the stripping process, predict the stripping effect of the equipment under different conditions, and verify the calculation results of the model using the kinetic fitting results of the experimental data. These calculation results of the model indicate that the mass transfer kinetic coefficients of ammonia stripping at 20 °C, 25 °C, and 30 °C are 85.62 min, 75.34 min, and 65.88 min, respectively, when the gas–liquid ratio is 129. When the gas–liquid ratios are 62, 129, and 163 at 25 °C, the mass transfer kinetic coefficients of ammonia stripping are 102.61 min, 75.34 min, and 61.43 min, respectively. With increasing temperature and gas–liquid ratio, the particle size and number of bubbles in the wave tube of the stripping equipment gradually decrease and the mass transfer efficiency of free ammonia between the gas and liquid phases improves, enhancing the stripping efficiency of ammonia nitrogen.

Lab‐scale data and microbial community structure suggest shortcut nitrogen removal as the predominant nitrogen removal mechanism in post‐aerobic digestion (PAD)

Implementing an aerobic digestion step after anaerobic digestion, referred to as "post aerobic digestion" (PAD), can remove ammonia without the need for an external carbon source and destroy volatile solids. While this process has been documented at the lab-scale and full-scale, the mechanism for N removal and the corresponding microbial community that carries out this process have not been established. This research gap is important to fill because the nitrogen removal pathway has implications on aeration requirements and carbon demand, that is, short-cut N-removal requires less oxygen and carbon than simultaneous nitrification-denitrification. The aims of this research were to (i) determine if nitrite (NO2 - ) or nitrate (NO3 - ) dominates following ammonia removal and (ii) characterize the microbial community from PAD reactors. Here, lab-scale PAD reactors were seeded with biomass from two different full-scale PAD reactors. The lab-scale reactors were fed with biomass from full-scale reactors and operated in batch mode to quantify nitrogen species concentrations (ammonia, NH4 + , NO2 - , and NO3 - ) over time. Experimental results revealed that NO2 - production rates were several orders of magnitude greater than NO3 - production rates. Indeed, nitrite accumulation rate (NAR) was greater than 90% at most temperatures, confirming that shortcut nitrogen removal was the dominant NH4 + removal mechanism in PAD. Microbial community analysis via 16S rRNA sequencing indicated that ammonia oxidizing bacteria (AOB) were much more abundant than nitrite oxidizing bacteria (NOB). Overall, this study suggests that aeration requirements for post-aerobic digestion should be based on NO2 - shunt and not complete simultaneous nitrification denitrification. PRACTITIONER POINTS: AOB are a key feature of PAD microbial communities NOB are present, but in much lower abundance than AOB High nitrite accumulation ratio suggests shortcut nitrite as the main mechanism for nitrogen removal Nitritation in PAD reactors is sustained at temperatures as high as 40°C No ammonia oxidation occurred at 50°C implying different mechanisms of nitrogen removal including ammonia stripping.

Comparative Assessment of Nitrogen Concentration Effect on Microalgal Growth and Biochemical Characteristics of Two Chlorella Strains Cultivated in Digestate.

Microalgae have been recently recognized as a promising alternative for the effective treatment of anaerobic digestion effluents. However, to date, a widely applied microalgae-based process is still absent, due to several constraints mainly attributed to high ammonia concentrations and turbidity, both hindering microalgal growth. Within this scope, the purpose of the present study was to investigate the performance of two Chlorella strains, SAG 211-11b and a local Algerian isolate, under different nitrogen levels, upon ammonia stripping. The experiments were performed on cylindrical photobioreactors under controlled pH (7.8 ± 0.2) and temperature (25 ± 2 °C). Cultures were monitored for biomass production and substrate consumption. After sampling at the beginning of the stationary phase of growth (12th day) and after the maturation of the cells (24th day), an analysis of the produced biomass was conducted, in terms of its biochemical components. The local isolate grew better than C. vulgaris 211-11b, resulting in 1.43 mg L−1 biomass compared to 1.02 mg L−1 under 25 mg NH4-N L−1, while organic carbon and nutrient consumption varied between the two strains and different conditions. Concerning biomass quality, a high initial NH4-N concentration led to high protein content, while low nitrogen levels favored fatty acid (FA) accumulation, though the production of pigments was inhibited. In particular, the protein content of the final biomass was determined close to 45% of the dry weight in all experimental scenarios with adequate nitrogen, while proteins decreased, and the fatty acids approached 20% in the case of the local isolate grown on the substrate with the lowest initial ammonium nitrogen (25 mg NH4-N L−1). The novelty of the present work lies in the comparison of a microalga with industrial applications against a local isolate of the same species, which may prove to be even more robust and profitable.

Nutrient removal and recovery from wastewater by microbial fuel cell-based systems - A review.

Microbial fuel cell (MFC) is a green innovative technology that can be employed for nutrient removal/recovery as well as for energy production from wastewater. This paper summarizes the recent advances in the use of MFCs for nutrient removal/recovery. Different configurations of MFCs used for nutrient removal are first described. Different types of nutrient removal/recovery mechanisms such as precipitation, biological uptake by microalgae, nitrification, denitrification and ammonia stripping occurring in MFCs are discussed. Recovery of nutrients as struvite or cattiite by precipitation, as microalgal biomass and as ammonium salts are common. This review shows that while higher nutrient removal/recovery is possible with MFCs and their modifications compared to other techniques as indicated by many laboratory studies, field-scale studies and optimization of operational parameters are needed to develop efficient MFCs for nutrient removal and recovery and electricity generation from different types of wastewaters.

Nitrogen recovery from anaerobic digestate via ammonia stripping and absorbing with a nitrified solution

Anaerobic digesters produce renewable energy from organic wastes, including animal wastes. However, ammonia toxicity stemming from the nitrogen content of animal wastes reduces the feasibility of the process. Approaches for stripping ammonia and recovering it via the use of strong mineral acids have disadvantages. Here, we evaluate a process that includes ammonia removal coupled with a novel nitrogen recovery strategy using a solution from biological nitrification. This approach has the potential to reduce ammonia toxicity while providing valuable biofertilizer from nitrification. Since this integrated process couples sub-systems that have different operating conditions, an experimental laboratory-scale study and Aspen Plus model of the nitrogen removal and recovery system (consisting of stripping and absorption units) were used to assess process performance as a function of stripping unit temperature and feed pH, as well as of the absorption unit feed pH and nitrogen concentrations. Based on results of the experiments and modeling, the recommended conditions for the integrated stripper-absorber system were a feed pH of 10 and operating temperature of 50 °C for the stripping unit, and a feed pH of 7 and feed nitrogen concentrations of 7 g-N/L for the absorption unit. While the feed pH and temperature had a large impact on ammonia stripping, neither the feed pH nor the nitrogen concentration in the feed led to a significant difference in the ammonia absorption. These results support the use of this new approach of using nitrified solution as the ammonia absorbent in an integrated anaerobic digestion process.

Design, Implementation and Simulation of a Small-Scale Biorefinery Model

Second-generation biomass is an underexploited resource, which can lead to valuable products in a circular economy. Available locally as food waste, gardening and pruning waste or agricultural waste, second-generation biomass can be processed into high-valued products through a flexi-feed small-scale biorefinery. The flexi-feed and the use of local biomass ensure the continuous availability of feedstock at low logistic costs. However, the viability and sustainability of the biorefinery must be ensured by the design and optimal operation. While the design depends on the available feedstock and the desired products, the optimisation requires the availability of a mathematical model of the biorefinery. This paper details the design and modelling of a small-scale biorefinery in view of its optimisation at a later stage. The proposed biorefinery comprises the following processes: steam refining, anaerobic digestion, ammonia stripping and composting. The models’ integration and the overall biorefinery operation are emphasised. The simulation results assess the potential of the real biowaste collected in a commune in Flanders (Belgium) to produce oligosaccharides, lignin, fibres, biogas, fertiliser and compost. This represents a baseline scenario, which can be subsequently employed in the evaluation of optimised solutions. The outlined approach leads to better feedstocks utilisation and product diversification, raising awareness on the impact and importance of small-scale biorefineries at a commune level.

Recovery of nitrogen and phosphorus from livestock slurry with treatment technologies: A meta-analysis

The livestock industry has developed rapidly in recent decades, but the improper treatment of livestock manure, especially slurry, causes environmental pollution. Treatment technologies are considered to be effective in alleviating nitrogen (N) and phosphorus (P) losses from livestock slurry. Here, we used published research data to conduct a meta-analysis of the recovery efficiencies of N and P of five mainstream treatment technologies, including ammonia stripping, air scrubbing, membrane filtration, microalgae cultivation and struvite crystallization. Additionally, the agronomic effects of the recovered products of these treatment technologies were evaluated. The results showed that all technologies exhibited clear recovery effects on N and P. The N recovery efficiencies ranged from 57% to 86%, and those of P ranged from 64% to 87%. Struvite crystallization was the most efficient treatment technology for both N and P recovery; moreover, the ammonia stripping and microalgae cultivation technologies were less efficient. The pH levels and temperatures are the main factors that influence ammonia stripping, struvite crystallization and microalgae cultivation, while membrane filtration and air scrubbing are mainly affected by the membrane types and properties. When the equal amount of N or P input to fields, the recovered products (ammonium sulfate and struvite crystals) may achieve a similar crop yield, relative to commercial N or P fertilizers. Our findings can provide deep suggestions and parameters for designing proper treatment technologies to reduce nutrient discharge from livestock slurry in regions with high livestock density and also for identifying the research gaps that should be paid more attention in the future.

Nutrient recovery from wastewater: A review on the integrated Physicochemical technologies of ammonia stripping, adsorption and struvite precipitation

• A review on technical integration for N-P-K recovery was performed. • “Stripping → K-struvite precipitation” can recover N, P and K simultaneously. • Crystal size should be enlarged for upscaling “stripping + struvite precipitation”. • (Modified-)biochar/zeolite have been used as the seed of struvite or adsorbent. • Adsorbent could replace sulfuric acid in acid scrubber following stripping column. The field of wastewater management has seen a transition from “contaminant removal” in wastewater treatment plants (WWTPs) to “nutrient recovery” in so-called water resource recovery facilities (WRRFs) for years. For achieving a higher efficiency and economic benefits, the integration of multiple nutrient recovery technologies (NRTs) is of increased interest. This study provides a comprehensive overview of the integration of ammonia stripping, adsorption and struvite precipitation, three of the most dominant physicochemical NRTs. In their different combinations, a critical comparison of the available research is given from the perspective of process technical description, the current scale of application and potential challenges and perspectives ahead. The integration between ammonia stripping and struvite precipitation has been applied in either “one single integrated reactor” at lab scale or “multiple discrete reactors” at pilot/full scale. The collection of struvite should be further optimized, and “stripping → K-struvite precipitation” is expected to recover all of three macronutrients. In the technical integration between struvite precipitation and adsorption, small pristine adsorbents (<50 μm) have been used as the seeding material for struvite, while pristine and surface-modified adsorbents have been integrated with struvite precipitation as the sorbent material. Some magnesium-modified adsorbents achieved a higher removal efficiency and adsorption capacity than pristine adsorbent. The non-preferential adsorption is one of the main challenges limiting its upscaling. Lastly, stripping has been applied in the regeneration process of zeolite. Its economic benefits should be further analysed before its upscaling. This review proposed to apply adsorbents as the alternative of sulfuric acid in the acid scrubber following the stripping column. This new perspective may decrease the cost on ammonia stripping.

PLS-based soft-sensor to predict ammonium concentration evolution in hollow fibre membrane contactors for nitrogen recovery

Hollow fibre membrane contactors (HFMC) have emerged as a promising technology for nitrogen-recovery that can be implemented in wastewater treatment plants (WWTPs) to promote circular economy. In this process, a hydrophobic membrane allows the transference of free-ammonia across the hollow fibres. During its operation, the ammonium concentration decreases, and real-time measurements would be of great value for process monitoring, optimization and control. Ammonium probes exist, but they are expensive and present noticeably maintenance costs. In this work, results from eight N-recovery experiments performed at different pH values using real supernatant of a full-scale anaerobic digester were analysed in terms of the time-evolution profiles of pH and total ammonium nitrogen (TAN). The pH revealed to carry relevant information related to the TAN concentration, as it decreased in the feed solution due to free ammonia stripping. The pH is an inexpensive-to-measure process variable that can be routinely acquired in any WWTP. Therefore, a data-driven soft-sensor has been developed. It uses the pH, its derivative, and the pH increments after each reagent dosing as input signals, to estimate the TAN concentration via PLS. An extended PLS-model incorporating interaction terms, quadratic and cubic forms of the three input variables improved the TAN concentration estimation. The developed soft-sensor was able to accurately reproduce the evolution of TAN concentration (in the range 0–1000 mgNH4+-N/L with R2 > 0.97 and RMSE <40 mg/L) during the HFMC process operation, thus making it possible to monitor the process as well as enabling future development of different control and optimization strategies.

Transforming wastewater ammonia to carbon free energy: Integrating fuel cell technology with ammonia stripping for direct power production

The transformation of ammonia from pollutant to energy rich carbon free fuel presents an opportunity for the transition of wastewater services to net zero. However, there is only limited knowledge of how the product quality of ammonia recovered from real wastewater might impact on its downstream exploitation in fuel cells. This study therefore exploited vacuum stripping to produce an aqueous ammonia concentrate from real wastewater that was then evaluated within a direct ammonia fuel cell, as a reference technology for energy generation. A 17 g L−1 aqueous ammonia product was created by vacuum stripping centrate from a full-scale anaerobic digester (2 gN L−1). The pH of the product was lower than expected due to the mild-acidification of solution by the co-transport of low MW volatile organic compounds. This reduced power density in the fuel cell, due to the incomplete deprotonation of ammonia (lowering oxidation potential at the fuel cell anode) and a decrease in [OH–] which is required for complete electrochemical conversion. We propose that improved vacuum stripping design can increase the distillate ammonia concentration and produce a more alkaline product, yielding markedly higher fuel cell power density by enhancing ammonia oxidation at the anode (through concentration and deprotonation) and reducing [OH–] mass transfer limitations. As the separation energy for ammonia is dominated by the latent heat demand of water vapour, a synergy exists between creation of a concentrated ammonia product (that improves power density) and reducing the energy demand for separation. The energy balance from this research evidences that despite the high latent heat demand for separation, the low cost of heat coupled with the power produced from ammonia yield a favourable economic return when compared to conventional biological treatment. This study also identifies that revaluing ammonia as a carbon free fuel can help reposition wastewater treatment for a zero-carbon future.

Exploring Different Pretreatment Methodologies for Allowing Microalgae Growth in Undiluted Piggery Wastewater

The overapplication of manure on agricultural soils leads to nitrogen and phosphorus discharge into the aquatic environment, resulting in serious eutrophication problems and decreased water quality. Piggery wastewater (PWW) can be treated by microalgae to recycle nutrients, but the toxic levels of ammonia and organic matter hinder their growth. Fresh water is usually used to dilute PWW, but it is a scarce resource. The implementation of a pretreatment step before microalgae-based treatment could make PWW suitable for microalgae growth. Electrocoagulation, ammonia stripping, photo-Fenton, and constructed wetlands were evaluated as pretreatment methods to reduce ammonia, chemical oxygen demand (COD), color, and total suspended solids. Moreover, the pretreated PWWs were tested to grow the microalga Tetradesmus obliquus. Photo-Fenton showed the best results among the other pretreatments, achieving removal efficiencies above 90%, except for ammonia. This resulted in T. obliquus being capable of growing on undiluted PWW, even at higher ammonia levels, achieving similar biomass productivity to synthetic medium (66.4 ± 17.8 mg·L−1·day−1 and 60.1 ± 10.4 mg·L−1·day−1, respectively) almost doubling with pH control (116.5 mg·L−1·day−1). Thus, this pretreatment seems to be the most promising one to incorporate into microalgae-based treatment systems and must be further explored.

Nitrogen Recovery from Anaerobic Digestate Via Ammonia Stripping and Absorbing with a Nitrified Solution

Nitrogen Recovery from Anaerobic Digestate Via Ammonia Stripping and Absorbing with a Nitrified Solution

N, P, K Recovery from Hydrolysed Urine by Na-Chabazite Adsorption Integrated with Ammonia Stripping and (K-)Struvite Precipitation

N, P, K Recovery from Hydrolysed Urine by Na-Chabazite Adsorption Integrated with Ammonia Stripping and (K-)Struvite Precipitation

Air stripping of ammonia using a gas-liquid contactor: Effect of pH, temperature, airflow rate, and initial ammonia concentration

Air stripping of ammonia using a gas-liquid contactor: Effect of pH, temperature, airflow rate, and initial ammonia concentration

Post-Hydrolysis Ammonia Stripping as a New Approach to Enhancing the Two-Stage Anaerobic Digestion of Poultry Manure: Optimization and Statistical Modeling

Post-Hydrolysis Ammonia Stripping as a New Approach to Enhancing the Two-Stage Anaerobic Digestion of Poultry Manure: Optimization and Statistical Modeling

Solid and Soluble Organic Compounds Changes During Thermophilic Aerobic Digestion of Sewage Sludge

Over the past decade, thermophilic aerobic digestion (TAD) has been considered a practical approach to treating highstrength wastewater because of its several advantages. In this study, batch-mode TAD of sewage sludge was conducted using a lab-scale bioreactor to evaluate the changes in solid and soluble organic compounds. The TAD process achieved rapid degradation of the solid compound at 55oC. The removal efficiency of volatile suspended solids (VSS) increased rapidly at the early operation stage and achieved 25% at 48 h. Then, the VSS removal efficiency increased gradually up to approximately 40% at the end of the digestion (168 h). As a result of VSS degradation, the soluble chemical oxygen demand (SCOD) increased significantly up to 12 g/L at 36 h and then showed a slow decline pattern. Furthermore, the pattern of protease activity was similar to that of the SCOD. This result indicates that the rapid degradation of VSS is highly linked to the increase of protease activity and thermophilic conditions. This study used acetic acid and propionic acid. The variation patterns were similar under both acetic acid and propionic acid. The concentrations of acetic acid and propionic acid rapidly increased up to 3.05 g COD/L at 48 h and 2.51 g COD/L at 36 h, respectively. Then, major volatile fatty acids concentrations declined sharply and became undetectable after 144 h. Similar to the SCOD variation pattern, the soluble total nitrogen and NH4+-N also decreased sharply after 72 h. This might be because ammonia stripping is enhanced by pH rising and continuous aeration during the TAD.

Exploiting the Nutrient Potential of Anaerobically Digested Sewage Sludge: A Review

The world is currently witnessing a rapid increase in sewage sludge (SS) production, due to the increased demand for wastewater treatment. Therefore, SS management is crucial for the economic and environmental sustainability of wastewater treatment plants. The recovery of nutrients from SS has been identified as a fundamental step to enable the transition from a linear to a circular economy, turning SS into an economic and sustainable source of materials. SS is often treated via anaerobic digestion, to pursue energy recovery via biogas generation. Anaerobically digested sewage sludge (ADS) is a valuable source of organic matter and nutrients, and significant advances have been made in recent years in methods and technologies for nutrient recovery from ADS. The purpose of this study is to provide a comprehensive overview, describing the advantages and drawbacks of the available and emerging technologies for recovery of nitrogen (N), phosphorus (P), and potassium (K) from ADS. This work critically reviews the established and novel technologies, which are classified by their ability to recover a specific nutrient (ammonia stripping) or to allow the simultaneous recovery of multiple elements (struvite precipitation, ion exchange, membrane technologies, and thermal treatments). This study compares the described technologies in terms of nutrient recovery efficiency, capital, and operational costs, as well as their feasibility for full-scale application, revealing the current state of the art and future perspectives on this topic.

Model-based identification of biological and pH gradient driven removal pathways of total ammonia nitrogen in single-chamber microbial fuel cells

Experimental data that allow for a precise identification of the total ammonia nitrogen (TAN) elimination pathways in single-chamber microbial fuel cells (SC-MFCs) are still very rare. However, nitrification–denitrification and ammonia volatilization are commonly reported as the two main removal mechanisms. This work presents a mathematical model to quantify the contribution of volatilization to TAN removal in SC-MFCs. For model verification, three different experimental settings were performed with TAN concentrations of 57 to 111mgNL−1: (i) biotic tests using sealed cathode chambers with variable oxygen supply, (ii) biotic tests for determination of the pH gradient within the cathodic microenvironment and (iii) pH-induced abiotic gas release tests. In biotic tests, the TAN removal rate in closed-circuit was 29–37% higher compared to open-circuit mode, which indicated additional electrochemical conservation processes. A limitation of oxygen availability on the air-facing side of the cathode (0.1%) resulted in negligible TAN removal rates. In contrast, an atmospheric oxygen content of 21% increased the biological oxidation rate of TAN to 653–730mgNm−2Catd−1and the electrochemical ammonia stripping rate to 210–241mgNm−2Catd−1 at 22 °C. During electricity generation, a peak pH value of 9.6 was measured by microelectrode measurements, which might lead to free ammonia nitrogen concentrations of 39–40mgFANL−1 nearby the cathode surface. Based on the proposed model and assuming an inhibition of ammonium-oxidizing bacteria, a maximum TAN removal rate via ammonia volatilization of 785mgNm−2Catd−1 (T = 22 °C) at a current density of 322 mA m−2Cat is estimated.

Treatment of hydrothermal liquefaction wastewater with ultrafiltration and air stripping for oil and particle removal and ammonia recovery

This study aims to evaluate the application of ultrafiltration technology for the separation of particles and oil droplets and the recovery of ammonia from hydrothermal liquefaction (HTL) wastewater. Real HTL wastewater from the hydrothermal liquefaction of municipal sewage sludge was used in this study. Experiments were carried out using a submerged polyethersulfone ultrafiltration membrane with molecular weight cutoff of 100 kDa in combination with air stripping and addition to acid and base traps for recovery of volatiles. Results showed, that the best operation mode of ultrafiltration is with backwash cycles of the permeate, maintaining a flux lower than the critical flux of 6 L/h·m2. The setup led to fast stripping of ammonia, which was successfully recovered by 88% in the acid trap. This application can be considered an adequate first stage treatment of the HTL wastewater. The importance of this work is that it proves that membrane technology can be successful in treating complex real HTL wastewater, and is not only limited for applications using model solutions.