Ammonia Stripping Research Articles

Recovery of ammonia in anaerobic digestate using vacuum thermal stripping - acid absorption process: scale-up considerations.

A vacuum thermal stripping process coupled with acid absorption has been developed at laboratory scale to recover ammonia in anaerobic digestate. To make this ammonia recovery process scalable, this study investigated the effects of feed depth on vacuum thermal stripping in a pilot system, developed sodium hydroxide dosages required to raise feed pH for stripping, and simulated the dynamics of ammonia reduction in batch stripping tests. As feed depth was increased from 8.5 to 34.0 cm, the ammonia mass transfer coefficient and ammonia stripping efficiency decreased while the mass of stripped ammonia increased. Digested municipal sludge had a greater ammonia mass transfer coefficient than digested dairy manure at each feed depth, which could be attributed to the difference in suspended and dissolved solids concentrations. The optimum feed depth was 18 cm of the digested sludge and 14 cm of the digested manure. Sodium hydroxide dosage for the digested manure was higher than that for the digested sludge and co-digested foodwaste. The dosages were correlated to concentrations of total dissolved solids and ammonia. Total ammonia concentration decreased exponentially in batch stripping of the digested sludge at 25.5 cm deep, with a first-order stripping rate coefficient of 0.087-0.144 h-1.

Electrochemical Stripping to Recover Nitrogen from Wastewater

Electrochemical water treatment replaces chemical inputs with electricity, allowing for fine-tuning of unit processes through control of applied current and potential. These modular systems are flexible to varying degrees of centralization and robust to handle intermittent flows and shock loadings. Recovering nitrogen from separately collected urine can potentially reduce costs and energy of wastewater nitrogen removal and fertilizer production. Through benchtop experiments, we demonstrate the recovery of nitrogen from urine as ammonium sulfate using electrochemical stripping, a combination of electrodialysis and membrane stripping. Nitrogen was selectively recovered with 93% efficiency in batch experiments with real urine and required 30.6 MJ kg N–1 in continuous-flow experiments (slightly less than conventional ammonia stripping). The effects of solution chemistry on nitrogen flux, electrolytic reactions, and reactions with electro-generated oxidants were evaluated using synthetic urine solutions. Fates of urine-relevant trace organic contaminants, including electrochemical oxidation and reaction with electro-generated chlorine, were investigated with a suite of common pharmaceuticals. Trace organics (<0.1 mg L–1) and elements (<30 mg L–1) were not detected at appreciable levels in the ammonium sulfate fertilizer product. This novel approach holds promise for selective recovery of nitrogen from concentrated liquid waste streams such as source-separated urine, anaerobic digester effluent, and nitrogen-rich food waste.

Effect of iron(II) and manganese(II) on oxidation and co-precipitation of cobalt(II) in ammonia/ammonium carbonate solutions during aeration - An update and insight to cobalt losses in the Caron process for laterite ores

The Caron process involves the roasting of nickel laterite ore at 750 °C with fuel oil to produce a calcine containing Fe-Ni-Co alloy and other reacted or unreacted host minerals. The leaching of the calcine in the form of a quenched slurry in ammonia/ammonium carbonate solutions at pH ~10 and 45 °C under anaerobic and aerobic conditions sequentially dissolves alloy to iron(II), nickel(II) and cobalt(II), oxidizes iron(II), precipitates iron(III) and allows the discard of iron rich tailings after counter current decantation and steam stripping of ammonia and carbon dioxide for recycling. Oxidation of aqueous cobalt(II) during aeration in the Caron Process is one of the critical steps to reduce the incorporation of cobalt into the tailings. Cobalt(II) species which are co-precipitated with the iron phase are not able to be leached back into solution and lost to the tailings, but cobalt(III) remains in solution. Fast oxidation of cobalt(II) to cobalt(III) is expected to minimise the co-precipitation of cobalt(II) during iron precipitation, resulting in smaller losses of cobalt to tailings. Results from this study show that the oxidation of cobalt(II) species (1 g L−1) in a synthetic ammonia / ammonium carbonate (SAC) solution containing 5.3 M NH3/NH4+(total) and 1.5 M HCO3– is relatively slow at room temperature and follows first order kinetics with respect to cobalt(II) concentration. The rate of reaction is temperature dependent with an activation energy of 65.8 kJ mol−1. The presence of manganese(II) and iron(II) increases the rate of oxidation of cobalt(II) when compared to that of cobalt(II) alone. The oxidation of cobalt(II) occurs only after most of iron(II) is oxidised to iron(III) solids which facilitates the co-precipitation of cobalt(II). The variation of the concentration of manganese(II) (0.025–1.25 g L−1) in SAC solution demonstrates minimal effect on cobalt oxidation. Analysis of the solids, using XRD, show that the final solid formed in the laboratory test by the aeration of iron(II) in SAC solution consisted of goethite and ferrihydrite and that formed by the aeration of manganese(II) in SAC solution was rhodochrosite (MnCO3). While the iron oxide precipitated during the oxidation of Fe(II) and Co(II) for 1 h in the laboratory test contains 0.38% Co, the cobalt content in solids formed in aerated tanks in the Caron processing plant increases from 0.15% in Tank 1 to 0.17% in Tank 4, but in all cases too low to be detected in XRD scans.

Recent Development in Ammonia Stripping Process for Industrial Wastewater Treatment

It is noteworthy to highlight that ammonia nitrogen contamination in wastewater has been reported to pose a great threat to the environment. This conventional method of remediating ammonia nitrogen contamination in wastewater applies the packed bed tower technology. Nevertheless, this technology appears to pose several application issues. Over the years, researchers have tested various types of ammonia stripping process to overcome the shortcomings of the conventional ammonia stripping technology. Along this line, the present study highlights the recent development of ammonia stripping process for industrial wastewater treatment. In addition, this study reviews ammonia stripping application for varied types of industrial wastewater and several significant operating parameters. Furthermore, this paper discusses some issues related to the conventional ammonia stripper for industrial treatment application. Finally, this study explicates the future prospects of the ammonia stripping method. This review, hence, contributes by enhancing the ammonia stripping treatment efficiency and its application for industrial wastewater treatment.

Behaviour of doxycycline, oxytetracycline, tetracycline and flumequine during manure up-cycling for fertilizer production

The fate of four widely used veterinary antibiotics (doxycycline, flumequine, oxytetracycline and tetracycline) during manure upcycling was investigated at laboratory and pilot scale. The pilot was operated continuously, while the laboratory scale in batch mode. Both set-ups consisted of anaerobic digestion, ammonia stripping and a solid liquid separation step. A partial nitritation anammox process was used to treat the laboratory scale effluent. In the pilot installation, pig manure as feed, natural occurring antibiotics levels were reduced by 92% for doxycycline, 88% for flumequine, 95% for oxytetracycline and 100% for tetracycline. In the laboratory scale set-up, antibiotic free sludge was used and the four substances were spiked. The input antibiotics concentration was reduced by 85% for doxycycline, 46% for flumequine, 97% for oxytetracycline and 100% for tetracycline. In both set-ups the centrifuge cake was identified as the major emission pathway for residual antibiotics. Manure upcycling, while producing fertilizers, can be considered effective in reducing the residual antibiotic load.

A combination of ammonia stripping and low temperature thermal pre-treatment improves anaerobic post-digestion of the supernatant from organic fraction of municipal solid waste treatment

Municipal Solid Waste is mostly composed of organic material which is often treated in anaerobic reactors in waste treatment plants. In most cases, the obtained digestate undergoes a solid/liquid separation step, producing a liquid fraction (known as anaerobic supernatant) rich in ammonium nitrogen that has to be further treated in order to meet discharge standards. The objective of the present work was to evaluate the feasibility of anaerobic post-digestion (37 °C) of a supernatant rich in carbon and nitrogen from a municipal waste treatment plant. In order to increase the efficiency of the process, a combined pre-treatment consisting of a low-temperature thermal process (75 °C) and ammonia stripping (1.3 Lair Lsupernatant−1 min−1) was applied. The effects of pre-treatment contact time (4 and 8 h) and the hydraulic retention time (HRT) in the anaerobic reactor (20–40 d) were studied. Supernatant pre-treatment with 8-h contact time caused 13% organic matter solubilisation, thus improving methanisation by 18% when the HRT was 40 d. At the same time, ammonia stripping allowed to maintain ammonia concentration in the digester below inhibitory values (less than 100 mg N-NH3 L−1) enabling therefore high methanogenic activity (>0.23 g COD g−1 VS d−1). The final effluent characteristics (low total ammonia nitrogen and aerobically biodegradable organic matter levels) would permit implementing subsequent less energy intensive and more environmental-friendly technologies (such as partial nitritation/anammox) to comply with discharge limits.

Removal of nitrogen from chicken manure anaerobic digestion for enhanced biomethanization

The effects of side-stream ammonia stripping as a pre- and post-treatment on the anaerobic mono-digestion of chicken manure were investigated in laboratory-scale continuous stirred tank reactors. Ammonia stripping columns were operated at pH 10 but different temperatures (35, 55, 70 °C). Results showed that digestate stripping at 70 °C and pH 10 got the highest ammonia removing rate (18.2–45.2%), and under these conditions, the methane yield at OLR of 9 g VS L−1 d−1 reached 0.199 L g−1 VSadded which was significantly higher than that of other digesters (0.01–0.03 L g−1 VSadded), although no improvement of methane yield was observed at OLR 3 and 6 g VS L−1 d−1. The microbial community analysis revealed that hydrolytic and fermentative bacteria dominated all bacterial communities. Methanogenic pathway of feedstock stripping digester was predominant by hydrogenotrophic Methanimicrococcus, while hydrogenotrophic/aceticlastic Methanoscarcina was dominant in the archaeal structures of the rest digesters. However, a shift from Methanosarcina to Methanoculleus was observed in R3 (digestate stripping at 70 °C/pH 10) when dominant species were inhibited and decreased in other digesters, indicating that the high methanogenic activity in R3 was maintained by shifting to methanogens with high tolerance to inhibitors.

Recovery of ammonia from digestate as fertilizer

Abstract Ammonia inhibition can be a major problem during anaerobic digestion of manure and municipal and industrial sludges. Anaerobic digestion is sensitive to higher NH3-N concentrations, which are inhibiting and at certain levels even toxic for methanogen bacteria. During anaerobic digestion, COD and BOD are converted for 60–80% into biogas. Nitrogen will only slightly be removed due to cell synthesis and due to hydrolysis most of the Kjehldahl nitrogen is converted to ammonium. Because of the reduction of COD in anaerobic digestion the effluent of the anaerobic treatment often results in a COD/N ratio which is too low for further aerobic nitrogen removal. The Nijhuis Ammonium Recovery system (NAR) can solve this problem and removes ammonium from digestate or other substrate for digestion. The NAR is a chemical process based on stripping of ammonia. The ammonium is recovered as ammonium sulphate, which can be used as a fertilizer for agricultural purposes. The NAR was proven to be a robust technology with a stable ammonium removal efficiency of 85–90% for anaerobic digested manure, municipal and other organic waste waters. The cost effectiveness mainly depends on the concentration of NH3-N in the influent, scale of the installation, the availability of residual heat and the local value and market for ammonium sulphate. Above 2 g/l NH3-N the NAR system is competitive and at higher NH3-N concentrations more cost efficient compared to other state of the art nitrogen removal technologies and ranges between 1–3 €/kg N.

Life Cycle Assessment of Biofertilizer Production and Use Compared with Conventional Liquid Digestate Management.

Handling of digestate produced by anaerobic digestion impacts the environment through emission of greenhouse gases, reactive nitrogen, and phosphorus. Previous life cycle assessments (LCA) evaluating the extraction of nutrients from digestate using struvite precipitation and ammonia stripping did not relate synthetic fertilizer substitution (SFS) to nutrient use efficiency consequences. We applied an expanded LCA to compare the conventional management of 1 m3 of liquid digestate (LD) from food waste against the production and use of digestate biofertilizer (DBF) extracted from LD, accounting for SFS efficacy. Avoidance of CH4, N2O, and NH3 emissions from LD handling and enhanced SFS via more targeted use of nutrients in the versatile DBF product could generate environmental savings of up to 0.129 kg Sb eq, 4.16 kg SO2 eq, 1.22 kg PO4 eq, 33 kg CO2 eq, and 20.6 MJ eq per m3 LD, for abiotic resource depletion, acidification, eutrophication, global warming, and cumulative energy demand burdens, respectively. However, under worst-case assumptions, DBF extraction could increase global warming and cumulative energy demand by 7.5 kg CO2e and 251 MJ eq per m3 LD owing to processing inputs. Normalizing these results against per capita environmental loadings, we conclude that DBF extraction is environmentally beneficial.

ASSESS THE DENITRIFICATION POTENTIAL OF FERMENTED BIOSOLIDS BASED ON THEIR SPECIFIC DENITRIFICATION RATE (SDNR)

The study examined the potential of fermented and dark-fermented biosolids as external carbon sources for denitrification improvement. This was done by up-scaling the selected two (out of seven) sludge fermentation conditions from past studies, carrying out ammonia stripping pre-treatment to fix the C/N ratio, before finding their specific denitrification rate (SDNR) using SDNR experiment set-up. The gotten SDNR were then compared to the SDNR of other substances gotten from both previous studies and literature, to weight the denitrification potential of fermented biosolids as a substance. The results found that with an initial COD of 607-704 mgCOD/L, the SDNR of the two fermented biosolids and dark fermented biosolids were found to be 8.35 ± 0.41 and 8.56 ± 0.71 respectively. This was much higher than the 1.53 -2.57 for sucrose and 1.29 ± 0.21 for wastewater found in earlier study using the same methodology; and comparable to the denitrification potential value for the well-studied methanol

Exploring low-cost practical antifoaming strategies in the ammonia stripping process of anaerobic digested slurry

As excessive foam formation is undesirable from an operational perspective in the ammonia stripping process of anaerobic digested slurry, the effect of alkaline agents on foam production was first evaluated by comparing two pH adjusters (NaOH and CaO). Results show that increased pH via CaO addition can significantly aggravate foam production and restrain defoaming ability during the stripping of anaerobic digestion effluent. The addition of 0.75% normal silicone oil (NSO) or 0.01% polyether-modified silicone oil (PMSO) as antifoam reduced foam capacity by 56.2 ± 2.5% and 75.2 ± 2.7%, respectively, but only works in a slurry with pH adjusted by NaOH, not by CaO. Moreover, the addition of these antifoams led to 4.31% (0.75% NSO) and 5.38% (0.01% PMSO) NH4+-N removal efficiency abatement during the stripping process. Finally, a new high-temperature, neutral (without pH adjustment) stripping strategy is proposed in this study, because it can effectively mitigate the formation of foam and maintain equalized ammonia removal. The effluent discharged via this stripping concept can be handled easily and does not cause heavy negative impacts from the residual alkaline content. Furthermore, the ammonia loss in the preparation phase before stripping was only 1/3 that in the traditionally high-pH stripping, indicating the potential of this new mitigation strategy in the frame of an environmentally friendly development.

Nutrient Recovery from Digestate of Anaerobic Digestion of Livestock Manure: a Review

Animal manure is often anaerobically digested for the purpose of producing biogas. The digested manure, namely digestate, can be applied onto farmlands to enhance crop yields as it is abundant in nutrients. However, intensive livestock farming brings about manure exceeding the carrying capacity of lands nearby. Technologies focused on nutrient recovery from digestate have been studied recently, while many problems and challenges still remain unsolved. In this article, these recovery technologies are reviewed and compared, and challenges are deliberated. Ammonia stripping and struvite formation are easily operated technologies in comparison with membrane technologies. Amongst membrane technologies, electrodialysis reversal and forward osmosis are promising due to their high resistance to membrane fouling. Further studies should be focused on the operational cost, disposal of solid and liquid residuals and marketization of the recovered products.

Wastewater degradation by iron/copper nanoparticles and the microorganism growth rate

Nowadays, trends in wastewater treatment by zero-valent iron (ZVI) were turned to use bimetallic NZVI particles by planting another metal onto the ZVI surface to increase its reactivity. Nano size zero-valent iron/copper (NZVI/Cu0) bimetallic particles were synthesized in order to examine its toxicity effects on the wastewater microbial life, kinetics of phosphorus, ammonia stripping and the reduction of chemical oxygen demand (COD). Various concentrations of NZVI/Cu0 and operation conditions both aerobic and anaerobic were investigated and compared with pure NZVI experiment. The results showed that addition 10mg/L of NZVI/Cu0 significantly increased the numbers of bacteria colonies under anaerobic condition, conversely it inhibited bacteria activity with the presence of oxygen. Furthermore, the impact of nanoparticles on ammonia stripping and phosphorus removal was also linked to the emitted iron ions electrons. It was found that dosing high concentration of bimetallic NZVI/Cu0 has a negative effect on ammonia stripping regardless of the aeration condition. In comparison to control, dosing only 10mg/L NZVI/Cu0, the phosphorus removal increased sharply both under aerobic and anaerobic conditions, these outcomes were obtained as a result of complete dissolution of bimetallic nanoparticles which formed copper-iron oxides components that are attributed to increasing the phosphorus adsorption rate.

Electrochemical Stripping to Recover Nitrogen from Source-Separated Urine.

Recovering nitrogen from separately collected urine can potentially reduce costs and energy of wastewater nitrogen removal and fertilizer production. Through benchtop experiments, we demonstrate the recovery of nitrogen from urine as ammonium sulfate using electrochemical stripping, a combination of electrodialysis and membrane stripping. Nitrogen was selectively recovered with 93% efficiency in batch experiments with real urine and required 30.6 MJ kg N-1 in continuous-flow experiments (slightly less than conventional ammonia stripping). The effects of solution chemistry on nitrogen flux, electrolytic reactions, and reactions with electro-generated oxidants were evaluated using synthetic urine solutions. Fates of urine-relevant trace organic contaminants, including electrochemical oxidation and reaction with electro-generated chlorine, were investigated with a suite of common pharmaceuticals. Trace organics (<0.1 μg L-1) and elements (<30 μg L-1) were not detected at appreciable levels in the ammonium sulfate fertilizer product. This novel approach holds promise for selective recovery of nitrogen from concentrated liquid waste streams such as source-separated urine.

Effect of Bottom Baffles and Air Inlet Position on Mass Transfer Performance of a Water-Sparged Aerocyclone

Water-sparged Aerocyclone (WSA) is a new type of gas-liquid mass transfer equipment with a coupling field of liquid jet with gas cyclone, which can be widely used in wastewater treatment process. To further optimize the structural design of WSA, the effect of bottom baffles and air inlet position on mass transfer performance of WSA was comparatively studied by air stripping of ammonia from wastewater. The results indicated that the separation space configuration of a WSA affects its mass transfer performances. Under the same condition, the axial air inlet position has no effect on mass transfer performance, but moving air inlet position downward could reduce the gas pressure drop in WSA by about 10%, which was probably caused by abating the friction loss between the gas cyclone and the wall. In case of high air inlet velocity and low liquid flow rate, the bottom baffles in the WSA could intensify the mixing effect between gas and liquid phases, thereby improving the mass transfer performance, and the effect is more pronounced with the increase of air inlet velocity. The results could be used as a guide for the design of WSA with excellent mass transfer performance.

Integrated, multi-process approach to total nutrient recovery from stored urine

This research investigated an integrated, multi-process approach of struvite precipitation, ammonia stripping–acid absorption, and evaporation to recover NPK from stored urine.

Mitigation of nitrogen in the poultry litter to enhance biomethane production

The objective of the study is to lower the nitrogen content in the substrate to mitigate the ammonia nitrogen generated in the anaerobic digestion of poultry litter using air stripping technique. The effect of nitrogen mitigation on the biomethane yield from poultry litter was studied in batch experiments with an organic load of 8 kg for a hydraulic retention time of 21 days in mesophilic ambiance. Air stripping results indicate that the free ammonia stripping is greatly influenced by the pH of the substrate and the aeration time. It is observed that the total Kjeldahl nitrogen content in the poultry litter substrate is reduced from 6.9% to 3.69% that is about a reduction of 53%. A significant improvement in the biomethane yield was noticed for poultry litter of which nitrogen content is lowered at a pH 11. The cumulative yield for air stripped substrate increased from 8.77 L/kg to 10.66 L/kg volatile solids. The biomethane production from air stripped poultry litter shows improvement of 18% compared to the control test. From this results, it is evident that the reduction in the nitrogen content of the substrate using air stripping at high pH value is a possible option for enhancing the biomethanisation of poultry litter.

Post-treatment of biogas digestate – An evaluation of ammonium recovery, energy use and sanitation

The utilization of digestate from anaerobic digestion (AD) processes offers the possibility to recycle nutrient from organic waste materials back to the food chain. However, digestates are characterized by a high water content resulting in high storage capacities and transportation costs. Various organic wastes such as organic municipal solid waste (oMSW) require sanitation with at least one hour hydraulic retention time (HRT) at 70°C to inactivate pathogens for the safe release of the material. Consequently, the sanitation process is one of the largest energy consumers in the whole AD process chain. In this study, a post-treatment of the biogas digestate was evaluated regarding the potential for energy savings and nutrient recovery via nitrogen stripping in comparison to the conventional pre-sanitation of the organic waste. With increasing HRT (one to three hours) and aeration flow (0.0-5.3 L air per L digestate and minute) more condensate and ammonia was removed from the digestate. The total ammonia removal from the digestate after one and three hours with the highest aeration flow rate reached 42% and 80%, respectively. However, energy requirement for aeration exceeded energy savings from the lower volume for sanitation after the digestion substantially. On a system level, a positive energy balance could still be achieved by taking energy savings from the replacement of mineral fertilizer (36 GJ per ton NH4) into account. Moreover, the digestate as fertilizer could be applied in a more demand-oriented way by adding ammonium sulphate obtained by the ammonia stripping during the post-treatment.

Membrane crystallization for phosphorus recovery and ammonia stripping from reject water from sludge dewatering process

Membrane crystallization (MCr) have been applied on real wastewater to study the potential of recovering phosphorus as struvite (MgNH4PO4·H2O). The performance of MCr shows a stable flux at recovery factor of 70%. To facilitate struvite precipitation, magnesium has been added in the molar ratio of 1:1.3 of P:Mg. A recovery of 60% phosphorus have been obtained at pH of 8.3 and at recovery factor of 70%. Furthermore, the MCr process allows to produce an ammonia-rich stream on the permeate side, due to the hydrophobic nature of the membrane and the transport of volatile compounds through the membrane. This liquid stream can be considered to be used directly as a fertilizer product.

The ion-exchanger-loop-stripping process: ammonium recovery from sludge liquor using NaCl-treated clinoptilolite and simultaneous air stripping.

The technical feasibility of an ammonium recovery process ('ion-exchanger-loop-stripping') for sludge liquor from municipal wastewater treatment plants is examined. The proposed process combines ion-exchange on natural zeolites with simultaneous air stripping of ammonia to produce an industrial NOx-removal agent. Column experiments with continuously recycled NH4Cl-solutions and a real sludge liquor sample were conducted to determine basic ion-exchange kinetics of the applied clinoptilolite. Mass balances of consecutive loading/regeneration cycles show the positive influence of NaCl-pretreatment as well as simultaneous air stripping on the NH4+-exchange capacities. Removal rates for NH4+ between 61.5 and 84.6% were achieved at NH4+-concentrations typical for sludge liquor (900 to 2,300 mg L-1). Zeolite loadings ranged from 5 to 8 mg NH4+ g-1 after 90 min of loading. Regeneration rates were between 42.9 and 49.7%, but increased to 64.8% with simultaneous air stripping. A minimal decrease in the ammonium removal rate was observed as a result of matrix effects in sludge liquor (e.g. flocculants, competing ions). Liquid analyses showed a considerable phosphate-reduction in the sludge liquor sample after ion-exchange due to potential struvite or apatite precipitation. The obtained results enable a detailed design, scale-up and further optimization of the ion-exchanger-loop-stripping process in future.