Air Stripping Research Articles

Ammonia removal mechanism by the combination of air stripping and ultrasound as the function of pH

Ammonia removal mechanism by the combination of airstripping and ultrasound (AU) as the function of pH was investigated. The synergistic effects were observed for air stripping and ultrasound, which was obviously enhanced with the decrease in pH. Ammonia degradation and ammonia stripping were the ammonia removal pathways by AU. Ammonia degradation was the main ammonia removal pathway at the pH of lower than 8, but at a higher pH, ammonia stripping was the main pathway. Air stripping strengthens ammonia degradation by ultrasound in two ways of providing reactive radicals and more cavitation bubbles for pyrolysis. Ammonia degradation depended on the oxidation of radicals at a pH of lower than 8 and did on pyrolysis at a higher pH. Ultrasound also strengthens ammonia stripping by increasing mass transfer coefficient and accelerating the shift of the equilibrium of free ammonia and ammonium ions, which resulted in more strongly strengthening effect at a lower pH.

Treatment of By-Products Generated from Anaerobic Digestion of Municipal Solid Waste

PurposeThis study aimed to examine the possibilities of the treatment of the by-products generated in the anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW): oxygen stabilization (composting) of the solid digestate and pretreatment with air stripping of the effluents (liquid digestate and leachate from maturation field and reactors from composting).MethodsOxygen stabilization (OS) was performed in full-scale in a mechanical–biological treatment (MBT) plant using three different methods, using an open field or enclosed box reactor with aeration. The ammonia stripping was performed in a pilot-scale installation using effluents from AD (liquid digestate) and OS (leachate from maturation field and reactors).ResultsThe lowest self-heating possibility after the OS was recorded at 28.5 °C, which proves that the most stabilized was the sample after processing with structuring material addition. Due to air stripping, the highest efficiency of ammonium ions removal was noted at the level of 50.6%, with an initial pH value of 10.5, after 12 h. Among the examined factors pH value was found to be significant [the determination coefficient (R2) of 0.93].ConclusionsThe oxygen stabilization of the digestate requires the structuring material addition before being placed in the reactor with aeration. The inert fraction from the ballistic separation of the OFMSW can be an interesting solution, as required structuring material. Air stripping as the effluents pre-treatment step can meet the MBT plants expectations.Graphic

Ammonium recovery from model solutions and sludge liquor with a combined ion exchange and air stripping process

The recovery of ammonium (NH4+) from model (NH4)2SO4 solutions as well as from sludge liquor of a communal waste water treatment plant was studied on the laboratory scale using the ion exchanger loop stripping process (ILS). The ILS process combines ion exchange and air stripping in a hybrid process and works with fixed bed columns containing natural zeolite (mainly clinoptilolite), which is alternately loaded and regenerated. The sodium hydroxide (NaOH) regeneration fluid is simultaneously air stripped. Ammonium is recovered in a subsequent acid scrubber as concentrated ammonium sulfate solution, which is a suitable reducing agent for industrial NOx recovery. Lab scale experiments with four loading and regeneration cycles demonstrate the technical feasibility of the process. The ammonium equilibrium increased after the first loading and regeneration cycles and ammonium uptake reached concentrations of 3 to 4 mg NH4+ L−1 over four consecutive cycles. NaOH regeneration at pH values >11.5 recovered nearly the total amount of previously adsorbed ammonium. The stripped amount of NH4+ increased over the investigated cycles and in the final regeneration sequence approximately the whole amount of desorbed ammonium was simultaneously stripped. Ammonium exchange and recovery characteristics did not significantly change when real sludge liquor samples were used.

Pilot‐scale experimental studies on ethanol purification by cyclic stripping

AbstractCyclic distillation is a proven process intensification method for enhanced separation of various mixtures. It uses an alternative operating mode based on separate phase movement which leads to important practical advantages (vs conventional mode) such as increased column throughput, lower equipment cost (using much less trays at the same reflux ratio) and reduced energy requirements by 20–35% (smaller reflux ratio at the same number of stages), and better separation performance (up to three times). However, if the impurities to be separated are in very low amounts in the feed then distillation is not favorable from an energy use viewpoint. This article is the first to report the practical performance of a continuous process for ethanol purification by air stripping using a cyclic mode of operation, a novel process that avoids the costs of distillation. The purification of ethanol food grade (96.4 vol%) from volatile impurities (0.5 vol%) such as esters, aldehydes, and alcohols, is carried out in a hydro‐selective column with five stages. The lightweight impurities are removed from a stream that is the head fraction of a distillation column. This is usually a waste stream amounting to 3–6% of the plant production rate. By concentrating the stream with impurities, more ethanol is produced such that the losses are reduced to only 1–1.5% of the plant capacity. Based on the experimental results presented in this work, a process consisting of two air stripping columns using cyclic operation is proposed for industrial implementation.

Two-stage air stripping combined with hydrolysis acidification process for coal gasification wastewater pretreatment.

Coal gasification wastewater is mainly from gas washing, condensation and purification processes in the gas furnace with high NH3-N (nitrogen in water in the form of free ammonia (NH3) and ammonium ion (NH4 +)), TN (total nitrogen) and refractory organics content, which will inhibit the subsequent biological treatment. The 'air stripping - hydrolysis acidification - air stripping' process was proposed as the pretreatment for coal gasification wastewater to improve the biodegradability and nitrogen removal, which could reduce the subsequent biological treatment load. The first-stage air stripping process before hydrolysis acidification could achieve a significant removal of NH3-N (97.0%) and volatile phenol (70.0%), reducing the corresponding toxicity on hydrolysis acidification. The group with air stripping had more abundant microbial communities and a more effective organic degradation performance in hydrolysis acidification than that without air stripping. The second-stage air stripping removed NH3-N released from hydrolysis acidification, and significantly reduced the TN concentration in effluent. The whole process achieved a TN removal from 2,000 ± 100 mg/L to 160 ± 80 mg/L, and a total phenols removal from 700 ± 50 mg/L to 80 ±20 mg/L.

Air stripping for drinking water

Drinking water tends to be relatively clean compared with water for other uses, but it sometimes contains contaminants. Air stripping, a water treatment technology primarily used for groundwater remediation, is now gaining traction within the drinking water treatment industry.

Evaluation of different solvent performance in a 0.7 MWe pilot scale CO2 capture unit

Novel concepts for post-combustion CO2 capture have been demonstrated in a 0.7MWe pilot-scale facility installed at Kentucky Utilities (KU) E.W. Brown Generating Station. The process which includes two-staged solvent stripping used a secondary air stripper to provide leaner regenerated solvents, and recycled CO2 to boiler to boost inlet CO2 concentrations to the absorber for enhanced mass transfer and increased solvent capacity. The effectiveness of the secondary stripper together with other aspects of the heat-integrated process and the associated energy savings have been demonstrated from solvent campaigns with 30wt% monoethanolamine (MEA) and other advanced solvents. Comparative analysis between advanced solvents showed that intercooling in the absorber had a more significant impact on the performance of the solvent with known high CO2 partial pressure as a result of the corresponding low heat of reaction with relative higher bicarbonate content from its reaction with CO2. The energy of regeneration of this solvent was lower than MEA at similar test conditions.

Enhanced biogasification from ammonia-rich swine manure pretreated by ammonia fermentation and air stripping

Anaerobic digestion (AD) is widely applied for efficient energy recovery from livestock manure. However, due to its high ammonia concentration and the resultant inhibition to methanogens, dry AD of livestock manure is difficult to achieve high efficiency of energy recovery. In this study, ammonia fermentation and air stripping were attempted as pretreatments to remove and recover ammonia, targeting enhanced dry AD of ammonia-rich swine manure. The effect of manure pH on ammonia stripping was specifically investigated under high solids condition and then on the subsequent dry AD. In order to remove and recover more nitrogen from manure, ammonia fermentation was conducted to release ammonia before air stripping. Results indicated that 90% and 85% of ammonia removal from the ammonia fermented manure (with ammonia nitrogen content of 17–18 g for per kilogram of total solids (TS)) could be obtained after being stripped at pH10.2 and pH8.8, respectively. Moreover, the biogas production from the subsequent dry AD of ammonia-stripped swine manure was about 1.6–1.7 times higher than that from the raw manure (27.5 ml for per gram of volatile solids (VS)). This study implies that ammonia fermentation followed by air stripping is a prospective solution for ammonia removal and recovery from livestock manure and then enhanced dry AD.

Combination of air stripping and biological processes for landfill leachate treatment

Combination of air stripping and biological processes for landfill leachate treatment

Ammonia-Rich Solution Production from Wastewaters Using Chemical-Free Flow-Electrode Capacitive Deionization

Conventional technologies for ammonia recovery from wastewaters are based on ammonia enrichment/separation methods (i.e., electrochemical stripping, air stripping and ion exchange) followed by acid...

Removal of ammonia from a smelting wastewater by cyclic stripping and acid adsorption: Kinetics study

Air stripping is an effective method for the removal of ammonia from high‐concentration wastewater. The traditional open stripping process is expensive due to high consumptions of alkali reagent and energy. This study proposed a novel cyclic stripping‐acid adsorption system for ammonia removal. The stripped ammonia gas flowed into the stripping tower, and no fresh air was added during the cyclic stripping process. The kinetics model of ammonia removal from the smelting wastewater in a pilot‐scale cyclic stripping tower was investigated. The influences of stripping temperature (T), wastewater pH, air to liquid ratio (R), and acid spray flow (F) on the ammonia removal rate were discussed. The kinetics equation was determined as G = 4.14 × 10−3 × pH1.83 × T0.27 × F0.98 × R−0.49 when pH = 9.80–12.29, T = 19–35°C, F = 58–76 m3·h−1, and R = 1329–1725. The equation can be used to predict the removal rate of ammonia during operation. The ammonia concentration of the effluent decreased from 5951 mg·L−1 to 13 mg·L−1 within 15 h. Ammonia can be removed rapidly and economically from wastewater via the cyclic stripping process. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13146, 2019

Nutrient removal from digested swine wastewater by combining ammonia stripping with struvite precipitation.

Typical biological processing is often challenging for removing ammonia nitrogen and phosphate from swine wastewater due to inhibition of high ammonia on activity of microorganisms, exhaustion of time, and low efficiency. In this study, a physicochemical process by combining ammonia stripping with struvite precipitation has been tested to simultaneously remove ammonia nitrogen, phosphate, and chemical oxygen demand (COD) from digested swine wastewater (DSW) with high efficiency, low cost, and environmental friendliness. The pH, temperature, and magnesium content of DSW are the key factors for ammonia removal and phosphate recovery through combining stripping with struvite precipitation. MgO was used as the struvite precipitant for NH4+ and PO43- and as the pH adjusted for air stripping of residual ammonia under the condition of 40°C and 0.48m3h-1L-1 aeration rate for 3h. The results showed that the removal efficiency of ammonia, total phosphate, and COD from DSW significantly increased with increase of MgO dosage due to synergistic action of ammonia stripping and struvite precipitation. Considering the processing cost and national discharge standard for DSW, 0.75gL-1 MgO dosage was recommended using the combining technology for nutrient removal from DSW. In addition, 88.03% NH4+-N and 96.07% TP could be recovered from DSW by adsorption of phosphoric acid and precipitation of magnesium ammonium phosphate (MAP). The combined technology could effectively remove and recover the nutrients from DSW to achieve environmental protection and sustainable and renewable resource of DSW. An economic analysis showed that the combining technology for nutrient removal from DSW was feasible.

Sustainable treatment of municipal landfill leachate by combined association of air stripping, Fenton oxidation, and enhanced coagulation.

The present world has been facing the problem of municipal solid waste disposal with the generation of highly complex and toxic landfill leachate. Thus, in this research work, treatability of landfill leachate had been investigated by the combined approach of air stripping, Fenton oxidation, and enhanced coagulation to comply with discharge standard. At the initial stage of treatment, air stripping of raw leachate was implemented which removes around 51.50% of COD, 74.60% of BOD5, and 97.60% of NH3-N within 36h of optimum retention time. Following air stripping, Fenton oxidation was applied with an optimum molar ratio of 1.9 of H2O2/Fe+2 which register a maximal removal of 67.70% of COD, 92.30% of BOD5, and 14.90% of Hg. Finally, enhanced coagulation (EC) with in situ formed Mn-Fe hydr(oxides) was employed and optimized by central composite design (CCD) of response surface methodology (RSM). Response surface plots denote an optimum condition of 0.13M ratio of Mn/Fe, 22.67mM of coagulant dose, and 7.78 of pH which corresponds to a maximum removal of 55.98% of COD and 77.68% of Hg. FTIR analysis of the precipitates of EC explained that the hydroxyl groups are primarily involved in the process of Hg removal. Moreover, EDAX spectrum also assured the removal of Hg by its existence with Mn-Fe complexes. Thus, the present line of treatment record an overall removal of 90.80% of COD, 98.0% of BOD5, 97.60% of NH3-N, and 82.68% of Hg which proves to be effective for the removal of leachate pollutants.

Degradation of cyanide, aniline and phenol in pre-treated coke oven wastewater by peroxide assisted electro-oxidation process.

The present study explored the feasibility of using graphite electrodes for the electrochemical oxidation of cyanide, thiocyanate, phenol and aniline with hydrogen peroxide. The dosing effects of hydrogen peroxide and current density were examined in the pre-treated coke oven wastewater. It was found that 0.025 M hydrogen peroxide and 13.63 mA/cm2 of current density were more favorable for the removal of 100%, 90%, 71% and 40% cyanide, thiocyanate, phenol and aniline respectively. The increased removal of phenol in the coke oven wastewater was attributed to the pre-treatment of wastewater. Initially, 28% phenol was converted to phenolate ion by air stripping process, which increased the removal rate of phenol by the electro-oxidation process as the removal of phenolate is quite easy compared to phenol. The advanced oxidation process degrades the more toxic cyanide into less toxic intermediate cyanate ions (CNO─), which further cut down into nontoxic end products such as N2, HCO3 and CO2. The experimental results show that the primary mechanisms in the oxidation of cyanide and phenol are mediated electro-oxidation by hydroxyl radicals and hypochlorite ions. The operating cost under the optimized conditions for the removal of 100% cyanide and 71% phenol was estimated to be 616.95 INR/m3.

Nitrogen Recovery from Wastewater: Possibilities, Competition with Other Resources, and Adaptation Pathways

Due to increased food production, the demand for nitrogen and phosphorus as fertilizers grows. Nitrogen-based fertilizers are produced with the Haber–Bosch process through the industrial fixation of N2 into ammonia. Through wastewater treatment, the nitrogen is finally released back to the atmosphere as N2 gas. This nitrogen cycle is characterized by drawbacks. The energy requirement is high, and in the wastewater treatment, nitrogen is mainly converted to N2 gas and lost to the atmosphere. In this study, technologies for nitrogen recovery from wastewater were selected based on four criteria: sustainability (energy use and N2O emissions), the potential to recover nitrogen in an applicable form, the maturity of the technology, and the nitrogen concentration that can be handled by the technology. As in wastewater treatment, the focus is also on the recovery of other resources; the interactions of nitrogen recovery with biogas production, phosphorus recovery, and cellulose recovery were examined. The mutual interference of the several nitrogen recovery technologies was studied using adaptive policy making. The most promising mature technologies that can be incorporated into existing wastewater treatment plants include struvite precipitation, the treatment of digester reject water by air stripping, vacuum membrane filtration, hydrophobic membrane filtration, and treatment of air from thermal sludge drying, resulting respectively in 1.1%, 24%, 75%, 75%, and 2.1% nitrogen recovery for the specific case wastewater treatment plant Amsterdam-West. The effects on sustainability were limited. Higher nitrogen recovery (60%) could be realized by separate urine collection, but this requires a completely new infrastructure for wastewater collection and treatment. It was concluded that different technologies in parallel are required to reach sustainable solutions. Nitrogen recovery does not interfere with the recovery of the other resources. An adaptation pathways map is a good tool to take into account new developments, uncertainties, and different ambitions when choosing technologies for nitrogen recovery.

Effective removal of MIB and geosmin using MBBR for drinking water treatment

Biodegradation is an effective method for the removal of taste and odour (T&O) compounds from drinking water sources. In this study, the applicability of a moving-bed biofilm reactor (MBBR) as biological treatment step for the control of MIB and geosmin was studied at pilot-scale. After a 3.5 month acclimation period both T&O compounds could be reliably removed by at least 80%. Biodegradation was found to be the dominant removal mechanism with air stripping contributing up to 25% at shorter HRTs. Also sorption of MIB and geosmin onto carriers and biofilm did occur, simultaneously facilitating the biodegradation process. The biodegradation of MIB and geosmin followed pseudo-first-order kinetics.

Cultivation of Chlorella vulgaris in manure-free piggery wastewater with high-strength ammonium for nutrients removal and biomass production: Effect of ammonium concentration, carbon/nitrogen ratio and pH

Ammonia toxicity is a major disadvantage of microalgal growth when high-strength ammonium wastewaters like manure-free piggery wastewater (MFPW) were used as microalgal growth medium. In the present study, the effect of ammonium concentration, carbon/nitrogen ratio, and pH on ammonia toxicity of Chlorella vulgaris cultivated in the MFPW and nutrients removal was investigated. The three important parameters affected ammonia toxicity of C. vulgaris and nutrients removal of the MFPW significantly. The ammonium concentration of the MFPW could be decreased by air stripping. Microalga grew best at a carbon/nitrogen ratio of 25:1 with the maximum biomass concentration of 3.83 g L−1, the highest cell viability of 97%, and the removal of 100% ammonia, 95% of total phosphorus, and 99% of chemical oxygen demand. Ammonia toxicity was alleviated by pH control. The application of the established strategies can enhance nutrients removal of the MFPW while mitigating ammonia toxicity of C. vulgaris.

Recovery of phosphorus and nitrogen from human urine by struvite precipitation, air stripping and acid scrubbing: A pilot study

Sustainable and closed-loop nutrient cycling require the recovery of valuable resources from wastewater. Resource recovery from diluted wastewater streams is limited by diluted concentrations and unfavorable reaction kinetics. In comparison, source separated urine allows resource recovery from a highly concentrated nutrient stream, resulting in a more sustainable and efficient recovery practice. Different nutrient recovery methods from urine have been studied in lab-scale, but pilot or full-scale process evaluations remain sparse. In this study, recovery of struvite and ammonium sulfate from urine of pregnant women was demonstrated at a pilot-scale treatment facility by means of precipitation and air stripping/acid scrubbing. The system achieved 94% struvite precipitation efficiency but merely 55% of the crystals were removed and recovered. The low phosphorus recovery was due to the washout of small crystals that escaped the sieve and settling tank, hence requiring an improved method for crystals capture. The removal and recovery efficiencies for nitrogen were 93% and 85%, respectively. Composition analysis of the produced fertilizers indicated that struvite was the dominated precipitate and quality of the ammonium sulfate met European standards. Carbamazepine and diclofenac were added in the urine to measure the fate of pharmaceuticals in the treatment system. Very little of the spiked pharmaceuticals (<0.01%) accumulated in the produced struvite and ammonium sulfate. The overall energy demand of the pilot system was 1066 MJ per m3 urine processed or 198 MJ per kg N removed. Energy efficiency was not optimized and can be improved in many ways.

A mobile, modular and rapidly-acting treatment system for optimizing and improving the removal of non-aqueous phase liquids (NAPLs) in groundwater.

Non-aqueous phase liquids (NAPLs) in pumped groundwater are highly variable, challenging the selection of above-ground treatment strategies in pump-and-treat system. Adjustable systems with multiple treatment units are urgently required. In the present study, a mobile, modular and rapidly-acting treatment system was developed to treat groundwater contaminated by NAPLs at a chemical industrial site. The system integrated four units of coagulation sedimentation, air flotation, air stripping and chemical oxidation. During a 3-month onsite operation, the composition of groundwater NAPLs had huge fluctuations and different treatment units had unique advantages in eliminating some components. For instance, air stripping exhibited satisfactory removal efficiencies (>80%) for short-chain petroleum hydrocarbons and chloroalkanes, but poor performance for others comparing to other units. A decision-making tool and a central control system were further developed to combine and adjust the four units in proper orders, achieving satisfied removal efficiency (70-90%) for multi-component NAPLs, regardless of composition fluctuation. These findings raise the state-of-the-art modular and rapidly-acting groundwater treatment system to clean up NAPLs contaminated groundwater through pump-and-treat strategy, help in better understanding on the decision and management to improve the treatment performance, and provide guidelines for its implication at other sites contaminated with multi-component NAPLs or undergoing accidental contamination.

Removing ammonia from skim by air stripping with rotating packed bed

Abstract Based on the effects of skim components on ammonium removal as well as the current processing technology, a new process-intensified technology of removing ammonia from skim by air stripping on rotating packed bed was proposed. The experiments were conducted on a wave-thread packed Rotating Packed Bed (RPB) under atmospheric pressure, suggesting that, in terms of order of importance, the ammonium concentration of feed-stock (xw), the average ultra-gravity factor (β), feed-stock flux (L), and gas flux (G) had significant impact on ammonium removal rate (η) and the ammonium concentration of products (xD). In the experiment, mass-transfer coefficient in gas phase (kyae) increases with the increase of β, G/L, and L. The ammonium concentration of products decreases with the increase of β, G/L and the increase of L. The ammonium concentration of products would be as low as 0.10% and the ammonia removal rate would be 63.21% when skim temperature was 25 °C, xw 0.28%, β 133.2, and G/L 15.0 m3·L− 1. Experiment results indicated that the proposed technology for removing ammonium from skim on a rotating packed bed would be a new process-intensified technique compared with traditional aeration process and centrifugal atomization method.