The application of high frequency ultrasound waves to remove ammonia from simulated industrial wastewater

Comparative study of different ultrasound based hybrid oxidation approaches for treatment of real effluent from coke oven plant

The present study investigates the treatment of real coke plant effluent utilising several ultrasound-based hybrid oxidation approaches including Ultrasound (US) alone, US + catalyst, US + H2O2, US + Fenton, US + Ozone, and US + Peroxone, with main objective as maximizing the reduction of chemical oxygen demand (COD). Ultrasonic horn at power of 130 W, frequency as 20 kHz and duty cycle as 70% was applied. Study with varying catalyst (TiO2) dose from 0.5 g/L - 2 g/L revealed 1 g/L as the optimum dose resulting in 65.15% reduction in COD. A 40 ml/L dose of H2O2 was shown to be optimal, giving an 81.96% reduction in COD, based on the study of varied doses of H2O2 from 20 ml/L to 60 ml/L. US + Fenton reagent combination at optimum Fe2+/H2O2 (w/v) ratio of 1:1 resulted in a COD reduction of 85.29% whereas reduction of COD as 81.75% was obtained at the optimum flow rate of ozone as 1 LPM for US + Ozone approach. US + Peroxone demonstrated the best efficiency (90.48%) for COD reduction. To find the toxicity effects, the treated (US + peroxone) and non-treated samples were tested for the growth of bacterial cultures. It was observed that the toxicity of the treated sample increased only marginally after treatment. High-resolution liquid chromatography mass spectrometry (HR-LCMS) analysis was also performed to establish intermediate compounds. Overall, the coupling of ultrasound with oxidation processes produced better results with US + Peroxone established as best treatment approach for coke plant effluent.

Extensive investigation of geometric effects in sonoreactors: Analysis by luminol mapping and comparison with numerical predictions

This investigation focuses on the influence of geometric factors on cavitational activity within a 20kHz sonoreactor containing water. Three vessels with different shapes were used, and the transducer immersion depth and liquid height were varied, resulting in a total of 126 experiments conducted under constant driving current. For each one, the dissipated power was quantified using calorimetry, while luminol mapping was employed to identify the shape and location of cavitation zones. The raw images of blueish light emission were transformed into false colors and corrected to compensate for refraction by the water-glass and glass-air interfaces. Additionally, all configurations were simulated using a sonoreactor model that incorporates a nonlinear propagation of acoustic waves in cavitating liquids. A systematic visual comparison between luminol maps and color-plots displaying the computed bubble collapse temperature in bubbly regions was conducted. The calorimetric power exhibited a nearly constant yield of approximately 70% across all experiments, thus validating the transducer command strategy. However, the numerical predictions consistently overestimated the electrical and calorimetric powers by a factor of roughly 2, indicating an overestimation of dissipation in the cavitating liquid model. Geometric variations revealed non-monotonic relationships between transducer immersion depth and dissipated power, emphasizing the importance of geometric effects in sonoreactor. Complex features were revealed by luminol maps, exhibiting appearance, disappearance, and merging of different luminol zones. In certain parametric regions, the luminol bright regions are reminiscent of linear eigenmodes of the water/vessel system. In the complementary parametric space, these structures either combine with, or are obliterated by typical elongated axial structures. The latter were found to coincide with an increased calorimetric power, and are conjectured to result from a strong cavitation field beneath the transducer producing acoustic streaming. Similar methods were applied to an additional set of 57 experiments conducted under constant geometry but with varying current, and suggested that the transition to elongated structures occurs above some amplitude threshold. While the model partially reproduced some experimental observations, further refinement is required to accurately account for the intricate acoustic phenomena involved.

Ultrasonic Disintegration to Improve Anaerobic Digestion of Microalgae with Hard Cell Walls-Scenedesmus sp. and Pinnularia sp

Microalgae are considered to be very promising feedstocks for biomethane production. It has been shown that the structure of microalgal cell walls can be highly detrimental to the anaerobic digestibility of biomass. Therefore, there is a real need to seek ways to eliminate this problem. The aim of the present study was to assess the effect of ultrasonic disintegration of Scenedesmus sp. and Pinnularia sp. microalgal biomass on the performance and energy efficiency of anaerobic digestion. The pretreatment was successful in significantly increasing dissolved COD and TOC in the system. The highest CH₄ yields were noted for Scenedesmus sp. sonicated for 150 s and 200 s, which produced 309 ± 13 cm³/gVS and 313 ± 15 cm³/gVS, respectively. The 50 s group performed the best in terms of net energy efficiency at 1.909 ± 0.20 Wh/gVS. Considerably poorer performance was noted for Pinnularia sp., with biomass yields and net energy gains peaking at CH₄ 250 ± 21 cm³/gVS and 0.943 ± 0.22 Wh/gVS, respectively. Notably, the latter value was inferior to even the non-pretreated biomass (which generated 1.394 ± 0.19 Wh/gVS).

Simulations of a full sonoreactor accounting for cavitation

In spite of the increasing interest in ultrasound processing applications, industrial scale-up remains limited, in particular by the unavailability of predictive computer tools. In this study, using a previously published model of cavitating liquids implementable as a non-linear Helmholtz equation, it is shown that a full sonoreactor can be modelled and simulated. The model includes the full transducer and the vibrations of the vessel walls, using the physics of elastic solids and piezo-electricity. The control-loop used by the generator to set the optimal frequency is also accounted for. Apart from the geometry, the unique input of the model is the current feeding the transducer whereas the dissipated electrical power, transducer complex impedance and working frequency are available as outputs. The model is put to the test against experiments realized in different geometries, varying either the input current or the transducer immersion depth. Despite the overestimation of the power dissipated in the liquid, the evolution of the acoustic load in both cases is reasonably well reproduced by simulation, which partially validates the method used.

Effect of Acid Whey Pretreatment Using Ultrasonic Disintegration on the Removal of Organic Compounds and Anaerobic Digestion Efficiency

Acid whey is a by-product of the dairy industry that should be utilized or appropriately neutralized. Anaerobic processes represent a group of prospective methods for whey processing, and a key priority in their development is to improve their technological and economical effectiveness. The present study aimed to determine the effect of ultrasonic disintegration (UD) of acid whey on the course and effectiveness of methane fermentation. The study results demonstrated that extending the UD duration resulted in increased concentrations of dissolved forms of COD and TOC, efficiency of organic matter biodegradation, and CH₄ production. The best effects were achieved at 900 s US, including CH₄ production of 0.203 ± 0.01 dm³/gCOD_in. and CH₄ content accounting for 70.9 ± 2.8%. Organic compounds were removed with the following efficiencies: COD-78.7 ± 2.1%, TOC-80.2 ± 1.3%, and BOD₅-84.1 ± 1.6%. The highest net energy gain of 5.763 Wh was achieved upon UD of 300 s. Extension of UD time had no significant effect on the improvement in the energetic effectiveness of anaerobic digestion. A strong positive correlation was found between COD and TOC concentrations in the dissolved phase and CH₄ production yield.

Influence of non-commercial fuel supply systems on small engine SI exhaust emissions in relation to European approval regulations

The development and operation of road infrastructure require machines and equipment driven by low-powered internal combustion engines. In this study, we conducted emission tests on five small spark-ignition engines. We used the most popular commercial design on the market, the Lifan GX 390, with a carburettor power system, and another commercial power unit, the Honda iGX 390, with an innovative power system characterised by an electronically controlled carburettor flap. The remaining three tested constructions were proprietary solutions modernising the design of the Lifan GX 390 engine: one had an electronic injection and ignition system powered by gasoline, whereas the other two had systems powered by alternative fuels. Emission tests were conducted under identical operating conditions on an engine dynamometer complying with European Union guidelines (Regulation 2016/1628/EU). The results of the tests showed that the innovative solutions in most cases reduced CO, CO₂ and hydrocarbon emissions but increased NO_x compounds.

Remove of ammoniacal nitrogen wastewater by ultrasound/Mg/Al2O3/O3

A large amount of ammoniacal nitrogen wastewater discharged into the water body not only causes eutrophication and black and offensive odor in water, but also increases the difficulty and cost of water treatment, and even produces toxic effects on people and organisms. In this paper, degradation of ammoniacal nitrogen wastewater by the system of ultrasound/Mg/Al₂O₃/ozone (US/Mg/Al₂O₃/O₃) was carried out. The effects of different influencing factors, such as initial pH of the solution, reaction time, temperature, catalyst addition, ozone flow rate, and ultrasonic intensity, on the degradation of ammoniacal nitrogen wastewater were investigated. The optimum reaction conditions were determined. The combination of ultrasonic technology and ozone oxidation technology can enhance the mass transfer of ozone and generate a large amount of HO. Due to Mg/Al₂O₃ catalyst has large surface area, the number of reactive sites and reaction molecule transport channels per unit area increases, resulting in the increase of HO on the surface, thus improving the catalytic activity. The introduction of ultrasound promotes the cleavage of N-H bonds on the catalyst surface, thereby promoting the degradation of ammoniacal nitrogen in the water. Results prove that there is not only a synergistic effect between ultrasound and catalytic ozone oxidation, but a strengthening effect of ultrasound on catalytic ozone oxidation. The research carried out in this paper provides a theoretical basis for the degradation of ammoniacal nitrogen in water.

Conversion of Ammonia to Hydrazine Induced by High-Frequency Ultrasound

Hydrazine is a chemical of utmost importance in our society, either for organic synthesis or energy use. The direct conversion of NH₃ to hydrazine is highly appealing, but it remains a very difficult task because the degradation of hydrazine is thermodynamically more feasible than the cleavage of the N-H bond of NH₃ . As a result, any catalyst capable of activating NH₃ will thus unavoidably decompose N₂ H₄ . Here we show that cavitation bubbles, created by ultrasonic irradiation of aqueous NH₃ at a high frequency, act as microreactors to activate and convert NH₃ to NH species, without assistance of any catalyst, yielding hydrazine at the bubble-liquid interface. The compartmentation of in-situ-produced hydrazine in the bulk solution, which is maintained close to 30 °C, advantageously prevents its thermal degradation, a recurrent problem faced by previous technologies. This work also points towards a path to scavenge ^. OH radicals by adjusting the NH₃ concentration.

Treatment of slaughterhouse wastewater using high-frequency ultrasound: optimization of operating conditions by RSM

Slaughterhouse processes produce substantial amounts of high organic strength wastewater due to high COD level. A fundamental work had been carried out to explore the removal of COD from actual poultry slaughterhouse wastewater by ultrasound irradiation. The effect of applied frequency, power density, irradiation time, pH, and adding H₂O₂ on COD removal was investigated. The COD removal reached ultimate levels after irradiation time of 180 min. The COD removal percentage increased from 2% to 43% and from 2% to 49% when the power density increased from 160 to 1200 W/L at working frequencies of 1142 and 578 kHz, respectively. Increasing the pH from 7 to 9 reduced the COD removal from 51% to 13%. At low power densities, the high frequency (1142 kHz) was more efficient in COD removal than low frequency (578 kHz) and vice versa at high power densities. A combined system of US and H₂O₂ was more effective in removing COD than US standalone system. Finally, the kinetics of the COD decay using sonication was found to obey the first-order model. In conclusion, the US can be used efficiently at least to pretreat slaughterhouse wastewater with a COD removal of about 50%.

Who is Asked and Who Gets to Answer the Health-Care Practitioner's Questions When Patients with Intellectual Disabilities Attend UK General Practice Health Checks with Their Companions?

When patients with intellectual disabilities (ID) attend a General Practice annual health check, current guidance directs health-care practitioners (HCPs) to involve them as much as possible as informants on their health. However, previous research based on interviews with participants suggests that during health consultations their communicative contributions of patients with ID may be sidelined in favor of information provided by caregivers perhaps because of HCPs' uncertainties about how to address the communication needs of these patients. The aim of this study was to establish, within naturally occurring health consultations, who HCPs select to answer their questions during health checks - patients with ID or their companions - and who actually answers. A nonconsecutive case series of primary care annual health checks involving patients with ID and their companions (n = 24) was conducted. Health checks were video-recorded and analyzed using tools of Conversation Analysis. We found that HCPs consistently selected patients with ID to answer their questions and patients then responded without significant gaps or dyfluencies in the immediate next turn at talk 70.1% of the instances. Companions were selected to respond in 9.3% of the total question-answer sequences recorded. Family members were more likely to be chosen as the addressee of HCP questions, compared to staff companions. They were also more likely to intervene to answer questions that had been directed at the patient. We conclude that health communication with patients with ID need not necessarily pose insurmountable challenges for HCPs, though the structure of the health check, with many questions requiring only a yes/no response may have reduced the communicative demand on patients. More research is needed to investigate how HCP involve patients with ID in more extensive health information exchange or health decision-making.

Impact of Compressed Natural Gas (CNG) Fuel Systems in Small Engine Wood Chippers on Exhaust Emissions and Fuel Consumption

The projected increase in the availability of gaseous fuels by growing popularity of household natural gas (NG) filling stations and the increase in the production of gaseous biogas-derived fuels is conducive to an increase in the use of NG fuel. Currently, natural gas in various forms (compressed natural gas (CNG), liquefied natural gas (LNG)) is popular in maritime, rail and road transport. A new direction of natural gas application may be non-road mobile machines powered by a small spark-ignition engine (SI). The use of these engines in the wood chippers can cause the reduction of machine costs and emissions of harmful exhaust gases. In addition, plant material chippers intended for composting in bio-gas plants can be driven by the gas they are used to produce. The biogas can be purified to bio-methane to meet natural gas quality standards. The article presents the design of the natural gas supply system, which is an upgrade of the Lifan GX 390 combustion engine spark ignition engine (Four-stroke, OHV (over head valve) with a maximum power of 9.56 kW), which is a common representative of small gasoline engines. The engine is mounted in a cylindrical chipper designed for shredding branches with a maximum diameter of up to 100 mm, which is a typical machine used for cleaning work in urban areas. The engine powered by CNG and traditionally gasoline has been tested in real working conditions, when shredding cherry plum (Prunus cerasifera Ehrh. Beitr. Naturk. 4:17. 1789 (Gartenkalender4:189–204. 1784)). Their diameter was ca. 80 mm, 3-metere-long, and humidity content ca. 25%. The systems were tested under the same actual operating conditions, the average power generated by the drives during shredding is about 0.69 kW. Based on the recorded results, it was found that the CNG-fuelled engine was characterized by nitrogen oxides (NOx) emissions higher by 45%. The other effects of CNG were a reduction in carbon dioxide (CO2), carbon monoxide (CO) and hydrocarbon (HC) emissions of about 81%, 26% and 57%, respectively. Additionally, the use of CNG reduced fuel consumption by 31% and hourly estimated machine operating costs resulting from fuel costs by 53% (for average fuel price in Poland: gasoline: 0.99 EUR/L and CNG: 0.71 EUR/m3 on 08 November 2020). The modernization performed by the authors ensured the work of the drive unit during shredding, closer to the value of stoichiometric mixtures. The average (AVG) value of the air fuel ratio (AFR) for CNG was enriched by 1.2% (AVG AFR was 17), while for the gasoline engine the mixture was more enriched by 4.8% (AVG AFR was 14). The operation of spark-ignition (SI) combustion engines is most advantageous when burning stoichiometric mixtures due to the cooperation with exhaust aftertreatment systems (e.g., three-function catalytic converter). A system powered by CNG may be beneficial in systems adapting to operating conditions, used in low-power shredding machines, whose problem is increased HC emissions, and CNG combustion may reduce them. The developed system does not exceed the emission standards applicable in the European Union. For CO emissions expressed in g/kWh, it was about 95% lower than the permissible value, and HC + NOx emissions were 85% lower. This suggests that the use of the fuel in question may contribute to tightening up the permissible emission regulations for non-road machinery.

Evaluation of Anaerobic Digestion of Dairy Wastewater in an Innovative Multi-Section Horizontal Flow Reactor

The aim of this study was the performance evaluation of anaerobic digestion of dairy wastewater in a multi-section horizontal flow reactor (HFAR) equipped with microwave and ultrasonic generators to stimulate biochemical processes. The effects of increasing organic loading rate (OLR) ranging from 1.0 g chemical oxygen demand (COD)/L·d to 4.0 g COD/L·d on treatment performance, biogas production, and percentage of methane yield were determined. The highest organic compounds removals (about 85% as COD and total organic carbon—TOC) were obtained at OLR of 1.0–2.0 g COD/L·d. The highest biogas yield of 0.33 ± 0.03 L/g COD removed and methane content in biogas of 68.1 ± 5.8% were recorded at OLR of 1.0 g COD/L·d, while at OLR of 2.0 g COD/L·d it was 0.31 ± 0.02 L/COD removed and 66.3 ± 5.7%, respectively. Increasing of the OLR led to a reduction in biogas productivity as well as a decrease in methane content in biogas. The best technological effects were recorded in series with an operating mode of ultrasonic generators of 2 min work/28 min break. More intensive sonication reduced the efficiency of anaerobic digestion of dairy wastewater as well as biogas production. A low nutrient removal efficiency was observed in all tested series of the experiment, which ranged from 2.04 ± 0.38 to 4.59 ± 0.68% for phosphorus and from 9.67 ± 3.36 to 20.36 ± 0.32% for nitrogen. The effects obtained in the study (referring to the efficiency of wastewater treatment, biogas production, as well as to the results of economic analysis) proved that the HFAR can be competitive to existing industrial technologies for food wastewater treatment.

Optimization of ibuprofen degradation in water using high frequency ultrasound-assisted biological reactor

Ultrasound (US) is being considered as a promising emerging advanced oxidation process to degrade persistent organic-pollutants. This paper investigated the effect of several operating parameters on the degradation of a recalcitrant pharmaceutical product, namely ibuprofen (IBP), using an ultrasound-assisted biological reactor. The tested operating parameters are the power density (960, 480) W/L, US frequency (1,142, 860, 578) kHz, working volume (500, 250) mL, initial IBP concentration (30, 60) mg/L, and pH (8.2, 4). It was observed that the IBP degradation was directly influenced by the power density, and the highest degradation efficiency (99%) was obtained at 960 w/L. However, the degradation of IBP at sonication time of 120 min was found to increase from 39% to 96% while decreasing the US frequency from 1,142 to 578 kHz. The working volume had no clear effect on the IBP degradation. The optimal pH was found to be 4, which resulted in 99.5% IBP degradation efficiency after 120 min of sonication time. The degradation of IBP followed the first order kinetics. Finally, the sonically-treated water was fed to a subsequent aerobic biological reactor. The results revealed that the remaining chemical oxygen demand (COD) after sonication was lowered in the biological reactor by a percentage of 47%.

Ultrasound assisted biogas production from landfill leachate

The aim of this study is to increase biogas production and methane yield from landfill leachate in anaerobic batch reactors by using low frequency ultrasound as a pretreatment step. In the first part of the study, optimum conditions for solubilization of organic matter in leachate samples were investigated using various sonication durations at an ultrasound frequency of 20 kHz. The level of organic matter solubilization during ultrasonic pretreatment experiments was determined by calculating the ratio of soluble chemical oxygen demand (sCOD) to total chemical oxygen demand (tCOD). The sCOD/tCOD ratio was increased from 47% in raw leachate to 63% after 45 min sonication at 600 W/l. Non-parametric Friedman's test indicated that ultrasonic pretreatment has a significant effect on sCOD parameter for leachate (p<0.05). In the second part of the study, anaerobic batch reactors were operated for both ultrasonically pretreated and untreated landfill leachate samples in order to assess the effect of sonication on biogas and methane production rate. In anaerobic batch reactor feed with ultrasonically pretreated leachate, 40% more biogas was obtained compared to the control reactor. For statistical analysis, Mann-Whitney U test was performed to compare biogas and methane production rates for raw and pretreated leachate samples and it has been found that ultrasonic pretreatment significantly enhanced biogas and methane production rates from leachate (p<0.05) in anaerobic batch reactors. The overall results showed that low frequency ultrasound pretreatment can be potentially used for wastewater management especially with integration of anaerobic processes.

Sonochemical destruction of chloroform by using low frequency ultrasound in batch and flow cell

Ultrasound assisted environmental remediation is emerging as a viable technology to remove organic pollutants. In this study, the potential of low frequency ultrasound (20 kHz) to remediate chloroform contaminated waters (demineralised water and groundwater) in batch and flow cell treatment was evaluated. The results show that approx. 8 mg/L of chloroform was completely mineralized within 60 min in batch as well as flow cell treatments in both waters. However, flow cell treatment was superior to the batch mode for demineralised water in contrast to the groundwater for which there was no appreciable difference between batch and flow cell modes during initial 30 min. The presence of dissolved organic carbon, higher total dissolved solid content and any other co-contaminants might have contributed to the slower rate of chloroform destruction in the groundwater compared to the demineralised water. This study demonstrates the potential of low frequency ultrasound for remediation of chloroform contaminated waters.

Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave

This article aims to apply the ultrasound technique in the field of clean technology to protect environment. The principle of sonochemistry is conducted here to degrade pesticides in simulated industrial wastewater resulted from a factory manufacturing pesticides namely diazinon. Diazinon pesticide selected in this study for degradation under high frequency ultrasound wave. Three different initial concentrations of diazinon (800, 1200, and 1800 ppm), at different solution volumes were investigated in to degrade dissolved diazinon in water. Ultrasound device with 1.7 MHz, and 0.044 cm diameter, was used to study the degradation process. It is found that as the concentration of diazinon increased, the degradation is also increasing, and when the solution volume increases, the ability to degraded pesticides decreases. The experimental results showed an optimum condition achieved for degradation of diazinon at 1200 ppm as initial concentration and 50 ml solution volume. Kinetic modeling applied for the obtained results showed that the degradation of diazinon by high ultrasound frequency wave followed a pseudo-first-order model with apparent rate constant of around of 0.01 s(-1).