Study on SO_2 Removal Efficiency by Nanosecond Rising Edge Pulse DBD Under Different Environmental Conditions

In this paper, an experimental study on SO2 removal by nanosecond rising edge pulse dielectric barrier discharge （DBD） plasma, generated by multi-needle-to-plane electrodes, is carried out. The mechanism of the effect of various factors, such as gap size between dielectric barrier and discharge needles, environmental humidity, and inlet speed of gas flow upon the removal efficiency of air purification is analyzed. The studies show that SOs removal efficiency improves with the increase in the gap size between dielectric barrier and discharge needles in the case of a fixed space between two electrodes, and also improves with the increase in the environmental humidity. For a mixed gas with a fixed concentration, there is an optimal inlet speed of gas flow, which leads to the best removal efficiency.

Water film area and dust removal efficiency of string grilles:a theoretical analysis

Based onmultiphase flowtheory and capillary mechanics,the dimensionless bond number expression of the influence of string grille wire spacing on droplet spreading is derived.Taking a liquid film formed by spreading droplets based on Kelvin correlation,the Young-Laplace equation,and the Hagen-Poiseuille law,an equation for calculating the thickness and height of the liquid film is established with temperature,relative humidity and molar volume of liquid phase as independent variables.According to the theory of string grille filtration and dust removal,a dust removal efficiency calculation model covering the wet string grille wire group is constructed based on the liquid film thickness,height,wire diameter,water film area,and vortex shedding frequency.Finally,a theoretical analysis of the influence of water film area on the efficiency of wet string grille dust removal is carried out based on the spray pressure and the ratio of string grille wire distance to wire diameter.It is found that the effect of spray pressure on water film area and dust removal efficiency is more significant than the string grille wire distance diameter ratio.Moreover,the optimized combination of wet string grille wire distance diameter ratio 0.84,wind speed 3m/s and spray pressure 0.8 MPa is found,which could provide an important reference for engineering applications.

Removal Effect of Precipitation on Atmospheric Particulate Matter (PM_(2.5) ) in Bengbu City

Based on the monitoring data of PM_(2.5) concentration in Bengbu Environmental Monitoring Station and precipitation observation data of Bengbu National Meteorological Observation Station from 2016 to 2019, the influence of precipitation on PM_(2.5) mass concentration in Bengbu City was analyzed. The results show that precipitation had a washing and removal effect on PM_(2.5) in the air, and the removal effect was related to precipitation level, precipitation intensity, precipitation duration and PM_(2.5) concentration. The removal effect of precipitation on PM_(2.5) increased with the increase of precipitation level, and the seasonal difference was obvious. Precipitation intensity was positively correlated with the removal effect of PM_(2.5) , but the average removal rate began to decline when precipitation intensity exceeded 10 mm. With the increase of precipitation intensity, the proportion of positive removal showed an overall upward trend, but there was a low-value area as precipitation intensity was 3-10 mm. Precipitation duration was also positively correlated with the removal effect of PM_(2.5) , and there was a low-value area when precipitation duration was 10-15 h. When PM_(2.5) concentration was low before the precipitation process began, the removal effect was not good, and the average removal rate was negative. As PM_(2.5) concentration was high before the precipitation process started, the removal effect was obvious.

Settling basin design in a constructed wetland using TSS removal efficiency and hydraulic retention time

Using total suspended solid （TSS） removal efficiency and hydraulic retention time （HRT） as design parameters a design guideline of a settling basin in a constructed wetland （CW） was suggested; as well as management of sediment and particle in the settling basin. The CW was desiEned to treat the piggery wastewater effluent from a wastewater treatment plant during dry days and stonnwater runoff from the surrounding paved area during wet days. The first settling basin （FSB） in the CVV was theoretically designed with a total storage volume （TSV） of 453 ms and HRT of 5.5 hr. The amount of sediment and particles settled at the FSB was high due to the sedimentation and interception of plants in the CVV. Dredging of sediments was performed when the retention rate at the FSB decreased to approximately 80%. Findings showed that the mean flow rate was 21.8 m3/hr less than the designed flow rate of 82.8 m3/hr indicating that the FSB was oversize and operated with longer HRT （20.7 hr） compared to the design HRT. An empirical model to estimate the length of the settling basin in the CW was developed as a function of HRT and desired TSS removal efficiency. Using the minimum tolerable TSS removal efficiency of 30%, the length of the FSB was estimated to be 31.2 m with 11.8 hr HRT.

Antibiotics in two municipal sewage treatment plants in Sri Lanka:Occurrence,consumption and removal efficiency

Most of the monitoring data on the occurrence of antibiotics in sewage treatment plants(STPs)have been reported from Europe,North America and some countries in Northeast Asia,while very limited data can be found in Southeast Asian countries.As a pioneering research in Sri Lanka,we collected 24 h composite wastewater samples at the influent and effluent of two municipal STPs for consecutive 7 days to investigate occurrence,consumption and removal efficiency of seventeen antibiotics.The STP was located in Colombo and Hikkaduwa,respectively,representing two kinds of communities(i.e.local and tourists)in Sri Lanka.The targeted antibiotics were extracted by solid-phase extraction method and detected on an Agilent HPLCMSMS(1290/6470QQQ).Results illustrated that the majority of the antibiotics can be always detected from both STPs,except for chlorotetracycine(CTC),doxycycline(DOX)and florfenicol(FF).Fluoroquinolones(FQs)were detected at highest concentrations with ciprofloxacin(CIP)being the dominant compound.Concentrations of CIP in the influent samples were in the range of 433 e6010 ng/L.The consumption of antibiotics was estimated on the basis of influent mass load and catchment population data.We found difference in consumption patterns between the two served areas.Compared to local people in Colombo,tourists in Hikkaduwa appeared to take more antibiotics during the study period with the estimated daily dose of 0.25 g per 1000 persons.Moreover,macrolides accounted for a larger portion than FQs in Hikkaduwa,with azithromycin(AZM)being the most prevalent antibacterial agent.After comparison with an official report by Medical Supplies Division of Sri Lanka,we conjected that AZM was not commonly used among local people and it was mainly introduced by foreign arrivals.As for the removal efficiency,the activated sludge system of Colombo exhibited better elimination and more stable performance than the constructed wetland process of Hikkaduwa.

Numerical Simulation of Dust Removal in the Cyclone Collector of a Straw Crusher Based on a Discrete Phase Model

The cyclone dust collector is an important subsystem of straw crushers used in agriculture.In the present study,a new type of dust collector with involute morphology is proposed to obtain better dust removal efficiency with respect to that of classical tangential and spiral dust collectors.A discrete phase model(DPM)method is used in synergy with a turbulence model,and the SIMPLE algorithm to simulate the flow field inside the dust collector and the related particle dynamics.It is shown that the internal flow field features a primary swirl,a secondary swirl and blockage effects.Moreover,for the involute dust collector,the tangential velocity in the initial stage and the pressure in the high-pressure area are larger than those obtained for the classical types.The dust removal efficiency is 37.11%,25.3%,and 16.37%for the involute type dust collector,the tangential type and the spiral type,respectively.

Performance of a Horizontal Flow Constructed Reed Bed Filter for Municipal Wastewater Treatment: The Case Study of the Prototype Installed at Gaston Berger University, Saint-Louis, Senegal

In Saint-Louis, Senegal, a constructed wetland with horizontal flow reed beds (FHa and FHb) has demonstrated significant efficacy in treating municipal wastewater. Analyzing various treatment stages, the system showed only a slight temperature variation, from an influent average of 26.3°C to an effluent of 24.7°C. Electrical conductivity decreased from 1331 mS/cm to 974.5 mS/cm post-primary treatment, with suspended solids (SS) dramatically reduced from 718.9 mg/L to 5.7 mg/L in the final effluent. Biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) saw a notable decrease, from initial levels of 655.6 mg/L and 1240 mg/L to 2.3 mg/L and 71.3 mg/L, respectively. Nitrogenous compounds (N-TN) and phosphates () also decreased significantly, indicating the system’s nutrient removal capacity. Microbiological analysis revealed a reduction in fecal coliforms from 7.5 Ulog/100ml to 1.8 Ulog/100ml and a complete elimination of helminth eggs. The presence of Phragmites and Typha was instrumental in enhancing these reductions. The system’s compliance with the Senegalese standards for disposal into natural environments, WHO recommendations for unrestricted water reuse in irrigation, and the European legislation for water reuse was established. The effluent quality met the stringent criteria for various classes of agricultural reuse, illustrating the system’s potential for sustainable water management. This wetland model presents a robust solution for water-stressed regions, ensuring environmental protection while supporting agricultural needs. The study calls for ongoing research to further refine the system for optimal, reliable wastewater treatment and water resource sustainability.

Nitrogen Removal Improvement by Adding Peat in Deep Soil of Subsurface Wastewater Infi ltration System

In order to enhance the nitrogen removal, a subsurface wastewater infiltration system （SWIS） was improved by adding peat in deep soil as carbon source for denitrification process. The effects of addition of carbon source in the underpart of the SWIS on nitrogen removal at different influents （with the total nitrogen （TN） concentration 40 and 80 mg L^-1, respectively） were investigated by soil column simulating experiments. When the relatively light pollution influent with 40 mg L^-1 TN was used, the average concentrations of NO3-N and TN in effluents were （4.69±0.235）, （6.18±0.079） mg L^-1, respectively, decreased by 32 and 30.8% than the control; the NO3--N concentration of all effluents was below the maximum contaminant level of 10 mg L^-1; as high as 92.67% of the TN removal efficiency was achieved. When relatively heavy pollution influent with 80 mg LITN was used, the average concentrations of NO3--N and TN in effluents were （10.2±0.265）, （12.5±0.148） mg L^-1 respectively, decreased by 20 and 21.2% than the control; the NO3--N concentration of all effluents met the grade Ⅲ of the national quality standard for ground water of China （GB/T 14848-1993） with the values less than 20 mg L^-1; the TN removal efficiency of 94.1% was achieved. In summary, adding peat in the underpart of the SWIS significantly decreased TN and NO3- -N concentration in effluents and the nitrogen removal efficiency improved significantly.

Characterization of cobalt ferrite-supported activated carbon for removal of chromium and lead ions from tannery wastewater via adsorption equilibrium

In this experiment,cobalt ferrite-supported activated carbon(CF-AC)was developed and characterized via the wet impregnation method for the removal of Cr and Pb(II)ions from tannery wastewater.Batch adsorption was carried out to evaluate the effect of experimental operating conditions(pH of solution,contact time,adsorbent dose,and temperature),and the removal efficiencies of Cr and Pb(II)ions by the developed adsorbents were calculated and recorded for all experimental conditions.These variables were estimated and reported as removal efficiencies of 98.2%for Cr and 96.4%for Pb(II)ions at the optimal conditions of 5,0.8 g,80 min,and 333 K for pH,adsorbent dose,contact time,and temperature,respectively.The equilibrium for the sorption of Cr and Pb(II)ions was studied using four widely used isotherm models(the Langmuir,Freundlich,Dubinin-Radushkevich,and Temkin isotherm models).It was found that the Freundlich isotherm model fit better with the coefficient of determination(R2)of 0.9484 and a small sum of square error of 0.0006.The maximum adsorption capacities(Qm)of Pb(II)and Cr adsorbed onto CF-AC were determined to be 6.27 and 23.6 mg/g,respectively.The adsorption process conformed well to pseudo-second order kinetics as revealed by the high R2 values obtained for both metals.The thermodynamic parameters showed that adsorption of Cr and Pb(II)ions onto CF-AC was spontaneous,feasible,and endothermic under the studied conditions.The mean adsorption energy(E)values revealed that the adsorption mechanism of Cr and Pb(II)by CF-AC is physical in nature.The results of the study showed that adsorbent developed from CF-AC can be efficiently used as an environmentally friendly alternative adsorbent,for removal of Cr and Pb(II)ions in tannery wastewater.

Efficiency of Removing Sulfur Dioxide in the Air by Non-Thermal Plasma Along with the Application of the Magnetic Field

The non-thermal plasma created by high voltage pulsed power supply can be used to remove sulfur dioxide in the air, but how to increase the removing efficiency is not clear. It is novel to apply the magnetic field in removing SO2 as discussed in this paper. The mechanisms of removing sulfur dioxide by non-thermal plasma along with the application of the magnetic field are analyzed, and the related factors affecting the removal efficiency, such as the magnitude of pulsed voltage, the polarity of the pulse, the layout of the discharge electrode, especially the magnetic field are experimentally investigated. It can be concluded that the purification efficiency is improved significantly by applying the magnetic field.

Effects of live rock on removal of dissolved inorganic nitrogen in coral aquaria

Maintaining stable water quality is one of the key processes for recirculating coral aquaculture. Traditional aquarium systems which mainly utilized a nitrification of nitrifying bacteria attached to the surface of massive artificial filter material are difficult to maintain the oligotrophic conditions necessary for coral aquaculture. This study investigated the removal effects of dissolved inorganic nitrogen（ammonia and nitrate） by live rock（LR）, a key component in the ＂Berlin system＂ coral aquarium. The expression levels of bacterial functional genes, AOA3,amo A and nos Z, were measured on the exterior and interior of LR. The nitrifying and denitrifying bacterial abundance on LR was quantified and the nitrogen nutrient regulatory effects of LR were evaluated. The results demonstrated that LR mainly removed ammonium（NH_4~＋） from the water with a mean efficiency of 0.141 mg/（kg·h）, while the removal of nitrate（NO_3~–） was not significant. Bacterial diversity analysis showed that ammonia-oxidizing bacteria（AOB） were the most common bacteria on LR, which accounted for 0.5%–1.4% of the total bacterial population, followed by denitrifying bacteria, which accounted for 0.2% of the total population, and the ammonia-oxidizing archaea（AOA） were the least common type（〈0.01%）. The low abundance of denitrifying bacteria may be responsible for the poor nitrate（NO_3~–） removal of LR. Thus, other biological filtration methods are needed in coral aquaria to control nitrates generated from nitrification or biological metabolism.

Optimization for Nitrogen Removal in Anoxic/Oxic⁃Membrane Bioreactor by Response Surface Methodology

The optimal operating condition for the total nitrogen(TN)removal in an anoxic/oxic⁃membrane reactor(A/O⁃MBR)was studied by employing response surface methodology(RSM),which is a statistical test method for optimizing stochastic processes.The individual and interactive influences of three operating parameters including dissolved oxygen in aerobic tank(DO),internal mixed liquor recycle rate(IR),and mixed liquor suspended solids(MLSS)on the TN removal efficiency were evaluated.TN removal efficiency increased first and then reduced with the increase of DO,IR,and MLSS.Results from RSM indicated that the three factors had significant interactive influences on the TN removal efficiency.Meanwhile,the interaction between DO and MLSS had more significant effects on the TN removal efficiency than those of the other two.The maximum TN removal efficiency was forecasted at 83.34%according to the model when MLSS was 7926.6 mg/L,IR was 371.8%,and DO was 3.5 mg/L.Under this optimum condition,the experimental TN removal efficiency was 83.13%,which further confirmed that the optimum strategy was reliable.

Enhancement of Cathode Dust Collection and its Application in Improving the Efficiency of Dry Electrostatic Precipitator

As the main equipment of flue gas dedusting in coal fired boiler,electrostatic precipitator(ESP)can meet the requirements of emission standard for air pollutants from coal-fired power plants through improving the efficiency of ESP and combining with desulfurization system while not installing wet ESP(WESP).This paper introduces the modifications of ESP cathode structure to improve the efficiency of dust collection by reducing the secondary dust loss at cathode.The application of cathode dust collection provides a reference for the improvement of ESP dust collection efficiency.

An Improved NHPP Model with Time-Varying Fault Removal Delay

In this paper, an improved NHPP model is proposed by replacing constant fault removal time with time-varying fault removal delay in NHPP model, proposed by Daniel R Jeske. In our model, a time-dependent delay function is established to fit the fault removal process. By using two sets of practical data, the descriptive and predictive abilities of the improved NHPP model are compared with those of the NHPP model, G-O model, and delayed S-shape model. The results show that the improved model can fit and predict the data better.

Fate of Parent and Substituted Polycyclic Aromatic Hydrocarbons in SBR/MBBR Treatment Process:Experimental Value Against Model Prediction

The knowledge of the existence,distribution and fate of polycyclic aromatic hydrocarbons(PAHs)and substituted polycyclic aromatic hydrocarbons(SPAHs)in wastewater treatment plants(WWTPs)was vital for reducing their concentrations entering the aquatic environment.The concentrations of 13 SPAHs and 16 PAHs were all determined in a WWTP with styrene butadiene rubber(SBR)in partnership with the moving bed biofilm reactor(MBBR)process.SPAHs presented a higher concentration lever than PAHs in nearly all samples.The total removal efficiencies of PAHs and SPAHs ranged from 64.0%to 71.36%and 78.4%to 79.7%,respectively.The total yearly loads of PAHs(43.0 kg)and SPAHs(73.0 kg)were mainly reduced by the primary and SBR/MBBR biological treatment stages.The tertiary treatment stage had a minor contribution to target compounds removal.According to a synthesis and improvement fate model,we found that the dominant processes changed as the chemical octanol water partition coefficient(K_(ow))increased.But the seasonal variations of experimental removal efficiencies were more obvious than that of predicted data.In the primary sedimentation tank,dissolution in the aqueous phase and sorption to sludge/particulate matter were controlling processes for the removal of PAHs and SPAHs.The sorption to sludge and biodegradation were the principal removal mechanisms during the SBR/MBBR biological treatment process.The contribution of volatilization to removal was always insignificant.Furthermore,the basic physicochemical properties and operating parameters influenced the fate of PAHs and SPAHs in the WWTP.

Assessment of Sunflower (Helianthus annuus L.) for Phytoremediation of Heavy Metal Polluted Mine Tailings—A Case Study of Nampundwe Mine Tailings Dam, Zambia

Mining activities have led to a generation of large quantities of heavy metals laden wastes which are released into the environment in an unsustainable way causing the contamination of the ecosystems and posing a risk to human health. Most mining companies have not employed any rehabilitation or remediation program of the heavy metal laden waste. The aim of this study was to assess the potential of sunflower for phytoremediation of heavy metal polluted mine tailings. Phytoremediation is an emerging technology in the remediation of mine tailings that uses tolerant plant species to clean up contaminated sites. It uses plants with high biomass and sunflower has been identified as such. These plants can extract, transfer, sequester and stabilize a variety of metals through mechanisms such as phytoextraction, phytostabilization, phytoaccumulation and phytovolatilization. Pot experiments were conducted by growing sunflower (Helianthus annuus L.) in pyrite mine tailings and in agricultural soil as a control. The study showed that the concentration of Cu reduced from 40.76 mg/kg to 36.59 mg/kg, Zn reduced from 3.58 mg/kg to 3.49 mg/kg and Fe reduced from 23.70 mg/kg to 10 mg/kg respectively in the mine tailings after 6 weeks. Analysis of harvested sunflower (roots, stems, leaves) showed that sunflower could remove heavy metals from the tailings and the highest removal efficiency was 53.7% and the highest translocation factor was 0.25. It was concluded that sunflower has the potential to remediate contaminated mine tailings and that phytoremediation is a viable and efficient technology to treat soils contaminated with heavy metals.

Domestic Wastewater Treatment through the Application of Corchuros olitorius L. as Bio-Coagulant in Cagayan de Oro City, Philippines

This research paper presented the potential of Corchuros olitorius L.as a natural coagulant in the removal of turbidity,total suspended solids,and biochemical oxygen demand from the domestic wastewater of the University of Science and Technology of Southern Philippines.Optimization of the natural coagulant and synthetic coagulant was employed prior to the treatment design.The jar test method was used in the optimization and lab analysis including the gravimetric method,dilution technique,and digital measurements.The optimization results of Corchuros olitorius L.using the jar test method revealed better removal at a lower dosage of 50 mg/L and a higher settling time of 90 minutes.The characterization using FTIR analysis also suggests a functional group that influences coagulation activity.Using the optimum dose and optimum settling time,results with the different treatment designs showed the highest removal at pH 7 showed%BOD removal of 89.78%(A75C25);85.98%(A25C75);88.76%(A50C50).TSS removal measured values of 88.50%(A75C25),85.56%(A25C75),and 87.16%(A50C50),while turbidity removal of 83.47%(A75C25),80.27%(A25C75),and 80.27%(A50C50).Statistically,measured values differ between treatment designs.It is suggested to investigate removal efficiency in more varied pH conditions,different settling times,stirring speed,and other variables for future studies.

Effects of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as end product

The effect of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as the end product was studied by using a SBR. Experimental results indicated that the growth of nitrobacteria was inhibited and very high levels of nitrite accumulation at different salinities were achieved under the conditions of 25—28℃, pH 7.5? ?.0 , and the influent ammonia nitrogen of 40—70 mg/L when seawater flow used to flush toilet was less than 35%(salinity 12393 mg/L, Cl - 6778 mg/L) of total domestic wastewater flow, which is mainly ascribed to much high chlorine concentration of seawater. Results showed that high seawater salinity is available for short-range nitrification to nitrite as the end product. When the seawater flow used to flush toilet accounting for above 70% of the total domestic wastewater flow, the removal efficiency of ammonia was still above 80% despite the removal of organics declined obviously(less than 60%). It was found that the effect of seawater salinity on the removal of organics was negative rather than positive one as shown for ammonia removal.

A novel integrated step-feed biofilm process for the treatment of decentralized domestic wastewater in rural areas of China

For wastewater treatment in rural areas, a novel three-stage step-feed wastewater treatment system, combined with a drop-aeration biofilm process, was tested in the laboratory to investigate its performance in removing suspended solids （SS）, chemical oxygen demand （COD）, NH4＋-N, total nitrogen （TN）, and total phosphorus （TP）. The removal rates of SS, COD and NH4＋-N were 90%, 80%, and 90% in efluent concentrations less than 10 mg/L, 50 mg/L and 8 mg/L, respectively. The TP removal rate was less satisfactory. The C/N ratio in the raw wastewater was often less than 3.5, and the removal efficiency of TN was therefore limited. A carbon-release batch experiment was carried out to measure the feasibility of enhancing denitrification at low influent C/N ratios. The result showed that the C/N could be over 9.0 in the supernatant. Polymerase chain reaction denaturing gradient gel electrophoresis technology was used to reveal the changes in the bacterial community during different stages of the integrated step-feed biofilm process. The results showed that banding patterns and the distribution of dominant bands for the same experimental period in different aerobic zones were similar. Phylogenetic analysis indicated that lanes 10, 11 and 12, which presented three aerobic zones at the same operation period, had the closest phylogenetic relationship among the lanes.

Distribution and elimination of polycyclic musks in three sewage treatment plants of Beijing, China

The two representative polycyclic musks, 1-（5,6,7,8-tetrahydro-3,5,5,6,8,8-hexamethyl-2-naphthenyl）-ethanone （AHTN） and 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[g]-2-benzopyrane （HHCB）, were measured in aqueous samples and sludge samples of three sewage treatment plants （STPs） in Beijing, China using a gas chromatograph-mass spectrometry. The HHCB and AHTN concentration ranges in the influents were 1251.4-3003.8 ng/L and 111.9-286.3 ng/L, respectively. Meanwhile, the ranges of 492.8-1285.3 ng/L for HHCB and 47.3-89.3 ng/L for AHTN were present in the effluents. The musks in the sludges were three to four orders of magnitude higher than those in aqueous sewages. The removal efficiencies.of the two musks varied in the ranges of 41.7%- 70.1% for HHCB, and 25.5%-68.8% for AHTN. Adsorption onto suspended particulate matter played an important role in removing musks from the sewages. The HHCB/AHTN ratio along the treatment processes showed that the two musks had high similarity of removal from sewage by each reactor in STP. The musks in the effluent sewages may pose a low potential risk to aquatic environment in terms of the predicted-non-effect concentration. Nevertheless, considering the possible additive and synergistic effects with other compounds emitted via STPs, their bioconcentration and bioaccumulation in aquatic organisms and so on, it is essential to monitor these compounds in various compartments and to study their environmental fate.