Inactivation of MS2 bacteriophage by streamer corona discharge in water

Electrical discharge processes are emerging as water treatment technologies applicable to both the degradation of organic contaminants as well as inactivation of pathogens. Particularly as a disinfection technology, electrical discharge processes do not produce toxic byproducts, and effectively inactivate a wide spectrum of microorganisms by multiple lethal actions generated by the formation of plasma channels. This study demonstrates the inactivation of a virus using the streamer corona discharge process (SCDP) with MS2 phage as a surrogate. A rapid inactivation of MS2 phage (i.e., approximately 4 log inactivation in 5 min) was observed in all experimental runs conducted. Discharge conditions such as applied voltage and storage capacitance significantly affected the inactivation efficiency of MS2 phage, whereas the influence of water quality parameters was minor. In order to elucidate the mechanism of MS2 phage inactivation, potentially lethal factors that can be generated by the SCDP were selected, and their roles in the inactivation of MS2 phage were examined. As a result, effects of UV radiation, chemical oxidants, and pulsed electric fields were found to be insignificant. The shockwave generated upon plasma channel formation appears to be the most important factor responsible for MS2 phage inactivation.     

How to optimize hollow-fiber submerged membrane bioreactors

Membrane fouling is linked to reversible or irreversible accumulation of macromolecules and solids on membrane surfaces and to the irreversible adsorption inside pores. If reversible accumulation can be controlled by filtering in subcritical conditions, then adsorption could also be minimized by reducing the soluble organic matter [extracellular polymeric substances, soluble microbial products (SMP)]. This research shows how the choice of operating parameters related to biological reaction (solid retention time and the organic loading rate) can influence the process rate and the by-product (SMP) production. It also illustrates how suspension characteristics and membrane aeration can influence membrane fouling control according to the hollow fiber configuration and to the different scales of observation. The investigations were based on the definition of different fouling level and fine-tuning of a model to better understand the effects of operating parameters on membrane bioreactor filtration.     

Experimental study and modelling of zinc adsorption by granular activated carbon and natural zeolite

The metal removal capability of Granular Activated Carbon (GAC) and natural zeolite is evaluated in this study using zinc as a model adsorbate. The equilibrium and kinetic characteristics of zinc adsorption on GAC and natural zeolite were studied in batch stirred tank experiments. The adsorption data for both systems were fitted by Langmuir, Freundlich, Langmuir-Freundlich, and Redlich-Peterson models. The parameters in the adsorption isotherms were estimated from the experimental equilibrium data using MATLAB. Using these data the best isotherm can be selected. The effect of initial concentration on the transient behaviour of zinc removal by GAC and natural zeolite was investigated. In this work two surface reaction models, namely a second order reversible reaction model and a second order irreversible reaction model for describing Zn(II) removal by GAC and natural zeolite, were employed. Modelling studies using two different second order surface reaction models demonstrated that it is very difficult to come to a general conclusion about which model has better ability.     

改性高炉渣对染料的吸附动力学及热力学研究

以高炉渣和壳聚糖为原料,制备了高温改性高炉渣-壳聚糖复合吸附剂(TBFSC)和盐酸改性高炉渣-壳聚糖复合吸附剂(ABFSC),考察了2种吸附剂对酸性蒽醌蓝和活性艳红K-2BP的吸附性能,研究了吸附过程的等温吸附特征、吸附动力学和热力学。结果表明,2种染料在TBFSC和ABFSC上的吸附更好地符合Langmuir等温方程,表观二级动力学模型能够很好地描述TBFSC和ABFSC的吸附动力学行为。对于染料在TBFSC上的吸附,粒子内扩散过程和液膜扩散过程是该吸附的速控步骤,而液膜扩散过程为ABFSC吸附染料的速控步骤。热力学参数表明,TBFSC和ABFSC对两种染料的吸附都是自发进行的物理吸附,吸附过程均无配位基交换、化学键等强的作用力。     

Removal of indigenous compounds to determine maximum capacities for adsorption of phenanthrene by sediments

The maximum amounts of phenanthrene that can be adsorbed in both the slowly desorbing domain and the very slowly desorbing domain of two sediments were determined. To this end, native compounds were removed by mild solvent extraction, heating, or extraction by Tenax. Maximum capacities for adsorption of phenanthrene in the very slowly desorbing domain after removal of native compounds by heating the sediments at 300 degrees C for 24 h were comparable to those after extraction with Tenax at 60 degrees C for 13 days. Mild solvent extraction resulted in lower capacities due to incomplete removal of native compounds. For the slowly desorbing domain, heating the sediment or performing mild solvent resulted in maximum capacities for adsorption exceeding those obtained after non-invasive extraction with Tenax. That was taken to indicate alterations of the sorbent by the solvent or high temperature resulting in an overestimation of the maximum capacities for adsorption. It is concluded that for the determination of maximum capacities of adsorption in the very slowly desorbing domain, removal of native compounds by heating at 300 degrees C for 24 h is reliable and practical. However, for the determination of maximum adsorption capacities of the slowly desorbing domain, native compounds have to be removed by a non-invasive technique such as extraction by Tenax.     

The effect of dissolved glyphosate upon the sorption of copper by three selected soils

The effect of the pesticide glyphosate (GPS) on adsorption processes of copper onto three soils of different characteristics has been studied. Cu adsorption decreases in general with increasing GPS concentration in solution, due principally to the lower equilibrium pHs, although this is not the only variable affecting copper adsorption. For the same pH values, Cu adsorption is higher in two of the three soils in the presence of GPS, but for the third soil, Cu adsorption is higher in the absence of GPS. This behavior is explained by the possibility of GPS adsorption on these soils and by the formation of Cu-GPS complexes in solution. The soils showing a higher Cu adsorption in the presence of GPS than in its absence for the same pH are able to adsorb this pesticide. In these soils, copper can be adsorbed directly on the soil surfaces, and also through the formation of bonds with GPS previously adsorbed. The third soil was not able to adsorb GPS. Consequently, all the pesticide remained in solution, forming strong Cu complexes with low tendency to be adsorbed on this soil. For this reason, the concentration of free Cu in solution is drastically reduced, and the adsorption of copper on this soil is lower.     

pH对活化前后废弃铁铝泥吸附不同种磷动力学的影响

实验研究了300℃热活化前后的给水厂废弃铁铝泥（R-FARs和H300-FARs）对正磷酸盐、聚磷酸盐和有机磷酸盐的吸附动力学特性,并考察pH对不同磷吸附动力学的影响。结果表明,pH对不同磷吸附动力学过程的影响趋势相似,即低pH有利于吸附。准二级动力学模型能够更真实地反映不同磷在R-FARs和H300-FARs的吸附动力学行为,由拟合结果可知焦磷酸盐和六肌醇磷酸盐的初始吸附速率相对较大,而甘油磷酸盐最小;且活化作用明显提高了不同磷的初始吸附速率,并减弱了pH对初始吸附速率的影响。不同磷的吸附速率受到液膜扩散、颗粒内扩散和吸附反应三者共同控制,其中吸附反应是主要的控制步骤。     

Effects of wastewater disinfection on waterborne bacteria and viruses.

Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other waterborne microorganisms (e.g., microbial pathogens). Undisinfected effluent samples from several municipal wastewater treatment facilities were collected for analysis. Facilities were selected to provide a broad spectrum of effluent quality, particularly as related to nitrogenous compounds. Samples were subjected to bench-scale chlorination and dechlorination and UV irradiation under conditions that allowed compliance with relevant discharge regulations and such that disinfectant exposures could be accurately quantified. Disinfected samples were subjected to a battery of assays to assess the immediate and long-term effects of wastewater disinfection on waterborne bacteria and viruses. In general, (viable) bacterial populations showed an immediate decline as a result of disinfectant exposure; however, incubation of disinfected samples under conditions that were designed to mimic the conditions in a receiving stream resulted in substantial recovery of the total bacterial community. The bacterial groups that are commonly used as indicators do not provide an accurate representation of the response of the bacterial community to disinfectant exposure and subsequent recovery in the environment. UV irradiation and chlorination/dechlorination both accomplished measurable inactivation of indigenous phage; however, the extent of inactivation was fairly modest under the conditions of disinfection used in this study. UV irradiation was consistently more effective as a virucide than chlorination/dechlorination under the conditions of application, based on measurements of virus (phage) diversity and concentration. Taken together, and when considered in conjunction with previously published research, the results of these experiments illustrate several important limitations of common disinfection processes as applied in the treatment of municipal wastewaters. In general, it is not clear that conventional disinfection processes, as commonly implemented, are effective for control of the risks of disease transmission, particularly those associated with viral pathogens. Microbial quality in receiving streams may not be substantially improved by the application of these disinfection processes; under some circumstances, an argument can be made that disinfection may actually yield a decrease in effluent and receiving water quality. Decisions regarding the need for effluent disinfection must account for site-specific characteristics, but it is not clear that disinfection of municipal wastewater effluents is necessary or beneficial for all facilities. When direct human contact or ingestion of municipal wastewater effluents is likely, disinfection may be necessary. Under these circumstances, UV irradiation appears to be superior to chlorination in terms of microbial quality and chemistry and toxicology. This advantage is particularly evident in effluents that contain appreciable quantities of ammonia-nitrogen or organic nitrogen.     

Persistence and fate of 17beta-estradiol and testosterone in agricultural soils

Steroidal hormones are constantly released into the environment by man-made and natural sources. The goal of this study was to examine the persistence and fate of 17beta-estradiol and testosterone, the two primary natural sex hormones. Incubation experiments were conducted under aerobic and anaerobic conditions using [4-(14)C]-radiolabeled 17beta-estradiol and testosterone. The results indicated that 6% of 17beta-estradiol and 63% of testosterone could be mineralized to (14)CO(2) in native soils under aerobic conditions. In native soils under anaerobic conditions, 2% of testosterone and no 17beta-estradiol was methanogenized to (14)CH(4). Essentially, no mineralization of either testosterone or 17beta-estradiol to (14)CO(2) occurred in autoclaved soils under aerobic or anaerobic condition. Results also indicated that 17beta-estradiol could be transformed to an unidentified polar compound through abiotic chemical processes; however, 17beta-estradiol was only oxidized to estrone via biological processes. The TLC results also indicated that testosterone was degraded, not by physical-chemical processes but by biological processes. Results also indicated that the assumed risks of estrogenic hormones in the environment might be over-estimated due to the soil's humic substances, which can immobilize majority of estrogenic hormones, and thereby reduce their bioavailability and toxicity.     

Thermal treatment for pathogen inactivation as a risk mitigation strategy for safe recycling of organic waste in agriculture

Thermal treatment at temperatures between 46.0°C and 55.0°C was evaluated as a method for sanitization of organic waste, a temperature interval less commonly investigated but important in connection with biological treatment processes. Samples of dairy cow feces inoculated with Salmonella Senftenberg W775, Enterococcus faecalis, bacteriophage ?X174, and porcine parvovirus (PPV) were thermally treated using block thermostats at set temperatures in order to determine time-temperature regimes to achieve sufficient bacterial and viral reduction, and to model the inactivation rate. Pasteurization at 70°C in saline solution was used as a comparison in terms of bacterial and viral reduction and was proven to be effective in rapidly reducing all organisms with the exception of PPV (decimal reduction time of 1.2 h). The results presented here can be used to construct time-temperature regimes in terms of bacterial inactivation, with D-values ranging from 0.37 h at 55°C to 22.5 h at 46.0°C and 0.45 h at 55.0°C to 14.5 h at 47.5°C for Salmonella Senftenberg W775 and Enterococcus faecalis, respectively and for relevant enteric viruses based on the ?X174 phage with decimal reduction times ranging from 1.5 h at 55°C to 16.5 h at 46°C. Hence, the study implies that considerably lower treatment temperatures than 70°C can be used to reach a sufficient inactivation of bacterial pathogens and potential process indicator organisms such as the ?X174 phage and raises the question whether PPV is a valuable process indicator organism considering its extreme thermotolerance.     

Removal of carbonyl sulfide using activated carbon adsorption

Wastewater treatment plant odors are caused by compounds such as hydrogen sulfide (H2S), methyl mercaptans, and carbonyl sulfide (COS). One of the most efficient odor control processes is activated carbon adsorption; however, very few studies have been conducted on COS adsorption. COS is not only an odor causing compound but is also listed in the Clean Air Act as a hazardous air pollutant. Objectives of this study were to determine the following: (1) the adsorption capacity of 3 different carbons for COS removal; (2) the impact of relative humidity (RH) on COS adsorption; (3) the extent of competitive adsorption of COS in the presence of H2S; and (4) whether ammonia injection would increase COS adsorption capacity. Vapor phase react (VPR; reactivated), BPL (bituminous coal-based), and Centaur (physically modified to enhance H2S adsorption) carbons manufactured by Calgon Carbon Corp. were tested in three laboratory-scale columns, 6 in. in depth and 1 in. in diameter. Inlet COS concentrations varied from 35 to 49 ppmv (86-120 mg/m3). RHs of 17%, 30%, 50%, and 90% were tested. For competitive adsorption studies, H2S was tested at 60 ppmv, with COS at 30 ppmv. COS, RH, H2S, and ammonia concentrations were measured using an International Sensor Technology Model IQ-350 solid state sensor, Cole-Parmer humidity stick, Interscan Corp. 1000 series portable analyzer, and Drager Accuro ammonia sensor, respectively. It was found that the adsorption capacity of Centaur carbon for COS was higher than the other two carbons, regardless of RH. As humidity increased, the percentage of decrease in adsorption capacity of Centaur carbon, however, was greater than the other two carbons. The carbon adsorption capacity for COS decreased in proportion to the percentage of H2S in the gas stream. More adsorption sites appear to be available to H2S, a smaller molecule. Ammonia, which has been found to increase H2S adsorption capacity, did not increase the capacity for COS.     

Paraquat adsorption, degradation, and remobilization in tropical soils of Thailand

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with Kf values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0-5 cm layer under field conditions and in the 0-1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT50 at 36-46 days and DT90 around 119-152 days.     

The effect of calcium and pH on nickel accumulation in and rhizotoxicity to pea (Pisum sativum L.) root-empirical relationships and modeling

The accumulation and rhizotoxicity of Ni to pea were investigated. Calcium, H, and Ni competed for root-binding sites with high pH and low Ca favoring more Ni accumulation. At low pH, Ca accumulation is the key factor determining root growth, while at medium to high pH, root elongation is more sensitive to Ni concentration. The tissue concentration of Ni and Ca ([Ni]t or [Ca]t, μmol g⁻¹ dry root) can be predicted from total dissolved Ni ([Ni]_T, μM), pH, and total dissolved Ca ([Ca]_T, mM) by two approaches. Approach 1 is the empirical equations [Ni]t = (0.361 pH-0.695[Ca]_T)*[Ni]_T and [Ca]t = 8.29 pH + 10.8 [Ca]_T. The second approach involves a two-step model. The surface-bound Ni and Ca are estimated from a surface adsorption model with binding constants derived from independent ion adsorption experiments. Then transfer functions are used to predict internal root Ni and Ca accumulation.     

Theoretical analysis of deviations from local equilibrium during sorbing solute transport through idealized stratified aquifers

This paper studies the spreading characteristics of reactive solute plumes in idealized stratified aquifers. The aquifer consists of two layers having different permeabilities with flow parallel to the stratification. The solute is assumed to adsorb onto the aquifer solids according to a first-order reversible kinetic rate law; the adsorption parameters are spatially uniform. We use the Aris moment method to examine analytically the time evolution of the lower-order spatial moments of the depth-averaged contaminant plume for an instantaneous input of mass. The results demonstrate that sorption kinetics cause the total dissolved mass and average velocity of the contaminant plume to decrease with increasing travel time. The plume variance is shown to depend upon three factors: intra-layer longitudinal dispersion, intra-layer kinetics, and vertical averaging. The results indicate that the relative importance of sorption kinetics diminishes as the permeability contrast between the layers increases. We present a simple criterion that can be used to assess the applicability of the local equilibrium assumption in idealized stratified systems.     

城市污水再生处理过程中壬基酚的迁移转化行为研究

采用SPE-GC-MSD-SIM方法,分析了壬基酚在污水再生处理全过程中的迁移转化行为与归宿.研究表明,在污水二级生物处理流程中,壬基酚主要来源为原污水和泥区回流液;壬基酚的去除途径有一沉池生污泥的吸附迁移作用和曝气池单元的生物降解转化作用,其中一沉池生污泥的吸附去除29.8%,曝气池生物降解54.4%,NP总去除率为84.2%.絮凝、过滤和消毒的污水再生深度处理工艺对壬基酚的迁移转化作用不明显.     

Competition for adsorption between added phenanthrene and in situ PAHs in two sediments

A study was performed on the influence of the addition of a relatively large amount of phenanthrene to two in situ contaminated sediments on the fractions of native PAHs in both the slowly desorbing domain and the very slowly desorbing domain in comparison to the undisturbed situation. Added phenanthrene was found to be present in both the slowly desorbing domain and the very slowly desorbing domain. The extent of removal of native PAHs from the very slowly desorbing domain induced by the presence of a large excess of phenanthrene was in line with expectations based on the incubation time and the rate constants for desorption of native PAHs from the very slowly desorbing domain. In contrast, the addition of phenanthrene did not result in a removal of native PAHs from the slowly desorbing domain. This was tentatively explained by assuming that native PAHs in the slowly desorbing domain are at adsorption sites with dimensions specific to each PAH and which are, therefore, less suited to other PAHs.     

Physical and chemical regeneration of zeolitic adsorbents for dye removal in wastewater treatment

Natural zeolite and synthetic zeolite, MCM-22, were employed as effective adsorbents for a basic dye, methylene blue, removal from wastewater. Two methods, Fenton oxidation and high temperature combustion, have been used for regeneration of used materials. It is found that MCM-22 exhibits equilibrium adsorption at 1.7 x 10(-4) mol g(-1), much higher than the adsorption of natural zeolite (5 x 10(-5) mol g(-1)) at initial dye concentration of 2.7 x 10(-5)M and 30 degrees C. Solution pH will affect the adsorption behaviour of MCM-22. Higher solution pH results in higher adsorption capacity. The regenerated adsorbents show different capacity depending on regeneration technique. Physical regeneration by high temperature combustion will be better than chemical regeneration using Fenton oxidation in producing effective adsorbents. Regeneration of MCM-22 by high temperature treatment can make the adsorbent exhibit comparable or superior adsorption capacity as compared to the fresh sample depending on the temperature and time. The optimal temperature and time will be 540 degrees C and 1h. The Fenton oxidation will recover 60% adsorption capacity. For natural zeolite, regeneration can not fully recover the adsorption capacity with the two techniques and the regenerated natural zeolites by the two techniques are similar, showing 60% adsorption capacity of fresh sample. Kinetic studies indicate that the adsorption follows pseudo-second-order kinetics.     

Competitive adsorption of alkylbenzene and water vapors on predominantly mineral surfaces

Competitive adsorption of ethylbenzene (EB) and water on bentonite and of p-xylene (pXYL) and water on kaolin and silica gel was studied using a technique that allowed the amount of adsorbed water and alkylbenzene to be measured independently. EB adsorption on bentonite was not affected by water at relative humidities (RH) near 0.23 but was reduced significantly at RH's near 0.50. pXYL adsorption on kaolin and silica gel decreased with increasing RH, especially above a RH of about 0.2. Increasing RH not only decreased the amount of alkylbenzene adsorption but also resulted in a change from Type-II adsorption isotherms to ones that were essentially linear. Linear isotherms for the adsorption of hydrophobic organic compounds on hydrated soil have generally been attributed to partitioning into organic carbon (OC). However, since the clays and oxide used here had very low to trace amounts of OC, it is suggested that processes involving only mineral surfaces can give rise to linear isotherms. Based on solubility considerations alone, partitioning of EB and pXYL into adsorbed water films was not considered to be an important adsorption mechanism in this study. The effect of cation hydration on the amount of water adsorbed from a mixture of water and pXYL vapors was evaluated by comparing adsorption on Li- and Na-saturated kaolin.     

Paraquat Adsorption,Degradation, and Remobilization in Tropical Soils of Thailand

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with K _f values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0–5 cm layer under field conditions and in the 0–1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT₅₀ at 36–46 days and DT₉₀ around 119–152 days.     

A geometric approach to determine adsorption and desorption kinetic constants

A geometric method based on Langmuir kinetics has been derived to determine adsorption and desorption kinetic constants. In the conventional procedure, either the adsorption kinetic constant (k(a)c) or desorption kinetic constant (k(d)c) is found from kinetic experiments and the other is calculated by their correlation with the equilibrium constant, i.e, k(d)c = Kcon/k(a)c, where Kcon has been known from equilibrium studies. The determined constants (Kcon, k(a)c, k(d)c), if based only on the conventional procedure, may not be accurate due to their mathematical dependence. Therefore, the objectives of this study are applying a geometric approach to directly determine Langmuir kinetic constants and describe adsorption behavior. In this approach, both adsorption kinetic constant (k(a)g) and desorption kinetic constant (k(d)g) are obtained only from data of kinetic experiments, and a geometric equilibrium constant (Kgeo) is calculated by Kgeo = k(a)g/k(d)g. The deviation between Kgeo and Kcon can prove the accuracy of k(a)g and k(d)g which were determined by this method. This approach was applicable to selenate, selenite and Mg2+ adsorption onto SiO2 regardless of whether the adsorbate formed inner- or outer-sphere complexes. However, this method showed some deviation between Kcon and Kgeo for Mn2+ adsorption because of the formation of surface Mn(II)-hydroxide clusters, which was inconsistent with the basic assumption of this method of monolayer adsorption.