Degradation of acephate using combined ultrasonic and ozonation method

The degradation of acephate in aqueous solutions was investigated with the ultrasonic and ozonation methods, as well as a combination of both. An experimental facility was designed and operation parameters such as the ultrasonic power, temperature, and gas flow rate were strictly controlled at constant levels. The frequency of the ultrasonic wave was 160 k Hz. The ultraviolet-visible(UV-Vis) spectroscopic and Raman spectroscopic techniques were used in the experiment. The UV-Vis spectroscopic results show that ultrasonication and ozonation have a synergistic effect in the combined system. The degradation efficiency of acephate increases from 60.6% to 87.6% after the solution is irradiated by a160 k Hz ultrasonic wave for 60 min in the ozonation process, and it is higher with the combined method than the sum of the separated ultrasonic and ozonation methods. Raman spectra studies show that degradation via the combined ultrasonic/ozonation method is more thorough than photocatalysis. The oxidability of nitrogen atoms is promoted under ultrasonic waves. Changes of the inorganic ions and degradation pathway during the degradation process were investigated in this study. Most final products are innocuous to the environment.     

超声强化臭氧降解高浓度苯酚废水研究

超声及其组合技术对有机物废水降解是一种新兴的污水处理技术,有着广阔的发展前景和应用市场.对超声强声动力强化臭氧降解高浓度苯酚废水过程中的臭氧通气量、溶液的pH值、反应时间及溶液的初始浓度进行了实验研究,并对单一臭氧和超声强化臭氧降解效果进行了比较.结果表明:由于超声独特的物理、化学效应为臭氧降解提供了极端的物理、化学环境,二者协同作用使得反应进行彻底,COD去除率可达100%.     

低强度超声场促进剩余污泥好氧消化

为了提高剩余污泥好氧消化效率,在消化过程中对剩余污泥进行超声辐射,声强为0.53 W/cm2,频率28 kHz,分别选用0.045 W/mL、0.09 W/mL两个功率密度,每次超声辐射时间20 min或10 min,辐射频次选用4次或2次,组成4个组合.研究表明,未经超声处理的污泥在消化第17天达到稳定,而经超声作用的污泥消化稳定时间较前者提前3～7 d.在相同好氧消化时间内,经超声波处理后污泥能获得更高的有机物降解率.同时对超声波促进污泥好氧消化工艺进行了工程经济评价.     

Effective sludge solubilization treatment by simultaneous use of ultrasonic and electrochemical processes.

Sludge disintegration treatment by using simultaneously ultrasonic irradiation and electrolysis was investigated experimentally. A lab-scale diaphragm cell irradiated with ultrasound at a constant oscillating frequency of 20 kHz was used as a reactor. The batch experiments were carried out under different conditions of electric outputs of the ultrasonic generator, electric current for the electrolysis and different initial SS concentrations. A simultaneous treatment in the cathodic compartment without any chemical doses considerably facilitated the sludge solubilization, compared to the sonication alone. An increase in the electric current up to 400 mA under a constant ultrasonic density decreased the specific energy by 55% within the experimental range. The specific energy consumption was also reduced when the initial SS concentration increased. In addition, before carrying out the simultaneous treatment, a brief electrolysis was effective for further reduction of the specific energy and the acceleration of soluble COD generation.     

功率超声的声学参数对废水处理效果的影响

从功率超声在水处理中的空化机理入手,论述了国内外在应用功率超声进行废水处理时频率、声功率/声强以及声化学反应器的物理结构(实质是声场分布)等声学参数对处理效果的影响。结论表明,对不同的废水溶液存在超声降解的最佳频率和最佳声功率/声强;双频或多频超声较单频超声在处理同一废水溶液时有明显的协同效应;混响场中的空化阈值比行波场低,相同条件下更利于声化学产额的提高。分析了目前超声水处理技术研究不够深入的原因,并对其发展进行了讨论和展望。     

低强度超声提高污泥活性的运行条件优化

为优化超声处理提高污泥活性的运行条件,考察了超声波的频率、强度、作用时间和污泥浓度等因素的影响.结果表明,采用35 kHz和61 kHz两种低频率超声波先后对污泥进行强化处理时,在总处理时间一致的条件下,超声波的顺序和时间分配对污泥活性的提高程度及活性的延续时间无显著差别;采用固定频率的超声波处理时,提高超声波的功率和延长超声作用时间都可以显著提高污泥活性;在功率和作用时间恒定的条件下,增大MLSS对单位质量污泥活性的提高程度影响较小,因此,对污泥先进行浓缩再超声处理可大大提高超声效率.     

Effects and mechanism of ozonation for degradation of sodium acetate in aqueous solution

The degradation efficiencies and mechanism of ozonation for the degradation of sodium acetate in aqueous solution were investigated under atmospheric pressure at room temperature (293 K). The effects of the initial pH value, reaction time, and concentrations of HCO3-, CO32-, CaCl2, and Ca(OH)2 on the removal rate of chemical oxygen demand (COD) were studied. The results indicated that ozonation obviously improved the degradation rate of sodium acetate when the pH value of the solution was not less than 8.5. A suitable long reaction time may be helpful in increasing the COD removal rate, and a removal rate of 36.36% can be obtained after a 30-minute treatment. The COD removal rate increased firstly and decreased subsequently with the increase of the HCO3- concentration (from 0 to 200 mg/L), and under the same experimental condition it reached the optimum 34.66% at the HCO3- concentration of 100 mg/L. The COD removal rate was 5.26% lower when the concentration of was 200 mg/L than when there was no HCO3-. The COD removal rate decreased by 15.68% when the CO32- concentration increased from 0 to CO32- 200 mg/L. has a more obvious scavenging effect in inhibiting the formation of hydroxyl radicals than HCO3-. CaCl2 and Ca(OH)2 could increase the degradation efficiency of sodium acetate greatly, and the COD removal rates reached 65.73% and 83.46%, respectively, after a 30-minute treatment, 29.37% and 47.10% higher, respectively, than with single ozone oxidation. It was proved that the degradation of sodium acetate in the ozonation process followed the mechanism of oxidization with hydroxyl free radicals (·OH).     

Ultrasound as a pre-oxidation for biological landfill leachate treatment.

In this study, the effects of low energy ultrasound irradiation on landfill leachate treatment by means of sequencing bath reactor were investigated. The aim of this work was to estimate the influence of leachate irradiation time on aerobic treatment efficiency. The sonification of the leachate was carried out in static conditions using the disintegrator UD-20. The field frequency of 22 kHz (the power output equals to 180 W) and amplitude of 12 microm was applied. The sonification time was changed in the range of 30-140 s. It was found that ultrasonic pretreatment enhances the subsequent aerobic digestion resulting in a better degradation of landfill leachate. The sonification of raw leachate leads to enhancement of COD and ammonia removal as compare to experiment without ultrasound.     

超声引发聚苯乙烯磺酸钠的降解

用低功率、高频率的超声波对水溶液中的聚苯乙烯磺酸钠进行降解,研究溶液浓度、pH值等对降解反应的影响,用凝胶色谱法测定降解产物的分子量及其分布,用红外光谱法以及紫外分光光度法表征了降解过程中的产物结构变化,用2,2-二苯基-1-苦肼基(DPPH)对降解过程中产生的自由基进行捕捉,证实降解反应经历了自由基历程。     

Photocatalytic degradation of p-nitrophenol by zinc oxide particles

The degradation of p-nitrophenol (PNP) by ZnO particles has been studied. With increasing PNP loading the degradation rate decreased. The mineralization of PNP was rather slow compared with the degradation. With a decrease in particle diameter or an increase in surface area, the degradation rate significantly increased. The degradation capability with solar irradiation was found to be superior to UV light irradiation. It was found that 30 mg L(-1) of PNP was completely degraded by solar light with the accumulated UV light of around 23 kJ L(-1) at ZnO dosage of 5 g L(-1). The degradation PNP by ZnO with UV light or solar light was faster than that by TiO(2).     

超声辐照降解水中氯苯的研究

研究了超声辐照工艺技术降解水中氯苯的效果和影响因素 ,包括声强、溶液pH值、初始浓度、溶解气体和自由基清除剂 ,并探讨了氯苯超声降解的机理。试验结果表明氯苯的超声降解主要在空化泡内热解 ,降解效果好     

The use of a range of ultrasound frequencies to reduce colouration caused by dyes

The formation of hydrogen peroxide and the degree of decolourisation of six different dyes as a result of sonication over several ultrasonic frequencies (20, 40, 380, 512, 850, 1,000 and 1,176 kHz) was investigated and correlated. It was found that the highest levels of hydrogen peroxide and also the greatest amount of decolourisation occurred at 850 kHz. 380 and 512 kHz also resulted in some decolourisation, however higher and lower ultrasonic frequencies were not effective.     

UASB reactor for domestic wastewater treatment at low temperatures: a comparison between a classical UASB and hybrid UASB-filter reactor.

The performance of an upflow anaerobic sludge blanket (UASB) reactor and a hybrid UASB-filter reactor was investigated and compared for the treatment of domestic wastewater at different operational temperatures (28, 20, 14 and 10 degrees C) and loading rates. For each temperature studied a constant CODt removal was observed as long as the upflow velocity was lower than 0.35 m/h. At these upflow velocities similar removals were observed for both reactor types at 28 and 20 degrees C, 82 and 72% respectively. However, at 14 and 10 degrees C the UASB reactor showed a better COD removal (70% and 48%, respectively) than the hybrid reactor (60% and 38%). COD removal resulted from biological degradation and solids accumulation in the reactors. At 28 degrees C, a constant 200 g sludge mass was observed in both reactors and COD removal was attributed to biological degradation only. At lower temperatures, solids accumulation was observed in addition to biological degradation with an increase in reactor sludge as the temperature decreased. The decrease in biological degradation at lower temperatures was offset by solids accumulation and explains the similar overall COD removal efficiency observed at 28 degrees C, 20 degrees C and 14 degrees C. The decrease in temperature was also followed by an increase in the effluent TSS concentration in both reactors. At 14 and 10 degrees C a lower effluent TSS concentration and better performance was observed in the UASB reactor.     

Quantitative study of degradation coefficient of pollutant against the flow velocity

The pollutant degradation coefficient is one of the key parameters to describe the water quality change, for establishing a reasonable water quality model and to determine the water carrying capacity and the environmental capacity. In this research, the environmental channel experiment is conducted to simulate the degradation evolution of the COD and NH3-N under different flow velocity conditions in typical pollution water. It is shown that the processes of the COD and the NH3-N's concentration over time are quite consistent with the first-order kinetic equation and the degradation coefficients increase with the increase of the flow velocity. When the flow velocity varies from 0 m?s-1 to 0.87 m?s-1, the degradation coefficients of the COD and NH3-N increase from 0.011 d-1 to 0.071 d-1 and 0.038 d-1 to 0.258 d-1, respectively. Moreover, the COD and NH3-N's degradation coefficients both have excellent correlation with the reaction time. There is a good linear relationship between the COD degradation coefficient and the flow velocity as well as a good power exponential function between the NH3-N degradation coefficient and the flow velocity. The comparative analysis of the Youth canal prototype monitoring and the calculation results shows that the quantitative formula obtained from the indoor water channel experiments gives results very close to the prototype observation results, which could reflect the degradation of pollutants in river water with varying flow velocity.     

Effect of low power ultrasound on aerobic/anoxic digestion of activated sludge

The effect of low power ultrasound on aerobic/anoxic digestion of activated sludge was investigated. First, dehydrogenate activity (DHA) and special oxygen uptake rate (SOUR) were detected to indicate the change of biological activity of sludge induced by ultrasound. Single-factor experiments showed that when the ultrasonic frequency was 28 kHz, the optimal ultrasonic density and exposure time were 0.15 W/mL and 10 min, respectively. Through orthogonal tests, the optimal ultrasonic parameters for aerobic/anoxic digestion were found to be a ultrasonic density of 0.15 W/mL, ultrasonic exposure time of 10 min and interval time of 12 h. The aerobic/anoxic digestion was improved by ultrasonic pretreatment, the VSS reduction at the optimal conditions was increased by 35.73%, compared with the control. It can be concluded that low power ultrasonic pretreatment is a valid method for improving aerobic/anoxic biodegradability of activated sludge.     

The effects of hydraulic retention time and feed COD concentration on the rate of hydrolysis of primary sewage sludge under methanogenic conditions.

A series of completely mixed methanogenic anaerobic digesters have been operated to determine the rate of hydrolysis of primary sewage sludge. The hydraulic retention time was reduced from 60 d to when the system failed (approximately 5 d), while the feed COD concentration was 40, 25, 13 and 2 gCOD/L. A steady state model based on first order kinetics was developed to simulate the hydrolysis rate at each retention time and feed concentration. With the mean value for the hydrolysis rate constant (0.992 +/- 0.492 d(-1)), this model was able to accurately predict the effluent COD for all steady state operating conditions. However, the effluent COD concentration was relatively insensitive to the exact value for this constant. The model provides a framework for analysis of anaerobic digestion experimental data, to enable meaningful comparisons.     

Fenton试剂在微波条件下处理稻壳热解发电含酚废水的试验

采取试验手段,研究在微波条件下用Fenton试剂处理含酚废水的效果,探讨H2O2质量浓度、FeSO4质量浓度、pH值、反应时间和微波功率等因素对稻壳热解发电废水中COD、挥发酚及色度去除率的影响,并进行不同条件下Fenton反应的对比试验。结果表明,在微波条件下,Fenton试剂能快速降解含酚废水,处理后水样的COD去除率超过73%,挥发酚去除率超过99%,色度去除率接近50%。该含酚废水的最佳处理条件是:H2O2质量浓度为1500 mg/L,FeSO4质量浓度为100 mg/L,pH值为3,反应时间为10 min,微波功率为400 W。     

十六醇和乙醇复配体系水分蒸发抑制剂研究

我国西北地区干燥少雨、蒸发量大,蓄水工程蒸发损失了大量的水资源。为研究干旱地区的水资源保护措施,以十六醇和乙醇为分子膜基材,采用超声波分散技术,制备了一种非均相体系水分蒸发抑制剂。对两种醇的比例、超声处理时间及功率、抑制剂加入量对抑制效果的影响进行了研究。结果表明:十六醇与乙醇比例为1∶6,超声处理功率6 k Hz,时间为25 min,每处理30 s停歇10 s的情况下,水分蒸发抑制剂效果最佳,24 h抑制率可达45.3%,抑制剂用于水面后,水体含氧量与自然条件下水体含氧量大致相同,不会对水生动植物的生长产生影响。所配抑制剂对于减少干旱地区水资源损失具有重大意义,可带来巨大的经济效益和社会效益。     

Some observations on the effects of accumulated benthic sludge on the behaviour of waste stabilisation ponds.

The effect of accumulated bottom sludge on water column characteristics was studied in two pilot-scale ponds. Parameters measured were ammonia, nitrate, phosphate, COD, suspended solids, dissolved oxygen (DO), temperature and light intensity. The de-sludged pond showed a stronger correlation between DO, light intensity, nutrients and suspended solids with the controlling factor being availability of nitrogen. This was less apparent in the pond with sludge where nutrient levels were higher and more complex mechanisms controlled biomass concentration. Water column characteristics in the two ponds converged rapidly in 7-10 weeks, however, due to accumulation of fresh sludge.     

Hydrodynamic effects on contaminants release due to rususpension and diffusion from sediments

Hydrodynamic effects play a very important role in the contaminants release from sediments. Experiments were perfor-med to study contaminants releasing characteristics due to resuspension. The time-dep...