Combination of ozonation with conventional aerobic oxidation for distillery wastewater treatment

Laboratory-scale experiments were conducted in order to investigate the effect of ozone as pre-aerobic treatment and post-aerobic treatment for the treatment of the distillery wastewater. The degradation of the pollutants present in distillery spent wash was carried out by ozonation, aerobic biological degradation processes alone and by using the combinations of these two processes to investigate the synergism between the two modes of wastewater treatment and with the aim of reducing the overall treatment costs. Pollutant removal efficiency was followed by means of global parameters directly related to the concentration of organic compounds in those effluents: chemical oxygen demand (COD) and the color removal efficiency in terms of absorbance of the sample at 254 nm. Ozone was found to be effective in bringing down the COD (up to 27%) during the pretreatment step itself. In the combined process, pretreatment of the effluent led to enhanced rates of subsequent biological oxidation step, almost 2.5 times increase in the initial oxidation rate has been observed. Post-aerobic treatment with ozone led to further removal of COD along with the complete discoloration of the effluent. The integrated process (ozone-aerobic oxidation-ozone) achieved approximately 79% COD reduction along with discoloration of the effluent sample as compared to 34.9% COD reduction for non-ozonated sample, over a similar treatment period.     

Application of cavitational reactors for water disinfection: current status and path forward

Cavitational reactors are a novel and promising form of multiphase reactors, based on the principle of release of large magnitude of energy due to the violent collapse of the cavities. An overview of cavitational reactors in the specific area of water disinfection, in terms of the basic mechanism, different reactor designs including recommendations for optimum operating parameters and applicability of the cavitation phenomena for disinfection of different micro-organisms have been presented. A design of a pilot scale sonochemical reactor has been presented, which forms the basis for development of industrial scale reactors. Economic analysis for comparison of cavitation phenomena with other conventional techniques of disinfection has been discussed. It appears that though cavitation is quite successful in treatment of water at laboratory scale operations, comparatively higher cost of treatment as compared to the conventional chemical methods is a hindrance in its industrial scale application. Intensification of cavitational activity and efficient design of industrial scale hydrodynamic cavitation reactors is required for ensuring successful application of cavitational reactors at industrial scale operation.     

西安夏季大气亚微米颗粒物化学组成与来源的在线观测研究

西安作为汾渭平原地区最大的城市,大气颗粒物污染形势严峻.2017年夏季期间,在西安市浐灞生态园区运用气溶胶化学组分监测仪,对大气亚微米颗粒物中的非难挥发性组分(NR-PM1)进行了在线监测.观测期间NR-PM1的平均质量浓度为(30.1?±?15.4)μg???m?3.其中有机物含量最高,占NR-PM1总质量浓度的63％,其次为硫酸盐(18％)、铵盐(10％)和硝酸盐(9％).运用正交矩阵因子分析法共解析出两个主要因子,包括烃类有机组分(HOA)和含氧有机组分(OOA),分别占有机物总质量浓度的43％和55％.HOA主要由机动车排放贡献,而OOA主要由气态污染物的二次反应生成.气象因素对NR-PM1的浓度与化学组分的影响较为显著.高硝酸盐阶段发生在高湿、低温条件,可能是由氮氧化物的液相反应产生的.高硫酸盐阶段发生在低湿、高温条件,主要来自于大气光化学反应的贡献.该研究结果为西安及周边地区的空气污染治理决策提供重要的理论依据.     

Improved treatment approach for the removal of aromatic compounds using polymeric beads in Fenton pretreatment and biological oxidation

An improved approach based on the use of iron-doped polymeric beads (IPB) as Fenton catalyst in the pretreatment and biomass-doped polymeric bead (BPB) in the biological oxidation has been reported for the removal of different aromatic mixtures present as pollutants in the aqueous solutions. Degradation has been investigated at fixed loading of IPB as 2.5 % weight basis and varying loading of hydrogen peroxide so as to understand the effect of oxidant loading on the extent of degradation. It has been observed that the maximum removal efficiency as 75.5, 81.4, and 59.1 % was obtained for the benzene-toluene-naphthalene-xylene (BTNX), benzene-toluene-ethylbenzene-xylene (BTEX), and benzene-toluene-naphthalene-p-nitrophenol (BTNp-NP) mixtures, respectively, at a 40-min pretreatment and optimum pH of 3.5. The biodegradability index was also observed in the favorable range of 0.4 to 0.5 after the pretreatment at optimum H₂O₂ loading of 1.5 g L⁻¹. Maximum COD removal efficiency of 99.2, 99.3, and 99.6 % was obtained using the biological oxidation treatment for 40 h for the case of BTNX, BTEX, and BTNp-NP mixtures, respectively. Analysis of kinetic models revealed that degradation followed three distinct stages based on fitting of the three-stage model and BPB was found to be more efficient as compared to the primary activated sludge (PAS) and modified activated sludge (MAS). Reusability studies confirmed that both IPB and BPB were effective over many cycles giving stable performance during degradation without leaching of Fe³⁺ ions into the solution.

     

Ultrasound and ozone assisted biological degradation of thermally pretreated and anaerobically pretreated distillery wastewater

The present work is aimed at increasing the overall efficiency of the treatment process of distillery spent wash using a combination of different treatment techniques. Initially the effluent samples were subjected to Thermal Pretreatment (TPT-DW) and anaerobic treatment (ANA-DW). Advanced oxidation techniques, viz., Ultrasound (US) and Ozone were then used for further COD reduction followed by the conventional aerobic oxidation using mixed microbial consortium. Pretreatment of TPT-DW with US and Ozone (as stand alone techniques) enhanced the subsequent aerobic oxidation rate. For US treated sample, a maximum of 13% COD reduction was attained at the end of 48 h of aerobic oxidation, while for the ozone treated effluent a maximum of 45.6% COD reduction was obtained as compared to mere 1.8% COD reduction for the control (TPT-DW directly subjected to aerobic oxidation) indicating a 25 times increase in the rate of aerobic biodegradation of ozonated sample. Anaerobically treated effluent sample (ANA-DW) could be successfully treated aerobically. In this case, however, the use of advanced oxidation techniques did not result in any synergistic effects. The rate of the aerobic oxidation was slightly higher for the control (ANA-DW directly subjected to aerobic oxidation) as compared to the sample pretreated using ultrasound or ozonation. TOC analysis revealed that between the two pretreatments studied, ozone was found to be superior over US as it led to both COD as well as TOC reduction during the aerobic oxidation step for ANA-DW effluent stream.     

Intensification of degradation of aqueous solutions of rhodamine B using sonochemical reactors at operating capacity of 7 L

In the present work, degradation of rhodamine B, a typical dye effluent commonly observed in chemical processing wastewaters has been investigated using a sonochemical reactor with capacity of 7 L. The reactor consists of an ultrasonic bath equipped with a single large transducer having longitudinal vibrations with operating frequency of 25 kHz and rated power output of 1 kW. The effect of operational conditions such as the rhodamine B initial concentration, operating pH and use of additives such as H(2)O(2), CCl(4) and TiO(2) has been investigated initially. A mathematical model has also been fitted to estimate the rate constant for rhodamine B removal under different operating conditions. Intensification studies have been carried by combining sonochemical oxidation with photocatalytic oxidation under optimized conditions. In all the investigated systems, complete removal of rhodamine B (10 ppm initial concentration) was obtained using a combination of sonochemical reactor and CCl(4). Sonocatalysis (in the presence of TiO(2)) of rhodamine B showed 92% degradation, while sonophotocatalysis gave degradation of 93%. TOC analysis at various optimum conditions was also performed to quantify the extent of mineralization and it was observed that the extent of mineralization is always lower than the extent of removal of parent compound.