Ozonation at Wiggins Water Purification Works,Durban, South Africa

The post-ozone plant at Wiggins waterworks was commissioned during 1984. The main objective of the post–ozone plant was to ensure proper disinfection, including the elimination of viruses, whenever raw water for the works was pumped from the polluted lower Umgeni River. The main problems experienced with the post–ozone plant were poor ozone transfer efficiency in the contact tank and poisoning of the catalyst in the thermal-catalytic destructor.     

紫外线对原水中几种微藻的作用效果研究

采用准平行光束仪对梅尼小环藻、谷皮菱形藻、钝脆杆藻、小球衣藻、镰形纤维藻、斜生栅藻、铜绿微囊藻和卵形隐藻等8种微藻进行辐射,确定剂量反应关系,研究紫外线对它们的作用效果及特点。结果表明,紫外线对梅尼小环藻、谷皮菱形藻、镰形纤维藻、斜生栅藻、铜绿微囊藻和卵形隐藻均具有一定的灭活作用,灭活率随着紫外线剂量的增加而提高,在剂量为400mJ/cm2时它们的灭活率分别为15.5%、26.9%、50.4%、6.9%、64.3%和19.8%;低剂量的紫外线对钝脆杆藻和小球衣藻细胞生长有促进作用,在剂量大于300mJ/cm2时有灭活作用,在剂量为400mJ/cm2时的灭活率分别为15.7%和6.2%。藻细胞个体大小不是影响紫外线灭活效果的原因,藻的种类、藻细胞壁的有无及其成分的不同等可能是造成不同灭活效果的原因。     

Inactivation of Bacillus subtilis spores with ozone and monochloramine

The inactivation kinetics of Bacillus subtilis spores with ozone and monochloramine was characterized by a lag phase followed by a pseudo-first-order rate of inactivation. The lag phase decreased and the post-lag phase rate constant increased with increasing temperature within the range investigated (1-30 degrees C for ozone, 1-20 degrees C for monochloramine). The corresponding activation energies were 46820 J/mol for ozone and 79640 J/mol for monochloramine. The CT concept was found to be valid within the concentration range investigated of 0.44-4.8 mg/l for ozone, and 3.8-7.7 mg/l as Cl(2) for monochloramine. The inactivation kinetics of B. subtilis spores with both ozone and monochloramine varied with pH within the range of pH 6-10 investigated. The fastest ozone and monochloramine inactivation rates were observed at pH 10 and 6, respectively. Different stocks of the same strain of B. subtilis spores had different resistance to ozone and monochloramine mainly because of discrepancies in the extent of the lag phase. B. subtilis spores might not be conservative surrogates for C. parvum oocysts for ozone disinfection at relatively low temperature mainly due to the spores having a lower activation energy compared to that for the oocysts. In contrast, the activation energy for monochloramine was comparable for both microorganisms but differences in the extent of the lag phase might result in the spores being overly conservative surrogates for the oocysts at relatively low temperature.     

不同LET碳离子对V79细胞辐射敏感性的影响

以中国仓鼠肺V79细胞为材料,利用兰州近代物理研究所重离子研究装置（HIRFL）产生的碳离子,研究了不同线性能量传递（LET）的重离子对体外培养细胞的存活效应,并与γ射线的结果作了比较。结果表明,不同LET碳离子引起细胞失活效应由大到小的顺序依次为125、200、700keV/μm。碳离子表现为无肩区的存活曲线,属单靶单击模型,γ射线表现为有肩区的存活曲线,属多靶单击模型。LET值为125、200、700keV/μm时得到的失活截面分别为35、12、8μm^2。当细胞存活比率为0.1和0.37,在LET为125keV/μm时得到相对生物学效应（RBE）值为1.47和2.19。     

Use of zero-valent iron nanoparticles in inactivating microbes

Nanoscale zero-valent iron (NZVI) particles were investigated in inactivating gram-positive Bacillus subtilis var. niger and gram-negative Pseudomonas fluorescens bacteria, and the fungus Aspergillus versicolor. NZVI particles were synthesized using NaBH₄ and Fe(NO₃)₃·9H₂O, and the microbial suspensions were subjected to the treatments of NZVI particle suspensions with concentrations of 0.1, 1 and 10 mg/ml for 5 min. Field emission scanning electron microscope (FE-SEM) was used to characterize the synthesized NZVI particles, suspensions and the surface morphologies of the treated agents.FE-SEM images showed that the NZVI particles were spherical with a fairly uniform size of about 20–30 nm, and the iron precipitates FeO(OH) appeared in needle-shape aggregates. When treated directly with NZVI particles under aerobic condition, the surfaces of microbes were quickly coated with needle-shape yellow-brown iron oxides. In this study, complete inactivation was achieved both for B. subtilis var. niger and P. fluorescens when treated with 10 mg/ml NZVI particles with vigorous shaking under aerobic condition. When NZVI particle concentration decreased to 1, 0.1 mg/ml, there was still a complete inactivation for P. fluorescens, while for B. subtilis var. niger the inactivation decreased to 95%, 80%, respectively. However, no inactivation was observed for the fungus A. versicolor when treated the same manner. Physical coating, disruption of membrane and generation of reactive oxygen species have played major roles in the inactivation observed.     

Pilot-Scale and Full-Scale Evaluation of the Chlorine-Ammonia Process for Bromate Control During Ozonation

An innovative approach to minimize bromate formation using sequential chlorine and ammonia (Cl₂-NH₃ process) was developed at pilot scale and validated in a full-scale drinking water facility. Pilot-scale results showed the Cl₂-NH₃ process minimized bromate formation by 65–95% compared to 40–70% using ammonia only. A 90-day full-scale evaluation confirmed the Cl₂-NH₃ process could prevent bromate concentrations from exceeding 10 μg/L. Full-scale implementation of the Cl₂-NH₃ process allowed an increase in ozone exposure level from 3.0 mg-min/L to 8.6 mg-min/L at 15.1°C. The increased exposure level is important as drinking water utilities strive to meet more stringent drinking water regulations such as Cryptosporidium inactivation.     

超高压对食品中的酶的影响

综述了超高压技术在国内外的最新研究成果及动态,其中着重谈到了超高压技术对于酶的灭活及激活作用,并对过氧化氢酶,多酚氧合酶,果胶甲基酯酯,脂肪氧合酶,纤维素酶,木瓜蛋白酶等的超高压作用结果作了评述。     

Inactivation of polyphenol oxidase from Pacific white shrimp by dense phase carbon dioxide

The inactivation of polyphenol oxidase (PPO) from Pacific white shrimp exposed to dense phase carbon dioxide (DPCD) treatment was investigated. PPO activity showed a dramatic loss at 4–25 MPa and 37 °C. At the lower pressure (4–15 MPa), the experimental data of inactivation followed the first-order reaction kinetic model, the pressure sensitivity (Z_P) of the kinetic parameters was 49.02 MPa and the activation volume (△ V^≠) was − 120.88 cm³/mol. At the higher pressure (20 and 25 MPa), the experimental data of inactivation followed the biexponential kinetic model. The kinetic rate constant k_F and k_S of fast and stable fractions were 2.45 and 0.08 min^{− 1}, respectively. The decimal reduction time D_F and D_S were 0.94 and 29.43 min at 25 MPa and 37 °C, respectively. After DPCD treatment, the loss activity of PPO had no restoration storing for 6 days at 4 °C. The results of SDS-PAGE and activity staining also showed that DPCD treatment had the obvious inhibitory effect on PPO from Pacific white shrimp. The PPO activity in vivo was easier to be inactivated than that in crude PPO extracts under the same DPCD treatment conditions.

Industrial relevance

There is a growing interest in non-thermal pasteurization methods, which could retain food's freshlike physical, nutritional, and sensory qualities. Pacific white shrimp accounts for 90% of the global aquaculture shrimp production, they are becoming increasingly popular. However, enzymatic browning of shrimp has been of great concern to food scientists and food processors. Dense phase carbon dioxide (DPCD) may be an adequate tool to obtain high quality since PPO activity could not be inactivated totally by high pressure under 400 MPa yet. The present work deals with the inactivation of PPO from Pacific white shrimp exposed to DPCD treatment in order to explore the feasibility of shrimp by DPCD process.     

Enzyme inactivation kinetics: Coupled effects of temperature and moisture content

Enzymes are often dried for stability reasons and to facilitate handling. However, they are often susceptible to inactivation during drying. It is generally known that temperature and moisture content influence the enzyme inactivation kinetics. However, the coupled effect of both variables on enzyme inactivation over a broad temperature–moisture content range is still not well understood. Therefore, the inactivation of β-galactosidase in maltodextrin matrix is investigated using a newly developed method. An improved kinetic modelling approach is introduced, to predict the inactivation over a large range of temperature–moisture values. The model assumes a two-step inactivation mechanism involving reversible unfolding and irreversible inactivation. The model is able to describe the inactivation kinetics of β-galactosidase accurately, showing the temperature-dependent kinetic transition from reversible unfolding to irreversible inactivation limited. Application of this approach can provide immediate understanding of the effect of processing on enzyme inactivation and indicates the processes’ critical points, which offers the possibility for optimisation.     

新型纳米光催化薄膜的结构设计与应用研究

采用溶胶-凝胶法分别制备了TiO2/ZrO2、TiO2/ZrTiO4、TiO2/SiO2等异质结构纳米薄膜.本文对形成溶胶的各成分配比、粘度以及薄膜样品的热处理工艺等进行了探讨,同时用喷涂法在瓷砖上成功制备光催化薄膜,用SEM对薄膜的外貌特征进行了表征,并利用紫外-可见分光光度计研究了薄膜吸收光谱的变化,用分光光度法研究了异质结构薄膜对甲基橙溶液的降解,探讨了过渡层对薄膜的光催化效率和抗失活稳定性的影响.结果表明,TiO2/ZrO2、TiO2/ZrTiO4薄膜中的晶粒尺寸减小,薄膜的光催化活性和抗失活稳定性均有较大提高,并可以用工厂方法制备大面积薄膜.