Disinfection of wastewaters: high-energy electron vs gamma irradiation

A study was undertaken to examine the sensitivity of a wastewater population of coliphage, total coliforms and total flora present in raw sewage and secondary effluent after irradiating with similar doses delivered by a high-energy electron beam and y -radiation. The electron beam study was conducted on a large scale at the Virginia Key Wastewater Treatment Plant, Miami, Fla. The facility is equipped with a 1.5 MeV, 50 mA electron accelerator, with a wastewater flow rate of 8 ls⁻¹. Concurrent y-radiation studies were conducted at laboratory scale using a 5000 Ci, ⁶⁰Co y -source. Three logs reduction of all three test organisms were observed at an electron beam dose of 500 krads, while at least four logs reduction were observed at the same dose utilizing the y-source.     

Effects of urbanisation on the quality of the urban runoff for Delhi watershed

The current paper is the first study to report quality of urban runoff, focusing on the diffuse sources contributing to pollutant loads in the Delhi watershed. The quality of stormwater runoff from the urban watershed of Delhi was evaluated to assess the effects of different land-use practices on pollutant concentrations. Six sites within the Delhi watershed with different land-use characteristics were selected. The microbial quality of the urban runoff from sub-catchments of Delhi watershed is very poor with Faecal Coliform (FC) levels varying between 6 and 7 log orders. There was a good correlation between the chemical and biological quality of urban runoff with land-use characteristics such as impervious land and population density. Except for chemical oxygen demand all other parameters in urban runoff were found to exceed the effluent discharge standards set by the National River Conservation Directorate (NRCD), India. The public health risks associated with exposure to urban runoff via different routes have also been qualitatively estimated.     

拉萨地区牦牛屠宰过程中的微生物污染

为探明拉萨地区牦牛胴体屠宰过程中的微生物污染程度,明确微生物关键控制点,对拉萨地区某具有代表 性的规范屠宰企业屠宰前车间空气中的微生物、各屠宰工艺环节牦牛胴体表面以及人员用具的菌落总数和大肠菌群 数量进行测定。结果表明：屠宰前车间微生物污染严重;随着剥皮和去内脏工艺的进行,牦牛胴体的菌落总数和大 肠菌群数量显著增加;斧劈四分体后胴体的菌落总数和大肠菌群数量均显著高于剥皮和去内脏后;牦牛屠宰过程中 微生物的主要来源是垫板和斧头。     

乳糖法与LST法检测大肠菌群的差异性研究

目的:为了解乳糖法与LST法检测大肠菌群的差异,帮助产品标准的更改。方法:乳糖法与LST法分别对大肠杆菌标准菌液和8类食品进行检测。结果:对大肠杆菌标准菌液的检测,乳糖法和LST法在MPN95%可信限内都是准确的、可靠的。LST法比乳糖法的平均检出率高出143%。对8类食品的检测,2种方法总体上存在显著性差异,LST法比乳糖法的平均不合格率高82.41%。就个体来讲,当食品中含有较多大肠菌群时,两者的结果有显著差异;当样品中含有极少或者不含有大肠菌群时,两者的结果没有显著差异。结论:LST法比乳糖法的检出率高,修订产品标准时,对易被大肠菌群污染的产品应依据LST法的结果重新修订标准值。     

肉品中菌落总数和大肠菌群快速检测试纸片的研究

对肉品中菌落总数和大肠菌群快速检测试纸片进行了研究.选择中速定性滤纸为材料,分别浸入经不同特殊处理(不同浓度的TTC、琼脂、NaCl)的培养基中,40℃下烘干制得试纸片;将所制得的菌悬液涂布于成份不同的试纸片上,于32℃,培养20h(试纸片法),或涂布于平板计数琼脂上,于32℃,培养48h(国标法),然后计数,将二者得到的数据进行比较.结果表明:试纸片法与国标法具有很高的相似性.在100ml培养基中,TTC的浓度为0.02‰时试纸片的显色情况最好,生成的红色菌落数目最多.菌落生长受琼脂浓度的影响,当琼脂的浓度高于或低于0.15%时,细菌生长速度逐渐减慢.NaCl的浓度在0.4%时菌落生长呈现最好势态.     

现场电解制次氯酸钠在污水处理厂出水消毒的应用研究

随着污水厂出水排放标准日益提高,对排水中粪大肠菌群的控制也越来越严格。现场电解制次氯酸钠发生系统是一种较为理想的环境友好型氯消毒技术,能够有效杀灭城镇污水处理厂出水中的粪大肠杆菌。因原水水质不同,次氯酸钠的杀菌效果会有差异。次氯酸钠对原水中的氨氮有一定的去除作用,但是有可能氧化原水中残留的有机氮,从而使得氨氮含量重新升高。现场连续投加试验中,反应池次氯酸钠浓度为1．2mg／L,出水中的粪大肠菌群始终稳定达到GB18918-2002一级A标准的要求,且其他水质指标（如氨氮、COD等）良好。     

平板显色法同时计数生乳中的大肠菌群和菌落总数

为提高大肠菌群和菌落总数的计数效率，选用2-硝基苯基-β-D-吡喃半乳糖苷作为平板培养基中的显色底物，利用大肠菌群lacZ基因编码的β-半乳糖苷酶将其分解产生黄色化合物，使得大肠菌群菌落区分于其他菌株，实现大肠菌群和菌落总数的同时计数，优化该培养基配方，评估培养基的特异性、准确性以及在生乳中的应用效果。最终确定该培养基配方：胰蛋白胨12.5 g/L、酵母浸粉2.5 g/L、磷酸氢二钾2.75 g/L、磷酸二氢钾1.75 g/L、氯化钠5.0 g/L、琼脂15.0 g/L，2-硝基苯基-β-D-吡喃半乳糖苷0.1 g/L，pH值为7.0。在此基础上，添加0.05 g/L异丙基-β-D-硫代半乳糖苷或2.0 g/L乳糖均能够增强菌落显色效果，而葡萄糖则会抑制黄色化合物生成。特异性实验中，仅大肠菌群菌落颜色呈黄橙色，其他菌株则呈乳白色。在生乳样本中，该培养基与国标方法对于大肠菌群和菌落总数的计数结果基本一致。因此，该复合显色培养基能够大大提高大肠菌群和菌落总数的计数效率，降低检测成本，为生乳的卫生指标检测提供一种可行方案。     

Influence of filter media depth and vegetation on Faecal Coliform removal by stormwater biofilters

Biofilters are promising technologies that widely applied in the treatment of urban stormwater. However, the microbial removal capacity performance depends greatly on the design of biofilters. Hence, this laboratory study attempts to investigate the influence of filter media depths (i.e. 150, 250, 350 and 450 mm) and the variation of native plants, that is, Cow Grass (Axonopus compressus) and Pearl Grass (Axonopus compressus, dwarf) in removing stormwater microorganism particularly Faecal Coliform (FC). Findings showed that a minimum media depth of 300 mm was required to achieve >1 log FC removal. The mean removal of FC at 450 mm depth filter exceeded 2 log for both Cow and Pearl grass biofilter columns. Results showed that there was no statistically significant difference in vegetation type on the performance of FC removal, however, Cow grass biofilter column revealed higher FC mean log removal compared to Pearl grass biofilter column.     

Reactivation and growth of non-culturable indicator bacteria in anaerobically digested biosolids after centrifuge dewatering

Recent literature has reported that high concentrations of indicator bacteria such as fecal coliforms (FCs) were measured in anaerobically digested sludges immediately after dewatering even though low concentrations were measured prior to dewatering. This research hypothesized that the indicator bacteria can enter a non-culturable state during digestion, and are reactivated during centrifuge dewatering. Reactivation is defined as restoration of culturability. To examine this hypothesis, a quantitative polymerase chain reaction (qPCR) method was developed to enumerate Escherichia coli, a member of the FC group, during different phases of digestion and dewatering. For thermophilic digestion, the density of E. coli measured by qPCR could be five orders of magnitude greater than the density measured by standard culturing methods (SCMs), which is indicative of non-culturable bacteria. For mesophilic digestion, qPCR enumerated up to about one order of magnitude more E. coli than the SCMs. After centrifuge dewatering, the non-culturable organisms could be reactivated such that they are enumerated by SCMs, and the conditions in the cake allowed rapid growth of FCs and E. coli during cake storage.     

广州秋季市售生蚝微生物污染状况调查

目的是了解广州秋季市售生蚝微生物污染状况。按照GB／T4789—2003《食品卫生微生物学检验》对样品进行微生物检测,结果发现秋季市售生蚝的微生物污染状况比较严重,菌落总数和大肠菌群指标均出现严重超标,超标率分别达到68％和78％,即使在温度偏低的11月份超标现象仍较严重。所检样品中,弧菌超标更为严重,3个月弧菌的检出率则高达90％。结论是广州市售生蚝的微生物污染状况严重,建议消费者不要生食或使用未煮熟的生蚝。