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Worldwide, the most important reuse of wastewater, in volume, is agricultural irrigation. Therefore, there is a need to properly treat wastewater for such purpose, considering the removal of pathogens while leaving suitable amounts of nutrients and other compounds to increase productivity. Helminth ova are one of the main targeted pathogens in the new guidelines for water reuse in agriculture and aquaculture issued in 2006 by the World Health Organization. However, relatively little research has been done recently on how to remove and inactivate helminth ova from wastewater and sludge and recommendations given several decades ago are still used, but when put into practice, particularly in developing countries, produce unsatisfactory results. One problem is that these criteria were developed using inaccurate analytical techniques and the other is the large number and variety of helminth ova species found in wastewater and sludge from the developing world. In fact, the few technological options to remove and inactivate helminth ova come from research performed using wastewater and sludge with low helminth ova content, and refer almost only to Ascaris (one type of helminth). This paper summarises recent research work and results from practical experience concerning helminth ova control for advanced and conventional sanitation.

During an outbreak of gastroenteritis in 28 children living in a small neighbourhood of Cuernavaca city (Mexico), a survey was performed to evaluate the confidence in coliform bacteria as sole indicators of potability of drinking waters. A primary infection by E. coli and a secondary by Pseudomonas aeruginosa was diagnosed in five of the children and the drinking water provided by a well was suspected as a transmission source. General and household distribution systems, household filters and bottled waters were evaluated for total and faecal coliforms, family Enterobacteriaceae, Paeruginosa and residual chlorine. In every sample, pathogenic/opportunistic bacteria were isolated even in the absence of coliforms and in the presence of residual chlorine. Arbitrarily assigned “pollution/risk levels” indicated that the most elevated risk was most frequently associated with storage in tanks and with bacterial colonisation in the pipeline system and commercial household filters where high levels of Paeruginosa were determined. A probability of correspondence between the presence of this bacterium and the secondary gastrointestinal infection diagnosed was found pointing towards a need for the inclusion of other microorganisms, one of which may be Paeruginosa, as indicators of health risk associated with drinking waters in Mexico.

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A survey of protozoa polluting bottled mineral water in Mexico was carried out using samples obtained form the three best-selling brands of bottled mineral water in the country. The organisms were concentrated through filtration procedures and subsequently cultured in the sterile media. The cultures were observed over four weeks, with identification to the level of genus and species. Most commonly found were the amoebae Naegleria gruberi, Acanthamoeba astronyxis, and Vahlkampfia vahlkampfi (trophic as well as cystic stages) plus one flagellate, Bodomorpha minima. No ciliates were detected. The public health importance of the findings is obvious, since some strains of Naegleria and Acanthamoeba have the potential to cause human disease that may lead to death.

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SUMMARYAn unusual Escherichia coli K I~ mutant for carbamyl phosphate synthetase is described. The mutation was generated by bacteriophage MUI insertion and left a 5 residual activity of the enzyme using either ammonia or glutamine as donors. The mutation is recessive to the wild-type allele and maps at or near the pyrA gene, but the mutant requires only arginine and not uracil for growth. By a second block in the pyrB gene it was possible to shift the accumulated carbamyl phosphate to arginine biosynthesis. The K, values and the levels of ornithine activation and inhibition by UMP were normal in the mutant enzyme,

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