Characterization of bacterial coliform occurrences in different zones of a drinking water distribution system

Culture and molecular methods as complementary tools for water quality management

Bacterial communities in a full-scale drinking water treatment plant (DWTP) were characterized using matrix-assisted laser desorption/ionization time of flight mass-spectrometry (MALDI-TOF MS) to identify HPC isolates and the obtained results were compared to 16S rRNA (V4) metabarcoding data acquired in a previous study. Sixty-three samples were collected at nine stages of the potabilization process: river water and groundwater intake, decantation, sand filtration, ozonization, carbon filtration, reverse osmosis, the mixing chamber and post-chlorination drinking water. In total, 1807 bacterial colonies were isolated, 32 % of which were successfully identified to at least the genus level by MALDI-TOF MS using our previously developed Drinking Water Library. Trends in diversity were similar by both approaches, but differences were observed in the detection of taxa, especially at lower hierarchy levels. High bacterial diversity was observed in river and groundwater, where Proteobacteria predominated. The diversity decreased significantly after the chlorination step, where Bacillus sp. (Firmicutes) and an unknown genus of Obscuribacteraceae (Cyanobacteria) were the most prevalent genera according to MALDI-TOF MS and metabarcoding, respectively. The two approaches gave similar results for the decantation, sand filtration and mixing chamber steps, where the most abundant taxon was Flavobacterium. The combined use of these culture-based and culture-independent methods to characterize microbial populations may help to better understand the role of bacteria in water treatment and quality, which will be of value for DWTP management.

Effect of oxygen injection in a reclaimed wastewater pipeline on the microbiological quality of water

In this work the influence of oxygen injection on the inactivation of microbiological indicators during reclaimed wastewater transportation was studied. Experiments were carried out in a completely filled gravity pipe (62 km long), at two different periods of the year and with three different oxygen doses (7, 15 and 30 mg L(-1)). Microbiological parameters studied were faecal coliforms, Escherichia coli, enterococci and somatic coliphages. As a consequence of the oxygen injection, a significant inactivation of the microbiological parameters was observed during the aerobic stretch of the pipe. Later, once the oxygen had been consumed, inactivation stopped and even a slight regrowth of the microbial population took place. Inactivations were within the range of 0.6-1.0 log10 units, in most cases. No significant differences between inactivations for the different microbiological parameters were found, except for the somatic coliphages. A relationship between the inactivation degree and oxygen dose and organic matter content was observed. The biofilm played an important role in the inactivation process. The injection of oxygen contributes to improving the microbiological quality of reclaimed wastewater during its transport by pipelines, helping to diminish the subsequent on-site disinfection requirements.

[Coliforms in the water supply of fast-food chains in the Metropolitan Region of Recife, in the state of Pernambuco (Brazil)]

A guaranteed supply of clean drinking water in food outlets is a relevant subject for public health. The scope of this study was to assess the microbiological quality of 96 water samples of a network of fast-food stores in the city of Recife (state of Pernambuco, Brazil) and Metropolitan Area and to compare the results to the standards established by Brazilian Health Ministry decree nº 518/2004. Every month, a double sample from one of the faucets in the food preparation area of the eight stores investigated was analyzed, totaling 96 samples over one year. The analyses followed the established methodology of American Public Health Association (APHA), in order to conduct the Presence-Absence Test, considering the potability standard in pertinent legislation. Results revealed that 11.46% and 1.04% of samples contained water contaminated with total coliforms and thermotolerant coliforms, respectively. The quality of the water in the food establishments studied is thus a health hazard since a significant percentage of samples analyzed were inappropriate for human consumption in accordance with current legislation, which stipulates the absence of total coliforms and thermotolerant coliforms.

QUALIDADE MICROBIOLÓGICA DA ÁGUA UTILIZADA EM FAZENDAS LEITEIRAS PARA LIMPEZA DAS TETAS DE VACAS E EQUIPAMENTOS LEITEIROS EM TRÊS MUNICÍPIOS DO ESTADO DO MARANHÃO

RESUMO Objetivou-se com este estudo avaliar a qualidade da água utilizada na higienização do úbere dos animais, de equipamentos e utensílios de ordenha em propriedades leiteiras nos municípios de Miranda do Norte, Itapecurú-Mirim e Santa Rita, MA, através do NMP de coliformes totais e Escherichia coli, pelo método Colilert. Foram coletadas 20 amostras de água no período de verão (agosto a dezembro/2006) e 20 amostras no período de inverno (janeiro a julho/2007). Verificouse no verão que coliformes totais variaram de ausência a contaminação máxima tabelada (> 2419,6 NMP) e E. coli variou de ausência a 344,1 NMP e no inverno, coliformes totais variaram de ausência a contaminação máxima (> 2419,6 NMP) e E. coli variou de ausência a 770,1 NMP. No verão, 90% das amostras para coliformes totais e 75% de amostras para E. coli e no inverno, 90% das amostras para coliformes totais e 70% para E. coli estavam em desacordo com a portaria n° 518/2004 do Ministério da Saúde. É necessária a realização de um trabalho de educação sanitária junto à população do meio rural, a adoção de medidas preventivas, visando minimizar a ocorrência de enfermidades de veiculação hídrica, e melhoria da qualidade do leite produzido nas propriedades leiteiras.