ABSTRACT
The feasibility of substituting a conventional pre-treatment, consisting of dioxi-chlorination, coagulation/flocculation, settling and sand filtration, of a drinking water treatment plant (DWTP) by direct ultrafiltration (UF) has been assessed from a microbiological standpoint. Bacterial indicators, viral indicators and human viruses have been monitored in raw river, ultrafiltered and conventionally pre-treated water samples during two years. Direct UF has proven to remove bacterial indicators quite efficiently and to a greater extent than the conventional process does. Nevertheless, the removal of small viruses such as some small bacteriophages and human viruses (e.g. enteroviruses and noroviruses) is lower than the current conventional pre-treatment. Membrane integrity has been assessed during two years by means of tailored tests based on bacteriophages with different properties (MS-2, GA and PDR-1) and bacterial spores (Bacillus spores). Membrane integrity has not been compromised despite the challenging conditions faced by directly treating raw river water. Bacteriophage PDR-1 appears as a suitable microbe to test membrane integrity, as its size is slightly larger than the considered membrane pore size. However, its implementation at full scale plant is still challenging due to difficulties in obtaining enough phages for its seeding.
Subject(s)
Drinking Water/microbiology , Rivers/microbiology , Ultrafiltration/methods , Water Purification/methods , Bacillus/isolation & purification , Bacteriophages/isolation & purification , Drinking Water/virology , Environmental Monitoring , Rivers/virology , Spores, Bacterial/isolation & purificationABSTRACT
The possibility of using aerobic spores as indicators (surrogates) of water treatment efficiency for the removal of Giardia cysts and Cryptosporidium oocysts was evaluated in a water treatment plant that supplies the Barcelona area of Spain. The water treatment consists of pre-chlorination, flocculation-sedimentation, double filtration (sand and granular activated carbon, GAC) with intermediate ozonation and post-chlorination. Aerobic spores significantly increased after GAC filtration, which indicated an active propagation of aerobic spore-formers. However, anaerobic (Clostridium) spores could be a good surrogate for Cryptosporidium oocysts, especially if their detection in samples at low concentrations was improved.
Subject(s)
Bacteria, Aerobic/growth & development , Cryptosporidium/isolation & purification , Giardia/isolation & purification , Water Purification/standards , Animals , Chlorine , Filtration , Flocculation , Oocysts , Oxidants, Photochemical/chemistry , Ozone/chemistry , Silicon Dioxide , Spores, Bacterial , Waste Disposal, FluidABSTRACT
The health related risk of wastewater reclamation and reuse is usually defined by laws, rules or regulations by using only biological tools; i.e. bacteria, viruses, or other pathogens or indicators determination. Those determinations exert some influence in the costs of the mentioned practices, and it seems probable that in the near future more determinations will be required. Nevertheless, a total indication of wastewater biological quality is not given by such organisms; in fact, long-term toxicity is not detected by such means. The future of biological control of reclamation and reuse systems and the price associated to such determinations is examined through a practical application case.
Subject(s)
Conservation of Natural Resources/methods , Water Purification/methods , Water Supply/standards , Conservation of Natural Resources/economics , Cost-Benefit Analysis , Public Health , Water Microbiology/standards , Water Purification/economics , Water Supply/economics , Water Supply/statistics & numerical dataABSTRACT
AIMS: To compare the bacterial coliforms detected from occurrences in three zones of a water distribution system supplied by two separate water sources. METHODS AND RESULTS: Conventional and standardized protocols for identifying enterobacterial populations were applied. Additional tests to confirm isolates were included. Analyses of diversity and population similarity were performed using the Phene Plate System, a miniaturized biochemical phenotyping method. Isolates were identified by the API 20E system in tandem with biochemical phenotyping. A total of 16 576 samples were taken from the water distribution system, with 1416 isolates analysed. A low number of coliform occurrences were observed (2%). Escherichia coli was not detected in either water origin or in Zone 2 samples; however, in Zones 1 and 3 a low number of cases of E. coli were recorded. The percentages of E. coli depended on the identification criteria. Eight biochemical profiles for coliform populations were defined according to the results of the confirmative tests. There was a high diversity among these populations in the three zones studied, although no significant variations in their composition (associated with occurrences in the different zones) were observed. Klebsiella oxytoca was the most commonly detected species irrespective of zone, although seven other enterobacterial genera were also found. CONCLUSIONS: Analysis of the enzymatic activity of beta-glucuronidase or application of the criteria established in the norm ISO 9308-1, in tandem with thermotolerance was needed to evaluate the occurrence of E. coli in the distribution systems. Detected occurrences of bacterial coliforms could be associated with re-growth patterns for specific sampling points in the distribution system. Seasonal differences, independent of the studied zones, were observed. SIGNIFICANCE AND IMPACT OF THE STUDY: Biochemical phenotyping of bacterial coliforms was shown to be a useful method on the characterization of occurrences in water distribution systems.