Quantification and identification of particle-associated bacteria in unchlorinated drinking water from three treatment plants by cultivation-independent methods.

Water quality regulations commonly place quantitative limits on the number of organisms (e.g., heterotrophic plate count and coliforms) without considering the presence of multiple cells per particle, which is only counted as one regardless how many cells attached. Therefore, it is important to quantify particle-associated bacteria (PAB), especially cells per particle. In addition, PAB may house (opportunistic) pathogens and have higher resistance to disinfection than planktonic bacteria. It is essential to know bacterial distribution on particles. However, limited information is available on quantification and identification of PAB in drinking water. In the present study, PAB were sampled from the unchlorinated drinking water at three treatment plants in the Netherlands, each with different particle compositions. Adenosine triphosphate (ATP) and total cell counts (TCC) with flow cytometry were used to quantify the PAB, and high-throughput pyrosequencing was used to identify them. The number and activity of PAB ranged from 1.0 to 3.5 × 10(3) cells ml(-1) and 0.04-0.154 ng l(-1) ATP. There were between 25 and 50 cells found to be attached on a single particle. ATP per cell in PAB was higher than in planktonic bacteria. Among the identified sequences, Proteobacteria were found to be the most dominant phylum at all locations, followed by OP3 candidate division and Nitrospirae. Sequences related to anoxic bacteria from the OP3 candidate division and other anaerobic bacteria were detected. Genera of bacteria were found appear to be consistent with the major element composition of the associated particles. The presence of multiple cells per particle challenges the use of quantitative methods such as HPC and Coliforms that are used in the current drinking water quality regulations. The detection of anoxic and anaerobic bacteria suggests the ecological importance of PAB in drinking water distribution systems.

Polaromonas and Hydrogenophaga species are the predominant bacteria cultured from granular activated carbon filters in water treatment.

AIM: Identification of the predominating cultivable bacteria in granular activated carbon (GAC) filters used in a variety of water treatment plants for selecting representative strains to study the role of bacteria in the removal of dissolved organic matter. METHODS AND RESULTS: Bacterial isolates were collected from 21 GAC filters in nine water treatment plants treating either ground water or surface water with or without oxidative pretreatment. Enrichment of samples in dilute liquid medium improved culturability of the bacteria by approximately log unit, to 9% up to 70% of the total cell counts. Genomic fingerprinting and 16S rDNA sequence analysis revealed that most (68%) of the isolates belonged to the Betaproteobacteria and 25% were identified as Alphaproteobacteria. The number of different genera within the Betaproteobacteria was higher in the GAC filters treating ozonated water than in the filters treating nonozonated water. Polaromonas was observed in nearly all of the GAC filters (86%), and the genera Hydrogenophaga, Sphingomonas and Afipia were observed in 43%, 33% and 29% of the filter beds, respectively. AFLP analysis revealed that the predominating genus Polaromonas included a total of 23 different genotypes. CONCLUSIONS: This study is the first to demonstrate that Polaromonas, which has mainly been observed in ultraoligotrophic freshwater environments, is a common component of the microbial community in GAC filters used in water treatment. SIGNIFICANCE AND IMPACT OF THE STUDY: The predominance of ultraoligotrophic bacteria in the GAC filters indicates that very low concentrations of substrates are available for microbial growth. Polaromonas species are suited for further studies on the nutritional versatility and growth kinetics enabling the modelling of biodegradation processes in GAC filters.

Fate of effluent organic matter (EfOM) and natural organic matter (NOM) through riverbank filtration.

Understanding the fate of effluent organic matter (EfOM) and natural organic matter (NOM) through riverbank filtration is essential to assess the impact of wastewater effluent on the post treatment requirements of riverbank filtrates. Furthermore, their fate during drinking water treatment can significantly determine the process design. The objective of this study was to characterise bulk organic matter which consists of EfOM and NOM during riverbank filtration using a suite of innovative analytical tools. Wastewater effluent-derived surface water and surface water were used as source waters in experiments with soil columns. Results showed the preferential removal of non-humic substances (i.e. biopolymers) from wastewater effluent-derived surface water. The bulk organic matter characteristics of wastewater effluent-derived surface water and surface water were similar after 5 m soil passage in laboratory column experiment. Humic-like organic matter in surface water and wastewater effluent-derived surface water persisted through the soil passage. More than 50% of total dissolved organic carbon (DOC) removal with significant reduction of dissolved oxygen (DO) was observed in the top 50 cm of the soil columns for both surface water and wastewater effluent-derived surface water. This was due to biodegradation by soil biomass which was determined by adenosine triphosphate (ATP) concentrations and heterotrophic plate counts. High concentrations of ATP in the first few centimeters of infiltration surface reflect the highest microbial activity which correlates with the extent of DOC reduction. Good correlation of DOC removal with DO and biomass development was observed in the soil columns.