Bacterial Population Dynamics in a Reverse-Osmosis Water Purification System Determined by Fluorescent Staining and PCR-Denaturing Gradient Gel Electrophoresis

Abstract

The bacterial population dynamics in an industrial scale reverse-osmosis (RO) water purification system were analyzed by fluorescent staining methods and denaturing gradient gel electrophoresis (DGGE). Bacterial numbers increased with storage in a tank, and bacterial diversity changed during the water purification process. A DNA sequence-based analysis of the major bands on the DGGE gel revealed that Simonsiella sp. (Betaproteobacteria) was abundant in the source water (activated sludge-treated waste effluent), while Bosea sp. and Rhizobium sp. (Alphaproteobacteria), which usually exist in an oligotrophic environment, became abundant during the water purification process. These results suggest the importance of microbiological monitoring by culture-independent methods for quality control in RO water purification systems. These methods could provide an early warning of impending problems and clarify critical steps in controlling specific bacteria contributing to the contamination of RO water systems.Key words: reverse-osmosis water purification system, bacterial diversity, oligotrophic environment, population dynamics, rapid microbiological method A huge volume of freshwater is treated and used every day for food and drink production, as well as medical and industrial needs. Water treatment based on reverse-osmosis (RO) membrane elements removes most particles and ions in source water and is widely used for water purification and seawater desalination. The processed water, reverse-osmosis water (RO water), is a critical component of food, drink and pharmaceutical products. Quality control of RO water, particularly microbiological quality control, is especially important when RO water will be used to create an ingestible product (7-9). Microorganisms which survive the water purification process and proliferate can become a source of microbial contamination, while water must meet strict quality standards which should be maintained until use.The production of RO water is a multistep process. Several treatments (e.g. filtration, UV irradiation) are employed to remove organic materials, ions and microorganisms. Despite these precautions, filters, tanks and other surfaces within the water supply system often provide a favorable environment for bacterial adhesion and growth. In the RO water manufacturing process, biofouling, damage to the RO membranes caused by microorganisms, is one of the most troubling problems. Many researchers are studying possible solutions to biofouling (21). Some research has outlined the dynamics of bacteria in lesser water purification systems, such as small water purifiers (13), pilot systems for potable water treatment (18), and drinking water treatment systems (3, 4, 15). However, bacterial population dynamics in largescale water treatment systems are still unknown. The bacterial population dynamics in working industrial scale RO water systems, especially systems using treated waste effluent as the source water, must be studied to advance quality assurance of RO water because these treated ...

16S Ribosomal RNA Gene-Based Phylogenetic Analysis of Abundant Bacteria in River, Canal and Potable Water in Bangkok, Thailand

“…Thus, this simple method is suitable for analyzing many samples simultaneously. TaqGold is often used for PCR amplification of eubacterial 16S rRNA genes from freshwater samples 10,11,14,15) ; however, this DNA polymerase was not very effective in our study.…”

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“…uidaho.edu/) and the result was "uncultured bacterium." More than 90% of bacteria in aquatic environments are difficult to culture under conventional conditions [1][2][3] and this result was convincing.…”

“…Microorganisms that survive the water purification process can become a source of microbial contamination. 1) Bacterial number and their community structure in freshwater should be determined as quickly as possible, and "real-time" and "onsite" microbiological methods are therefore required.…”

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