On-site Biocide Study and Identification of Troubleshome Microorganisms in a Middle East Inland Water Treatment Plant

Abstract

An On-Site Biocide Study and Identification of Troublesome Microorganisms in a Middle East Inland Water Treatment Plant

In order to fully determine the efficacy of biocides for application in the field it is important to carry out on-site trials using ‘real’ system microbes and water. Such an approach can help solve problems caused by troublesome micro-organisms and optimise biocide dosing regimes. In this study, sessile bacterial monitoring tubes were set up at various locations on a produced water and aquifer water treatment system, and were monitored by MPN culturing until biofilm had developed. An audit revealed the system to be heavily contaminated and a thick biofilm developed rapidly within the tubes.

The biofilm coated tubes were then used to monitor the efficacy biocides of varying compositions. THPS based biocides were most effective at killing sessile SRB; although no biocide was apparently successful at killing sessile GAnB as determined by MPN culturing. It was hypothesised this was due to biocide killing vegetative cells, leaving intact spores which subsequently grew in the culture media. This was confirmed through DGGE and DNA sequencing analysis which showed that the majority of the GAnB were indeed spore-forming Clostridia. Remediation and control strategies could then be applied to alleviate the microbiological contamination problem and optimise biocide dosing regimes. This case study illustrates how a combination of traditional microbiology and DNA based techniques can be applied synergistically to overcome field based microbiological problems.