Fate of Bacillus sp. and Pseudomonas sp. isolated from seawater during chlorination and microfiltration as pretreatments of a desalination plant

In order to assess the biofouling propensity of Bacillus sp. and Pseudomonas sp. isolated from the seawater intake of a desalination system, the effect of chlorination and microfiltration pretreatment processes on these organisms was investigated. The removal efficiency of Bacillus sp. Sea-3 was higher than that of Pseudomonas sp. Sea-5 in the hollow-fiber microfiltration. However, Bacillus sp. Sea-3 had a stronger resistance against chlorination and also showed increase in active cell numbers at 24 h after chlorination, whereas the viability of Pseudomonas sp. Sea-5 decreased rapidly during the same time. The spo0A gene (which makes the regulatory protein Spo0A to enter the development process of sporulation) expression assay of Bacillus sp. Sea-3 in different chlorination conditions showed that sporulation gene transcription level varied in 0 and 24 h after chlorination. Increase in the number of spo0A gene at 0 h after chlorination was positively related with the increased numbers of cells during 24 h incubation since lysed cells were utilized by Bacillus sp. during its reproduction and adaptation of 24 h made vegetative growth of spores active. Sporulation gene assay of Bacillus sp. in the chlorination of seawater showed one of the selective options for pretreatment design in order to reduce the risk of biofouling.