Download Investigation of Marine Bacterial Resistance to Chlorine

Investigation of Marine Bacterial Resistance to Chlorine during Desalination Pretreatment
Lynze Cheung
Mentor: Sunny Jiang
Severe drought and increasing population has pushed the Western U.S. to seek new sources of drinking water
to supplement existing supplies. The advancement of reverse osmosis (RO) membrane technology has made
desalination of seawater a viable source of drinking water in the coastal region. During membrane
desalination, chlorination of seawater is a common pretreatment process to reduce bacteria loads in the intake
in order to prevent membrane biofouling by the formation of bacterial biofilm. However, little is known
about the efficiency of chlorine treatment and desalination plants have reported biofouling following
dechlorination, indicating the inadequacy of chlorination to inactive all marine bacteria. This study
investigated the marine bacterial resistance to chlorine in order to improve membrane desalination efficiency
by reducing biofouling. Seawater from coastal Pacific Ocean was collected and treated with 3, 5, and 10 mg/L
of chlorine for 10 min. The bacterial resistance to chlorine was examined by adding essential nutrients after
dechlorination to observe the possible growth of surviving bacteria. The results showed that a fraction of the
marine bacteria were resistant to all chlorine concentrations tested, which was further confirmed by a second
chlorine treatment. An extracellular polymeric substance (EPS) assay was performed on the bacterial
community and isolates to identify if the production of EPS is a possible mechanism for chlorine resistance.
However, EPS assay results were inconclusive indicating the complexity of the resistance mechanism.
Identification of resistant bacteria using 16S rDNA sequencing is current underway and will provide further
insight.