Efficacy of pH elevation as a bactericidal strategy for treating ballast water of freight carriers

Abstract

Treatment of ship ballast water with sodium hydroxide (NaOH) is one method currently being developed to minimize the risk to introduce aquatic invasive species. The bactericidal capability of sodium hydroxide was determined for 148 bacterial strains from ballast water collected in 2009 and 2010 from the M/V Indiana Harbor, a bulk-freight carrier plying the Laurentian Great Lakes, USA. Primary culture of bacteria was done using brain heart infusion agar and a developmental medium. Strains were characterized based on PCR amplification and sequencing of a portion of the 16S rRNA gene. Sequence similarities (99+ %) were determined by comparison with the National Center for Biotechnology Information (NCBI) GenBank catalog. Flavobacterium spp. were the most prevalent bacteria characterized in 2009, comprising 51.1% (24/47) of the total, and Pseudomonas spp. (62/101; 61.4%) and Brevundimonas spp. (22/101; 21.8%) were the predominate bacteria recovered in 2010; together, comprising 83.2% (84/101) of the total. Testing was done in tryptic soy broth (TSB) medium adjusted with 5 N NaOH. Growth of each strain was evaluated at pH 10.0, pH 11.0 and pH 12.0, and 4 h up to 72 h. The median cell count at 0 h for 148 cultures was 5.20 × 106 cfu/mL with a range 1.02 × 105–1.60 × 108 cfu/mL. The TSB adjusted to pH 10.0 and incubation for less than 24 h was bactericidal to 52 (35.1%) strains. Growth in pH 11.0 TSB for less than 4 h was bactericidal to 131 (88.5%) strains and pH 11.0 within 12 h was bactericidal to 141 (95.3%). One strain, Bacillus horikoshii, survived the harshest treatment, pH 12.0 for 72 h.

Toxicity of Aqueous Alkaline Solutions to New Zealand Mudsnails, Asian Clams, and Quagga Mussels

“…Because of the simplicity of elevating water-system pH with NaOH, its potential use in confined pipes and in channels and tanks infested with nuisance mollusks may hold promise. Tests of ballast disinfection using additions of NaOH (Elskus et al 2015;Moffitt 2015a;Starliper et al 2015) suggested that not only was this chemical effective, but that after neutralization with CO 2 , the effluents would meet regulatory guidelines for safe discharge. Sodium hydroxide was registered as a herbicide many decades ago for control of tree roots in sewer systems, as a fungicide and algicide for use on water-well casings, and as a disinfectant in various indoor settings (USEPA 1992).…”

“…Elevating the pH of water with NaOH in freshwater ballast systems has been reported as highly effective to kill a suite of plankton and bacterial or viral species (Moffitt et al 2015a;Starliper et al 2015). The alkaline solutions in ballast tanks used can be neutralized with CO 2 , yielding environmentally harmless compounds that have been shown to meet effluent guidelines (Elskus et al 2015;Moffitt et al 2015a).…”

Effect of various poultry feather hydrolysates on the growth of indigenous keratinolytic strains

“…This NaOH content can inhibit the growth and production of bacterial enzymes. For example, NaOH or sodium hydroxide in pH 12 for 24 hours could kill bacteria [24]. NaOH in low concentrations can be bactericidal.…”

Potential of Maritime Transport for Ocean Liming and Atmospheric CO2 Removal

“…The use of ballast tanks to transport a slurry of SL could avoid the necessity of a dedicated cargo hold, and at the same time has the benefit of avoiding the treatment of ballast water (or at least reducing treatment costs), currently mandatory because ships are a major vector for the introduction of nonindigenous and harmful organisms (Johnson and McMahon, 1998;Sousa et al, 2008). pH increase through the addition of alkaline materials (one of which is calcium hydroxide) is an efficient and cheap ballast water treatment strategy (Starliper et al, 2015), since it kills the aquatic nuisance species that cause economic and ecological damages to oceans. International legislative constraints should be evaluated to understand the possibility of discharging SL slurry; ballast water treatment with SL is still not among the authorized treatment methods (IMO-International Maritime Organization, 2008).…”