The effect of filtration and electrolysis on ballast water treatment

Abstract

Ballast water is required to be treated to reach D-2 standard according to the International Maritime Organization (IMO). Filtration and electrolysis are important technologies for ballast water management systems (BWMS). However, the clogging of filters during the operation of BWMS leads to significant system trips and downtime. In this paper, a mesoscale experiment system was set up and the effects of filtration on ballast water treatment using electrolysis were investigated. The results showed pore size of filter had significant effect on filtration efficiency, total residual oxidant (TRO) decay and inactivation efficacy. The filtration efficiency of filter with 50 μm pore size was over 80% for ≥50 μm organisms. For 200–2000 μm pore sizes (200 μm, 500 μm, 1000 μm and 2000 μm), the filtration efficiency was less than 10%. The effect of filtration on TRO depended on pore size and holding time. Our results indicated that increasing pore size of electrolysis may not a good way for new BWMS design. If electrolysis was applied alone to treat ballast water, higher initial TRO concentration was needed. In our investigation, the initial TRO was more than 12 mg/L.