Chlorine Dose Optimization for Ballast Water Treatment on the Rear Admiral John Lie Training Ship: Compliance with IMO D-2 Standard and Control of Chlorine Residues

Abstract

Ballast water is one of the main routes for the movement of aquatic organisms, microorganisms, and potentially invasive species between ports. This study evaluated the effectiveness of chlorine in reducing biological indicators in the ballast water of the Rear Admiral John Lie Training Ship and assessed the safety of the remaining chlorine residue after treatment. Ballast water samples were taken while the ship was docked at Bitung Port, North Sulawesi, then treated with sodium hypochlorite at concentrations of 0.5; 1.0; 1.5; 2.0; 5.0; and 10.0 ppm for 60 minutes. Parameters observed included Total Plate Count (TPC), Escherichia coli, free chlorine residual, temperature, pH, and salinity. Data were analyzed descriptively by comparing the treatment results to the IMO D-2 Standard and the oxidant residue threshold. Untreated ballast water contained a TPC of 1,780 colonies/mL and 76 CFU of E. coli/100 mL. The TPC value decreased with increasing chlorine dose and reached <25 colonies/mL only at 10 ppm. E. coli decreased to <1 CFU/100 mL at 2, 5, and 10 ppm. Free chlorine residuals were recorded at 0.07 mg/L at 2 ppm, 0.28 mg/L at 5 ppm, and 1.30 mg/L at 10 ppm. The 2 ppm treatment was the most balanced dose, meeting the tested IMO D-2 biological parameters while maintaining chlorine residuals below 0.1 mg/L. Higher doses provided stronger biological suppression but resulted in excess chlorine residuals, requiring neutralization before discharge.

Keywords: ballast water; E. coli; IMO D-2; invasive species; Total Plate Count

Abstrak.  Air ballast merupakan salah satu jalur utama perpindahan organisme akuatik, mikroorganisme, dan spesies berpotensi invasif antar pelabuhan. Penelitian ini mengevaluasi efektivitas klorin dalam menurunkan indikator biologis pada air ballast Kapal Latih Laksamana Muda John Lie serta menilai keamanan residu klorin yang tersisa setelah perlakuan. Sampel air ballast diambil saat kapal sandar di Pelabuhan Bitung, Sulawesi Utara, kemudian diberi perlakuan natrium hipoklorit pada konsentrasi 0,5; 1,0; 1,5; 2,0; 5,0; dan 10,0 ppm selama 60 menit. Parameter yang diamati meliputi Angka Lempeng Total (Total Plate Count/TPC), Escherichia coli, residu klorin bebas, suhu, pH, dan salinitas. Data dianalisis secara deskriptif dengan membandingkan hasil perlakuan terhadap Standar IMO D-2 dan ambang batas residu oksidan. Air ballast tanpa perlakuan mengandung TPC 1.780 koloni/mL dan E. coli 76 CFU/100 mL. Nilai TPC menurun seiring meningkatnya dosis klorin dan mencapai <25 koloni/mL hanya pada 10 ppm. E. coli menurun menjadi <1 CFU/100 mL pada 2, 5, dan 10 ppm. Residu klorin bebas tercatat 0,07 mg/L pada 2 ppm, 0,28 mg/L pada 5 ppm, dan 1,30 mg/L pada 10 ppm. Perlakuan 2 ppm merupakan dosis paling seimbang karena memenuhi parameter biologis IMO D-2 yang diuji sekaligus mempertahankan residu klorin di bawah 0,1 mg/L. Dosis yang lebih tinggi memberikan penekanan biologis lebih kuat, tetapi menghasilkan residu klorin berlebih sehingga memerlukan netralisasi sebelum pembuangan.

Kata kunci: air ballast; E. Coli, IMO D-2; spesies invasif, Total Plate Count