Pengaruh Penambahan Dispersan pada Kinerja Proses Bioremidiasi Air laut Tercemar Minyak Bumi menggunakan Bacillus subtilis CYA27

Abstract

Eksplorasi dan pengolahan minyak bumi menghasilkan limbah limbah Bahan Berbahaya dan Beracun (B3) yang bersifat toksik dan karsinogenik. Bioremediasi merupakan pendekatan ramah lingkungan untuk mengatasi tumpahan minyak di laut dengan memanfaatkan bakteri, yang kinerjanya dapat ditingkatkan melalui penambahan surfaktan sebagai pengemulsi. Penelitian sebelumnya menunjukkan bahwa kombinasi Bio-OSD dan Bacillus subtilis CYA27 mampu mendegradasi 56,36% cemaran minyak pada pasir yang terkontaminasi minyak. Diperlukan uji lebih lanjut di perairan laut untuk mengevaluasi efektivitas sebagai solusi penanganan tumpahan minyak. Metode penelitian dimulai dengan peremajaan dan pembuatan kurva pertumbuhan bakteri Bacillus subtilis CYA27, diikuti dengan uji bioremediasi dan toksisitas. Bioremediasi crude oil dilakukan pada erlenmeyer dengan Oil Spill Dispersant (OSD) terhadap minyak sebesar 0,1:1, 0,5:1, dan 1:1, serta penambahan 9% v/v kultur bakteri. Parameter bioremediasi yaitu nilai pH, populasi bakteri, dan penurunan total petroleum hidrokarbon (awal-akhir) diamati selama 14 hari. Uji toksisitas dilakukan untuk mengevaluasi tingkat toksisitas produk OSD serta perlakuan setelah proses bioremediasi. Sebelum pengujian, hewan uji diaklimatisasi terlebih dahulu untuk beradaptasi dengan kondisi lingkungan baru dengan waktu pemaparan selama 24 dan 96 jam. Bioremediasi air terkontaminasi crude oil menggunakan OSD dan B. subtilis CYA27 efektif dalam mendegradasi minyak dilihat dari hasil Total Petroleum Hidrokarbon (TPH) tertinggi pada Bio-OSD dengan (DOR) 0,5:1 yaitu 68,5% dan nilai pH menunjukkan fluktuasi antara 7,15-8,59. Percobaan non-Bio-OSD TPH tertinggi dengan (DOR) 0,1:1 yaitu 40,33% dan pH berfluktuasi pada kisaran 7,61-8,33. Pengamatan jumlah sel menunjukkan bahwa populasi bakteri pada perlakuan Bio-OSD dan non-Bio-OSD mengalami fluktuasi signifikan, dengan kisaran 9,8 × 106 hingga 21 × 106 sel/mL. Uji probit dengan tingkat kepercayaan 95%, Bio-OSD pada konsentrasi 2880,061 ppm (>100 ppm) dikategorikan sebagai “praktis tidak beracun” yang menyebabkan kematian 50% populasi benur udang dalam 96 jam. Nilai LC50 non-Bio-OSD sebesar 36,924 ppm (10–100 ppm), yang tergolong dalam kategori “sedikit beracun”, karena menyebabkan kematian 50% populasi benur dalam durasi 96 jam. Perlakuan setelah bioremediasi Bio-OSD dengan penambahan B. subtilis, nilai LC50 tercatat lebih rendah dibandingkan Bio-OSD tanpa bakteri pada seluruh interval waktu. Hasil penelitian menunjukkan kedua perlakuan tergolong 'sedikit beracun' (LC50 > 10 ppm) pada paparan 24 jam, sedangkan pada paparan 48 hingga 96 jam, nilai LC50 menurun ke rentang 1–10 ppm yang termasuk dalam kategori “cukup beracun”. Perlakuan non-Bio-OSD dengan penambahan B. subtilis menyebabkan penurunan nilai LC50 dibandingkan tanpa bakteri, terutama pada waktu pemaparan 72 dan 96 jam. Paparan 24 jam menunjukkan kedua perlakuan masih tergolong “sedikit beracun” (LC50 >10 ppm). Perlakuan Bio-OSD mengalami penurunan nilai LC50 hingga masuk ke kategori “cukup beracun” (1–10 ppm) dalam rentang waktu 48 hingga 96 jam. Hasil ini mengindikasikan bahwa penambahan B. subtilis cenderung meningkatkan toksisitas media, meskipun toksisitas perlakuan non-Bio-OSD tetap lebih tinggi dibandingkan Bio-OSD di setiap interval waktu setelah bioremediasi air laut tercemar minyak bumi.

Petroleum exploration and processing generate hazardous waste that is both toxic and carcinogenic. Bioremediation represents an environmentally friendly approach to addressing marine oil spills by utilizing bacteria, whose degradation performance can be enhanced through the addition of surfactants as emulsifying agents. Previous studies have demonstrated that the combination of Bio-OSD and Bacillus subtilis CYA27 is capable of degrading up to 56.36% of petroleum contamination in oil-contaminated sand. Further evaluation in marine environments is required to assess its effectiveness as a viable oil spill mitigation strategy. The research began with the rejuvenation and growth curve analysis of Bacillus subtilis CYA27, followed by bioremediation and toxicity testing. Crude oil bioremediation was carried out in Erlenmeyer flasks using OSD-to-oil ratios of 0.1:1, 0.5:1, and 1:1, each supplemented with 9% (v/v) bacterial culture. Bioremediation parameters including pH, bacterial population, and reduction in total petroleum hydrocarbons (TPH) from initial to final values were monitored over a 14-day period. Toxicity tests were conducted to assess the toxicity levels of OSD products and post-bioremediation treatments. Prior to testing, the test organisms were acclimatized to allow adaptation to the new environmental conditions. Toxicity exposure durations were set at 24 and 96 hours. Bioremediation of crude oil-contaminated water using OSD and Bacillus subtilis CYA27 was effective in degrading oil, as indicated by the highest TPH reduction in the Bio-OSD treatment with a dispersant-to-oil ratio (DOR) of 0.5:1, reaching 68.5%. The pH values in this treatment fluctuated between 7.15 and 8.59. In the non-Bio-OSD treatment, the highest TPH reduction was observed at a DOR of 0.1:1, with a value of 40.33%, while the pH ranged from 7.61 to 8.33. Cell count observations revealed that bacterial populations in both Bio-OSD and non-Bio-OSD treatments fluctuated significantly, ranging from 9.8 × 106 to 21 × 106 cells/mL. A probit analysis with a 95% confidence level indicated that Bio-OSD at a concentration of 2,880.061 ppm (>100 ppm) was categorized as “practically non-toxic,” causing 50% mortality in shrimp fry after 96 hours of exposure. In contrast, the LC50 value of non-Bio-OSD was 36.924 ppm (10–100 ppm), classifying it as “slightly toxic,” as it also caused 50% mortality in shrimp fry within 96 hours. The post-bioremediation treatments, the addition of Bacillus subtilis resulted in lower LC50 values compared to treatments without bacterial inoculation at all observation times. At 24 hours of exposure, both Bio-OSD and non-Bio-OSD treatments were classified as “slightly toxic” (LC50 > 10 ppm). From 48 to 96 hours, LC50 values declined to the range of 1–10 ppm, indicating a “moderately toxic” classification. The non-Bio-OSD treatment with B. subtilis showed a greater reduction in LC50 values, particularly at 72 and 96 hours, compared to the treatment without bacteria. In the Bio-OSD treatment, LC50 values continued to decrease over time, falling into the “moderately toxic” category between 48 and 96 hours. These findings suggest that the addition of B. subtilis tends to increase the toxicity of the medium. Moreover, non-Bio-OSD treatments consistently exhibited higher toxicity than Bio-OSD at each observation interval following bioremediation of petroleum-contaminated seawater.