Abstract
Crude oil contamination of water poses serious environmental and public health risks due to its persistence and toxicity. This study evaluated the effectiveness of natural biocarriers, cassava mash (CM), maize bran (MB), and soursop peel (SP) in enhancing the bioremediation of crude-oil-polluted water using Aspergillus niger. The objectives were to: (i) characterize the nutrient composition of the biocarriers, (ii) assess changes in water quality indicators before and after contamination, (iii) monitor bioremediation-indicating parameters during treatment, and (iv) determine the extent of total petroleum hydrocarbon (TPH) reduction over 35 days. Initial contamination significantly degraded water quality, with BOD increasing from non-detectable (ND) to 14.32 mg/L, COD rising from ND to 16.02 mg/L, DO decreasing from 7.2 to 3.16 mg/L, and TPH reaching 1000 mg/L, while pH remained at 7.14. Biocarrier characterization showed high nutrient levels: nitrogen 5.24-5.82%, total organic carbon 75.10-78.61%, phosphorus 18.652-19.898%, potassium 1.023-2.103 ppm, calcium 1.408-2.832 ppm, iron 0.376-0.4217 ppm, protein 6.300-9.102%, and carbohydrates 100.436-155.598 mg/L. During bioremediation, all treated reactors showed steady improvement across key parameters. DO increased progressively, while BOD and COD declined, indicating effective microbial degradation. Microbial population rose sharply, especially in reactors with maize bran and cassava mash. TPH reduction was substantial in all treatments, with maize bran achieving the highest degradation efficiency of 94%, followed by cassava mash 90% and soursop peel 85% over 35 days. Overall, the study demonstrates that nutrient-rich natural biocarriers significantly improve crude oil bioremediation performance. Maize bran proved most effective, followed by cassava mash and soursop peel, offering a low-cost, sustainable solution for treating oil-polluted water.