Cationic thiazine and azo dye along with petroleum hydrocarbon microbial degradation and assessment of physiochemical and radionuclides parameters of targeted point source (water)

Abstract

Background: Water pollution remains a critical environmental and public health issue in Bangladesh, particularly in Dhaka and its surrounding areas. The continuous discharge of untreated sewage, industrial effluents, and chemical wastes has led to the deterioration of aquatic ecosystems, contributing to the emergence of fish and human diseases. Regular monitoring is essential to assess the extent of pollution, track microbial adaptation, and detect potential outbreaks of novel pathogens. Method: Water samples were systematically collected from multiple locations and transported at 4°C to preserve microbial integrity. Selective and differential media were employed to isolate bacteria resistant to hydrocarbons (petrol, kerosene) and azo dyes. Enrichment cultures in Bushnell-Haas broth, supplemented with pollutants as carbon sources and ammonium nitrate as a nitrogen source, facilitated the degradation process over seven days. Gas chromatography was utilized to analyze the breakdown of hydrocarbon pollutants. Molecular identification of isolates was performed using 16S rDNA gene sequencing. For heavy metal and radionuclide analysis, samples were acidified and analyzed using Atomic Absorption Spectroscopy (AAS) for metal quantification, while High-Purity Germanium (HPGe) detectors were used for radionuclide profiling. Results: Radionuclide analysis of surface and groundwater samples from Dhaka showed Th- 232, Ra-226, and K-40 levels within safe limits, indicating no significant radiological risk. Molecular characterization identified Pseudomonas aeruginosa with notable hydrocarbondegrading abilities. Gas chromatography confirmed biodegradation of hydrocarbons like toluene, naphthalene, and hexadecane. However, AAS detected Pb toxic heavy metal exceeding permissible limits in Signboard River and Shitalakha River, indicating localized heavy metal pollution. Conclusions: Overall, the combined microbial and chemical analyses underscore the natural bioremediation potential of indigenous microbes in mitigating hydrocarbon and azo dye pollution in the aquatic environment of Dhaka and its surroundings.