# Bioremediation of hexamine and formaldehyde using a radio-tolerant bacterial consortium for efficient pollutant and COD removal

## TL;DR

A radio-tolerant bacterial consortium was developed to efficiently remove hexamine, formaldehyde, and COD from wastewater.

## Contribution

This is the first report of a radio-tolerant bacterial consortium for hexamine removal, including the first involvement of Brucella pseudintermedia in this process.

## Key findings

- The consortium removed 1.26 g/kg hexamine, 0.87 g/kg formaldehyde, and 185.26 g/kg COD under immobilized conditions.
- Brucella pseudintermedia was identified as a novel participant in hexamine and formaldehyde removal.
- The biofilm-based system showed higher removal efficiency compared to suspended systems.

## Abstract

Hexamine and its by-products (formaldehyde and ammonia) are classified as organic pollutants. Formaldehyde has antibacterial properties, while increased ammonia levels contribute to eutrophication, both of which disrupts microbial communities in aquatic ecosystems. Hexamine is considered a common pollutant released from various industries.

Culture based analysis in enriched medium resulted in development of bacterial consortium using environmental isolates.

A consortium, containing six pure bacterial isolates {SRCHD03 & SRCHD04 (Brevundimonas diminuta), SRCHD05 & SRCHD07 (Brucella pseudintermedia), SRCHD06 (Ochrobactrum sp.), and SRCHD02 (Micrococcus luteus)} showed the ability to remove 1.26 g/kg hexamine associated with 0.87 g/kg of formaldehyde and 185.26 g/kg of Chemical Oxygen Demand (COD) at 96 hours of incubation under immobilized condition after 5.25 Gray of 60Co γ irradiations, starting from an initial concentration of 50 mg/L hexamine and 13367 mg/L COD, hence reporting the first radio tolerant consortium for hexamine removal.

Involvement of Brucella pseudintermedia in hexamine and formaldehyde removal is being reported for the first time. The radio tolerant consortium in biofilm-based system showed enhanced hexamine, formaldehyde and COD removal efficiency compared to its suspended counterpart. This is a potential microbial formulation for the removal of hexamine and formaldehyde from stimulated wastewater.

Diagram illustrating the process of hexamine bioremediation. Wastewater undergoes hexamine removal and microbial identification to form Consortium C6. Consortium is immobilized in a biofilm and exposed to gamma rays from Cobalt-60. This treatment reduces hexamine, formaldehyde, and COD, as shown by downward arrows beside the effluent. The process is labeled "Bioremediation of Hexamine."