Hexamine a Major Wastewater Pollutant: The Complete Story

Hexamethylenetetramine (HMT) (often known as methenamine, urotropine, and hexamine) is the heterocyclic non-aromatic amine (CH2)6N4 with a symmetrical three-dimensional structure. It is one of the most recalcitrant pollutants, which is generated from rubber manufacturing units (additive), plastic manufacturing units, explosive production plants, phenolic resins, pharmaceutical industry discharge, and sewage, to name a few. Its degradation under acidic conditions produces formaldehyde and ammonia. HMT and its by-products (formaldehyde, formic acid, ammonia, and nitrate) constitute the majority of the effluents, which have a detrimental effect on the ecosystem, and its vapor can lead to different toxic effects on the human body. As it has an adverse impact on the environment, it needs to be treated. There are different conventional treatments, which include both the physicochemical and biological steps, each with its own limitations. Bibliographic data analysis of the past 10 years shows only 39 papers on hexamine removal while 4089 and 18,877 papers on formaldehyde and ammonia removal as opposed to 89,565 papers on wastewater treatment, revealing hexamine remediation as a relatively less explored area. Ongoing research in some groups focuses on the degradation of this pollutant efficiently, through an environment-friendly, effective, sludge-free, and economical biological treatment method. This article proposes to present an overall detail of HMT related to its structure, properties, mechanisms of degradation, and possible approach for the development of suitable microbial solutions.