The indiscriminate use of heavy metalsHeavy metals and radionuclidesRadionuclides for anthropogenic purposes has brought significant increase in their presence above the permissible limits causing disturbances in the ecosystem. Industrial effluents are major contributors to terrestrial and aquatic contamination with toxic heavy metalsHeavy metals like arsenicArsenic, nickel, zinc, copper, chromium, lead, mercuryMercury, cadmiumCadmium, etc., and radionuclidesRadionuclides like uranium, thorium, radon, etc., whose high solubility in the aquatic environments attributes to their hazardous bioaccumulative nature. Various approaches used to degrade such pollutants include physical, chemical, and biological methods. Though none of these methods claim complete degradation of the toxic pollutants, biological techniques are comparatively more effective, economically viable, and environment-friendly, mainly reducing the secondary pollution and by-product accumulation caused by physiochemical methods. Using microbes as the platform for remediation and degradation of heavy metal and radionuclide waste is an alternative yet effective method administered in the recent times. Various processes such as enzymatic transformation including dissolution of pollutants by low molecular weight acidic microbial metabolic secretions or reduction of heavy metalsHeavy metals coupled to anaerobic oxidationAnaerobic oxidation of organic substrates; biosorptionBiosorption of ions to cell wall layers of microbes; and bioconversionBioconversion and precipitation are used by microbes to degrade or reduce heavy metalsHeavy metals into less toxic innocuous forms. This chapter highlights the biological treatment strategies that may replace or augment existing chemical processes and elaborates on various methods in which microbes are used to remove the most common toxic heavy metalsHeavy metals and radionuclidesRadionuclides found in wastewaterWaste Water.