Ultraviolet light kills bacteria in wastewater without the use of chemicals. This reliable and environment friendly method was used in the project Clean Isar in Germany.
Links:
[1] http://admin.indiaenvironmentportal.org.in/feature-article/application-uv-wastewater-treatment
[2] http://admin.indiaenvironmentportal.org.in/category/author/daniela-hornung
[3] http://admin.indiaenvironmentportal.org.in/category/journal/everything-about-water
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/sewage-treatment-technology
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/wastewater-treatment-cost
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/wastewater-recycling
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/germany