 In some cases, considerations that fall within the field of social sciences and urban planning must be factored in as well.Although sanitary engineering may be most associated with the design of sewers, sewage treatment and wastewater treatment facilities, recycling centers, public landfills and other things which are constructed, the term applies equally to a plan of action to reverse the effects of water pollution or soil contamination in a specific area.Irrigation systems were invented five to seven thousand years ago as a means of supplying water to agriculture-based societies.