A by-product of sewage treatment is usually a semi-solid waste or slurry, called sewage sludge, that has to undergo further treatment before being suitable for disposal or land application.
Life expectancy is defined statistically as the average number of years remaining for an individual or a group of people at a given age.Longevity refers to the characteristics of the relatively long life span of some members of a population.athematically, life expectancy is the mean number of years of life remaining at a given age, assuming constant mortality rates. It is denoted by, which means the average number of subsequent years of life for someone now aged, according to a particular mortality experience.
Life Expectancy (With International Comparison) Life expectancy is a summary mortality measure often used to describe the overall health status of a population. Life expectancy is defined as the average number of years a population of a certain age would be expected to live, given a set of age-specific death rates in a given year. Healthy People 2020 monitors 2 life expectancy measures: Life expectancy at birth. Life expectancy at age 65.