bacterial bed(A device that removes some suspended solids from sewage. Air and bacteria decompose additional wastes filtering through the sand so that cleaner water drains from the bed)
bacterium(Group of single-cell micro-organisms, the smallest of the living organisms. Some are vital to sustain life, while others are responsible for causing highly dangerous human diseases, such as anthrax, tetanus and tuberculosis. Bacteria are found everywhere, in the soil, water and air)