Tag: biology

Biogas is produced due to the anaerobic fermentation of the slurry of animals dung.
Microbial conversion of organic matter to methane has become attractive as a method of waste treatment and resource recovery. This process is anaerobic and is carried out by action of various groups of anaerobic bacteria.
Three basic points about this process are that most of the important bacteria involved in biogas production process are anaerobes and slow growing, a greater degree of metabolic specialization is observed in these anaerobic microorganisms and that most of the free energy present in the substrate is found in the terminal product methane. Since less energy is available for the growth of organism, less microbial biomass is produced and, consequently, disposal of sludge after the digestion may not be a major problem.

Sewage is defined as wastewater that contains a mixture of liquid waste from households and organic matter, such as human excreta and food scraps. It is not purely liquid or solid, but a suspension of materials in water.

Aeration is mixing of oxygen into the water. It increases the microbial growth in the water. The microbial growth acts on the organic matter and creates flocs which settle. The degradation of organic matter leads to the change in the pH of the water and production of gases like hydrogen sulfide which creates an odour.

Nitrogen in wastewater primarily comes from organic nitrogen sources. Urea is a major component of human waste and a significant source of nitrogen in domestic sewage.

The final passageway for urine out of the bladder is through the thin walled urethra. This tube runs from the base of the urinary bladder to the outside of the body.

Malpighian tubules are found lining the gut of some species of arthropods, such as the bee. They are usually found in pairs and the number of tubules varies with the species of insect. Malpighian tubules are convoluted, which increases their surface area, and they are lined with microvilli for reabsorption and maintenance of osmotic balance. Malpighian tubules work cooperatively with specialized glands in the wall of the rectum.

The nitrogen-containing compounds excreted by the sculpin, starry flounder, and blue sea-perch were profusely under research. Approximately four-fifths of the nitrogenous material was excreted via the gills. Ammonia and urea were the main components of the excreta in all three species.

Nephridia are the invertebrate excretory organ that performs a function similar to the vertebrate kidney. These are small coiled tubes. Leech contains 17 pairs of nephridia arranged segmentally.