Physical-chemical and biological evaluation in commercial treatment systems in Costa Rica

In Costa Rica, 70.9% of the population uses the septic tank as an individual treatment system for domestic wastewater. Although septic tanks are the most used treatment technology in the country, there is no detailed information about their operation and efficiency. The maintenance tasks, such as the removal of septic sludge, was carried out directly by each family that uses this system, using their own resources. The evaluation was carried out in treatment systems manufactured by one of the most important private companies in the country. Each equipment consists of a septic tank and an upflow anaerobic filter for the treatment of domestic wastewater. The evaluation included a physical, chemical and biological characterization of the quality and quantity of wastewater produced in three different treatment systems, considering hourly variations, as well as the characterization of the quality and quantity of sludge accumulated in each system. The treatment systems were installed in two multifamily buildings and a single-family house. The results indicated that the treatment systems are very sensitive in terms of quantity and quality of wastewater, presenting significant hourly variations and also affected by the type of water use that occurs in homes: which is directly related to the operation of the treatment.