Septic tank
A septic tank is an underground chamber made of concrete, fiberglass or plastic through which domestic wastewater (sewage) flows for basic treatment. Settling and anaerobic processes reduce solids and organics, but the treatment efficiency is only moderate (referred to as "primary treatment"). Septic tank systems are a type of simple onsite sewage facility (OSSF). They can be used in areas that are not connected to a sewerage system, such as rural areas. The treated liquid effluent is commonly disposed in a septic drain field which provides further treatment. However, groundwater pollution may occur and can be a problem.
Water supply and sanitation in the Philippines
In 2005 the situation was as follows: Only 5% of the total population was connected to a sewer network.The vast majority used flush toilets connected to septic tanks. Since sludge treatment and disposal facilities were rare, most effluents were discharged without treatment. Within the entire country, septic tanks are the most common method of sewage treatment. In Metro Manila alone, about 75 local companies provide tank-desludging services.