Black water: A mixture of urine, faeces and flush water along with anal cleansing water (if water is used for cleansing), and/or dry cleansing materials. Black water contains pathogens of faeces and the nutrients of urine that are diluted in the flush water.
Desludging or Emptying: The operation of removing sludge (and septage) from septic tanks, pit latrines or any other primary treatment units is called de-sludging.
Effluent: The supernatant liquid discharged from a septic tank. The liquid separated out from the septage is also referred to as effluent.
Faecal sludge: The settled contents of pit latrines and septic tanks. It differs from sludge produced in municipal wastewater treatment plants. The characteristics of faecal sludge can differ widely from household to household, city to city, and country to country. The physical, chemical and biological qualities of faecal sludge are influenced by the duration of storage, temperature, soil conditions, and intrusion of groundwater or surface-water into septic tanks or pits, performance of septic tanks, and tank emptying technology and pattern.