<p>This paper is about the major biological treatment processes for wastewater that include activated sludge processes, aerated lagoons or stabilization ponds, trickling filters or fixed-film reactors, and anaerobic processes.</p>

<p>In this study the behaviour of an uplow anaerobic sludge bed filter (UBF) and an upflow anaerobic filter (UAF) treating a landfill leachate was investigated.</p>