The upflow anaerobic sludge blanket reactor (UASB) is a single tank process used for the biological treatment of wastewater. Wastewater enters the reactor from the bottom, and flows upward. A suspended sludge blanket filters and treats the wastewater as the wastewater flows through it. Biogas, which is produced during the process can be collected and reused. Effluent requires a further treatment step to remove pathogens. Sludge can be composted and/or dried before safe disposal or reuse in agriculture as soil amendment.