Development of anaerobic sludge bed (ASB) reactor technologies for domestic wastewater treatment: motives and perspectives

During the treatment of raw domestic wastewater in the upflow anaerobic slu dge blanket (UASB) reactor, the suspended solids (SS) present in the wastew ater tend to influence negatively the methanogenic activity and the chemica l oxygen demand (COD) conversion efficiency. These problems led to the emer gence of various anaerobic sludge bed systems such as the expanded granular sludge bed (EGSB), the upflow anaerobic sludge blanket (UASB)-septic tank, the hydrolysis upflow sludge bed (HUSB), the two-stage reactor and the ana erobic hybrid (AH) reactor. However, these systems have, like the UASB reac tor, limited performance with regard to complete treatment (e.g., removal o f pathogens). In this respect, a new integrated approach for the anaerobic treatment of domestic wastewater is suggested. This approach combines a UAS B reactor and a conventional completely stirred tank reactor (CSTR) for the treatment of the wastewater low in SS and sedimented primary sludge, respe ctively. The principal advantages of the proposed system are energy recover y from organic waste in an environmentally friendly way; lowering the negat ive effect of suspended solids in the UASB reactor; production of a high qu ality effluent for irrigation; and prevention of odour problems.