The temperature phased anaerobic biofilter-ASBR system is a new system that has been developed at Iowa State University. The temperature phased system employs a first stage thermophilic (55°C) biofilter reactor followed in series by a second stage mesophilic (35°C) anaerobic sequencing batch reactor (ASBR). The idea of temperature phased anaerobic treatment is to eliminate the disadvantages of both thermophilic (poor organic removals) and mesophilic (long retention times) temperatures while retaining the advantages of both these temperatures (fast reaction rates at thermophilic temperatures and good organic removal efficiencies at mesophilic temperatures);Three temperature phased systems were operated in the laboratory for the duration of this study. The systems were fed nonfat dry milk at hydraulic retention times (HRTs) ranging from 14 to 30 hours. This was accomplished by operating the second stage ASBRs at constant HRTs of 24, 18, and 12 hours, and changing the HRT of the first stage biofilters between 6 and 2 hours;The temperature phased system was able to achieve TCOD removals in excess 90% at system loads up to 26.8 g COD/L/day and SCOD removals in excess of 94% at these same organic loads at all HRTs tested. The temperature phased system performed equally at all HRTs and organic loads tested with the largest difference in organic removal efficiency between operating conditions of 5%;The second stage mesophilic ASBR was able to compensate for the declining efficiency of the first stage thermophilic unit as organic load was increased. Volatile fatty acid production remained low in the second stage ASBR even as volatile fatty acid production increased dramatically in the first stage biofilter. The concentration of propionic acid was greater in the first stage biofilter than the concentration of acetic acid with both acids being degraded in the second stage ASBR;The temperature phased system is a stable and resilient system as evidenced by its quick and complete start-up 54 hours after a 14 day shutdown. Overall, the temperature phased system performs better than either a thermophilic biofilter or a mesophilic ASBR operated with the same substrate and at similar organic loads and HRTs.