Biosolids mineralization in an anaerobic–aerobic combined reactor system

In this paper, we describe a biosolids mineralization process that could address some concerns about biosolids management. Solids retention in a combined anaerobic/aerobic reactor system promotes biosolids mineralization. Solids retained in the reactor were subjected to both anaerobic and aerobic degradation in two different zones in the reactor. After 267 d of operation, 75% of the solids that entered the reactors were mineralized, 62% of the total nitrogen (TN) was transformed, 51% of the phosphorus in the reactors was precipitated, and 39% of the solids dissolved and appeared in the effluent. Accumulation of solids in the reactors did not have an adverse effect on reactor performance. Evidence of biosolids degradation included a decrease in the VSS/TSS ratio, an increase in temperature, loss of nitrogen, decrease in COD, and an increase in TDS.