Physico-chemical characteristics and biodegradability of primary effluent and particulate matter removed by microscreens.

Abstract

In this study, the physical, chemical, and biological characteristics of raw wastewater were compared with the liquid and solid streams generated by a primary clarifier (PC), a rotating belt filter (RBF, 350 μm), and a drum filter (DF, 60 μm) and series (SER) combination of an RBF with a PC or a DF using pilot-scale primary treatment units. The RBF removed about 36% of the influent total suspended solids. The DF and PC yielded an influent total suspended solid removal of 47% to 55% in both individual (parallel) and SER configurations. The size fractionation and chemical characterizations of the liquid fractions indicated a significant change in the wastewater composition in both filter configurations with no variation in the biodegradability of liquid fractions. The solids recovered by RBF had a higher total solids (TS) concentration and a higher volatile solids (VS) content (0.92 g VS/g TS) than that of DF and PC treatments (0.58 to 0.84 g VS/g TS). DF and PC sludge demonstrated a higher biodegradability rate (k1 ; 0.11 d-1 < k1 < 0.20 d-1 ) than solids recovered by RBF (0.09 d-1 ). The retained solids in the SER configuration demonstrated a significantly lower theoretical biochemical methane potential than the parallel configuration, likely due to the presence of smaller particles with a significantly higher ratio of particulate chemical oxygen demand over volatile suspended solids (1.86 to 2.40 g chemical oxygen demand/g volatile suspended solids). These results indicated that the physical, chemical, and biological characteristics of liquid and solids from different filter configurations are required to determine design criteria to upgrade or retrofit water resource recovery facilities using an RBF or a DF. PRACTITIONER POINTS: A rotating belt filter (RBF) removed less solids than a drum filter (DF) or a primary clarifier (PC). A series configuration of an RBF with either a DF or PC resulted in an effluent with a lower proportion of slowly biodegradable organic matter than in a parallel configuration. Solids from an RBF, a DF, or a PC had similar theoretical biochemical methane potential.