An Integrated Approach to Lysis-Cryptic Growth (Sludge Ozonation) and Sequencing Batch Reactor Coupled to an Anaerobic Side-Stream Reactor (SBR-ASSR): Performance and Characteristics

Anaerobic side-stream reactors (ASSR) have been suggested to reduce waste activated sludge volumes benefiting from relatively low capital/operation costs and design simplicity. In this study, an evaluation of the feasibility of combining the ASSR system with the lysis-cryptic growth (ozonation) process was made so that a part of the sludge which passed through the ASSR anaerobic tank would be then treated by ozonation before returned to the aeration tank. The main independent factor was the ozonation flowrate (OFR), which is defined as the percent of return sludge which passed through the both the anaerobic tank and the ozonation unit. Three systems were studied, an ASSR control without ozonation (OFR-0), a combined ASSR with ozonation designated as OFR-2.5 (anaerobic interchange rate [AIR] of 10% per day and 25% of the exchanged sludge being ozonated [ozone interchange rate or OIR]), and OFR-3.1 (AIR = 12.5%, OIR = 25%). The results revealed that the insertion of an ozonation step led to an enhanced total microbial activity, eukaryotic population, and nitrogen removal. The linear relationship between the observed yield and the specific oxygen uptake rate indicated that microbial predation was the major relevant mechanism for the enhanced sludge reduction. The results of measurements of particle size distribution, and sludge dewaterability rates suggest that additional studies are needed to better understand and optimize this system.