The A-stage process to promote bioflocculation and microbial storage for carbon redirection: current perspectives and future research directions

Going Beyond Carbon Redirection: Integrating Operational Conditions to Maximize Carbon and Phosphorus Removal in the A-Stage Process

“…Still, the good performance, especially in terms of COD handling, at such a long SRT (4 days) is worth further investigation as it conflicts with all reports on A-stage systems. , On the other hand, the present study is the first to investigate P-removal using AAA along with COD handling while using wastewater composition that mimics real wastewater. With particulates representing 50–60% of the influent fraction, SRT cannot be increased to reach such values without deteriorating COD redirection due to hydrolysis …”

“…1 Among proposed WRRF technologies, the adsorption/bio-oxidation (A/B) process provides applicable opportunities to shift WWTPs to WRRF, given its readiness level and compatibility to be integrated into existing infrastructure. 2 The A/B process is a two-stage process in which high-rate conditions are applied in the A-stage to maximize organic redirection to the solid stream for recovery. Such high-rate conditions could reach retention times 5−10 times lower than those of the conventional activated sludge (CAS) process.…”

“…11,12 Furthermore, maintenance of the phosphorusaccumulating organisms (PAOs) at such short SRT and HRT levels was never reported. 2 Hence, further research is still needed to balance carbon redirection and removal along with maximizing P removal.…”

“…For example, Li et al reused the unsaturated activated carbon from the postphysicochemical unit for a COD reduction in raw wastewater and proposed the A–OHO process as a water treatment system for resource management . Among proposed WRRF technologies, the adsorption/bio-oxidation (A/B) process provides applicable opportunities to shift WWTPs to WRRF, given its readiness level and compatibility to be integrated into existing infrastructure . The A/B process is a two-stage process in which high-rate conditions are applied in the A-stage to maximize organic redirection to the solid stream for recovery.…”

“…Applying the aforementioned conditions has failed to maximize both carbon redirection and carbon oxidation. For example, it was reported that running the system at SRT of 0.2–0.3 days and HRT of 0.5–0.6 h can lead to carbon redirection above 50%, but with carbon removal less than 65%. , Furthermore, maintenance of the phosphorus-accumulating organisms (PAOs) at such short SRT and HRT levels was never reported . Hence, further research is still needed to balance carbon redirection and removal along with maximizing P removal.…”