Incorporating the oxic‐settling‐anaerobic (OSA) process into an anoxic–oxic system for sewage sludge reduction and nutrient removal

Abstract

The production of sludge in biological wastewater treatments is a growing problem worldwide as it entails economic, environmental, and health problems. The oxic‐settling‐anaerobic (OSA) process is one of the techniques that have been developed to reduce the sludge produced in the activated sludge process (ASP). This article reports the feasibility of the application of the OSA process in a nutrient removal system, specifically, in an anoxic–oxic (A) process. The results reveal TN removal in the A + OSA system of 68.84% and 69.91% (for 7 and 11 h of sludge anaerobic exposure time, SAET, respectively) versus 38.02% and 32.47% in the OSA system with similar SAET. The percentage sludge reductions obtained were, respectively, 22.41% and 31.93% in the OSA system and 23.53% and 32.49% in the A + OSA system compared to the sludge produced in the conventional ASP. The study confirms the suitability of the application of the OSA process in a nutrient removal system, as nutrient removal performances are not affected, while at the same time achieving higher sludge reduction. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1068–1074, 2018

Insights on mechanisms of excess sludge minimization in an oxic-settling-anaerobic process under different operating conditions and plant configurations

“…Compared with the available studies carried out with real wastewater on WWTP configured according to BNR schemes (Coma et al, 2015;Romero Pareja et al, 2018;Nikpour et al, 2020;Ferrentino et al, 2021), the results of the present study indicated that the excess sludge reduction was higher when implementing the scheme B. Thus, a double-growth limitation strategy consisting in a prolonged substrate limitation after a sufficient long retention under anaerobic condition, allowed obtaining a higher excess sludge minimization.…”

Minimizing biological sludge generation in a sidestream enhanced biological phosphorus removal (S2EBPR) system: full-scale evaluation and modeling insights

“…In the literature, reports on the effect of OSA-like processes on sludge settleability are often controversial, as SVI value have been reported to both improve or worsen after OSA implementation. 4,[32][33][34] For instance, the studies by Corsino et al 4 and Pareja et al 35 report a reduction in SVI values up to 73% after implementing a CAS with the OSA process operated with a HRT SSR between 7 and 12 h. In contrast, under similar HRT SSR (3-9 h), Corsino et al 17 and Torregrossa et al 32 observed an increase in SVI value up to 77%. Furthermore, these results do not allow for a clear deduction regarding the impact of the system scale (pilot-or laboratory-scale) and influent type (synthetic or real wastewater) on sludge settleability, as a different combination of these operating conditions can be found in the studies aforementioned.…”

“…Generally, the proliferation of PAO has a positive impact on sludge settleability, as these bacteria tend to aggregate in dense clusters which contribute to preserving good settling properties for the sludge. 35…”

Simulation of an Oxic-Settling-Anaerobic Pilot Plant Operated under Real Conditions Using the Activated Sludge Model No.2d

“…The pilot plant was equipped with pH, ORP, temperature, and dissolved oxygen (DO) probes and a programmable logic controller (PLC). Although DO concentration in the activated sludge process (aerobic reactor) is usually set at 2 mg/L, in the present work, a higher concentration was selected based on previous studies on OSA process [4,[8][9][10], which reported a wide range of DO concentrations, ranging from 2 to 7 mg O 2 /L. The DO set-point concentration into the aerobic tank of this study was 4.0 mg O 2 /L, providing also the mixing of the aerobic reactor.…”

“…In recent years, the combination of the OSA process with other technologies capable of sludge volume reduction, such as thermal and mechanical treatment, was also studied [7,8]. Although the implementation of an additional tank in the return sludge line increases the investment cost, OSA process is an environmental-friendly technology with several advantages: (i) the proven excess sludge reduction [1,4,9,10], (ii) the process stability, and (iii) the easy implementation in current conventional activated sludge system (CAS) associated to low operational costs [3,11].…”