Survey of full-scale sidestream enhanced biological phosphorus removal (S2EBPR) systems and comparison with conventional EBPRs in North America: Process stability, kinetics, and microbial populations.

Sidestream EBPR (S2EBPR) is an emerging alternative process to address common challenges in EBPR related to weak wastewater influent and may improve EBPR process stability. A systematic evaluation and comparison of the process performance and microbial community structure was conducted between conventional and S2EBPR facilities in North America. The statistical analysis suggested higher performance stability in S2EBPR than conventional EBPR, although possible bias associated with other plant-specific factors might have affected the comparison. Variations in stoichiometric values related to EBPR activity and discrepancies between the observed values and current model predictions suggested a varying degree of metabolic versatility of PAOs in S2EBPR systems that warrant further investigation. Microbial community analysis using various techniques suggested comparable known candidate PAO relative abundances in S2EBPR and conventional EBPR systems, whereas the relative abundance of known candidate GAOs seemed to be consistently lower in S2EBPR facilities than conventional EBPR facilities. 16S rRNA gene sequencing analysis revealed differences in the community phylogenetic fingerprints between S2EBPR and conventional facilities and indicated statistically higher microbial diversity index values in S2EBPR facilities than those in conventional EBPRs. PRACTITIONER POINTS: Sidestream EBPR (S2EBPR) can be implemented with varying and flexible configurations, and they offer advantages over conventional configurations for addressing the common challenges in EBPR related to weak wastewater influent and may improve EBPR process stability. Survey of S2EBPR plants in North America suggested statistically more stable phosphorus removal performance in S2EBPR plants than conventional EBPRs, although possible bias might affect the comparison due to other plant-specific factors. The EBPR kinetics and stoichiometry of the S2EBPR facilities seemed to vary and are associated with metabolic versatility of PAOs in S2EBPR systems that warrant further investigation. The abundance of known candidate PAOs in S2EBPR plants was similar to those in conventional EBPRs, and the abundance of known candidate GAOs was generally lower in S2EBPR than conventional EBPR facilities. Further finer-resolution analysis of PAOs and GAOs, as well as identification of other unknown PAOs and GAOs, is needed. Microbial diversity is higher in S2EBPR facilities compared with conventional ones, implying that S2EBPR microbial communities could show better resilience to perturbations due to potential functional redundancy.

The price of associating with breeders in the cooperatively breeding chestnut-crowned babbler: foraging constraints, survival and sociality.

Understanding the costs of living with breeders might offer new insights into the factors that counter evolutionary transitions from selfish individuals to cooperative societies. While selection on early dispersal is well understood, it is less clear whether costs are also associated with remaining with family members during subsequent breeding, a prerequisite to the evolution of kin-based cooperation. We propose and test the hypothesis that living in groups containing breeders is costly and that such costs are exacerbated by increasing group size. For example, in group-living central-place foragers, group members might suffer from resource depletion when foraging in a restricted area during breeding and significant costs of repeatedly travelling between foraging patches and the site of offspring. Using the cooperatively breeding chestnut-crowned babbler (Pomatostomus ruficeps), for which grouping during breeding is obligatory, we show that reproduction is associated with substantially reduced foraging areas and evidence of resource depletion, particularly in larger groups. Such effects largely persisted from the onset of incubation through to offspring independence 4-5 months later. All group members, irrespective of their breeder or helper status, lost significant body mass over this period, and, in males, mass loss was associated with reduced interannual survival. Although babblers are constrained from living outside of breeding groups due to high risks of predation and the poor success of breeding without helpers, we suggest that the effects we describe may generally select against group living during breeding attempts in species where constraints to independent breeding and costs of dispersal are less acute.