Microbial composition and nitrogen removal pathways in a novel sequencing batch reactor integrated with semi-fixed biofilm carrier: evidence from a pilot study for low- and high-strength sewage treatment.

The sequencing batch reactor (SBR) activated sludge process is a well-established technology for sewage treatment. One of the drawbacks of SBRs, however, total nitrogen (TN) removals is insufficient. By means of introducing four improvements, including semi-fixed biofilm carrier, sludge elevation mixing and change for the mode of influent and effluent, compliant standard for TN discharge was obtained in this novel SBR configuration during low- and high-strength sewage load. To illustrate the microbial compositions and functions of the attached biofilm on semi-fixed carrier and the suspended aggregates, as well as the nitrogen removal pathway, high throughput 16S rRNA gene amplicon sequencing, PICRUSt2 algorithm, and KEGG database were applied. The results revealed that (i) the microbial communities from suspended aggregates and biofilm samples were significantly different from each other; (ii) during low-strength sewage loads, TN removal was mainly by nitrification-denitrification. The suspended aggregates was responsible for denitrification, while the biofilm was focused on ammonium oxidation; (iii) during high-strength sewage loads, function of nitrate reductase from suspended aggregates was faded, and anammox and N assimilation by biofilm became dominant. Meanwhile, TN removal referring to the formation of L-glutamine via assimilation was the main pathway.

Effects of ultrasound on invasive golden mussel Limnoperna fortunei mortality and tissue lesions.

Biofouling by the invasive golden mussel Limnoperna fortunei deleteriously affects artificial water systems, but few effective, environmentally friendly antifouling strategies exist. We propose ultrasound for control of this invasive mussel and report minimum exposure times to kill juveniles and adults at ultrasonic powers ranging 300-600 W from a fixed distance of 8.5 cm. Analysis using a PMA + RT-qPCR assay revealed the formation of tissue lesions in response to ultrasound, with gill tissue more prone to injury than adductor muscle tissue. Shell microstructure determined using scanning electron microscopy (SEM) + energy dispersive X-ray spectroscopy (EDS) is plywood-like, with a thicker shell and increased numbers of prism and nacre layers in adult mussels that provide greater resistance to ultrasound, reducing mortality and tissue lesions. Our results suggest L. fortunei biomass could be effectively reduced by ultrasound, especially for early life-history stages without, or with only immature shells.