Discovery of a novel potential polyphosphate accumulating organism without denitrifying phosphorus uptake function in an enhanced biological phosphorus removal process

Study of modified ion exchange resins for phosphorus removal from glyphosate by-product salt

In order to achieve the goal of phosphate removal from glyphosate by-product salts, zirconium and zinc ions were successfully loaded onto D202 resin by co-precipitation modification method in this study, and their effectiveness in phosphate removal was evaluated under various conditions. The results of static adsorption experiments showed that the Zr/Zn@D202 resin effectively reduced the phosphate concentration in the glyphosate by-product salts from 10 mg/L to less than 0.1 mg/L, which met the national level emission standard (P < 0.5 mg/L). The adsorption capacity of Zr/Zn@D202 resin was 31.26 mg/g at pH 3, temperature 30 ℃, and adsorption time 2 h. The phosphate removal rate was 99.5%. The phosphate removal efficiency of Zr/Zn@D202 resin was maintained at 92% after five cycles. The samples were characterized by SEM, EDS, XRD, FT-IR and XPS. The characterization results confirmed the successful loading of zirconium and zinc ions, and elucidated that the adsorption mechanism of phosphate mainly involves the increase of the adsorption sites on the surface of the ion-exchange resin and the ion-exchange process. The pseudo-first-order model accurately described the adsorption kinetics, while the adsorption isotherms followed the Langmuir model.

Biological performance and membrane fouling of a microalgal-bacterial membrane photobioreactor for wastewater treatment without external aeration and carbonation

Biological nutrient removal processes involving the use of activated sludge (AS) to treat municipal wastewater normally result in high aeration energy consumption and significant greenhouse gas (GHG) emissions. Therefore, developing cost-efficient and environmentally friendly processes for wastewater treatment is vital. In this work, a novel non-aerated microalgal-bacterial membrane photobioreactor (MB-MPBR) was proposed, and its feasibility for organic contaminant and nutrient removals was evaluated, for the first time. The effects of inoculation ratio (microalgae to bacteria (M/B)) on the biological performance and membrane fouling were systematically investigated. The results showed that 95.9% of the chemical oxygen demand (COD), 74.5% of total nitrogen (TN), 98.5% of NH4+-N and 42.0% of total phosphorus (TP) were removed at an inoculation M/B ratio of 3:2 at steady state, representing a significant improvement compared to the M/B inoculation ratio of 1:3. Additionally, the higher inoculation M/B ratio (3:2) significantly promoted the biomass production owing to the favorable mutual exchange of oxygen and carbon dioxide between microalgae and bacteria. Cake layer formation was the primary fouling mechanism owing to the absence of aeration scouring on the membrane surface. The membrane fouling rate was slightly higher at the higher inoculation ratio (M/B = 3:2) owing to the increased biomass and extracellular polymeric substances (EPS) productions, despite the larger particle size. These results demonstrated that the non-aerated MB-MPBR could achieve superior biological performance, of which the inoculation M/B ratio was of critical importance for the initiation and maintenance of microalgal-bacterial symbiotic system, yet possibly caused severer membrane fouling in the absence of external aeration and carbonation. This study provides a new perspective for further optimizing and applying non-aerated MB-MPBR to enhance municipal wastewater treatment.