Wan Liu,Shan Chen,Han Zhou,Xianyun Wang,Houtao Xu,Liqing Wang,Wei Zhang,Lijing Chen
Sulfonamides (SAs) are the most common and bio-refractory antibiotics detected in surface water systems, which cause long-term toxic effects on aquatic organisms. This study used the combination of a BiVO4photocatalyst and freshwater micro-green alga (Dictyosphaeriumsp.) to remove sulfadiazine (SD) and sulfamethazine (SM2) at an initial concentration of 5 mg/L (1:1v/v) for 7 days. We set up three gradient concentrations of BiVO4(0.5, 1 and 2 g/L) combined with the same concentration (80 mg/L) ofDictyosphaeriumsp. and then prepared corresponding concentrations of pure BiVO4and pure microalgae as controls. We evaluated the ability of BiVO4andDictyosphaeriumsp. combined technology to remove SAs by observing the removal efficiency of antibiotics and explained the degradation mechanism of antibiotics and the key role of microalgae by studying the changes of reactive oxygen species (ROS) and inorganic ions (nitrogen, sulfur). The results showed that the degradation rate of these two SAs in the 0.5 g/L BiVO4–algae group could reach >96% within 7 d, which was higher than that in the 2 g/L BiVO4group (93%) and the algae group (28%). The increased degradation efficiency of SAs in BiVO4and microalgae systems was mainly due to the increased amount of ROS. Meanwhile, more SAs were degraded to inorganic compounds such as NH4+-N, NO3−-N and SO42−-S under ROS stress. It was found that microalgae can absorb the degradation products of antibiotics such as NH4+-N for their own growth, thereby reducing the toxicity of antibiotic by-products. In addition, BiVO4had no damaging effect on the autofluorescence intensity of the microalgae. Our study provides an efficient and eco-economic approach to remove antibiotics using visible-light irradiation in aquatic environments and provides new insights into the biological removal of other antibiotic contaminants in aquatic environments.Keywords:Dictyosphaeriumsp.;BiVO4;sulfamethazine;sulfadiazine;reactive oxygen species;NH4+-N
The widespread adoption of anaerobic digestion in manure management necessitates handling discharged ammonia–nitrogen (NH 4 + -N)-rich digestate, where electrochemical ammonia recovery is a viable solution but is limited by the cost of membrane fouling. Here, we present a membrane-free ion enrichment electrolyzer (MIEE) engineered with an electrode spatially decoupled structure, enabling NH 4 + and OH – ion enrichment in the anaerobic digestate for further ammonia recovery. Through in-situ measurements, we identify electrochemically induced relative concentration gradients of ions as the pivotal mechanism driving ion enrichment. MIEE maintains electroneutrality by migrating ions, and the effect is close to electrodialysis below ∼50 % migration of NH 4 + ions. Cathode effluent treated by MIEE achieves ∼80 % ratio of NH 4 + -N recovery in the stripping process, coupled with carbon mitigation. The cost of OH – ions supplied by MIEE is ∼50 % compared to directly dosing NaOH. The anode effluent neutralizes the stripping effluent pH from 9.3 to 8.6 and optimizes the organic carbon/nitrogen molar ratio from 1.5 to more than 3, enhancing compatibility with the bioprocess. This study presents a novel strategy for enriching ions without ion exchange membranes, which reduces the cost of membranes and stripping pretreatment in the ammonia recovery.
Lin Zhu,Caihong Huang,Wei Li,Weixia Wu,Zhurui Tang,Yu Tian,Beidou Xi
Nitrogen loss from compost is a serious concern, causing severe environmental pollution. The NH 4 + -N content reflects the release of NH 3 . However, the nitrogen conversion pathway that has the greatest impact on NH 4 + -N content is still unclear. This study attempted to explore the key pathways, core functional microorganisms, and mechanisms involved in the transformation of ammonia nitrogen during composting. KEGG (Kyoto Encyclopedia of Genes and Genomes) metabolic pathways revealed that ammonia assimilation was dominated by the glutamate dehydrogenase (GDH) pathway (53.4%), which is crucial for nitrogen preservation. The combined analysis of KEGG, NR species annotation, and co-occurrence network identified 20 easy-to-regulate obligate core nitrogen-transforming functional microorganisms, including 18 ammonia-assimilating bacteria. Furthermore, the effects of environmental parameters on the obligate core functional microorganisms were investigated. The present study results provided a theoretical basis for the utilization of ten ammonia-assimilating bacteria, such as Paenibacillus , Erysipelatoclostridium, and Defluviimonas to improve the quality of compost.
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