Aerobic granular sludge formation and stability in enhanced biological phosphorus removal system under antibiotics pressure: Performance, granulation mechanism, and microbial successions.

Wastewater containing antibiotics can pose a significant threat to biological wastewater treatment processes. This study investigated the establishment and stable operation of enhanced biological phosphorus removal (EBPR) by aerobic granular sludge (AGS) under mixed stress conditions induced by tetracycline (TC), sulfamethoxazole (SMX), ofloxacin (OFL), and roxithromycin (ROX). The results show that the AGS system was efficient in removing TP (98.0%), COD (96.1%), and NH4+-N (99.6%). The average removal efficiencies of the four antibiotics were 79.17% (TC), 70.86% (SMX), 25.73% (OFL), and 88.93% (ROX), respectively. The microorganisms in the AGS system secreted more polysaccharides, which contributed to the reactor's tolerance to antibiotics and facilitated granulation by enhancing the production of protein, particularly loosely bound protein. Illumina MiSeq sequencing revealed that putative phosphate accumulating organisms (PAOs)-related genera (Pseudomonas and Flavobacterium) were enormously beneficial to the mature AGS for TP removal. Based on the analysis of extracellular polymeric substances, extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and microbial community, a three-stage granulation mechanism was proposed including adaption to the stress environment, formation of early aggregates and maturation of PAOs enriched microbial granules. Overall, the study demonstrated the stability of EBPR-AGS under mixed antibiotics pressure, providing insight into the granulation mechanism and the potential use of AGS for wastewater treatment containing antibiotics.

Effects of pretreatments on thickened waste activated sludge and rice straw co-digestion: Experimental and modeling study.

In order to maximize the biogas production from thickened waste activated sludge (TWAS), co-digestion of TWAS and rice straw (RS) was studied and the application of thermal/thermo-alkaline and NaOH/H2O2 to TWAS and RS, respectively, was evaluated. The batch experiments were conducted at three different TWAS/RS (volume basis) ratios of 1:3, 1:1 and 3:1, respectively. Furthermore, the modified Gompertz model was introduced to predict the biogas yield and evaluate the kinetic parameters. The highest biogas production (409.2 L/kg VSadded) was achieved from co-digestion of TWASthermo-alkaline and RSNaOH at mixing ratio of 1:1, which is greater by 42.2% and 5.9% than that of digesting TWASthermo-alkaline, and RSNaOH alone, respectively. The highest VS removal rate was obtained from the co-digestion of TWASthermo-alkaline and RSNaOH at mixing ratio of 1:3, which is greater by 55.8% and 14.0% than those of mono-digestion. The modified Gompertz model (R(2): 0.993-0.998 and 0.993-0.999 for mono- and co-digestions, respectively) showed a good fit to the experimental results and the estimated parameters indicating that the pretreatments and co-digestion of substrates markedly improved the biogas production rate.

Recent developments in biochar as an effective tool for agricultural soil management: a review.

In recent years biochar has been demonstrated to be a useful amendment to sequester carbon and reduce greenhouse gas emission from the soil to the atmosphere. Hence it can help to mitigate global environment change. Some studies have shown that biochar addition to agricultural soils increases crop production. The mechanisms involved are: increased soil aeration and water-holding capacity, enhanced microbial activity and plant nutrient status in soil, and alteration of some important soil chemical properties. This review provides an in-depth consideration of the production, characterization and agricultural use of different biochars. Biochar is a complex organic material and its characteristics vary with production conditions and the feedstock used. The agronomic benefits of biochar solely depend upon the use of particular types of biochar with proper field application rate under appropriate soil types and conditions. © 2016 Society of Chemical Industry.