Enhancing simultaneous nitrogen and phosphorus availability through biochar addition during Chinese medicinal herbal residues composting: Synergism of microbes and humus.

The disposal of Chinese medicinal herbal residues (CMHRs) derived from Chinese medicine extraction poses a significant environmental challenge. Aerobic composting presents a sustainable treatment method, yet optimizing nutrient conversion remains a critical concern. This study investigated the effect and mechanism of biochar addition on nitrogen and phosphorus transformation to enhance the efficacy and quality of compost products. The findings reveal that incorporating biochar considerably enhanced the process of nutrient conversion. Specifically, biochar addition promoted the retention of bioavailable organic nitrogen and reduced nitrogen loss by 28.1 %. Meanwhile, adding biochar inhibited the conversion of available phosphorus to non-available phosphorus while enhancing its conversion to moderately available phosphorus, thereby preserving phosphorus availability post-composting. Furthermore, the inclusion of biochar altered microbial community structure and fostered organic matter retention and humus formation, ultimately affecting the modification of nitrogen and phosphorus forms. Structural equation modeling revealed that microbial community had a more pronounced impact on bioavailable organic nitrogen, while humic acid exerted a more significant effect on phosphorus availability. This research provides a viable approach and foundation for regulating the levels of nitrogen and phosphorus nutrients during composting, serving as a valuable reference for the development of sustainable utilization technologies pertaining to CMHRs.

Attenuation effects of ZVI/PDS pretreatment on propagation of antibiotic resistance genes in bioreactors: Driven by antibiotic residues and sulfate assimilation.

Sulfate radical-based advanced oxidation processes (AOPs) combined biological system was a promising technology for treating antibiotic wastewater. However, how pretreatment influence antibiotic resistance genes (ARGs) propagation remains largely elusive, especially the produced by-products (antibiotic residues and sulfate) are often ignored. Herein, we investigated the effects of zero valent iron/persulfate pretreatment on ARGs in bioreactors treating sulfadiazine wastewater. Results showed absolute and relative abundance of ARGs reduced by 59.8%- 81.9% and 9.1%- 52.9% after pretreatments. The effect of 90-min pretreatment was better than that of the 30-min. The ARGs reduction was due to decreased antibiotic residues and stimulated sulfate assimilation. Reduced antibiotic residues was a major factor in ARGs attenuation, which could suppress oxidative stress, inhibit mobile genetic elements emergence and resistant strains proliferation. The presence of sulfate in influent supplemented microbial sulfur sources and facilitated the in-situ synthesis of antioxidant cysteine through sulfate assimilation, which drove ARGs attenuation by alleviating oxidative stress. This is the first detailed analysis about the regulatory mechanism of how sulfate radical-based AOPs mediate in ARGs attenuation, which is expected to provide theoretical basis for solving concerns about by-products and developing practical methods to hinder ARGs propagation.

Insight into Chinese medicine residue biochar combined with ultrasound for persulfate activation in atrazine degradation: Acanthopanax senticosus precursors, synergistic effects and toxicity assessment.

The synergistic activation of persulfate by multiple factors could degrade pollutants more efficiently. However, the co-activation method based on metal ions has the risk of leakage. The non-metallic coupling method could achieve the same efficiency as the metal activation and meanwhile release environmental stress. In this study, the original biochar (BC) was prepared through using Chinese medicinal residue of Acanthopanax senticosus as the precursor. Compared with other biochar, the pore size structure was higher and toxicity risk was lower. The ultrasonic (US)/Acanthopanax senticosus biochar (ASBC)/persulfate oxidation system was established for Atrazine (ATZ). Results showed that 45KHz in middle and low frequency band cooperated with ASBC600 to degrade nearly 70 % of ATZ within 50 min, and US promoted the formation of SO4- and OH. Meanwhile, the synergy index of US and ASBC was calculated to be 1.18, which showed positive synergistic effect. Finally, the potential toxicity was examined by using Toxicity Characteristic Leaching Procedure (TCLP) and luminescent bacteria. This study provides a promising way for the activation of persulfate, which is expected to bring a new idea for the win-win situation of pollutant degradation and solid waste resource utilization.

The Feasibility of Maintaining Biological Phosphorus Removal in A-Stage via the Short Sludge Retention Time Approach: System Performance, Functional Genus Abundance, and Methanogenic Potential.

The increasing concerns on resource and energy recovery call for the modification of the current wastewater treatment strategy. This study synthetically evaluates the feasibility of the short sludge retention time approach to improve the energy recovery potential, but keeping steady biological phosphorus removal and system stability simultaneously. SBRS-SRT and SBRcontrol that simulated the short sludge retention time and conventional biological phosphorus removal processes, respectively, were set up to treat real domestic sewage for 120 d. SBRS-SRT achieved an efficient COD (91.5 ± 3.5%), PO43--P (95.4 ± 3.8%), and TP (93.5 ± 3.7%) removal and maintained the settling volume index around 50 mL/gSS when the sludge retention time was 3 d, indicating steady operational stability. The poor ammonia removal performance (15.7 ± 7.7%) and a few sequences detected in samples collected in SBRS-SRT indicated the washout of nitrifiers. The dominant phosphorus accumulating organisms Tetrasphaera and Hydrogenophaga, which were enriched with the shortened sludge retention time, was in line with the excellent phosphorus performance of SBRS-SRT. The calculated methanogenic efficiency of SBRS-SRT increased significantly, which was in line with the higher sludge yield. This study proved that the short sludge retention time is a promising and practical approach to integrate biological phosphorus removal in A-stage when re-engineering a biological nutrient removal process.

Upgrading liquor-making wastewater into medium chain fatty acid: Insights into co-electron donors, key microflora, and energy harvest.

Ethanol and lactate are considered suitable electron donors (EDs) for chain elongation (CE); however, their respective shortcomings still limit the substrate conversion ratio and medium chain fatty acid (MCFA) production. To address this limitation, different EDs and electron acceptors (EAs) were combined to compare their CE performances, and to investigate whether the combination of ethanol and lactate could further enhance the MCFA production based on the complementary characteristics of ethanol and lactate. The results verified, for the first time, ethanol and lactate as the co-EDs formed a cooperative relationship to largely promote the conversion of substrates into MCFA. The co-EDs of ethanol and lactate stimulated the transformation of dispersive lactate-carbon flux from the competing acrylate pathway into n-heptylate. Additionally, the coexisting by-products (H2 and CO2) from ethanol and lactate also contributed to the supererogatory MCFA generation. The key microbial taxa that distinguished the co-EDs from their single action were the preponderant species from class Negativicutes and family Ruminococcaceae. In addition, the co-EAs of acetate, n-butyrate, and n-caproate also promoted MCFA generation. Low concentration of n-caproate could be directly elongated into n-caprylate, while n-caproate concentration exceeding the toxic limit was unsuitable as an EA. This research provided a guide for substrate selection and collocation for CE technology. Chinese liquor-making wastewater (CLMW) was subsequently used as a substrate for MCFA production since it contains abundant lactate, ethanol, and short-chain fatty acids. In this study, a MCFA selectivity of 80.34 ±â€¯5.26%, a slightly higher selectivity which is in the range of previously reported ones, was obtained. This study paves a way for the sustainable development of Chinese liquor industry by recycling the high-output CLMW into MCFA.

Biological phosphorus removal in an extended ASM2 model: Roles of extracellular polymeric substances and kinetic modeling.

This paper presents the results of an extended ASM2 model for the modeling and calibration of the role of extracellular polymeric substances (EPS) in phosphorus (P) removal in an anaerobic-aerobic process. In this extended ASM2 model, two new components, the bound EPS (XEPS) and the soluble EPS (SEPS), are introduced. Compared with the ASM2, 7.71, 8.53, and 9.28% decreases in polyphosphate (polyP) were observed in the extended ASM2 in three sequencing batch reactors feeding with different COD/P ratios, indicating that 7.71-9.28% of P in the liquid was adsorbed by EPS. Sensitive analysis indicated that, five parameters were the significant influential parameters and had been chosen for further model calibration by using the least square method to simulate by MATLAB. This extended ASM2 has been successfully established to simulate the output variables and provides a useful reference for the mathematic simulations of the role of EPS in biological phosphorus removal process.

Enhancement of volatile fatty acid production by co-fermentation of food waste and excess sludge without pH control: The mechanism and microbial community analyses.

The study provided a cost-effective and high-efficiency volatile fatty acid (VFA) production strategy by co-fermentation of food waste (FW) and excess sludge (ES) without artificial pH control. VFA production of 867.42mg COD/g-VS was obtained under the optimized condition: FW/ES 5, solid retention time 7d, organic loading rate 9g VS/L-d and temperature 40°C. Mechanism exploration revealed that the holistic biodegradability of substrate was greatly enhanced, and proper pH range (5.2-6.4) was formed by the high buffering capacity of the co-fermentation system itself, which effectively enhanced hydrolysis yield (63.04%) and acidification yield (83.46%) and inhibited methanogenesis. Moreover, microbial community analysis manifested that co-fermentation raised the relative abundances of hydrolytic and acidogenic bacteria including Clostridium, Sporanaerobacter, Tissierella and Bacillus, but suppressed the methanogen Anaerolineae, which also facilitated high VFA production. These results were of great guiding significance aiming for VFA recovery from FW and ES in large-scale.

Simultaneous in-situ sludge reduction and nutrient removal in an A(2)MO-M system: Performances, mechanisms, and modeling with an extended ASM2d model.

Among the existing in-situ sludge reduction processes, the oxic-settling-anaerobic (OSA) process is of particular interest because it has shown significant sludge reduction with several advantages. However, an ideal process for practical application must simultaneously incorporate effluent quality with sludge reduction. In this study, an improved OSA system, the stage-aerated anaerobic, anoxic, micro-aerobic, and oxic system combining a micro-aerobic starvation tank (abbreviated as A(2)MO-M system) was developed. Compared with OSA3# (hydraulic retention time (HRT) of 12 h), the A(2)MO-M2# system with optimized HRT of 9 h yielded almost 16.3% less sludge. The average total nitrogen (87.3%) and total phosphorus (91.9%) removal efficiencies in A(2)MO-M2# were 20.6 and 42.2% higher than those in OSA3#. Investigation of the mechanisms of sludge reduction revealed that, except for the main factors of energy uncoupling metabolism (16.7%) and sludge decay (21.2%), enrichment of slow-growing bacteria and lysis-cryptic growth metabolism analyzed by high-throughput 454 pyrosequencing were shown to contribute to sludge reduction in the A(2)MO-M system. On the basis of effluent organic matters (EfOM) measurements, soluble microbial products (SMP) were the major components in EfOM; and different reduction-oxidation (redox) potentials controlled in the OSA and A(2)MO-M systems led to different SMP formation mechanisms. To explore the mechanism and kinetics of SMP formation under different redox potentials, three new components (SUAP, SBAP, and XEPS) were integrated in an extended ASM2d model. Experimental and modeling results revealed that biomass-associated products (BAP) supported a substantial population of SMP that were quite sensitive to different redox potentials. The extended ASM2d model further illustrated that more BAP produced in the alternating anaerobic and aerobic conditions in the OSA system adversely affected its effluent quality.

Economical evaluation of sludge reduction and characterization of effluent organic matter in an alternating aeration activated sludge system combining ozone/ultrasound pretreatment.

An ozone/ultrasound lysis-cryptic growth technology combining a continuous flow anaerobic-anoxic-microaerobic-aerobic (AAMA+O3/US) system was investigated. Techno-economic evaluation and sludge lyses return ratio (r) optimization of this AAMA+O3/US system were systematically and comprehensively discussed. Economic assessment demonstrated that this AAMA+O3/US system with r of 30% (AAMA+O3/US2# system) was more economically feasible that can give a 14.04% saving of costs. In addition to economic benefits, a 55.08% reduction in sludge production, and respective 21.17% and 5.45% increases in TN and TP removal efficiencies were observed in this AAMA+O3/US2# system. Considering the process performances and economic benefits, r of 30% in AAMA+O3/US2# system was recommended. Excitation-emission matrix and Fourier transform infrared spectra analyses also proved that less refractory soluble microbial products were generated from AAMA+O3/US2# system. Improvement in 2,3,5-triphenyltetrazolium chloride electron transport system (TTC-ETS) activity in AAMA+O3/US2# further indicated that a lower sludge lyses return ratio stimulated the microbial activity.

Feasibility and simulation model of a pilot scale membrane bioreactor for wastewater treatment and reuse from Chinese traditional medicine.

The lack and pollution of water resource make wastewater reuse necessary. The pilot scale long-term tests for submerged membrane bioreactor were conducted to treat the effluents of anaerobic or aerobic treatment process for the high-strength Chinese traditional medicine wastewater. This article was focused on the feasibility of the wastewater treatment and reuse at shorter hydraulic retention time (HRT) of 5.0, 3.2 and 2.13 h. MLSS growth, membrane flux, vacuum values and chemical cleaning periods were also investigated. The experimental results of treating two-phase anaerobic treatment effluent demonstrated that the CODfilt was less than 100 mg/L when the influent COD was between 500-10000 mg/L at HRT of 5.0 h, which could satisfy the normal discharged standard in China. The experimental results to treat cross flow aerobic reactor effluent demonstrated that the average value of CODfilt was 17.28 mg/L when the average value of influent COD was 192.84 mg/L at HRT of 2.13 h during 106 d, which could completely meet the normal standard for water reuse. The maximum MLSS and MLVSS reached 24000 and 14500 mg/L at HRT of 3.2 h respectively. Membrane flux had maximal resume degrees of 94.7% at vacuum value of 0.02 MPa after cleaning. Chemical cleaning periods of membrane module were 150 d. A simulation model of operational parameters was also established based on the theory of back propagation neural network and linear regression of traditional mathematical model. The simulation model showed that the optimum operational parameters were suggested as follows: HRT was 5.0 h, SRT was 100 d, the range of COD loading rate was between 10.664-20.451 kg/(m3xd), the range of MLSS was between 7543-13694 mg/L.