Heterogeneity of humic/fulvic acids derived from composts explains the differences in accelerating soil Cd-hyperaccumulation by Sedum alfredii.

The hyperaccumulating mechanism concerning heavy metal activation or passivation and plant response triggered by fulvic acid (FA) and humic acid (HA) recruitments are investigated herein. We carefully examine the Cd activation effect by various FA and HA, tracing from pig, goat, and duck manure composts to straw compost and commercial materials (i.e., PC, GC, DC, SC, and CM), as well as their roles in plant growth promotion and Cd uptake. Our results indicate that due to the decrease of soil pH and their multiple functional groups, the contents of available Cd (AE-Cd) increased by 4.3-4.8% and 3.6-6.3% when all FA and HA sources were applied for 30 days. A 13.1-19.9% increase in AE-Cd was observed when CFA, DFA, and PFA were applied for five days, and a 9.5% increment was found when PHA was applied for 10 days. In the pot experiment, the Cd accumulation in plants increased by 2.78 and 2.17 folds with PFA and PHA applications, respectively, compared to the blank control group. This result can be attributed to the stimulative effects of the simultaneous Sedum alfredii growth and Cd phytoavailability. Notably, the Cd accumulation increased by 2.26 times with the SFA amendment due to the predominant stimulation effect to the phytoavailable Cd rather than plant growth. However, slight inhibitory effects were observed upon plant growth or Cd uptake, which led to the reduction of the Cd accumulation with DHA, SHA, and CHA employments. Consistently, the corresponding soil Cd removal efficiencies were 43.5% and 34.6% with PFA and PHA, respectively, which hold abundant O- and N-containing groups. Our research aims to gain insights into the ternary interaction in the presence of heavy metal, humic substances, and S. alfredii to simultaneously accelerate Cd activation and hyperaccumulation.

Phosphorus attenuation and mobilization in sand filters treating onsite wastewater.

The effectiveness of phosphorus (P) removal by sand filters is limited during septic tank effluent (STE) treatment. The elevated effluent P concentrations pose threats to drinking water quality and contribute to eutrophication. The concern of P leaching from sand filters is further exacerbated by the increased frequency of flooding and natural precipitation due to climate change. This study aimed to understand P attenuation and leaching dynamics, as well as the removal mechanisms in sand filters treating STE, offering insights into the design and implementation of P removal/recovery modules to onsite wastewater treatment systems. P attenuation and leaching during STE treatment and rainfall were studied in bench-scale columns (new vs. aged sand). At standard STE loading (1.2 gallon d-1 ft-2), 24-32% removal of total phosphorus (TP) was achieved, while increased P removal efficiency (35-53%) was observed at low loading (0.6 gallon d-1 ft-2) with influent containing 10.3-20.0 mg P L-1. Complete breakthroughs were observed in both aged (12-70 days) and new columns (27-73 days) at test hydraulic loadings. The maximum TP attenuation level was 20.6-45.3 mg P kg-1 and 25.3-33.0 mg P kg-1, in aged and new sand columns, respectively. When simulated rain was applied (15-60 mm h-1), 80-97% of the attenuated P leached out and the leaching dynamics were impacted by rainfall duration rather than the intensity. The highest concentrations of TP (15.6-15.9 mg L-1) were leached out from both columns within the first 2-6 h. Orthophosphate was the dominant P species in treated effluent (83-84%) and leachate (69-88%), demonstrating its significance as the major P form in the discharge. In addition, aged sand (>5 years) accumulated higher levels of Mg, Al, Ca, and Fe, thus enhancing the P attenuation level during STE treatment. Collectively, this study underscored the importance of frequent field monitoring for reliable long-term P removal estimates.

An old story with new insights into an ignored issue of metabolites in biochar-amended soil: Effect of biochar on dissipation of carbosulfan as an example.

Carbofuran (CAS) is one of extensively used carbamate pesticides, which is considered as a derivative or a candidate of carbofuran (CAN) for its lower toxicity and persistence. Nevertheless, CAS could be degraded into its toxic metabolites, imposing potential risks on ecological safety. In this paper, biochars, derived from rice straw (RS), chicken manure (CM), corn straw (CS) and tire rubber (TR), were applied in CAS-contaminated soil to explore their effects on the dissipation of CAS and its metabolites. The dissipation rate of CAS was depressed by the amendment of biochar, mainly because biochar inhibited the hydrolysis of CAS by elevating soil pH value. Nevertheless, CS has efficiently enhanced the dissipation of CAN by almost 2-times for its promotion in hydrolysis and biodegradation. CS and CM improved biodegradation by altering the composition and structure of the microbial communities, exhibiting potential for facilitating bioremediation of CAS and CAN. Moreover, steam activated biochar accelerated the dissipation rate by 1.7-2.9 times and 1.3-2.4 times for CAS and CAN, respectively. This study investigated the effects of biochar on CAS and its toxic metabolites as well as possible governing mechanisms, providing rational instruction for biochar application in ambient atmosphere.

Nutrient removal from piggery wastewater by Desmodesmus sp.CHX1 and its cultivation conditions optimization.

Combination of microalgae cultivation and piggery wastewater treatment has become a hot topic in recent years. Nutrient removal from aerated piggery wastewater (APW) by Desmodesmus sp. CHX1 and the optimization of cultivation conditions were investigated in this study. Results indicated that Desmodesmus sp. CHX1 showed an efficient growth in APW, with specific growth rate of 0.26-0.56 d-1. The biomass yield based on nutrient consumption was 9.65 g biomass/g NH4-N and 209.15 g biomass/g total phosphorus (TP) respectively. Desmodesmus sp. CHX1 performed well in nutrient removal from APW, with ammonium nitrogen (NH4-N) and TP removal efficiency (RE) of 78.46% and 91.66% respectively after 7 days of culture. Nutrient removal process fitted the pseudo-first-order kinetic equations well, with removal rate (RR) constant of 0.24 d-1 for NH4-N and 0.28 d-1 for TP. The optimum conditions for nutrient removal from APW by Desmodesmus sp. CHX1 were light intensity of 150 µmol photons m-2 s-1 in the photoperiod for 24 h when the temperature was set at 35°C with alga cell inoculation concentration of 30%. The removal efficiencies of NH4-N and TP were 88.26% and 95.06% respectively under the optimal conditions after 7 days of culture. Our results can be a good reference for enhancement of microalga production and the nutrient RE and further extend the application of the large-scale piggery wastewater treatment under a controlled environment.

Performance of a novel photobioreactor for nutrient removal from piggery biogas slurry: Operation parameters, microbial diversity and nutrient recovery potential.

Photobioreactor is deemed to be one of limiting factors for the commercial application of wastewater treatment based on microalgae cultivation. In this study, a novel Flat-Plate Continuous Open Photobioreactor (FPCO-PBR) was developed to treat piggery biogas slurry. The operation parameters, microbial stability and nutrient recovery potential of FPCO-PBR were investigated. Results showed that the appropriate influent mode for FPCO-PBR was multi-point or spraying mode. The optimal hydraulic retention time and interval time for biomass harvesting of FPCO-PBR were both 2 d. Nitrogen and phosphorus recovery rate were 30 mg L-1 d-1 and 7 mg L-1 d-1 respectively under optimal operating parameters. Microbial diversity remained relatively stable in FPCO-PBR. Biomass production rate of FPCO-PBR was 0.47 g L-1 d-1 under optimal operating parameters. The revenue generated from biomass was estimated to be 15.06 $ kg-1, which means that treating one ton of wastewater can generate $ 7.08 in revenue.

A scintillating plastic fiber array and multiplexer based 384-channel fast neutron spectrometer.

A fast neutron detection system based on a scintillating plastic fiber array and multiplexer was designed to measure the spectrum of fast neutrons ranged 10 MeV-100 MeV. With the method of nuclear recoil, the energy of incident neutron was determined by measuring the recoil proton track and deposited energy in scintillating plastic fibers. The detection system was composed of a scintillating plastic fiber array, 6 position sensitive photomultiplier tubes, and a high-density readout electronics based on the multiplexer. The scintillating plastic fiber array was made as a staggered structure with two kinds of fibers in different sizes (0.5 mm-square fiber and 3 mm-square fiber). The structure provided a wider detection energy range and better detection efficiency than arrays made with uniform plastic fibers. A dedicated digital electronics system was well designed to control the whole readout system to provide 384-channel signal processing. The detector had a 48 mm × 48 mm effective detection area and a mechanical size of 34 cm × 34 cm × 27 cm. In the simulation of the detector model performance, the system gave an energy resolution of 23%-35% for neutrons ranged 10 MeV-100 MeV. Experimental results showed that the detector had a good energy linearity and energy resolutions were, respectively, 35.82% at 14.817 MeV, 36.84% at 21.264 MeV, 35.90% at 23.069 MeV, and 32.90% at 24.220 MeV. The optimized prototype model had potential in increasing fast neutron detection performance.