Aerobic composting was conducted to evaluate the effects of the different ratios (0%, 2.5%, 5%, 7.5%, and 10%) of Ca-bentonite (CB) on the speciation of Cu and Zn during pig manure composting, while pot experiment was performed to investigate the role of CB-added compost on the bio-availability of Cu and Zn to Chinese cabbage and its biomass. The results showed that the exchangeable fractions of Cu and Zn decreased, while their oxidized and residual fractions gradually increased during composting; CB addition reduced the distribution ratios of bio-available Cu and Zn in mature compost by approximately 19.84%-48.90% and 4.94%-16.39%, compared to those in the 0% CB-added treatment, and the best result was found in the 10% CB-added treatment.. Meanwhile, the pot experiment confirmed that the addition of compost considerably increased soil organic matter (OM) and electrical conductivity (EC) but decreased soil pH value. On the contrary, the application of CB effectively decreased EC and increased soil pH but inhibited OM mineralization in soil as compared to non-amended treatment. While addition of compost significantly increased plant dry biomass as compared to that with soil alone, maximum biomass was obtained[(6.51±0.34) g·pot-1] in 10% CB-added compost. After the application of CB-added compost, the contents of the bio-available factions of Cu in the harvested soil increased, while the contents of the exchangeable fractions of Zn decreased by 38.91%, 43.69%, 46.02%, 45.12%, and 54.65%, respectively. The absorption of Cu and Zn by Chinese cabbage was considerably reduced after the application of compost, while the uptake of Zn in the plant declined as the CB rates increased, and the absorption of Cu increased. The study indicated that 10% CB addition could significantly reduce the bioavailability of Cu and Zn in compost, and also showed a continuous effect on restricting the bioavailability of Zn after land utilization. Meanwhile CB amendment enhanced Chinese cabbage biomass and reduced the uptake of Zn.
Sewage sludge was amended with calcium-based bentonite with addition of no more than 10% in dry weight during the 52-day aerobic composting process, the variations of temperature, pH, organic carbon, EC, total nitrogen, nitrate(NH4+-N) and ammonium(NO3--N) were investigated, as well as the compost detoxification(germination test), heavy metals(Zn, Cu, Pb, Cd) passivation and estrone(E1) elimination. The results showed that the amendment facilitated the thermophilic phase, promoted the compost heat inactivation and brought the organic carbon mineral up to more than 15.27% -19.71%. During the composting, the compost pH increased at the beginning and then gradually decreased before reaching values of 6.76-7.05, while the amendments alleviated the dramatic pH value fluctuation. The bentonite amendment reduced the salinity of the compost with final product EC remarkably lower than 1132 μS·cm-1 of the control treatment, and the effect was enhanced with the increase of addition amount. The total nitrogen content increased with time, and there was a remarkable ammonia loss in the beginning stage for the control treatment, while the bentonite addition could facilitate the total nitrogen content increase by reducing the ammonia loss. With the composting variation, the contents of NH4+-N increased and then decreased while the NO3--N content increased gradually. The bentonite addition had a slight inhibitory effect on the plant germination but did not influence the compost maturity and detoxification; meanwhile, the amendment improved the heavy metal passivation and reduced the E1 content, especially from 90.48 to 28.27 μg·kg-1 with 5% treatment during the composting. The study indicated that bentonite addition of lower than 5% was acceptable for the sludge compost amendment, which had great potential in sludge hygienization, detoxification, heavy metal passivation and E1 elimination.
Abstract In this work, a detection method using pH and ORP for the endpoint determination of the prepared reaction of N-(oxidiethylene)-2-benzothiazolyl sulfonamide (NOBS) was reported, and the properties of NOBS samples were comprehensively investigated. According to the chemical equation of this reaction, the turning point of pH and ORP was used to determine the endpoint of this reaction. Results showed that the purity and yield of experimental NOBS samples increased to 96.4% and 81.7%, respectively. The FTIR and XRD analysis were also used to investigate the chemical structure and crystal absorption peak of NOBS samples. SEM-EDS spectra confirmed the existence of C, N, O and S elements, and there were no other elements in the products. What is more important, the properties of experimental NOBS samples were better than that of contrast samples. Thus, this paper offers an approach to determine the endpoint of the prepared reaction of NOBS.
The effect of initial total solids (TS) concentration on volatile fatty acid (VFAs) production from food waste under mesophilic conditions (35 °C) was determined. VFAs concentration and composition, biogas production, soluble chemical oxygen demand concentration, TS and volatile solids (VS) reduction, and ammonia nitrogen release were investigated. The VFAs concentrations were 26.10, 39.68, 59.58, and 62.64 g COD/L at TS contents of 40, 70, 100, and 130 g/L, respectively. While the VFAs’ yields ranged from 0.467 to 0.799 g COD/g VSfed, decreased as initial TS increased. The percentage of propionate was not affected by TS concentration, accounting for 30.19–34.86% of the total VFAs, while a higher percentage of butyrate and lower percentage of acetate was achieved at a higher TS concentration. Biogas included mainly hydrogen and carbon dioxide and the maximum hydrogen yield of 148.9 ml/g VSfed was obtained at 130 g TS/L. concentration, TS and VS reductions increased as initial TS increased. Considering the above variables, we conclude that initial TS of 100 g/L shall be the most appropriate to VFAs production.
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