Phosphorus flows and use efficiencies in production and consumption of wheat, rice, and maize in China

Increasing fertilizer phosphorus (P) application in agriculture has greatly contributed to the increase of crop yields during the last decades in China but it has also increased P flows in food production and consumption. The relationship between P use efficiency and P flow is not well quantified at national level. In present paper we report on P flows and P use efficiencies in rice, wheat, and maize production in China using the NUFER model. Conservation strategies for P utilization and the impact of these strategies on P use efficiency have been evaluated. Total amounts of P input to wheat, rice, and maize fields were 1095, 1240, and 1128 Gg, respectively, in China, approximately 80% of which was in chemical fertilizers. The accumulation of P annually in the fields of wheat, rice, and maize was 29.4, 13.6, and 21.3 kg ha⁻¹, respectively. Phosphorus recovered in the food products of wheat, rice, and maize accounted for only 12.5%, 13.5%, and 3.8% of the total P input, or 3.2%, 2.6%, and 0.9% of the applied fertilizer P, respectively. The present study shows that optimizing phosphorus flows and decreasing phosphorus losses in crop production and utilization through improved nutrient management must be considered as an important issue in the development of agriculture in China.     

Synthesis of core-shell magnetic molecular imprinted polymer by the surface RAFT polymerization for the fast and selective removal of endocrine disrupting chemicals from aqueous solutions

In this study, we present a general protocol for the making of surface-imprinted core-shell magnetic beads via reversible addition-fragmentation chain transfer (RAFT) polymerization using RAFT agent functionalized iron oxide nanoparticles as the chain transfer agent. The resulting composites were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) analysis, thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface-imprinted magnetic beads were demonstrated with a homogeneous polymer films (thickness of about 22 nm), spherical shape, and exhibited magnetic property (Ms = 0.41 mA m² g⁻¹) and thermal stability. Rebinding experiments were carried out to determine the specific binding capacity and selective recognition. The as-synthesized surface-imprinted core-shell magnetic beads showed outstanding affinity and selectivity towards bisphenol A over structurally related compounds, and easily reach the magnetic separation under an external magnetic field. In addition, the resulting composites reusability without obviously deterioration in performance was demonstrated at least five repeated cycles.     

The removal of Polycyclic Aromatic Hydrocarbons in the wastewater treatment process: experimental calculations and model predictions

The removal of PAHs during the wastewater treatment process was examined in an activated sludge mode conventional facility. Concentrations reported are taken from an earlier measuring campaign. Removals of PAHs ranged between 28 and 67% in the primary, <1-61% in the secondary stage, and 37-89% in the whole process. Significant positive relationships were observed for removal efficiencies and the log K(ow) of PAHs in the primary and the log K(H) of PAHs in the secondary stage. Experimental removals were compared to those obtained from the FATE model. In the primary stage, predicted removals were lower than those experimentally calculated while in the secondary stage were higher. Predicted removals were apportioned mainly to sorption with negligible contribution from volatilization and biodegradation. Remarkable consistency between experimental and modeled removal efficiencies (-20-+20%) was observed for almost all PAHs in the whole treatment process.     

Technological options for the management of biosolids

BACKGROUND, AIM, AND SCOPE: Large quantities of biosolids (sewage sludge), which are produced from municipal wastewater treatment, are ever-increasing because of the commissioning of new treatment plants and continuous upgrades of the existing facilities. A large proportion of biosolids are currently landfilled. With increasing pressure from regulators and the general public, landfilling of biosolids is being phased out in many countries because of potential secondary pollution caused by leachate and the emission of methane, a potent greenhouse gas. Biosolids contain nutrients and energy that can be used beneficially. Significant efforts have been made recently to develop new technologies to manage biosolids and make useful products from them. In this paper, we provide a review of the technologies in biosolids management. MATERIALS AND METHODS: A survey of literature was conducted. RESULTS: At present, the most common beneficial use of biosolids is agricultural land application because of inherent fertilizer values found in biosolids. Expansion of land application, however, may be limited in the future because of more stringent regulatory requirements and public concern about food chain contamination in some countries. Perceived as a green energy source, the combustion of biosolids has received renewed interest. Anaerobic digestion is generally a more effective method than incineration for energy recovery, and digested biosolids are suitable for further beneficial use through land application. Although conventional incineration systems for biosolid management generally consume more energy than they produce because of the high moisture content in the biosolids, it is expected that more combustion systems, either monocombustion or cocombustion, will be built to cope with the increasing quantity of biosolids. DISCUSSION: Under the increasingly popular low-carbon economy policy, biosolids may be recognized as a renewable fuel and be eligible for 'carbon credits'. Because ash can be used to manufacture construction materials, combustion can provide a complete management for biosolids. A number of advanced thermal conversion technologies (e.g., supercritical water oxidation process and pyrolysis) are under development for biosolids management with a goal to generate useful products, such as higher quality fuels and recovery of phosphorus. With an ever-increasing demand for renewable energy, growing bioenergy crops and forests using biosolids as a fertilizer and soil amendment can not only contribute to the low-carbon economy but also maximize the nutrient and carbon value of the biosolids. CONCLUSIONS: Land application of biosolids achieves a complete reuse of its nutrients and organic carbon at a relatively low cost. Therefore, land application should become a preferred management option where there is available land, the quality of biosolids meet regulatory requirements, and it is socially acceptable. Intensive energy cropping and forest production using biosolids can help us meet the ever-increasing demand for renewable energy, which can eliminate the contamination potential for food sources, a common social concern about land application of biosolids. In recent years, increasing numbers of national and local governments have adopted more stringent regulations toward biosolid management. Under such a political climate, biosolids producers will have to develop multireuse strategies for biosolids to avoid being caught because a single route management practice might be under pressure at a short notice. Conventional incineration systems for biosolids management generally consume more energy than they produce and, although by-products may be used in manufacturing, this process cannot be regarded as a beneficial use of biosolids. However, biosolids are likely to become a source of renewable energy and produce 'carbon credits' under the increasingly popular, low-carbon economy policy. RECOMMENDATIONS AND PERSPECTIVES: To manage biosolids in a sustainable manner, there is a need for further research in the following areas: achieving a higher degree of public understanding and acceptance for the beneficial use of biosolids, developing cost-efficient and effective thermal conversions for direct energy recovery from biosolids, advancing technology for phosphorus recovery, and selecting or breeding crops for efficient biofuel production.     

高效除磷材料的除磷特性研究

研究了高效除磷材料(Efficient Phosphorus Removal Composite,EPRC)的除磷特性,以及以此材料为填料的吸附柱对模拟含磷废水的除磷效果.试验结果表明: EPRC颗粒在15℃、25℃、35℃时的最大饱和吸附量分别达到1.9535mg/g、2.281mg/g、3.6724mg/g.以EPRC颗粒填充吸附柱处理模拟含磷废水时,停留时间8h、连续进水、运行8d,磷的平均去除率为93%,废水pH值略有升高.     

Degradation of chlorinated dioxin in denitrifying activated sludge from leachate treatment plant of a landfill

The degradation rate of dioxins added to the activated sludge from a leachate treatment plant of a landfill under denitrification conditions was estimated using six bioreactors. Over 99% of the added dioxins (600ng) were degraded within 7 days. Furthermore, continuous cultivation was carried out for 1 month. The activated sludge degraded 600ng of dioxins (that is, all of the added dioxins) placed in each reactor every 7 days, and this activity was maintained for 35 days. Under aerobic conditions with this sludge, the dioxins were not degraded in 7 days, but 90% of the 600ng of dioxins was degraded in 35 days. The high level of activity observed in the present study may only occur under anaerobic conditions, especially under denitrifying conditions.     

SH-A工艺处理煤焦油加工废水的研究

采用"SH-A节能型强化生物脱氮除碳工艺"进行煤焦油加工废水处理的研究,讨论了各个处理环节的运行情况和处理效果。经该工艺对煤焦油加工废水进行处理后,COD、NH-N和矿物油的去除率均可达到98%,色Cr 3度和酚的去除率均可达到99%,氰的去除率可达到95%,各项指标均可达到国家《污水综合排放标准》(GB8978-1996)一级。     

Phosphorus removal from sediments by Potamogeton crispus: New high-resolution in-situ evidence for rhizosphere assimilation and oxidization-induced retention

Macrophytes are usually chosen for phytoremediation tools to remove P in eutrophic aquatic ecosystems, but the lack of test methods hinders the understanding of removal mechanism and application. In this study, we used the novel technologies combined of Diffusive gradients in thin films (DGT), Planar optode (PO), and Non-invasive micro-test technology (NMT) to explore P dynamics in water-sediment continuum and rhizosphere of Potamogeton crispus over time. Results of the high-resolution in situ measurement showed that labile P(LP_DGT) fluxes at the surficial sediment significantly decreased from approximate 120, 140, and 200 pg/ (cm²?sec) via 30 days incubation period to 17, 40, and 56 pg/(cm²?sec) via that of 15 days. Obvious synchronous increase of LP_DGT was not detected in overlying water, suggesting the intense assimilation of dissolve reactive P via root over time. PO measurement indicated that O₂ concentration around the rhizosphere remarkably increased and radially diffused into deeper sediment until 100% saturation along with the root stretch downwards. NMT detection of roots showed the obvious O₂ inflow into root tissue with the uppermost flux of 30 pmol/(cm²?sec) from surroundings via aerenchyma on different treatment conditions. Different from previous reports, gradually saturating O₂ concentrations around the rhizosphere was principally driven by O₂ penetration through interspace attributing to root stretch downward rather than root O₂ leakage. Increased O₂ concentrations in deep sediment over time finally induced the oxidization of labile Fe(II) into Fe(III) bound P and local P immobilization.     

Enhanced biological phosphorus removal using thermal alkaline hydrolyzed municipal wastewater biosolids

This study reports the feasibility of using municipal wastewater biosolids as an alternative carbon source for biological phosphorus removal. The biosolids were treated by a lowtemperature, thermal alkaline hydrolysis process patented by Lystek International Inc.(Cambridge, ON, Canada) to produce short-chain volatile fatty acids and other readily biodegradable organics. Two sequencing batch reactors(SBRs) were operated with synthetic volatile fatty acids(Syn VFA) and readily biodegradable organics produced from the alkaline hydrolysis of municipal wastewater biosolids(Lystek) as the carbon source, respectively.Municipal wastewaters with different strengths and COD:N:P ratios were tested in the study. The reactors' performances were compared with respect to nitrogen and phosphorus removal. It was observed that phosphorus removal efficiencies were between 98%–99% and 90%–97% and nitrogen removal efficiencies were 78%–81%, and 67% for the Syn VFA and Lystek, respectively. However, the kinetics for phosphorus release and uptake during the anaerobic and aerobic stages with Lystek were observed to be significantly lower than Syn VFA due to the presence of higher order VFAs(C4 and above) and other fermentable organics in the Lystek.     

Underestimation of phosphorus fraction change in the supernatant after phosphorus adsorption onto iron oxides and iron oxide–natural organic matter complexes

The phosphorus(P) fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid(HA) complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L(I =0.01 mol/L and pH = 7),it was shown that the colloid(1 kDa-0.45 μm) component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite(FH),goethite(GE),ferrihydrite-humic acid complex(FH-HA),goethite-humic acid complex(GE-HA),respectively.The 1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe~(3+) hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.