Modelling N mineralization from green manure and farmyard manure from a laboratory incubation study

Predicting N mineralization from organic manures like farmyard manure (FYM) is more difficult than from fresh organic materials like crop residues, as the manures vary greatly in composition. A laboratory incubation experiment was carried out for 98 days at 30 °C under aerobic conditions to study the effects on N dynamics of Gliricidia (Gliricidia sepium, Jacquin) and FYM application to soil at 5 and 10 g kg⁻¹. Application of Gliricidia induced N mineralization from the start of incubation period, with the amount of N mineralized increasing with rate of application. In contrast, application of FYM resulted in immobilization of mineral N in soil, irrespective of the rate of application. The initial net immobilization from FYM was limited by availability of N in the soil for the higher rate of application.We used the APSIM SoilN module to simulate these contrasting patterns of mineralization of N from Gliricidia and from FYM. The prediction of N mineralized from Gliricidia was better than FYM. The default model parameters specify that the fresh organic matter pools (FPOOL1, FPOOL2 and FPOOL3) have the same C:N ratio and this assumption was ineffective in predicting N mineralized from FYM. The predictive ability of the model improved when this default assumption was modified based on the size of the individual pools (FPOOL1, FPOOL2 and FPOOL3), and the pool's C:N ratios. The modelling efficiency, a measure of goodness of fit between the simulated and observed data, improved markedly for the modified model. The discrepancy between the modelled and observed data was a tendency for the model to underestimate the rate of re-mineralization at the lower rate of application of FYM in the later part of incubation. Unfortunately the appropriate modification to the size and C:N ratios of the FPOOLs could not be determined on the basis of chemical analysis alone. Thus, a true predictive application of the model to a new FYM material is not yet possible.     

磷基材料对土壤铅稳定化效果及影响因素的Meta分析

磷基材料对土壤Pb有良好的稳定化效果.利用Meta分析法筛选汇总了1997~2022年磷基材料稳定土壤Pb的90篇文献,从土壤性质、稳定化工艺条件和磷基材料类型这3个方面量化分析了磷基材料对土壤Pb的稳定化率、赋存形态转化和对土壤pH的影响.结果表明,从土壤性质来看,土壤碱性越强（pH≥7.5）、土壤ω（Pb）越低（≤500 mg ·kg^-1）和土壤ω（有机质）越高（>0.5%）时,越有利于磷基材料对土壤Pb的稳定化,稳定化率分别为75.21%、34.97%和93.12%.从稳定化工艺条件来看,磷基材料添加量较高（≥10%）、含水率较高（>50%）、养护时间较长（≥30d）和养护温度较高（≥40℃）时,更有利于土壤Pb的稳定化,稳定化率可分别达到80.65%、84.98%、79.39%和41.44%.从磷基材料类型来看,可溶性磷基材料对土壤Pb有很高稳定化率（96.24%）;其使土壤可交换态Pb和碳酸盐结合态Pb向残渣态Pb转化的转化率达到95.93%;可溶性磷基材料多呈酸性,对土壤pH的降低率为7.27%,难溶性磷基材料多呈碱性,对土壤pH的增加率为3.63%.综上,在土壤pH≥7.5、土壤ω（Pb）≤500 mg ·kg^-1、土壤ω（有机质）>0.5%、可溶性磷基材料添加量≥10%、含水率>50%、养护时间≥30 d和养护温度≥40℃时,磷基材料对土壤Pb的稳定化效果较好.可见在实际Pb污染土壤修复过程中,为提高Pb稳定化率,需综合考虑土壤性质、稳定化工艺条件和磷基材料类型等因素的影响.     

固定化硝化菌去除氨氮的研究

选用氯乙烯醇作为包埋载体,添加适量粉末活性炭,包埋固定硝化污泥,处理以（ＮＨ４）２ＳＯ４和葡萄糖为主的合成废水,考察了影响固定化工艺及硝化作用的各种因素。对固定化硝化菌的呼吸活性,细菌活性回收率等生物特性进行了测定。     

聚乙烯醇包埋厌氧活性污泥处理废水的最优化条件研究

研究以聚乙醇为主要包埋材料的混合载体法固定厌氧活性污泥处理有机废水的最优化条件。混合载体由聚乙烯醇（ＰＶＡ）、０．１５％海藻酸钠,２％Ｆｅ粉,０．３％ＣａＣＯ３,４％ＳｉＯ２粉末组成,结果表明,ＰＶＡ８％,初始污泥浓度１５％时最适宜,凝固凝饱和硼ＰＨ对包埋效果有影响,用Ｎａ２ＣＯ３调节硼酸ＰＨ至６．７可使包埋颗粒强度及产ＣＨ４活性提高,混合载体法有效地解决了固定化细胞技术应用于废水处理所面临的成球     

固定化微藻流化床反应器去除低碳污水中氨氮的潜力

以固定化微藻颗粒为原料,通过搭建流化床反应器强化微藻对氨氮（NH₄⁺-N）的去除,设计了藻种、污水上升流速、光周期和光照强度四组单一变量实验,系统地研究了不同条件下微藻去除NH₄⁺-N的能力.结果表明,当以固定化斜生栅藻为原料、污水上升流速为6.8m/h、光周期为8：16h和光照强度为4800Lux时,NH₄⁺-N去除效果最优（96.7%）.在最优操作条件下,探究了COD为200mg/L时微藻去除NH₄⁺-N的潜力,结果表明,当NH₄⁺-N初始浓度不高于50mg/L时,NH₄⁺-N去除率高于95%.本实验建立了一套半连续微藻流化床实验方法,该方法显著减弱了微藻在生物同化过程中对有机碳源的依赖性,为低COD条件下微藻生物脱氮工艺的设计提供了技术参考和理论基础.     

纳米Al_2O_3固定化红平红球菌菌球的制备及其对苯酚的降解

以海藻酸铝为主要包埋材料、纳米Al_2O_3为添加剂,包埋固定红平红球菌,制得纳米Al_2O_3固定化红平红球菌菌球,并将其用于苯酚的降解。表征结果显示:菌球内部包含丰富的菌丝体;内部孔径以中孔居多。实验结果表明:菌球的最优制备方案为0.05 g纳米Al_2O_3加入3 m L海藻酸钠溶液中、海藻酸钠质量分数6%、微生物包埋量0.5 m L/m L(以海藻酸钠溶液计)、Al_2(SO_4)_3质量分数3%;在初始苯酚质量浓度为400 mg/L、反应时间为24h、菌球加入量为8 g/L、反应p H为8.0、反应温度为30℃的条件下,菌球首次使用时可使苯酚完全降解,使用5次后的苯酚降解率仍达93%以上,具有良好的循环使用性。     

NITROGEN TRANSFORMATIONS IN SEDIMENTS AS AFFECTED BY CHEMICAL AMENDMENTS1

ABSTRACT: A study was conducted to elucidate some of the chemical factors affecting the rate and pathways of N transformations in lake sediments. The main emphasis was placed on modifying a noncalcareous sediment with CaCO₃ to approximate the composition of a calcareous sediment. Additionally, the effects of Ca²⁺, CO₃^2-, Mg2⁺ and OH^- were evaluated by using appropriate chemicals. Further, the effect of aluminum sulfate was evaluated with both sediment types. Sediment pH at 7 days was not affected by CaCO₃, but was decreased by aluminum sulfate. The CaCO₃ treatment increased the rate of ammonification, nitrification, reduction of acetylene to ethylene and methane formation, while with few exceptions the other treatments decreased the rate of the transformations studied. Aluminum sulfate, which has been proposed as a lake restoration treatment, increased ammonification but decreased most of the other transformations.     

微生物固定化技术在污水生物脱氮中的应用

综述了微生物固定化技术在污水硝化、生物脱氮中的应用,包括固定化材料与固定化工艺;国内外研究与应用现状;以及在较大规模污水处理中的实际应用;对该项技术目前存在的问题及其解决途径、发展前景和趋势进行了评述。     

Time dependent influx and efflux of phenol by immobilized microbial consortium

Phenol, like many other organic solvents, is toxic to micro-organisms even at low concentrations. However, some micro-organisms can withstand this toxicity to a certain concentration. To observe the uptake mechanism of phenol, bacteria were isolatedfrom a petroleum refinery effluent and identified. Study was carried out to understand the effect of varying sub-lethal concentrations of phenol, on all the isolated individual bacterial cultures. Out of the bacteria isolated, Serratia liquefaciens was found to tolerate phenol concentration up to 1500 mg l^-1. A microbial consortium of the isolated bacteriawas formulated and immobilized. Individual cultures were also immobilized and uptake of phenol by the immobilized micro-organisms was observed in a nutrient-rich and nutrient-stressed medium containing phenol as a sole source of carbon. A time-dependent uptake of phenol was exhibited by the micro-organismsin nutrient-stressed medium, after which a sudden increase in phenol concentration occurred in the extracellular medium, till it reached back to the initial concentration. This was attributedto an active efflux mechanism adopted by the micro-organisms to withstand the toxic shock.     

活性污泥的固定化及其性能研究

用改进聚乙烯醇-硼酸法将活性污泥制成固定化颗粒，考察了改进聚乙烯醇-硼酸法的最佳条件及固定化颗粒的性能。实验结果表明：改进聚乙烯醇-硼酸法的最佳条件为聚乙烯醇质量分数6．5％、包泥比（包埋剂与活性污泥质量比）1．2：1、二氧化硅质量分数1．5％、活性炭质量分数0．3％、海藻酸钠质量分数0．6％；用最佳条件下制得的固定化颗粒处理模拟化工废水，连续运行15d后的COD去除率达90％以上，且固定化颗粒耐冲击负荷和pH变化能力强；固定化颗粒对模拟化工废水的COD去除速率随进水COD的变化曲线类似于米氏方程所描述的反应初速度随底物浓度的变化规律。