Optimization of process parameters using response surface methodology for bioconversion of activated sludge by Penicillium corylophilum

The optimization of process parameters for the bioconversion of activated sludge by Penicillium corylophilum was investigated using response surface methodology （RSM）. The three parameters namely temperature of 33℃, agitation of 150 r/min, and pH of 5 were chosen as center point from the previous study of fungal treatment. The experimental data on chemical oxygen demand （COD） removal （%） were fitted into a quadratic polynomial model using multiple regression analysis. The optimum process conditions were determined by analyzing response surface three-dimensional surface plot and contour plot and by solving the regression model equation with Design Expert software. Box-Behnken design technique under RSM was used to optimize their interactions, which showed that an incubation temperature of 32.5℃, agitation of 105 r/min, and pH of 5.5 were the best conditions. Under these conditions, the maximum predicted yield of COD removal was 98.43%. These optimum conditions were used to evaluate the trail experiment, and the maximum yield of COD removal was recorded as 98.5%.     

太湖流域稻田不同氮肥管理模式下的氮素平衡特征及环境效应评价

研究了不同氮肥管理模式下的稻田氮素平衡特征和环境效应.在太湖主要入湖河流直湖港下游开展了农户常规施肥处理、缓控释肥处理、有机无机肥配施处理、按需施肥处理以及化肥减量优化处理5种氮肥管理模式的田间小区试验,实测了稻季的径流和淋洗氮损失,估算了氨挥发和N₂O等气体损失,分析了不同氮肥处理下的环境排放量和氮素平衡特征.与农户常规施肥处理相比,其他处理在减少氮肥总投入量20%～40%的情况下产量与农户对照基本持平,氮肥利用率提高了14.5%～44%.不同氮肥管理模式下,缓控释肥处理和按需施肥处理的氮环境排放量最低,比农户施肥处理分别降低了52.8%和45.4%.在等氮量投入下,有机无机配施处理比纯化肥处理减少了环境氮排放量.农户施肥处理存在着明显的氮盈余,增加了麦季氮流失的风险,按需施肥处理略微出现氮亏缺,在一定程度上减少了麦季氮流失风险.新型缓控释肥处理和按需施肥处理能在不降低产量和效益的情况下,提高氮肥利用率,减少环境排放量,是值得在太湖流域推广的经济环保氮肥管理模式.     

纳米级二氧化锰材料阻控土壤砷向水稻迁移的研究

为了探究纳米级二氧化锰材料阻控土壤中砷向水稻迁移的影响,通过盆栽种植水稻,向砷污染土壤中分别添加0%(CK)、0.2%、0.5%、1.0%和2.0%的纳米级二氧化锰材料,分析土壤溶液p H值、砷和锰的含量变化,及水稻中砷和锰的含量变化.结果表明:添加不同浓度的纳米级二氧化锰材料,土壤溶液pH值没有显著变化,土壤溶液中砷、锰的浓度随着水稻生长的时间增加而降低;不同时期水稻中砷和锰的分布规律是根部茎部叶部糙米,水稻植株中锰和砷的含量呈显著负相关(p0.05);不同浓度的纳米级二氧化锰材料能有效控制水稻糙米中总砷含量,其中1.0%添加量的阻控效果最好,使糙米中总砷含量降低了65.4%,其无机砷含量低于《食品中污染物限量(GB2762—2012)》中砷限量.     

外源钙对两种价态锑胁迫下水稻幼苗吸收积累锑和钙的影响

通过溶液培养试验,研究外源钙对两种价态锑[Sb(III)和Sb(Ⅴ)]胁迫下水稻吸收积累锑和钙的影响。结果表明,这两种价态的Sb对水稻生长均有抑制作用,Sb(III)比Sb(Ⅴ)对水稻毒害更明显,施Ca可缓解Sb对水稻的毒害。Sb(III)和Sb(Ⅴ)的添加对水稻根系和茎叶吸收积累Ca影响不一致。当溶液中的Ca浓度为5.0 mmol·L-1时,添加三价Sb 10和30μmol·L-1均可以显著地降低水稻茎叶中的Ca含量15.7%和49.4%,但是添加Sb(Ⅴ)浓度为30μmol·L-1时,却分别提高水稻茎叶和根系Ca含量26.2%和50.4%。Ca的添加可以显著地降低水稻根系和茎叶对两个价态Sb的吸收积累。在30μmol·L-1Sb(III)处理下,添加5.0和20 mmol·L-1的Ca可导致水稻根系和水稻茎叶Sb浓度分别比对照处理降低19.0%-79.4%和42.6%-71.8%;在30μmol·L-1Sb(Ⅴ)处理下,添加5.0和20 mmol·L-1的Ca可导致水稻根系和水稻茎叶Sb浓度分别比对照处理降低34.3%-70.6%和74.1%-84.6%。Ca的添加对Sb在水稻根系和茎叶中的富集系数和分配比率也有显著影响。综上所述,可以通过施用Ca肥来防治农田Sb污染,降低Sb对人体健康的危害。     

外源酶对秸秆堆肥进程的影响及腐熟度模糊评价

为探讨外源酶制剂对秸秆堆肥腐熟进程的影响,通过模拟堆肥试验研究了分别添加纤维素酶、蛋白酶,以及纤维素酶与蛋白酶混合添加情况下堆肥各项指标的动态变化规律,并利用模糊综合评价法对堆肥腐熟度进行了评价.结果表明,纤维素酶与蛋白酶配合使用对堆肥中纤维素的降解及氮素释放都有较强的促进效果,与对照处理相比,纤维素含量降低了14.9%,C/N降低了18.4%,发芽指数提高了6.0%;单施外源纤维素酶主要是促进了纤维素类物质降解速率,显著提高了发芽指数;单施外源蛋白酶则显著促进了含氮物质的分解,铵态氮及硝态氮含量提高;通过对E4/E6、NH+4-N、NO-3-N、C/N、发芽指数等指标进行模糊综合评价,得出纤维素酶与蛋白酶的配合使用对于促进堆肥腐熟效果最佳,其次是纤维素酶堆肥和蛋白酶堆肥,常规堆肥腐熟程度最低.可见,纤维素酶与蛋白酶配合使用对堆肥腐熟有更好的促进效果,可以推测外源纤维素酶和蛋白酶对于促进堆肥腐熟具有协同作用.     

Improving the Synthesis Gas Quality in Catalytic Gasification of Rice Straw by an Integrated Hot-Gas Cleaning System

This research investigates an enhanced removal rate of tar and trace pollutants (e.g. hydrogen chloride and hydrogen sulfide, H₂S) in the gasification of rice straw, using an integrated in situ tar reduction and hot-gas cleaning technique. The gasification temperature was set at 900°C and equilibrium ratio (ER) was 0.30 in the gasifier. In the in situ tar reduction method, the catalyst, dolomite with an amended ratio of 0–15% was introduced to the gasifier. The integrated hot-gas cleaning system applied a multi-packed tower to remove the tar, sulfur and/or chlorine byproduct in syngas at 250°C. The packed materials composed of zeolite, calcined dolomite and activated carbon. The experimental results indicated that the tar concentration of syngas was approximately 20 g/kg. However, in catalytic gasification with 5% dolomite addition, the tar concentration reduced to 17 g/kg. The tar reduction efficiency was approximately 15% by an in situ dolomite addition. When applying the integrated hot-gas cleanup system, the tar was virtually eliminated. The total tar elimination rate was almost 100% and the cleaned syngas could be applied in other energy utilization equipment. On the other hand, the H₂S and HCl concentration were 101 ppmv and 991 ppmv, respectively. After the integrated syngas cleaning system, the H₂S and HCl were decreased to 7.9 ppmv and 410 ppmv with a removal efficiency of 92.1% and 58.6%, respectively. It can be concluded that combining the in situ method with the integrated syngas cleaning system can effectively reduce the amount of byproduct and enhance the syngas quality in the gasification of rice straw.     

稻秸对Pb2+的吸附特性

为探讨稻秸对废水中Pb2+的吸附特性,通过静态试验研究了吸附时间、离子浓度、吸附剂用量、初始pH和温度对稻秸吸附Pb2+的影响,并分析了其吸附动力学、等温吸附平衡及热力学特征.结果表明:稻秸吸附Pb2+的过程进行得很快,60 min时去除率达到85.64%,其吸附动力学过程以准二级动力学方程拟合效果最好;吸附等温线符合Langmuir和Freundlich等温吸附模型,其中以Freundlich模型为最优,与吸附强度有关的常数在2～10之间,吸附容易发生,而使用Langmuir模型拟合最大吸附量的理论值可达13.67 mg/g;随着稻秸投加量的增加,Pb2+的去除率逐渐增加,单位吸附量逐渐减小;溶液初始pH对稻秸吸附Pb2+的影响较大,pH在4～6时去除率可达92%以上;稻秸对Pb2+的吸附受温度影响较小,吸附过程具有自发性、放热性和熵增特性.     

基于水蚯蚓摄食活性污泥的生长动力学研究

基于水蚯蚓摄食活性污泥的批量培养试验,考察了水蚯蚓在活性污泥中的生长规律,以及底物、溶解氧浓度由低到高变化对水蚯蚓比增长速率的影响.结果表明,在水温25℃±0.5℃、溶解氧4 mg.L-1、底物浓度4 000 mg.L-1条件下培养18周,水蚯蚓体重随培养时间的变化趋势较好地符合Gauss函数,最大比增长速率μAWma...     

控释肥条件下沿南四湖农田水稻吸氮特征

氮素是水稻必需营养元素中限制植物生长和形成产量的首要因素,同时也是南四湖水体主要营养性污染物之一.通过施用树脂包膜控释尿素不同氮肥量处理大田试验,研究了南四湖流域鱼台农田控释肥条件下水稻生育期的吸氮特征.结果表明,树脂包膜控释尿素对水稻产量有明显的促进作用,但并不随施氮量的增加呈线性增长,施用中氮量337.5 kg/h...     

改性稻草秸秆对重金属Pb~(2+)吸附作用研究

以农业废弃物稻草秸秆为原料,经过高锰酸钾和乙二胺改性后,制成对金属离子具有吸附作用的新型吸附材料,研究其对废水中Pb2+吸附效果,对吸附过程pH值和吸附剂投加量的影响以及吸附动力学特征和等温吸附特征进行研究,并将改性稻草秸秆用于鲕状赤铁矿选矿废水混凝后Pb2+深度处理。实验结果表明:改性稻草秸秆对Pb2+具有明显的吸附作用;pH在3~8之间,Pb2+吸附率均可达到80%以上;在室温下,pH为5~5.5,固液比为2 g/L时,吸附时间90 min时,吸附率可达98.7%;吸附过程符合二级动力学吸附过程,饱和吸附容量达到156.9 mg/g;不同浓度下吸附量与平衡浓度之间遵从Freundlich经验公式;混凝后鲕状赤铁矿选矿废水中Pb2+经过改性稻草秸秆深度吸附处理后,可以达到国家排放标准。