Sewage sludge ditch for recovering heavy metals can improve crop yield and soil environmental quality

• Indirect use of sludge in ditches alongside plants was tested in field experiments. • The dried and stabilized sludge in ditches was recovered with heavy metals. • Cd, Pb, Cu and Zn in the planted soil were all in a safe range. • The indirect use of sludge increased plant yield, soil N content and C storage. The treatment and disposal of municipal sewage sludge (MSS) is an urgent problem to be resolved in many countries. Safely using the nutrients within MSS to increase crop yield and enhance the fertility of poor soil could contribute to achieving sustainable development. An indirect use of MSS in ditches alongside Pennisetum hybridum plants was studied in field plots for 30 months and the contents of heavy metals and macronutrients were monitored in soil, sludge and plant samples. We found that the yield of P. hybridum was significantly increased by 2.39 to 2.80 times and the treated plants had higher N content compared with no sludge. In addition, the organic matter (OM) and N contents in the planted soil increased significantly compared with the initial soil. The OM content in the planted soil of the MSS treatment was 2.9 to 5.2 times higher than that with no sludge, and N increased by 2.0 to 3.8 times. However, MSS had no significant effect on the N, P and K contents in the soil at the bottom of the MSS ditch, and the content of heavy metals (Cd, Pb, Cu and Zn) were also within the safe range. Moreover, the moisture content and phytotoxicity of MSS after this indirect use were reduced and the heavy metal contents changed little, which is favorable to the further disposal of recovered MSS. Therefore, this indirect use of MSS is beneficial to agricultural production, soil quality and environmental sustainability.     

Influence of pore structure on biologically activated carbon performance and biofilm microbial characteristics

• Pore structure affects biologically activated carbon performance. • Pore structure determines organic matter (OM) removal mechanism. • Microbial community structure is related to pore structure and OM removal. Optimizing the characteristics of granular activated carbon (GAC) can improve the performance of biologically activated carbon (BAC) filters, and iodine value has always been the principal index for GAC selection. However, in this study, among three types of GAC treating the same humic acid-contaminated water, one had an iodine value 35% lower than the other two, but the dissolved organic carbon removal efficiency of its BAC was less than 5% away from the others. Iodine value was found to influence the removal of different organic fractions instead of the total removal efficiency. Based on the removal and biological characteristics, two possible mechanisms of organic matter removal during steady-state were suggested. For GAC with poor micropore volume and iodine value, high molecular weight substances (3500–9000 Da) were removed mainly through degradation by microorganisms, and the biodegraded organics (soluble microbial by-products,<3500 Da) were released because of the low adsorption capacity of activated carbon. For GAC with higher micropore volume and iodine value, organics with low molecular weight (<3500 Da) were more easily removed, first being adsorbed by micropores and then biodegraded by the biofilm. The biomass was determined by the pore volume with pore diameters greater than 100 μm, but did not correspond to the removal efficiency. Nevertheless, the microbial community structure was coordinate with both the pore structure and the organic removal characteristics. The findings provide a theoretical basis for selecting GAC for the BAC process based on its pore structure.     

Catalytic fast pyrolysis of walnut shell for alkylphenols production with nitrogen-doped activated carbon catalyst

• N-doped activated carbon was prepared for catalytic pyrolysis of walnut shell. • Alkylphenols were selectively produced from catalytic pyrolysis process. • The alkylphenols yield increased by 8.5 times under the optimal conditions. • Formation mechanism of alkylphenols was proposed. Alkylphenols are a group of valuable phenolic compounds that can be derived from lignocellulosic biomass. In this study, three activated carbons (ACs) were prepared for catalytic fast pyrolysis (CFP) of walnut shell to produce alkylphenols, including nitrogen-doped walnut shell-derived activated carbon (N/WSAC), nitrogen-doped rice husk-derived activated carbon (N/RHAC) and walnut shell-derived activated carbon (WSAC). Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were carried out to reveal the influences of AC type, pyrolytic temperature, and AC-to-walnut shell (AC-to-WS) ratio on the product distributions. Results showed that with nitrogen doping, the N/WSAC possessed stronger capability than WSAC toward the alkylphenols production, and moreover, the N/WSAC also exhibited better effects than N/RHAC to prepare alkylphenols. Under the catalysis of N/WSAC, yields of alkylphenols were significantly increased, especially phenol, cresol and 4-ethylphenol. As the increase of pyrolytic temperature, the alkylphenols yield first increased and then decreased, while high selectivity could be obtained at low pyrolytic temperatures. Such a trend was also observed as the AC-to-WS ratio continuously increased. The alkylphenols production achieved a maximal yield of 44.19 mg/g with the corresponding selectivity of 34.7% at the pyrolytic temperature of 400°C and AC-to-WS ratio of 3, compared with those of only 4.67 mg/g and 6.1% without catalyst. In addition, the possible formation mechanism of alkylphenols was also proposed with the catalysis of N/WSAC.     

The in situ treatment of TCE and PFAS in groundwater within a silty sand aquifer

Chlorinated ethenes such as trichloroethene (TCE), cis‐1,2‐dichloroethene (cis‐1,2‐DCE), and vinyl chloride along with per‐ and polyfluoroalkyl substances (PFAS) have been identified as chemicals of concern in groundwater; with many of the compounds being confirmed as being carcinogens or suspected carcinogens. While there are a variety of demonstrated in‐situ technologies for the treatment of chlorinated ethenes, there are limited technologies available to treat PFAS in groundwater. At a former industrial site shallow groundwater was impacted with TCE, cis‐1,2‐DCE, and vinyl chloride at concentrations up to 985, 258, and 54 µg/L, respectively. The groundwater also contained maximum concentrations of the following PFAS: 12,800 ng/L of perfluoropentanoic acid, 3,240 ng/L of perfluorohexanoic acid, 795 ng/L of perfluorobutanoic acid, 950 ng/L of perfluorooctanoic acid, and 2,140 ng/L of perfluorooctanesulfonic acid. Using a combination of adsorption, biotic, and abiotic degradation in situ remedial approaches, the chemicals of concern were targeted for removal from the groundwater with adsorption being utilized for PFAS whereas adsorption, chemical reduction, and anaerobic biodegradation were used for the chlorinated ethenes. Sampling of the groundwater over a 24‐month period indicated that the detected PFAS were treated to either their detection, or below the analytical detection limit over the monitoring period. Postinjection results for TCE, cis‐1,2‐DCE, and vinyl chloride indicated that the concentrations of the three compounds decreased by an order of magnitude within 4 months of injection, with TCE decreasing to below the analytical detection limit over the 24‐month monitoring period. Cis‐1,2‐DCE, and vinyl chloride concentrations decreased by over 99% within 8 months of injections, remaining at or below these concentrations during the 24‐month monitoring period. Analyses of Dehalococcoides, ethene, and acetylene over time suggest that microbiological and reductive dechlorination were occurring in conjunction with adsorption to attenuate the chlorinated ethenes and PFAS within the aquifer. Analysis of soil cores collected pre‐ and post‐injection, indicated that the distribution of the colloidal activated carbon was influenced by small scale heterogeneities within the aquifer. However, all aquifer samples collected within the targeted injection zone contained total organic carbon at concentrations at least one order of magnitude greater than the preinjection total organic carbon concentrations.     

水处理用活性炭改性研究

利用锆和氯化十六烷基三甲铵共同改性活性炭,制备一种新型去除污水中硝酸盐和磷酸盐的水处理吸附剂,并考察吸附剂加量、反应温度、pH值、共存阴离子等影响因素对吸附效果的影响。结果表明:锆-氯化十六烷基三甲铵改性活性炭(Zr-CTAC-AC)吸附剂适用于硝酸盐和磷酸盐浓度在100mg/L以下的污水,随着Zr-CTAC-AC加量的增加,硝酸盐、磷酸盐去除率逐渐增加,单位吸附量逐渐下降,Zr-CTAC-AC加量为8g/L时,硝酸盐去除率为79%,Zr-CTAC-AC加量为4.0g/L时,磷酸盐去除率可达91%,但应在较低的pH值范围内使用;反应温度对Zr-CTAC-AC的吸附效果影响不大;共存Cl-、HCO3^-和SO4^2-可使硝酸盐的吸附率降低,但对磷酸盐吸附率影响较小;1mol/L NaCl溶液可使吸附到Zr-CTAC-AC表面的硝酸盐90.9%左右被解吸出来,1mol/L NaOH溶液可使吸附到Zr-CTAC-AC表面的磷酸盐78.4%左右被解吸出来。Zr-CTAC-AC能够有效去除污水中硝酸盐和磷酸盐,制备方法简单,且可循环利用,处理成本低。     

蓝藻资源化技术研究及应用进展

针对蓝藻资源化问题,概述国内外利用蓝藻制备有机肥、提取高纯度藻蓝蛋白、制备活性炭和藻粉这4种利用方式的特点、现状及应用进展。提出,应从高温好氧堆肥技术、藻蓝蛋白提取技术和藻水分离技术这3个方面,解决其关键技术问题并进行进一步研究开发。     

微波强化CWPO工艺CuO_x-CeO_2/GAC催化剂的制备及其对二甲亚砜的降解

以颗粒活性炭(GAC)为载体、铜为活性组分、铈为助剂组分、草酸钠为沉淀剂,采用浸渍焙烧法制得CuO_x-CeO_2/GAC催化剂。以H_2O_2为氧化剂,微波强化催化湿式过氧化氢氧化(CWPO)处理二甲亚砜(DMSO)初始质量浓度为1 000 mg/L的废水,处理3 min后DMSO去除率达93.8%。催化剂第7次使用时DMSO去除率仍保持在75%以上。初始废水pH在3~9范围内,DMSO去除率均在85%以上。助剂Ce的加入提高了催化剂表面活性组分的分散性和稳定性,使催化剂的活性稳定性和使用寿命显著提高。     

聚硅酸钛制备及其助凝特性

采用在活化硅酸制备过程中加入适量Ti Cl4的方法,试制了一种新型无机高分子助凝剂—聚硅酸钛。研究了不同[Si]/[Ti]条件下制备的聚硅酸钛在固定p H值的水中分散物的粒径和Zeta电位随着活化时间的变化趋势,并与活化硅酸作比较。结果表明,在Si/Ti=20,活化48 h的条件下能制备出较为稳定的聚硅酸钛。与活化硅酸相比,聚硅酸钛在水中的分散物具有较大的粒径和更高的Zeta电位。通过对比制备的活化硅酸和聚硅酸钛的红外图谱发现,聚硅酸钛中有TiO-Si键,证明钛离子参与了聚合反应,新生成的化学键提高了它的聚合度和稳定性。采用硫酸铝为混凝剂,聚硅酸钛为助凝剂进行混凝除浊实验。测定了絮凝体的Zeta电位和混凝沉淀后的上清液浊度,研究了硫酸铝投加量和混凝p H对聚硅酸钛助凝效果的影响。结果表明,投加适量的聚硅酸钛助凝剂,明显提高了混凝除浊效果且拓宽了有效混凝p H值的范围。     

硫酸盐还原菌污泥固定化特性

采用玉米芯为碳源,聚乙烯醇(PVA)为包埋载体,饱和硼酸(H3BO3)为交联剂,研究了硫酸盐还原菌污泥(SRBS)、铁屑、麦饭石共固处理合成煤矿酸性废水的最优配比与机理,并分析了固定化过程中小球稳定性及活性的变化规律。实验结果表明,SRBS投加量是影响处理效果的最显著因子,当投加30%SRBS、2%铁屑、3%麦饭石时SO2-4、Mn2+去除率分别为94.13%和84.39%,溶液p H为7.03,未检测出Fe2+;随着交联时间的延长,小球膨胀率及SO2-4还原率分别呈线性与指数下降,从保持小球稳定性与活性角度考虑,可将交联时间设定为4~8 h;该法可为市政污泥的处置以及生物法处理煤矿酸性废水的工程应用提供技术参考。     

活性炭吸附和两级Fenton氧化组合工艺处理高盐对氨基苯酚生产废水

采用活性炭吸附和两级Fenton氧化组合工艺对高盐度对氨基苯酚生产废水进行了处理实验研究。结果表明,p H值对活性炭去除有机物的影响较小。当活性炭投加量为4 g/L时,TOC去除率61%。分级加药可以有效提高Fenton氧化对有机物的去除效率。在温度为25℃、p H为3、30%H2O2投加量为3%(V/V)、Fe2+/H2O2摩尔比为0.05时,两级Fenton氧化处理后,出水TOC降至150 mg/L以下。此外,Fenton氧化后形成氢氧化铁污泥颗粒粒径为4.5μm,经过聚丙烯酰胺(PAM)絮凝之后,污泥的粒径明显增加,过滤特性改善。PAM絮凝效果依赖于溶液的p H值,当p H超过10后会失去作用,故在使用过程中需要严格控制溶液的p H值。