New insights into different surfactants’ impacts on sludge fermentation: Focusing on the particular metabolic processes and microbial genetic traits

• The promoting effects for VFA generation follow the order of APG>SDBS>HTAB. • Surfactants improve the WAS solubilization/hydrolysis and acidification processes. • The VFA promotion is associated with surfactants’ distinctive characteristics. • Surfactants induce the enrichment of functional bacteria for VFA biosynthesis. • The vital genes for substrates delivery, metabolism, and VFA yields are upregulated. Surfactants were expected to exhibit positive effects on the waste activated sludge (WAS) disposal. However, the systematic comparison of different categories of surfactants on the WAS fermentation and the functional mechanisms, especially microbial metabolic traits, have not yet been precisely explored. This study revealed the positive effects of different surfactants on the volatile fatty acid (VFA) production, which followed the order of alkyl polysaccharides (APG)>sodium dodecylbenzene sulfonate (SDBS)>hexadecyl trimethyl ammonium bromide (HTAB). Mechanistic exploration found that the presence of different surfactants improved solubilization and hydrolysis steps, and then contributed to the subsequent acidification with different efficiencies. The functional microorganisms associated with VFA generation were enriched in surfactant-conditioned reactors. Metagenomic analysis further indicated that the key genes involved in the particular process of VFA generation were over-expressed. The simultaneous bioavailable substrate improvement, functional bacterial enrichment, and metabolic activity upregulation induced by different surfactants jointly contributed to VFA promotion during WAS fermentation. This study could provide a comprehensive realization of surfactants’ impacts on the WAS fermentation process, and more importantly, it reminded the public to discern the distinct interplaying effects induced by different chemicals in regulating the WAS disposal and resource recovery.     

季铵盐离子液体改性活性炭及其热安全性研究*

为进一步提高活性炭对VOCs的吸附性能和热安全性,采用铵盐类离子液体改性原始活性炭,优化其理化性质。结果表明:改性活性炭表面生成新的无机盐化合物,C=O、-OH、C-O、-COOH和C-S基团增加;孔隙结构增多且分布均匀,比表面积及微孔体积增大;改性后活性炭对甲苯的吸附量提高3.14倍,吸附效率明显提升;在固定碳的燃烧阶段,改性活性炭活化能为54.44 kJ·mol-1,是改性前活性炭的1.38倍,活化能增大,物质稳定性增强;当粒径为120~150目及200目以上时,改性前后活性炭的自燃温度分别从328.4 ℃、319.3 ℃增长至355.1 ℃、345.7 ℃。因此,负载季铵盐离子液体可有效提高活性炭吸附性能和热安全性,研究结果可为优化VOCs处理工艺提供参考。     

酸化大豆蛋白废水的厌氧处理

对有机质浓度高,成分单一,蛋白质、总氮浓度较高,易酸化,且已酸化程度较高的大豆蛋白废水,确定以新型内循环厌氧反应池为主的处理工艺,在原废水ρ(COD)为11809~15040mg/L时,总出水浓度192~350mg/L,去除率达到96.2%~97.5%。新的内循环厌氧反应池具有高度小、结构简单、污染物去除率高的特征,COD运行负荷达6.0~7.5kg/(m3.d),COD去除率达88%~93%。当COD运行负荷5.0~7.0kg/(m3.d)时,该池内循环管道形成了连续的较强内回流。     

基于微波辐射研究城市污水污泥脱水特性

选用沈阳市仙女河污水处理厂和北部污水处理厂污水污泥作为微波脱水试验物料,分析物料性质、辐射强度、辐射时间以及添加剂投入量等对污泥脱水率和有机质损失率的影响. 结果表明:污泥中水分含量高的脱水效果最好,经过微波处理后的污泥有机质含量仍较高;辐射时间是最主要的影响因素,在540 W下辐射2～5 min即可达到良好效果;在合适的辐射时间下540～900 W都能达到良好的脱水效果,但在900 W时有机质的损失率较大,达到65.64%;添加剂投入量对污泥脱水基本不起作用,但可改变污泥微波干燥后的性状. 同时,运用灰色关联分析得到决定微波试验运行系统的主次因素,最后建立了影响因素对污泥脱水率和有机质损失率的经验公式.      

轻质陶粒滤料生态滤床的挂膜与启动研究

以自行设计的反应器作为生态滤床的基础,采用活性污泥作为接种污泥,采用轻质陶粒作为生态滤床的滤料,对其进行挂膜.在整个挂膜过程中,温度控制在中温条件下,进水pH值控制在7左右,水力停留时间为24 h,进水方式为连续进水,并根据需要对曝气量进行调节.在挂膜过程中对进、出水的COD、NH_3-N、TP、Cl~-和pH进行检测,并刮取少量轻质陶粒上的生物膜制成镜检切片后用多媒体显微镜对生物膜的形态进行观察.研究结果表明,在中温条件下采用活性污泥作为接种污泥,以轻质陶粒为滤料的生态滤床在15 d内挂膜成功;且随着进水污染负荷的提高,其去除率也逐渐提高,其中COD的去除率最后稳定在95%左右,NH3-N的去除率稳定在85%左右,TP的去除率在挂膜后期达到了80%以上;Cl~-作为微生物所需的微量元素在微生物生长高峰期为50%,稳定期保持在20%左右;进水pH保持在7左右,出水pH略高于进水,在8左右;从第13 d和第15 d的切片可观察到轮虫这种象征生物膜成熟的微生物的出现,此外还有大量的丝状菌和菌胶团.     

等离子体改性对活性炭纤维表面化学结构的影响

采用放电等离子体对活性炭纤维表面进行改性,通过改变活性炭纤维的化学官能团来强化活性炭纤维对SO2和NOx的吸附和催化作用。利用XPS、FTIR等方法对改性活性炭纤维的化学性质进行表征,研究了活性炭纤维表面官能团在等离子体改性过程中的转化规律和机理。实验结果表明:放电改性过程可以有效地向活性炭纤维表面引入有利于脱硫脱氮的含氧、含氮官能团;当电压为8kV,放电时间为5min时,放电改性活性炭纤维的效果最佳。     

从造纸污泥中提取木质素制备缓蚀阻垢剂

以造纸污泥为原料,用碱溶酸析法提取其中的木质素,对木质素进行磺化改性后,与有机磷、锌盐等进行复配,以提高缓蚀阻垢效果。探讨了主原料配比、药剂投加量、反应温度、反应时间等对药剂性能的影响。结果表明:由该法制备的缓蚀阻垢剂性能较好,为造纸污泥的综合利用提供了一条新途径。     

水解酸化工艺的改进

综合水解酸化工艺传统的"膜法"和"泥法"两种工艺的优点,开发一种新的水解酸化工艺。把新工艺和传统的"膜法"工艺并联运行,进行对比实验,发现新工艺在有机物和色度的去除以及提高废水的可生化性方面均具有优势,COD去除率20%~30%,色度去除率60%,出水ρ(BOD5)/ρ(COD)在0.7左右。     

Use of thermal analysis techniques (TG-DSC) for the characterization of diverse organic municipal waste streams to predict biological stability prior to land application

The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO₂ respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts.     

Techno-economic evaluation of ultrasound and thermal pretreatments for enhanced anaerobic digestion of municipal waste activated sludge

To enhance the anaerobic digestion of municipal waste-activated sludge (WAS), ultrasound, thermal, and ultrasound + thermal (combined) pretreatments were conducted using three ultrasound specific energy inputs (1000, 5000, and 10,000 kJ/kg TSS) and three thermal pretreatment temperatures (50, 70 and 90 °C). Prior to anaerobic digestion, combined pretreatments significantly improved volatile suspended solid (VSS) reduction by 29-38%. The largest increase in methane production (30%) was observed after 30 min of 90 °C pretreatment followed by 10,000 kJ/kg TSS ultrasound pretreatment. Combined pretreatments improved the dimethyl sulfide (DMS) removal efficiency by 42-72% but did not show any further improvement in hydrogen sulfide (H₂S) removal when compared with ultrasound and thermal pretreatments alone. Economic analysis showed that combined pretreatments with 1000 kJ/kg TSS specific energy and differing thermal pretreatments (50-90 °C) can reduce operating costs by $44-66/ton dry solid when compared to conventional anaerobic digestion without pretreatments.