Effect of sodium dodecyl benzene sulfonate (SDBS) on the performance of anaerobic co-digestion with sewage sludge,food waste,and green waste

Abstract

The anionic detergent sodium dodecyl benzene sulfonate (SDBS) inhibits anaerobic solid waste fermentation process in mesophilic anaerobic digesters. In this study, the effect SDBS on the performance of anaerobic digestion (AD) of mixture of sewage sludge, food waste, and green waste serving as substrate was investigated. The batch experiments were conducted with five SDBS concentrations namely 0, 0.01, 0.02, 0.05, 0.1, and 0.2?g/g (SDBS/dry sludge) under mesophilic condition (37?±?1?°C) and lasted for 63?days. The results showed that the presence of SDBS remarkably increased the release of protein and carbohydrate, and resulting in the serious accumulation of volatile fatty acids (VFAs), especially for propionate accumulation. Likewise, the observed variations in enzyme activities associated with different stage of AD revealed that methanogenesis was quite sensitive to SDBS and inhibited by the increase of SDBS addition. Meanwhile, the presence of SDBS decreased the pH value and the concentration of free ammonia, but increased the concentration of NH₄⁺-N. Furthermore, the production of biogas was reduced by SDBS. In conclusion, SDBS addition has a negative impact on anaerobic co-digestion. On the one hand, methanogens were severely inhibited and biogas yield decreased remarkably, on the other hand, the accumulation of VFAs was excessive. Thus, the presence of surfactant (SDBS) in the municipal organic waste should be concerned during the waste disposal via anaerobic digestion process.     

Evaluation of hydrogen producing cultures using pretreated food waste

In order to enhance bio-hydrogen production from food waste, pretreatment methods are widely used. The influence of the initial pH and autoclaving were investigated in batch experiments. Fermentative studies showed that pure cultures like Clostridium beijerinckii could directly utilize raw food waste to produce hydrogen, while other cultures (Clostridium butyricum and Clostridium pasteurianum) could produce hydrogen only after pH adjustment. In this case, the optimal starting pH of the culture was found to be 7. Autoclaving could further enhance hydrogen yields due to increased hydrolysis of food waste. The maximum hydrogen yield was achieved by C. butyricum (38.9 mL-H₂/g-VS_added) after autoclaving food waste with pH adjustment at 7. In addition, the ratio acetic to butyric acid was decreased by autoclaving pretreatment, because butyrate metabolic pathway was favored in the fermentation process. However, suitable pH for bacteria growth and the low ammonia production could be achieved from autoclaving food waste.     

Simultaneous biohydrogen (H2) and bioplastic (poly-β-hydroxybutyrate-PHB) productions under dark,photo, and subsequent dark and photo fermentation utilizing various wastes

The present study is focused on bio hydrogen (H₂) and bioplastic (i.e., poly-β-hydroxybutyrate; PHB) productions utilizing various wastes under dark fermentation, photo fermentation and subsequent dark-photo fermentation. Potential bio H₂ and PHB producing microbes were enriched and isolated. The effects of substrate (rice husk hydrolysate, rice straw hydrolysate, dairy industry wastewater, and rice mill wastewater) concentration (10–100%) and pH (5.5–8.0) were examined in the batch mode under the dark and photo fermentation conditions. Using 100% rice straw hydrolysate at pH 7, the maximum bio H₂ (1.53 ± 0.04 mol H₂/mol glucose) and PHB (9.8 ± 0.14 g/L) were produced under dark fermentation condition by Bacillus cereus. In the subsequent dark-photo fermentation, the highest amounts of bio H₂ and PHB were recorded utilizing 100% rice straw hydrolysate (1.82 ± 0.01 mol H₂/mol glucose and 19.15 ± 0.25 g/L PHB) at a pH of 7.0 using Bacillus cereus (KR809374) and Rhodopseudomonas rutila. The subsequent dark-photo fermentative bio H₂ and PHB productions obtained using renewable biomass (i.e., rice husk hydrolysate and rice straw hydrolysate) can be considered with respect to the sustainable management of global energy sources and environmental issues.     

Effect of pre-treatment and hydraulic retention time on biohydrogen production from organic wastes

This study investigated the effect of pre-treatment and hydraulic retention time (HRT) on biohydrogen production from organic wastes. Various pre-treatments including thermal, base, acid, ultrasonication, and hydrogen peroxide were applied alone or in combination to enhance biohydrogen production from potato and bean wastewater in batch tests. All the pre-treated samples showed higher hydrogen production than the control tests. Hydrogen peroxide pre-treatment achieved the best results of 939.7 and 470 mL for potato and bean wastewater, respectively. Continuous biohydrogen production from sucrose, potato and bean wastewater was significantly influenced by reducing the HRT as 24, 18 and 12 h. Sucrose and potato showed similar behavior, where the hydrogen production rate (HPR) increased with decreasing the HRT. Optimum hydrogen yield results of 320 mL-H₂/g-VS (sucrose) and 150 mL-H₂/g-VS (potato) were achieved at HRT of 18 h. Bean wastewater showed optimum HPR of 0.65 L/L.d with hydrogen yield of 80 mL-H₂/g-VS at 24 h HRT.     

酸性条件下模拟高浓度有机废水厌氧水解酸化试验研究

采用容积为10.2 L的自制产酸反应器,在温度为(35±1)℃,出水pH为4.1～4.5的条件下,以红糖为基质分别接种絮状污泥和颗粒污泥进行高浓度有机废水的厌氧水解酸化的研究,连续运行57 d.结果表明,整个试验过程中,COD去除率为16%左右;挥发性脂肪酸(VFAs)随着糖负荷的提升而提高,VFAs中乙酸的平均含量超过了50%;后期产气中的氢气含量分别稳定在55%和30%左右;微量元素Fe、Co、Ni的添加对反应器的运行效果有正效应;显微镜观察表明,经过57 d的运行,已经培养出沉降性能好、比较密实,粒径大于0.5 mm的颗粒污泥.     

产蛋白酶混合菌系对碱性剩余污泥水解酸化的影响

为提高剩余污泥水解酸化过程中挥发性脂肪酸（VFAs）的累积,从剩余污泥中分离产蛋白酶活力较高的耐碱细菌,并构建产蛋白酶混合菌系．将其接种于碱性（ pH 10．0）发酵剩余污泥的不同发酵时期,评价其对溶解性有机化合物和VFAs累积的影响,探讨利用剩余污泥生产VFAs的最佳条件．从剩余污泥中分离到2株产蛋白酶活力较高的耐碱细菌,并构建产蛋白酶混合菌系．在发酵初期接种混合菌系效果最显著,且可缩短发酵启动时间2 d．发酵初期接种混合菌系后,溶解性蛋白质和VFAs质量浓度在第8天均达到最高值,分别为未接种混合菌系样品中相应值的1．25和1．41倍,分别占溶解性化学需氧量（ SCOD）总量的29．87％和44．54％．乙酸和丙酸为剩余污泥水解酸化过程中VFAs的主要组分,分别占VFAs总量的50．69％和18．19％．     

厌氧水解-SNAD工艺处理低碳氮比农村生活污水

为解决农村生活污水的高效除碳脱氮问题,以厌氧水解-同时硝化反硝化厌氧氨氧化(SNAD)工艺处理低C/N比农村生活污水。实验结果表明:水解酸化单元进水C/N比为2∶1时,COD的去除率达到69%;产物VFA主要成分为乙酸、丙酸和正丁酸,平均含量分别为88.4%、6.5%与5.1%,VFAs/COD比为0.74;出水C/N比为3∶5。水解酸化单元出水进入SNAD脱氮单元,通过亚硝化、反硝化与厌氧氨氧化的耦合作用,该单元COD与总氮的去除率分别可达到76.7%和84.1%。厌氧水解-SNAD组合工艺COD与总氮总去除率分别达到92.8%和84.1%。     

预处理法促进剩余活性污泥生产挥发性脂肪酸

采用不同方法（加热法,加热超声法,碱处理法）对污泥进行预处理,考察污泥水解酸化效果。结果表明：经加热超声法预处理的活性污泥,在温度315℃,机械搅拌转速450rpm的条件下,污泥厌氧水解酸化12h后,挥发性脂肪酸（VFAs）的产量最高可达3035mg/L,其中主要成分为乙酸841mg/L、丙酸194mg/L、丁酸420mg/L、戊酸1579mg/L。     

内置式连续液-液萃取法对污泥厌氧消化液中挥发性脂肪酸的测定

采用内置式连续液-液萃取、气相色谱内标定量法同时测定厌氧消化液中6种主要VFAs,其中乙酸、丙酸、异丁酸、正丁酸、异戊酸、正戊酸的加标回收率分别为86.7%、93.8%、94.5%、96.2%、103%和107%。样品经萃取后有效去除了无机盐杂质,减小了由直接进样造成的设备损伤,提高了检测数据的准确度和精密度。