Electron donor capacity of reducing dissolved organic matter from crop residue decomposition as probed by chronoamperometry

Reducing dissolved organic matters (RDOMs) from the anaerobic decomposition of crop residue can greatly affect the physicochemical and biological properties of soils. Electrochemical methods that can effectively protect them from oxidation and rapidly obtain results, such as differential pulse voltammetry (DPV), have been applied to qualitatively analyzing properties of RDOMs. However, the donated amount of electrons from RDOMs as a capacity factor may be more crucial for evaluating their important roles. For the first time, matured chronoamperometry (CA) was applied to quantitatively determining the electron donor capacities of RDOMs in crop residue management. The electron donor capacities of RDOMs from green manure were much higher than those from rice straw, which indicated that the former had greater effect on the redox status and reactions of soil. Chronoamperometry was proposed as a practical and effective method to quantitatively characterize RDOMs from residue decomposition.     

Anaerobic degradation of nonylphenol in soil

This study investigated the effects of various factors on the anaerobic degradation of nonylphenol (NP) in soil. The results show that the optimal pH for NP degradation was 7.0 and that the degradation rate was enhanced when the temperature was increased. The addition of compost enhanced NP degradation. The individual addition of the electron donors lactate, acetate, and pyruvate inhibited NP degradation. The high-to-low order of NP degradation rates under three anaerobic conditions was sulfate-reducing conditions > methanogenic conditions > nitrate-reducing conditions. The results show that sulfate-reducing bacteria, methanogen, and eubacteria are involved in the anaerobic degradation of NP, with sulfate-reducing bacteria being a major component of the soil. Of the anaerobic strains isolated from the soil samples, strain AT3 expressed the best ability to biodegrade NP.     

Low-heat alkaline pretreatment of biomass for dairy anaerobic codigestion

In this research, low-heat alkaline pretreatment was evaluated to determine the extent to which urban landscape waste (yard waste), corn stover, and switchgrass could be codigested under conditions typical of US farm-based anaerobic digestion (AD). Waste heat from combined heat and power (CHP) units associated with AD could make such pretreatment economical. Short-term batch digestion studies and 8-week continuous-feed studies were used to screen and evaluate various pretreatment conditions. Results indicate that maple and oak leaves did not digest well, even with pretreatment. Pretreatment did improve digestion of corn leaves and stalks as well as switchgrass. However, these materials also digested reasonably well even without pretreatment. No digester operational problems were observed during continuous-feed studies of intermittently stirred bench top digesters, but optimal levels of alkali, temperature, and pretreatment time may be specific to the feedstock, particle size, and digester loading rate. Results suggest that some common lignocellulosic biomass materials, such as corn stover and switchgrass, could be successfully codigested in many existing farm-based digesters. Interestingly, without pretreatment, switchgrass digestion improved over 20-fold when digested with seed culture from a dairy digester compared to seed culture from a municipal digester, suggesting that culture acclimation could be as important as pretreatment in improving digestion of specific lignocellulosic feedstocks.     

Field and laboratory studies of the fate and enantiomeric enrichment of venlafaxine and O-desmethylvenlafaxine under aerobic and anaerobic conditions

The stereoselectivity of R,S-venlafaxine and its metabolites R,S-O-desmethylvenlafaxine, N-desmethylvenlafaxine, O,N-didesmethylvenlafaxine, N,N-didesmethylvenlafaxine and tridesmethylvenlafaxine was studied in three processes: (i) anaerobic and aerobic laboratory scale tests; (ii) six wastewater treatment plants (WWTPs) operating under different conditions; and (iii) a variety of wastewater treatments including conventional activated sludge, natural attenuation along a receiving river stream and storage in operational and seasonal reservoirs. In the laboratory and field studies, the degradation of the venlafaxine yielded O-desmethylvenalfaxine as the dominant metabolite under aerobic and anaerobic conditions. Venlafaxine was almost exclusively converted to O-desmethylvenlafaxine under anaerobic conditions, but only a fraction of the drug was transformed to O-desmethylvenlafaxine under aerobic conditions. Degradation of venlafaxine involved only small stereoisomeric selectivity. In contrast, the degradation of O-desmethylvenlafaxine yielded remarkable S to R enrichment under aerobic conditions but none under anaerobic conditions. Determination of venlafaxine and its metabolites in the WWTPs agreed well with the stereoselectivity observed in the laboratory studies. Our results suggest that the levels of the drug and its metabolites and the stereoisomeric enrichment of the metabolite and its parent drug can be used for source tracking and for discrimination between domestic and nondomestic wastewater pollution. This was indeed demonstrated in the investigations carried out at the Jerusalem WWTP.     

反硝化除磷污泥的厌氧释磷与缺氧吸磷特性研究

为研究厌氧释磷过程中的影响因素,以连续流A 2N双污泥中试污泥为样品,考察了碳源种类、碳源浓度、pH值以及温度对反硝化除磷污泥厌氧释磷的影响。结果表明:乙酸为碳源时释磷效果最佳,其次是葡萄糖,甲醇为碳源时释磷效果较差。MLSS为1 200 mg/L左右时,投加200 mg/L的COD即可保证充分释磷。pH值为6.3~8.8,对厌氧释磷效果影响不大,适当提高pH值有利于提高释磷速率。温度为20~30℃,释磷效果较好。另外,实验同时研究了反硝化除磷污泥分别利用不同电子受体(硝氮、氧气)的吸磷特性。以硝氮为电子受体的反硝化吸磷过程中,前15min的反硝化吸磷脱氮速率最高,吸磷速率与反硝化速率分别为11.5、10.4 mgN/gVSS·h;以氧气为电子受体的好氧吸磷过程中,前15 min的好氧吸磷速率最高,达到20.4 mgP/gVSS·h,大约为反硝化吸磷的2倍。     

造纸污水处理厌氧系统沼气综合利用

目前厌氧系统已广泛应用于造纸废水处理,厌氧处理系统过程中产生大量的沼气,而沼气的热值很高,很有利用的价值,而本文结合笔者曾编制的某造纸废水处理厌氧技术改造环评探讨造纸污水处理厌氧系统沼气综合利用技术。该项目的实施,既减少了造纸废水的出水浓度,又提高了节能环保效益。     

酸性条件下厌氧颗粒污泥活性抑制与恢复试验研究

取食品生产废水处理中试工程运行中现有的厌氧颗粒污泥进行活性抑制与恢复试验。通过慢性致毒与急性致毒作用的对比,分析酸性条件对颗粒污泥的抑制作用,研究颗粒污泥的耐酸性,并考察污泥活性恢复方法。结果表明:当进水pH=6.5,颗粒污泥活性受到轻微抑制,不影响系统的稳定运行;当pH值下降至4.5时,COD去除率和产甲烷量均趋于零。同时使用调节进水pH值、降低进水有机负荷、提高进水碱度以及调整水力停留时间等4种方法能有效恢复污泥活性,活性达到抑制前的80%左右。     

五氯苯酚在厌氧颗粒污泥中的吸附研究

在血清瓶中进行的分批实验中,研究了UASB和EGSB反应器厌氧颗粒污泥对五氯苯酚(PCP)的吸附、解吸规律.结果表明,吸附和解吸在接触PCP 2.5 h内达到平衡,吸附和解吸过程都符合Freundich等温方程,PCP的吸附机制为恒定的分配吸附.来自UASB反应器中活的颗粒污泥吸附能力大于灭活的颗粒污泥,Freundich等温方程吸附常数K值分别为0.557 0和0.037 9.UASB反应器颗粒污泥对PCP的吸附能力大于EGSB反应器颗粒污泥,Freundich等温方程吸附常数K值分别为0.557和0.263.     

Kinetic analysis of the anaerobic digestion of untreated vinasses and vinasses previously treated with Penicillium decumbens

A kinetic study was carried out on the anaerobic digestion of untreated vinasses and vinasses previously fermented with Penicillium decumbens. Two 1-l volume continuous-flow stirred tank reactors (CFSTR) operating at mesophilic temperature (35 degrees C) were used for the study. One reactor was fed with untreated vinasses (COD concentration of 80.5 g/l) and the other with vinasses previously fermented (COD concentration of 23.0 g/l). Both reactors were operated at organic loading rates in the range of 1.5-7.5 g chemical oxygen demand (COD)/l-d. The results obtained were evaluated using the Chen-Hashimoto methane production model to determine the values of the maximum specific growth rate (micromax) and the model kinetic constant (K) of the process for each case studied. The kinetic constants (micromax and K) were affected by the pre-treatment, and the respective values were 9.6 and 6.9 times higher for pretreated vinasses than those of untreated vinasses. This was significant at the 95% confidence level. This behaviour is believed to be due to the lower levels of phenolic compounds present in the pretreated vinasses, as compared to untreated vinasses, resulting in an improved process performance, kinetics and stability. Finally, the experimental values of methane production were reproduced with deviations equal to or less than 4% and 10% for pretreated and untreated vinasses, respectively.     

温度对厌氧降解邻苯二甲酸二酯的影响研究

本试验是针对温度对厌氧降解邻苯二甲酸二酯影响的研究 ,目的是寻找适应这种反应的最佳温度或最佳温度区间。研究表明 ,对于原始污泥来说 ,最佳温度是其所生存的原始温度 ,即消化处理温度 3 7℃ ,对于污泥和填埋场渗出液的富集菌群来说 ,由于人工选择培养的介入 ,最佳温度有向高温偏移的趋势