干式厌氧发酵反应器的中试研究

采用一种新型卧式推流干式厌氧发酵系统用于猪粪、秸秆和污泥处理中试研究。试验阶段干式厌氧发酵系统表现出较好的稳定性,运行效果良好。新型卧式推流干式厌氧反应器能够有效解决传热和传质差的问题。当进料含水率为80%、回流比为50%时,出料含水率为84%~88%,有机质含量为60%~70%,酸碱比基本维持在0. 1~0. 3。干式厌氧发酵系统的最佳有机负荷为4. 8 kg/(m^3·d),有机物降解率为40%~50%,容积产气率可达2~3 m^3/(m^3·d)。猪粪与秸秆协同厌氧发酵的效果好于猪粪、秸秆单一物料,因为猪粪与秸秆混合可以将进料的C/N值控制在厌氧发酵的最佳范围(20~30)。猪粪和秸秆混合发酵系统中,C/N值的提高使得氨氮浓度呈下降趋势,这在一定程度上避免了系统出现氨抑制的情况。     

Innovative process scheme for removal of organic matter, phosphorus and nitrogen from pig manure

Disposal of pig manure often requires treatment with respect to environmental legislations. In this study different processes for reduction of the organic matter (anaerobic digestion, effluent separation by decanter centrifugation, membrane microfiltration, post-digestion in upflow anaerobic sludge blanket (UASB) reactor, partial oxidation), nitrogen (oxygen-limited autotrophic nitrification-denitrification, OLAND) and phosphorus (phosphorus removal by precipitation as struvite, PRS) from pig manure were tested. Results obtained showed that microfiltration was unsuitable for pig manure treatment. PRS treated effluent was negatively affecting the further processing of the pig manure in UASB, and was therefore not included in the final process flow scheme. In a final scheme (PIGMAN concept) combination of the following successive process steps was used: thermophilic anaerobic digestion with sequential separation by decanter centrifuge, post-digestion in UASB reactor, partial oxidation and finally OLAND process. This combination resulted in reduction of the total organic, nitrogen and phosphorus contents by 96%, 88%, and 81%, respectively.     

Fate of steroid hormones and endocrine activities in swine manure disposal and treatment facilities

Manure may contain high concern endocrine-disrupting compounds (EDCs) such as steroid hormones, naturally produced by pigs, which are present at μg L⁻¹ levels. Manure may also contain other EDCs such as nonylphenols (NP), polycyclic aromatic hydrocarbons (PAHs) and dioxins. Thus, once manure is applied to the land as soil fertilizer these compounds may reach aquifers and consequently living organisms, inducing abnormal endocrine responses. In France, manure is generally stored in anaerobic tanks prior spreading on land; when nitrogen removal is requested, manure is treated by aerobic processes before spreading. However, little is known about the fate of hormones and multiple endocrine-disrupting activities in such manure disposal and treatment systems. Here, we determined the fate of hormones and diverse endocrine activities during manure storage and treatment by combining chemical analysis and in vitro quantification of estrogen (ER), aryl hydrocarbon (AhR), androgen (AR), pregnane-X (PXR) and peroxysome proliferator-activated γ (PPARγ) receptor-mediated activities. Our results show that manure contains large quantities of hormones and activates ER and AhR, two of the nuclear receptors studied. Most of these endocrine activities were found in the solid fraction of manure and appeared to be induced mainly by hormones and other unidentified pollutants. Hormones, ER and AhR activities found in manure were poorly removed during manure storage but were efficiently removed by aerobic treatment of manure.     

Enhancing anaerobic digestibility and phosphorus recovery of dairy manure through microwave-based thermochemical pretreatment

Anaerobic digestion and struvite precipitation are two effective ways of treating dairy manure for recovering biogas and phosphorus. Anaerobic digestion of dairy manure is commonly limited by slow fiber degradation, while struvite precipitation is limited by the availability of orthophosphate. The aim of this work is to study the possibility of using microwave-based thermochemical pretreatment to simultaneously enhance manure anaerobic digestibility (through fiber degradation) and struvite precipitation (through phosphorus solubilization). Microwave heating combined with different chemicals (NaOH, CaO, H₂SO₄, or HCl) enhanced solubilization of manure and degradation of glucan/xylan in dairy manure. However, sulfuric acid-based pretreatment resulted in a low anaerobic digestibility, probably due to the sulfur inhibition and Maillard side reaction. The pretreatments released 20-40% soluble phosphorus and 9-14% ammonium. However, CaO-based pretreatment resulted in lower orthophosphate releases and struvite precipitation efficiency as calcium interferes with phosphate to form calcium phosphate. Collectively, microwave heating combined with NaOH or HCl led to a high anaerobic digestibility and phosphorus recovery. Using these two chemicals, the performance of microwave- and conventional-heating in thermochemical pretreatment was further compared. The microwave heating resulted in a better performance in terms of COD solubilization, glucan/xylan reduction, phosphorus solubilization and anaerobic digestibility. Lastly, temperature and heating time used in microwave treatment were optimized. The optimal values of temperature and heating time were 147 °C and 25.3 min for methane production, and 135 °C and 26 min for orthophosphate release, respectively.     

Modeling of ammonia speciation in anaerobic digesters

Anaerobic digestion of high-nitrogen wastes such as animal manure can be inhibited by high concentrations of un-ionized ammonia, NH₃ (aq). Understanding the toxicity of NH₃ (aq) to anaerobic digestion requires a method for determining its concentration. Previous work on ammonia toxicity in anaerobic digesters has utilized a simple equilibrium calculation for estimating NH₃ (aq) concentration from total ammonia, temperature, and pH. This approach is not appropriate for concentrated solutions. In this work, a speciation model for major solutes in anaerobic digesters, based on Pitzer's ion-interaction approach, is presented. Model simulations show that the simple equilibrium calculation (without corrections for non-ideal behavior) substantially overestimates NH₃ (aq) concentration for all but dilute digesters. This error in concentration determination increases with total solids content and is estimated to be greater than 40% for a digester fed dairy manure with 5% total solids or swine manure with 3% total solids. However, including an estimate of the activity coefficient for NH₄⁺ in the simple equilibrium calculation results in much more accurate estimates of NH₃ (aq) concentration. In this case, the estimated error is less than 10% in the absence of struvite precipitation at the highest total solids contents considered.     

Anaerobic biodegradability and treatment of grey water in upflow anaerobic sludge blanket (UASB) reactor

Feasibility of grey water treatment in an upflow anaerobic sludge blanket (UASB) reactor operated at different hydraulic retention time (HRT) of 16, 10 and 6h and controlled temperature of 30 degrees C was investigated. Moreover, the maximum anaerobic biodegradability without inoculum addition and maximum removal of chemical oxygen demand (COD) fractions in grey water were determined in batch experiments. High values of maximum anaerobic biodegradability (76%) and maximum COD removal in the UASB reactor (84%) were achieved. The results showed that the colloidal COD had the highest maximum anaerobic biodegradability (86%) and the suspended and dissolved COD had similar maximum anaerobic biodegradability of 70%. Furthermore, the results of the UASB reactor demonstrated that a total COD removal of 52-64% was obtained at HRT between 6 and 16 h. The UASB reactor removed 22-30% and 15-21% of total nitrogen and total phosphorous in the grey water, respectively, mainly due to the removal of particulate nutrients. The characteristics of the sludge in the UASB reactor confirmed that the reactor had a stable performance. The minimum sludge residence time and the maximum specific methanogenic activity of the sludge ranged between 27 and 93 days and 0.18 and 0.28 kg COD/(kg VS d).     

CFD simulation of mixing in egg-shaped anaerobic digesters

A computational fluid dynamics (CFD) model that characterizes mechanical draft tube mixing in egg-shaped anaerobic digesters was developed. Simulation of flow patterns were carried out with a propeller rotating from 400 to 750 rpm, assuming liquid manure to be Newtonian (water) and non-Newtonian fluids depending on the total solids (TS) concentration. Power number and flow number of the propeller in water mixing were validated against lab specifications and experimental data from a field test. The rotational direction and placement of the propeller were examined to identify the primary pumping mode and the optimum position of the propeller fixed inside the tube. Quantitative comparisons of two mixing methods and two digester shapes indicated that mechanical draft tube mixing is more efficient than external pumped recirculation, and that the egg shape provides for more efficient mixing than the cylindrical shape. Furthermore, scale-up rules for mixing in egg-shaped digesters were investigated.     

碱法麦草浆黑液处理系统的调试

对某造纸厂黑液处理系统的调试经验进行了总结。首先修正了原设计方案，提出酸析木素、中和、第一厌氧池、第二厌氧池相串连的处理流程，重点进行了第一厌氧池和第二厌氧池（UBF）的调试，探讨了挥发性脂肪酸（VFA）、重碳酸盐碱度、pH值及水力条件等工艺参数问题，并对存在的反应器污泥流失、重碳酸盐碱度与VFA浓度控制、水力条件的选择与控制等问题提出了解决办法。     

Temperature Effects On Pig Manure Under Low Level Batch Aeration

This project investigated the temperature effect on some chemical and biological characteristics of liquid swine manure under low level batch aeration conditions. An airflow rate of 0.129 L/min/L manure was used to aerate manure contained in reactors made of plexiglas tubes. Five temperatures, i.e. 5°C, 10°C, 15°C, 20°C, and 25°C, were examined. Data showed that manure pH would decrease with an increase in temperature. When temperature increased from 5°C to 25°C, the average oxidation-reduction potential decreased from +40 mV to m 60mV, resulting in a decrease in aerobic counts from 5.5 2 10 6 to 2.2 2 10 6 . This was accompanied by an increase in anaerobic bacterial counts (from 3.8 2 10 6 to 5.1 2 10 6 ). The increased anaerobic population produced more volatile fatty acids, leading to the decrease in pH. An inversely linear correlation was observed between pH and volatile fatty acids with a correlation coefficient of 0.8742. To prevent aerobic bacteria from decreasing and anaerobic bacteria from increasing, manure temperature should be kept under 15°C during aeration. To reduce odor generation potential (based on reduced VFA production), the oxidation-reduction potential should be maintained at +35 mV or higher.     

Effect of antimicrobial compounds tylosin and chlortetracycline during batch anaerobic swine manure digestion

Tylosin and chlortetracycline (CTC) are antimicrobial chemicals that are fed to >45% of the US swine herds at therapeutic and sub-therapeutic dosages to enhance growth rates and treat swine health problems. These compounds are poorly absorbed during digestion so that the bioactive compound or metabolites are excreted. This study investigated the degradation and stabilization of swine manure that contained no additives and compared the observed processes with those of manure containing either tylosin or CTC. The batch anaerobic incubation lasted 216 days. The breakdown of insoluble organic matter through anaerobic hydrolysis reactions was faster for manure containing CTC compared with tylosin or no-antimicrobial treatments. Volatile fatty acid (VFA) accumulation, including acetate, butyrate, and propionate, was greater for CTC-containing manure compared to tylosin and no-antimicrobial treatments. The relative abundance of two aceticlastic methanogens, Methanosaetaceae and Methanosarcinaceae spp., were less for CTC manure than manure with no-antimicrobial treatment. In addition, generation of methane and carbon dioxide was inhibited by 27.8% and 28.4%, respectively, due to the presence of CTC. Tylosin effects on manure degradation were limited, however the relative abundance of Methanosarcinaceae spp. was greater than found in the CTC or no-antimicrobial manures. These data suggest that acetate and other C-1 VFA compounds would be effectively utilized during methanogenesis in the presence of tylosin.     

Seepage Failure Mechanism of the Gouhou Rockfill Dam During Reservoir Water Infiltration

The catastrophic failure of the 71-m high Gouhou concrete-faced rockfill dam in Qinghai Province, China, has drawn many studies. This paper aims at providing new understanding on the modes and process of this failure, which could be applicable to similar dam failures. The geometrical and hydraulic criteria for internal erosion in rockfill materials are assessed. Unsaturated-saturated seepage theory is used to analyze the Gouhou dam since the rockfill materials of the dam were unsaturated before reservoir water infiltration. The water infiltration is simulated by several cases of transient seepage analyses. According to the study, a perched-water table formed in the dam when the reservoir water infiltrated into the rockfill from the top of the concrete face. The perched water spread nearly horizontally along stratifications in the rockfill and exited from the downstream slope at a high elevation as observed before the breach of the dam. The hydraulic gradient of the perched water table was the highest near the wetting front, which might provide necessary hydraulic conditions to trigger internal erosion and piping failure. Based on the geometrical conditions of the rockfill materials and the hydraulic conditions in the dam, the susceptibility of internal erosion is evaluated and the possible modes and process of seepage failure of the dam are described.     

低温条件下微生物对沉积物氮释放的影响研究

通过室内静态模拟实验,研究了沉积物中氮的释放特性。将反应器密封后自然达到厌氧状态,温度与水库底部相近（7～8℃）,进行未灭菌和灭菌两个系列对比试验,连续监测两个系列装置中NO3^-N、NO^2-N、NH4^＋-N、TN、DO和pH的变化,并对试验前后沉积物中的总氮含量进行测定。结果表明,未灭菌装置沉积物中总氮减少量明显多于灭菌装置,而上覆水中可监测总氮少于灭菌装置,说明在厌氧条件下氮元素会在微生物作用下从沉积物中释放出来,并通过反硝化和厌氧氨氧化等作用以气态形式释放出水体。试验前后对底泥表面的硝化、亚硝化、反硝化和氨化细菌的数量通过计数进行了比较,发现厌氧后反硝化细菌和氨化细菌明显增多,说明厌氧过程中对氮释放起主要作用的是反硝化细菌和氨化细菌。     

现代液压传动技术的新方向——纯水液压传动

本文简要回顾了液压传动工作介质的两次历史性变化及影响,论述了纯水液压传动技术的优势和面临的主要技术问题,介绍了国内外纯水液压传动技术的研究应用状况,并就发展我国纯水液压传动技术提出建议。     

Ecotoxicological assessment of doxycycline in aged pig manure using multispecies soil systems

This paper assesses the ecotoxicity of the antibiotic doxycycline in aged spiked pig manure using a multispecies soil system (MS 3) covering plants, earthworms and soil microorganisms. The study reproduced realistic exposure conditions, as well as higher exposure doses covering the uncertainty factors typically employed for covering interspecies variability. MS 3, consisting of columns of natural sieved soil assembled with earthworms and seeds from three plant species, were employed. Pig manure was spiked with doxycycline (75 or 7500 microg/ml), aged for 15 days under aerobic/anaerobic conditions and added on top of the soil columns (120 ml/column, equivalent to 220 kgN/ha). Water and doxycycline free manure were used as negative controls. Doxycycline (7500 microg/ml) solution was used as a positive control. No effects on plants or earthworms were observed. Significant effects on soil phosphatase activity, indicating effects on soil microorganisms, were observed at the highest exposure dose, affecting all soil layers in the doxycycline-solution-treated MS 3 (positive control) but only the top layer in the spiked pig manure system. Chemical analysis confirmed the different behavior of doxycycline in both systems (with and without manure) and those effects were observed in soil with measured concentrations over 1 mg/kg soil. The detection of doxycycline in leachates revealed a potential mobility. Leachate concentrations were similar for doxycycline solution and spiked manure treatments.     

Measurements of N2O and CH4 from the aerated composting of food waste

Emissions of N2O and CH4 from an aerated composting system were investigated using small-scale simulated reactors. The results show relatively high emissions of N2O at the beginning of composting, in proportion to the application amount of food waste. After 2 days, the N2O emission decreased to 0.53 ppmv on average, near to the background level in the atmosphere (0.45 ppmv). The addition of composted cattle manure increased N2O emissions not only at the beginning of composting, but also during the later period and resulted in two peak emission curves. Good correlation was observed between the N2O concentration at the air outlet and NO2- concentration in waste, suggesting a generation pathway for N2O from NO2- to N2O. Methane was only detected in treatments containing composted cattle manure. The high emission of methane illustrates the involvement of anoxic/anaerobic microorganisms with the addition of composted manure. The result suggests the existence of anoxic or anaerobic microsite inside the waste particles even though ventilation was employed during the composting process.     

Phosphorus losses in subsurface flow before and after manure application to intensively farmed land.

A study was conducted to examine the loss of P in subsurface flow from three cultivated soils of varying soil P concentrations. Measurements were made in flow waters from the soils before applying manure and then 3 weeks after sowing the soils to grass. An additional measurement of P in flow waters was made 1 year later. Dissolved reactive P (DRP) concentrations measured in flow water before (0.15-0.20 mg l(-1)) and after (0.39-0.51 mg l(-1)) manure application exceed current estimates of those required to promote surface water eutrophication (0.05 mg l(-1)). Concentrations of DRP1 year after manurial application increased compared to 3 weeks after application and was attributed to the slow movement of P down the cultivated soil. Concentrations of soil P were significantly increased down the soil profile and attributed to the P saturation of soils before manurial application. The results suggest that despite the establishment of fast growing grass, P concentrations would not be mitigated in the short-term (= 1 year), due to the large contribution of P in subsurface pathways.     

Phenols in anaerobic digestion processes and inhibition of ammonia oxidising bacteria (AOB) in soil

This study focuses on the presence of phenols in digestate from seven Swedish large-scale anaerobic digestion processes and their impact on the activity of ammonia oxidising bacteria (AOB) in soil. In addition, the importance of feedstock composition and phenol degradation capacity for the occurrence of phenols in the digestate was investigated in the same processes. The results revealed that the content of phenols in the digestate was related to the inhibition of the activity of AOB in soil (EC(50)=26 microg phenols g(-1) d.w. soil). In addition, five pure phenols (phenol, o-, p-, m-cresol and 4-ethylphenol) inhibited the AOB to a similar extent (EC(50)=43-110 microg g(-1) d.w. soil). The phenol content in the digestate was mainly dependent on the composition of the feedstock, but also to some extent by the degradation capacity in the anaerobic digestion process. Swine manure in the feedstock resulted in digestate containing higher amounts of phenols than digestate from reactors with less or no swine manure in the feedstock. The degradation capacity of phenol and p-cresol was studied in diluted small-scale batch cultures and revealed that anaerobic digestion at mesophilic temperatures generally exhibited a higher degradation capacity compared to digestion at thermophilic temperature. Although phenol, p-cresol and 4-ethylphenol were quickly degraded in soil, the phenols added with the digestate constitute an environmental risk according to the guideline values for contaminated soils set by the Swedish Environmental Protection Agency. In conclusion, the management of anaerobic digestion processes is of decisive importance for the production of digestate with low amounts of phenols, and thereby little risks for negative effects of the phenols on the soil ecosystem.     

水力负荷对湖滨带人工湿地除磷效果的影响

分析了湖滨带复合人工湿地的各单元在旱季和雨季的除磷效果。结果表明，在进水TP浓度较高时，沉淀池对TP的去除效果较明显，旱、雨季的不同水力负荷对处理效果几乎没有影响。雨季时潜流人工湿地内发生了不溶性磷的吸附和沉积，实现了对磷的去除；旱季时由于水力负荷极小，水体流动性差，系统内处于厌氧状态，出现了磷的释放。雨季时，表面流人工湿地对磷的去除效果没有沉淀池和潜流人工湿地的理想，旱季的低水力负荷对除磷效果没有显著的影响。     

Determination of penicillin G and its degradation products in a penicillin production wastewater treatment plant and the receiving river

To investigate the fate of penicillin G (PEN G) in the wastewater from a PEN G production facility and the receiving river, an analytical method was developed for the simultaneous detection of PEN G and five degradation products using liquid chromatography-electrospray ionization mass spectrometry (LC-ESI/MS). PEN G had already undergone transformation before entering into the wastewater treatment plant (WWTP), with concentrations of 153+/-4 microg/L in raw wastewater. Most of the PEN G could be eliminated following successive treatments of anaerobic, hydrolysis, and two aerobic units under a hydraulic residence time (HRT) of 30 h, and the final concentrations were 1.68+/-0.48 microg/L in treated water. In the receiving river, the concentration of PEN G decreased from 0.31+/-0.04 microg/L at the discharging point to under the detection limit (0.03 microg/L) at the last sampling site (about 30 km from the discharging point). The main PEN G degradation products in surface water were found to be penilloic acid, penicilloic acid and isopenillic acid, which occupied 65.8%, 20.4% and 12.9%, respectively, of the total concentration at the last site. This is the first study on the behaviors of PEN G and its main degradation products in wastewater treatment processes and the aquatic environment.     

Inactivation of Escherichia coli O157:H7 during thermophilic anaerobic digestion of manure from dairy cattle

Inactivation of the pathogenic Escherichia coli serotype O157:H7 and a non-pathogenic E. coli strain isolated from dairy cattle manure was evaluated with batch tests at 50 and 55 degrees C in biosolids from a thermophilic anaerobic digester treating the manure. Using differential-selective plating on sorbitol-MacConkey (SMAC) agar to quantify E. coli, the decline in concentrations of both the sorbitol-negative (putative E. coli O157:H7) and sorbitol-positive (putative non-pathogenic E. coli) organisms followed a model that assumed there was a heat-sensitive fraction and a heat-resistant fraction. Inactivation rates of the heat-sensitive fractions were similar for both colony types at each temperature, suggesting that wild-type E. coli can be used as an indicator of inactivation of serotype O157:H7. The decimal reduction time for the heat-sensitive fractions was in the order of 10min at 55 degrees C and ranged from approximately 1-3h at 50 degrees C. Concentrations of heat-resistant organisms at 55 degrees C were 1.4-1.7log(10)cfu/mL. Confirmatory analyses conducted on 30 randomly selected colonies of heat-resistant sorbitol-negative cells from treatment at 55 degrees C indicated that none were serotype O157:H7, nor were they E. coli. Similar analyses on 10 sorbitol-negative isolates from untreated manure indicated that none were serotype O157:H7, although 16S rRNA gene sequence analysis indicated that eight were E. coli or closely related enteric bacteria. These findings suggest that plating on differential-selective media to quantify E. coli, including serotype O157:H7, in effluent samples from thermophilic anaerobic digestion can lead to false positive results. Therefore, more specific methods should be used to evaluate the extent of thermal inactivation of both pathogenic and non-pathogenic E. coli in manure treatment systems.