Biodegradation of phenol at low temperature using two-phase partitioning bioreactors.

Two-phase partitioning bioreactors offer many advantages for the removal of toxic pollutants. In particular, such systems can be loaded with very large quantities of pollutants without risks of microbial inhibition, they are self-regulated and they prevent the risks of hazardous pollutant volatilisation during aerobic treatment. However, their potential has never been tested at low temperatures. Phenol biodegradation by a cold adapted Pseudomonas strain was therefore tested at 14 or 4 degrees C using 2-undecanone, diethyl sebacate or 2-decanone as organic phases in a two-phase partitioning bioreactor. The three solvents were biocompatible at 14 degrees C but evidence was found that diethyl sebacate was biodegraded by the bacteria and this solvent was not tested further. Although only 2-decanone was suitable at 4 degrees C, phenol biodegradation was more efficient in 2-undecanone at 14 degrees C, reaching a maximum volumetric rate (based on the volume of aqueous phase) of approximately 1.94 g/L.day after 47 h of cultivation. In 2-decanone at 14 degrees C, evidence was found that phenol degradation was limited by the release of biosurfactants, which increased the solubility and toxicity of the solvent in the aqueous phase inhibiting microbial activity. This study therefore shows that pollutant removal at low temperature is feasible but that the production of biosurfactants can have a negative impact on the process and must be taken into consideration when selecting the organic solvent. Future work should therefore focus on the selection of solvents suitable for use at temperatures below 14 degrees C.     

Anaerobic digestion of gelatinous water at laboratory and pilot scale and nitrogen inhibition.

The anaerobic digestion of the liquid residue (gelatinous water) coming from the production of fat from animal residue, was studied at laboratory and pilot scale. Biodegradability (>98%) and biogas potential (675 mL of biogas/g of COD(applied)) of this wastewater are very high. However, due to the high content on nitrogen, an inhibition of the anaerobic activity was observed for quite low concentrations of N-NH(3). Dilution of the wastewater and pH regulation in the reactor around 7.3 are the 2 solutions which were investigated to overcome the nitrogen inhibition at industrial scale. These two solutions were validated at laboratory scale in an anaerobic SBR and then onsite at pilot scale in a continuous reactor. A stable anaerobic digestion was observed in both reactors showing that no nitrogen inhibition was obtained when N-NH(3) concentration in the reactor was kept low.     

微生物电解池降解乙酸钠的运行条件优化研究

采用微生物电解池(microbial electrolysis cell,MEC)技术,通过正交试验考察了Na Ac浓度、缓冲液浓度、外加电压和搅拌速度等因素对MEC降解水中乙酸钠效果以及反应器产气效果的影响。试验结果的极差分析表明,各因素对乙酸钠降解效果和产气效果均呈正相关;通过方差分析得出各影响因素对乙酸钠降解性能影响的大小顺序依次为:Na Ac浓度、搅拌速度、外加电压和缓冲液浓度;对产气性能影响的大小顺序依次为:外加电压、缓冲液浓度、Na Ac浓度和搅拌速度。在Na Ac浓度1.5 g/L、缓冲液浓度50 mmol/L、外加电压0.9 V和搅拌速度1 000 r/min的最优条件下,MEC反应器对水中乙酸钠的去除率为98.2%、产气速率为0.148 m3/(m3·d)。研究表明,可以从处理效果或经济性角度优化MEC反应器运行条件,如适当增加搅拌速度、外加电压和缓冲液浓度,提升Na Ac去除率;适当减小搅拌速度可以获得相似的产气速率,且降低能耗。     

Evaluation and thermodynamic calculation of ureolytic magnesium ammonium phosphate precipitation from UASB effluent at pilot scale

The removal of phosphate as magnesium ammonium phosphate (MAP, struvite) has gained a lot of attention. A novel approach using ureolytic MAP crystallization (pH increase by means of bacterial ureases) has been tested on the anaerobic effluent of a potato processing company in a pilot plant and compared with NuReSys(?) technology (pH increase by means of NaOH). The pilot plant showed a high phosphate removal efficiency of 83 ± 7%, resulting in a final effluent concentration of 13 ± 7 mg · L(-1) PO(4)-P. Calculating the evolution of the saturation index (SI) as a function of the remaining concentrations of Mg(2+), PO(4)-P and NH(4)(+) during precipitation in a batch reactor, resulted in a good estimation of the effluent PO(4)-P concentration of the pilot plant, operating under continuous mode. X-ray diffraction (XRD) analyses confirmed the presence of struvite in the small single crystals observed during experiments. The operational cost for the ureolytic MAP crystallization treating high phosphate concentrations (e.g. 100 mg · L(-1) PO(4)-P) was calculated as 3.9 € kg(-1) P(removed). This work shows that the ureolytic MAP crystallization, in combination with an autotrophic nitrogen removal process, is competitive with the NuReSys(?) technology in terms of operational cost and removal efficiency but further research is necessary to obtain larger crystals.     

微污染水中苯酚光催化降解的健康风险评价

利用微污染水中苯酚光催化降解的试验统计结果进行了环境健康风险评价.结果表明,在苯酚初始浓度为0.004～0.05 mg/L的试验条件下,反应30～85 min时,苯酚含量降至0.002mg/L的安全标准值(健康危害风险为8.16×10-12a-1),但中间产物邻苯二酚、对苯二酚的最大健康危害风险分别高达2.45×10-11a-1和2.04×10-11a-1,且风险度随苯酚初始浓度的增大而增强.说明利用光催化降解微污染水中苯酚的健康安全初始浓度小于0.01 mg/L,安全反应时间大于85 min.     

Kinetics of cometabolic degradation of 2-chlorophenol and phenol by Pseudomonas putida

In order to address the complex cometabolic degradation of toxic compounds,batch experiments on the biodegradation of 2-chlorophenol (2-CP) and phenol by Pseudomonas putida were carried out.The experimental results show that 2-CP has an inhibitory effect on cell growth and phenol degradation,which demonstrates that the interaction between substrates affects cell growth and substrate degradation.A kinetic model of cell growth and substrate transformation was also developed.The square of the correlation coefficient from the experiment was 0.97,indicating that this model properly simulates the cometabolic degradation of 2-CP and phenol.     

基于遗传算法的田间尺度土壤水力参数与溶质运移参数优化

合理确定田间尺度土壤水力参数和溶质运移参数是保证农田土壤水盐动态模拟正确性的重要前提。本文开展了基于遗传算法(Genetic Algorithms,GA)与农田水文模型SWAP(Soil-Water-Atmosphere-Plant)耦合进行土壤水力参数和溶质运移参数优化的方法研究。在已有GA基础上引入了子体优生策略,并以完全嵌入方式耦合GA与SWAP模型。采用河套灌区曙光实验站的土壤剖面分层含水率(θi)和溶液浓度(cmli)、表土含水率(θsur)、实际腾发量(ETa)等观测资料,开展了田间尺度土壤水力参数和溶质运移参数优化的数值试验与相应分析。结果表明:(1)采用土壤分层信息(θi和cmli)作为观测数据,GA参数优化效果很好;(2)仅采用ETa作观测数据时,参数优化效果相对欠佳,需慎重使用,而结合ETa与θsur后可提高优化精度;(3)引入子体优生策略可提高GA的参数优化效率和精度。综上,结合GA与SWAP模型是优化田间尺度土壤水力参数和溶质运移参数的一种实用方法。     

The distribution and movement of polyphosphate and associated cations in sludges from ndebpr plants in different configurations at pilot scale

A gradual change in the mode and location of intracellular storage of polyphosphate was observed during a long-term pilot-scale evaluation of operating efficiency of a number of EBPR process configurations used for model calibration. The location of intracellular polyphosphate, (defined by the extraction procedure), was seen to change from a long chain form to a lower molecular weight or short chain form under the influence of nitrate return to the anaerobic zone, which was related to a number of factors including influent character (TKN/COD, influent RBCOD) and process configuration, however during trials with high TKN/COD (⩾0.13) the storage of polyphosphate was observed to exist predominately in the short chain form. The behaviour of EBPR biomass in a sequencing batch reactor demonstrated mobilisation and storage of polyphosphate from only the low MW form.     

大型污泥厌氧消化系统的启动与运行调控

北京小红门污水处理厂建有5座单体容积12 300m3的卵形污泥厌氧消化设施,设计沼气产量30 000m3/d。以运行数据为基础,总结了大型厌氧消化系统的启动、运行与调控经验,分析大型污泥厌氧消化系统的启动与运行特点。提出建议与措施,并提出系统优化的具体目标。     

Ti/SnO_2电极在苯酚废水降解中的应用

采用热分解法制备了Ti/SnO_2电极,以苯酚为目标污染物,研究苯酚废水在电极上电解的最佳条件、电解一定时间后的电压以及电极的寿命。结果表明,在电流密度为190 A/m2和pH值为2的条件下,苯酚溶液初始质量浓度为70 mg/L,电解350 min后,苯酚和COD的降解效率最高,分别为96.80%和40%,苯酚被降解为中间产物,没有被彻底矿化为CO_2和H_2O,此时的电压为8 V。在25℃,0.5 mol/L的H_2SO_4水溶液中、恒流500 A/m2条件下对电极的寿命测试,电极寿命仅仅为8 h,寿命较短。     

利用外加剂提高混凝土抗硫酸盐侵蚀的尝试

1问题的提出 地处浙江西部的龙游县南部山区是富含黄铁矿的区域，龙游沐尘水库工程正处在这一区域。受黄铁矿外围影响，工程所处区域地层岩石结构面上均有不同程度的黄铁矿分布，局部黄铁矿发育，特别是通过大坝趾板F2和F3断层，实为黄铁矿矿脉。施工过程中采用深挖后混凝土回填的方法进行处理。由于黄铁矿的存在，混凝土必须具有较强的抗硫酸盐侵蚀的特性。     

以冲淤控制为目标的水库优化调度

以各时段下泄流量为决策变量,将遗传算法与一维水沙模型结合,建立了以冲淤控制为目标的水库优化调度模型.探讨了如何选择合适的遗传操作维持种群的多样性,保持遗传算法从可行域和非可行域同时搜索的能力,构造了一种基于高斯分布的动态变异算子,用于处理非线性约束条件.通过算例说明了该模型的有效性和灵活性,以及相对于微分动态规划法的优势.     

地表漫流系统处理污染河水工程设计探讨

通过地表漫流系统中试工程应用于新沂河污染河水的生态治理试验研究,认为应将草的稠密度作为最基本的植物选择原则之一;以氨氮为主要去除对象的处理系统设计水力负荷可采用8~10cm/d;沿坡面宽度方向将坡面划分成宽2~2.5m的场地,用垄分隔,不仅可以提高坡面平整度,而且有利于缩短坡面长度,将其控制在30m左右;为便于调节,平顶堰槽式表面布水系统的堰板设计宽度不宜大于2m;投配时间控制在10~12h/d,投配周期为5~6d,能够防止坡面堵塞,还有利于草的生长。     

Enhanced sludge conditioning by enzyme pre-treatment: comparison of laboratory and pilot scale dewatering results.

The effect of enzyme pre-treatment on dewaterability of anaerobically digested sludge was investigated at both laboratory and pilot scale. Our results revealed a significant increase in cake solid content (27% cake solids compared to 18% without enzyme pre-treatment), using an enzyme dose of only 20 mg/L. In order to assess practical application, enzyme pre-treatment was applied at the Wilmington, Delaware (U.S.) wastewater treatment plant, using a pilot-scale centrifuge. However, the efficiency reached in laboratory scale could not be obtained in pilot scale, where the final cake solids content did not exceed 20%. Centrifuge and belt filter press (simulated by Crown Press) dewatering were compared in terms of the process efficiencies in the absence and presence of enzyme pre-treatment. Possible factors that might cause the differences were tested by experimental and statistical comparisons. Results indicated that the higher shear applied in centrifugation is responsible for the lack of improved cake solids. The network strength of sludge determined by rheological measurements revealed that enzymatic treatment weakens the gel structure of the sludge floc through the hydrolysis of extracellular polymeric substances; this allows improved dewatering by filtration processes, but leads to floc deterioration when subjected to high shear during centrifugation.     

Modification of submerged membrane bioreactors (MBRS) by inserting baffles: pilot scale study.

Submerged membrane bioreactors (MBRs) have been gaining in popularity in various types of wastewater treatment. One drawback of submerged MBRs is difficulty in removing nitrogen as they are accompanied with intensive aeration inside the reactor and therefore principally operated under aerobic conditions. In order to address this problem, a simple modification for submerged MBRs, insertion of baffles to create alternative aerobic/anoxic conditions, was proposed. In this study, the performance of the proposed baffled membrane bioreactor (BMBR) was investigated based on a pilot-scale experiment using a real municipal wastewater. With appropriate operating conditions, the BMBR could remove more than 70% of total nitrogen contained in the feed water without any external carbon source. The BMBR demonstrated a good treatment performance in terms of TOC and phosphorus removal as well. Increase of trans-membrane pressure difference was subtle, which might be attributed to the alternative creation of aerobic/anoxic conditions.     

Modelling of long-term simultaneous nitrification and denitrification (SNDN) performance of a pilot scale membrane bioreactor

Nutrient removal capability of the MBR process has attracted more attention than organics removal in the past few years. Apart from the conventional schemes for nitrogen removal in MBR process, simultaneous nitrification-denitrification (SNDN) requires the most attention for further research. In order to fully understand the fundemantals and mechanism of SNDN in MBRs, a pilot plant was set up. A mathematical model was adopted for investigation and calibration against the observed values. This paper reports a study focusing on evaluating major mechanisms that govern nitrogen removal from domestic wastewater in membrane bioreactors. Two items need to be emphasized in this evaluation: (i) an MBR is basically regarded as an activated sludge process-a suspended growth bioreactor with total biomass recycle and substantially higher biomass concentration; (ii) in this context an AS model, namely ASM1R modified for endogenous respiration, is used for dynamic modelling and calibration of experimental results. The impact of diffusion through biomass which obviously exerts a significant effect on system performance and denitrification is evaluated with success using the adopted model by means of switch functions that regulate nitrification-denitrification with respect to dissolved oxygen concentration in the bulk liquid.     

UNITANK系统生物——化学联合除磷工艺中试研究

以诸暨市水样进行的中试研究表明,采用生物—化学联合除磷工艺对UNITANK系统进行常规改进得不偿失。但可以考虑采用生物—化学联合除磷工艺作为UNITANK系统应对TP冲击负荷的应急处理工艺。     

Optimization of the removal of phenol by soybean seed coats using response surface methodology

Peroxidase from soybean seed coats catalyzes the oxidation and polymerization of aromatic compounds in the presence of H(2)O(2). The present study investigated the optimization of the phenol removal from wastewaters by direct using of soybean seed coats that can be extended to large scale, as a cost-effective option in comparison to pure enzyme. A central composite design was used to evaluate the effect of the following factors on the phenol removal: H(2)O(2) concentration (1-40 mmol/L), polyethylene glycol (PEG) concentration (0-1 g/L) and the amount of soybean seed coats (10-60 g/L). The results showed that PEG concentration had no significant effect on phenol conversion. Additionally, by increasing the amount of soybean seed coats, the extent of phenol conversion was increased and a higher concentration of H(2)O(2) was required to reach the maximum phenol conversion. Under optimum conditions for 1 mmol/L initial phenol, 50 g/L soybean seed coats, 14 mmol/L H(2)O(2) and 0.8 g/L PEG, the phenol conversion after 30 min was 78%. After 2 h, the catalyzed process was capable of achieving 90-92% removal of the total phenol from synthetic wastewater. A cubic model was also developed that was verified by predicting some independent experimental results.     

Winter operation of spillway structures at hydroelectric power plants

Basic problems of reliability assurance at hydroelectric power plants under the winter conditions prevalent in Siberia, the Far East, and mountainous region are touched upon. Data presented in the paper are based on results of scientific observations of spillway operation at various hydroprojects during the winter. Major attention is focused on analysis of the winter operation of the spillway at the Sayano-Shushenskaya HPP. Basic positions with regard to evaluation of the possibility and assurance of the operation of spillway structures during winter should be considered for hydroprojects already built, and those under design.