寒冷地区城市污水处理厂污泥膨胀及其控制

结合大庆乘风庄污水厂运行 5年来两次污泥膨胀的实例 ,对活性污泥系统发生污泥膨胀的主要原因进行了分析 ,提出在寒冷地区活性污泥系统中 ,除低氧、低负荷外 ,低温也是造成膨胀的原因之一。对此提出采用减小曝气池污泥浓度或单池连续运行以提高负荷和鼓风机进风口空气加热提高曝气池水温的方法 ,可使膨胀得到有效控制。     

跨界融合子处理高浓度有机废水投资最小化模型研究

以跨界融合子基因工程菌处理高浓度有机废水为研究对象,建立了处理系统投资最小化数学模型及相应的约束方程,探讨该处理系统的优化设计问题。研究中以进水ＢＯＤ浓度Ｓ０、微生物浓度Ｘ和回流比Ｒ为初始控制变量,通过对跨界融合子降解豆制品废水实例验证,表明在给定的初始变量范围内有惟一的最优解,为处理工艺的合理设计提供了依据。     

Feedforward control for nitrogen removal in a pilot-scale anaerobic-anoxic-oxic plant for municipal wastewater treatment

To improve the efficiency of nitrogen removal with lower energy consumption, the study of feedforward control was carried out on a pilot-scale anaerobic-anoxic-oxic (AAO) plant for the treatment of municipal wastewater. The effluent qualities of the pilot plant under different control strategies were investigated. The results indicated that the change of external recycle was not a suitable approach to regulate the sludge concentration of plug-flow reactors; adjusting the aeration valve and dissolved oxygen set-point according to ammonia load could overcome the impact of influent fluctuation; and the denitrification potential could be estimated based on the transit time of anoxic zone and the relative content of carbon resource entering the anoxic zone. Simple feedforward control strategies for aeration and internal recycle were subsequently proposed and validated. The nitrogen removal was successfully improved in the pilot plant. The effluent total nitrogen had decreased by 29.9% and was steadily controlled below 15 mg·L^-1. Furthermore, approximately 38% of the energy for aeration had been saved.     

曝气强度对膜生物反应器运行特性的影响

以膜生物反应器（MBR）处理模拟生活废水为研究体系,考察曝气强度对系统污染物去除效果、脱氢酶活性、胞外聚合物（EPS）组分和含量、Zeta电位、污泥粒径及跨膜压差等的影响.结果表明,随着曝气强度降低,COD去除率变化不大,均大于94.0%,脱氢酶活性明显降低,VSS/SS比值下降;污泥LB-EPS增加,Zeta电位降低,污泥平均体积粒径减小,膜通量下降速率增大.曝气强度为800—400 L.m-.2h-1的条件下,曝气产生的水力剪切力不是影响污泥粒径大小的主导因素,污泥Zeta电位则起着决定作用,但水力剪切力有利于缓解膜污染.     

Classification of contaminants and treatability evaluation of domestic wastewater

Long-term sampling and analysis were conducted in a domestic wastewater treatment plant for the investigation on the characteristics of the representative contaminants in raw sewage such as SS, COD, BOD₅, TP, and TN. All these constituents were classified into dissolved and suspended groups by using a 0.45-μm membrane filter, and the concentration of each constituent in each group was analyzed. As a result, almost 100% of the SS was found to be suspended matter, as well as about 65% of COD, 60% of BOD₅, 50% of P, and 20% of N. All these could be easily removed by sedimentation or coagulation/sedimentation. A treatability evaluation diagram was proposed for a rational selection of wastewater treatment process in accordance with raw water quality.     

Duckweed: an effective tool for phyto-remediation

Effective wastewater treatment through conventional methods that rely on heavy aeration are expensive to install and operate. Duckweed is capable of recovering or extracting nutrients or pollutants and is an excellent candidate for bio-remediation of wastewaters. Such plants grow very fast, utilizing wastewater nutrients and also yield cost effective protein-rich biomass as a by-product. Duckweeds being tiny surface-floating plants are easy to harvest and have an appreciable amount of protein (15%–45% dry mass basis) and a lower fiber (7%–14% dry mass basis) content. Besides nutrient extraction, duckweeds has been found to reduce total suspended solids, biochemical oxygen demand (BOD), and chemical oxygen demand in wastewater significantly. Depending on the initial concentrations of nutrients, duckweed-covered systems can remove nitrate (NO₃^?) at daily rates of 120–590 mg NO₃^? m^?2 (73%–97% of initial concentration) and phosphate (PO₄^?) at 14–74 mg PO₄^? m^?2 (63%–99% of initial concentration). Removal efficiencies within 3 days of 96% and 99% have been reported for BOD and ammonia (NH₃). Besides several genera of duckweeds (Spirodela, Lemna, Wolffia), other surface-floating aquatic plants like water hyacinth (Eichhornia) are well known for their phyto-remediation qualities.     

Effect of mercury on the survival,respiration, and growth of postlarval white shrimp,Penaeus setiferus

The results of toxicity experiments have shown that a level of 17 ppb ionic mercury is acutely toxic (96-h LC₅₀) to postlarval white shrimp (Penaeus setiferus). In addition, the size of the shrimp, within the range tested (7 to 35 mm) did not significantly alter the toxicity values of mercury to this species. Fifty-seven days pre-exposure to low levels of mercury (0.5 and 1.0 ppb) had no effect on the acute toxicity (96-h LC₅₀) of mercury to the shrimp. The effect of chronic exposure to low levels of mercury on the respiratory rate, growth, and molting rate of postlarval P. setiferus was studied, and the results showed that 60 days exposure to 0.5 and 1.0 ppb mercury did not significantly affect any of these parameters for the postlarvae.     

Photocatalytic treatment of dimethoate by solar photocatalysis at pilot plant scale

Titanium dioxide photocatalysis, using 200 mgl⁻¹ of TiO₂, and photo-Fenton, using 20 mg l⁻¹ of iron, were applied to the treatment of dimethoate dissolved in water at 50 mg l⁻¹. A heterogeneous photocatalysis test was performed in a 35-l solar pilot plant with Compound Parabolic Collectors (CPCs) under natural illumination. A homogeneous photocatalysis test was performed in a different solar pilot plant with four CPC units and a total volume of 75 l. In this work total disappearance of dimethoate and 90% of mineralization were attained in both solar treatments. Treatment time, hydrogen peroxide consumption and ferric phosphate precipitation during photo-Fenton treatment were discussed. An erratum to this article can be found at     

Principal Biogeochemical Factors Affecting the Speciation And Transport of Mercury through the terrestrial environment

It is increasingly becoming known that mercury transport and speciation in the terrestrial environment play major roles in methyl-mercury bioaccumulation potential in surface water. This review discusses the principal biogeochemical reactions affecting the transport and speciation of mercury in the terrestrial watershed. The issues presented are mercury-ligand formation, mercury adsorption/desorption, and elemental mercury reduction and volatilization. In terrestrial environments, OH^–, Cl^– and S^– ions have the largest influence on ligand formation. Under oxidized surface soil conditions Hg(OH)₂, HgCl₂, HgOH⁺, HgS, and Hg⁰ are the predominant inorganic mercury forms. In reduced environments, common mercury forms are HgSH⁺, HgOHSH, and HgClSH. Many of these mercury forms are further bound to organic and inorganic ligands. Mercury adsorption to mineral and organic surfaces is mainly dictated by two factors: pH and dissolved ions. An increase in Cl^– concentration and a decrease in pH can, together or separately, decrease mercury adsorption. Clay and organic soils have the highest capability of adsorbing mercury. Important parameters that increase abiotic inorganic mercury reduction are availability of electron donors, low redox potential, and sunlight intensity. Primary factors that increase volatilization are soil permeability and temperature. A decrease in mercury adsorption and an increase in soil moisture will also increase volatilization. The effect of climate on biogeochemical reactions in the terrestrial watershed indicates mercury speciation and transport to receiving water will vary on a regional basis.     

招远市区土壤及常见绿化植物汞污染特征

为查明长期黄金开采冶炼对城市汞污染的影响,以"金都"招远为研究对象,于2011年4月,采集了招远市区常见绿化植物柏树、落叶松、冬青的茎叶样品30份,并同步采集相应表层土壤样品34份。采用冷原子吸收法测定样品总汞含量,分析了土壤的理化性质。结果表明,招远市区表层土壤中汞含量范围为0.002~0.815 mg·kg-1,平均值为0.149 mg·kg-1。土壤汞含量与有机质呈极显著正相关,与p H、粗颗粒比例呈显著正相关关系,而与阳离子交换量、黏粒比例呈显著负相关。不同城市区域相比,处于金矿区污染源下风向、且与矿区距离较近的梦芝区土壤汞含量要显著高于其它区域。常见绿化植物茎叶汞含量范围为0.021~0.782 mg·kg-1,不同植物中的汞含量没有显著差异,但同种植物中茎、叶中汞含量存在极显著正相关。植物中的汞在各城市区域没有显著差异,与土壤汞含量也不存在显著相关性。研究结果显示,招远市区土壤和植物受周边金矿开采和黄金冶炼的影响,存在一定程度汞污染。     

Acute toxicity of potassium permanganate to Caspian roach Rutilus rutilus caspicus in two size classes and under different aeration conditions

Caspian roach, Rutilus rutilus caspicus, might experience potassium permanganate (PM) toxicity, because it is common and widely used disinfectant in fish rearing and propagation centers in Iran. Thus, acute toxicity (24-h-LC₅₀) of PM was determined on Caspian roach in two size classes (small and large groups), under aerated and non-aerated conditions, using static non-renewal system. 24-h-LC₅₀ for PM in Caspian roach was 3.2, 3, 3.2, and 2.8?mg?L^?1 in large-aerated, large-non-aerated, small-aerated, and small-non-aerated groups, respectively. Results indicated that aeration was led to decrease in PM toxicity, regardless of size class. However, large fish showed more tolerance to PM toxicity compared to small ones, under non-aerated condition. It is concluded that aeration could decrease the toxicity of PM that seems to be due to the increase in PM degradation, derived from increase in water turbulence. It is suggested that 96-h-LC₅₀ may be more suitable to determine the effects of fish size on PM toxicity than 24-h-LC₅₀.     

Removal of nitrogen and phosphorus from textile wastewater by soilless culture of Lolium multiflorum

A technique of soilless culture for removal of total nitrogen (TN) and total phosphorus (TP) from textile wastewater using Lolium multiflorum was conducted in this research. The TN concentration decreased from 50.72 mg/L to 24.64–27.89 mg/L and TP decreased from 6.9 mg/L to 3.7–4.1 mg/L in the experimental tank with the size of 4.7 m x 1.2 m x 0.75 m. The results suggested that L. multiflorum could absorb a large amount of N and P elements from the wastewater. This technique of soilless culture has many advantages such as simple equipment, low cost, easy operation, low energy consumption, convenient management and flexible disposition.     

Green synthesis and characterization of metal ions-mixed titania for application in dye-sensitized solar cells

Abstract

The objective of the present study is to synthesize various metal ions mixed TiO₂ nanoparticles using a continuous hydrothermal synthesis pilot reactor for dye-sensitized solar cells (DSCs). In the pilot plant, aqueous solutions of the metal salts are mixed with a flow of supercritical water (450?°C and 24.1?MPa) in a confined jet mixer for continuous synthesis of metal ions-mixed nano-titania. Characterization of the particles was made using Brunauer–Emmett–Teller technique for specific surface area, powder X-ray diffraction analysis and transmission electron microscopy for identification and crystallite size, X-ray photoelectron spectroscopy for surface analysis and infrared spectroscopy for distinct group identification. Following the already existing procedures and using the titanates synthesized, dye-sensitized cells of 1?cm² area were assembled and their photovoltaic parameters were evaluated under standard test conditions. The power conversion efficiencies (η %) for 40?mol % Zn²⁺, 5?mol % Zr⁴⁺ and 10?mol % Zn⁴⁺ titania were obtained to be 4.8, 4.95 and 4.9, respectively. The promising efficiency results from a greener and large-scale production of nano-titania is a step forward towards commercializing DSC technology.     

Performance of bioferric-submerged membrane bioreactor for dyeing wastewater treatment

Adding iron salt or iron hydroxide to sludgemixed liquor in an aeration tank of a conventional activated sludge processes (bioferric process) can simultaneously improve the sludge’s filterability and enhance the system’s treatment capacity. In view of this, Fe(OH)₃ was added to a submerged membrane bioreactor (SMBR) to enhance the removal efficiency and to mitigate membrane fouling. Bioferric process and SMBR were combined to create a novel process called Bioferric-SMBR. A side-by-side comparison study of Bioferric-SMBR and common SMBR dealing with dyeing wastewater was carried out. Bioferric-SMBR showed potential superiority, which could enhance removal efficiency, reduce membrane fouling and improve sludge characteristic. When volumetric loading rate was 25% higher than that of common SMBR, the removal efficiencies of Bioferric-SMBR on COD, dye, and NH₄ ⁺-N were 1.0%, 9.5%, and 5.2% higher than that of common SMBR, respectively. The trans-membrane pressure of Bioferric-SMBR was only 36% of that in common SMBR while its membrane flux was 25% higher than that of common SMBR. The stable running period in Bioferric-SMBR was 2.5 times of that in common SMBR when there was no surplus sludge discharged. The mixed liquor suspended solids concentration of Bioferric-SMBR was higher than that of common SMBR with more diversified kinds of microorganisms such as protozoans and metazoans. The mean particle diameter and specific oxygen uptake rate of Bioferric-SMBR were 3.10 and 1.23 times the common SMBR, respectively.     

南方某铀矿山废水对生物的急性毒性研究

为探明铀矿山对周围环境的联合毒性机制,本研究以常用生物毒性测试菌种——发光细菌青海弧菌Q67和费氏弧菌以及禾花鲤为受试生物代表,实地采集的铀矿山废水为目标废水,研究铀矿山废水对发光细菌和禾花鲤的急性毒性。实验结果表明,矿山废水对3种生物的急性毒性存在显著的剂量-效应关系,毒性效应浓度EC_(50)(LC50)的大小顺序为禾花鲤幼鱼费氏弧菌青海弧菌Q67,Pb~(2+)/U~(6+)浓度分别为6.052/3.026 mg·L~(-1)、2.284/1.142 mg·L~(-1)、1.339/0.669 mg·L~(-1),均可有效指示矿山废水的毒性水平,其中发光细菌更为灵敏、快速;且青海弧菌Q67的EC_(50)值最小,灵敏度最高,可作为表征矿山废水毒性风险的首选指示物。研究结果能够为放射性矿区废水生态风险预警、安全处理处置、水质基准制定及流域水环境管理提供依据。     

城市污水厂氨气的来源及排放因子研究

通过对城市污水处理厂进行现场调查和分析,选取广州市猎德污水处理厂的格栅、沉砂池、A-B工艺的曝气池、组合交替式(unitank)生化池、污泥浓缩池及脱水机房采集气样,同时在A-B工艺的曝气池、unitank生化池及A-B工艺的沉淀池采集水样,采用模拟实验测试这些污水处理单元的氨挥发速率,并结合理论计算,研究氨气的来源和排放因子.结果表明,A-B工艺的曝气池和unitank工艺的生化池为城市污水处理厂的主要氨排放源.城市污水处理厂污水的氨气平均挥发速率为21.06μg.m-.2s-1,在此基础上计算出其氨气平均排放因子为0.28 g.m-3,其中A-B工艺曝气池的氨排放因子较高,为0.205 g.m-3;unitank生化池的氨排放因子为0.033 g.m-3;A-B工艺沉淀池的氨排放因子较低,为0.0085 g.m-3.     

中国地区大气汞的数值模拟研究

结合中国地区的汞排放,利用引入大气汞化学反应机制和干沉降模型的区域大气环境模式系统(Regional Atmospheric Environment Model System,Reg AEMS),对中国地区大气汞化物浓度和干沉降通量的时空分布特征进行模拟研究。研究结果表明,中国地区年均气态零价汞Hg0、氧化汞Hg O、氢氧化汞Hg(OH)2、氯化汞Hg Cl2和颗粒态汞HgP的沉降量分布类似。除西部、西北部地区Hg0的浓度较低外(0.5 ng·m-3),其他地区均高于全球背景浓度。各类汞化物浓度的季节变化明显,8月最低,2、3月最高。一次汞源区附近汞浓度随高度递减,在离源较远的地区,高层汞浓度较高。气态零价汞的干沉降速度的季节变化最明显,其干沉降通量在夏季最高。模拟区域中气态零价汞、氧化汞和颗粒态汞的年干沉降量分别为163.9、7.43和32.2 t。     

缺氧—SBR工艺处理焦化废水

对焦化废水进行曝气吹脱,10h氨氮去除率达73．7％,用缺氧－SBR工艺处理焦化废水,进水浓度为COD1474mg/L,NH3-N826.8mg/L时,缺氧SRT10h,SBR曝气10h,沉降2h,出水COD186mg/L,NH3-N290.5mg/L,去除率分别达到87．83％,64．9％。