过氧化钙释氧过程中碱度调控方法的研究

当采用过氧化物作为原位生物修复污染地下水的释氧剂时,以微生物培养驯化过程中所需的营养组分(NH4)2SO4和KH2PO4作为pH调节剂,同时以电气石和现场土壤的调节、缓冲作用作为辅助手段,对过氧化钙(CaO2)释氧过程中的碱度调控方法进行了研究.结果表明,(NH4)2SO4和KH2PO4的协同作用可将溶液pH值由12.1降至适宜微生物生长的6.5～8.5;电气石和现场土壤可持续稳定地降低溶液的pH值,在一定条件下可减少pH调节剂的使用量,避免地下水的二次污染.     

投加菌剂对清淤底泥好氧堆肥效果的强化作用

为解决清淤底泥好氧堆肥存在有机质含量低、高温阶段升温不足的问题,从自然堆肥过程中分离提取优势菌株,制成微生物复合菌剂,通过投加菌剂强化清淤底泥好氧堆肥效果。结果表明,与对照组相比,试验组堆体温度升高快,高温阶段持续时间长,高于55℃的时间可达9 d,满足《粪便无害化卫生要求》(GB 7959—2012)的规定。菌剂投加促进了堆料腐熟,种子发芽指数从86.9%提高到96.3%。试验组和对照组的C/N值分别降低了22.0%和14.3%,可见投加菌剂还可以提高堆料保氮效果。     

矿井水处理聚合氯化铝残留物对超滤膜污染的影响

针对矿井水混凝处理过程中投加的聚合氯化铝(PAC)残留物对超滤膜的污堵问题,采用在聚偏氟乙烯(PVDF)超滤膜前投加不同量的PAC对矿井水进行混凝和超滤试验,考察PAC不同投加量下浊度、污染指数(SDI)、残留铝含量、跨膜压差(TMP)和归一化膜比通量(NSF)间的相互关系及对超滤膜的影响。结果表明:当PAC投加量为35~40 mg/L时,混凝上清液中SDI最小为5. 3,残留铝含量约为0. 16~0. 23 mg/L,浊度约为6. 0~8. 0 NTU。跨膜压差随着PAC投加量、残留铝含量和pH值的增加而上升。当PAC投加量为40 mg/L、残留铝含量为0. 18 mg/L、pH值为4. 2~5. 2时,跨膜压差(TMP)最小值约为64. 8~68. 4 kPa。水中残留铝存在形态在不同pH值条件下可相互转化,其聚合态和絮凝体粒径又影响着超滤膜污染,酸性条件(pH值为4. 2~5. 2)下更有助于减少残留铝对超滤膜的污染。     

养鱼池底泥耗氧速率的研究

本文用新的底泥耗氧速率的测定方法,探讨了此方法的精密度和水温及底泥中有机质对鱼池底泥耗氧速率的影响。用此方法研究鱼池底泥耗氧速率.发现在培育期内北力养鱼池底泥耗氧速率一般为0.4～1.6gO_2·m^(-2)·d(-2)·d^(-1),鱼池底泥耗氧速率占鱼池总耗氧的比率在5％～20％之间,还对新老池底泥耗氧速率进行了比较。     

厌氧/好氧一体式折流板反应器处理淀粉废水

采用三级厌氧/好氧一体式折流板生物反应器处理马铃薯淀粉废水,并在好氧室添加多孔炉渣作为填料,考察了该工艺的处理效能。结果表明,在运行温度为25~35℃、pH值为5.0~8.5的条件下,当废水的COD为1 400~3 000 mg/L、氨氮为15.0~24.0 mg/L时,系统的出水COD≤200 mg/L、氨氮为10.8 mg/L,对COD和氨氮的去除率分别为(90%~96%)、(42.7%~53.0%);多孔炉渣填料的投加可提高好氧室的处理效果。     

铝盐强化混凝去除水中腐殖酸

研究了原水中腐殖酸含量、温度、pH值、混凝剂投加量等因素对强化混凝去除水中腐殖酸的影响;实验结果表明,在20℃,原水中的腐殖酸含量小于10mg/L,pH值为5.5～6.0,AlCl3的投加量为0.5×10-3mol/L的条件下,原水剩余的腐殖酸可以控制在0.02cm-1以下;加入0.05mol/L的NaCl对腐殖酸的去除有较好的促进作用。     

增效结团流化床处理低浊水的启动试验

将增效结团流化床应用于低浊水处理,并探讨了其启动条件。研究确定启动增效结团流化床装置需投加pH值为7.31,Zeta电位为-1.28mV的底泥约624g;同时得出在进水流量Q=2040～2720L/h时,最佳的启动条件为:PAC投加量3.0～3.2mg/L,PAM投加量0.42mg/L,污泥回流比4.8%左右。     

治理感潮河道黑臭的底泥原位修复技术研究

选择典型的珠江流域重污染感潮河道——广州市荔湾区郭村涌为研究对象,结合河道感潮特性,在退潮后的最低水位时采用底泥曝气并投加TRSS稳定剂来消除河道黑臭,以利于河道生态系统的恢复。研究结果表明：底泥曝气可有效氧化底泥中的硫化物,运行一个月后对其去除率达到了86.3%～92.1%,臭味基本被消除;底泥经投加TRSS进行稳定化处理后,Cu、Zn、Cr、Cd等重金属的释放量降低了79.5%～87.2%,且形态更加稳定,经底泥毒性鉴别其浸出量分别降低了66.2%、81.5%、82.2%和78.6%,均低于危险废物毒性鉴别标准值,同时还使磷的释放量降低了约90%;停止投药两个月后,底泥中硫化物的含量稳定在0.035 g/kg以下;维持微碱性、好氧条件（pH≈8,DO〉2 mg/L）,可使表层底泥由黑色变成亮褐色,上覆水体水质稳定,黑臭基本消除。     

化学混凝强化去除微氧EGSB出水中的TP

采用硫酸铝混凝强化去除微氧EGSB反应器出水中的TP,考察了混凝时间和沉淀时间、混凝剂投量、pH和温度等对强化除磷效果的影响,以分析微氧EGSB/化学混凝组合工艺作为生活污水再生回用工艺的可行性。结果表明,在最佳Al3+/TP值(质量比)为1.5～2.3、混凝时间为20min、沉淀时间为20min的条件下,对TP的去除率可达94.6%～96.4%,出水TP可降至0.29mg/L,达到了GB18918—2002的一级A标准,证明了微氧EGSB/化学混凝组合工艺作为生活污水再生回用工艺是可行的。硫酸铝的混凝除磷效果对pH的变化较敏感,最佳pH值范围为6.5～7.2,此时对TP的去除率可达到90.8%～92.1%;微氧EGSB反应器出水pH值为6.5～8.5,投加硫酸铝后能获得85%以上的TP去除率,出水TP最高可达0.85mg/L,因此需要适当调节pH使出水TP0.5mg/L,以满足回用要求。硫酸铝混凝除磷的适宜温度为10～25℃,微氧EGSB反应器出水的温度满足此要求。     

ME/Fenton/AF/BAF工艺处理炼油废水研究

采用微电解/芬顿/厌氧/好氧生物滤池工艺(ME/Fenton/AF/BAF)处理炼油废水,探讨了各工段的工艺参数及工艺整体运行效果。试验得到最佳工艺参数如下:微电解单元的初始pH值为3,Na2SO4投加量为0.05 mol/L;双氧水的投加量为1.5 m L/L;AF/BAF工段的水力停留时间为(2+2)h。在上述工艺条件下,ME/Fenton/AF/BAF工艺连续运行处理炼油废水时对COD、氨氮、油的平均去除率分别为85.2%、85.0%、90.1%。     

Oxygen consumption by a sediment bed for stagnant water: comparison to SOD with fluid flow

A model of sedimentary oxygen demand (SOD) for stagnant water in a lake or a reservoir is presented. For the purposes of this paper, stagnant water is defined as the bottom layer of stratified water columns in relatively unproductive systems that are underlain by silt and sand-dominated sediments with low-organic carbon (C) and nitrogen (N). The modeling results are compared to those with fluid flow to investigate how flow over the sediment surface raises SOD compared to stagnant water, depending on flow velocity and biochemical activity in the sediment. SOD is found to be substantially limited by oxygen transfer in the water column when water is stagnant. When flow over the sediment surface is present, SOD becomes larger than that for stagnant water, depending on flow velocity and the biochemical oxygen uptake rate in the sediment. Flow over the sediment surface causes an insignificant raise in SOD when the biochemical oxygen uptake rate is small. The difference between SOD with fluid flow and SOD for stagnant water becomes significant as the biochemical oxygen uptake rate becomes larger, i.e. SOD is 10-100 times larger when flow over the sediment surface is present.     

Oxygen microprofiles of trickling filter biofilms

Oxygen microprofiles of photosynthetic and non-photosynthetic biofilms of trickling filters from a sewage treatment plant were studied with Clark type oxygen microelectrodes. The oxygen profiles in photosynthetic biofilms exhibited pronounced changes with changing light conditions, and the profiles of both types of biofilm were affected by addition of nutrients. The existence of a 100–500 μm thick diffusive boundary layer in the water just above the biofilm was evident from all recordings. The O₂ gradient in this boundary layer was used to calculate diffusive fluxes of oxygen exchanged between the biofilms and the overlying water phase. The calculated fluxes were compared to the overall oxygen consumption rates measured experimentally and to the photosynthetic activity as measured with the microelectrodes. Approximately 60–70% of the oxygen produced in the algal films during photosynthesis was consumed within the films. At least one third of this consumption may be due to photorespiration. Dark/light and light/dark shifts demonstrated a very dynamic nature of the O₂ status of the algal films, showing an increase from anaerobic conditions to 500% air saturation and vice versa within 25 min. In the same regime, pH profiles showed a similar dynamic change, whereby pH varied between 8.1 and 9.7 in the same period.

The data obtained with the non-photosynthetic biofilms show that the oxygen respiration and oxygen penetration are mostly limited by diffusive oxygen transport through the boundary layer. The overall oxygen consumption of the heterotrophic biofilms equalled within ± 10% the estimates made from flux calculations.     

Coagulation of humic substances and dissolved organic matter with a ferric salt: an electron energy loss spectroscopy investigation

Transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS) was used to investigate the coagulation of natural organic matter with a ferric salt. Jar-test experiments were first conducted with a reconstituted water containing either synthetic or natural extracts of humic substances, and then with a raw water from Moselle River (France). The characterization of the freeze-dried coagulated sediment by EELS in the 250-450 eV range, showed that Fe-coagulant species predominantly associate with the carboxylic groups of organic matter, and that this interaction is accompanied by a release of previously complexed calcium ions. The variation of Fe/C elemental ratio with iron concentration provides insightful information into the coagulation mechanism of humic substances. At acid pH, Fe/C remains close to 3 over the whole range of iron concentrations investigated, while a much lower atomic ratio is expected from the value of optimal coagulant dosage. This suggests that a charge neutralization/complexation mechanism is responsible for the removal of humic colloids, the aggregates being formed with both iron-coagulated and proton-neutralized organic compounds. At pH 8, the decrease in Fe/C around optimal coagulant concentration is interpreted as a bridging of stretched humic macromolecules by Fe-hydrolyzed species. Aggregation would then result from a competition between reconformation of humic chains around coagulant species and collision of destabilized humic material. EELS also enabled a fingerpriting of natural organic substances contained in the iron-coagulated surface water, N/C elemental analyses revealing that humic colloids are removed prior to proteinic compounds.     

Sedimentary microbial oxygen demand for laminar flow over a sediment bed of finite length

Dead organic material accumulated on the bed of a lake, reservoir or wetland often provides the substrate for substantial microbial activity as well as chemical processes that withdraw dissolved oxygen (DO) from the water column. A model to estimate the actual DO profile and the "sedimentary oxygen demand (SOD)" must specify the rate of microbial or chemical activity in the sediment as well as the diffusive supply of DO from the water column through the diffusive boundary layer into the sediment. Most previous experimental and field studies have considered this problem with the assumptions that the diffusive boundary layer is (a) turbulent and (b) fully developed. These assumptions require that (a) the flow velocity above the sediment bed is fast enough to produce turbulent mixing in the boundary layer, and (b) the sediment bed is long. In this paper a model for laminar flow and SOD over a sediment bed of finite length is presented and the results are compared with those for turbulent flow. Laminar flow near a sediment bed is encountered in quiescent water bodies such as lakes, reservoirs, river backwaters, wetlands and ponds under calm wind conditions. The diffusive oxygen transfer through the laminar diffusive boundary layer above the sediment surface can restrict the microbial or chemical oxygen uptake inside the sediment significantly. The developing laminar diffusive boundary layer above the sediment/water interface is modeled based on the analogy with heat transfer, and DO uptake inside the sediment is modeled by Michaelis-Menten microbial growth kinetics. The model predicts that the rate of SOD at the beginning of the reactive sediment bed is solely dependent on microbial density in the sediment regardless of flow velocity and type. The rate of SOD, and the DO penetration depth into the sediment decrease in stream-wise direction over the length of the sediment bed, as the diffusive boundary layer above the sediment/water interface thickens. With increasing length of the sediment bed both SOD rate and DO penetration depth into the sediment tend towards zero if the flow is laminar, but tend towards a finite value if the flow is turbulent. That value can be determined as a function of both flow velocity and microbial density. The effect of the developing laminar boundary layer on SOD is strongest at the very lowest flow velocity and/or highest microbial density inside the sediment. Under quiescent conditions, the effective SOD exerted by a reactive sediment bed of a lake or wetland approaches zero, i.e. no or very little oxygen demand is exerted on the overlying water column, except at the leading edge.     

城市河道底泥释磷的影响因素研究

自制模拟河道,取含磷的河道底泥进行试验,考察了温度、扰动、溶解氧等因素对河道底泥释磷的影响。结果表明,加大换水频率、缩短停留时间可以维持较好的水质,但并不能从根本上降低释磷量;溶解氧水平对底泥释磷的影响较大,低溶解氧水平(0.8 mg/L)下的释磷量是高溶解氧水平(7.2 mg/L)下的3.7倍;扰动(风)是影响底泥释磷的主要因素,有扰动时上覆水的TP浓度是无扰动时的4倍多;释磷强度会随温度的升高而明显增大,在静态条件下,水温为22℃时的TP浓度是8℃时的1.5倍。     

Measurement of sediment oxygen demand for modelling dissolved oxygen distribution in tidal Keelung River

The Keelung River is one of the major branches of the Danshuei River estuarine system, which runs the metropolitan capital city of Taipei, Taiwan, and receives a large of amount of wastewater. The dissolved oxygen (DO) concentration is generally low in the tidal portion of the Keelung River. Hypoxia/anoxia occurs often, particularly during a low-flow period. The sediment oxygen demand (SOD) amounts to a significant value, hence increasing the total oxygen demand load of the river. The present work reports on laboratory SOD made on grab sediment core samples in situ that are undisturbed. The results reveal that SOD values fluctuate with variations in seasons and are higher in summer due to a high-temperature effect. It was found in the laboratory tests that the average SOD (at 20 °C) value is 0.76 g/m²/day and the maximum SOD (at 20 °C) value reaches 1.58 g/m²/day. The mean values of measured SOD at each station were adopted in the vertical two-dimensional water quality model to simulate the DO distribution along the tidal Keelung River. The simulated results are in reasonable agreement with the measured DO distribution in the river. Model sensitivity analyses were also conducted with increasing and decreasing SOD. It reveals that SOD is an important parameter that affects the DO distribution in the tidal estuary.     

Phosphorus release rates from sediments and pollutant characteristics in Han River, Seoul, Korea

The Han River is 469.7-km long and drains a 26219-km(2) watershed. The sediments in the river are highly polluted due to inputs from upstream tributaries as well as partially treated municipal wastewaters that are discharged to the river. The water quality and strategy for control are important because the river is the primary drinking water supply for the City of Seoul, as well as being a major source for irrigation and industrial water. The Jamsil submerged dam partitions the river to isolate an upstream area for drinking water, but also captures sediments. Samples from four sites were studied to determine sediment pollutant concentrations and phosphorus release rates. Phosphorus tends to desorb from sediments when the concentration of overlying water is less than 1.4 mg/l. Water column P concentrations range from 0.04 to 0.1 mg/l, which suggests that sediments will act as a P source. In a series of batch experiments, P was released at approximately 15-20 mg/m(2)week in the winter (1-5 degrees C) and as much as 90 mg/m(2)week in the summer (20-24 degrees C), and is also a function of pH and dissolved oxygen concentration. The sediment total phosphorus concentration, which averages 833 mg/kg, is evenly distributed among non-apatite-P (33%), apatite-P (32%) and residual-P (34%). An equilibrium model is proposed to describe release rate.     

Effect of pH, ionic strength, dissolved organic carbon, time, and particle size on metals release from mine drainage impacted streambed sediments

Acid-mine drainage (AMD) input to a stream typically results in the stream having a reduced pH, increased concentrations of metals and salts, and decreased biological productivity. Removal and/or treatment of these AMD sources is desired to return the impacted stream(s) to initial conditions, or at least to conditions suitable for restoration of the aquatic ecosystem. Some expected changes in the water chemistry of the stream following removal of AMD input include an increase in pH, a decrease in ionic strength, and an increase in dissolved organic carbon (DOC) concentrations from increased biological activity in the absence of toxic metals concentrations. These changes in water chemistry may cause the existing contaminated bed sediments to become a source of metals to the stream water. Streambed sediments, collected from North Fork Clear Creek (NFCC), Colorado, currently impacted by AMD, were assessed for the effects of pH, ionic strength, DOC concentration, time, and particle size on metals release using a factorial design. The design included two levels for each chemical parameter (ionic strength = 40 and 80% lower than ambient; pH = 6 and 8; and DOC = 1 and 3 mg/l higher than ambient), ten sampling times (from zero to 48 h), and two size fractions of sediments (63 μm ≤ x < 2 mm and <63 μm). Greater concentrations of metals were released from the smaller sized sediments compared with the larger, with the exception of Cu. A mild acid digestion (0.6 M HCl) evaluated the amount of each metal that could be removed easily from each of the sediment size fractions. Release of all metals over all time points, treatments, and from both sediment sizes was less than 1% of the extractable concentrations, with the exception of Mn, which ranged from 4 to 7% from the smaller sized sediment. Greater percentages of the 0.6 M HCl-extractable concentrations of Cu, Fe, and Zn were released from the larger sized sediment, while this was true for release of Cd and Mn from the smaller sized sediment. Thus, at least for Cd and Mn, the observed higher concentrations released from the smaller sized sediment with each treatment solution is not simply a function of these particles having higher concentrations available for release, but that these metals also are more readily released from the smaller sediment particles versus the larger. DOC concentration strongly influenced the release of Cu; ionic strength strongly influenced the release of Cd, Mn, and Zn; and interaction effects were observed with the release of Cu, Mn, and Zn from the larger size fraction and with the release of Zn from the smaller size fraction. Overall, results suggest that the expected changes in water chemistry following removal/treatment of the AMD sources would result in a release of metals from the existing sediments, with a greater effect on the release of Cu and Fe, than on the release of Cd, Mn, and Zn.     

The dynamics of alkalinity generation by an anoxic sediment exposed to acid water

The time dependence of the rate of generation of alkalinity by productive sediments treated with acid waters was investigated for various conditions using continuously stirred flowing reactors. Complete mass balances allowed the generated alkalinity to be related to specific processes, none of which were affected by light. The high rate of oxidation of organic material was sufficient to consume all the oxygen, nitrate and sulphate supplied to the vessels during the first few days of incubation, but by 15 days sulphate reduction had ceased and oxygen and nitrate reduction were incomplete. In incubations supplied with anoxic waters there was an initial small release of calcium, but by 10–15 days the generation of alkalinity could be accounted for by nitrate reduction (23%), sulphate reduction (47%), Fe(II) production (23%) and NH₄⁺ production (7%). Iron(II) was exhausted when only 1% of the total amount of iron in the sediment had been released. In incubations supplied with oxygenated waters sulphate was only reduced during the first 10 days while oxygen was completely consumed. By 15 days there was incomplete consumption of oxygen and the generation of alkalinity was accounted for by nitrate reduction (36%), calcium release (53%) and NH₄⁺ production (11%). Comparisons of reaction rates indicate that calcium is released by being replaced by ammonium ions which are generated by decomposition of organic matter. Although, in the longer term, more base is generated by sediment incubated anoxically, sediments incubated with oxygenated water generate base more rapidly for the first few days until the most readily oxidized organic matter is consumed.