电吸附除盐后续工艺电解水催化还原去除硝酸盐的研究

针对碳气凝胶电极电吸附除盐工艺去除硝酸盐过程中存在的问题,采用电解水催化还原工艺作为其后续工艺,在原碳气凝胶电吸附除盐工艺装置上,进行了一系列平衡试验,对其影响因素进行了研究.结果表明,可以在不增加任何设备的情况下,大幅提高碳气凝胶电极电吸附除盐工艺去除硝酸盐的效果,并使电极得到再生.     

超声波强化活性污泥活性的试验研究

研究了超声波对活性污泥活性的影响,用污泥好氧速率OUR来衡量活性,并通过模拟人工废水试验验证。研究表明超声波频率为25kHz,输出声密度为0·2W/mL,作用60s后,污泥活性比原污泥提高30.49%;相同条件超声3s后,污泥活性比原污泥提高20%。试验中从能耗角度推荐选用超声3s。脉冲方式比连续超声更能改善污泥活性,且脉冲比1∶1时效果最好。超声3s后的活性污泥处理人工废水的出水水质明显好于未经处理的出水水质。     

Simultaneous removal of nitrate and phosphate using cross-flow micellar-enhanced ultrafiltration (MEUF).

The feasibility of cross-flow micellar-enhanced ultrafiltration (MEUF) was investigated to remove nitrate and phosphate simultaneously. At the above critical micelle concentration (CMC), a cationic surfactant added in wastewater forms micelles, which have positive charge on their surface. Anionic contaminants such as nitrate and phosphate can be bound on the micelles by electrostatic interaction, and the micelle-pollutants complex is removed effectively by ultrafiltration. In this study, a cross-flow MEUF system was designed and investigated the feasibility of MEUF for field application. A cationic surfactant, cetylpyridinium chloride (CPC), was used, and the synthetic wastewater was treated by the polyacrylonitrile membranes with molecular weight cut-off (MWCO) of 30,000 Da and 10,000 Da. With the molar ratio of CPC to total pollutants of > 3, > 86% of nitrate and > 91% of phosphate were removed, respectively, and > 97% of CPC was also rejected. The flux was maintained 20-30% of the flux of distilled water. Therefore, it is feasible to remove nitrate and phosphate simultaneously using the cross-flow MEUF system.     

浅议关中灌区改造工程对环境的影响

水利工程建设中的环境保护工作在我国刚起步不久,尚无很成熟的经验和办法可以借鉴.关中灌区改造工程是陕西省利用世行贷款进行的一项重点水利建设项目,实施三年来在环保方面作了大量的工作,取得了一定的成绩.本文对该项目一些具体管理措施作了简要阐述,以供参考.     

The effect of nitrite on aerobic phosphate uptake and denitrifying activity of phosphate-accumulating organisms.

An anaerobic/aerobic/anoxic/aerobic sequencing batch reactor (SBR) was operated with municipal wastewater to investigate the effect of nitrite on biological phosphorus removal (BPR). When nitrite accumulated, aerobic phosphate uptake activity significantly decreased and, in case of hard exposure to nitrite, BPR severely deteriorated. The interesting observation was that the relative anoxic activity of phosphate accumulating organisms (PAOs) increased after nitrite exposure. Moreover batch tests of aerobic phosphate uptake in the presence/absence of nitrite indicated that PAOs with the higher relative anoxic activity are less sensitive to nitrite exposure. From these results, we concluded that BPR is sensitive to nitrite exposure, but BPR containing PAOs with the higher relative anoxic activity is possibly more stable against nitrite than BPR containing PAOs with the lower relative anoxic activity.     

Study of different methods for enhancing the nitrate removal efficiency of a zero-valent metal process.

This study explores the effect of several enhancing methods, namely acid wash pretreatment, ultrasound treatment and addition of nickel catalyst on the nitrate removal efficiency of three zero-valent metals--iron, aluminium and zinc. It is hoped that by learning about the major reaction pathways of nitrate removal with zero-valent metals and the main factors influencing the reactivity of those zero-valent metals, optimum process conditions may be identified. The study results show that direct transfer of electrons is the major reaction pathway. Thus increasing a clean, fresh metal surface and decreasing the thickness of the diffusion layer to accelerate mass transfer are the main determinants of reaction rate. In the absence of a clean, fresh metal surface, the catalytic reaction of nickel becomes the primary removal pathway.     

梅林水厂污泥脱水特性与强化试验研究

针对深圳市梅林水厂回收水沉淀池的排泥水处理工艺存在的问题,分析了其污泥脱水性能及影响因素,并在现有工艺基础上,进行了絮凝剂优选及投加量优化试验以强化污泥脱水性能.结果表明,使用PAM进行污泥调质,操作简单,效果显著.投加量在1‰～1.5‰时,阴离子型PAM可将污泥性质调节至易脱水的范围之内.污泥脱水性能的提高与PAM的吸附架桥作用密切相关,与其电性中和作用关系不大;pH变化则仅对非离子型PAM影响较大.阴离子型PAM价格低,用量少,且不易受pH变化影响,适宜在梅林水厂生产工艺中使用.     

水井设计与完井工艺改进技术研究

合理的水井设计与完井工艺能提高水井产量、延长水井使用寿命。本文通过对辽河油田矿区水井测井资料与水质化验资料的分析,总结出了含水层视电阻率与地下水矿化度的关系,为水井设计提供了可靠的依据,并在实践中得到了成功应用;PVC-U塑料贴砾滤水管防砂效果好、操作简单,在国外被大量应用。本文阐述了其性能特点并结合修井实践,提出了推广建议。     

排泥水处理系统药剂试验及工艺改进

保定中法供水有限公司排泥水处理系统采用Densadeg高密度浓缩沉淀技术,在实际运行中出现跑矾花的问题,影响了系统的正常运行.为此分别在排泥水处理系统进水、药剂选择、工艺参数调整等环节进行了改进.同时为了达到了节能降耗的目的,还对部分机电设备进行了更换,取得了较好的经济效益,排泥水处理系统日耗电节约200～300kW·h.     

Effects of various process parameters on struvite precipitation kinetics and subsequent determination of rate constants.

In this paper, struvite (MgNH(4)PO(4).6H(2)O) precipitation kinetics were studied with different operating conditions (varying supersaturation, pH, Mg:P ratio, degree of mixing and seeding conditions) and relevant rate constants were determined by fitting a slightly modified first-order kinetic model to the experimental data obtained. The rate of change of ortho-P concentration in the bulk solutions increases with increasing supersaturation ratio. The estimated rate constants are 2.034, 1.716 and 0.690 hr(-1) for the supersaturation ratio of 9.64, 4.83, and 2.44, respectively. Kinetic parameters were also evaluated for the Mg:P ratio between the ranges of 1.0 and 1.6, indicating higher phosphorus removal efficiency with increasing Mg:P ratio. The rate constants were found to be 0.942, 2.034 and 2.712 hr(-1) for Mg:P ratios of 1.0, 1.3 and 1.6, respectively. The experimental observations for kinetic study of struvite precipitation with different stirrer speeds clearly show that the mixing intensity used had little effect on the intrinsic rate constants. K values found to be 2.034 and 1.902 h(-1) for 100 and 70 rpm, respectively. Seeding, with 250-500 microm of seed crystals during the struvite precipitation kinetics test, was found to have very little effect on the ortho-P removal.     

Examining substrate uptake patterns of Rhodocyclus-related PAO in full-scale EBPR plants by using the MAR-FISH technique.

While recognised as the important population responsible for enhanced biological phosphorus removal (EBPR), detailed knowledge on the physiology of Rhodocyclus-related polyphosphate accumulating organisms (PAO) has yet to be grasped. The objective of this study was to examine the in situ substrate uptake patterns of Rhodocyclus-related PAO present in full-scale EBPR plants by the combined technique of microautoradiography-fluorescent in situ hybridization (MAR-FISH). The presence of these PAO in the four investigated plants was confirmed by FISH and they constituted 17%, 9%, 8%, and 7% of the sludge community. By using MAR-FISH technique, Rhodocyclus-related PAO in all the plants demonstrated similar anaerobic substrate uptake patterns. They were capable of assimilating acetate, aspartate and glutamate under anaerobic condition but they showed negative uptake with palmitate. A significant fraction of the MAR-positive cells assimilated acetate, aspartate or glutamate was found to be Rhodocyclus-related PAO. Dual staining with DAPI and FISH showed that these PAO also accumulated polyphosphate aerobically with aspartate and glutamate as carbon source. The ability of assimilating amino acids besides acetate strongly indicates the versatile physiology of Rhodocyclus-related PAO, which could benefit them to achieve predominance in EBPR activated sludge.     

淤地坝卧管的改进研究

淤地坝是黄土高原地区治理水土流失的重要措施,而放水建筑物是拦沙、排水、淤地、造田的重要保证。卧管是被广泛采用的一种放水建筑物,本文对卧管放水孔进行优化改进研究,提出了改进方案,提高了泄水能力,保障了坝地稳产保收,对于改进淤地坝设计具有参考价值。     

Effect of chlorination bulking control on water quality and phosphate release/uptake in an anaerobic-oxic activated sludge system.

This study evaluates the effect of chlorination bulking control on water quality and phosphate release/uptake in an anaerobic-oxic activated sludge system. A series of batch experiments with different specific NaOCl mass dose were conducted to determine the sludge settling properties, supernatant water quality and phosphate metabolism behavior of filamentous bulking sludge. The harvested sludge was from a continuous-flow anaerobic-oxic (A/O) activated sludge pilot-plant, i.e., enhanced biological phosphorus removal (EBPR) system, operated with 15 days of sludge retention time. The filamentous bacteria in the A/O pilot plant were identified to be Thiothrix according to Eikelboom's classification techniques, which was in accordance with the high influent sulfate concentration of this study (50 mg/L sulfate). Increasing NaOCI concentration, as revealed by experimental results, obviously decreased the sludge settling properties (SVI values and zone settling velocities) and meanwhile significantly reduced supernatant water quality (COD, SS, TP) mainly due to higher suspended solids caused by floc disruption. Moreover, the nine-hour batch experiments indicated that high NaOCI dosage (40 mg/gMLSS) completely deteriorated phosphate metabolism of EBPR sludge. Such a high dosage of chlorination further confirmed overdosing through disappearance of intracellular PHB and death of protozoa by microscopic investigation. Still, phosphate release/uptake behavior of EBPR sludge properly functions at low NaOCl dosage (5 mg/g MLSS). Besides, phosphate metabolism worsens rapidly before the SVI value reaches its lowest level. These findings imply that determining NaOCI requirement with merely SVI values can readily result in chlorination overdosing. Proper NaOCI dosage requires a delicately balanced consideration between sludge settling improvement, water quality demand and phosphate metabolism. Batch test of phosphate release/uptake is apparently a prerequisite to conclude an appropriate NaOCl dosage for bulking control.     

An extension of the Anaerobic Digestion Model No. 1 to include the effect of nitrate reduction processes.

Nitrate reduction processes were incorporated into the IWA Anaerobic Digestion Model No. 1 (ADM1) in order to account for the effect of such processes on fermentation and methanogenesis. The general structure of the ADM1 was not changed except for modifications related to disintegration and hydrolysis of complex organic matter and decayed biomass. A fraction of butyrate/valerate and propionate degraders was assumed to be the fermentative denitrifiers carrying out fermentation in the absence of N-oxides. Nitrate reduction proceeded in a stepwise manner to nitrite, nitric oxide, nitrous oxide and nitrogen gas using four substrates as electron and/or carbon source. The utilization of the four substrates and N-oxides was based on stoichiometry and kinetics. The inhibitory effect of N-oxides on the methanogens was accounted for by the use of non-competitive inhibition functions. Model simulations were compared with experimental data obtained with a batch, mixed fermenting and methanogenic culture amended with various initial nitrate concentrations.     

Treatment of spent brine from a nitrate exchange process using combined biological denitrification and sulfate precipitation.

A combined biological denitrification and sulfate precipitation process was developed to treat and reuse the spent brine produced by a nitrate exchange system. Although the spent brine contained a relatively high salt concentration, more than 80% of NO3(-)-N fed into the denitrification reactors was removed at a nitrate-N loading rate of 2.2 g NO3(-)-N/l x day, regardless of the presence or absence of sulfate up to 8,000 mg/l. Sulfate present in the spent brine was successfully removed by the addition of BaCl2 and the settling velocity of BaSO4 suspension was remarkably enhanced by FeCl3 coagulation. Since most of the chloride consumed in regenerating the exhausted resins was replaced during chemical treatment with BaCl2 and FeCl3, it was possible to reuse the treated spent brine as a regenerant after compensating for the small amount of unreplaced NaCl.     

Water fluxes and diffuse nitrate pollution at river basin scale: coupling of agro-economic models and hydrological approaches.

An integrated model system has been developed to estimate the impact of nitrogen reduction measures on the nitrogen load in groundwater and in river catchment areas. The focus lies on an area-wide, regionally differentiated, consistent link-up between the indicator "nitrogen balance surplus" and nitrogen charges into surface waters. As a starting point of the analysis actual nitrogen surpluses in the soil were quantified using the agro-economic RAUMIS-model, which considers the most important N-inputs to the soil and N-removals from the soil through crop harvest. The most important pathways for diffuse nitrogen inputs into river systems are modelled with the water balance model GROWA. Additionally, the time-dependent nitrogen degradation along the nitrogen pathways in soil and groundwater are modelled using the WEKU-model. The two selected river basins in Germany cover a variety of landscape units with different hydrological, hydrogeological and socio-economic characteristics. The results indicate a wide range of annual nitrogen surpluses for the rural areas between than 10 kg N ha(-1) x a(-1) and 200 kg N ha(-1) x a(-1) or more, depending on the type and intensity of farming. The level of nitrogen inputs into the surface waters is reduced because of degradation processes during transport in soil and groundwater. Policy impact analyses for a nitrogen tax and a limitation of the livestock density stress the importance of regionally adjusted measures.     

Influence of ORP variation, carbon source and nitrate concentration on denitrifying phosphorus removal by DPB sludge from dephanox process.

The effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by denitrifying phosphorus removal bacteria sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in the anoxic phase increased with the high initial anaerobic carbon source addition. However, once the initial COD concentration reached a certain level, which was in excess of the PHB saturation of Poly-p bacteria, residual COD carried over to the anoxic phase inhibited the subsequent denitrifying phosphorus uptake. This was equal to supplementing the external carbon source to the anoxic phase, furthermore the higher the external carbon source concentration the more powerful the inhibition caused. High nitrate concentration in the anoxic phase increased the initial denitrifying phosphorus rate. Oncethe nitrate was exhausted, phosphate uptake changed to phosphate release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found that ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the dinitrification and anoxic phosphorus uptake operations.     

Improving the start-up of an EBPR system using OUR to control the aerobic phase length: a simulation study.

The enhanced biological phosphorus removal (EBPR) process is based on enriching the sludge with polyphosphate accumulating organisms (PAO) which are scarce in conventional non-EBPR wastewater treatment plant sludge. Hence, the start-up of EBPR systems (i.e. enriching the sludge with PAO) can be very slow and complex. A simulation study of a possible improvement of the start-up of an EBPR system in a sequencing batch reactor is presented in this work. The improvement is based on reducing the length of the aerobic phase so that it coincides with the depletion of orthophosphate from the medium. This improvement, though verified by simulation to be very successful, requires a good on-line orthophosphate sensor. To avoid this technical limitation, a link between oxygen uptake rate (OUR) measurements and orthophosphate presence is proposed. This link allows the control of the aerobic phase length with OUR as a measured variable and, consequently, a considerable improvement with respect to the conventional fixed aerobic phase length operation. An improvement of 95% in the ratio of PAO to heterotrophs and an increase of 30% in the final amount of PAO in sludge is achieved with this control strategy. The kinetic mod for simulations was a modification of the Activated Sludge Model 2d.     

Effect of organic loading rate on a wastewater treatment process combining moving bed biofilm and membrane reactors.

The effect of moving bed biofilm reactor (MBBR) loading rate on membrane fouling rate was studied in two parallel units combining MBBR and membrane reactor. Hollow fiber membranes with molecular weight cut-off of 30 kD were used. The HRTs of the MBBRs varied from 45 min to 4 h and the COD loading rates ranged from 4.1 to 26.6 g COD m(-2) d(-1). The trans-membrane pressure (TMP) was very sensitive to fluxes for the used membranes and the experiments were carried out at relatively low fluxes (3.3-5.6 l m(-2) h(-1)). Beside the test with the highest flux, there were no consistent differences in fouling rate between the low- and high-rate reactors. Also, the removal efficiencies were quite similar in both systems. The average COD removal efficiencies in the total process were 87% at 3-4 h HRT and 83% at 0.75-1 h HRT. At high loading rates, there was a shift in particle size distribution towards smaller particles in the MBBR effluents. However, 79-81% of the COD was in particles that were separated by membranes, explaining the relatively small differences in the removal efficiencies at different loading rates. The COD fractionation also indicated that the choice of membrane pore size within the range of 30 kD to 0.1 microm has very small effect on the COD removal in the MBBR/membrane process, especially with low-rate MBBRs.     

离子交换工艺对地表水中硝酸盐的去除效能及应用模式

硝酸盐是影响饮用水质量的重要水质参数之一,近年来部分地表水厂也面临硝酸盐超标的问题.在对LMK水源地水质特征及硝酸盐来源分析的基础上,利用中试研究了离子交换工艺对地表水中硝酸盐的去除效能,优化了工艺参数,并探讨了其在地表水厂中的应用模式.结果表明:水源水中硝酸盐浓度随季节呈现动态变化规律,主要来源于周边的苹果园,降雨过程中雨水冲刷、入渗最终形成的汇流是其主要输入途径;针对硝酸盐去除的最佳运行及再生条件为:滤速6 m/h,采用质量分数10％的NaCl溶液进行再生,再生液用量为3倍树脂体积,再生时间2 h,再生效率可达85％～90％,且保持稳定;离子交换工艺宜设置在砂滤之后、消毒之前,可以作为去除地表水中硝酸盐的备选工艺.