絮凝—沉淀一体化设备对海水的预处理效果

采用絮凝-沉淀一体化设备对渤海海水进行反渗透海水淡化预处理的试验,考察了该设备的处理效果。当聚合氯化铁（PFC）的投量为5．0mg／L、聚丙烯酰胺（PAM）的投量为3.0mg／L时,在适宜的pH条件下（pH值约为11）,经该设备处理后,出水的浊度〈1.0NTU,SDI值〈4．0,CODMn〈3.0mg／L。出水水质可满足反渗透工艺对进水的水质要求。     

Conventional oxidation treatments for the removal of arsenic with chlorine dioxide, hypochlorite, potassium permanganate and monochloramine

Arsenic is widespread in soils, water and air. In natural water the main forms are arsenite (As(III)) and arsenate (As(V)). The consumption of water containing high concentration of arsenic produces serious effects on human health, like skin and lung cancer. In Italy, Legislative Decree 2001/31 reduced the limit of arsenic from 50 to 10 μg/L, in agreement with the European Directive 98/83/EC. As consequence, many drinking water treatment plant companies needed to upgrade the existing plants where arsenic was previously removed or to build up new plants for arsenic removal when this contaminant was not previously a critical parameter.Arsenic removal from water may occur through the precipitation with iron or aluminum salts, adsorption on iron hydroxide or granular activated alumina (AA), reverse osmosis and ion exchange (IE). Some of the above techniques, especially precipitation, adsorption with AA and IE, can reach good arsenic removal yields only if arsenic is oxidized.The aim of the present work is to investigate the efficiency of the oxidation of As(III) by means of four conventional oxidants (chlorine dioxide, sodium hypochlorite, potassium permanganate and monochloramine) with different test conditions: different type of water (demineralised and real water), different pH values (5.7-6-7 and 8) and different doses of chemicals.The arsenic oxidation yields were excellent with potassium permanganate, very good with hypochlorite and low with monochloramine. These results were observed both on demineralised and real water for all the tested reagents with the exception of chlorine dioxide that showed a better arsenic oxidation on real groundwater than demineralised water.     

The fate of Transparent Exopolymer Particles (TEP) in integrated membrane systems: Removal through pre-treatment processes and deposition on reverse osmosis membranes

The abundance of Transparent Exopolymer Particles (TEP) in surface waters has been unnoticed for many years until recently as a potential foulant in reverse osmosis systems. Recent studies indicate that TEP may cause organic and biological fouling and may enhance particulate/colloidal fouling in reverse osmosis membranes. The presence of TEP was measured in the raw water, the pre-treatment processes and reverse osmosis (RO) systems of 6 integrated membrane installations. A spectrophotometric method was used to measure TEP in the particulate size range (>0.40 μm) and was extended to measure TEP in the colloidal size range (0.05–0.40 μm). Ultrafiltration pre-treatment applied in 4 plants, totally removed particulate TEP while microfiltration systems (2 plants) and coagulation/sedimentation/rapid sand filtration systems (3 plants) partially removed this fraction. None of the pre-treatment systems investigated totally removed colloidal TEP. Biopolymer analysis using LC–OCD showed consistency between colloidal TEP and polysaccharide removal by UF pre-treatment and further verified the presence of TEP in the RO feedwater. TEP deposition in the RO system was determined after measuring total TEP concentrations in the RO feed and concentrate. The TEP deposition factors and specific deposition rates indicate that TEP accumulation had occurred in all plants investigated. This observation was verified by an autopsy of RO modules from two RO plants. Further improvement and verification of the (modified) TEP method, in particular the calibration, is necessary so that it can be employed to investigate the role of TEP in the fouling of RO systems.     

大型反渗透海水淡化系统双端产水脱硼工艺研究

针对大型反渗透海水淡化系统,设计了一种双端产水脱硼工艺,并采用反渗透系统模拟软件研究了二级进水pH值、海水温度和硼含量等参数对工艺脱硼效果的影响。结果表明,该工艺能有效脱除海水中的硼,当二级进水pH值为9. 5时,产水水质可以达标。当海水温度和硼含量均较低时,仅开启一级系统时产水水质即可达标;当海水温度> 13℃或硼含量> 2. 3 mg/L时,需启用二级系统进一步脱硼;当海水温度> 30℃或硼含量> 6. 0 mg/L时,还需适当提高二级进水pH值来增强反渗透膜的脱硼率,以实现产水硼含量达标。与常规脱硼工艺相比,双端产水脱硼工艺通过减少43%的二级系统处理规模,使二级系统的建设投资成本和运行成本均减少43%。     

O3/BAC工艺应用于城市污水深度处理

为使再生水适合不同用途,对经过混凝沉淀和砂滤处理的再生水进行了臭氧-生物活性炭的深度处理.在臭氧消耗量和反应时间分别为5 mg/L和10 min,BAC空床停留时间(EBCT)为10 min的条件下,臭氧-生物活性炭工艺对CODMn、DOC、UV254和色度平均去除率为32.4%、29.2%、48.6%和80.1%,出水CODMn、DOC、UV254和色度的平均值分别为3.3 mg/L、4.0mg/L、0.05 cm-1和2.0倍;臭氧生物活性炭工艺出水SDI《4,从而满足了反渗透系统的进水要求.     

预氧化强化混凝工艺处理南水北调-水库掺混源水

针对邯郸市双水源供水体系,开展了预氧化强化混凝工艺处理南水北调-本地水库掺混源水试验。结果表明,单因素试验得到的PAC、次氯酸钠最佳投加量分别为5～15、0. 1～1. 0mg/L,慢速反应搅拌速度以60～100 r/min为宜;采用Box-Behnken法对单因素试验参数进行优化,并建立了响应值为叶绿素a和浊度去除率与PAC、次氯酸钠投加量及慢速反应搅拌速度的二次回归模型,通过Design-Expert软件得到的最优工艺参数如下:PAC投加量为11. 85 mg/L、次氯酸钠投加量为0. 88 mg/L、慢速反应搅拌速度为67 r/min,此时对叶绿素a和浊度去除率的预测值分别为93. 27%、90. 79%,与实测值93. 26%、90. 85%高度接近。     

A^2O/高压脉冲电絮凝/O3-BAC/膜法处理焦化废水

吕梁三泉焦化工业园区污水处理厂率先采用A^2O/高压脉冲电絮凝/高密度澄清池/臭氧-活性炭滤池/超滤/反渗透组合工艺处理焦化废水。该组合工艺设计紧凑,技术先进,处理效果好。在废水处理量为9550 m^3/d,进水COD、氨氮、SS、电导率、浊度、总硬度、Cl-平均浓度分别为574 mg/L、44.2 mg/L、275 mg/L、5600μS/cm、146 NTU、210 mg/L和740 mg/L时,系统出水所有指标均远优于《工业循环冷却水处理设计规范》(GB/T 50050—2007)规定的再生水水质标准,并全部实现达标回用。本工程直接运行费用合计为4.47元/m^3。     

Adsorptive selenite removal from water using iron-coated GAC adsorbents

Removal of selenite from aqueous phase using iron-coated granular activated carbons (GAC) was investigated in this study. Five different types of GAC were used for iron coating by oxidizing ferrous chloride with sodium hypochlorite and the iron-coated GAC (Fe-GAC) were tested for selenite removal. Nitrogen adsorption-desorption analyses indicated that Brunauer-Emmett-Teller (BET) specific surface area, pore size, and pore volume decreased with the iron coating. The Darco 12x20 GAC was shown to be the most effective adsorbent among the five tested GACs after iron coating. Among the different concentrations used for iron coating, the Darco 12x20 GAC coated with 0.1M ferrous chloride achieved the highest selenite removal (97.3%). High removal efficiency of selenite occurred in a wide range of pH (i.e., 2-8), but the efficiency decreased when pH was higher than 8. Adsorption kinetics showed that selenite removal efficiency reached more than 90% after 6-h adsorption for initial selenium concentration of 2mg/L and equilibrium was obtained after 48h. A pseudo-second-order kinetic model was found to characterize the adsorption kinetics well for all the initial selenium concentrations and temperatures tested (R(2)>/=0.9969). Three temperatures (25, 35, 45 degrees C) were used to examine temperature effect on the adsorption behavior of the Fe-GAC with initial selenium concentration of 1mg/L. Activation energy was calculated to be 30.42kJ/mol. Adsorption isotherms for initial selenium concentration of 2mg/L at various temperatures and ionic strengths were developed and the data generally fit the Langmuir model well (R(2)>/=0.994). The adsorption capacity reached as high as 2.50mg-Se/g-adsorbent at equilibrium for initial concentration of 2mg/L at 25 degrees C. The Gibbs free energy was determined to be negative, indicating the spontaneous nature of the adsorption reaction. Oxyanion competitive adsorption showed that sulfate (0.1-5mM) barely affected selenite adsorption. Other anions (phosphate, silicate and carbonate) impact selenite adsorption to various degrees with phosphate completely excluded selenite adsorption at 5mM. The possible adsorption mechanisms were discussed.     

MCM/RO工艺对二级出水的深度处理效果

采用微滤-活性炭过滤-微滤-反渗透（MCM／RO）工艺对污水处理厂的二沉池出水进行深度处理,考察了该工艺的处理效果。结果表明,该工艺对浊度、CODMn、TOC、UV254、细菌和总大肠菌群均有良好的去除效果,上述各指标的出水平均值分别为0．095NTU、2．57mg/L、0．84mg/L、0．013cm^-1、16个／L和11个／L。RO膜对砷、镉、铅的截留效果良好,平均去除率分别为90．5％、99％和98％。     

混凝沉淀法对砷污染物的去除性能研究

采用次氯酸钠和二氧化氯作为氧化剂,三氯化铁和聚合氯化铝作为混凝剂,分别考察了混凝沉淀工艺及预氧化+混凝沉淀工艺对原水中As(Ⅲ)和As(Ⅴ)的去除效果.结果表明:三氯化铁和聚合氯化铝对As(Ⅴ)均有较好的去除效果,投加量大于3 mg/L,即可将As(Ⅴ)由0.1mg/L左右降至0.005 mg/L以下,三氯化铁对As(...     

Evaluation of chemicals to control the generation of malodorous hydrogen sulfide in waste water

The effect of hydrogen peroxide, sodium/calcium hypochlorite and ferrous/ferric salts on hydrogen sulfide dissolved in waste water were investigated to establish an effective odour control system for Kuwait Sewage Networks. The waste water samples were collected from the inlet structure of main pumping station with pressure pipelines and analyzed for dissolved sulfide and pH before and after addition of chemicals individually and in combination under controlled laboratory conditions. The waste water contained dissolved sulfide in the range of 18 to 25 mg/l and pH ranged between 7.2 and 7.8. Various concentrations of above mentioned chemicals were tried to determine the accurate chemical requirement for oxidation or precipitation of dissolved sulfide in waste water. The reaction temperature was maintained at 35°C (±2°C), the normal temperature of waste water in Kuwait during summer. To oxidize 1 g of sulfide 1.25, 2.0 and 1.8 g hydrogen peroxide, sodium hypochlorite and calcium hypochlorite were required respectively. To remove 1 g of sulfide by precipitation with ferrous sulfate and ferric salt solution, 8 g and 4 g ferrous and ferric salt were required respectively under laboratory investigations. A combination of sodium hydroxide and sodium hypochlorite was also studied to control malodorous hydrogen sulfide in waste water. The addition of sodium hydroxide with sodium hypochlorite in waste water reduced the demand of hypochlorite 50%. This procedure was found to be cost effective and best suited for the warm climate of Kuwait and was implemented in the field at a screw conveyor type lifting station with gravity sewer pipelines. When sodium hypochlorite was injected without shock loadings of sodium hydroxide 46% reduction of dissolved sulfides was recorded and it was increased to 57% with shock loadings of sodium hydroxide, though the quantity of sodium hypochlorite was reduced to half than the former case. Similarly, 45 and 70% reduction in the emission of gaseous hydrogen sulfide was recorded with NaOCl injection without and with NaOH shock loading respectively. The cost comparison of all the chemicals when applied in field is also presented.     

Reverse osmosis desalination: Water sources, technology, and today's challenges

Reverse osmosis membrane technology has developed over the past 40 years to a 44% share in world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. The use of membrane desalination has increased as materials have improved and costs have decreased. Today, reverse osmosis membranes are the leading technology for new desalination installations, and they are applied to a variety of salt water resources using tailored pretreatment and membrane system design. Two distinct branches of reverse osmosis desalination have emerged: seawater reverse osmosis and brackish water reverse osmosis. Differences between the two water sources, including foulants, salinity, waste brine (concentrate) disposal options, and plant location, have created significant differences in process development, implementation, and key technical problems. Pretreatment options are similar for both types of reverse osmosis and depend on the specific components of the water source. Both brackish water and seawater reverse osmosis (RO) will continue to be used worldwide; new technology in energy recovery and renewable energy, as well as innovative plant design, will allow greater use of desalination for inland and rural communities, while providing more affordable water for large coastal cities. A wide variety of research and general information on RO desalination is available; however, a direct comparison of seawater and brackish water RO systems is necessary to highlight similarities and differences in process development. This article brings to light key parameters of an RO process and process modifications due to feed water characteristics.     

Evaluation of an MBR-RO system to produce high quality reuse water: microbial control, DBP formation and nitrate

A membrane bioreactor and reverse osmosis (MBR-RO) system was developed to assess potential reuse applications of municipal wastewater. The objective of the study was to examine the water quality throughout the system with a focus on waterborne pathogens, disinfection by-products (DBPs) and nitrate. This paper will discuss the presence of these contaminants in MBR effluent and focus on their subsequent removal by RO. This study has shown that high quality reuse water can be produced from municipal wastewater through the use of an MBR-RO system. The water meets California Title 22 reuse regulations for non-potable applications and US EPA drinking water limits for trihalomethanes (THM) (80 microg/L), haloacetic acids (HAA) (60 microg/L), chlorite (1.0 mg/L), total coliform (not detectable), viruses (not detectable), and nitrate/nitrite (10 mg N/L). However, THM formation (182-689 microg/L) attributed to cleaning of the MBR with chlorine and incomplete removal by subsequent RO treatment resulted in reuse water with THM levels (40.2+/-19.9 microg/L) high enough to present a potential concern when considering drinking water applications. Nitrate levels of up to 3.6 mg N/L, which resulted from incomplete removal by the RO membrane, are also a potential concern. A denitrification step in the MBR should be considered in potable water applications.     

化学氧化消减装置研发及其应急处理氨氮污染水源

以氨氮为污染物,设计研发了一款便捷可拼装式化学氧化消减装置用于应急处理突发环境事件,探讨了氨氮浓度、氧化剂投量、pH值、反应时间对氨氮去除效果的影响,并对装置运行参数包括进出水口高度以及搅拌方式、时间和速度进行了优化。结果表明,在常规pH值条件下,当水中氨氮浓度超标5、10、20倍时分别投加1.7、1.9、15 mL/L次氯酸钠,反应40 min,基本能使水中氨氮浓度降到Ⅲ类地表水限值(1.0 mg/L)以下。化学氧化消减装置最佳运行参数如下:进水口和出水口分别设计在水池有效深度的9/10和1/2处;搅拌方式选用机械搅拌,搅拌速度不低于75r/min,搅拌时间不少于3 min。     

管网内淡化水的化学稳定性及控制方法研究

为研究海水反渗透淡化水在管网中的化学稳定性及控制方法,实现减缓管网腐蚀和改善管网水质的目的,分别建立由PE、塑钢和旧铸铁管组成的3套管网,并模拟淡化水在管网中的输配。研究了淡化水在3套管网中的水质变化规律,并考察了投加CaCO3、将淡化水和水库水混合等措施提高淡化水在管网中化学稳定性的效果。综合化学稳定性判别指数LSI(-3.8～-2.2)、RSI(12.3～14.1)、CCPP(-12.5～-10.5 mg/L)可知,反渗透淡化水具有极严重的腐蚀性;PE管网在减缓管网腐蚀和改善管网水质方面优于塑钢管网;投加CaCO3、将淡化水和水库水混合等措施能显著改善淡化水水质。     

地下水生物除铁效果及其动力学研究

采用生物滤柱进行了地下水除铁的试验研究。当原水中Fe^2＋的质量浓度为4．3mg／L,pH值为6．4～6．6,水温为23～25℃,DO为1．5mg／L,滤速为8m／h时,出水中Fe^2＋〈0．1mg,／L。通过灭菌试验得出,滤柱对铁的去除主要通过生物氧化完成,而非物理化学作用。通过分析不同高度滤层水中铁的含量研究了生物氧化除铁动力学规律,得出铁含量与空床接触时间之间的函数关系。     

A comparative life cycle assessment of hybrid osmotic dilution desalination and established seawater desalination and wastewater reclamation processes

The purpose of this study was to determine the comparative environmental impacts of coupled seawater desalination and water reclamation using a novel hybrid system that consist of an osmotically driven membrane process and established membrane desalination technologies. A comparative life cycle assessment methodology was used to differentiate between a novel hybrid process consisting of forward osmosis (FO) operated in osmotic dilution (ODN) mode and seawater reverse osmosis (SWRO), and two other processes: a stand alone conventional SWRO desalination system, and a combined SWRO and dual barrier impaired water purification system consisting of nanofiltration followed by reverse osmosis. Each process was evaluated using ten baseline impact categories. It was demonstrated that from a life cycle perspective two hurdles exist to further development of the ODN-SWRO process: module design of FO membranes and cleaning intensity of the FO membranes. System optimization analysis revealed that doubling FO membrane packing density, tripling FO membrane permeability, and optimizing system operation, all of which are technically feasible at the time of this publication, could reduce the environmental impact of the hybrid ODN-SWRO process compared to SWRO by more than 25%; yet, novel hybrid nanofiltration-RO treatment of seawater and wastewater can achieve almost similar levels of environmental impact.     

Adsorption combined with ultrafiltration to remove organic matter from seawater

Organic fouling and biofouling are the major severe types of fouling of reverse osmosis (RO) membranes in seawater (SW) desalination. Low pressure membrane filtration such as ultrafiltration (UF) has been developed as a pre-treatment before reverse osmosis. However, UF alone may not be an effective enough pre-treatment because of the existence of low-molecular weight dissolved organic matter in seawater. Therefore, the objective of the present work is to study a hybrid process, powdered activated carbon (PAC) adsorption/UF, with real seawater and to evaluate its performance in terms of organic matter removal and membrane fouling. The effect of different PAC types and concentrations is evaluated. Stream-activated wood-based PAC addition increased marine organic matter removal by up to 70% in some conditions. Moreover, coupling PAC adsorption with UF decreased UF membrane fouling and the fouling occurring during short-term UF was totally reversible. It can be concluded that the hybrid PAC adsorption/UF process performed in crossflow filtration mode is a relevant pre-treatment process before RO desalination, allowing organic matter removal of 75% and showing no flux decline for short-term experiments.     

过冷水动态制冰冷冻法处理酸铜电镀废水研究

电镀中常用的酸铜工艺的水洗废水为强酸性,pH值超过了反渗透膜允许的范围,无法应用反渗透法进行浓缩回用于电镀槽。为此,采用全新的过冷水动态制冰技术,对酸铜工艺电镀水洗废水进行冷冻法处理。结果表明,一次冷冻结晶冰融水的溶质去除率超过90%,可满足一级水洗槽补充水洗水的要求;二次冷冻浓缩液达到电镀槽电镀液浓度的80%,可回用于电镀槽补充电镀液。     

富含高岭土的矿井水处理中存在的问题及应对措施

针对某煤矿富含高岭土的矿井水难以处理的问题,对絮凝剂PAM和PAC的选用及最佳投量进行了试验。结果表明:阳离子PAM的絮凝效果显著优于阴离子、非离子PAM的;原采用的普通型PAC配合PAM不能有效去除高岭土颗粒,而高效液体型PAC在投加量仅为普通型PAC的1/3的条件下,处理出水浊度可降至4.2～8.4 NTU。因此,实际工程确定选用阳离子PAM和高效液体型PAC药剂,投加量分别为0.25、50 mg/L,处理效果得到了显著提高,但反渗透进水SDI值仍常有超过3的情况出现。为此,在一级过滤泵前增加二次絮凝工艺(投加3～5 mg/L的PAC),保证反渗透进水SDI值稳定在3以下,达到了设计要求。