Effects of Ozonation on Molecular Weight Distribution of Humic Substances and Coagulation Processes – A Case Study: The Úzquiza Reservoir Water

In this article the influence of preozonation on the effectiveness of NOM removal via coagulation processes will be studied (focusing on the influence of the calcium hardness) as well as changes in MW (molecular weight) distribution of humic substances caused by ozonation. Additionally, THMFP removal in both ozonation and preozonation-coagulation processes is assessed. Three different types of water have been used in this study: a natural water from the Úzquiza Reservoir (Burgos, Spain), a synthetic water prepared using natural fulvic acids extracted from the Úzquiza Reservoir and a synthetic water prepared using a commercially supplied humic acid. Molecular weights of humic substances were determined using high-performance size exclusion chromatography (HPSEC); average molecular weights calculated for the unozonated humic substances are 4500 Da for the commercial humic acids and 1000 Da for the natural fulvic acids extracted from the Úzquiza Reservoir. Preozonation shifted the molecular weight distribution of humic substances (both humic and fulvic acids) towards lower average molecular weight values. For the natural water from the Úzquiza Reservoir (with low levels of calcium hardness and hydrophobic fraction (humic substances) being the main fraction of NOM), preozonation has a negative effect on the effectiveness of the coagulation process for NOM removal: the percentages of TOC removal via coagulation decrease with increasing ozone dosage; the maximum TOC removal (33%) is achieved for the unozonated water. Also for this water, ozonation reduced 5–25% of THMFP with ozone doses varying from 0.25 to 2.5 mg O₃/L. A preferential THMFP removal, that is to say, higher reduction in THMFP (43%) relative to TOC (28%) is achieved by the coagulation-flocculation process; this also occurs when preozonation is used, independently of ozone dosage.     

Effects of O3, O3/H2O2 and Coagulation on Natural Organic Matter and Arsenic Removal from Typical Northern Serbia Source Water

The objectives of this study were to investigate the effects of ozone and the O₃/H₂O₂ process on FeCl₃ coagulation efficiency for the removal of the high content of natural organic matter (NOM) and arsenic (As) from groundwater (DOC = 9.27 ± 0.92 mg/L; 51.7 ± 16.4 µg As/L). Arsenic and NOM removal mechanisms during coagulation/flocculation are well investigated. However, data concerning arsenic removal in the presence of NOM, which is the subject of this article, are still insufficient. Laboratory and pilot plant test results have shown that the competition of NOM and As for adsorption sites on the coagulant surface have great influence on coagulation/flocculation efficiency for their removal. With both oxidation pre-treatments, arsenic content after the coagulation process was less than 2.0 µg/L in treated water. Application of ozone has a lower influence on coagulation efficacy in terms of DOC reduction, compared to the O₃/H₂O₂ process with the same ozone dose.     

Effect of potassium permanganate dosing position on the performance of coagulation/ultrafiltration combined process

The effects of potassium permanganate(KMnO_4)dosing position on the natural organic matter(NOM)removal as well as membrane fouling were investigated in the coagulation/ultrafiltration combined process.KMnO_4 oxidation altered the NOM characteristics in terms of hydrophobicity and molecular weight,and destroyed humic substances originated from terraneous organisms in raw water.The optimal KMnO_4 dosage was 0.5 mg·L~(-1) in the peroxidation enhanced coagulation process with respect to the dissolved organic carbon(DOC)removal.When KMnO_4 was dosed into both upstream and downstream of coagulation,namely in the proposed twoposition dosing mode,coagulation and KMnO_4 oxidation worked individually on the apparent DOC removal.However,compared to the KMnO_4 addition prior to or after coagulation,the two-position dosing mode dramatically alleviated membrane fouling and reduced fouling irreversibility.This was attributed to the change of NOM characteristics as a result of KMnO_4 addition prior to coagulation and the presence of MnO_2 on membrane surface as a result of KMnO_4 addition prior to ultrafiltration.This work may provide useful information for the application of KMnO_4 oxidation in the coagulation/ultrafiltration combined system.     

电解参数对循环冷却水处理及倒极除垢效果的影响

利用电化学法处理循环冷却水,探究电解参数对处理效果的影响,并探究不同倒极条件对阴极结垢的剥离效果和剥离方式。结果表明,当水质硬度为800 mg/L、Cl-质量浓度为567.2 mg/L、电流密度为10 mA/cm2、水力停留时间为10 min时,硬度去除质量浓度为300 mg/L,Cl-去除质量浓度为140 mg/L,活性氯质量浓度为8.74 mg/L,电流效率为88.44%;在除垢时间为8 min,倒极电流密度为5 mA/cm2的条件下,阴极结垢剥离率达到了94.3%,以物理脱落为主。倒极电流密度过高会造成水质硬度上升,除垢时间过长会造成电极腐蚀。     

水介质分散型阳离子聚丙烯酰胺在制药废水处理中的应用

研究了水介质分散型阳离子聚丙烯酰胺水处理剂在硫酸庆大霉素制药废水处理中的应用.实验室和现场实验的研究结果表明:水介质分散型阳离子聚丙烯酰胺用于硫酸庆大霉素制药废水气浮和压滤的处理工艺中,气浮出水浮渣少,水清,COD由49 200 mg/L下降到11 850 mg/L,去除率达75.9%;SS由75 300 mg/L降至950 mg/L,去除率达98.7%;压滤泥饼含水率小于75%.     

Effect of polyaluminum chloride on enhanced softening for the typical organic-polluted high hardness North-China surface waters

The treatment of organic-polluted high hardness surface water by enhanced softening via precipitation using various coagulants, such as FeCl₃, AlCl₃ and polyaluminum chloride (PACl), was investigated in bench scale experiments. Higher removal of natural organic matter (NOM) (UV₂₅₄ removal reaches about 50%) is achieved by enhanced softening with coagulant addition conditions as compared with conventional coagulation at natural pH or by softening alone without coagulation. It is found that PACl could enhance the formation of Mg(OH)₂ precipitate to remove NOM efficiently at relative lower pH range (pH <10). Under this circumstance, the pH for enhanced softening can be decreased significantly into the practical pH range for treatment plant operation. The efficiency of enhanced softening is affected significantly not only by pH, coagulant type and dose, but also by raw water quality such as NOM characteristics, magnesium content and hardness. NOM with more hydrophobic content and higher molecular weight may be removed more easily in some situations. For water with higher content of Mg²⁺, the inflexion pH for favorable UV₂₅₄ removal is lower. It is of practical value for organic-polluted water with high content of magnesium to be treated by enhanced softening with PACl.     

Colloidal organic matter fouling of UF membranes: role of NOM composition & size

The aim of this study was to fractionate pre-filtered surface water using a 3.5 and a 10 kDa dialysis membrane, and to compare the rate of fouling and the fouling reversibility/irreversibility of the NOM fractions. Trial dialyses (3.5 and 10 kDa) were carried out for 6 and 21 days with pre-filtered surface water using synthetic surface water as dialysate. The aim of the trials was to optimize the dialysis process for NOM fractionation. DOC, Ca²⁺, Mg²⁺, soluble silica and bacteria were monitored at intervals during the dialysis process. Thereafter, the various NOM fractions (with low and high Ca²⁺) were fed to a miniature UF system operated at a constant flux of 138.5 L/m2 h, filtration cycle times of 31.5 min and backwash duration of 1.75 min. A PES/PSV hollow fiber UF membrane (MWCO 100 kDa) with a surface area of 0.0125 m² was employed for the filtration tests (X-Flow). Transmembrane pressure (TMP) and UF feed and permeate (LC-OCD) were monitored at regular intervals. For a dialysate recirculation of 95 L/h, sample to dialysate ratio of 5.2:80 L and a dialysate change frequency of 3 times per 24 h, the shortest duration of dialysis was about 6–7 days for both 3.5 and 10 kDa dialyses membranes. The removal of organic carbon (OC) increased with dialysis duration and MWCO of the bags. The biopolymer fraction increased from 120% to 240% when the duration of dialysis was increased from 6 days (1.1 mg DOC/L, 151 mg Ca/L) to 21 days (0.82 mg DOC/L, 133 mg Ca/L) with the 10 kDa dialysis membrane. The increased biopolymer fraction in the NOM sample that was dialyzed for 21 days resulted in a doubling of the fouling rate from 3.5 to 6.6 mbar/min per mg DOC/L. The other NOM fractions (humics and building blocks) and the Ca/DOC ratio was more or less the same in both NOM samples suggesting that biopolymers were the major cause of UF fouling.     

石灰法处理磷化废水工程实践

介绍了用石灰法处理磷化废水的工程实践，在进水磷酸盐２７３～４８７ｍｇ／Ｌ，Ｚｎ２＋２００ｍｇ／Ｌ左右时，处理出水磷酸盐：００２５～００８１ｍｇ／Ｌ，Ｚｎ２＋：０３６～１１４ｍｇ／Ｌ，去除率分别为９９６％～９９９％和９３８４％～９７３１％     

热解解毒铬渣处理水中磷酸盐的应用

采用600℃和800℃下的两种热解解毒铬渣处理模拟含磷废水,研究了最佳反应条件,并探讨了解毒铬渣除磷的机理。结果表明,热解解毒后铬渣的浸出毒性大幅降低,当磷浓度为50 mg/L时,选择投加量为2.5 g/L,振荡接触时间为2 h。磷分级试验结果表明,解毒铬渣除磷机理主要是溶出金属离子的沉淀作用,从铬渣中溶出的Ca~(2+)含量和平衡溶液pH值对除磷效率有较大影响,铬渣在碱性条件下处理效果较好,适宜处理中性和碱性含磷废水。     

Pilot Study on Pre-Ozonation Enhanced Drinking Water Treatment Process

The enhancement of TOC, COD_Mn, and UV₂₅₄ reduction in the conventional drinking water treatment process by pre-ozonation was investigated in South China on treating dam source water with a pilot plant consisting of pre-ozonation, coagulation-sedimentation, and filtration units. Pre-ozonation enhanced the reduction of NOM in the conventional coagulation-sedimentation and filtration process, and the total removals of UV₂₅₄, COD_Mn and TOC were improved for 34.6%, 18.1% and 15.3%, respectively by the adoption of pre-ozonation under an ozone dose (in ozone consumption base) of 0.85 mg/L. The enhancement of UV₂₅₄ and COD_Mn removals was mainly achieved through direct ozonation on humic substances, and that for TOC removal was achieved through biodegradation in sand filtration. In comparison with the TOC removal of 38%, a removal of 49% was acquired for SDS-THM under a pre-ozonation dose of 0.80 mg/L, indicating the selective removal of THMFP. The reduction of SDS-THM paralleled the reduction of COD_Mn to a significant degree, suggesting that the COD_Mn might be an effective surrogate parameter for SDS-THM if the raw water does not contain the reductive inorganic matters. Although the source water contains 13.2–27.0μg/L bromide, the formation of bromate was negligible when the ozone dose was below 1.0 mg/L.     

生物预处理净水工艺除色度生产应用研究

采用生物接触氧化预处理净水工艺对受污染的水源原水进行了除色度效果研究,结果表明：在正常水温20－28℃的条件下,当污染水源CODMn为6－11mg/L,色度为30－40度和生物预处理净水工艺进行了参数HRT为1.4h,气,水为0.5:1,DO为7－9mg/L时,生物预处理净水工艺对水源原水的脱色率为19％－43％,在较低水温7－16℃的条件下,当污染水源CODMn为6－10mg/L,色度为32－35度和生物预处理净水工艺进行了参数HRT为1.4h,气,水为0.5:1,DO为8-10mg/L时,生物参处理净水工艺可去除水源原水中的色度为13%-22%.     

外加碳源对AOA-SBR工艺脱氮除磷效果的影响

采用厌氧/好氧/缺氧模式运行的SBR工艺处理模拟城市污水,考察外加碳源乙酸钠和污泥水解酸化上清液对其脱氮除磷效果的影响。模拟城市污水,进水水质COD为400 mg/L、氨氮为60 mg/L、磷酸盐为7 mg/L。结果表明:不投加碳源时,系统对COD、氨氮、磷酸盐的去除率分别为90%、91%、82%;乙酸钠投加量为60 mg/L的条件下,外加乙酸钠系统对COD、氨氮、磷酸盐的去除率分别为93%、100%、100%,磷的去除主要是通过好氧聚磷作用;上清液投加量折合进水COD为30 mg/L时,外加污泥水解酸化上清液系统对COD、氨氮、磷酸盐的去除率分别为97%、99%、95%,系统中出现明显的反硝化除磷现象,反硝化除磷占24%。     

改性Zr-Na/Zeolite双功能沸石脱除水溶液中氨氮和磷性能研究

采用氯化钠离子交换和氯氧化锆沉积沉淀两步法改性天然沸石,得到具有脱除水中氨氮和磷的双功能锆钠改性天然沸石（Zr-Na/Zeolite）,考察了不同pH、溶液初始质量浓度和温度下Zr-Na/Zeolite对氨氮溶液、含磷溶液及氮磷共存溶液的吸附情况。结果表明,Zr-Na/Zeolite能够在保持Na改性沸石（Na/Zeolite）优良的吸附氨氮性能的基础上,极大地提高吸附磷的能力。在不同pH下,Zr-Na/Zeolite 吸附氨氮和磷的效果呈现不同的规律。对于氨氮,水溶液pH在4~8时具有最佳吸附性能,最高吸附量达到4.5 mg/g。对于含磷阴离子,脱磷能力随pH的升高而降低,吸附容量从pH=2时的4.71 mg/g降到pH=10时的2.20 mg/g。溶液初始质量浓度从10 mg/L提高到200 mg/L时,氨氮和磷的单位吸附容量分别从1.42和2.46 mg/g提高到11.6和11.8 mg/g,去除率分别从57.0%和98.2%降低到23.2%和23.6%。溶液温度从25 ℃升高到45 ℃,氨氮的吸附容量提高了10%,磷的吸附容量提高了11%。磷和氨氮的吸附过程符合准二级动力学模型。0.1 mol/L NaOH和1.0 mol/L NaCl混合溶液可以再生Zr-Na/Zeolite,循环吸附14次,吸附效率几乎保持不变。     

磷化涂装废水处理工艺改进研究

以具体工程为实例,阐述了化学法除磷工艺中影响除磷效率的要素及其作用方式。进水磷酸盐质量浓度超过20 mg/L,工艺改进前出水磷酸盐质量浓度为1.2 mg/L,经过工艺改进后出水磷酸盐质量浓度降至0.4 mg/L以下,达到了上海市地方标准污水综合排放标准的一级排放标准。     

pH adjustment for seasonal control of UF fouling by natural waters

Natural surface waters in Algarve, Portugal, have important seasonal variations in natural organic matter (NOM) content, that influences ultrafiltration (UF) performance. This paper addresses the evaluation of the pH adjustment for seasonal control of UF fouling at a laboratory scale, using a plate and frame polysulphone membrane of 47 kDa MWCO. Results of two types of natural water (clear water, 3-5 NTU, and turbid water, 33-34.6 NTU) and three different water pH values (acid, neutral and basic) demonstrated that the pH adjustment could be used for seasonal control of UF fouling: when the water has less NOM (in dry periods, clear water), the acid pH will improve the UF performance, while during and after intense rainfall periods (turbid water with high NOM concentration) basic pH will be advantageous, because it minimizes membrane fouling. This behaviour is explained for clear water in terms of charge effects on membrane size. For turbid water, the electrostatic repulsion between membrane surface and NOM and turbidity particles is reduced at pH 4.13 and protonation of the NOM functional groups decreases the hydrodynamic radii of humic substances while increasing their hydrophobicity and their tendency to adsorb. Therefore, a dense fouling layer develops and flux is lower at pH 4.13 than at pH 8.33. These results together with the observed raw water feed concentrations decline and rejection decrease with WRR confirm the extensive adsorption on the membrane enhanced by the moderate hardness cation of this water.     

改性粉煤灰处理含磷废水的研究

采用浓硫酸固相反应法对粉煤灰进行改性用于含磷废水的净化,考察了pH值,吸附剂用量,磷初始浓度,反应时间对净化过程的影响。通过实验发现溶液pH值在4-10范围内对磷的吸附过程影响不显著,改性粉煤灰可以在较宽的pH值范围内进行脱磷处理;随着粉煤灰加入量的增加和初始溶液中磷酸根浓度的降低,磷的净化率逐渐增加。对于含磷50 mg/L的溶液,当粉煤灰的投加量为1.5%时,磷的吸附效率可达99.66%,净化后水中含磷量为0.17 mg/L。改性粉煤灰对水中磷的净化过程速度较快,5 min可达到最大净化率。改性粉煤灰对磷的吸附等温线符合Freudlich方程。     

生物接触氧化法去除微污染水源水中的氨氮

采用生物接触氧化法对北京某水库的微污染水源水进行了除氨效果研究。结果表明,生物接触氧化法具有较好的除氨效果,生物接触氧化原水氨氮的质量浓度在不大于0.234mg/L时,氨氮的月平均去除率为30.8%~72.9%,进水氨氮的质量浓度人工增加至0.126~2.080mg/L时,氨氮去除率最高可达97.4%,平均去除率为71.2%。同时探讨了水温及进水氨氮的质量浓度对氨氮去除效果的影响。     

水解酸化—好氧MBBR耦合Fenton法处理抗生素废水研究

采用水解酸化—好氧移动床生物膜(MBBR)串联Fenton工艺处理抗生素废水,探讨了pH、HRT等对水解酸化以及Fe2 浓度和H2O2投加量对Fenton工艺的影响。实验结果表明,对于COD为6800.62mg/L、B/C<0.3的抗生素废水,当水解段pH和HRT分别为6.5和12h时,挥发酸(VFA)质量浓度为931.75mg/L,COD去除率为26.59%,此时水解酸化—好氧段出水COD为1229.80mg/L,COD总去除率为81.92%。再经Fenton工艺深度处理,当Fe2 最佳投加质量浓度为240mg/L,H2O2投加量为3.19mL/L时,总COD去除率可达97.38%,最终出水COD为178.50mg/L,达到制药工业废水排放标准。