Drinking water treatment using a submerged internal-circulation membrane coagulation reactor coupled with permanganate oxidation

A submerged internal circulating membrane coagulation reactor(MCR) was used to treat surface water to produce drinking water. Polyaluminum chloride(PACl) was used as coagulant,and a hydrophilic polyvinylidene fluoride(PVDF) submerged hollow fiber microfiltration membrane was employed. The influences of trans-membrane pressure(TMP), zeta potential(ZP) of the suspended particles in raw water, and KMnO_4 dosing on water flux and the removal of turbidity and organic matter were systematically investigated. Continuous bench-scale experiments showed that the permeate quality of the MCR satisfied the requirement for a centralized water supply, according to the Standards for Drinking Water Quality of China(GB 5749-2006), as evaluated by turbidity(1 NTU) and total organic carbon(TOC)(5 mg/L)measurements. Besides water flux, the removal of turbidity, TOC and dissolved organic carbon(DOC) in the raw water also increased with increasing TMP in the range of 0.01–0.05 MPa. High ZP induced by PACl, such as 5–9 mV, led to an increase in the number of fine and total particles in the MCR, and consequently caused serious membrane fouling and high permeate turbidity.However, the removal of TOC and DOC increased with increasing ZP. A slightly positive ZP, such as 1–2 mV, corresponding to charge neutralization coagulation, was favorable for membrane fouling control. Moreover, dosing with KMnO_4 could further improve the removal of turbidity and DOC, thereby mitigating membrane fouling. The results are helpful for the application of the MCR in producing drinking water and also beneficial to the research and application of other coagulation and membrane separation hybrid processes.     

Reduction of DOM fractions and their trihalomethane formation potential in surface river water by in-line coagulation with ceramic membrane filtration

This research was aimed at investigating the reduction of DOM fractions and their trihalomethane formation potential （THMFP） by in-line coagulation with 0.1 μm ceramic membrane filtration. The combination of ceramic membrane filtration with a coagulation process is an alternative technology which can be applied to enhance conventional coagulation processes in the field of water treatment and drinking water production. The Ping River water （high turbidity water） was selected as the raw surface water because it is currently the main raw water source for water supply production in the urban and rural areas of Chiang Mai Province. From the investigation, the results showed that the highest percent reductions of DOC, UV-254, and THMFP （47.6%, 71.0%, and 67.4%, respectively） were achieved from in-line coagulation with ceramic membrane filtration at polyaluminum chloride dosage 40 mg/L. Resin adsorption techniques were employed to characterize the DOM in raw surface water and filtered water. The results showed that the use of a ceramic membrane with in-line coagulation was able to most efficiently reduce the hydrophobic fraction （HPOA） （68.5%）, which was then followed by the hydrophilic fraction （HPIA） （49.3%）. The greater mass DOC reduction of these two fractions provided the highest THMFP reductions （55.1% and 37.2%, respectively）. Furthermore, the in-line coagulation with ceramic membrane filtration was able to reduce the hydrophobic （HPOB） fraction which is characterized by high reactivity toward THM formation. The percent reduction of mass DOC and THMFP of HPOB by in-line coagulation with ceramic membrane filtration was 45.9% and 48.0%, respectively.     

Investigating the coagulation of non-proteinaceous algal organic matter: Optimizing coagulation performance and identification of removal mechanisms

The removal of algal organic matter(AOM) is a growing concern for the water treatment industry worldwide. The current study investigates coagulation of non-proteinaceous AOM(AOM after protein separation), which has been minimally explored compared with proteinaceous fractions. Jar tests with either aluminum sulphate(alum) or polyaluminium chloride(PACl) were performed at doses of 0.2–3.0 mg Al per 1 mg of dissolved organic carbon in the p H range 3.0–10.5. Additionally, non-proteinaceous matter was characterized in terms of charge, molecular weight and carbohydrate content to assess the treatability of its different fractions. Results showed that only up to 25% of non-proteinaceous AOM can be removed by coagulation under optimized conditions. The optimal coagulation p H(6.6–8.0 for alum and 7.5–9.0 for PACl) and low surface charge of the removed fraction indicated that the prevailing coagulation mechanism was adsorption of non-proteinaceous matter onto aluminum hydroxide precipitates. The lowest residual Al concentrations were achieved in very narrow p H ranges, especially in the case of PACl. High-molecular weight saccharidelike organics were amenable to coagulation compared to low-molecular weight( 3 k Da)substances. Their high content in non-proteinaceous matter(about 67%) was the reason for its low removal. Comparison with our previous studies implies that proteinaceous and nonproteinaceous matter is coagulated under different conditions due to the employment of diverse coagulation mechanisms. The study suggests that further research should focus on the removal of low-molecular weight AOM, reluctant to coagulate, with other treatment processes to minimize its detrimental effect on water safety.     

Prediction of DOM removal of low specific UV absorbance surface waters using HPSEC combined with peak fitting

High performance size exclusion chromatography (HPSEC) is used in water quality research primarily to determine the molecular weight distribution of the dissolved organic matter (DOM), but by applying peak fitting to the chromatogram, this technique can also be used as a tool to model and predict DOM removal. Six low specific UV absorbance (SUVA) source waters were treated using coagulation with alum and both the source and treated water samples were analysed using HPSEC. By comparing the molecular weight profiles of the source and treated waters, it was established that several DOM components were not effectively removed by alum coagulation even after high dosage alum treatment. A peak-fitting technique was applied based on the concept of linking the character (molecular weight profile) of the recalcitrant organics in the treated water with those of the source water. This was then applied to predict DOM treatability by determining the areas of the peaks which were assigned to removable organics from the source water molecular weight profile after peak fitting, and this technique quantified the removable and non-removable organics. The prediction was compared with the actual dissolved organic carbon (DOC) removal determined from jar testing and showed good agreement, with variance between 2% and 10%. This confirmed that this prediction approach, which was originally developed for high SUVA waters, can also be applied successfully to predict DOC removal in low SUVA waters.     

Coagulation of micro-polluted Pearl River water with IPF-PACIs

Water samples collected from early March 2001 to the end of April 2002 at the branch of Pearl River around the Guangzhou City were analyzed for its micro-polluted characteristics. The coagulation behavior of polyaluminum chlorides(PACIs) was then examined focusing on the effect of primary water quality and speciation distribution. The results showed that PACIs exhibit better coagulation efficiency than alum in accordance with the different speciation.The turbidity removal property of PACIs is evidently better than alum at low dosage. While in neutral zone(about 6.5--7.5), the turbidity removal of PACIs decreases owing to the restabilization of particles at higher dosage. The organic matters in raw water exhibit marked influence on coagulation. In acidic zone, organic matters complex with polymer species and promote the formation of flocs. With an increase in pH, the complexation of organics with polymer species gradually decreases, and the removal of organics mainly depends on adsorption. The effect is evidently improved with the raise of B value.     

Full-scale study of removal effect on Cyclops of zooplankton with chlorine dioxide

Cyclops of zooplankton propagated excessively in eutrophic water body and could not be effectively inactivated by the conventional disinfections process like chlorination due to its stronger resistance to oxidation. In this paper, a full-scale study of chlorine dioxide preoxidation cooperating with routine clarification process for Cyclops removal was conducted in a waterworks. The experimental results were compared with that of the existing prechlorination process in several aspects: including the Cyclops removal efficiencies of water samples taken from the outlets of sedimentation tank and sand filter and the security of drinking water and so on. The results showed that chlorine dioxide might be more effective to inactivate Cyclops than chlorine and Cyclops could be thoroughly removed from water by pre-dosing chlorine dioxide process. The GC-MS examination and Ames test further showed that the sort and amount of organic substance in the treated water by chlorine dioxide preoxidation were evidently less than that of prechlorination and the mutagenicity of drinking water treated by pre-dosing chlorine dioxide was substantially reduced compared with prechlorination.     

Effects of Ca(OH)2 assisted aluminum sulfate coagulation on the removal of humic acid and the formation potentials of tri-halomethanes and haloacetic acids in chlorination

The effects of addition of calcium hydroxide on aluminum sulphate(or alum) coagulation for removal of natural organic matter(NOM) and its subsequent effect on the formation potentials of two major types of regulated disinfection byproducts(DBPs),haloacetic acids(HAAs) and trihalomethanes(THMs),have been examined.The results revealed several noteworthy phenomena.At the optimal coagulation pH(i.e.6),the coagulation behavior of NOM water solutions versus alum dose,showed large variation and a consequent great change in the formation potentials of the DBPs at certain coagulant doses.However,with addition of a relatively small amount of Ca(OH) 2,although the zeta potential of coagulated flocs remained almost the same,NOM removal became more consistent with alum dose.Importantly,also the detrimental effect of charge reversal on NOM removal at the low coagulant dose disappeared.This resulted in a steady decrease in the formation potentials of DBPs as a function of the coagulant dose.Moreover,the addition of Ca(OH) 2 broadened the pH range of alum coagulation and promoted further reduction of the formation potentials of the DBPs.The enhancement effects of Ca(OH) 2 assisted alum coagulation are especially pronounced at pH 7 and 8.Finally,synchronous fluorescence spectra showed that the reduction in DBPs formation potential by Ca(OH) 2-assisted alum coagulation was connected to an enhanced removal of small hydrophobic and hydrophilic HA molecules.Ca(OH) 2-assistance of alum coagulation appeared to increase substantially the removal of the hydrophilic HA fraction responsible for HAAs formation,prompting further reduction of HAA formation potentials.     

Preferential binding between intracellular organic matters and Al13 polymer to enhance coagulation performance

Coagulation is the best available method for removing intracellular organic matter (IOM), which is released from algae cells and is an important precursor to disinfection by-products in drinking water treatment. To gain insight into the best strategy to optimize IOM removal, the coagulation performance of two Al salts, i.e., aluminum chloride (AlCl₃) and polyaluminum chloride (PACl, containing 81.2% Al₁₃), was investigated to illuminate the effect of Al species distribution on IOM removal. PACl showed better removal efficiency than AlCl₃ with regard to the removal of turbidity and dissolved organic carbon (DOC), owing to the higher charge neutralization effect and greater stability of pre-formed Al₁₃ species. High pressure size exclusion chromatography analysis indicated that the superiority of PACl in DOC removal could be ascribed to the higher binding affinity between Al₁₃ polymer and the low and medium molecular weight (MW) fractions of IOM. The results of differential log-transformed absorbance at 254 and 350?nm indicated more significant formation of complexes between AlCl₃ and IOM, which benefits the removal of tryptophan-like proteins thereafter. Additionally, PACl showed more significant superiority compared to AlCl₃ in the removal of < 5?kDa and hydrophilic fractions, which are widely viewed as the most difficult to remove by coagulation. This study provides insight into the interactions between Al species and IOM, and advances the optimization of coagulation for the removal of IOM in eutrophic water.     

Interference of iron as a coagulant on MIB removal by powdered activated carbon adsorption for low turbidity waters

Powered activated carbon (PAC) is widely used in water treatment plants to minimize odors in drinking water. This study investigated the removal of 2-methylisoborneol (MIB) by PAC adsorption, combined with coagulation using iron as a coagulant. The adsorption and coagulation process were studied through different case scenarios of jar tests. The analysis evaluated the effect of PAC dosing in the liquid phase immediately before or after the coagulant addition. Ferric sulphate was used as the coagulant with dosages from 10 to 30 mg/L, and PAC dosages varied from 10 to 40 mg/L. The highest MIB removal efficiency (about 70%) was achieved without the coagulant addition and with the highest PAC dosage (40 mg/L). Lower MIB removal efficiencies were observed in the presence of coagulant, showing a clear interference of the iron precipitate or coagulant in the adsorption process. The degree of interference of the coagulation process in the MIB removal was proportional to the ratio of ferric hydroxide mass to the PAC mass. For both cases of PAC dosing, upstream and downstream of the coagulant injection point, the MIB removal efficiency was similar. However, MIB removal efficiency was 15% lower when compared with experiments without the coagulant application. This interference in the MIB adsorption occurs potentially because the coagulant coats the surface of the carbon and interferes with the MIB coming in contact with the carbon’s surface and pores. This constraint requires an increase of the PAC dosage to provide the same efficiency observed without coagulation.     

Characterization of dissolved organic matter as N-nitrosamine precursors based on hydrophobicity, molecular weight and fluorescence

It is very important to identify the dominant precursors for N-nitrosamine formation from bulk organic matter, to enhance the understanding of N-nitrosamine formation pathways in water treatment plants and allow the development of practical treatment technologies. In this study, dissolved organic matter (DOM) from two source waters was fractionated with XAD resins and ultra- filtration membranes. The N-nitrosamine formation potential (FP) (ng of N-nitrosamines formed per mg of dissolved organic carbon (DOC)) from raw water and each fraction were measured and correlated with the fluorescence excitation-emission matrix (EEM), molecular weight (MW) and other assays. The results showed that the hydrophilic fraction had N-nitrosamine FP 1.3 to 3.5 times higher than the hydrophobic fraction from both source waters. The DOM fraction with low MW was the dominant fraction in these two source waters and contributed more precursors for N-nitrosamine formation than the larger MW fraction. The EEM spectra indicated there were notable amounts of soluble microbial products (SMPs) and aromatic proteins in the two studied rivers, which probably originated from wastewater discharge. The SMPs tended to be more closely correlated with N-nitrosodimethylamine formation potential than the other DOM components. Higher N-nitrosamine FP were also related to fractions with lower DOC/DON ratios and lower SUVA 254 values.     

生物脱氮系统中无厌氧释磷的生物除磷工艺

采用2个工作容积为6L的SBR反应器(1#和2#)分别进行人工废水的脱氮试验研究,其中1#进水是以醋酸钠为碳源,2#以淀粉为碳源,2个反应器进水的COD、氨氮、磷酸盐和硝氮浓度一致.2个反应器均按缺氧76min-好氧294min交替的模式运行·在COD/NO-3N比为8.76:1(400 mg·L-1:45.67 mg·L-1)和15.03:1(400 mg·L-1:26.61 mg·L-1)2种水质条件下.考察了2个反应器对COD、氮和磷的脱除情况.结果表明.2种碳氮比下,1#反应器为传统的硝化.反硝化生物脱氮.对硝酸盐和COD具有较好的脱除效果,对磷基本不能去除;2#反应器在缺氧段发生反硝化脱氮作用,在好氧时段发生硝化作用,同时伴有明显的磷去除.这种现象稳定持续,致使反应器中污泥浓度明显增加.结合pH、DO等环境因素的分析,判定这是一种新型的非传统生物除磷现象.     

温度对生物强化除磷工艺反硝化除磷效果的影响

以处理城市污水的中试规模生物强化除磷A2/O活性污泥工艺系统为研究对象,考察了温度对系统COD去除和脱氮除磷效果的影响,特别是温度对活性污泥反硝化除磷性能的影响.结果表明,当温度从(30.9±0.8)℃降低到(9.1±0.6)℃时,A2/O系统的脱氮除磷效果显著下降,系统对TN和TP的污泥去除负荷明显下降.通过污泥反硝化除磷活性实验发现,随着温度的降低,系统中活性污泥的最大厌氧释磷速率、最大好氧吸磷速率和最大缺氧吸磷速率都降低.活性污泥中反硝化除磷菌(DPB)占聚磷菌(PAOs)总量的比例随温度降低稍有下降,但平均值仍维持在47.5％左右.用阿伦尼乌斯公式对实验结果进行拟合,得到系统中活性污泥聚磷菌厌氧释磷反应活化能Ea1为148.0 kJ· mol-1,聚磷菌好氧吸磷反应活化能Ea2为228.8 kJ·mol-1,发生在缺氧条件下反硝化除磷菌的吸磷反应活化能Ea3为315.8 kJ·mol-1.对不同温度下污泥絮体粒径分析结果表明,随温度降低,粒径分布更加集中,系统中活性污泥絮体颗粒平均粒径减小,不利于污泥絮体内部反硝化除磷缺氧微环境的形成.     

添加剂和湿法除尘主要参数对炭黑去除效率的影响

选取十六烷基三甲基溴化胺(CTAB)、十二烷基苯磺酸钠(SDBS)、月桂醇聚氧乙烯(9)醚(AEO-9)和壬基酚聚氧乙烯醚(OP-10)4种表面活性剂配制成吸收液,采用伞形罩洗涤器对燃煤窑炉黑烟进行湿法除尘净化实验,探讨添加剂种类、入口含尘浓度(Cin)、入口风速(u)和液气比(L/G)参数的不同对炭黑(BC)去除效率(η)的影响,结合压降(ΔP,Pa)的变化提出高效脱黑的可行方案.结果表明,在实验条件同为Cin=2g·m-3、u=12m·s-1和L/G=0.2L·m-3条件下,4种吸收液脱黑效果差别不大,AEO-9吸收液具有略明显的优势,炭黑去除效率可达到99.5%(0.06mmol·L-1,AEO-9);在u=12m·s-1和L/G=0.2L·m-3条件下,Cin=5g·m-3时更利于洗涤器对黑烟的净化,AEO-9吸收液的炭黑去除效率近乎100%,ΔP变化不大;入口风速的变化对炭黑去除效率和压降的影响比较明显,当Cin和L/G分别为2g·m-3、0.2L·m-3时,最佳入口风速为12～14m·s-1,炭黑去除效率保持在99%以上;最佳操作液气比可控制在0.2～0.4L·m-3.     

Nitrogen removal in sequencing batch reactor

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强化生物除磷系统除磷特性对水温变化响应的试验研究

以富集聚磷菌(Phosphorus Accumulating Organisms,PAOs)的活性污泥为基础,研究了强化生物除磷(Enhanced Biological Phosphorus Removal,EBPR)系统的磷酸盐去除特性对温度升高和恢复的响应.结果表明,水温从20℃分别上升到25、30和35℃3种状态持续运行8d后,EBPR系统厌氧释磷和好氧吸磷受到明显抑制,系统磷酸盐去除率显著下降.20℃对照处理系统的磷酸盐去除率约为80.3%,而35℃的升温处理其磷酸盐去除率为0,说明此系统处于崩溃状态.当所有处理系统水温恢复到20℃运行后,25℃处理系统经过1d的恢复,磷酸盐去除率可恢复至80%,30℃处理系统经过5d的恢复,磷酸盐去除率可达80%,而35℃处理系统则无法恢复到原来的状态.此外,水温上升到25、30和35℃分别运行8d后,系统内厌氧胞内聚合物(PHA)的合成量和好氧PHA的消耗量随着反应器内水温的升高而增加.20℃对照处理系统的厌氧PHA合成量约为0.03mg·mg-1(以污泥计,下同),好氧PHA消耗量约为0.06mg·mg-1;35℃升温处理系统的厌氧PHA合成量约为0.11mg·mg-1,好氧PHA消耗量约为0.12mg·mg-1.当所有处理水温恢复到20℃运行后,升温处理的反应器内厌氧PHA合成量和好氧PHA消耗量都明显降低.     

猪场废水脱氮与沼气脱硫耦联反应器的启动

采用鼓泡反应器研究猪场废水脱氮与沼气脱硫耦联反应器的启动,比较了启动过程中不接种污泥、接种厌氧污泥及接种好氧污泥对启动时间及效能的影响.结果表明,接种好氧污泥的反应器在第32d时氮硫同步去除率达到60%以上;不接种污泥的反应器氮硫同步去除率达到60%需要36d;而接种厌氧污泥的反应器则需要50d.成功启动后,在温度为30～32℃、空塔停留时间为9.75min、水力停留时间为4.78d、沼气中H2S浓度为1.70 8·m-3左右及进水NOx-N浓度为109 mg·L-1的条件下,不接种污泥反应器,接种厌氧污泥反应器和接种好氧污泥反应器的NOx-N去除率分别97%、91%、99%,硫化氢的去除率分别稳定在82%、78%和86%左右.接种好氧污泥的反应器硫化氢去除率最高可达92.3%.运行稳定后,3个反应器均可实现按相对固定的比例同时去除硫和氮,废水脱氮与沼气脱硫得到了很好耦联,在1个反应器中可以同时实现废水脱氮与沼气脱硫.     

Nitrogen removal from coal gasification wastewater by activated carbon technologies combined with short-cut nitrogen removal process

A system combining granular activated carbon and powdered activated carbon technologies along with shortcut biological nitrogen removal （GAC-PACT-SBNR） was developed to enhance total nitrogen （TN） removal for anaerobically treated coal gasification wastewater with less need for external carbon resources. The TN removal efficiency in SBNR was significantly improved by introducing the effluent from the GAC process into SBNR during the anoxic stage, with removal percentage increasing from 43.8%49.6% to 68.8%-75.8%. However, the TN removal rate decreased with the progressive deterioration of GAC adsorption. After adding activated sludge to the GAG compartment, the granular carbon had a longer service-life and the demand for external carbon resources became lower. Eventually, the TN removal rate in SBNR was almost constant at approx. 43.3%, as compared to approx. 20.0% before seeding with sludge. In addition, the production of some alkalinity during the denitrification resulted in a net savings in alkalinity requirements for the nitrification reaction and refractory chemical oxygen demand （COD） degradation by autotrophic bacteria in SBNR under oxic conditions. PACT showed excellent resilience to increasing organic loadings. The microbial community analysis revealed that the PACT had a greater variety of bacterial taxons and the dominant species associated with the three compartments were in good agreement with the removal of typical pollutants. The study demonstrated that pre-adsorption by the GAC-sludge process could be a technically and economically feasible method to enhance TN removal in coal gasification wastewater （CGW）.     

活性藻系统对氮、磷及有机物的去除研究

报道了实验室条件下利用活性藻反应系统对合成污水中N、P、CODCr和BOD5等的去除 效果.在26±2℃条件下,当停留时间为24h时,TN, TP, COD_Cr 和BOD₅ 的平均去除率分别为 7 7.62%, 33.23%, 90.89% 和 95.77%.当进水负荷加大一倍、停留时间相应缩短、光强、水温 同时减弱和降低时,该系统对TP 和BOD₅的处理效果受到明显影响,对 COD_Cr的处理效果影响 不大,运行条件的改变基本上不影响活性藻系统对TN的处理效果,两种运行条件下,TN的平均 去除率分别为77.62%和77.86%.     

Genotoxicity removal of reclaimed water during ozonation

Genotoxicity in wastewater and reclaimed water now is gaining increased attention because of genotoxins' potential damage to the ecosystem and human health. The effect of ozonation on genotoxicity in reclaimed water was investigated. It was found that ozonation decreased the genotoxicy dramatically in three tertiary treatment plants. In the further batch ozonation experiment in laboratory,secondary effluent sample used exhibited the genotoxicity of(41.1 ± 4.1) μg 4NQO/L. Ozonation with a dose of 10 mg O3/L completely removed the genotoxicity in secondary effluent. However,after ozonation, the dissolved organic carbonvalue of the sample didn't change much but the specific ultraviolet absorbance(SUVA) value dropped sharply. With the help of Fourier transform infrared spectroscopy, ozonation was found to change chemical aliphatic carbon and C–O of the dissolved arganic matter, which might be the reason of the significant decreases of SUVA and genotoxicity.     

铁型反硝化脱氮技术研究进展

传统反硝化工艺是非常有效的废水脱氮技术,具有反应快、效率高等优点,但受废水中有机碳源浓度影响较大.废水中碳源不足不能满足生物反硝化脱氮的需求且会导致总氮(TN)去除率偏低,而投加外源有机碳源会提高处理成本,极易造成二次污染,因而传统反硝化工艺对低碳氮比(C/N)废水脱氮处理具有一定局限性.铁型反硝化脱氮技术作为自养反硝...