Effects of activated carbon on the reactions of combined chlorine with phenols

In the presence of ammonia, prechlorination in drinking water treatment results in contact of combined chlorine (monochloramine) with activated carbon, which is used to remove organic compounds from water. Monochloramine reacts very slowly with phenolic compounds in aqueous solution, giving low yields of chlorinated phenols. When monochloramine reacts with phenols adsorbed on granular activated carbon (GAC), however, several oxidized products, principally hydroxylated biphenyls, are formed. Some of the hydroxylated biphenyls are chlorinated (hydroxylated PCBs). Their formation is particularly important because of their potential toxicity. Such compounds are major reaction products from chlorophenol, but they are also formed in small amounts from nonchlorinated phenols. Most of the monochloramine-GAC-phenolic compound reaction products are also produced in similar reactions with free chlorine, indicating that similar reaction mechanisms (free radical mechanisms) take place on carbon's surface. No organic compounds are produced from the reaction of monochloramine with GAC alone.     

从分子质量的变化分析臭氧活性炭工艺

为了解臭氧活性炭工艺的机理并优化运行条件,采用臭氧活性炭处理黄浦江原水,分析了原水及经不同工艺单元处理后溶解性有机物 (DOM)分子质量 (MW)的变化。结果表明:黄浦江原水中的DOM主要为小分子有机物;臭氧对大分子有机物的氧化分解作用明显强于对小分子有机物的氧化作用;MW<1ku的有机物经臭氧氧化后则表现出不同程度的增加;混凝、沉淀、过滤对MW>3ku的大分子有机物去除效果较好,而对MW<3ku的小分子有机物去除效果较差;生物活性炭单元能有效去除MW为 3~1ku和MW<1ku的小分子有机物;臭氧氧化与活性炭吸附在去除不同MW有机物的过程中有很好的互补性,从而使该工艺能有效去除原水中的DOM。     

活性炭吸附用于城市污水地下回灌技术的研究

通过静态吸附试验比较与Ｃｒｉｔｔｅｎｄｅｎ计算模型分析,选择ＧＨ－１６型粒状活性炭对北京高碑店污水处理厂二级出水进行深度处理试验。结果表明：ＧＨ－１６型活性炭的净化效果存在阈值,约２５％的ＤＯＣ不能被吸附,不被吸附的主要是分子量〉３０００ｕ的有机物。对以ＵＶ２５４表征的有机物去除效果最好,分子量〈１０００ｕ的弱极性有机物易被微孔吸附且吸附容量,对以ＡＯＸ表征的极性有机物去除效果较差。二级出水经活性     

活性炭/纳滤工艺深度处理污水厂尾水的研究

以某污水处理厂的尾水为研究对象,进行了活性炭/纳滤组合工艺深度处理污水处理厂尾水中微量有机物的研究。结果表明,该组合工艺对CODMn、TOC、UV254均有较好的去除效果,平均去除率分别达到42.09%、69.54%和78.53%,出水的平均浓度分别为5.90mg/L、1.93mg/L和0.04cm-1。纳滤膜对邻苯二甲酸酯类物质具有较好的截留效果,对邻苯二甲酸二丁酯、邻苯二甲酸二乙酯和邻苯二甲酸二乙基己基酯的平均去除率分别为78.91%、78.95%和70.69%。     

The effect of pretreatment to ultrafiltration of biologically treated sewage effluent: a detailed effluent organic matter (EfOM) characterization

Ultrafiltration alone can remove only a portion of the effluent organic matter (EfOM) from biologically treated sewage effluent (BTSE). Use of pretreatment not only improves the EfOM removal but also reduces the membrane fouling. In this research, NTR 7410 ultrafiltration membrane was employed to remove EfOM from BTSE. Different pretreatments namely FeCl(3) flocculation and powder activated carbon adsorption were evaluated. The highest removal of organic matter was observed when flocculation followed by adsorption was used as pretreatment. The flocculation and adsorption removed 68.5% and 71.4% of hydrophobic organics, respectively. The molecular weight (MW) of the EfOM in BTSE ranged from 300 to about 400000 Da. After the flocculation pretreatment, the majority of large MW organic matter was removed. The pretreatment of the flocculation followed by adsorption led to very high removal of both small and large organic matter. Further, this pretreatment led to practically no filtration flux decline.     

Disinfection by-product formation after biologically assisted GAC treatment of water supplies with different bromide and DOC content

Chlorination of drinking water in the presence of bromide and dissolved organic carbon (DOC) leads to the formation of brominated and chlorinated disinfection by-products (DBP). The concentration of bromide ions in the raw water is a significant factor in the speciation of DBP formed, and causes shifts in trihalomethane (THM) formation from chlorinated to brominated species. Drinking water treatment techniques that remove organic contaminants without affecting bromide ion concentrations cause increases in the brominated THM. For the present study, three water supplies containing different DOC and ambient bromide concentrations were filtered through biologically assisted granular activated carbon (BGAC). Similar to adsorption and coagulation treatment, this treatment does not remove bromide from drinking water; also, THMFP (trihalomethane formation potential) analysis indicated that the chlorinated effluent contained higher concentrations of brominated THM in comparison to the influent. Although BGAC may increase the brominated THM, which may be more toxic than the chlorinated THM, the overall reduction of THMFP by DOC removal far exceeds this negative change, thereby producing a much less toxic finished drinking water. This work is part of a study to make high DOC surface waters on the Canadian prairie safe and palatable for small volume users (individuals or small communities).     

Selected organic pesticides, behavior and removal from domestic wastewater by chemical and physical processes

A study was conducted to evaluate the effectiveness of chemical and physical wastewater treatment processes in removing selected organic pesticides from domestic wastewater. A 3785 m³ day⁻¹ (1 MGD) nominal capacity pilot plant consisting of biological, chemical and physical units was used for the study. Biologically treated domestic wastewater was subjected to chemical coagulation, multimedia filtration, and activated carbon adsorption. Eight sequences of treatment processes were studied. Influent and effluent samples were analyzed for selected chlorinated hydrocarbon pesticides and chlorophenoxy herbicides using EC-GC. Confirmatory tests such as TLC, extraction of p-value and CPU-MS-GC were applied on selected samples. Results of the study provided qualitative and quantitative evaluation of the performance of the treatment processes studied. Qualitatively characteristic profiles consisting of a limited number of refractory organic residues were detected as peaks on EC chromatograms of extracts from each treatment unit. Thirteen compounds were confirmed in the biologically treated wastewater. These included DDT and its metabolites, aldrin, dieldrin, and 2,4-D alkyl esters and salts. Concentration levels of these compounds in wastewaters were at the ng l⁻¹ (part per trillion) level. Chemical coagulation with alum-lime or lime-ferric chloride was found to effect slight reduction of the organic residues detected on EC chromatograms. Quantitatively only DDT compounds were more completely removed by chemical treatment. Multimedia filters had no discernible effect in removing organic residues from biologically and chemically treated wastewater. Activated carbon columns were found to be the most effective means for removing the refractory organic residues detected. However, breakthrough of some organic residues was noted after usage of the carbon for over 1 year. The overall results of the study showed that application of several sequences of treatment processes on domestic wastewater can produce a high quality effluent which is virtually free from EC detectable organic residues.     

Complexation of copper in the effluent of a sewage treatment plant and an estimate of its influence on toxicity to coho salmon

Measurements by cupric ion electrode of the complexing capacity of the effluent from a sewage treatment plant (STPE) averaged 0.300 mg 1⁻¹. Of the complexed Cu 67% was due to compounds of 10,000 MW. Organic compounds removable by activated carbon composed 88% of the total organic carbon and were responsible for 87% of the complexation. Complexation of Cu²⁺ by STPE diminishes the toxicity from total Cu to juvenile coho salmon; the LC₅₀ was 0.164 mg 1⁻¹ for river water vs 0.286 mg 1⁻¹ for 40% STPE. The LC₅₀ of Cu²⁺ was approximately the same (0.017 vs 0.022 mg 1⁻¹) in both matrices; this species thus appears to play a toxic role. The mean survival time in diluted STPE with added Cu was inversely proportional to the Cu²⁺ concentration.     

Ozonation effect on natural organic matter adsorption and biodegradation - Application to a membrane bioreactor containing activated carbon for drinking water production

More stringent legislation on dissolved organic matter (DOM) urges the drinking water industry to improve in DOM removal, especially when applied to water with high dissolved organic carbon (DOC) contents and low turbidity. To improve conventional processes currently used in drinking water treatment plants (DWTPs), the performances of a hybrid membrane bioreactor containing fluidised activated carbon were investigated at the DWTP of Rennes. Preliminary results showed that the residual DOC was the major part of the non-biodegradable fraction. In order to increase the global efficiency, an upstream oxidation step was added to the process. Ozone was chosen to break large molecules and increase their biodegradability. The first step consisted of carrying out lab-scale experiments in order to optimise the necessary ozone dose by measuring the process yield, in terms of biodegradable dissolved organic carbon (BDOC). Secondly, activated carbon adsorption of the DOC present in ozonated water was quantified. The whole process was tested in a pilot unit under field conditions at the DWTP of Rennes (France). Lab-scale experiments confirmed that ozonation increases the BDOC fraction, reduces the aromaticity of the DOC and produces small size organic compounds. Adsorption tests led to the conclusion that activated carbon unexpectedly removes BDOC first. Finally, the pilot unit results revealed an additional BDOC removal (from 0.10 to 0.15 mg L⁻¹) of dissolved organic carbon from the raw water considered.     

颗粒活性炭吸附对预臭氧后微污染原水水质影响研究

在不同的预臭氧浓度条件下处理微污染原水,考察了颗粒活性灰（GAC）吸附对处理后水样水质的影响.选择化学需氧量（CODMn）、溶解性有机碳（DOC）、生物可降解溶解性有机碳（BDOC）、UV254和氨氮（NH;-N）含量及有机物分子量分布作为考察吸附效果的检测指标.结果表明,在静态吸附时间达到5天时,颗粒活性炭吸附曲线开始趋于平缓,吸附时间超过5天之后吸附趋于饱和;预臭氧含量为2.5 mg/L时,颗粒活性炭对有机物的吸附效果最佳,对CODMn、DOC、BDOC的去除率分别为53.2％,63.2％和36.2％;在不同预臭氧处理条件下,颗粒活性炭对NH;-N的吸附效果并未表现出较大的差异,吸附去除率约为5％;颗粒活性炭优先吸附水中分子量＞ 10kDa的有机物,其次为分子量＜1 kDa的有机物.     

粉末炭去除饮用水中土霉味物质的影响因素研究

采用粉末活性炭（PAC）去除饮用水中2-甲基异莰醇（MIB）、2,4,6-三氯茴萫醚（TCA）、2-异丙基-3-甲氧基吡嗪（IPMP）和2-异丁基-3-甲氧基吡嗪（IBMP）等4种常见的土霉味物质,研究了PAC种类、PAC投加量、嗅味物质的初始浓度、余氯、水质等因素对PAC去除土霉味物质的影响。结果表明,PAC吸附对嗅味物质的去除主要发生在前1 h内;煤质PAC对MIB有更高的去除率;在一定的吸附时间和活性炭投加量下,PAC对痕量嗅味物质的去除率与其初始浓度无关;余氯和有机物的存在降低了PAC对嗅味物质的吸附容量,水质对去除嗅味物质也有很大的影响。     

Formation and removal of mutagenic activity during drinking water preparation

The influence of different treatment processes on the mutagenic activity (Ames test) and some chemical parameters in water were investigated in a few waterworks. Application of a chlorine treatment generally increased the direct and promutagenic activity, but the extent increase proved to be dependent on the type of water chlorinated. The use of ozone in the preparation of drinking water decreased the mutagenic activity in the water. The extent reduction was also dependent on the type of water ozonated. Dune filtration greatly reduced the mutagenic activity. Slow sand filtration could not be evaluated, because of the toxicity of the organic concentrates for the bacterial strains. Granular activated carbon filters, in operation for about 1 year, reduced the mutagenic activity below the detection level. A similar filter which has operated for more than 1.5 years in a pilot plant, showed a breakthrough of mutagenic activity, suggesting that carbon filters are able to remove organic mutagens for a limited period. The results of the chemical parameters measured before and after the different treatment processes showed that none of these parameters were a reliable indicator for the mutagenic activity.     

两种碳基材料对二级出水中有机物的去除特性

针对活性炭与活性焦两种碳基吸附材料,分别开展静态吸附与动态过滤实验,考察了两者对城镇再生水厂二级出水中有机物的去除效果。结果表明:活性焦介孔及大孔丰富,对应孔体积为0.436 cm³/g,为活性炭的1.6倍;准二级动力学模型更适用于两种材料对COD的吸附动力学拟合,活性焦动力学吸附速率常数k₂为活性炭的2倍;水温为22℃时,活性焦与活性炭对COD的Langmuir饱和吸附量分别为230.38、94.14 mg/g。在近4个月的连续运行中,活性焦滤柱对有机物的去除效果全程优于活性炭滤柱,尽管两滤柱在由单纯吸附向生物吸附降解转化的过程中对有机物的去除率有所降低,但对COD的去除率仍可分别稳定在28.43%和22.26%。活性焦颗粒与活性炭颗粒表面ATP含量最高分别为7032.94、5753.52 ng/g。此外,活性焦滤柱对1~10 ku有机物组分,以及腐殖酸类物质、溶解性微生物代谢产物等不同荧光特性有机物均有较好的去除效果。与活性炭相比,活性焦对再生水厂二级出水中有机物的去除效果更优。     

Elimination of organophosphate ester flame retardants and plasticizers in drinking water purification

Organophosphate ester flame retardants and plasticizers like tris-(2-chloro-, 1-methyl-ethyl)phosphate (TCPP), tris-(2-chloro-, 1-chloromethyl-ethyl)phosphate (TDCP), tris-(2-chloroethyl)phosphate (TCEP), tributylphosphates, triphenylphosphate (TPP), ethylhexyldiphenylphosphate (EHDPP) and tris-(butoxyethyl)phosphate (TBEP) have been studied in diverse processes for drinking water purification. The elimination efficiency of these different treatment processes, e.g., biological active slow underground passage, soil passage and technical treatment processes such as ozonization or multilayer and activated carbon filtration have been studied in three waterworks in the catchment area of the river Ruhr. In the untreated surface water the concentrations of the chlorinated organophosphates ranged 50-150 ng L(-1) TCPP, 10-130 ng L(-1) TCEP and 10-40 ng L(-1) TDCP. The amounts of the non-chlorinated alkylphosphates were in the same order of magnitude (40 ng L(-1) of the tributylphosphates, 170 ng L(-1) of TBEP and 10 ng L(-1) TPP) depending on weather and water flow. EHDPP was detected in the range of 1 ng L(-1). After the drinking water purification process in all waterworks in this study, the concentrations of the selected substances were below the respective limit of quantification (0.3-3 ng L(-1)). While activated carbon filtration as well as extended passage through soil (10-15 days residence time) were effective in eliminating all selected compounds, ozonization and multilayer filtration did not contribute to the elimination of the chlorinated compounds. The elimination effect of slow underground passage combined with soil passage concerning the halogenated compounds seemed to depend on the hydraulic residence time.     

Formation, adsorption and separation of high molecular weight disinfection byproducts resulting from chlorination of aquatic humic substances

A significant portion of the unidentified disinfection byproducts (DBPs) in chlorinated drinking water can be attributed to high molecular weight (MW)-chlorinated DBPs (above 500 Da) that may have adverse health effects. In this work, issues on the formation, adsorption and separation of high MW-chlorinated DBPs were investigated by introducing radioactive (36)Cl into humic substance samples. The results show that the amount of high MW-chlorinated DBPs during chlorination decreased with the increase of contact time from 1 to 120 h, increased with the increase of pH from 5.5 to 9.5, and was less in the ultrafiltered samples from Suwannee River fulvic acid than from Suwannee River humic acid. The high MW-chlorinated DBPs were found to be effectively adsorbed by activated carbon and be possibly reduced to Cl(-) by activated carbon, but not to be readily desorbed from the activated carbon. Those high MW-chlorinated DBPs were demonstrated to be incapable of resolution into discrete peaks by any of the three liquid chromatography columns studied. The significant implications of these results are discussed.     

The impact of aromatic compounds on the efficiency of biofiltration through activated carbon

The article has investigated the sorption process on activated carbon of aromatic compounds with different functional groups (o- nitrophenol, o-aminophenol, aniline). We have showed the possibility of assessing the efficiency of biofiltration depending on such factors as the variation of the Gibbs free energy of adsorption of sorbates and the value of the specific load of an organic substance on activated carbon. For determining a contribution of the biological component to the total efficiency of the process we used the value of the ratio between the specific dynamic adsorption to the specific equilibrium adsorption at uniform loads in terms of the organic matter on biologically activated carbon.     

Electrochemical oxidation of phenolic wastes with boron-doped diamond anodes

The electrochemical oxidation of several phenolic aqueous wastes has been studied using a bench-scale plant with a single-compartment electrochemical flow cell. Boron-doped diamond materials were used as the anode. Complete mineralization of the waste was obtained in the treatment of phenols not substituted with chlorine or nitrogen. Chlorinated phenolic compounds were transformed into carbon dioxide; volatile organochlorinated compounds and nitro-substituted phenols deal with the formation of polymeric materials. These polymeric materials behave as final products or treatment intermediates depending on the nature of the initial pollutant. The removal of nitro- or the chloro-group from the phenolic molecule seems to be one of the first stages in the treatment. Non-nitrogenated or chlorinated carboxylic acids have been found to be the main intermediates in the electrochemical oxidation of all the phenolic compounds tested. The efficiencies of the process depend strongly on the concentration of organic pollutants and on their nature, and not on the current density, at least in the operation range studied.     

Simultaneous colour and DON removal from sewage treatment plant effluent: Alum coagulation of melanoidin

The aim of this study was to detect and characterise melanoidin in sewage treatment plant (STP) effluent, and to study the ability of alum coagulation to remove the colour and dissolved organic nitrogen (DON) associated with melanoidin. The melanoidin is non-biodegradable due to the complex cyclic based structure and thus it directly contributes to effluent nitrogen concentrations from the sewage treatment plant (STP). Lowering of effluent total nitrogen limits and the link between colour and chlorinated disinfection by-products have therefore driven a need to understand the structure, properties and treatability of DON species found in STP effluent.The focus of this paper is the refractory coloured, organic nitrogen compound melanoidin. Wetalla STP effluent has relatively high colour (170 mg-PtCo L⁻¹) and DON (2.5 mg L⁻¹) for a biological nutrient removal STP, owing to an industrial supply of melanoidin containing molasses fermentation wastewater. Alum coagulation jar tests were performed on synthetic melanoidin solution, STP effluent containing melanoidin (Wetalla, Toowoomba, Australia) and STP effluent free of melanoidin (Merrimac, Gold Coast, Australia) to examine the treatability of melanoidin and its associated colour and DON content when present in STP effluent.The removal of melanoidin from STP effluent resulted in significant colour and DON reduction. An alum dose of 30 mg L⁻¹ as aluminium was sufficient to reach maximum removal of colour (75%), DON (42%) and dissolved organic carbon (DOC) (30%) present in melanoidin containing STP effluent. Alum was shown to preferentially remove DON with a molecular weight >10 kDa over small molecular weight DON. Fluorescence excitation-emission matrix examination of the humic compounds present in the STP effluent indicated that melanoidin type humic compounds were more readily removed by alum coagulation than other humic compounds.     

太湖源水中蓝藻腐败产物的去除工艺研究

采用超滤膜法对太湖源水中的蓝藻腐败产物进行了分子质量分级,研究了混凝、超滤、臭氧氧化及活性炭吸附等工艺对腐败产物的去除效果.结果表明,以CODMn表征的有机物主要分布在分子质量>40 ku和<10 ku的区间,致嗅物质主要集中在10-40 ku的区间,以UV254表征的有机物主要分布在分子质量<40 ku的区间.混凝、超滤特别适于去除分子质量较大的有机物,对致嗅有机物的去除效果不明显;臭氧氧化能显著去除致嗅有机物,同时还将大分子有机物氧化为小分子有机物;活性炭对小分子有机物的吸附效果明显,能够有效去除分子质量<10 ku的有机物.将这四种工艺进行组合能充分发挥各自的作用,保障饮用水的安全性.     

Sorption of chlorinated C1- and C2-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment

The sorption of chlorinated C₁- and C₂-hydrocarbons and monocyclic aromatic hydrocarbons on sea sediment was studied with a miscible displacement technique. Detection was done either by on-line UV-detection or off-line GC-analysis. Equilibrium partitioning coefficients between the salt water phase and the marine sediment were determined for 11 compounds by fitting their breakthrough curves to a local sorption equilibrium model. Based on the obtained partitioning coefficients and on the measurement of the organic carbon content of the sediment, the sorption into the organic carbon fraction was considered. Log K_oc data (K_oc = organic carbon-water partitioning coefficient) were calculated. A linear relationship between the log K_oc values and the log K_ow data (K_ow = octanol-water partitioning coefficient) was found (r = 0.94, n = 11). However, the sorption was lower than expected from the log K_ow data. Finally, the implications of the experimental results for the sorption behaviour of the compounds in the marine environment were evaluated. It was concluded that the sea sediment does not act as an important sink for these anthropogenic compounds.