Oil-Refinery Wastewater Treatment Aiming Reuse by Advanced Oxidation Processes (AOPs) Combined with Biological Activated Carbon (BAC)

The treatment of a refinery wastewater by Advanced Oxidation Processes (AOP) coupled with Biological Activated Carbon (BAC) was investigated aiming to generate water for reuse. O₃/UV and H₂O₂/UV processes were employed to oxidize the organic matter and the BAC process to remove residual organic matter from the AOP effluent. AOP promoted oxidation of recalcitrant organic matter as observed by moderate drops on the treated wastewater absorbance (31–79%) and TOC values (10–18%). BAC filters showed to be effective, reaching average efficiencies of 65% in a sufficiently long period of operation (84 days), while GAC filters were saturated after 28 days. Effluent TOC values in the range of 4 to 8.5 mg/L were achieved by the combined treatment (H₂O₂/UV + BAC), allowing water reuse.     

Systematic Approach to Quantify Adsorption and Biodegradation Capacities on Biological Activated Carbon Following Ozonation

The goal of this research was to develop a systematic approach to quantify adsorption and biodegradation capacities on biological activated carbon (BAC). The role of absorption and biodegradation on BAC was studied using a continuous column. Several media, i.e., granular activated carbon (GAC), seeded glass bead and seeded GAC, and a target compound (p-hydroxybenzoic acid) were selected. Before breakthrough, the effluent of the GAC column contained a small amount of p-hydroxybenzoic acid that contributed the greatest amount of organic carbon to the effluent of the glass bead column, which suggests that adsorption should be the prevailing mechanism for removal the p-hydroxybenzoic acid, and biodegradation should be responsible for reducing the ozonation intermediates. Also, the bioactivity approach (biomass respiration potential, BRP) of BAC can not only reveal the importance of biodegradation mechanisms for the intermediates of ozonation, but also quantify the extent of the adsorption or biodegradation reaction occurring on BAC.     

Removal efficiencies of endocrine disrupting chemicals by coagulation/flocculation, ozonation, powdered/granular activated carbon adsorption, and chlorination

Removal efficiencies of endocrine disrupting chemicals (EDCs), bisphenol A and nonylphenol, during various types of water treatment processes were evaluated extensively using laboratory- and pilot-scale experiments. The specific processes of interest were coagulation/flocculation sedimentation/filtration (conventional water treatment process), powdered activated carbon (PAC), granular activated carbon (GAC), ozonation and chlorination. Batch sorption tests, coagulation tests, and ozone oxidation tests were also performed at higher concentrations with 14 EDCs including bisphenol A. The conventional water treatment process had very low removal efficiencies (0 to 7%) for all the EDCs except DEHP, DBP and DEP that were removed by 53%, 49%, and 46%, respectively. Ozonation at 1 mgO₃/ L removed 60% of bisphenol A and 89% of nonylphenol, while chlorination at 1 mg/L removed 58% and 5%, respectively. When ozone and chlorine doses were 4 and 5 mg/L, respectively, both EDCs were not detected. PAC removal efficiencies ranged from 15% to 40% at 3 to 10 mg/L of PAC with a contact time of 15 minutes. In the high concentration batch sorption tests, EDC removal efficiencies by PAC were closely related to octanol-water partition coefficient (K_ow). GAC adsorption was very effective water treatment process. The type and service time of GAC did not affect EDC removal efficiencies. The combination of ozonation and GAC in series appears to remove EDCs effectively to safe levels while conventional water treatment could not.     

Adsorption and Microbiological Mechanisms for Removal of Natural Organics in Granular Activated Carbon Columns

Performance data for GAC columns treating surface water are analyzed to determine the relative importance of physical adsorption and biological activity, with and without pre-ozonation. Kinetic and equilibrium adsorption parameters for the source water are used in the Homogeneous Surface Diffusion model to predict GAC performance over 83 weeks. The model underestimates removal of TOC for ozonated and unozonated streams by 46% and 28%, respectively, which is attributed to omission of biological removal in the model.     

Behavior Of Glyoxal During Granular Activated Carbon Treatment

Glyoxal, which was the strong mutagen formed by ozonation of humic substances, was treated with granular activated carbon (GAC) and the behavior of glyoxal was investigated. Glyoxal itself was adsorbed well on GAC at pH 5–7. But, glyoxal increased by GAC treatment of ozonated humic substances when the ozone dose was insufficient to decolorize the humic substances. The precursors of glyoxal may be among other ozonated products which may be changed to glyoxal on GAC.     

Ozone: A Means of Stimulating Biological Activated Carbon Reactors

To reduce the formation of chlorination byproducts in drinking water, the European strategy consists in developing techniques for the removal of organic matter. No chlorine is added to the water until the end of the treatment line, allowing a great reduction of the chlorine dose applied. Delaying the chlorination also improves the biological assimilation of organics within the filters. Identification of the basic properties (i.e., molecular weight, biodegradability) of the molecules which react with chlorine shows that the combination of ozone and biological activated carbon (BAC) filtration is an efficient and economical technique for the removal of these undesirable byproducts. More and more, drinking water suppliers are faced with the worrisome problem of chlorinated byproducts. This concern was prompted largely by the degradation of raw waters. Chlorinated byproducts are caused by the effect of chlorine on organic matter dissolved in water.     

Biodergradability and GAC Adsorbability of Micropollutants by Preozonation

In order to evaluate the effect of preozonation on GAC adsorbability and biodegradability and to discuss the performance of BAC, three kinds of batch experiments have been conducted, using humic acid as the test substance. Conclusively, it is recognized that preozonation evidently improves the biodegradability of humic acid, but the equilibrium adsorption constant k, is not changed. However, the adsorption rate is greatly improved. Based on these results and continuous experiments, the characteristics of the removal mechanism of organics by a BAC filter and a GAC filter are compared.     

Biological Filtration for Ozone and Chlorine DBP Removal

This paper presents results from a water treatment pilot testing program in Winnipeg, Canada (pop. 650,000) which evaluated a DAF/ozone/deep bed filtration process. As part of the testing program, biological filtration using GAC and anthracite media was assessed for the removal of ozone DBPs and background chlorine DBPs (due to upstream chlorination of the source water). The results were used to evaluate the effectiveness of biological filtration for DBP removal.

High filtration rates were tested in this study. The 2.1m deep filters were run at a hydraulic loading rate (HLR) of 35 m/h with an empty bed contact time (EBCT) of only 3.6 minutes.

The important findings of this work are

?The high-rate biologically active carbon (BAC) filters met the objective of controlling ozone DBPs. These results confirm that high rate, low EBCT filters can provide significant biodegradation. Anthracite biofilters provided significantly less removal of ozone DBPs.

?The high rate BAC filters showed significant reduction of background HAAs. BAC reduced the background HAAs to below the long-term target of 30 μg/L. Anthracite biofilters did not exhibit HAA removal.

?Biological filtration with either media was ineffective for background THM removal. The long-term target of 40 μg/L could not be achieved without GAC adsorption.     

Degradation of Refractory Organic Pollutants by Catalytic Ozonation—Activated Carbon and Mn-Loaded Activated Carbon as Catalysts

A novel catalyst for the ozonation process was prepared by loading manganese on the granular activated carbon (GAC). Nitrobenzene was used as a model refractory organic micropollutant in this study. The catalytic activity of GAC and the Mn-loaded GAC were studied respectively. The removal efficiency of nitrobenzene by Mn-loaded GAC catalyzed ozonation could reach 34.2–49.9%, with the oxidation efficiency being about 1.5–2.0 times higher than that achieved in GAC catalyzed ozonation and 2.0–3.0 times higher than that achieved by ozonation alone. The effect of pH and the t -butanol on the GAC/ozone process was discussed. The optimum condition for preparing the catalyst was studied.     

臭氧活性炭联合工艺去除微污染水中有机物

采用臭氧活性炭联合工艺(O3+BAC)对以长江为水源的某水厂砂滤水进行深度处理。试验结果表明,该工艺对水中有机物有稳定的去除效果,在臭氧投加量为1mg/L,活性炭空床接触时间为8.6min时,对CODMn,UV254,DOC,THMEP(三氯甲烷生成势)和AOC(可同化有机碳)的平均去除率分别为32%,40%,22%,19%,7%。在DOC较低的情况下,三氯甲烷生成势与UV254有较好的正相关性。     

The Effect Of Preozonation,Ozone/Hydrogen Peroxide Treatment,And Nanofiltration On The Removal Of Organic Matter From Drinking Water

Pilot scale experiments were performed to evaluate the ability of ozonation, ozone/hydrogen peroxide treatment and nanofiltration to reduce levels of organic matter, mutagenicity, total adsorbable halogens, color and turbidity from purified and bank-filtered surface water rich with humic material.

Ozonation and ozone/hydrogen peroxide decreased the amount of organic material from drinking water by about 20 percent measured as TOC and COD_Mn. Color and turbidity level reductions were 49 and 11 percent, respectively. Ozonation reduced the AOX concentrations formed during postchlorination from 150 μgL^?1 to 75 μgL^?1. The addition of hydrogen peroxide further improved the removal to 37 and 26 μgL^?1 depending on the ratio of H₂O₂/O₃. The mutagenicity reduction followed the same pattern: without ozonation the chlorination-derived mutagenicity was 1,450 net revertant L^?1 after the ozonation 700 and after the H₂O₂/O₃ treatment from <100 to 400 net revertant L^?1 depending on the H₂O₂/O₃ ratio. Nanofiltration appeared to be the most effective way to remove organic material. The removal of TOC was 68%, COD_M 72%, color 90%, turbidity 68%, AOX 88%, and mutagenicity 85%.     

常规处理与深度处理工艺对南京长江原水中有机物去除效能比较

以长江南京段原水为研究对象,通过常规处理及深度处理工艺(强化过滤工艺和生物活性炭工艺)对长江南京段水源水中有机物的去除效能进行对比研究。结果表明常规工艺对CODMn、UV254、DOC及BDOC的去除率分别为30%、41%、27%及25%。强化常规工艺和生物活性炭工艺各指标的去除率分别为34%和52%、48%和50%、37%和40%及74%和82%。强化过滤工艺及生物活性炭工艺对1,2,4-三氯苯的去除效果明显,能显著提高出水水质。常规工艺对MW大于5 kDa的有机物去除效果明显,强化过滤工艺对MW小于1 kDa的有机物去除率大于25%,生物活性炭工艺对各个分子量区间的去除效果都比较好,特别是对原水中占多数的MW小于1 kDa的有机物去除率大于30%。     

Adsorption of Bromate From Aqueous Solutions by Modified Granular Activated Carbon: Batch and Column Tests

Bromate by-product formation during ozonation of bromide-containing potable water has aroused widespread concern. In this study, cetylpyridinium chloride was selected to modify two different kinds of granular activated carbon (GAC) to improve their bromate adsorption capacity. The adsorption characteristics of modified GAC were studied by batch and column tests, with results suggesting greatly improved bromate adsorption ability: the saturation capacities for bromate were >7 times for modified GAC than for GAC under the experimental conditions used. This enhancement in adsorptive capacity is likely due to an increase in basic functional groups, because the saturated adsorption capacity of bromate on the GAC is positively correlated with the basic functional groups. The increase of the basic functional groups accelerates OH- dissociation from the GAC surface and protonation of the GAC surface, thus resulting in the enhancement in adsorptive capacity. The modified GAC was relatively immune to the impact of pH change over a broad range. Both the Yoon-Nelson model and the Thomas model fit well the breakthrough curves of bromate adsorbed by modified and unmodified GAC under different conditions. Our results provide insight into the sorption process of bromate onto modified GAC.     

Evaluation Of Ozone/Biological Treatment For Disinfection Byproducts Control And Biologically Stable Water

Impacts of ozonation followed by biological filtration on the formation of disinfection byproducts and the production of biologically stable water were studied on pilot plant and full-scale at two U.S. locations (Oakland, CA and Tampa, FL). Also evaluated is a method to estimate bacterial regrowth potential by comparing it to assimilable organic carbon (AOC) measurements. At both locations, settled plant water is diverted to the pilot plant where it is split into two parallel trains. One train is ozonated, then Filtered through anthracite/sand dual media followed by GAC or through a GAC/sand dual media filter. The other train (control) is identical except that the water is not ozonated. The full scale plants have sedimentation, ozonation, then GAC/sand filtration.     

Performance of Granular Activated Carbon (GAC) Adsorption and Biofiltration in the Treatment of Biologically Treated Sewage Effluent

Abstract

In this study, the performance of GAC adsorption and biofiltration systems in treating biological treated sewage effluent (BTSE) was evaluated in terms of organic removal efficiency, organic fractions, and molecular weight distribution (MW) of organic matter (OM) removed. The GAC biofilter removed 23.5% and 61% of the hydrophobic fractions and hydrophilic fractions of OM in the BTSE respectively. MW distribution studies of GAC filter and GAC adsorption revealed the following: Hydrophobic fraction of the effluent showed a peak at 345 dalton after GAC biofiltration and 256 dalton after GAC adsorption, whereas, with hydrophilic fractions, peaks at 46,178 and 345 daltons were observed after GAC biofiltration and peaks at 46,178 and 256 daltons after GAC adsorption. Transphilic fraction showed the peaks at 12,783 dalton with GAC biofiltration, and 1,463 dalton with GAC adsorption. The performance of the GAC biofilter was successfully mathematically modelled.     

MECHANISMS OF ACTIVATED CARBON BIOREMOVAL

The removal of an organic azo dye-stuff particularly resistant to biodegradation was studied in an activated sludge pilot plant on the basis of the PACT process. Different runs were carried out by adding to the oxidation basin both adsorbent solids (granular activated carbon (GAC), and powdered activated carbon (PAC)) or practically non-adsorbent solid (semisilica fire brick crushed particles (SFB).) Biological removal of the dye-stuff was observed with GAC or PAC addition, whereas no removal was observed with the fire brick particles.

Comparison of the results obtained with either GAC or PAC with those from the SFB non-adsorbent solid showed carbon bioregeneration, existing only in the presence of adsorbent solids, to be probably the fundamental mechanism governing biological dye removal. The specific removal rate obtained with carbons, probably dependent on many physical and biological phenomena, was interpreted with saturation type equations typical of biological phenomena. The apparent adsorption capacities at the end of the runs with GAC and PAC were respectively 5 times and 17 times higher than those corresponding to the GAC and PAC physical adsorption isotherms.

Carbon physical adsorption capacity seemed to play a fundamental role: the dye biological removal rate obtained with PAC (whose physical adsorption capacity was about 2.5 times higher than that of GAC) turned out to be 3.5 times higher, on the average, than that determined with GAC.     

接种厌氧絮状污泥的厌氧氨氧化反应器的快速启动

厌氧氨氧化技术因其节能、运行费用低、不需添加有机物等优点而备受关注,但反应器启动慢是该技术面临的瓶颈问题。为了加速厌氧氨氧化反应器的启动,该研究在两个不同阶段中先后在同一UASB反应器中接种絮状污泥和添加颗粒活性炭,以含NH4+-N和NO2--N的人工配水为进水,进行连续试验,并在试验过程中调整运行参数,最终添加活性炭的絮状污泥反应器在运行85 d后成功启动厌氧氨氧化过程,总氮去除率稳定在80%-90%。结果表明在使用活性炭吸附法固定化时,反应器启动迅速,活性炭可以成为厌氧氨氧化菌的理想载体。     

Characteristics of adsorption and biodegradation of dissolved organic carbon in biological activated carbon pilot plant

The dissolved organic carbon (DOC) properties for the influent of the BAC pilot plant have shown a 42% biodegradable fraction and a 58% non-biodegradable fraction. The biodegradable dissolved organic carbon (BDOC) was degraded entirely by biodegradation; the removal efficiency was 65–83%. The BDOC removal efficiency at empty bed contact time (EBCT) 15 minutes was larger than at EBCT 8 minutes. At increasing EBCT, a more slowly biodegradable fraction of BDOC (H₂) was utilized. The non-biodegradable dissolved organic carbon (NBDOC) was removed mostly by adsorption, and the removal amount was 24–58%. Therefore, the DOC was removed by adsorption and biodegradation; the removal efficiency by biodegradation was 31%, and that by adsorption was 24%. The breakthrough behaviors of DOC and NBDOC continued to be saturated as the bed volume increased, whereas the BDOC breakthrough curves maintained a certain ratio according to the bed volume.     

Combined Use of Ozone and Granular Activated Carbon (GAC) in Potable Water Treatment; Effects on GAC Quality After Reactivation

Common processes in potable water treatment regarding dissolved organics removal (natural organic matter, NOM, and organic micropollutants, OMP) include oxidation techniques – like ozonation -and adsorption onto granular activated carbon (GAC). This paper deals with combined ozonation and GAC filtration. Effects on water quality are discussed: partial oxidation of dissolved organics by ozone, leading to changing adsorption behavior and enhanced biodegradation in GAC columns. Special emphasis is laid on long term effects of ozone on GAC quality after several thermal reactivations. Long term experience indicates that ozonation prior to GAC filtration, leading to moderate ozone concentrations in the GAC influent, does not influence GAC quality negatively, even after more than ten reactivation cycles.     

生物活性炭对含吲哚和吡啶废水的去除研究

考察了三种不同生物活性炭对含吲哚和吡啶的模拟废水的去除效果。三种生物活性炭由沥青基球形活性炭（PSAC）、煤质柱状炭（EAC）和椰壳颗粒炭（GAC）循环挂膜制得,分别简称B-PSAC、B-EAC和B-GAC。生物活性炭的运行可分为三个阶段,活性炭的吸附阶段、活性炭的挂膜阶段以及生物活性炭阶段,考察指标为吲哚和吡啶的浓度。结果表明：三种生物活性炭对吲哚的去除率都在96%以上;B-GAC对吡啶的去除率最好,一般在90%以上,B-PSAC次之,约为75%,B-EAC去除效果最差。