O3-BAC Process Research Articles

Removal of dissolved organic matter via a combination of UV/persulfate oxidation and biological activated carbon (BAC) process

The combination process of UV/peroxydisulfate (UV/PDS) oxidation and BAC (UV/PDS-BAC) is examined as an advanced treatment for conventional drinking water treatment through a continuous flow experimental apparatus with actual sand filter effluent as feed water. The effect of three key parameters (UV dosage, PDS dosage, and water temperature) on dissolved organic matter (DOM) is evaluated via long-term monitoring data. The removal behavior of DOM in the UV/PDS-BAC process is also compared with that in the O3-BAC process. Further, this study delves into the mechanisms behind the enhanced DOM removal achieved by UV/PDS-BAC. The achieved results reveal that impressive removal rates of 42.1 % for total organic carbon (TOC) and 62.9 % for UV254 could be achieved in the presence of specific conditions: a UV input of 200 mJ/cm2 and a PDS dosage of 0.5 mM. The efficiency of DOM removal by UV/PDS-BAC exhibits a positive correlation with the UV dosage ranging from 50 to 200 mJ/cm2, and the water temperature in the range of 4–30 ℃. While increasing the PDS dosage from 0.01 to 0.5 mM results in improved DOM removal, any further increase yields reduced removal efficiency. In comparison, subjected to similar operating conditions, UV/PDS-BAC outperforms O3-BAC in removing DOM. The superior DOM removal achieved by the UV/PDS-BAC process can be essentially attributed to several factors: firstly, it exhibits excellent mineralization capacity for low molecular weight organics (<1 kDa) and leads to increased biodegradable fraction of organics by oxidatively degrading DOM with a molecular weight >3 kDa. Secondly, the appropriate exposure of activated carbon pores is chiefly maintained by suitably controlling the biomass. Lastly, the enhanced biodegradability of BAC influent stimulated the growth of bacteria proficient in degrading DOM.

Impact of biological activated carbon filtration and backwashing on the behaviour of PFASs in drinking water treatment plants

PFASs are present in surface water, tap water and even commercial drinking water and pose a risk to human health. In this study, the treatment efficiency of 14 PFASs was studied in a large drinking water treatment plant (DWTP) using Taihu Lake as the source, and it was found that the ozone/biological activated carbon (O3-BAC) process was the most effective process for the removal of PFASs in DWTPs. For the O3-BAC process, there were differences in the removal of PFASs by BACs (1,4,7,13 years) of different ages. The sterilization experiments revealed that for GAC, its physical adsorption capacity reached saturation after one year, while for BAC with mature biofilms, biosorption was the main mechanism for the removal of PFASs. The abundance of Alphaproteobacteria and Gammaproteobacteria in biofilms was positively correlated with the age of the BAC. The microbial community with higher abundance is beneficial to the biodegradation of organic matter and thus provides more active sites for the adsorption of PFASs. PFASs can leak in the early stage of filtration after backwashing, so it is necessary to pay close attention to the influent and effluent concentrations of PFASs during biofilm maturation after backwashing.

A new process to further remove dissolved organic matter and disinfection by-product formation potential during drinking water treatment.

Biological activated carbon (BAC) will produce soluble microbial products (SMPs), which affect effluent quality. To clarify the mechanism by which BAC affects effluent water quality, the processes of a drinking water plant in Jiangsu Province were investigated. It was found that during the O3-BAC process, although ozonation could remove dissolved organic matter (DOC) to a certain extent, the DOC increased from 4.44 to 4.47mg/L after BAC. Dissolved organic matter (DOM) in effluent from different processes was divided into five fractions based on hydrophilicity and hydrophobicity by resin fractionation. Through fluorescence excitation-emission matrix (EEM) spectroscopy combined with DOC analysis, it was found that SMPs are mainly included in transitional hydrophilic neutral (TPIN) fraction, which was the main cause of the DOC increase. Therefore, a new combined process was designed to remove TPIN effectively by coagulation after biological treatment, and found that coagulation had a good removal rate (13.2%) on TPIN. The trihalomethane formation potential (THMFP) of TPIN could be reduced effectively by 44.9% after coagulation. Compared with the old process, the new combined process had a higher removal rate (14.2-30.0%) of DOC, as well as a greater reduction of THMFP (29.0-78.6%) and haloacetic acid formation potential (HAAFP) (46.4-75.3%). This study aims to reveal the mechanism by which SMPs affect effluent water quality and exacerbate health risks, and to propose a solution to provide theoretical support for the design and optimization of drinking water treatment processes.

Co-occurrence of odor-causing dioxanes and dioxolanes with bis(2-chloro-1-methylethyl) ether in Huangpu River source water and fates in O3-BAC process

In recent years, dioxanes and dioxolanes have been intermittently detected in water environment and have caused several offensive drinking water odor incidents worldwide. In this study, the co-occurrence of eight dioxanes, twelve dioxolanes and bis(2-chloro-1-methylethyl) ether was investigated in Huangpu River watershed to explore potential sources and contributions to septic/chemical odor. Totally 8 dioxanes and dioxolanes were detected in river, with 1,4-dioxane (212 −8310 ng/L) and 2,5,5-trimethyl-1,3-dioxane (n.d.−133 ng/L) as the dominated dioxanes, 2-methyl-1,3-dioxolane (49.5 −2278 ng/L), 2-ethy-4-methyl-1,3-dioxolane (n.d.−167 ng/L) and 1,3-dioxolane (n.d.−225 ng/L) as the major dioxolanes. Bis(2-chloro-1-methylethyl) ether was detected (n.d.−1094 ng/L) with significant correlation with dioxanes and dioxolanes, illustrating their similar polyester resin-related industrial origins. 2-Ethy-4-methyl-1,3-dioxolane, 2,5,5-trimethyl-1,3-dioxane and bis(2-chloro-1-methylethyl) ether with individual maximum odor activity value above 1, should contribute to septic/chemical odor in Huangpu River water. The increased concentrations of these chemicals in the downstream of some industrial areas illustrated the association with industrial discharge. Fates in a waterworks using the river water as source water were further explored. The adopting ozone-biological activated carbon treatment could permit a relatively high removal for bis(2-chloro-1-methylethyl) ether and 2,5,5-trimethyl-1,3-dioxane (> 80%), while limited removal for other chemicals. This study provides valuable information for the management of drinking source water and water environment.

Pilot study on the treatment of lake water with algae by ultrafiltration–ozone–biologically activated carbon

Abstract For the treatment of lake water with algae, the coagulation–ultrafiltration–ozone–biologically activated carbon (CUF–O3–BAC) integrated process was first used to treat East Taihu Lake water in China, aiming at evaluating the removal efficiencies of algae, permanganate index (CODMn), UV254, NH3-N and disinfection by-products (DBPs) precursors. In addition, the long-term performance of the membrane operation under the fluxes of 60, 70, 80 and 90 L/(m2·h) was also investigated, and kinetic models were established. The experimental results showed that the integrated process had positive impaction of algae, CODMn, UV254 and NH3-N removal, and the removal rates were 95.89 ± 1.52, 76.18 ± 4.38, 72.06 ± 4.72 and 81.31 ± 6.71%, respectively. The CUF process was prone to increase the formation potentials of DBPs. Although ozone could reduce the formation risks of chlorinated trihalomethanes (THMs) to a certain extent, it is ineffective to reduce those of brominated THMs and haloacetic acids (HAA5). However, the CUF–O3–BAC process was an effective technology for the removal of THMs and HAA5 precursors in drinking water treatment. Finally, it was found that the relationship between transmembrane pressure (TMP) and time conformed to the first-order and second-order kinetic models, and the linear fitting coefficients were all above 90%.

Pilot Study on the Combination of Different Pre-Treatments with Nanofiltration for Efficiently Restraining Membrane Fouling While Providing High-Quality Drinking Water.

Nanofiltration (NF) is a promising post-treatment technology for providing high-quality drinking water. However, membrane fouling remains a challenge to long-term NF in providing high-quality drinking water. Herein, we found that coupling pre-treatments (sand filtration (SF) and ozone–biological activated carbon (O3-BAC)) and NF is a potent tactic against membrane fouling while achieving high-quality drinking water. The pilot results showed that using SF+O3-BAC pre-treated water as the feed water resulted in a lower but a slowly rising transmembrane pressure (TMP) in NF post-treatment, whereas an opposite observation was found when using SF pre-treated water as the feed water. High-performance size-exclusion chromatography (HPSEC) and three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy determined that the O3-BAC process changed the characteristic of dissolved organic matter (DOM), probably by removing the DOM of lower apparent molecular weight (LMW) and decreasing the biodegradability of water. Moreover, amino acids and tyrosine-like substances which were significantly related to medium and small molecule organics were found as the key foulants to membrane fouling. In addition, the accumulation of powdered activated carbon in O3-BAC pre-treated water on the membrane surface could be the key reason protecting the NF membrane from fouling.

Pilot-scale UV/H2O2-BAC process for drinking water treatment – Analysis and comparison of different activated carbon columns

An UV/H2O2-BAC combination process was developed and the effects of activated carbon columns with carbon of different ages and particle sizes were compared and inspected under long-term operation conditions. In addition, differences in the microbial community structure of the biological membrane on the surface of the activated carbons was explored by scanning electron microscopy (SEM) and high-throughput sequencing. Furthermore, the removal efficiency of organic matter and the microbial community structure were compared between UV/H2O2-BAC and O3-BAC processes under the same treatment conditions. The results showed that younger carbon age and smaller particle size were associated with higher organic matter removal rates. Additionally, Actinobacteria and Legionella were the main microorganisms for BAC to degrade hydrogen peroxide, and the microbial species of the four activated carbons were basically the same, differing only in abundance. When compared with the O3-BAC process, the UV/H2O2-BAC process had higher removal efficiency for organic matter and higher effluent safety. Overall, the results indicate the UV/H2O2-BAC process can be used as an alternative to the O3-BAC process for control of bromate.

Performance of ozonation and biological activated carbon in eliminating sulfonamides and sulfonamide-resistant bacteria: A pilot-scale study

Removal of sulfonamides (SAs) by an integrated ozonation and biological activated carbon filtration (O3-BAC) process, as an advanced drinking water treatment process, was evaluated in a pilot-scale study. Furthermore, the effects of the O3-BAC process on sulfonamide-resistant bacteria (SRB) and on the removal of total organic carbon, UV254, and turbidity were investigated. Results indicate that ozonation could effectively remove SAs from water at an appropriate ozone dose with an improvement of water quality; however, BAC filtration would lead to an increase of SRB. In addition, the performance of the integrated process in eliminating disinfection byproducts formation potential (DBPsFP) in chlorination was evaluated. The results show ozonation would result in an increase of DBPsFP, while subsequent BAC filtration could effectively reduce DBPsFP to the safety-standard level of water quality. Overall, effective removal was achieved by the O3-BAC process in terms of the reduction of SAs but not of SRB. Subsequent disinfection is significant and biological safety should be evaluated further to ensure the effectiveness of the integrated process and the security of water quality.

Evaluating the biosafety of conventional and O3-BAC process and its relationship with NOM characteristics

ABSTRACTIt is the priority to guarantee biosafety for drinking water treatment. The objective of this study was to evaluate the impact of widely applied conventional and ozone-biological activated carbon (O3-BAC) advanced treatment technology on biosafety of drinking water. The items, including assimilable organic carbon (AOC), biodegradable dissolved organic carbon (BDOC), heterotrophic plate counts (HPCs) and the microorganism community structures, were used to evaluate the biosafety. Moreover, their relationships with molecular weights (MWs) and fluorescence intensity of dissolved organic matter were investigated. The results indicated that the technology provided a considerable gain in potable water quality by decreasing dissolved organic carbon (DOC, from 5.05 to 1.71 mg/L), AOC (from 298 to 131 μg/L), BDOC (from 1.39 to 0.24 mg/L) and HPCs (from 275 to 10 CFU/mL). Ozone brought an increase in DOC with low MW <1 kDa, which accompanies with an increase in AOC/BDOC concentration, which could be reduced effectively by subsequent BAC process. The formation of AOC/BDOC was closely related to DOC with low MWs and aromatic protein. Bacteria could be released from BAC filter, resulting in an increase in HPC and the presence of pathogenic bacteria in effluent, while the post sand filter could further guarantee the biosafety of finished water.

Concentration Variation and Removal of Amino Acids in Typical Drinking Sources in the South of China

Amino acids are the main components of nitrogenous organic matter in surface water. In order to reveal the concentration variation and removal of amino acids in reservoirs water, the concentration variation of the twenty common amino acids for three main reservoirs' water in a typical southern city of China was monitored between May and October in the year of 2015 by HPLC, and the space distribution and change trend of the twenty amino acids were analyzed. In addition, the removal of the twenty amino acids was also studied by different water treatment processes. The results showed that the amino acids contents and composition were different among the three reservoirs. Aspartic acid, cysteine and leucine were the main amino acids for the three reservoirs. Besides, there was no obvious seasonal variation of amino acids content for reservoir C. However, the concentration of amino acids in autumn was higher than that in summer. Coagulation and sedimentation were main units for the removal of amino acids in conventional and BAC-UF processes while O3 oxidation was the main unit in O3-BAC process. 94.42%, 66.04% and 49.75% of total amino acids contents were removed by the conventional, BAC-UF and O3-BAC processes, respectively.

Study on the Effect of Different Water Treatment Technology on Removing 2-MIB

To compare the removal efficiency of 2-MIB by traditional water treatment, prechlorination, O3-BAC, MIEX pre adsorption and UV/H2O2 advanced oxidation process, the pilot-test of drinking water odor control technology were studied in this paper. The results showed that the traditional water treatment process had poor effect on removing 2-MIB, with about 10% removal rate, while the O3-BAC process was the best at removing 2-MIB, whose removal rate reached over 90%. And the 2-MIB removal rate of UV/H2O2 process was about 55% and that of prechlorination process was about 20%. However, the MIEX pretreatment process had almost no effect on removing 2-MIB.

Addition of hydrogen peroxide for the simultaneous control of bromate and odor during advanced drinking water treatment using ozone

Complete removal of the characteristic septic/swampy odor from Huangpu River source water could only be achieved under an ozone dose as high as 4.0 mg/L in an ozone-biological activated carbon (O3-BAC) process, which would lead to the production of high concentrations of carcinogenic bromate due to the high bromide content. This study investigated the possibility of simultaneous control of bromate and the septic/swampy odor by adding H2O2 prior to the O3-BAC process for the treatment of Huangpu River water. H2O2 addition could reduce the bromate concentration effectively at an H2O2/O3 (g/g) ratio of 0.5 or higher. At the same time, the septic/swampy odor removal was enhanced by the addition of H2O2, although optimization of the H2O2/O3 ratio was required for each ozone dose. At an ozone dose of 2.0 mg/L, the odor was removed completely at an H2O2/O3 ratio of 0.5. The results indicated that H2O2 application at a suitable dose could enhance the removal of the septic/swampy odor while suppressing the formation of bromate during ozonation of Huangpu River source water.

Advanced oxidation of bromide-containing drinking water: A balance between bromate and trihalomethane formation control

Addition of H2O2 has been employed to repress bromate formation during ozonation of bromide-containing source water. However, the addition of H2O2 will change the oxidation pathways of organic compounds due to the generation of abundant hydroxyl radicals, which could affect the removal efficacy of trihalomethane precursors via the combination of ozone and biological activated carbon (O3-BAC). In this study, we evaluated the effects of H2O2 addition on bromate formation and trihalomethane formation potential (THMFP) reduction during treatment of bromide-containing (97.6–129.1 μg/L) source water by the O3-BAC process. At an ozone dose of 4.2 mg/L, an H2O2/O3 (g/g) ratio of over 1.0 was required to maintain the bromate concentration below 10.0 μg/L, while a much lower H2O2/O3 ratio was sufficient for a lower ozone dose. An H2O2/O3 (g/g) ratio below 0.3 should be avoided since the bromate concentration will increase with increasing H2O2 dose below this ratio. However, the addition of H2O2 at an ozone dose of 3.2 mg/L and an H2O2/O3 ratio of 1.0 resulted in a 43% decrease in THMFP removal when compared with the O3-BAC process. The optimum H2O2/O3 (g/g) ratio for balancing bromate and trihalomethane control was about 0.7–1.0. Fractionation of organic materials showed that the addition of H2O2 decreased the removal efficacy of the hydrophilic matter fraction of DOC by ozonation and increased the reactivity of the hydrophobic fractions during formation of trihalomethane, which may be the two main reasons responsible for the decrease in THMFP reduction efficacy. Overall, this study clearly demonstrated that it is necessary to balance bromate reduction and THMFP control when adopting an H2O2 addition strategy.

Characteristics of DOM and Removal of DBPs Precursors across O3-BAC Integrated Treatment for the Micro-Polluted Raw Water of the Huangpu River

The aim of this study is to determine the impact upon dissolved organic matter (DOM) and removal of disinfection by-product (DBP) precursors of adding an ozone-biological activated carbon (O3-BAC) process after the conventional treatment process (CTP) using water from the Huangpu River in Shanghai, east China. Several metrics, including size fractionation, dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP), were employed to accomplish this goal. In the raw water collected from the Huangpu River, the low molecular weight (MW) molecules (MW &lt;3 kDa) were absolutely dominant in DOM, accounting for more than 55% of total DOC, and the DOM resulted in a high THMFP level of 472.91 ± 4.63 µg/L after an excessive chlorination. The CTP reduced high MW molecules (MW &gt;10 kDa) by 61% and the low MW molecules (MW &lt;3 kDa) by only 8%. The O3-BAC presented an accumulated DOC removal efficiency of approximately 50%, in particular, showing a high degree of the removal effectiveness of low MW molecules. Samplings from the CTP, ozone and BAC were subjected to excessive chlorination to determine the THMFP, and the measured concentrations were 211.89 ± 4.58 µg/L, 169.52 ± 4.55 µg/L, and 124.42 ± 4.27 µg/L, respectively. Therefore, coupled with the THMFP removal rate of 74%, the addition of the O3-BAC process after an existing CTP improved the water quality of the effluent, particularly, in terms of the improved reduction in the precursors of DBPs.

Application of conventional and O3-BAC processes to treat organic matter and antibiotic pollutants in a lake in East China

The occurrence and treatment of antibiotics in a micro-polluted lake which serves as a drinking water source in East China was surveyed. A pilot plant with conventional and O3-BAC (biological activated carbon) processes was set up to investigate its effectiveness in dealing with the contaminants. Solid phase extraction (SPE) coupled with electro-spray ionization-tandem mass spectrometry (LC-ESI-MS-MS) was applied to detect various antibiotics simultaneously. Three groups of antibiotics, i.e. sulfonamides, fluoroquinolones and tetracyclines, were detected in the source water. The gross concentrations of them in the lake are up to 471, 23.4 and 1,039 ng/L, respectively. The conventional and O3-BAC processes could remove 78.9, 62.4 and 70.2% of them, respectively. Among the antibiotics, tetracyclines could be effectively removed by ozonation, while fluoroquinolones could be removed by the coagulation–sedimentation process. BAC could not degrade fluoroquinolones but enabled the reduction of the other two antibiotics. In addition, O3-BAC was an effective technology for the removal of bulk organic matter. The concentrations of chemical oxygen demand (CODMn), UV254 and dissolved organic carbon (DOC) in the effluent of the up-flow BAC process were 2.31 mg/L, 0.034 cm−1 and 1.76 mg/L, respectively, with the corresponding removal rates of 45.1, 67.3 and 65.1%, respectively. In all, the combined conventional and O3-BAC process was the best available technology to remove organic matter as well as antibiotics.

Investigation on the Key Factors and the Solution for pH Value Decrease in Carbon Filter in O3-BAC Process

An investigation was carried out to eliminate the decrease of effluent pH value in carbon filter in O3-biological activated carbon process. The influence factors were examined in a pilot test, and pH was adjusted in the pilot and waterworks. Results show that the carbon filter is an acid-base buffer system and the activated carbon is the key factor. Chemical functional groups on activated carbon surface present acid-base properties to buffer the water but decrease with time, so that effluent pH value decreases. The effects of ozone dosage, CO2 in the carbon filter, and the filter influent quality are negligible. A new method to adjust pH is developed: the activated carbon is first modified by soaking in sodium hydroxide solution to make its pH reach the desired value, and then the pH value of inflow is controlled to certain value by dosing lime in sand filter influent. The method is economical and effective.

浄水処理におけるオゾン‐生物活性炭プロセスの評価

Parallel studies using Ozonation-Biological Activated Carbon (O3-BAC) process and a simple Biological Activated Carbon (BAC) process were conducted to evaluate the effect of ozonation on a BAC process. The raw water used was pre-treated by microfiltration to remove suspended solids. Contact time for ozonation was 24 minutes while empty bed contact time (EBCT) of the activated carbon column was 15 minutes. An ozone dosage of 7 mg·l-1 was used.Effluent DOC and THMFP of O3-BAC process were lower than those of BAC process after 80 days. Lifetime of activated carbon adsorption was extended in the O3-BAC process compared with the BAC process until breakthrough, because ozonation decreased DOC in the activated carbon influent in the O3-BAC process. DOC was partitioned into four fractions and analyzed based on its biodegradability and activated carbon adsorbability. It is proposed that O3-BAC process can be used for a long time without activated carbon replacement because biodegradable DOC was removed even after activated carbon adsorption capacity was exhausted. Adsorbed DOC in the O3-BAC process also decreased until breakthrough, probably because ozonation increased hydrophilicity of DOC resulting in its decreasing adsorbability. In this study, ozone dosage of 2 mg O3·mg DOC-1 and EBCT of 15 minutes was determined to be satisfactory for an increase in biodegradability and removal of DOC.

Ammonia, Nitrite and Nitrate Nitrogen Removal from Polluted Source Water with Ozonation and BAC Processes

Abstract Studies on the removal of ammonia-, nitrite-, and nitrate nitrogen with ozonation (O3), sand filtration (SF), biological activated carbon (BAC), SF-BAC, and/or O3-BAC processes were carried out in two pilot plants and a full scale plant, respectively. The results showed that all of the tested processes exhibited certain nitrogen removal efficiencies, of which both the O3-SF-BAC and O3-BAC processes were most effective and efficient in removing ammonia nitrogen, with mean removal efficiencies of some 90 and 80 percent, respectively. Ozonation was found able to oxidize some organic nitrogen into ammonia, and nitrite ion into nitrate ion. It was also found out, with interest, that the O3-BAC process can carry the nitrification process to the end under sufficient DO content, as well as more hydrocarbon substrates through ozonation that are more easily assimilated by some strains of nitrobacter that can multiply heterotrophically in its carbon beds. In the BAC process, both the DO and easily assimilated substrate contents were too low in its carbon beds due to no ozonation to sustain nitrobacter growth; but the nitrite conversion bacteria, like nitrosornas, can survive under such conditions. As a result, nitrite or nitrate ion content increased multiply in the effluents from BAC or O3-BAC processes over their influents. respectively. The removal mechanisms of various processes for the three forms of nitrogen were studied and discussed, and the optimum design parameters were determined as well.