Pilot-Scale Evaluation of Ozone vs. Peroxone for Trihalomethane Formation

Both the direct ozone reaction and the indirect hydroxyl radical reaction are important in the ozonation of drinking water. This paper investigates the effectiveness of ozone versus ozone coupled with hydrogen peroxide (peroxone) with respect to trihalomethanes formation. The investigation was conducted on a pilot-scale at various H₂O₂:O₃ dose ratios of 0.1, 0.2, and 0.35 and change in peroxide addition point (pre- and post-ozonation). It was observed that the addition of peroxide, either before or after ozonation, increased trihalomethane concentrations and that increasing H₂O₂:O₃ increased trihalomethane concentrations. In comparing the addition point of peroxide, addition prior to ozonation better controlled trihalomethane formation than after ozonation.     

The Influence of Ozone,Oxygen and Chlorine on Biolocical Activity on Biological Activated Carbon

A laboratory study was conducted into the effects of the treatment of activated sludge effluent with different oxidants on the biodegradability of the organic substances. It was found that, under the experimental conditions described, ozone increased the biodegradability, whereas chlorine had no apparent significant effect. The effect of continuous oxidative pretreataent of activated sludge effluent on microbial populations and the biological activated carbon used subsequently in the process also was studied. It was found that ozone, particularly at a dosage of about 5 mg/L promoted biological activity, while chlorine and oxygen (in addition to the dissolved oxygen already in the effluent) had no significant effect on the biological population size.     

Effect of Ozone Dosage for Removal of Model Compounds by Ozone/GAC Treatment

This research employed batch ozonation and GAC (granular activated carbon) column to investigate the effect of preozonation dosage on the subsequent GAC adsorption, in terms of the adsorption capabilities for small and large molecules.

For large target compounds like humic acid, the adsorption efficiency was improved with higher ozone dosages, whereas the combined effect of ozonation coupling with GAC for small model compounds seems to be negative. In addition, there is a selective adsorption between the chlorinated disinfection by-product (DBP) precursors and other non-precursors, and most of the non-precursors are less adsorbable than the precursors.     

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.     

Removal Of Residual Organics From Drinking Water By Ozonation And Activated Carbon Filtration: A Pilot Plant Study

The effects of ozonation, granular (GAC) and biological activated carbon (BAC) in the removal of natural organic matter and precursors of disinfection byproducts from drinking water were studied on pilot scale. Ozonation was determined to be the best method to reduce concentrations of the precursors of AOX, chloroform and mutagenicity, whereas BAC removed organic matter the most effectively. Reductions in TA100 mutagenicity were an average 40%, 4%, 26% in ozonated, GAC and BAC filtered water, respectively. Average reductions of AOX levels were similar at 48%, 7% and 35%, respectively. The chloroform formation potential always increased after GAC filtration.     

Synergistic Evaluation of Ozone and UV at the Coquitlam Source for Enhanced DBP Control and Cryptosporidium Inactivation

A study was performed for the GVRD to select the ozone dose that results in a higher UVT (UV Transmittance) and reduced DBP formation potential, at the most economical life cycle costs of ozone and UV treatment. The GVRD treats its Coquitlam source with ozone, to meet Giardia and virus inactivation requirements. Currently, the Coquitlam Facility does not meet Cryptosporidium inactivation requirements (3-log). Because the ozone dosage required for Cryptosporidium inactivation is cost prohibitive, UV treatment was selected to provide for adequate log inactivation. Based on pilot and full-scale test results, a model was developed to predict the ozone treated water UVT, which was applied to historical water quality data to evaluate life cycle costs of ozone and UV treatment. In addition, the dosage necessary for control of DBPs, the change in ozone decay rate with increases in pH, and the impact of three quenching chemicals on treated water UVT were evaluated.     

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.     

Ozone and Activated Carbon for Tertiary Wastewater Treatment

Preozonation of biologically or physically–chemically treated wastewater effluents, followed by passage through granular activated carbon (GAC) for tertiary wastewater treatment was studied at the Duck Creek Wastewater Treatment in Garland, Texas. Whereas the average period of operation for the GAC before exhaustion without ozone pretreatment was 70 days, pretreatment with ozone or with oxygen alone extended GAC operation to at least 480 days, withoutexhaus–tion. Effluent streams consistently metapplicable discharge standards during this period of time, without the necessity of regenerating the GAC.     

Fluidized Bed GAC Filtration for the Control of Ozone Residuals

A laboratory scale study was conducted in order to investigate upflow granular activated carbon (GAC) filtration for the removal of aqueous ozone. The experimental results showed that fluidized bed GAC filtration operated at hydraulic loadings of 60 — 100 m/h is a promising process for the safe destruction of ozone residuals at the end of ozone contactors. The key parameters in terms of ozone destruction are empty bed contact time, the specific ozone destruction capability of the different GACs and the specific surface of the carbon. Ozone removal in such filters was well described with first order kinetics and external mass transfer was not limiting. Under given conditions in terms of ozone influent concentration, GAC granulometry, GAC density and bed depth, hydraulic loading and available headloss have to be traded off in order to design a well adapted and robust system.     

Pilot-Scale Ozone Inactivation of Cryptosporidium and Other Microorganisms in Natural Water

A pilot-scale study was conducted to evaluate the inactivation by ozone against Cryptosporidium oocysts, Giardia cysts, poliovirus, and B. subtilis endospores spiked into Ohio River water. The indigenous Ohio River populations of total coliform bacteria, heterotrophic plate count bacteria and endospores of aerobic spore forming bacteria were also evaluated. Endospores were the only organisms found to be more resistant to ozone than Cryptosporidium oocysts. Endospores may serve as an indicator of microbial treatment efficiency. Cryptosporidium oocysts were more resistant than Giardia cysts or poliovirus. Although HPC bacteria were less resistant than Cryptosporidium oocysts, variability limits their usefulness as an indicator of treatment efficiency. Ozone inactivation data generated in a pilot-scale study employing natural surface waters were comparable to inactivation data derived from previously published bench-scale studies using laboratory waters. The ozone requirements for inactivation of Cryptosporidium oocysts may produce elevated levels of bromate and ozone byproducts.     

Formation and Removal of Biodegradable Ozonation By-Products during Ozonation-Biofiltration Treatment: Pilot-Scale Evaluation

An ozonation-biological filtration pilot-scale study was performed to evaluate the formation and removal of biodegradable ozonation by-products. The formation of aldehydes and ketoacids was found to be proportional to the DOC concentration and ozone dosage, and a strong relationship between the formation of aldehydes, ketoacids, and biodegradable dissolved organic carbon (BDOC) was observed. Four types of granular activated carbon (GAC) and one nonadsorbing medium, biolite, were employed to evaluate the performance of biofiltration for removing ozonation by-products. It was observed that GAC filters developed biological activity sooner than the biolite filter. Once developed, biofilters, either GACs or biolite, were particularly effective in the removal of aldehydes, ketoacids and BDOC.     

Effectiveness of Pre- and Intermediate Ozonation on the Enhanced Coagulation of Disinfection By-product Precursors in Drinking Water

This study evaluated the impact of pre- and intermediate ozonation coupled with enhanced coagulation in controlling halogenated disinfection by-product formation in drinking water. Raw waters from utilities representing each of the nine elements of the enhanced coagulation matrix presented in Table I were examined. All testing was completed using bench-scale, batch experimental procedures. The various waters were analyzed for turbidity, total organic carbon, dissolved organic carbon, ultraviolet absorbance, trihalomethane formation potential, and haloacetic acid formation potential before and after ozonation. The results indicated that formation of trihalomethanes and haloacetic acids following enhanced coagulation decreased with both pre- and intermediate ozonation applications relative to the decreases observed by enhanced coagulation alone. The amount of trihalomethanes and haloacetic acids formed were lower for the waters that were pre-ozonated and then coagulated compared to those that were coagulated first and then ozonated. This comparison must be tempered by the fact that the settled waters treated by intermediate ozonation were not subjected to subsequent biofiltration which is commonly used in water treatment practice to remove additional DBP precursors. Strong correlations between disinfection by-product formation potentials and ultraviolet absorbance at 254?nm were observed for enhanced coagulation with and without pre- and intermediate ozonation.     

Effect of Ozone and GAC Process for the Treatment of Micropollutants and DBPs Control in Drinking Water: Pilot Scale Evaluation

To improve the quality of water supplied to the City of Seoul in Korea, a pilot-scale evaluation of how the conventional treatment process could be upgraded was conducted. Three candidate processes were evaluated and compared: a conventional process (consisting of coagulation, sedimentation, and rapid sand filtration) plus GAC (Train A); a conventional process plus ozone and GAC (Train B); and a process consisting of coagulation, sedimentation, intermediate ozone, sand filtration, and GAC (Train C). Treatment efficiency of the unit process and overall treatment trains were evaluated using several parameters such as turbidity, dissolved organic carbon (DOC), UV absorbance at 254 nm (UV₂₅₄), specific ultraviolet absorbance (SUVA), micropollutants (pesticides, benzenes, and phenols), disinfection by-products (trihalomethanes (THMs), haloacetic acids (HAAs) and aldehydes), and total organic halogen (TOX). Results showed that ozone and/or GAC was effective for removing micropollutants and controlling chlorinated by-products such as THMs and HAAs. However, any synergistic effect of ozonation (adsorption and biodegradation) on GAC was observed due to the low concentration of aldehydes in raw and process water.     

The Application of Ozone for Water Treatment In The United Kingdom — Current Practive and Recent Research

Only two water works in the UK apply ozone at present as part of their treatment, onefor taste and odor control and theother forcolor removal. Forthetwo applicationus ozone was the most economical option at thetime theplants were installed andozone has been successful for the purpose for which it was designed.     

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.     

Effects of Ozone and Ozone/Hydrogen Peroxide on the Degradation of Model and Real Oil-Sands-Process-Affected-Water Naphthenic Acids

Naphthenic acids (NAs) are persistent compounds that contribute to the toxicity of oil sands process-affected water (OSPW). In this study, the effects of ozone and ozone/hydrogen peroxide on the NAs degradation in buffered water and OSPW were examined. Cyclohexanoic acid (CHA) was used as a model NAs compound in buffered water experiments at two different pHs, using radical scavengers. At pH 9, the addition of carbonate did not have any effect on CHA degradation. Additions of tert-butyl alcohol and tetranitromethane decreased the CHA degradation levels. For the OSPW experiments, degradation of acid-extractable fraction (AEF) and NAs was examined. Approximately 90% of AEF was oxidized in a semi-batch system. In a batch system, 99% of OSPW NAs were degraded. This study demonstrated that ozone and ozone/hydrogen peroxide could be suitable treatment processes for OSPW remediation.     

Efficacy of Ozone to Reduce Chlorinated Disinfection By-Products in Quebec (Canada) Drinking Water Facilities

The impact of ozonation on the reduction of chlorinated disinfection by-products formation was investigated in 15 full-scale and lab-scale drinking water facilities of Québec (Canada). Total trihalomethanes (TTHM) and the sum of six haloacetic acids (HAA6) were measured after chlorination under uniform formation conditions (UFC). Results showed that before ozonation TTHM and HAA6 average concentrations were 89.4 and 45.3 μg/L, respectively. In full-scale ozonation conditions TTHM-UFC and HAA6-UFC reductions averaged respectively 27 and 32%. After lab-scale ozonation at a O₃/C of 1:1, a decrease of only 9% of TTHM was calculated, while for HAA6, reduction was not significantly impacted (30%). For BDOC, average concentrations of 0.13, 0.46, and 0.69 mg C/L were measured before and after and lab-scale ozonation, respectively. Chlorine demand (Cl₂D) and immediate ozone demand (IOD) were found to be the most appropriate indicators to evaluate NOM reactivity after ozonation.     

Applicability of Ozone and Biological Activated Carbon for Potable Reuse

The Upper San Gabriel Valley Municipal Water District in California is considering groundwater replenishment as a potential strategy to augment its potable water supply. This case study demonstrates the broad applicability of ozone and biological activated carbon (BAC) for such potable reuse systems based on recently developed criteria and models for bulk organics, trace organic contaminants, disinfection byproducts, and cost. Using an advanced treatment train composed of ozone (ozone to total organic carbon ratio of 1.0) and BAC (empty bed contact time of 20 min), a 10 million gallon per day potable reuse facility can achieve savings of $25–$51 million in capital costs, $2–$4 million per year in operations and maintenance costs, and 4–8 GWh per year in energy consumption in comparison to alternative treatment trains with reverse osmosis. This ozone-based treatment train is also capable of achieving public health criteria recently developed by the California Department of Public Health and the National Water Research Institute for potable reuse applications.     

Oxone Enhanced Biological Activated Carbon in Denver,Colorado: A Pilot Plant Study

Five parallel ozone and activated carbon systems were compared for their effectiveness in treating unchlorinated effluent from the Denver Metropolitan Sewage Disposal District No. 1 wastewater facility. Data were gathered over four months of continuous operation. The objective of the study was to assess the potential for enhanced carbon column performance through the use of ozone.     

The Efficacy of Ozone/BAC Treatment on Non-Steroidal Anti-Inflammatory Drug Removal from Drinking Water and Surface Water

Three non-steroidal anti-inflammatory drugs (NSAIDs)—ketoprofen, naproxen and piroxicam—in both deionized (DI) water and surface lake water (SW) (Tallahassee, FL), were exposed to varying ozone treatment regimes or H₂O₂/O₃ advanced oxidation on the laboratory bench. Recently used biofilm-supporting granular activated carbon (BAC) was sampled from a municipal drinking water treatment facility (Tampa, FL, USA), and employed to determine the bio-availability of chemical intermediates formed in ozonated water. Advanced chemical analysis was used to identify oxidation by-products formed and combined with a bioanalytical tool to assess non-specific toxicity (Microtox assay). All 3 target pharmaceuticals were efficiently removed by different processes, with a lower NSAIDs removal yield observed in lake water compared to DI water experiments. The removal yields of ketoprofen, naproxen, and piroxicam improved with increasing ozone dose, H₂O₂/O₃ ratio and empty bed contact time (EBCT) with BAC. Ozonation with BAC filtration had a positive impact by reducing the initial ozone dose required to achieve > 90% removal of all 3 pharmaceuticals (when an initial ozone dose < 1 mg L^-1 was combined with EBCT < 15 min). The toxicity evolution of the treated samples was monitored by Microtox bioassay. Ozone doses higher than 2 mg L^-1 for 2 min contact time were optimal to reach the lower water samples toxicity with NSAIDs removal yields ranging from 95.5 to 99.0% in DI water and from 77 to 90% in SW. Also, higher ozone doses were not shown to remove the residual toxicity. In contrast, the BAC filtration hardly decreases the sample toxicity when an EBCT of 15 min was chosen despite a NSAIDs removal yield equal or higher than 90% in SW.