Urban Wastewater Treatment by Catalytic Ozonation

This study focuses on the catalytic ozonation of organic matter recalcitrant to usual water treatment technologies. Experiments aimed to investigate the efficiency of the process TOCCATA®, which uses a granular catalyst coupled with ozonation. Comparison was made between single ozonation, single adsorption onto the catalyst and catalytic ozonation. Adsorption was proven to contribute to decreased dissolved organic carbon. Catalytic ozonation enhanced organic matter removal and ozone transfer compared to single ozonation. Catalytic ozonation was modeled with global apparent first-order kinetics and single adsorption with pseudo–second-order sorption kinetics.     

Extraction and Destruction of Organics in Wastewater Using Ozone-Loaded Solvent

Originally developed as a heat exchange fluid, Volasil 245 (decamethylcyclopentasiloxane) has been found to dissolve 10 times more ozone than water does. This article proposes and investigates the extraction of wastewater contaminants to ozone-loaded Volasil 245 as a means of providing rapid treatment. In a series of bench-scale tests, the effectiveness of ozone-loaded Volasil 245 contact was compared with that of conventional gas contact. Tests were conducted with respect to a range of organic compounds: namely, phenol, 2-chlorophenol, 2,3-dichlorophenol, 1,3-dichlorobenzene, o-nitrotoluene, and nitrobenzene. Contact with the ozone-loaded solvent was suggested to be the more rapid technique, reducing aqueous concentrations by at least 85% within 30 s. In the case of 2-chlorophenol, Volasil 245 contact was shown to require just ~0.5 min to achieve a residual aqueous fraction of 5%, as opposed to ~4.5 min of gas contact. However, water/solvent interfacial mass transfer resistance was suggested to limit the degree of aqueous decontamination ultimately achieved.     

Examining the Role of Effluent Organic Matter Components on the Decomposition of Ozone and Formation of Hydroxyl Radicals in Wastewater

The impact of wastewater derived effluent organic matter (EfOM) on the decomposition of ozone and formation of hydroxyl radicals (HO^●) was evaluated for four wastewaters (sites A, B, C1 and C2). The reactivity of EfOM was assessed by fractionation into four apparent molecular weight (AMW) fractions (<10 kDa, <5 kDa, <3 kDa, and <1 kDa). The R_CT, defined as the ratio of HO^● exposure to ozone exposure (∫HO^●dt?/?∫O₃dt), was measured for all fractions and bulk waters (at times greater than 5 seconds), with an initial ozone dose equal to the total carbon concentration of EfOM (ozone:DOC ratio of 1). The R_CT of all the samples and ozone first-order decay rates of two of the waters increased significantly (95% confidence) from the bulk sample to the <10 kDa fraction, and decreased with AMW. This indicates that the intrinsic capacity of different molecular weight fractions of the EfOM have different reactivity with ozone.     

Reaction Mechanisms for DBPS Reduction in Humic Acid Ozonation

In this study, XAD-8 resins were used to extract the natural organic matter (NOM) from samples collected at the intake of Feng Yuan Water Treatment Plant (in central Taiwan) into five groups: humic acids, fulvic acids, hydrophobic neutrals, hydrophobic bases, and hydrophilic fractions. Quantitative results show that hydrophobic and hydrophilic fractions contribute 44.2% and 55.5% of NOM, individually. Ozonation processes will significantly reduce both disinfection by-products formation potential (DBPFP) and average molecular weight of the humic acid sample. Additionally, double carbon bonds are broken up so that hydrophobic fractions were converted to hydrophilic fractions by ozonation leading to the reduction of DBPFP.     

Parameters Affecting the Formation of Bromate Ion During Ozonation

Batch type ozone experiments conducted on aquatic humic substances solutions spiked with bromide ion were developed to evaluate the importance of various parameters that may affect the formation of bromate ion during ozonation. The nature of the NOM, the alkalinity, the bromide ion content and the presence of ammonia were found to significantly affect the bromate ion production. Temperature and pH can be considered as minor factors. The ozonation of a clarified surface water using a continuous flow ozone contactor have shown that the addition of a low quantity of ammonia (0.05 to 0.1 mg/L NNH₄ ⁺) appeared to be an interesting option for controlling the bromate formation. On the contrary, the addition of hydrogen peroxide may enhance or reduce the bromate ion production, depending on the applied hydrogen peroxide/ozone ratio.     

Influence of Ozonation Conditions on Aldehyde and Carboxylic Acid Formation.

The influence of ozonation conditions (i.e. ozone dose and contact time) on the aldehyde and carboxylic acids formation was studied on a pilot scale. The data derived from changes in the molecular weight distribution of natural organic matter (NOM) and the concentration of residual ozone can be applied to a selection of the optimum ozonation conditions. The results confirm the relative ease with which ozone reacts with the organic matter. The short contact time (4–6?min) appeared to be sufficient for the reaction. The higher molecular weight (1600?D) fraction of NOM seems to be slightly more reactive to ozone than the lower molecular weight fraction (500?D). It was also observed that carboxylic acids had been formed at much higher quantities than aldehydes. Two differently acting groups of aldehydes were identified. The concentration of the first one (i.e. formaldehyde, acetaldehyde) strongly depends on ozone dose, while the concentration of the second group of aldehydes (i.e. glyoxal, methylglyoxal) seems to be relatively independent of the ozone dose.     

Treatment Efficiency of an Improved Ozonation Unit Applied to Fish Culture Situations

Ozonation has been successfully applied in experimental fish culture recirculation systems, especially to oxidize some of the most important metabolites (such as nitrite, ammonium, BOD) at times when these concentrations reach a daily peak level. In this study the oxidation rates for ammonium, nitrite, and BOD have been determined for each of these components separately or in combination, using an improved design of the contacting chamber. Two flow rates and three ozone concentrations were employed. Ammonia oxidation rates were slowest while nitrite and BOD removal was rapid. Ozone concentrations substantially influenced the oxidation rates for ammonium ion. Nitrate was oxidized equally rapidly under almost all operational conditions. Slight differences in oxidation rates were noted for both ammonia and nitrite as long as the BOD was high.     

Changes in the Chemical Nature of a Biologically Treated Wastewater During Disinfection by Ozone

Pilot plant studies were carried out on the effect of ozone on the chemical content of a secondary domestic and industrial sewage. Results are expressed in terms of COD, BOD₅, nitrite ion concentrations, bacterial counts, XAD-4-extraetable compounds, and free amino acid concentrations. Ozone dosages of 6 to 12 mg/L were found to reduce levels of fecal bacteria, COD and nitrite ion concentrations significantly, to modify the nature and the concentration of XAD-4-extraetable compounds, and to increase the concentration of free amino acids.     

Kinetic Description of Industrial Wastewater Ozonation Processes

Literary and experimental data on the ozonation kinetics of aqueous solutions and wastewater were analyzed. COD was suggested to be used as a kinetic parameter from the solution side. On the basis of the results obtained from the ozonation of model solutions and wastewater, the rate coefficient by COD of the reaction was shown to be constant during separate stages of the process. Due to the consumption of fast-reacting components and entering into the reaction of more slowly reacting intermediate products, the rate coefficient changed spasmodically with transition from one stage to another. The reaction order with respect to the COD of the solution was shown to be equal to the reaction order with respect to the pure component.     

Effect of Ammonia and Chloramine Pretreatment during the Ozonation of a Colored Groundwater with Elevated Bromide

Ozone coupled with pre-chloramination was evaluated as an effective color removal and bromate control method for groundwater at Mesa Water's Well #8. A modified solution ozone test procedure was employed to simulate the sidestream ozone injection. Satisfactory color removal (<10 PtCo CU) was achieved with 2 mg/L of ozone in the presence or absence of preformed monochloramine or ammonia. While bromate formation was reduced by 67% and 83% with 0.3 and 0.6 mg/L of ammonia-N alone, respectively, 68% and 92% of bromate formation was suppressed with 1.0 and 2.0 mg/L of monochloramine as Cl₂, respectively. Only the pre-treatment with 2.0 mg/L of monochloramine provided sufficient bromate control to meet its maximum contaminant level of 10 μg/L. UV and fluorescence analyses showed effective destruction of color-causing organics by ozone in the presence of preformed monochloramine.     

Promoting Hydroxyl Radical Production during Ozonation of Municipal Wastewater

Hydroxyl radical (HO^?) production during ozonation of municipal wastewater was investigated with and without liquid or solid-phase promoters. For liquid-phase promoters, an “ozone dose threshold” was observed, below which addition of H₂O₂ yielded no discernible increase in the rate of HO^? production. This threshold occurs because ozonation of bulk organics in wastewater promotes HO^? due to the presence of ambient promoters. Although solid-phase catalysts are reported to promote oxidation of contaminants, ozonation of effluent over TiO₂ or GAC was no more effective on trace organic removal than over inert surfaces.     

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.     

Two-Stage Optimization of Coliforms,Helminth Eggs,and Organic Matter Removals from Municipal Wastewater by Ozonation Based on the Response Surface Method

In this study, a set of municipal wastewater (MWW) samples from an actual residual water treatment plant was treated by ozone. The residual water was characterized in terms of organic load and biological contaminants: total coliforms (TC), fecal coliforms (FC) and helminth eggs (HE). Initial values of these parameters were 2.8 × 10⁷ MPN/100 mL, 8.48 × 10⁶ MPN/100 mL, and 470 L^?1, respectively. The experimental setup considered the modification of pH and ozone dose as independent variables. Three different initial pH values (4.0, 7.0, and 11.0) and three different ozone concentrations (6, 15, and 30 mg/L) were used to investigate the pH ozone dose effect. The efficiency of ozone-based treatment was determined by the reduction of the microbiological indicators (TC, FC, and HE) and physicochemical parameters (COD and turbidity). The response surface method was used to determine suboptimal reaction conditions. These conditions were obtained using a two-stage procedure. The conditions under which both microbiological and organics were better removed corresponded to pH 7.8 and ozone concentration of 15.5 mg/L. A decline of biological indicators of 99% for TC, 99% for FC, and 99% for HE was obtained under the same reaction conditions. The reduction of chemical oxygen demand (COD) and turbidity was 75% and 85% under the same operation conditions, respectively.     

Investigation into Ozonation of Coal Coking Processing Wastewater for Cyanide,Thiocyanate and Organic Removal

A laboratory investigation was carried out to establish whether ozonation could be used to oxidize cyanides, thiocyanates and color in wastewater from a coal coking plant to supplement biological and activated carbon treatment (GAC). Ozonation was found to be capable of oxidizing cyanide and cyanate to sufficiently low levels at relatively high stoichiometric ratios as a result of competitive ozone consumption by organic substances in the wastewater. While good color removal was also achieved with ozonation, organic removal could not match GAC in overall organic removal. Ozonation was not found to be economical for the remaining nine years of a build, own, operate and transfer (BOOT) contract period. Ozonation would be competitive over longer operational periods and more environmentally friendly than presently used technology.     

The Formation of Filter-Removable Biodegradable Organic Matter During Ozonation

Biodegradable organic matter formed during the ozonation of natural waters was fractionated into rapidly and slowly degradable components based on measurements of biodegradable organic carbon (BDOC). The rapidly degradable fraction (BDOC_rapid) was defined using the specific BDOC reactor incubation time that resulted in biodegradation similar to that in a pilot scale biofilter. Ozone dose was found to increase the formation of BDOC_rapid up to a transferred dose of 1.0 to 1.5 mg O₃/mg DOC. This fraction was insensitive to DOC quantity or character. The formation of BDOC_slow was not sensitive to ozone dose but was sensitive to DOC quantity.     

Microbial Counts and Antibiotic Resistances during Conventional Wastewater Treatment and Wastewater Ozonation

ABSTRACT

In view of the increasing interest in the occurrence and spread of antibiotic-resistant bacteria due to wastewater treatment systems into the environment, total colony counts and antibiotic-resistant bacteria were determined in regard to a conventional wastewater treatment plant and its upgrade with a wastewater ozonation. To cope with the elimination of conventionally not sufficiently decimated micropollutants, the Eifel-Rur Waterboard built a full-scale ozonation plant at the stream Wurm, which is strongly influenced by WWTP discharge. To evaluate the effect of wastewater ozonation on the receiving water’s biocenosis, extensive monitoring of the WWTP and its receiving water is performed before and after implementation of ozonation treatment and in preliminary pilot-scale ozonation experiments. Total colony counts showed no significant difference between the stream Wurm upstream and downstream of the WWTP and were slightly below the average of comparable investigations. Antibiotic resistances showed only a little differences between WWTP and the stream samples. Furthermore, no accumulation of antibiotic resistances was found at the conventional WWTP. Pilot-scale ozonation yielded a reduction of total colony counts of fecal indicator bacteria Escherichia coli and Enterococci after ozone treatment. The pilot-scale experiments gave no indication that ozone treatment leads to a rise in antibiotic resistances against selected antibiotics of different antibiotic classes.     

Improvement in the Effectiveness of Ozonation of Drinking Water Through the Use of Hydrogen Peroxide

Addition of hydrogen peroxide to water during ozonation increases the rate of oxidation of organic compounds and ozone transfer. Coupling ozone with hydrogen peroxide can increase the efficiency of a drinking water treatment line, for example in removing THM precursors. To optimize this oxidation process, the quantity of hydrogen peroxide added and the point of injection must be carefully selected.     

Kinetics of Natural Organic Matter as the Initiator,Promoter, and Inhibitor,and Their Influences on the Removal of Ibuprofen in Ozonation

Natural organic matter (NOM) can simultaneously act as the initiator, promoter and inhibitor in water ozonation. This study presents an explicit method that can be used to determine these rate constants via the integration of the transient steady-state hydroxyl radical (?OH) model, the R_ct concept and the pseudo first-order ozone decomposition model. The theoretical background of this method was provided, and the method was validated with model compounds. The rate constants of three NOM isolates were determined using the developed method. With these rate constants, the influences of NOM on the degradation of ibuprofen, an ?OH-reactive pharmaceutical compound, can be quantitatively described. [Supplementary materials are available for this article. Go to the publisher's online edition of Ozone Science &; Engineering for the following free supplemental resources: tables, figures, and equations.]     

Using Fractionated Natural Organic Matter to Quantitate Organic Byproducts of Ozonation

An improved procedure was used to isolate and fractionate natural organic matter (NOM) in water for subsequent ozonation and disinfection by-product (DBP) and color removal quantisation. Isolated NOM fractions from two different sources, accounting for approximately 50 to 60% of the dissolved organic material and 60 to 75% of the color, were characterized and then ozonated under conditions approximating those encontered during drinking water treatment. The natural waters also were ozonated. Organic DBPs of either health concern or which may contribute to biological instability of finished water were investigated, including aldehydes, oxoacids and low molecular weight carboxylic acids. pH and ozone dosage were the parameters having the greatest effect on DBP formation. On the basis of UV absorbance measurements, the fulvic acid fractions studied taken together accurately represented the natural water and may be the primary sources of precursor material for aldehydes and oxoacid DBPs. However, as yet unidentified NOM fractions contribute significantly to carboxylic acid formation upon ozonation.