Effect Of Pre-ozonation Research Articles

Effect of pre-ozonation on coagulation with IPF–PACls: Role of coagulant speciation

Inorganic polymer flocculants (IPFs)–polyaluminum chloride (PACl) with various B (OH/Al ratio) values were synthesized and applied to examine the effect of ozone on coagulation. Formation and performance of flocs during coagulation processes were monitored using photometric dispersion analyzer (PDA). And the apparent molecular weight distribution (AMWD) and resin fractionation (RF) method were performed to characterize molecular changes of aquatic organic matter (AOM) resulted from pre-ozonation. The results show that O 3 exhibits complicated effects on organic matter coagulation depending largely on dosage of O 3, characteristics of AOM and coagulant speciation. Interaction of ozone with AOM results in two effects: decomposition–mineralization of small AOM and desorption–decomposition of particle adsorbed AOM. Coagulation aid effect of ozone in the aspects of coagulation kinetic is observed only for PACls with certain OH/Al ratio at moderate ozone doses. When PACl ( B = 2.5) used as coagulant, less effect on floc formation is observed at O 3 dosage less than 0.74 mg O 3/mg total organic carbon (TOC). With increasing O 3 dosage, floc formation is retarded gradually. Removals of turbidity, dissolved organic carbon (DOC) and UV 254 are all decreased. With decreasing coagulant B value, the influence of ozonation on coagulation becomes gradually remarkable. As PACl with B = 1.5 and 2.2 are used, ozone improves turbidity removals at ozone dosage 1.6 mg/L or 0.36 mg O 3/mg TOC. AlCl 3 exhibits worse performance than PACl in all O 3 dosages.

Removal of Dissolved Organic Carbon and Color from Dyeing Wastewater by Pre-ozonation and Subsequent Biological Treatment

The effects of pre-ozonation and subsequent biological treatment on the decrease in dissolved organic carbon (DOC) and color from dyeing wastewater were investigated. Moreover, the compositions of organic compounds in raw wastewater (RW) and the respective treated waters were estimated, and microscopic observations of the mixed liquor were conducted. The amount of ozone required to remove 1 mg of DOC and the DOC removal rate brought about by pre-ozonation ranged from 6.6 to 13.2 mgO3/mgC and 12 to 15%, respectively. The total amount of DOC removed was increased by the combined use of pre-ozonation and subsequent biological treatment, and pre-ozonation did not necessarily lead to an increase in the amount of DOC removed by biological treatment. However, this combined method was effective in decreasing color and adsorbable organic halide formation potential (AOXFP). The rates of the dyestuff in RW and the respective treated waters were less than 10% of total DOC, and those of the other non-biodegradable compounds were much higher than those of the dyestuff. The morphological difference was observed in the predominant bacteria in RW with and without pre-ozonation.

Microfiltration for separation of green algae from water

Cross-flow microfiltration was used for separation of green algae, Chlorella sp., from freshwater. The transmembrane pressure (TMP) was adjusted at 40, 50 and 60 kPa, respectively. The cross-flow velocity was set at 0.43 m/s for laminar flow and 0.84 m/s for turbulent flow, respectively. The results showed that flux increased as TMP increased from 40 to 50 kPa. But drastic flux decline was observed when operating at TMP of 60 kPa. Raising cross-flow velocity increased the initial flux of MF under TMP of 60 kPa. Nevertheless, implementing turbulent cross-flow did not improve the drastic flux decline under the highest TMP. Preozonation increased the dissolved organic carbon, decreased algal viability and made the size of algal cells smaller. It also increased dissolved polysaccharide that derived from extracellular organic matter (EOM). Different effects of preozonation on flux behavior of MF were observed when utilizing hydrophobic and hydrophilic membrane. Generally speaking, preozonation improved performance of microfiltration by reducing cake compressibility and the biomass loading when both membranes were used. However, dissolved polysaccharide released during preozonation was adsorbed onto the hydrophobic membrane. Consequently, fouling resistance of the hydrophobic membrane became higher. These arguments were verified by classification of hydrodynamic resistances.

The Effects of Preozonation on the Biodegradability of Phenolic Solutions Using a New Gas-Inducing Reactor

To achieve effective COD removal, the combination of preozonation with biological treatment is necessary for phenolic wastewater treatments. Preozonation of 4-cresol, 2-chlorophenol and 4-nitrophenol solutions can be carried out with high ozone utilization rate using a new gas-inducing reactor. During the preozonation, the phenolic compounds can be completely decomposed with 100% ozone utilization rate. This new gas-inducing reactor is beneficial for the preozonation of phenolic solutions, comparing with a conventional gas-liquid reactor. The BOD5 of preozonized phenolic solution is strongly related to both the degree of decomposition of phenolic compounds and the accumulation of intermediate products in aqueous solution. Based on the high ozone utilization rate, it is suggested that the optimal utilized ozone dose for 4-cresol, 2-chlorophenol and 4-nitrophenol can be chosen as 360, 350 and 400 mg/L, respectively. At those optimal utilized ozone doses, the ratio of BOD5/COD of preozonized 4-cresol, 2-chlorophenol and 4-nitrophenol solutions increase to 0.33, 0.26 and 0.33, respectively.

The effects of preozonation on the biodegradability of mixed phenolic solution using a new gas-inducing reactor

In this study, the effects of preozonation on the biodegradability of mixed 2-chlorophenol/4-cresol solution were investigated using a new gas-inducing reactor, which can provide high ozone utilization efficiency. The decomposition rate of phenolic mixture, COD removal and TOC removal increases with increasing pH. A half-order overall kinetic model can correctly describe the decomposition of phenolic mixture. The BOD 5/COD ratio of the preozonized solutions increases with increasing preozonation time, indicating that preozonation can enhance the biodegradability. Based on high ozone utilization rate, it is concluded that the best characteristic time can be chosen at the rapid increase of ozone gas outlet concentration. Since the ozone gas outlet concentration can be easily monitored, it is a useful real-time control parameter in preozonation.

The enhancement of the biodegradability of phenolic solution using preozonation based on high ozone utilization

In this research, the effects of preozonation on the biodegradability of 4-cresol, 4-nitrophenol and 2-chlorophenol solutions were investigated using a new gas-inducing reactor with high ozone utilization rate. The extent of preozonation may be monitored by determining the characteristic ozonation behaviors of preozonized phenolic solutions, such as residual phenolic concentration, ADMI value and ozone gas outlet concentration. Experimental results showed that as the initial phenolic compounds decomposed completely, the ozone gas outlet concentration rapidly increases. In addition, at pH 7, a peak ADMI value appears during the preozonation of 4-cresol and 2-chlorophenol, while for 4-nitrophenol the ADMI value decreases monotonically. Based on the characteristic ozonation behaviors and the ozone utilization rate, three characteristic times were chosen in order to have better control on the extent of preozonation. The effect of preozonation on the biodegradability of preozonized phenolic solution was studied based on these characteristic times. The intermediate products during the preozonation were also identified. The variation of BOD 5 is strongly dependent on the accumulation of intermediate products. It is suggested that the best characteristic time is as the rapid increase of ozone gas outlet concentration in this study. The biodegradability (BOD 5/COD) of preozonized 4-cresol, 2-chlorophenol and 4-nitrophenol solutions increase to 0.18, 0.26 and 0.33, respectively, for the best characteristic time.

The effect of pre-ozonation on the biocompatibility of reactive dye hydrolysates

Pre-ozonation of 14 different reactive dyestuff hydrolysates at alkaline pH was investigated to assess possible relationships between ozone transfer efficiency, first order decolourization kinetics, release of initially complexed heavy metals and relative changes in the biodegradability of the partially oxidized dye waste samples. Biocompatibility of the raw (untreated) and ozonated dye hydrolysates was comparatively tracked through specific oxygen uptake rate measurements from which the respirometric inhibition of biological activated sludge imparted by raw and ozonated reactive dye wastewater with respect to synthetic domestic wastewater was determined. It could be demonstrated that preliminary ozonation of reactive azo dyes increases their biological compatibility more significantly than formazan copper complex, copper complex azo and phythalocyanine dyes as a consequence of heavy metal release associated with the cleavage of associated chromophoric groupings right at the initial stages of pre-ozonation.

Effect of ozone injection location on filter performance in direct filtration

Two identical pilot scale sand filters were operated in parallel to study the effects of preozonation in direct filtration. No coagulants were used. The influent of one filter was ozonated, whereas the influent to the second filter was aerated. Significantly improved reduction in turbidity, particle count, and iron was observed with the filter receiving preozonated water. The head loss development rate was increased as a result of using ozone. In a second set of experiments, the effects of ozone injection point on filter performance were investigated. Two identical filters both receiving preozonated water were operated. With one of the filters, the raw water was ozonated immediately before it entered the filter. The entrance of the preozonated water to the other filter was delayed by using a detention tank between the ozone contact chamber and the filter. In addition to effluent turbidity and particle count values, zeta potentials of the waters entering the two filters were measured. Head loss development at several locations within each filter bed was also observed and recorded. Slightly better effluent quality (turbidity and particle count) was observed with the filter receiving preozonated water without delay. It was observed that the zeta potential of the prezonated water became more negative with increasing delay time.

The effect of pre-ozonation on the H2O2/UV-C treatment of raw and biologically pre-treated textile industry wastewater

Advanced chemical oxidation of raw and biologically pretreated wastewater by ozonation, H2O2/UV-C treatment and the successive combination of ozonation and H2O2/UV-C oxidation was investigated. For the raw textile wastewater, the application of successive O3 + H2O2/UV-C oxidation enhanced the COD and TOC removal efficiency of the H2O2 (50 mM)/UV-C process by a factor of 13 and 4, respectively. In case of the biotreated textile wastewater, the preliminary ozonation step increased COD removal of the H2O2 (10 mM)/UV-C treatment system from 15% to 62%, and TOC removal from 0% to 34%, but did not appear to be more effective than applying a single ozonation process in terms of TOC abatement rates. Enhancement of the biodegradability was more pronounced for the biologically pre-treated wastewater with a two fold average increase in the BOD5/COD ratio for the studied chemical oxidation systems.

Ozonation In Direct Filtration

The effects of pre-ozonation on the effluent quality and the head losses through a deep filter were investigated using two identical deep bed filters receiving the same raw water. One of the influents to the filters was pre-ozonated and the other was aerated using identical contact chambers and diffusers. It was observed that the pre-ozonated filter resulted in significantly better effluent quality. It was found that the delay time after the pre-ozonation process has an important effect in direct filtration. The shorter the delay time, the less is the head loss and the better is the effluent quality. Indices that calculate Specific Energy (cm of head required per gram of solids captured) in deep bed filters were developed. The Filterability Index given in the literature and the Specific Energy values were used to compare the performance of the two identical filters receiving the same raw water. It was shown that the pre-ozonated water required on average 1.1 times more specific energy compared to the same aerated water and the experiments with short ozone delay times had on average 4.9 times less specific energy compared to the long delay experiments.

Effect of Ozonation and UV Irradiation with Direct Filtration on Disinfection and Disinfection by-Product Precursors in Drinking Water Treatment

Pilot plant studies were conducted to evaluate the effect of pre-ozonation and ultraviolet irradiation on disinfection, disinfection by-product precursors and water quality in a direct filtration water treatment system. Disinfection parameters including total coliforms, faecal coliforms and heterotrophic plate count were investigated. Total organic carbon (TOC), trihalomethanes (THMs), total organic halides (TOX), filtered water turbidity and colour were also evaluated. It was found that advanced pre-oxidation processes (ozonation and UV irradiation) significantly increase the level of disinfection of raw water. Removal of total trihalomethanes and total organic halides precursors improved with ozonation and UV irradiation, compared to no oxidation treatment in direct filtration and/or in conventional water treatment. All coliforms (total and faecal) were completely destroyed by ozonation alone, and also with ozonation in conjunction with UV irradiation. However, the heterotrophic plate count was not significantly reduced at an ozone residual concentration of 0.1 mg l−1. This suggests that disinfection efficiency is strongly influenced by competition reactions of organic and inorganic compounds with ozone. Precursors of total trihalomethanes and total organic halides were reduced by 90% and 98%, respectively, with advanced pre-oxidation processes. Water quality parameters were improved by the pre-ozonation and UV irradiation treatment system.

Membrane filtration of surface water in the presence of ozone

The preliminary study investigated the effect of pre-ozonation of synthetic raw water (bentonite and humic acid) on membrane fouling. The results showed that humic acid, not bentonite, was the dominant factor in membrane fouling. When the synthetic raw water was pre-treated using ozone and activated carbon, stable operation was possible at twice the flux of membrane filtration without pre-treatment. Thus, ozone and activated carbon reduced the concentration of organic matter (humic acid), leading to an increase in flux. Secondly, an MF membrane filtration device with ozone tolerance was attached downstream of the ozone reactor so that residual ozone could reach the membrane surface. When water was treated with MF membrane filtration in the presence of ozone, the flux was stable at 4 m/d. The membrane filtration resistance increased when ozone was not injected, and decreased when it was injected. This phenomenon was repeatable. In the presence of ozone, organic matter that could accelerate fouling as decomposed and converted to less fouled materials, resulting in a suppression of fouling as well as facilitating removal of the fouling layer during back washing.

Effects of pre-ozonation and selected advanced water treatment processes on Mount Seymour impoundment water

In May 1999, a project using a dissolved air flotation (DAF)/ozone/filtration pilot plant was started to study the effects of pre-ozonation on the flocculation of particles and removal of organic matter in an advanced treatment process. Results indicate that small doses of ozone pre-ozonation slightly improve the flocculation of particles and their subsequent removal in the DAF unit when used in conjunction with alum or PACl. However, it was found that high ozone doses impeded flocculation. More significant is ozone's benefit for the removal of UV-absorbing organic matter. The study also found that DAF is very effective at removing turbidity causing particles and colour from the water, thereby improving filter performance.

Effect of Preozonation on Flux and Water Quality in Ozonation-Ultrafiltration Hybrid System for Water Treatment

The effect of ozonation on membrane flux and water quality was investigated in an ozonation ultrafiltration (UF) hybrid system. Crossflow UF was performed in total recycle mode to study the effect of ozonation on membrane fouling and disinfection by-product formation potentials of organics. Total organic carbon (TOC), UV absorbance at 254 ran (UV254) and trihalomethane formation potential (THMFP) were measured as water quality parameters. The effect of ozonation on membrane flux was found to be largely dependent on raw water quality as well as ozone dose. In case of upstream water (A), preozonation achieved significant flux enhancement regardless of ozone dose. Whereas, for the downstream water (B), the steady state flux was increased or decreased depending on ozone dose. The analysis based on the resistance-in-series model provided the mechanistic interpretation on the membrane flux variation. Ozonation in an ozone-ultrafiltration system always brought about a decrease in cake resistance (Rc) and an increase in fouling resistance (Rf). Based on the measurement of particle size distribution and zeta potential, the reduction in cake resistance through ozonation was attributed to an increase in particle size due to “ozone-induced particle destabilization”. However, the increase in the fouling resistance seems to be caused partly by the microbial characteristics of raw water. Although there was little effect on TOC, ozone-UF treatment could get much higher removal of UV 254, THMFP (lday) and THMPF/TOC ratio than UF treatment alone.

Preozonation effects on coagulation

Depending on the type of coagulant used, preozonation can help or hinder the removal of organic matter.The effects of preozonation on interactions among coagulants, particles, and natural organic matter were examined at bench scale through a series of jar tests using different organic matter, pH values, and coagulants. When alum was used as a coagulant, preozonation hindered turbidity and dissolved organic matter (DOM) removal at the conditions tested. When cationic polymers were used as the coagulant, however, preozonation led to small but statistically significant increases in the removal of both turbidity and DOM. When polyaluminum chloride was used as the coagulant for several natural waters, preozonation aided turbidity and DOM removal in one instance and hindered removal of particles and organic materials in another instance. The authors hypothesize that preozonation reduces the surface charge of particulates, leading to better coagulation by charge neutralization.

Sodium Dodecylbenzenesulfonate Removal from Water and Wastewater. 2. Kinetics of the Integrated Ozone-Activated Sludge System

A batch-activated sludge process (AS) has been applied to eliminate sodium dodecylbenzenesulfonate (NaDBS), a linear alkylbenzenesulfonate (LAS) compound, from synthetic and real domestic wastewater. The kinetics of surfactant biodegradation was best described by first-order kinetics with rate constants of 1.28 and 1.15 L·(g VSS·day)-1 for synthetic and real domestic wastewater, respectively. The effect of preozonation on the overall surfactant and COD removal rates was also studied. The results indicated that treatment by combined ozone−AS leads to negligible foam ability and low residual surfactant concentration and COD in the treated effluent. Acclimation of a mixed culture to ozonated products was beneficial to highly improve biodegradation rates after preozonation. Thus, when applying ozone at a dose of 100 mg·L-1, the first-order surfactant biodegradation rate constant increased up to 1.79 and 3.09 L·(g VSS·day)-1 for synthetic and real wastewater, respectively. Continuous experiments of ozonation f...

Effect of Preozonation on the Formation of Chlorinated Disinfection By-products for River Ruhr

Effect of Preozonation on the Formation of Chlorinated Disinfection By-products for River Ruhr

Effect of Preozonation on the Formation of Chlorinated Disinfection By-products for River Ruhr

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The effect of preozonation on microorganism and particle removal

The new European regulation on treated water focuses on oxidation by-products and consequently the use of ozone for parasites and virus inactivation should be limited. To achieve the necessary removal of parasites by a multi-barrier water treatment plant, physical removal needs to achieve consistently high levels of particle and microorganism removal. TheNeuilly-sur-Marne treatment plant treats raw water of particularly poor bacteriological quality. In order to improve the filtered water quality, preozonationhas been tested in a pilot scale study. Results obtained have confirmed that, with this sort of raw water, preozonation directly on the raw water or on the settled water can provide a significant improvement in filtered water. This is true for both particles and coliforms. It appears that an ozone dose of 0.5 g/m3 is enough to achieve a constant level of efficiency.

Effects of Pre-Ozonation of High Humic Content Waters on Direct Filtration in a Pilot Plant

Direct filtration and the effects of pre-ozonation on direct filtration performance were evaluated and compared with conventional water treatment performance in a pilot plant study. Performance measures including coagulant demand, turbidity, colour, total organic carbon, head loss development, filter run time, back wash water consumption, filtration solids volume and iron and manganese were examined for a water source with low turbidity and high organic matter content. The optimal coagulant dosage established for in-line direct filtration was much lower than that required for conventional treatment of the same raw water. Direct filtration preceded by ozonation achieved similar, or substantially higher, turbidity removal efficiencies with a significantly lower alum coagulant dosage. Pre-ozonation was effective in lowering turbidity, colour, head loss development and iron and manganese levels but was not significant in removing TOC. Pre-ozonation increased filter run time by about 7% when compared with the case of no ozonation treatment. The back wash consumption was 5% of total water produced and solids volume produced by coagulation and direct filtration alone was 8% of the back wash water used. There were no significant differences for the latter two parameters by pre-ozonation treatment.