Modification of the standard Neutral Ozone Decomposition Model

ABSTRACT
The modified Staehelin, Buhler, and Hoigné model for aqueous ozone decomposition was tested over a wide range of hydroxyl radical scavenger concentrations at a pH of 7.1-7.2. Results from these experiments showed that the modified model appeared to overpredict the residual hydroxyl radical probe compound, tetrachloroethylene, concentration.

The modified Staehelin, Buhler, and Hoigné model was recalibrated and two rate constants, the rate constant of the initiation reaction of ozone  decomposition of hydroxide ion and the rate constant of the promotion reaction of ozone decomposition by hydroxyl radical, were reestimated. The new estimates of these rate constants are 1.8x102M-1S-1 (initiation reaction) and 2x108 M-1S-1 (promotion reaction). The recalibrated -modified model was tested and validated by conducting experiments at different pH values and hydroxyl radical scavenger concentrations. Also, the effect of phosphate buffer as a hydroxyl radical scavenger was investigated at phosphate buffer concentrations of 10mM and1mM. Boijayanta K. Bezbarua1 and David A. Reckhow2 1Luit Infotech Pvt. Ltd., Chennai, India 2Department of Civil and Environmental Engineering, University of Massachusetts, Amherst, Massachusetts, USA

Seawater Ozonation of Bacillus Subtilis Spores: Implications for the Use of Ozone in Ballast Water Treatment

ABSTRACT
The potential of ozone for disinfection of ship's ballast water was investigated using Bacillus Subtilis spores as an indicator. The effects of pH, presence of iron, and bacterial strain on disinfection efficacy in seawater, under simulated ballast conditions, were investigated. Ozone dosages of 9 mg/L (pH7) and 14 mg/L (pH 8.2) and 24 h contact achieved a 4-log inactivation with the various oxidant residuals formed. Iron surface at a ratio to water of 9 m2/m3 impaired the oxidant residuals and the disinfection of spores. Different strains of B. Subtilis resulted in different CT values. Ozone does not seem to be a good choice for the control of spore-forming organisms in ballast water, but may  be suitable for the control of other species.

D. Oemcke1 and J. Hans van Leeuwen2 1Provisor, Hartley Grove Urrbrae, South Australia 2Department of Civil, Construction and Environmental Engineering, Iowa State University, Ames, Iowa, USA

A two-Phase Computational Fluid Dynamics Model for Ozone Tank Design and Troubleshooting in Water Treatment

ABSTRACT
A computational fluid dynamics (CFD) tool was employed to design and study ozone contactors. The emphasis was to achieve the desired flow distribution. The Eulerian-Eulerian multiphase model was used with the standard ?-? turbulent model. The water surface was slip wall boundary and was specified as a sink to remove ozone bubbles. For a single-column contactor with side entry , the flow pattern was found to be crucially dependent on both the direction and magnitude of the entry velocity from the inlet pipe. It was difficult to achieve uniform gas concentration over the contactor volume. In a multicompartment contactor, the counter current flow resulted in a mixed flow condition and the mixing increased with a higher gas rate. For the counter current flow, water was accelerated by the gas and the plug flow pattern was achieved. The flow distribution in each compartment can be significantly different even though the overall residence time distribution curves are similar.

C.T.Ta and J. Hague
Kempton AWTW, Thames Water, Research and Technology, Hanworth, Middlesex,
United Kingdom

Application of an Experimental Design to Modeling of Ozone Bleaching Stage in TCF Processes

ABSTRACT
An oxygen delignified eucalyptus Kraft pulp was bleached in a totally chlorine-free (TCF) sequence using an ozone stage (Z) followed by a hydrogen peroxide stage (P). Ozone treatments were carried out at a laboratory scale with new automated equipment. The Z stage was modelled using a four-variable sequential statistical plan over the following ranges: 10:20 g o.d.p. mass pulp, 20-50 mg/L ozone inlet concentration, 80-220 LN h ozone flow, and o.25-0.65% o.d.p. ozone dose. The influence of these variables on several pulp properties after the Z and P stages of the XZP sequence was examined. The models defined from the results obtained predicted, in the Z stage, variations in ISO brightness, viscosity, and kappa number of 74.6-85.6%, 496-876 mL/g, and 0.44-2.27, respectively. It is possible to obtain bleached eucalyptus pulp of brightness over 89% ISO and viscosities over 800 mL/g. The variable most strongly influencing the pulp properties was found to be the ozone dose.

A.L. Torres, M.B. Roncero, J.F. Colom, J.A. Martinez, and T. Vidal
Department of Textile and Paper Engineering, ETSEI Terrassa, Technical University of Catalonia, Terrassa, Spain

Ozonation of Polycyclic Aromatic Hydrocarbons in Water Solution

ABSTRACT
The degradation of three polycyclic aromatic hydrocarbons (PAHs): benzo[a]pyrene (BAP), chrysene (CHR), and fluorine (FLU) in aqueous solution using ozone was investigated. The influence of pH of the reaction mixture, ozone concentration, and the presence of a radical scavenger on the reaction rate was determined. The highest rate of PAHs disappearance was achieved in acidic solutions. The radical scavenger, tert-butanol, effectively inhibited the rate of PAHs destruction. The rate constants of direct reaction of PAHs with ozone were calculated and they were equal to (3.32±0.21)x 104 and 44.8±1.1 M-1S-1 for BAP, CHR, and FLU, respectively. The contributions of direct ozonolysis, and radical reaction to PAHs oxidation in ozonation processes, were evaluated.

Jacek S. Miller and Dorota Olejnik
Faculty of Process and Environmental Engineering, Technical University of ?òdz, ?òdz, Poland

Influence of DOC on the Inactivation Effieciency of Ozonation Assessed with Clostridium perfringens and a Lab-Scale Continuous Flow System

ABSTRACT
Routine quality monitoring for fecal indicators after ozonation at the river-lake waterworks Weesperkarspel of Amsterdam. Water Supply (AWS) show large variation in inactivation. The influence of the high DOC in the water on the inactivation efficiency was investigated. Results showed a higher inactivaton of Clostridium perfringens in the AWS water than in a water with low DOC at the same CT conditions. The contribution of the gas feed chamber to the overall inactivation of C. perfringens was high in the AWS water and was reduced after DOC reduction with GAC. This result may alter the current CT concept of the process. Further research will be focused on the ozone dosage strategy and control related to the required CT for inactivation and the production of by-products.

W.A.M.  Hijnen, E. Baars,T.G.J. Bosklopper, A.J. van der Veer, R.T. Meijers, and G.J. Medema
Kiwa Water Research Ltd., Nieuwegein, the Netherlands Amsterdam Water Supply, Amsterdam
The Netherlands Water Company Europoort, Rotterdam, the Netherland, Aquavisie, Hengelo, the Netherlands

Research Note: Effects of Ozonated Water Spray Droplet Size and Distance on the Dissolved Ozone Concentration at the Spray Target

ABSTRACT
Dissolved ozone concentration (DOC) of ozonated water (OW) sprayed from four different distances using three different droplet sizes  (expressed in terms of Sauter mean diameter, small, medium, large) was measured at the spray target to obtain fundamental data for improving disease control efficacy when spraying OW onto plants. DOC in the OW at the spray target decreased with decreasing droplet size. DOC was also greatly reduced at the typical spray distances of 0.50 to 0.75m  to less than one-seventh of the initial DOC (2.2 mg/L-1) in the sprayer reservoir, and DOC one-third  lower than the initial DOC was observed even at the shortest spray distance of 0.05m for all three nozzle sizes used. Based on the results of these experiments, disease control efficacy by spraying OW can  be improved by minimizing the spray distance and using a nozzle that produces a larger spray droplet size, within the range such that adhesion efficiency of OW to the leaf surface is not greatly reduced.

Kazuhiro Fujiwara and Takuya Fuji
Graduate School of Agricultural and Life Sciences, the University of Tokyo, Bunkyo, Tokyo, Japan

Research Note: Inactivation Efficiency of Ozonated water for Fusarium oxysporum Conidia under Hydroponic Greenhouse Conditions

ABSTRACT
Ozonated water was used for inactivation of Fusarium oxysporum conidia in sterilized water and inorganic soil less nutrient medium at different treatment temperatures. F. oxysporum conidia were effectively inactivated in both water and nutrient media and the inactivation curves were almost same at 15°C, 25°C and 30°C. Approximate 4-log orders of F. oxysporum conidia were killed when the ozonated water with initial ozone concentration of 1.0 ppm had been used. The surviving curves, however, were characterized by a tailing-off effect, and the effect was related to the residual ozone concentration in the ozone treated suspensions.

Norijuki Igura, Masatoshi Fuji, Mitsuya Shimoda, and Isao Hayakawa
Laboratory of Food Process Engineering, Department of Bioscience and Biotechnology, Faculty of Agriculture, Kyushu University, Fukuoka City, Fukuoka, Japan

BIOLOGICAL SLUDGE REDUCTION WITH OZONE

The solution of the problems linked to the disposal of the sludge coming from purification plants is one of the main themes that the water treatment branch will have to solve in the next few years.

Because of the expansion of purification plants, due both to the new development areas and to the stricter and stricter imposed limits, we have to be prepared to a dramatic increasing of produced sludge quantity.

We also have to add the more and more pressing social request not to dispose of the sludge in agriculture and consequently the demand to reduce the produced sludge quantity drastically.

The European and Italian guidelines are more and more demanding:
" European Norm: 86/278 regarding the environment protection
" Italian Receipt: DL 99/92; Ronchi decree
" "Sludge" directive: directed to increase the sludge recycling, provided that it has a fertilizer effect and that it is harmless
" DM 367/2003 : from 2008 on industrial waste sludge, also mixed, cannot be used in agriculture (attachment B, point h)

The cost of biological sludge treatment, that today already absorbs about 60% of the total exercise costs of an activated sludge plant, is going to grow dramatically!

At the moment, there are two ways to reduce the produced sludge in a biological process:
- increasing the pre-treatment (by reducing the organic charge and consequently the sludge quantity that will form)
- thickening as much as possible; with great increasing of plant costs and of chemical reactants consumption

The new process that allows to avoid cost increase and environmental damages is

OXYSLUDGE

Oxysludge is the name chosen by our Firm to characterize the process used for the destruction of activated sludge more easily.
It consists of a biological sludge oxidation made with ozone  that, through its action permits sludge to be reduced to one fifth and more of its starting amount.
The system is made up of a contact reactor in which ozone and   sludge coming from  sedimentation, from biological oxidation, from aerobic or anaerobic digestion react for a fixed time.

Ozone Action:
" damages the cellular membrane of stronger micro organisms that use part of the energy derived from the consumption of nourishing elements, to recover the cell rather than use it for reproduction.
" causes a wear or a complete break of the membrane of the weaker micro organisms
" favours the survival of more developed micro organisms (protozoa, metazoans,…) which use damaged micro organisms for their metabolism.

Picture 1  Different methods to  insert destruction with ozone in a biological active sludge plant (Paul, 2003)

Consequent advantages are:
" reduction of  disposal costs
" reduction of sludge treatment costs for equipment and chemical reactants
" increased sedimentability and elimination of bulking problem
" synergy with purifying processes and/or tertiary refining treatments with ozone (decolouration, surfactant elimination,…)

Concretely this process allows:
"  sludge reduction  50 - 80     %
"  with an ozone quantity of 0,06 -0,08     KgO3/KgSS100%

As to produce 1 Kg of ozone at current prices of electrical energy (0,092 €/kWh) and oxygen (0,103 €/kg) costs 1,8 €/kg O3, it derives that the cost to remove 1 kg of sludge at 100% si SS is equal to  0,108 - 0,144 €/kg.
The medium European price to dispose 1 tonne of sludge is of 200 €; in Italy it is certainly more changeable and conditioned (not chemically) from local situations, but it is clear that this kind of system is proposed to technicians, local authorities and managers because it:
" reduces disposal costs ( 40 - 50%)
" reduces reactants costs (lime and ferric chloride from 20 to 40%)
" reduces the costs of filtration, incineration
" avoids the manipulation and transport of  charges  with bad odours and dangers
" ensures the effective resolution of problem avoiding the formation of sludge
" grants that it is not used for "improper" applications