The applied process consisting of ozonization and activated carbon adsorption is well known and widely applied in Europe in particular for large cities.

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The applied process consisting of ozonization and activated carbon adsorption is well known and widely applied in Europe in particular for large cities. 

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In general, pilot system should have provision for measuring the ozone concentration and the gas flow rate. The system should also have the provisions for measuring the reactor ozone concentration in the off gas to be able to determine the transferred ozone doze. To simplify ozone measurements, gas manifold system can be constructed to split generator output flow into several streams, each with its own flowmeter. The feed and off gas will be monitored with ozone gas monitor.

Pilot plants could use commercially available gas phase ozone monitors that use UV absorption of ozone to measure the concentration in the gas stream. UV analysers are applied for ozone concentrations range 0-200 ppm.

The ozone residual measurements use spectrophotometry with indigo method or some other colorimetric technique. Indigo method is based on the decolorization of an aqueous indigotrisulfonate reagent by ozone observed at 600 nm.

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Thanks! In China, we use ozone in a similar way after secondary treatment. We have developed an electromagnetic device that can improve ozone transfer efficiency. We are looking for a good method to test the OTE or off-gas, as well as developing a model to simulate the process because it also affects the AOP efficiency. How do you usually test the OTE or off-gas in pilot tests? 

Many thanks, Merry Christmas! 

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Ozone could be applied in several positions on Municipal WWTP:

after physico-chemical or biological treatment (for disinfection and color removal),

in activated sludge treatment process through external loop

for aerobic stabilisation of excess biological sludge

The transfer rate will depend on

physical properties of gas/liquid,

difference in concentration on either side of interphase and the rate of chemical reaction consuming the ozone

mixing in the reactor

Several models could be used to simulate general ozone transfer in aqueous phase

However, it is always necessary to perform pilot tests and experiments, for various wastewater characteristics depending on position where the ozone will be used on WWTP. 

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It is important to emphasise that many installations are over 20 years old and still have older types of ozone generators. However, there are new technologies in ozone treatment, like IGS™ Technology, IGS™ (Intelligent Gap System), applied by Ozonia, Svez, France.  The IGS™ Technology actually tailors the plasma (corona discharge) to optimize ozone generation and minimize non-productive energy.

The manufacturer claim reduction of 30 % of energy consumption in comparison to conventional ozone generators.

The other European manufacturer producing cold plasma ozone generators is Primozone Sweeden, also with high energy saving capabilities.

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Ozone is the strongest oxidizers for many containments for water and groundwater treatment, but energy consumption is one of the major concerns. That's why it's hard to promote this technology in the US. I am surprised that there are over hundred applications in the EU. Does the GHG requirement enforce operators to cut energy consumptions, especially for ozone process in the EU? 

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There is much more application of Ozone + GAC in drinking water treatment.

The use of ozone in wastewater treatment is mainly for disinfection after biological treatment. For odour removal, colour removal (mainly for industrial wastewater). Application of ozone in activated sludge process is also present.

Ozone is applied for treatment of some industrial wastewater treatment plants.

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In general ozonization plants are typically followed by Granular activated Carbon (GAC) systems so almost all of them have this combination.The combination of ozonation and GAC is commonly referred to as the biological activated carbon (BAC) process, or biologically enhanced activated carbon process.

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