UV-Oxidation > UV Oxidation > FAQ on Enviolet UV technology

FAQ on Enviolet's UV Technology

UV-oxidation in dark medium: Enviolet makes it possible.

Isn’t UV normally sensible to deposits on the quartz tube?
Our enviolet quartz is constructed in a special way and is not prone to scaling. Most of the scaling during UV oxidation comes from a very poor reactor design and a lack of understanding the requirements during the chemical process of UV oxidation. Our process can even produce optimal results in solutions with high COD of up to 70 g/L.

Our solution is very dark – won't all of the UV be absorbed?
Indeed a solution without absorption is a problem. UV oxidation needs the interaction of light and material. Without UV absorption of the matrix no reaction would take place. In the case of a very strong absorption, we have designed our reactor appropriately in order to reach its maximum performance, others just struggle with the black tube and can only switch off the process. The picture above demonstrates the possibilities.

What is the difference between our UV Oxidation Technology and Ozonation?
Ozone is a process that often works well at low concentrations. At higher concentrations the low solubility of ozone makes the reactions quite long and leads to a bad performance. (By increasing the system pressure in order to achieve higher ozone solubility, respecting safety restrictions makes the ozone system quite expensive).
Ozone also causes higher costs due to safety requirements that have to be met and also due to the residual destruction of ozone in the off-gas.
Ozone processes are therefore mostly found in drinking water applications, as the target concentration there shows a good range in relation to the possible range of ozone concentration.

What is the difference between our UV Oxidation Technology and UV Ozonation?
We do not know any application where the combination of ozone/UV performs reliably on strong wastewaters. The ozone/UV process does not show a working range, but a working point only. This is due to the special ternary system with respect to the design:
- If the water gets more transparent than assumed, all ozone is processed to H2O2 and a very expensive variation of UV/H2O2 is applied.
- If the water gets darker the system changes to an ozone process only, as nearly no ozone is activated by UV.
In both cases the performance of the UV-Ozone-AOP is strongly reduced and the machine will not perform on spec.
Low contaminated water like drinking water or municipal wastewater are typical applications for Ozone processes.

Why does enviolet quote UV/H2O2 only?

We quote various AOP processes – UV/H2O2 is only one of several different ones. Usually during our feasibility study we identify the process which is the most suitable for that application and this is the process we will recommend.

What is the purpose of the hydrogen peroxide added in UV/H2O2 and the reaction with the UV radiation?
H2O2 can be an oxidant adding the necessary amount of oxygen to the solution; H2O2 can become a very strong oxidant in the presence of UV irradiation.

Does H2O2 remain in the effluent after the treatment?
If the process is applied in the right way there should not be any residual H2O2. Mostly it won't even be allowed for us to have residual H2O2.

Is there a specific grade for the H2O2 supply?
Technical quality or even waste H2O2 could be applied – only in synthetic applications we sometimes need specified H2O2.

What is the purpose of the additional catalyst used?
It varies from one application to the other if a catalyst will increase the efficiency – there are homogeneous catalysts like soluble sensitizers (egg. BR) and also heterogenic catalysts like TiO2, which can be used.

Is the additional catalyst used all the time, in all circumstances?
No – a catalyst will be used, when the catalyst will have advantageous effects on the process. These can be lower CAPEX, lower OPEX or a higher efficiency due to a selective process.

Does the additional catalyst remain in the effluent?
This depends on the application; often we recycle it, if this appears to be worthwhile. Also depending on the application we might eliminate it separately.

Does the customer always have to buy the catalyst from the process supplier?
In very specific applications: yes. Usually, we hand in the recipe after the acceptance of our unit.

We see your RECO system for the regulation of the UV radiation performance.
What is it? What is its purpose? Why is it a “plus” compared to other “UV” technology?

The RECO was an essential step for developing a reliable UV technology. The part of the hard UV-C light is sensible to voltage fluctuations. For a reliable process the UV performance has to be constant, as the UV oxidation process would otherwise not be constant. To warrant this, enviolet has developed and patented the RECO. The RECO permanently compares the current and the necessary process parameters of operation by continuous measurement of the physical conditions. These data are permanently compared with the lamps fingerprint on a chip-card supplied together with the UV lamp. In the case of differences outside the tolerance, the RECO adjusts the operating parameters.

This ensures that the performed power is equal to the nominal power.
The RECO is made up of three functional units:
* Measurement instrumentation (in reactor and power supply)
* Microprocessor with display
* Power supply panel (= modulator)

Do you use UV lamp “low pressure” or “medium pressure” with Hg ?
We use very different types of lamps. There are many more types than those mentioned above, and this is already a part which even in 5 pages could not be answered, why which lamp is best for the related application together with the individual set-up of the installation.

What is wavelength range mainly used in your technology?

This can be very different. The RECO-card decides which spectrum we apply and that can vary from project to project.

Is it more 185-190 nm or below 210-230 nm ?
See above; the lowest applications start at 172 nm and the longest we have end with 530 nm.

When you state the OPEX, is it including everything such as the H2O2, catalyst, electricity, UV lamps replacement, service, spare parts, etc… ?
Mostly we define OPEX as following: Chemicals, electricity and replacement lamps i.e. all consumables.

What is the maintenance required on one of your batch units?

All these things are stated in the manual and are strongly variable according to the application and the unit size. Normally it can be assumed that per batch we calculate 1 h of operation for the standard procedures, if the unit is started and the pumping off is activated manually. In special cases we even have an automatic start and discharging, but that requires special conditions; in this case the time per batch is even smaller.

Regarding the operation of a unit, do we need a full-time operator on the system, when the unit is running?
No – at many customers' sites the installations even run for a week without seeing an operator. There are alarm concepts using modern communication technology, and this prevents inspections outside of the required intervals.

After start-up, can the operator walk away?
YES, but see also above.

Is the system flexible enough so that if the effluent concentration in COD or other organics changes then the system can also handle it?

Does it require on-site intervention by your operators regularly?
NO, in the case of competent operator who is able to read and understand our documentation or followed the training during start-up or hand-over.

Why should I change from my working cyanide oxidation with peroxide/hypochlorite to a Cyanomat®?
Cyanomat® is fully automatic, safe and also able to destroy strong chelates like Ni-Cyanide or to crack T-CN (total cyanide).

Can I save chemicals by applying UV/H2O2 instead of H2O2 only?

Yes, there are two standard processes where the presence of UV irradiation strongly increases the degradation efficiency and at the same time reduces OPEX:
1.) UV/H2O2 instead of H2O2 for CN-destruction
2.) Photo-Fenton instead of a Fenton.
In detail, this means in the case of a Photo-Fenton:
-    a significantly lower amount of chemicals (than would be consumed in Fenton) is consumed
-    a stronger degradation (compared to Fenton) is obtained
-    after oxidation no precipitation/ filtration of iron sludge is required.
This reduces CAPEX (no flocculation/filtration of iron has to be installed) and OPEX (as less chemicals are required and no sludge disposal is needed).

Is there a specific advantage of the enviolet's photo-Fenton to the normal Fenton process?
In the case of a photo-Fenton we even need a lot less chemicals, have a stronger degradation and in the end there is no need for a precipitation and filtration of the iron. This reduces CAPEX and also OPEX for sludge disposal of chemicals put into the water before.

Is there a specific advantage of enviolet in comparison to the anodic oxidation process?
There are many processes where enviolet works many times better than anodic oxidation or so-called electro-oxidation: Cyanide detoxification, destruction of chelates, oxidation of COD, TOC-polishing, etc. We often have the impression that manufacturers of special electrodes for the chlorine-alkali-electrolysis are by force looking for new applications.

Does UV oxidation also work in concentrated solutions?

This depends on the definition of concentrated solutions and the case of application. Regarding the COD oxidation, we have successfully and commercially applied it to concentrations of up to more than 70.000 mg/L. As for selective elimination of APIs, we have successfully applied this in solutions with more than 250.000 mg/L COD. Cyanomat® treats cyanide concentrations up to 160.000 mg/L. We therefore conclude that we are able to treat concentrated solutions.