Ozone/AOP
In the field of water and waste water treatment, an efficient technology is required to eliminate endocrine disrupters, pharmaceutical and personal care products (PPCPs) in order to avoid adverse effects in receiving waters.
These organic compounds represent persistent substances that are hardly biodegradable. Endocrine disrupters are particularly a matter of concern. This group include nonylphenols, PCBs or phthalic esters for instance. These molecules are called endocrine disrupters due to their impact on the hormonal system. Among these compounds, some of them are now recognized for impacting the human health, as they are carcinogenic, mutagenic and reprotoxic (CMR) substances. The elimination of endocrine disrupters from water effluents is therefore a huge public health issue.
As endocrine disrupters are hardly or even not degraded within conventional sewage plants, they remain at the surface water, enter ground water and finally, potable water. Nevertheless, these substances can be reduced by using an oxidation process such as Ozone/AOP (Advanced Oxidation Process) which uses mainly ozonation but may also combine UV and / or H2O2. Ozone is a powerful multifunctional oxidant that can be used for disinfection or colour-reduction for instance. The oxidized by-products that are obtained through this treatment are better biodegradable: hydroxyl radicals are generated and react very quickly with nearly all organic compounds.
In order to develop analytical methods and determine the treatment effect of an AOP, pilot tests were conducted at the municipal sewage treatment plant in Braunschweig (Germany). In particular, the Ozone/UV technique was tested within this treatment plant. The device included an ozone generator with a capacity of 100 g/h and a UV reactor.
More than 50 compounds, which are frequently present in municipal wastewater, were analysed during the pilot testing period. The amount of one single substance varies from 0,5 µg/L to 10 µg/L in the water effluent.
The results showed that ozonation was a very efficient process treatment, considering that for most of the compounds, the oxidation efficiency was higher than 80%. However, it was shown that in real waste waters, when carrying out a cost/benefit analysis, the best available technology consists in using Ozone. An additional enhancement by UV or H2O2 is not necessary.
