Micro pollutants are minerals or organic substances whose toxic, persistent and bio-accumulative properties may have a negative effect on the environment and organisms. Since these contaminants are bio-active, they are not totally biodegradable and hence cannot be removed using traditional water treatment technologies.
The steady release of micro pollutants containing waste water effluent poses long-term health risks since such contaminants are bio-accumulating and form new mixtures in the water. However, the exact outcomes of this are not fully known.
The presence of micro pollutants in the water cycle also poses a risk to the ecosystem. This has given way to large-scale analyses over a long period of time to investigate the impact of these contaminants.
However, the outcome of these studies does not bode well. The current generation of waste water treatment plants are not capable of removing these pollutants; however, a number of solutions are now available.
Since micro pollutants cannot be completely removed by standard water treatment methods, their bio-accumulation in waters presents a major concern. Some examples of micro pollutants sources are as follows:
- Pharmaceutical and personal care products (PPCPs): Pharmaceuticals (prescriptions, veterinary drugs, OTC-drugs); personal care products (cosmetics, fragrances, sunscreens)
- Radioactive and/or biologically harmful metals (lead, mercury, arsenic)
- Endocrine disrupters (EDCs)
At present, there are 100,000 compounds that are commercially registered in Europe, and residue from the most of these will ultimately end up in the water cycle. Many are aware of the ecological impact of EDCs, which can interfere with the endocrine system of animals and humans.
Research carried out on different fish species has shown the negative impact of EDCs on the reproductive system, for instance feminization of male fish, and behavioral changes that may eventually alter the natural evolution of these species.
Pathways to the Water
Surface run-off from agricultural areas or cities and waste water treatment plants are largely responsible for releasing micro pollutants into the water cycle. Human consumption accounts for 70% of the pharmaceutical residue found in waste water and livestock farming accounts for 20%.
Available Water Treatment Technologies
Traditional biological and mechanical water treatment techniques are not adequate for reducing micro pollutants. Two technologies are available which have been shown to work. Extensive research carried out in Sweden, Switzerland, and Germany showed that the most feasible solutions are activated carbon and ozone. According to these studies, ozone is the most eco-friendly and low-cost solution.
Ozone for Reduction of Micro Pollutants
Ozone is known for its high oxidation potential, which makes it highly efficient. It is a selective oxidant and mainly attacks double bonds and other electron-rich structures in molecules. Hence, it can effectively break down micro pollutants, such as pharmaceuticals.
However, the effective reduction of micro pollutants depends on the ozone dose, design of the ozone system, the dissolution system and so on. It also depends on separate process conditions at the water treatment plant where the ozone solution is deployed.
Pilot Scale Installations for Reduction of Pharmaceutical Residue
In 2014, Primozone, specializing in complete ozone water treatment solutions, constructed a mobile pilot scale ozone system that was particularly designed for reducing pharmaceutical residue.
This mobile ozone solution has been deployed at over 10 different waste water treatment facilities in the south of Sweden. The goal of such installations was to establish the concept on current waste water treatment plants and also to test and validate the design of the system on different water flows and different process and environmental conditions.
Individual water treatment plants stand to benefit from results, which are specific for their process technology, treatment method, plant size, and population structure.
Along with the waste water treatment plant, it was also decided where the ozone system can be implemented in the process. The pilot plant can be installed quickly, taking just a few hours and once the system has been operating for a few days, samples can be taken for testing.
The samples are collected prior to pre-filtration, after pre-filtration and subsequent to ozone treatment. In case an additional sand filter has been utilized, samples would also be collected after that.
The outcomes of these pilot installations indicated that with a dose of 5g O3/m3 up to 95% of reduction can be realized. These pilot installations also showed that the design of the ozone system plays a major role.
In addition, the cost of using ozone was relatively low, which was in effect much lower than that of other methods. Figure 1 shows the layout of Primozone® ozone system for reducing pharmaceutical residue. This complete system is mobile and easily accommodates in a 20’ container.
Figure 1. Design of Primozone® ozone solution for reduction of pharmaceutical residue
Results of Primozone Pilot Study
The results rely on many parameters such as alkalinity, pH and dissolved organic compounds (DOC). Other parameters unique to an individual WWTP could also apply. An example of the results observed in the Primozone pilot study is given below:
Reduction of pharmaceutical residue with ozone:
- Dose - 5 g ozone/m3
- Result - 95% overall reduction
- Cost – About 0.015 Euro/m3
Disinfection is a bonus when treating waste water with ozone:
- Dose - 5g ozone/m3
- Result (reduction in %): E-coli bacteria - 99,8%, Coliform bacteria - 99,9%
- No additional cost
This information has been sourced, reviewed and adapted from materials provided by Primozone.
For more information on this source, please visit Primozone.