Adapting the low-cost pre-disinfection column PREDICO for simultaneous softening and disinfection of pore water.

In previous works, a low-cost predisinfection column that combined coagulation-flocculation and GAC filtration was proposed for combination with electrodisinfection in the successful treatment of highly faecal polluted surface water. In this work, this column is adapted for the treatment of pore water by transforming the coagulation chamber into a chemical reactor with lime and replacing the GAC of the filter with ion exchange resins. This adapted system can soften water, remove nitrate and condition water for very efficient electrochemical disinfection, where 4 logs and 3 logs in the removal of E. coli and P. aeruginosa, respectively, were reached using commercial electrochemical cells, i.e., CabECO ® or MIKROZON®. The availability and low cost of the technology are strong points for usage in poor areas of developing countries.

How to avoid the formation of hazardous chlorates and perchlorates during electro-disinfection with diamond anodes?

This work focuses on disinfection of water using electrolysis with diamond coatings avoiding or minimizing the formation of hazardous chlorates and perchlorates using a special type of commercial cells designed by CONDIAS (Itzehoe, Germany) in two different sizes: the CabECO and the MIKROZON cells. In these cells, the electrolyte that separates the anode and cathode is a proton exchange membrane. This helps to minimize the production of perchlorate and this behavior is enhanced in the smallest cell for which the very low contact times between the electrodes and the water allows to avoid the production of perchlorates when operating in a single-pass mode, which becomes a really remarkable point. In this paper, we report tests in which we demonstrate this outstanding performance and we also explain the differences observed in the two cells operating with the same water.

Testing the use of cells equipped with solid polymer electrolytes for electro-disinfection.

This work focuses on disinfection of water using electrolysis with boron doped diamond (BDD) coatings and faces this challenge by comparing the performance of two different cells manufactured by CONDIAS GmbH (Izehoe, Germany): CONDIACELL® ECWP and CabECO cells. They are both equipped with diamond electrodes, but the mechanical design is completely different, varying not only by geometry but also by the flow conditions. ECWP is a flow-through cell with perforated electrodes while the CabECO cell is a zero-gap cell with a proton exchange membrane as a solid polymer electrolyte (SPE) separating the anode and cathode. At 0.02 Ah dm-3 both cells attain around 3-5 logs pathogen removal, but design and sizing parameters give an advantage to the CabECO: it can minimize the production of chlorates and perchlorates when operating in a single-pass mode, which becomes a really remarkable point. In this paper, we report tests in which we demonstrate this outstanding performance and we also explain the differences observed in the two cells operating with the same water.

Electrochemical advanced oxidation process using DiaChem electrodes.

The electrochemical advanced oxidation process (EAOP) using boron doped diamond (DiaChem, registered trademark of Condias GmbH) has been studied for wastewater treatment and drinking water disinfection. DiaChem electrodes consist of preferentially metallic base materials coated with a conductive polycrystalline diamond film by hot-filament chemical vapour deposition. They exhibit high overpotential for water electrolysis as well as high chemical inertness and extended lifetime. In particular the high overpotential for water decomposition opens the widest known electrochemical window, allowing the energy efficient production of hydroxyl radicals directly from aqueous solutions. The hydroxyl radicals on the other hand are effectively used for the oxidation of pollutants. The EAOP using DiaChem electrodes thus facilitates the direct and, if necessary, complete decomposition of even hazardous or persistent pollutants in different wastewaters. Current efficiencies of more than 90%, also without the use of additives for hydroxyl radical generation, have been demonstrated. Additionally, for drinking water preparation diamond electrodes facilitate disinfection with and without the support of chlorine.